Patent Publication Number: US-2023160597-A1

Title: Ventilation apparatus and control method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application, under 35 U.S.C. § 111(a), of International Application No. PCT/KR2022/013024, filed on Aug. 31, 2022, which claims priority to Korean Patent Application No. 10-2021-0160695, filed on Nov. 19, 2021 in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     The disclosure relates to a ventilation apparatus for providing fresh air to an indoor space and a control method thereof. 
     2. Description of the Related Art 
     A ventilation apparatus is an apparatus for supplying outside air into an indoor space or exchanging room air with outside air to ventilate the indoor space. Existing ventilation apparatuses adjust room temperature and humidity only by performing total heat exchanging between outside air and room air through a total heat exchanger. Accordingly, outside air supplied to an indoor space is insufficiently dehumidified, and there are difficulties in maintaining comfort room temperature and humidity. 
     Recently, as the quality of room air, sanitation, and cleanliness are emphasized, ventilation apparatuses are increasing in use, and interest in internal contamination of the ventilation apparatuses is growing accordingly. One of components of a ventilation apparatus, which consumers can replace, is a total heat exchanger. In many cases, consumers cannot recognize a replacement of the total heat exchanger, which may result in contamination accumulation of the total heat exchanger and the propagation of bacteria and mold inside the total heat exchanger. 
     SUMMARY 
     Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the disclosure. 
     A ventilation apparatus according to an embodiment of the disclosure includes: a housing including a first inlet through which outside air is suctioned into the housing, a second inlet through which room air is suctioned into the housing, a first outlet through which the outside air is discharged to an indoor space, and a second outlet through which the room air is discharged to an outdoor space; an outside temperature sensor configured to measure a first temperature of the outside air; a room temperature sensor configured to measure a second temperature of the room air; a total heat exchanger to perform heat exchange between the outside air and the room air; a first blower connectable with the first outlet; a second blower connectable with the second outlet; and a processor configured to perform a drying operation to dry the total heat exchanger by operating at least one of the first blower while the first blower is connected to the first outlet and the second blower while the second blower is connected to the second outlet, based on a difference value between the first temperature and the second temperature. 
     The processor may be further configured to perform a first drying operation of operating both the first blower and the second blower, according to an identification that the difference value between the first temperature of the outside air and the second temperature of the room air is smaller than or equal to a preset threshold value; and perform a second drying operation of alternately operating the first blower and the second blower, according to an identification that the difference value between the first temperature of the outside air and the second temperature of the room air is greater than the preset threshold value. 
     The ventilation apparatus may further include a first damper formed between the first inlet and the first outlet, and the first damper to open or close a bypass flow path bypassing the total heat exchanger; a second damper to open or close a connecting flow path formed between the first inlet and the second inlet; and a third damper to open or close the first inlet, wherein the processor is further configured to control the first damper, the second damper, and the third damper based on the first drying operation or the second drying operation. 
     The processor may be configured to open the first damper and the third damper and close the second damper during the first drying operation. 
     The processor may be configured to close, during the second drying operation, the first damper and the third damper, and alternately close and open the second damper in correspondence to an alternate operation of the second blower and the first blower. 
     The processor may be configured to close the second damper and operate the second blower for a first predetermined time, and open the second damper and operate the first blower for a second predetermined time after the first predetermined time elapses. 
     The processor may be configured to set the first predetermined time to a longer time than the second predetermined time. 
     The ventilation apparatus may further include: a first duct connectable with the first outlet and provided outside the housing; a second duct connectable with the second inlet and provided outside the housing; a third duct connecting the first duct with the second duct, and forming a return flow path between the first outlet and the second inlet; and a fourth damper provided inside the third duct and opening or closing the return flow path. 
     The processor may be configured to open, during the second drying operation, the fourth damper in correspondence to an operation of the first blower and close the fourth damper in correspondence to a stop of the first blower. 
     The ventilation apparatus may further include a heat exchanger provided between the total heat exchanger and the first blower and configured to dehumidify air passed through the total heat exchanger. 
     The processor may be configured to perform the drying operation to dry the total heat exchanger based on a preset schedule. 
     The ventilation apparatus may further include an inputter configured to obtain a user input, wherein the processor may be configured to perform the drying operation to dry the total heat exchanger based on the user input including a drying command for the total heat exchanger. 
     A method for controlling a ventilation apparatus, the method comprising: measuring a first temperature of outside air which is suctioned into a housing of the ventilation apparatus through a first inlet; measuring a second temperature of room air which is suctioned into the housing of the ventilation apparatus through the second inlet; detecting a difference value between the first temperature of the outside air discharged into an indoor space through a first outlet and the second temperature of the room air discharged to an outdoor space through a second outlet; and performing a drying operation for a total heat exchanger, which performs heat exchange between the outside air and the room air, by operating at least one of a first blower while the first blower is connected with the first outlet and a second blower while the second blower is connected with the second outlet, based on the difference value between the first temperature and the second temperature. 
     The performing of the drying operation for the total heat exchanger may include: performing a first drying operation of operating both the first blower and the second blower, according to an identification that the difference value between the first temperature and the second temperature is smaller than or equal to a preset threshold value; and performing a second drying operation of alternately operating the first blower and the second blower, according to an identification that the difference value between the first temperature and the second temperature is greater than the preset threshold value. 
     The performing of the first drying operation may include: opening a first damper provided in a bypass flow path bypassing the total heat exchanger; closing a second damper provided in a connecting flow path between the first inlet and the second inlet; and opening a third damper provided in the first inlet. 
     The performing of the second drying operation may include: closing a first damper provided in a bypass flow path bypassing the total heat exchanger; closing a third damper provided in the first inlet; and alternately closing and opening a second damper provided in a connecting flow path between the first inlet and the second inlet, in correspondence to an alternate operation of the second blower and the first blower. 
     The performing of the second drying operation may include: closing the second damper and operating the second blower for a first time; and opening the second damper and operating the first blower for a second time after the first time elapses. 
     The first time may be set to a longer time than the second time. 
     The performing of the second drying operation may include: opening a fourth damper provided inside a duct forming a return flow path between the first outlet and the second inlet, in correspondence to an operation of the first blower; and closing the fourth damper in correspondence to a stop of the first blower. 
     The performing of the second drying operation may include dehumidifying air passed through the total heat exchanger by using a heat exchanger provided between the total heat exchanger and the first blower. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the present disclosure will become apparent from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG.  1    shows a ventilation system including a ventilation apparatus according to an embodiment of the disclosure; 
         FIG.  2    is a top view showing an inside of a ventilation apparatus according to an embodiment of the disclosure; 
         FIG.  3    shows a circulation of a refrigerant in a ventilation system according to an embodiment of the disclosure; 
         FIG.  4    is an exploded perspective view of a ventilation apparatus according to an embodiment of the disclosure; 
         FIG.  5    is a perspective view showing a bottom of a ventilation apparatus according to an embodiment of the disclosure after some components of the ventilation apparatus are removed; 
         FIG.  6    shows a first internal housing of the ventilation apparatus shown in  FIG.  4    after the first internal housing is turned up and down; 
         FIG.  7    shows a second internal housing of the ventilation apparatus shown in  FIG.  4    after the second internal housing is turned up and down; 
         FIG.  8    shows an integrated air conditioning system including a ventilation apparatus according to an embodiment of the disclosure; 
         FIG.  9    shows a circulation of a refrigerant in an integrated air conditioning system according to an embodiment of the disclosure; 
         FIG.  10    is a control block diagram showing configurations of a ventilation apparatus according to an embodiment of the disclosure; 
         FIG.  11    is a control block diagram showing configurations of an integrated controller according to an embodiment of the disclosure; 
         FIG.  12    shows a flow of air inside a ventilation apparatus according to an embodiment of the disclosure during a first drying operation of the ventilation apparatus; 
         FIG.  13    shows a flow of air through a first flow path inside a ventilation apparatus according to an embodiment of the disclosure during a second drying operation of the ventilation apparatus; 
         FIG.  14    shows a flow of air through a second flow path inside a ventilation apparatus according to an embodiment of the disclosure during a second drying operation of the ventilation apparatus; 
         FIG.  15    shows an embodiment of the disclosure, which is additionally applicable to the second drying operation described in  FIG.  14   ; 
         FIG.  16    is a flowchart illustrating a method for controlling a ventilation apparatus, according to an embodiment of the disclosure; and 
         FIG.  17    is a flowchart detailedly illustrating the method for controlling the ventilation apparatus, described in  FIG.  16   . 
     
    
    
     DETAILED DESCRIPTION 
     Configurations illustrated in the embodiments and the drawings described in the present specification are only the preferred embodiments of the present disclosure, and thus it is to be understood that various modified examples, which may replace the embodiments and the drawings described in the present specification, are possible when filing the present application. 
     Like reference numerals or symbols denoted in the drawings of the present specification represent members or components that perform the substantially same functions. In the drawings, for easy understanding, the shapes or sizes of components are more or less exaggeratedly shown. 
     Throughout this specification, it will be understood that when a certain part is referred to as being “connected” with another part, it can be directly or indirectly connected with the other part. When a part is indirectly connected with another part, it may be connected with the other part through a wireless communication network or via another part. 
     The terms used in the present specification are merely used to describe embodiments, and are not intended to limit and/or restrict the disclosure. An expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context. In the present specification, it is to be understood that the terms such as “including” or “having,” etc., are intended to indicate the existence of the features, numbers, steps, operations, components, parts, or combinations thereof disclosed in the specification, and are not intended to preclude the possibility that one or more other features, numbers, steps, operations, components, parts, or combinations thereof may exist or may be added. 
     Also, it will be understood that, although the terms including ordinal numbers, such as “first”, “second”, etc., may be used herein to describe various components, these components should not be limited by these terms. These terms are only used to distinguish one component from another. For example, a first component could be termed a second component, and, similarly, a second component could be termed a first component, without departing from the scope of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of associated listed items. 
     In addition, the terms “portion”, “device”, “block”, “member”, and “module” used herein refer to a unit for processing at least one function or operation. For example, the terms may mean at least one process that may be processed by at least one hardware such as field-programmable gate array (FPGA) or application specific integrated circuit (ASIC), or at least one software or processor stored in a memory. 
     Reference numerals used in operations are provided to identify the operations, without describing the order of the operations, and the operations can be executed in a different order from the stated order unless a specific order is definitely specified in the context. 
     Throughout the disclosure, the expression “at least one of a, b or c” indicates only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or variations thereof. 
     Therefore, it is an aspect of the disclosure to provide a ventilation apparatus capable of efficiently drying a total heat exchanger, and a control method thereof. 
     Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings. 
       FIG.  1    shows a ventilation system including a ventilation apparatus according to an embodiment of the disclosure.  FIG.  2    is a top view showing an inside of a ventilation apparatus according to an embodiment of the disclosure.  FIG.  3    shows a circulation of a refrigerant in a ventilation system according to an embodiment of the disclosure. 
     Referring to  FIGS.  1 ,  2 , and  3   , a ventilation system  1  may include a ventilation apparatus  100  that communicates with an indoor space and an outdoor space to exchange room air with outside air, and an outdoor unit  200  for circulating a refrigerant to be supplied to the ventilation apparatus  100 . 
     The outdoor unit  200  may include a compressor  210  and a condenser  220 . The compressor  210  may include an accumulator  212  and a compressor body  211 . The condenser  220  is also referred to as an ‘outdoor heat exchanger’. The compressor  210  may be connected with the condenser  220  through a refrigerant pipe  221 . The outdoor unit  200  may include a cooling fan  220   a  to adjust temperature of the condenser  220 . The cooling fan  220   a  may discharge air toward the condenser  220  to cool the condenser  220 . Because the condenser  220  is cooled by the cooling fan  220   a , temperature of a refrigerant passed through the condenser  220  may be lower than in a case in which the cooling fan  220   a  does not exist. 
     The outdoor unit  200  may correspond to an outdoor unit for an air conditioner known in the art, and therefore, one of ordinary skill in the art may easily change or add various components required to operate the outdoor unit  200 . As such, the ventilation system  1  may operate by using an existing outdoor unit  200 , and therefore, the ventilation apparatus  100  may be miniaturized and reduce production costs because the ventilation apparatus  100  includes no separate component such as a compressor. 
     The ventilation apparatus  100  may include a housing  101  forming an outer appearance. The housing  101  may be substantially in a shape of a box. The housing  101  may include an intake flow path  102  for sucking outside air in and guiding the outside air to an indoor space, and an exhaust flow path  103  for guiding room air to outside. The intake flow path  102  may be partitioned from the exhaust flow path  103  by a plurality of partition walls  108 . 
     The housing  101  may include a first intake room  104  including a first inlet  101   a  which communicates with an outdoor space and through which outside air is sucked to inside of the housing  101 , wherein the intake flow path  102  may be formed inside the first intake room  104 , and a second intake room  105  including a first outlet  101   b  which communicates with the indoor space and through which outside air sucked to the inside of the housing  101  is discharged to the indoor space, wherein the intake flow path  102  may be formed inside the second intake room  102 . The intake flow path  102  may connect the first inlet  101   a  with the first outlet  101   b.    
     The housing  101  may include a first exhaust room  106  including a second inlet  101   c  which communicates with the indoor space and through which room air is sucked to the inside of the housing  101 , wherein the exhaust flow path  103  may be formed inside the first exhaust room  106 , and a second exhaust room  107  including a second outlet  101   d  which communicates with the outdoor space and through which the room air sucked to the inside of the housing  101  is discharged to the outside, wherein the exhaust flow path  103  may be formed inside the second exhaust room  107 . The exhaust flow path  103  may connect the second inlet  101   c  with the second outlet  101   d.    
     The ventilation apparatus  100  may include an intake blower  109   a  positioned inside the second intake room  105 , generating blowing power required to suck outside air into the indoor space, and communicating with the first outlet  101   b . The ventilation apparatus  100  may include an exhaust blower  109   b  positioned inside the second exhaust room  107 , generating blowing power required to discharge room air to the outside, and communicating with the second outlet  101   d . The intake blower  109   a  is also referred to as a ‘first blower’, and the exhaust blower  109   b  is also referred to as a ‘second blower’. 
     The ventilation apparatus  100  may include a total heat exchanger  110  for heat-exchanging air flowing along the exhaust flow path  103  with air flowing along the intake flow path  102 . The total heat exchanger  110  may be made of a paper material coated with lithium chloride, and the total heat exchanger  110  is also referred to as a ‘total heat exchanging device’. The total heat exchanger  110  may be a plate type total heat exchanger or a rotary type total heat exchanger. The total heat exchanger  110  may be positioned at a location where the intake flow path  102  intersects with the exhaust flow path  103 . That is, the total heat exchanger  110  may be considered as being positioned on both the intake flow path  102  and the exhaust flow path  103 . 
     The total heat exchanger  110  may communicate the second intake room  105  with the second intake room  106 . The total heat exchanger  110  may communicate the first exhaust room  106  with the second exhaust room  107 . Outside air flowing through the intake flow path  102  may be heat-exchanged with room air flowing through the exhaust flow path  103  without being in contact with the room air inside the total heat exchanger  110 . 
     The ventilation apparatus  100  may include a filter  112  for collecting foreign materials included in outside air. The filter  112  may be adjacent to the total heat exchanger  110 . The total heat exchanger  110  may include an intake terminal  110   a , and the filter  112  may face the intake terminal  110   a  of the total heat exchanger  110 . 
     Preferably, the filter  112  may face the intake terminal  110   a  in such a way as to be in close contact with the intake terminal  110   a . Accordingly, foreign materials flowing in outside air entered the filter  112  through the first inlet  101   a  may be filtered by the filter  112 , and as a result, the total heat exchanger  110  may be prevented from being contaminated. 
     For example, the filter  112  may be a High Efficiency Particulate Air (HEPA) filter. The HEPA filter may be configured with glass fibers. The filter  112  may be a photocatalyst filter for inducing a chemical action of air by using photocatalyst. That is, the filter  112  may include photocatalyst, and collect various pathogens and bacteria existing in the air by inducing a chemical action by light energy of the photocatalyst. By catalyzing a chemical action, smell particles in the air may be decomposed, removed, or collected, although not limited thereto. However, the filter  112  may be one of various kinds of filters capable of collecting foreign materials. 
     An existing ventilation apparatus performs heat-exchange between outside air and room air by using a total heat exchanger installed therein, without being connected with an outdoor unit. The existing ventilation apparatus does not include a separate heat exchanger that is connected with the outdoor unit and receives a refrigerant from the outdoor unit. That is, the existing ventilation apparatus supplies outside air to an indoor space and exhausts room air to the outside without performing additional dehumidification. 
     However, the ventilation apparatus  100  may include heat exchangers  120  and  130  for adjusting humidity and temperature of air flowing through the intake flow path  102 . The heat exchangers  120  and  130  are also referred to as ‘dehumidification modules’. The heat exchangers  120  and  130  may remove moisture from air passing therethrough. Accordingly, dehumidified air may be supplied to the indoor space. 
     The heat exchangers  120  and  130  may be configured with a first heat exchanger  120  and a second heat exchanger  130 . The heat exchangers  120  and  130  may be provided on the intake flow path  102 . The heat exchangers  120  and  130  may be positioned inside the second intake room  105 . That is, the first heat exchanger  120  and the second heat exchanger  130  may be positioned more downstream of the intake flow path  102  than the total heat exchanger  110 . 
     The second heat exchanger  130  may be positioned more upstream of the intake flow path  102  than the first heat exchanger  120 . In other words, the first heat exchanger  120  may be positioned more downstream of the intake flow path  102  than the second heat exchanger  130 . Outside air sucked through the first inlet  101   a  may pass through the first intake room  104 , the total heat exchanger  110 , the second heat exchanger  130 , and the first heat exchanger  120  in this order, and then be discharged to the indoor space through the first outlet  101   b.    
     Air flowing along the intake flow path  102  from the first inlet  101   a  toward the first outlet  101   b  may be dehumidified by the second heat exchanger  130 . Air passed through the second heat exchanger  130  may be heated by the first heat exchanger  120 , or the air may be cooled and dehumidified. 
     The first heat exchanger  120  may be connected with the outdoor unit  200  by a first refrigerant pipe  121 . The first heat exchanger  120  may be connected with the condenser  220  of the outdoor unit  200  by the first refrigerant pipe  121 . The second heat exchanger  130  may be connected with the first heat exchanger  120  by a second refrigerant pipe  131 . The second heat exchanger  130  may be connected with the outdoor unit  200  by a third refrigerant pipe  132 . The second heat exchanger  130  may be connected with the accumulator  212  of the outdoor unit  200  by the third refrigerant pipe  132 . 
     The ventilation apparatus  100  may include a first expander  160  provided in the first refrigerant pipe  121 . The first expander  160  may selectively expand a refrigerant that is supplied to the first heat exchanger  120  via the first refrigerant pipe  121 . The refrigerant passed through the first expander  160  may be reduced in pressure. 
     The ventilation apparatus  100  may include a second expander  170  provided in the second refrigerant pipe  131 . The second expander  170  may selectively expand a refrigerant that is discharged from the first heat exchanger  120  to the second heat exchanger  130  via the second refrigerant pipe  131 . The refrigerant passed through the second expander  170  may be reduced in pressure. The first expander  160  and the second expander  170  may be installed inside the housing  101 . The second refrigerant pipe  131  may be installed inside the housing  101 . 
     The first expander  160  may expand a high-temperature, high-pressure refrigerant to a low-temperature, low-pressure refrigerant by a throttling action, and adjust a flow rate of a refrigerant that is supplied to the first heat exchanger  120 . The first expander  160  may reduce pressure of a refrigerant by a throttling action of a refrigerant by which a refrigerant passing through a narrow flow path is reduced in pressure without exchanging heat with the outside. For example, the first expander  160  may include an electronic expansion valve (EEV)  161 . The electronic expansion valve  161  may adjust an expansion degree and flow rate of a refrigerant by adjusting a degree of opening. In a case in which the electronic expansion valve  161  fully opens, a refrigerant may pass through the electronic expansion valve  161  without resistance, and may be not expanded. 
     The second expander  170  may expand a high-temperature, high-pressure refrigerant to a low-temperature, low-pressure refrigerant by a throttling action. For example, the second expander  170  may include a solenoid valve  171  and a capillary tub  172  connected in parallel with the solenoid valve  171 . Upon closing of the solenoid valve  171 , a refrigerant may move to the capillary tub  172  to be throttled and expanded, and upon opening of the solenoid valve  171 , a refrigerant may be not expanded by flowing through the solenoid valve  171  without resistance. To efficiently adjust the flow and expansion of the refrigerant, the solenoid valve  171  may be replaced with an electronic expansion valve (EEV), although not limited. 
     For example, both the first expander  160  and the second expander  170  may include an electronic expansion valve. The first expander  160  may include a solenoid valve and a capillary tube connected in parallel with the solenoid valve, and the second expander  170  may include an electronic expansion valve. Both the first expander  160  and the second expander  170  may include a solenoid valve and a capillary tube connected in parallel with the solenoid valve. The solenoid valve connected in parallel with the capillary tube may also be replaced with an electronic expansion valve. 
     The ventilation apparatus  100  may include an outside temperature sensor  141  for measuring first temperature (outside temperature) of outside air and a room temperature sensor  142  for measuring second temperature (room temperature) of room air. Also, the ventilation apparatus  100  may include a discharge temperature sensor  143  for measuring discharge temperature which is temperature of air discharged to the indoor space after passing through the heat exchangers  120  and  130 . The ventilation apparatus  100  may include a room humidity sensor  150  for measuring room temperature. The room humidity may be relative humidity. 
     The outside temperature sensor  141  may be provided on the intake flow path  102 . For example, the outside temperature sensor  141  may be positioned in the first intake room  104  between the first inlet  101   a  and the total heat exchanger  110 , although not limited thereto. The outside temperature sensor  141  may be positioned outside the housing  101 . The outside temperature sensor  141  is also referred to as a ‘first temperature sensor’. 
     The room temperature sensor  142  and the room humidity sensor  150  may be provided on the exhaust flow path  103 . The room temperature sensor  142  and the room humidity sensor  150  may be positioned inside the first exhaust room  106 . The room temperature sensor  142  and the room humidity sensor  150  may be positioned more upstream of the exhaust flow path  103  than the total heat exchanger  110 . The room temperature sensor  142  is also referred to as a ‘second temperature sensor’. 
     The room temperature sensor  142  may measure temperature of room air sucked through the second inlet  101   c , and the room humidity sensor  150  may measure humidity of the room air sucked through the second inlet  101   c , although not limited thereto. The room temperature sensor  142  and the room humidity sensor  150  may be positioned outside the housing  101 . 
     The discharge temperature sensor  143  may be provided on the intake flow path  102 . The discharge temperature sensor  143  may be positioned inside the second intake room  105 . The discharge temperature sensor  143  may be positioned more downstream of the intake flow path  102  than the total heat exchanger  110 , the first heat exchanger  120 , and the second heat exchanger  130 . The discharge temperature sensor  143  may measure temperature of air that is discharged to the indoor space through the first outlet  101   b , although not limited thereto. The discharge temperature sensor  143  may be positioned outside the housing  101 . The discharge temperature sensor  143  is also referred to as a ‘third temperature sensor’. 
     The ventilation apparatus  100  may include a first sterilizer  111  for sterilizing the first heat exchanger  120  and the second heat exchanger  130 . The first sterilizer  111  may be positioned between the first heat exchanger  120  and the second heat exchanger  130 . The first sterilizer  111  may sterilize the first heat exchanger  120  and the second heat exchanger  130  positioned at both sides, at the same time. The first sterilizer  111  may include an ultraviolet light source for irradiating ultraviolet light. For example, the first sterilizer  111  may include a UV-LED. 
     Also, the ventilation apparatus  100  may include a second sterilizer  113  for sterilizing room air sucked through the second inlet  101   c . The second sterilizer  113  may be positioned inside the first exhaust room  106 . For example, the second sterilizer  113  may include at least one of a heater, an infrared lamp, or a UV-LED. 
     The ventilation apparatus  100  for sucking outside air and ventilating an indoor space may provide operation modes of a first dehumidification mode, a second dehumidification mode, and a ventilation mode. The ventilation apparatus  100  may operate in one of the first dehumidification mode, the second dehumidification mode, and the ventilation mode based on room temperature and room humidity. A processor  192  of the ventilation apparatus  100  may control the ventilation apparatus  100  to operate in the first dehumidification mode, the second dehumidification mode, or the ventilation mode. The ventilation apparatus  100  may operate by switching to the first dehumidification mode, the second dehumidification mode, and the ventilation mode based on room temperature and room humidity. 
     The first dehumidification mode will be described below. In the first dehumidification mode, the first expander  160  may expand a refrigerant. The second expander  170  may expand or not expand a refrigerant. Preferably, the second expander  170  may not expand a refrigerant in the first dehumidification mode such that the refrigerant flows smoothly. For this, in the first dehumidification mode, the solenoid valve  171  of the second expander  170  may open. 
     A high-temperature, high-pressure refrigerant discharged from the compressor  211  may be condensed in the condenser  220  of the outdoor unit  200  and then enter the first expander  160 . The first expander  160  may expand the high-temperature, high-pressure refrigerant to a low-temperature, low-pressure state such that the refrigerant is evaporated in the first heat exchanger  120  and the second heat exchanger  130 . 
     The refrigerant expanded by the first expander  160  may enter the first heat exchanger  120 , and exchange heat with air passing through the first heat exchanger  120  to thereby be evaporated. The refrigerant discharged from the first heat exchanger  120  and then entered the second heat exchanger  130  may be again evaporated in the second heat exchanger  130 . The first heat exchanger  120  and the second heat exchanger  130  may remove moisture included in the air passing through the first heat exchanger  120  and the second heat exchanger  130  by condensing the air, and cool the air passing through the first heat exchanger  120  and the second heat exchanger  130 . That is, the ventilation apparatus  100  which operates in the first dehumidification mode may lower both temperature and humidity of outside air sucked to the indoor space. 
     Air supplied to the indoor space by the ventilation apparatus  100  operating in the first dehumidification mode may have temperature and humidity at which a user may feel comfortable. Because the ventilation apparatus  100  operating in the first dehumidification mode discharges cooled and dried air to the indoor space, the first dehumidification mode is also referred to as a ‘cooling dehumidification mode’. 
     The second dehumidification mode will be described below. In the second dehumidification mode, the first expander  160  may not expand a refrigerant. The second expander  170  may expand a refrigerant. A high-temperature, high-pressure refrigerant discharged from the compressor body  211  may be condensed by the condenser  220  of the outdoor unit  200  and then enter the first heat exchanger  120 . The first heat exchanger  120  may condense the received refrigerant. The high-temperature, high-pressure refrigerant discharged from the first heat exchanger  120  may be expanded by the second expander  170  to become a low-temperature, low-pressure refrigerant. The expanded refrigerant may enter the second heat exchanger  130 , and exchange heat with air passing through the second heat exchanger  130  to be evaporated. 
     In the second dehumidification mode, air flowing along the intake flow path  102  may pass through the second heat exchanger  130  and the first heat exchanger  120  in order. The second heat exchanger  130  may remove moisture included in the air passing through the second heat exchanger  130  by condensing the air, and accordingly, the air passing through the second heat exchanger  130  may be cooled and dehumidified. The first heat exchanger  120  may heat the air from which moisture has been removed by the second heat exchanger  130  by condensing the refrigerant. Because the air cooled by passing through the second heat exchanger  130  is heated by the first heat exchanger  120 , temperature of the air passed through the first heat exchanger  120  may be higher than temperature of the air immediately passed through the second heat exchanger  130 . 
     Therefore, relative humidity of the air passed through the second heat exchanger  130  and the first heat exchanger  120  may be lower than relative humidity of the air passed only through the second heat exchanger  130 . Accordingly, air having temperature and humidity at which a user may feel comfortable may be supplied to the indoor space. Because the ventilation apparatus  100  operating in the second dehumidification mode discharges dried air having temperature that is the same as or similar to room temperature to the indoor space, the second dehumidification mode is also referred to as a ‘fixed temperature dehumidification mode’. 
     In the ventilation mode, a refrigerant may be not supplied to the first heat exchanger  120  and the second heat exchanger  130 , and only heat exchange between room air and outside air may occur in the total heat exchanger  110 . The processor  192  may block a flow of a refrigerant that enters the ventilation apparatus  100 , block a refrigerant entered the ventilation apparatus  100  from entering the first heat exchanger  120  and the second heat exchanger  130 , or turn off the outdoor unit  200  to operate the ventilation apparatus  100  in the ventilation mode. 
     Referring to  FIG.  3   , the housing  101  may include a connecting flow path  102   b  connecting the first intake room  104  with the second intake room  106 . The connecting flow path  102   b  may be positioned between the first intake room  102   b  and the second intake room  106 , and may be positioned on a partition wall  108  partitioning the first intake room  104  from the second intake room  106 . The connecting flow path  102   b  may be formed by cutting at least one portion of the partition wall  108 . By opening the connecting flow path  102   b , the first intake room  104  may communicate with the second intake room  106 . 
     The ventilation apparatus  100  may include various dampers for opening or closing flow paths formed inside the ventilation apparatus  100 . For example, a first damper  330  may open or close a bypass flow path  331  formed to bypass the total heat exchanger  110  between the first inlet  101   a  and the first outlet  101   b . The first damper  330  may be positioned above or below the total heat exchanger  110 . 
     A second damper  340  may be provided between one side of the total heat exchanger  110  and an inner wall of the housing  101 . The second damper  340  may be positioned on the connecting flow path  102   b . The second damper  340  may open or close the connecting flow path  102   b  formed between the first inlet  101   a  and the second inlet  101   c . A third damper  350  may be provided in the first inlet  101   a  and open or close the first inlet  101   a.    
     Although not shown in  FIG.  3   , the ventilation apparatus  100  may include a first duct  601  communicating with the first outlet  101   b  and provided outside the housing  101 , a second duct  602  communicating with the second inlet  101   c  and provided outside the housing  101 , and a third duct  603  connecting the first duct  601  with the second duct  602  and forming a return flow path between the first outlet  101   b  and the second inlet  101   c . The ventilation apparatus  100  may include a fourth damper  360  provided inside the third duct  603  to open and close the third duct  603 . 
     A degree of opening of each of the first damper  330 , the second damper  340 , the third damper  350 , and the fourth damper  360  may be adjusted. 
     Meanwhile, as use of the ventilation apparatus  100  is accumulated, foreign materials (for example, dust) may be attached to a surface of the total heat exchanger  110 . As a result of a great temperature difference (for example, a temperature difference that is greater than 5° C.) between outside temperature and room temperature, moisture may be generated by condensation during a process of heat exchange between room air and outside air in the total heat exchanger  110 . In a case in which driving of the ventilation apparatus  100  is finished in a state in which moisture is generated in the total heat exchanger  110 , a mold may be formed by the foreign materials (for example, dust) attached to the surface of the total heat exchanger  110  and the moisture. In a case in which air passed through the total heat exchanger  110  on which the mold is formed is supplied to the indoor space, quality of room air may deteriorate. Accordingly, by performing a drying operation for the total heat exchanger  110  in the ventilation apparatus  100 , the total heat exchanger  110  may be prevented from being contaminated. 
     The drying operation for the total heat exchanger  110  may be performed based on a preset schedule. That is, the drying operation for the total heat exchanger  110  may be performed one time or repeated periodically according to a schedule. A schedule for drying the total heat exchanger  110  may change by a user input. Also, the drying operation for the total heat exchanger  110  may be performed in response to a user input including a dry command for the total heat exchanger  110 . The user input may be obtained through an inputter  180  of the ventilation apparatus  100  or an inputter  52  of an integrated controller  50 . The drying operation for the total heat exchanger  110  may be performed after a ventilation operation is finished. 
     The ventilation apparatus  100  may perform various drying operations for the total heat exchanger  110  according to a difference value between first temperature of outside air and second temperature of room air. By a ventilation operation (for example, the first dehumidification mode, the second dehumidification mode, or the ventilation mode) of the ventilation apparatus  100 , room air may be maintained at appropriate temperature and humidity, and accordingly, the room air may be suitable to dry the total heat exchanger  110 . The ventilation apparatus  100  may operate at least one of the first blower  109   a  or the second blower  109   b  based on a difference value between first temperature of outside air and second temperature of room air to perform a drying operation for the total heat exchanger  110 . For example, according to an identification that a difference value between first temperature of outside temperature and second temperature of room air is smaller than or equal to a preset threshold value (for example, 5° C.), a first drying operation for the total heat exchanger  110  may be performed. During the first drying operation, both the first blower  109   a  communicating with the first outlet  101   b  and the second blower  109   b  communicating with the second outlet  101   d  may operate. Also, during the first drying operation, the first damper  330  for opening or closing the bypass flow path  331  may open, the third damper  330  provided in the first inlet  101   a  may open, and the second damper  340  provided in the connecting flow path  102   b  between the first inlet  101   a  and the second inlet  101   c  may be closed. 
     In other words, during the first drying operation, outside air sucked through the first inlet  101   a  may be guided to the first outlet  101   b  along the bypass flow path  331 , without passing through the total heat exchanger  110 . Room air sucked through the second inlet  101   c  may pass through the total heat exchanger  110  and then be discharged to the outside through the second outlet  101   d . A flow path through which room air sucked through the second inlet  101   c  flows to the outside of the ventilation apparatus  100  is referred to as a ‘first flow path’. 
     As another example, according to an identification that a difference value between first temperature of outside air and second temperature of room air is greater than the preset threshold value (for example, 5° C.), a second drying operation for the total heat exchanger  110  may be performed. During the second drying operation, the second blower  109   b  and the first blower  109   a  may operate alternately. Also, during the second drying operation, the first damper  330  may be closed, the third damper  350  may also be closed, and the second damper  340  may open and be closed alternately. During the second drying operation for the total heat exchanger  110 , closing and opening of the second damper  340  may correspond to the alternate operation of the second blower  109   b  and the first blower  109   a.    
     For a first time of the second drying operation, all of the first damper  330 , the second damper  340 , and the third damper  350  may be closed and the second blower  109   b  communicating with the second outlet  101   d  may operate. Also, the first blower  109   a  may stop. Accordingly, room air sucked through the second inlet  101   c  may pass through the total heat exchanger  110  and then be discharged to the outside through the second outlet  101   d . In contrast, outside air may no longer enter through the first inlet  101   a . In other words, for the first time, the total heat exchanger  110  may be dried through the first flow path for moving room air to the outside of the ventilation apparatus  100 . A drying operation in which the second damper  340  is closed and the second blower  109   b  operates for the first time is referred to as a ‘third drying operation’. 
     In the second drying operation, for a second time after the first time elapses, the first damper  330  and the third damper  350  may be closed, the second damper  340  may open, and the first blower  109   a  may operate. Also, for the second time, the second blower  109   b  may stop. Accordingly, room air sucked through the second inlet  101   c  may pass through the connecting flow path  102   b , pass through the filter  112  and the total heat exchanger  110 , and then be discharged to the indoor space through the first outlet  101   b . For the second time, outside air may no longer enter through the first inlet  101   a . A flow path through which sucked room air again flows to the indoor space is referred to as a ‘second flow path’. In other words, for the second time, the total heat exchanger  110  may be dried by the second flow path through which room air again flows to the indoor space. A drying operation in which the second damper  340  opens and the first blower  109   a  operates for the second time is referred to as a ‘fourth drying operation’. That is, the second drying operation may include the third drying operation and the fourth drying operation. 
     By performing the second drying operation using the first flow path and the second flow path sequentially, the total heat exchanger  110  may be dried in both directions, and drying efficiency may be improved. 
     Also, in the second drying operation for the total heat exchanger  110 , the compressor  200  may operate to supply a refrigerant to the heat exchangers  120  and  130 . Accordingly, air dehumidified by the heat exchangers  120  and  130  may be supplied to the indoor space through the first outlet  101   b . In other words, the compressor  200  may operate for the second time after the first time elapses from a start of the second drying operation. 
     During the second drying operation, the fourth damper  360  may open in correspondence to an operation of the first blower  109   a , and may be closed in correspondence to a stop of the first blower  109   a . In other words, the fourth damper  360  may open for the second time after the first time elapses from a start of the second drying operation. The fourth damper  360  may be closed based on an elapse of the second time. Air dehumidified by passing through the heat exchangers  120  and  130  may be discharged through the first outlet  101   b  and then again guided to the second inlet  101   c  through the third duct  603 . 
     The first time for the second drying operation may be set to a longer time than the second time. A sum of the first time and the second time may be a total drying time (for example, 20 minutes) for the total heat exchanger  110 . That is, a sum of the first time and the second time may be a total drying time by the second drying operation. For example, the first time may be set to ⅔ of the total drying time, and the second time may be set to ⅓ of the total drying time, although not limited thereto. The first time and the second time may be set to different times according to a design. 
     In a process of drying the total heat exchanger  110 , air passed through the total heat exchanger  110  may contain moisture. For the first time of the second drying operation, air passed through the total heat exchanger  110  may be discharged to the outside. For the second time of the second drying operation, air passed through the total heat exchanger  110  may be again supplied to the indoor space. Accordingly, setting the first time to a longer time than the second time may be more effective in maintaining good air quality of an indoor space. 
       FIG.  4    is an exploded perspective view of a ventilation apparatus according to an embodiment of the disclosure.  FIG.  5    is a perspective view showing a bottom of a ventilation apparatus according to an embodiment of the disclosure after some components of the ventilation apparatus are removed.  FIG.  6    shows a first internal housing of the ventilation apparatus shown in  FIG.  4    after the first internal housing is turned up and down.  FIG.  7    shows a second internal housing of the ventilation apparatus shown in  FIG.  4    after the second internal housing is turned up and down. 
     Referring to  FIG.  4   , the ventilation apparatus  100  may include a drain tray  125  for collecting condensed water generated by the heat exchangers  120  and  130 . The drain tray  125  may be positioned below the heat exchangers  120  and  130  in an up-down direction Z. 
     The housing  101  may include a first internal housing  310  and a second internal housing  320 . The second internal housing  320  may be coupled with the first internal housing  310  in the up-down direction Z. The first and second internal housings  310  and  320  may be provided as insulations. For example, the first and second internal housings  310  and  320  may be EPS insulations such as polystyrene, although not limited thereto. However, the first and second internal housings  310  and  320  may be formed of various insulations for maintaining air flowing through the intake flow path  102  and the exhaust flow path  103  at constant temperature. 
     The ventilation apparatus  100  may include covers  410  and  420  forming an outer appearance of the housing  101  and covering the first and second internal housings  310  and  320 . The covers  410  and  420  may include a first cover  410  positioned at a lower location in the up-down direction Z, and a second cover  420  positioned above the first cover  410  and coupled with the first cover  410 . The first cover  410  may form a lower outer appearance of the ventilation apparatus  100 , and the second cover  420  may form an upper outer appearance of the ventilation apparatus  100 . The first and second covers  410  and  420  may cover the first and second internal housings  310  and  320  to protect the first and second internal housings  310  and  320  from the outside. For example, the first and second covers  410  and  420  may be provided as plastic molded products. 
     The first internal housing  310  may be inserted in the first cover  410 , and the second internal housing  320  may be inserted in the second cover  420 . The first cover  410 , the first internal housing  310 , the second internal housing  320 , and the second cover  420  may be positioned in this order in a direction from a lower portion of the ventilation apparatus  100  toward an upper portion of the ventilation apparatus  100 . 
     Components of the ventilation apparatus  100 , such as the total heat exchanger  110 , the filter  112 , the first and second blowers  109   a  and  109   b , the heat exchangers  120  and  130 , and the drain tray  125 , may be supported by the first internal housing  310  and/or the second internal housing  320 . 
     In the first internal housing  310 , a first hole  315  may be provided. The total heat exchanger  110 , the filter  112 , and the drain tray  125  may be separable from the ventilation apparatus  100  through the first hole  315  of the first internal housing  310 . The second internal housing  320  may include a second hole  325  corresponding to the first hole  315  of the first internal housing  310 . 
     The first cover  410  may include a body portion  411  being in a shape of a quadrilateral frame, a plate portion  412  detachably coupled with the body portion  411  and being in a shape of a plate, and a lower cover portion  413  covering the plate portion  412  from below. The plate portion  412  of the first cover  410  may include a plate body  412   a , a first surface  412   b  of the plate body  412   a , and a second surface being opposite to the first surface  412   b.    
     The plate portion  412  of the first cover  410  may include a third hole  412   d  corresponding to the first hole  315  of the first internal housing  310 . The third hole  412   d  may be formed in the plate body  412   a . Because the third hole  412   d  corresponds to the first hole  315 , the third hole  412   d  may be asymmetrically formed in the plate body  412   a  with respect to any one of a longer axis L and a shorter axis S of the housing  101 . 
     The plate portion  412  of the first cover  410  may be coupled with the body portion  411  such that the first surface  412   b  faces downward. The third hole  412   d  may be formed in the same shape as the first hole  315 , and overlap with the first hole  315  in the up-down direction Z. 
     As shown in  FIG.  5   , upon separating of the lower cover  413  from the first cover  410 , the total heat exchanger  110 , the filter  112 , and the drain tray  125  may be exposed from below the ventilation apparatus  100 . Accordingly, a user may easily separate the total heat exchanger  110 , the filter  112 , and the drain tray  125  from the ventilation apparatus  100  as necessary. 
     Referring to  FIG.  6   , the first internal housing  310  may include a first inlet forming portion  311  (see  FIG.  3   ) forming a portion of the first inlet  101   a , a first outlet forming portion  312  forming a portion of the first outlet  101   b , a second inlet forming portion  313  forming a portion of the second inlet  101   c , and a second outlet forming portion  314  (see  FIG.  3   ) forming a portion of the second outlet  101   d . The first outlet forming portion  312  may be symmetrical to the second outlet forming portion  314  with respect to the longer axis L of the ventilation apparatus  100 . The first inlet forming portion  311  may also be symmetrical to the second inlet forming portion  313  with respect to the longer axis L of the ventilation apparatus  100 . 
     The first hole  315  through which the total heat exchanger  110 , the filter  112 , and the drain tray  125  are withdrawn may be divided into a first area  315   a  through which the total heat exchanger  110  and the filter  112  are withdrawn and a second area  315   b  through which the drain tray  125  is withdrawn. The first area  315   a  of the first hole  315  may be connected with the second area  315 , although not limited thereto. However, the first area  315   a  may be separated from the second area  315   b.    
     The total heat exchanger  110  may be in a shape of a regular hexahedron. The total heat exchanger  110  may have a square section. Because the filter  112  is adjacent to the intake terminal  110   a  of the total heat exchanger  110 , the first area  315   a  of the first hole  315  may be in a shape of a rectangle. Through the first area  315   a  of the first hole  315 , the total heat exchanger  110  and the filter  112  may be exposed to the outside. 
     The second area  315   b  of the first hole  315  may have a shape corresponding to the drain tray  125 . For example, the second area  315   b  may be formed in a shape of a polygon, although not limited thereto. However, the second area  315   b  may have various shapes. 
     Referring to  FIG.  7   , the second internal housing  320  may include a first inlet forming portion  321  forming a portion of the first inlet  101   a , a first outlet forming portion  322  forming a portion of the first outlet  101   b , a second inlet forming portion  323  forming a portion of the second inlet  101   c , and a second outlet forming portion  324  forming a portion of the second outlet  101   d . The first outlet forming portion  322  may be symmetrical to the second outlet forming portion  324 . The first inlet forming formation  321  may also be symmetrical to the second inlet forming portion  323 . 
     By assembling the first internal housing  310  and the second internal housing  320  together in the up-down direction Z, the first inlet  101   a , the first outlet  101   b , the second inlet  101   c , and the second outlet  101   d  may be formed. By positioning one surface of the first internal housing  310  in parallel to the other surface  326  of the second internal housing  320 , the first hole  315  of the first internal housing  310  may also be positioned in parallel to the second hole  325  of the second internal housing  320 . 
     A side in which the first inlet  101   a  and the second outlet  101   d  are positioned in a front-rear direction X is referred to as one side of the housing  101 , and a side in which the second inlet  101   c  and the first outlet  101   b  are positioned is referred to as the other side of the housing  101 . The total heat exchanger  110  may be adjacent to the one side of the housing  101 . Because the heat exchangers  120  and  130  are adjacent to the first outlet  101   b  and the first blower  109   a  inside the second intake room  105 , the total heat exchanger  110  may be most adjacent to the first inlet  101   a  to secure a wide space of the second intake room  105 . 
     The first intake room  104 , the second intake room  105 , the first exhaust room  106 , and the second exhaust room  107  may be partitioned by partition walls  108  formed by the first internal housing  310  and the second internal housing  320 . Also, the partition walls  108  may function to support the total heat exchanger  110 . 
     An upper surface of the total heat exchanger  110  may be spaced from the other surface  326  of the second internal housing  320 . A vertical distance from the upper surface of the total heat exchanger  110  and the other surface  326  of the second internal housing  320  may depend on a design. A size of a space formed between the upper surface of the total heat exchanger  110  and the other surface  326  of the second internal housing  320  may also depend on the design. 
     A first molding  328  and a second molding  329  may be provided between the upper surface of the total heat exchanger  110  and the other surface  326  of the second internal housing  320 . By the first molding  328  and the second molding  329 , room air entered through the second inlet  101   c  may be prevented from flowing to the second outlet  101   d  through the space above the total heat exchanger  110 . However, outside air entered through the first inlet  101   a  may flow to the first outlet  101   b  through the space above the total heat exchanger  110 . 
     In the second internal housing  320 , the first damper  330  may be provided. By coupling the first internal housing  310  with the second internal housing  320 , the first damper  330  may be positioned above the total heat exchanger  110 . The first damper  330  may open or close the bypass flow path  331  formed between the first inlet  101   a  and the first outlet  101   b . In  FIG.  7   , the first damper  330  is shown to be positioned above the total heat exchanger  110 , although not limited thereto. However, the first damper  330  may be positioned above or below the total heat exchanger  110 . 
     Upon opening of the first damper  330 , outside air sucked through the first inlet  101   a  may move to the first outlet  101   b  through the bypass flow path  331  formed between the upper surface of the total heat exchanger  110  and the second internal housing  320 . In this case, the outside air may not pass through the total heat exchanger  110  due to a difference in flow velocity. During the first drying operation for the total heat exchanger  110 , the first damper  330  may open. 
     The first damper  330  may be positioned between the first molding  328  and the second molding  329 , and supported by the first molding  328  and the second molding  329 . The first damper  330  may be positioned perpendicularly to the first molding  328  and the second molding  329 , and may be rotatable. The first damper  330  may be in a shape of a rectangle. The first damper  330  may rotate toward the first intake room  104  or toward the first exhaust room  105 . 
       FIG.  8    shows an integrated air conditioning system including a ventilation apparatus according to an embodiment of the disclosure.  FIG.  9    shows a circulation of a refrigerant in an integrated air conditioning system according to an embodiment of the disclosure. 
     Referring to  FIG.  8   , an integrated air conditioning system  2  may include the ventilation apparatus  100 , the outdoor unit  200 , a plurality of indoor units ( 30 :  30   a ,  30   b ,  30   c , and  30   d ), and an integrated controller  50 . The ventilation apparatus  100  may be connected with the outdoor unit  200  by a refrigerant pipe P 1 . The refrigerant pipe P 1  may correspond to the first refrigerant pipe  121  described above. The plurality of indoor units  30  may be connected with the outdoor unit  200  by a refrigerant pipe P 2 . The outdoor unit  200  may supply a refrigerant to each of the plurality of indoor units  30  through the refrigerant pipe P 2 . 
     The plurality of indoor units  30  may be respectively installed inside a plurality of different indoor spaces. For example, the plurality of indoor units  30  may be respectively installed in a plurality of offices, a plurality of guestrooms, or a plurality of rooms, which are partitioned inside a building. As a result of operating of the plurality of indoor units  30 , indoor spaces where the plurality of indoor units  30  are respectively installed may be air-conditioned (for example, cooled). 
     The ventilation apparatus  100  may be installed in various spaces inside a building. For example, the ventilation apparatus  100  may be installed in a space, such as a balcony or utility room of an apartment. The first inlet  101   a , the second inlet  101   c , the first outlet  101   b , and the second outlet  101   d , provided in the housing  101  of the ventilation apparatus  100 , may be respectively connected with ducts. Ducts connected with the second inlet  101   c  and the first outlet  101   b  may extend to an indoor space. For example, in a ceiling or wall of an indoor space, a hole communicating with the ventilation apparatus  100  may be provided. Ducts connected with the first inlet  101   a  and the second outlet  101   d  may extend to an outdoor space. 
     A single ventilation apparatus  100  and a single outdoor unit  200  are shown, however, one or more ventilation apparatuses  100  and one or more outdoor units  200  may be provided. Also, four indoor units  30  are shown. However, the number of the indoor units  30  is not limited to four. One or more indoor units  30  may be provided. 
     The integrated controller  50  may be electrically connected with the ventilation apparatus  100 , the outdoor unit  200 , and the plurality of indoor units  30 . The integrated controller  50  may be electrically connected with the ventilation apparatus  100 , the outdoor unit  200 , and the plurality of indoor units  30  through a communication line CL. The integrated controller  50  may control operations of the ventilation apparatus  100 , the outdoor unit  200 , and the plurality of indoor units  30 . 
     The integrated controller  50  may obtain a user input, operate the integrated air conditioning system  2  in response the user input, and display information of the integrated air conditioning system  2 . The integrated controller  50  may control the ventilation apparatus  100  and the indoor units  30  based on room temperature and room humidity of indoor spaces where the indoor units  30  are installed. 
     By appropriately controlling operations of the ventilation apparatus  100  and the indoor units  300  based on room temperature and room humidity, cooling efficiency and dehumidification efficiency may be improved, and energy for cooling and dehumidification may be saved. 
     Referring to  FIG.  9   , the integrated air conditioning system  2  may include the ventilation apparatus  100 , the outdoor unit  200 , and a second apparatus  30 . The outdoor unit  200  may be connected with the second apparatus  30 . The second apparatus  30  may correspond to an ‘indoor unit’ of an air conditioner. The second apparatus  30  may receive a refrigerant discharged from the compressor  210  and then condensed in the condenser  220 . Hereinafter, the second apparatus  30  will be referred to as an ‘indoor unit’. 
     The outdoor unit  200  may also supply a refrigerant to the ventilation apparatus  100 . A refrigerant discharged from the condenser  220  of the outdoor unit  200  may be supplied to the ventilation apparatus  100 , or a refrigerant discharged from the compressor  210  of the outdoor unit  200  may be supplied to the ventilation apparatus  100 . 
     For example, the first refrigerant pipe  121  may diverge from the refrigerant pipe  221  connecting the condenser  220  of the outdoor unit  200  with the compressor body  211  of the outdoor unit  200 . A refrigerant not passed through the condenser  220  of the outdoor unit  200  may flow through the first refrigerant pipe  121 , and a high-temperature, high-pressure refrigerant may be supplied to the first heat exchanger  120 . At this time, the first expander  160  may expand or not expand a part of the refrigerant. Because the refrigerant flowing through the first refrigerant pipe  121  is a high-temperature, high-pressure refrigerant not condensed, the first heat exchanger  120  may function as a condenser for heating air while condensing a refrigerant. That is, the ventilation apparatus  100  may operate in the second dehumidification mode regardless of a degree of opening of the first expander  160 . The ventilation apparatus  100  may also operate in the ventilation mode. 
     As another example, as described above with reference to  FIG.  2   , the first refrigerant pipe  121  may itself be connected with the condenser  210  of the outdoor unit  200 . In this case, a refrigerant condensed in the condenser  220  may be supplied to the ventilation apparatus  100  through the first refrigerant pipe  121 , although not limited thereto. 
     For example, a separate condenser (not shown) may be provided on the first refrigerant pipe  121 . A refrigerant flowing through the first refrigerant pipe  121  may pass through the condenser (not shown) provided on the first refrigerant pipe  121  to be condensed and then enter the first expander  160  in the condensed state. The ventilation apparatus  100  may operate in the first dehumidification mode or the second dehumidification mode. The ventilation apparatus  100  may also operate in the ventilation mode. 
     A refrigerant discharged from the first heat exchanger  120  may be expanded by the second expander  170 , and then enter the second heat exchanger  130 . The second heat exchanger  130  may evaporate the refrigerant to thereby condense moisture in air and remove the moisture. In this way, the ventilation apparatus  100  and the indoor unit  30  may be driven at the same time by using the single outdoor unit  200 . 
     The method for operating the ventilation apparatus  100 , as described above, may also be applied to the integrated air conditioning system  2  described above with reference to  FIGS.  8  and  9   . 
       FIG.  10    is a control block diagram showing configurations of a ventilation apparatus according to an embodiment of the disclosure. 
     Referring to  FIG.  10   , the ventilation apparatus  100  may include, as described above, the outside temperature sensor  141 , the room temperature sensor  142 , the discharge temperature sensor  143 , the room humidity sensor  150 , the first sterilizer  111 , the second sterilizer  112 , the first blower  109   a , the second blower  109   b , the first expander  160 , the second expander  170 , the first damper  330 , the second damper  330 , the third damper  350 , and the fourth damper  360 . 
     Also, the ventilation apparatus  100  may include the inputter  180 , the memory  191 , and the processor  192 . The processor  192  may be electrically connected with components of the ventilation apparatus  100 , and control the individual components. For example, the processor  192  may adjust a degree of opening of each of the first damper  330 , the second damper  340 , the third damper  350 , and the fourth damper  360 . 
     The inputter  180  may obtain various user inputs for operations of the ventilation apparatus  100 . The inputter  180  may output an electrical signal (voltage or current) corresponding to a user input to the processor  192  of the ventilation apparatus  100 . The inputter  180  may include various buttons, a dial, and/or a touch display. 
     For example, the inputter  180  may obtain a user input including a drying command for the total heat exchanger  110 . The processor  192  may perform a first drying operation or a second drying operation for the total heat exchanger  110 , based on the drying command for the total heat exchanger  110 . Also, the inputter  180  may obtain a user input for adjusting a schedule for drying the total heat exchanger  110 . The processor  192  may perform the first drying operation or the second drying operation for the total heat exchanger  110  periodically based on a schedule set in advance according to a user input. 
     The memory  191  may memorize/store various information required for operations of the ventilation apparatus  100 . The memory  191  may store instructions, applications, data, and/or programs required for operations of the ventilation apparatus  100 . The processor  192  may generate control signals for controlling the operations of the ventilation apparatus  100  based on the instructions, applications, data, and/or programs stored in the memory  191 . 
     Also, the ventilation apparatus  100  may include a communication interface for communicating with the outdoor unit  200  and/or the integrated controller  50 . The ventilation apparatus  100  may operate based on a control signal transmitted from the integrated controller  50  through the communication interface. 
     As described above, as use of the ventilation apparatus  100  is accumulated, the total heat exchanger  110  may be contaminated. Due to moisture generated by heat-exchange between outside air and room air, a mold may be formed in the total heat exchanger  110 . To properly manage the total heat exchanger  110 , the total heat exchanger  110  may need to be dried. Drying the total heat exchanger  110  after the ventilation apparatus  100  completes an operation of sucking outside air and ventilating an indoor space may be preferable. 
     The processor  192  of the ventilation apparatus  100  may obtain first temperature (outside temperature) of outside air from the outside temperature sensor  141 , and obtain second temperature (room temperature) of room air from the room temperature sensor  142 . The processor  192  may operate at least one of the first blower  109   a  or the second blower  109   b , based on a difference value between the first temperature of the outside air and the second temperature of the room air, and perform a drying operation for the total heat exchanger  110 . According to an identification that the difference value between the first temperature of the outside air and the second temperature of the room air is smaller than or equal to a preset threshold value (for example, 5° C.), the processor  192  of the ventilation apparatus  100  may perform the first drying operation for the total heat exchanger  110 . According to an identification that the difference value between the first temperature of the outside air and the second temperature of the room air is greater than the preset threshold value (for example, 5° C.), the processor  192  of the ventilation apparatus  100  may perform the second drying operation for the total heat exchanger  110 . 
     The processor  192  of the ventilation apparatus  100  may perform a drying operation for the total heat exchanger  110  based on a preset schedule. That is, a drying operation for the total heat exchanger  110  may be performed one time or repeated periodically according to a schedule. The schedule for drying the total heat exchanger  110  may change by a user input. Also, the processor  192  may perform the first drying operation or the second drying operation in response to a user input including a drying command for the total heat exchanger  110 . 
     The processor  192  of the ventilation apparatus  100  may open the first damper  330  and the third damper  350 , close the second damper  340 , and operate the first blower  109   a  and the second blower  109   b , thereby performing the first drying operation. 
     During the first drying operation, outside air entered through the first inlet  101   a  as a result of opening of the first damper  330  may move to the first outlet  101   b  through the bypass flow path  331 . That is, during the first drying operation, outside air may not pass through the total heat exchanger  110 . In contrast, room air entered through the second inlet  101   c  may pass through the total heat exchanger  110  to dry the total heat exchanger  110 . Because the total heat exchanger  110  is made of a paper material, the total heat exchanger  110  may be entirely dried only by passing room air through the total heat exchanger  110  in one direction. A flow path through which room air sucked through the second inlet  101   c  flows to the outside of the ventilation apparatus  100  is referred to as a ‘first flow path’. 
     In a case in which a difference value between first temperature of outside air and second temperature of room air is smaller than or equal to the preset threshold value, an amount of heat exchange between the room air and the outside air may be relatively small. Therefore, no condensation may occur in the total heat exchanger  110  or an amount of condensation in the total heat exchanger  110  may be small. Accordingly, by performed only the first drying operation, the total heat exchanger  110  may be sufficiently dried. 
     During the second drying operation, the processor  192  of the ventilation apparatus  100  may close the first damper  330  and the third damper  350 , alternately close and open the second damper  340 , and alternately operate the second blower  109   b  and the first blower  109   a.    
     As described above, the second drying operation may include the third drying operation and the fourth drying operation using different flow paths. For the second drying operation, the processor  192  may close the first damper  330 , the second damper  340 , and the third damper  350 , and operate the second blower  109   b  for a first time. After the first time elapses, the processor  192  may also close the first damper  330  and the third damper  350 , open the second damper  340 , and operate the first blower  109   a  for a second time. Unlike this, the processor  192  may open the second damper  340  and operate the first blower  109   a  for the first time, and for the second time, the processor  192  may close the second damper  340  and operate the second blower  109   b.    
     For the first time of the second drying operation, room air sucked through the second inlet  101   c  may pass through the total heat exchanger  110  along the first flow path, and then be discharged to the outside through the second outlet  101   d . For the second time of the second drying operation, room air sucked through the second inlet  101   c  may pass through the total heat exchanger  110  along the second flow path and then be discharged to the indoor space through the first outlet  101   b . By performing the second drying operation using the first flow path and the second flow path sequentially, the total heat exchanger  110  may be dried in both directions, and drying efficiency may be improved. 
     A sum of the first time and the second time for the second drying operation may be a total drying time (for example, 20 minutes) of the total heat exchanger  110 . That is, a sum of the first time and the second time may be a total drying time by the second drying operation. The processor  192  may set the first time to a longer time than the second time. For example, the first time may be set to ⅔ of the total drying time, and the second time may be set to ⅓ of the total drying time, although not limited thereto. However, the first time and the second time for the second drying operation may be set to different times according to a design. 
     In a process of drying the total heat exchanger  110 , air passed through the total heat exchanger  110  may contain moisture. For the first time of the second drying operation, air passed through the total heat exchanger  110  may be discharged to the outside of the ventilation apparatus  100 . For the second time of the second drying operation, air passed through the total heat exchanger  110  may be again supplied to the indoor space. Accordingly, setting the first time to a longer time than the first time may be more effective in maintaining good air quality of an indoor space. 
     Also, during the second drying operation, the processor  192  of the ventilation apparatus  100  may operate the compressor  200  to supply a refrigerant to the heat exchangers  120  and  130 , and control the first expander  160  and the second expander  170 . Accordingly, air dehumidified by the heat exchangers  120  and  130  may be discharged to the indoor space through the first outlet  101   b.    
     In addition, during the second drying operation, the processor  192  of the ventilation apparatus  100  may open the fourth damper  360  in correspondence to an operation of the first blower  109   a , and close the fourth damper  360  in correspondence to a stop of the first blower  109   a . In other words, for the second time of the second drying operation, the processor  192  may open the fourth damper  360  to open the return flow path formed by the third duct  603 . Air dehumidified by passing through the heat exchangers  120  and  130  may be discharged through the first outlet  101   b  and then again guided to the second inlet  101   c  through the third duct  603 . The processor  192  may close the fourth damper  360  based on an elapse of the second time and/or a stop of the first blower  109   a.    
       FIG.  11    is a control block diagram showing configurations of an integrated controller according to an embodiment of the disclosure. 
     Referring to  FIG.  11   , the integrated controller  50  may include a display  51 , the inputter  52 , a communication interface  53 , a memory  54 , and a processor  55  electrically connected with the display  51 , the inputter  52 , the communication interface  53 , and the memory  54 . The integrated controller  50  may provide a user interface for interactions between the integrated air conditioning system  2  and a user. 
     The display  51  may display information about a state and/or operation of the integrated air conditioning system  2 . The display  51  may display information input by the user or information to be provided to the user through various screens. The display  51  may display information related to an operation of the integrated air conditioning system  2  with at least one of an image or text. Also, the display  51  may display a Graphic User Interface (GUI) for enabling a control of the integrated air conditioning system  2 . That is, the display  51  may display a User Interface (UI) element such as an icon. 
     The display  51  may include various types of display panels. For example, the display  51  may include a Liquid Crystal Display (LCD) panel, a Light Emitting Diode (LED) panel, an Organic Light Emitting Diode (OLED) panel, or a micro LED panel. 
     The display  51  may be implemented as a touch display. The touch display may include a display panel displaying an image, and a touch panel for receiving a touch input. The display panel may convert image data received from the processor  55  into an optical signal which is visible to a user. The touch panel may identify a touch input by a user, and provide an electrical signal corresponding to the touch input to the processor  55 . 
     The inputter  52  of the integrated controller  50  may output an electrical signal (voltage or current) corresponding to a user input to the processor  55 . The inputter  52  may include various buttons or a dial. In the display  51  implemented as a touch display, the inputter  52  may be not provided in the integrated controller  50 . That is, the integrated controller  50  may obtain a user input. For example, the integrated controller  50  may obtain a user input for setting target temperature and target humidity, a user input for turning on or off the ventilation apparatus  100  and each of the indoor units  30 , or a user input for setting an operation mode of the ventilation apparatus  100  and each of the indoor units  30 . 
     The communication interface  53  may communicate with the ventilation apparatus  100 , the outdoor unit  200 , and the indoor units  30 . The communication interface  53  of the integrated controller  50  may be connected with communication interfaces of the ventilation apparatus  100 , the outdoor unit  200 , and each of the indoor units  30  through the communication line CL. The integrated controller  50  may transmit a control signal to the ventilation apparatus  100 , the outdoor unit  200 , and the indoor units  30  through the communication interface  53 . 
     Also, the communication interface  53  may include a wired communication module and/or a wireless communication module for communicating with an external device (for example, a mobile device or a computer). The wired communication module may communicate with an external device through a wide area network such as the Internet, and the wireless communication module may communicate with an external device through an access point connected with a wide area network. Thereby, a user may control the integrated air conditioning system  2  remotely. 
     The memory  54  may memorize/store various information required for operations of the integrated air conditioning system  2 . The memory  54  may store instructions, applications, data, and/or programs required for operations of the integrated air conditioning system  2 . For example, the memory  54  may store data about reference temperature and reference humidity for setting operations of the ventilation apparatus  100  and the indoor units  30 . 
     The memory  54  may include a volatile memory, such as Static Random Access Memory (S-RAM) or Dynamic Random Access Memory (D-RAM), for memorizing data temporarily. Also, the memory  54  may include a non-volatile memory, such as Read Only Memory (ROM), Erasable Programmable Read Only Memory (EPROM), or Electrically Erasable Programmable Read Only Memory (EEPROM), for storing data for a long time. 
     The processor  55  may generate a control signal for controlling an operation of the integrated air conditioning system  2  based on the instructions, applications, data, and/or programs stored in the memory  54 . The processor  55  may include a logic circuit and an arithmetic circuit, as hardware. The processor  55  may process data according to a program and/or instruction provided from the memory  54  and generate a control signal according to a result of the processing. The memory  54  and the processor  55  may be implemented as a single control circuit or a plurality of circuits. 
     Meanwhile, components of the ventilation apparatus  100 , the outdoor unit  200 , the indoor units  30 , and the integrated controller  50  are not limited to those described above with reference to  FIGS.  10  and  11   . Some of the components of the ventilation apparatus  100 , the outdoor unit  200 , the indoor units  30 , and the integrated controller  50  may be omitted, or another component may be added. 
       FIG.  12    shows a flow of air inside a ventilation apparatus according to an embodiment of the disclosure during a first drying operation of the ventilation apparatus. 
     Referring to  FIG.  12   , during a second drying operation of the total heat exchanger  110 , the first damper  330  may open to open the bypass flow path  331 , the third damper  350  may open to open the first inlet  101   a , and the second damper  340  provided in the connecting flow path  102   b  between the first inlet  101   a  and the second inlet  101   c  may be closed. Also, during a first drying operation, both the first blower  109   a  communicating with the first outlet  101   b  and the second outlet  101   d  communicating with the second outlet  101   d  may operate. 
     As a result of opening of the first damper  330 , outside air OA entered through the first inlet  101   a  may move to the first outlet  101   b  through the bypass flow path  331  formed above the total heat exchanger  110 . In this case, the outside air OA may not pass through the total heat exchanger  110  due to a difference in flow velocity. In contrast, room air RA entered through the second inlet  101   c  may pass through the total heat exchanger  110  to dry the total heat exchanger  110 . Because the total heat exchanger  110  is made of a paper material, the total heat exchanger  110  may be entirely dried only by passing room air through the total heat exchanger  110  in one direction. A flow path through which room air sucked through the second inlet  101   c  flows to the outside of the ventilation apparatus  100  through the second outlet  101   d  is referred to as a ‘first flow path’. 
     As described above, the first drying operation for the total heat exchanger  110  may be performed according to an identification that a difference value between first temperature of outside air OA and second temperature of room air RA is smaller than or equal to the preset threshold value (for example, 5° C.). 
     In a case in which the difference value between the first temperature of the outside air OA and the second temperature of the room air RA is smaller than or equal to the preset threshold value, an amount of heat exchange between the outside air OA and the room air RA may be relatively small. Therefore, no condensation may occur in the total heat exchanger  110  or an amount of condensation in the total heat exchanger  110  may be small. Accordingly, by performing only the first drying operation, the total heat exchanger  110  may be sufficiently dried. 
     Meanwhile, after the ventilation apparatus  100  operates in the ventilation mode for a preset time or more in a state in which a difference value between first temperature of outside air OA and second temperature of room air RA is smaller than the preset threshold value, a drying operation for the total heat exchanger  110  may be omitted. As the ventilation apparatus  100  operates in the ventilation mode, a difference between first temperature of outside air OA and second temperature of room air may become smaller, and a ventilation operation may dry the total heat exchanger  110 . 
       FIG.  13    shows a flow of air through a first flow path inside a ventilation apparatus according to an embodiment of the disclosure during a second drying operation of the ventilation apparatus.  FIG.  14    shows a flow of air through a second flow path inside a ventilation apparatus according to an embodiment of the disclosure during a second drying operation of the ventilation apparatus. 
     As described above, the ventilation apparatus  100  may perform a second drying operation for the total heat exchanger  110 , according to an identification that a difference value between first temperature of outside air and second temperature of room air is greater than a preset threshold value (for example, 5° C.). During the second drying operation, the second blower  109   b  and the first blower  109   a  may operate alternately. Also, during the second drying operation, the first damper  330  and the third damper  350  may be closed, and the second damper  340  may be closed and open alternately. Because a great temperature difference between outside air OA and room air RA may cause condensation of the total heat exchanger  110 , a drying operation for drying the total heat exchanger  110  may be required to remove condensation. 
     Referring to  FIG.  13   , for a first time of the second drying operation for drying the total heat exchanger  110 , the first damper  330 , the second damper  340 , and the third damper  350  may be closed, and the second blower  109   b  may operate (third drying operation). Also, the first blower  109   a  may stop. Accordingly, room air RA sucked through the second inlet  101   c  may pass through the total heat exchanger  110 , and be discharged to the outside through the second outlet  101   d . In contrast, outside air OA may no longer enter through the first inlet  101   a . In other words, the total heat exchanger  110  may be dried through the first flow path through which room air flows to the outside of the ventilation apparatus  100 . 
     Referring to  FIG.  14   , fora second time of the second drying operation, the first damper  330  and the third damper  350  may be closed, the second damper  340  may open, and the first blower  10   a  may operate (fourth drying operation). Also, the second blower  109   b  may stop. Accordingly, room air RA entered through the second inlet  101   c  may pass through the connecting flow path  102   b , pass through the filter  112  and the total heat exchanger  110 , and then be discharged to an indoor space through the first outlet  101   b . That is, during the second drying operation, outside air may no longer enter through the first inlet  101   a.    
     Also, during the second drying operation for the total heat exchanger  110 , the processor  192  of the ventilation apparatus  100  may operate the compressor  200  to supply a refrigerant to the heat exchangers  120  and  130 , and control the first expander  160  and the second expander  170 . Accordingly, air dehumidified by the heat exchangers  120  and  130  may be discharged to the indoor space through the first outlet  101   b.    
       FIG.  15    shows an embodiment of the disclosure, which is additionally applicable to the second drying operation described in  FIG.  14   . 
     Referring to  FIG.  15   , the ventilation apparatus  100  may include the first duct  601  communicating with the first outlet  101   b  and provided outside the housing  101 , the second duct  602  communicating with the second inlet  101   c  and provided outside the housing  101 , and the third duct  603  connecting the first duct  601  with the second duct  602  and forming a return flow path between the first outlet  101   b  and the second inlet  101   c . The ventilation apparatus  100  may include the fourth damper  360  provided inside the third duct  603  to open and close the third duct  603 . 
     During a second drying operation, the processor  192  of the ventilation apparatus  100  may open the fourth damper  360  in correspondence to an operation of the first blower  109   a , and close the fourth damper  360  in correspondence to a stop of the first blower  109   a . In other words, for the second time of the second drying operation, the processor  192  may open the fourth damper  360  to open the return flow path formed by the third duct  603 . Air dehumidified by passing through the heat exchangers  120  and  130  may be discharged through the first outlet  101   b , and again guided to the second inlet  101   c  through the third duct  603 . The processor  192  may close the fourth damper  360  based on an elapse of the second time and/or a stop of the first blower  109   a . Because air dried by the heat exchangers  120  and  130  is again guided to the second inlet  101   c , drying efficiency of the total heat exchanger  110  may be improved. 
       FIG.  16    is a flowchart illustrating a method for controlling a ventilation apparatus, according to an embodiment of the disclosure. 
     Referring to  FIG.  16   , the processor  192  of the ventilation apparatus  100  may control the outside temperature sensor  141  to measure first temperature of outside air ( 1601 ). The processor  192  may control the room temperature sensor  142  to measure second temperature (room temperature) of room air ( 1602 ). The processor  192  may detect or calculate a difference value between the first temperature of the outside air and the second temperature of the room temperature. 
     The processor  192  may operate at least one of the first blower  109   a  or the second blower  109   b  based on the difference value between the first temperature of the outside air and the second temperature of the room air, and perform a drying operation for the total heat exchanger  110  ( 1603 ). For example, according to an identification that the difference value between the first temperature of the outside air and the second temperature of the room air is smaller than or equal to a preset threshold value (for example, 5° C.), the processor  192  may perform a first drying operation for the total heat exchanger  110 . According to an identification that the difference value between the first temperature of the outside air and the second temperature of the room air is greater than the preset threshold value (for example, 5° C.), the processor  192  may perform a second drying operation for the total heat exchanger  110 . 
       FIG.  17    is a flowchart detailedly illustrating the method for controlling the ventilation apparatus, described in  FIG.  16   . 
     Referring to  FIG.  17   , the processor  192  of the ventilation apparatus  100  may control the outside temperature sensor  141  to measure first temperature of outside air ( 1701 ). The processor  192  may control the room temperature sensor  142  to measure second temperature (room temperature) of room air ( 1702 ). The processor  192  may detect or calculate a difference value between the first temperature of the outside air and the second temperature of the room air ( 1703 ). 
     The processor  192  may compare the difference value between the first temperature of the outside air and the second temperature of the room temperature with a preset threshold value ( 1704 ). According to an identification that the difference value between the first temperature of the outside air and the second temperature of the room temperature is smaller than or equal to the preset threshold value (for example, 5° C.), the processor  192  may set execution of a first drying operation. For the first drying operation, the processor  192  may open the first damper  330  provided on the bypass flow path  331  bypassing the total heat exchanger  110 , close the second damper  340  provided on the connecting flow path  102   b  between the first inlet  101   a  and the second inlet  101   c , and open the third damper  350  provided in the first inlet  101   a  ( 1705 ). At the same time, the processor  192  may perform the first drying operation by operating the first blower  109   a  and the second blower  109   b  ( 1706 ). 
     The first drying operation may be performed for a preset drying time (for example, 20 minutes). According to an elapse of the drying time after the first drying operation starts, the processor  192  may identify that the total heat exchanger  110  has been completely dried, and finish the drying operation for the total heat exchanger  110  ( 1707 ). 
     According to an identification that the difference value between the first temperature of the outside air and the second temperature of the room temperature is greater than the preset threshold value (for example, 5° C.), the processor  192  of the ventilation apparatus  100  may set execution of a second drying operation, and close the first damper  330  and the third damper  350  ( 1708 ). The processor  192  may close the second damper  340  and operate the second blower  109   b  for a first time ( 1709 ). For a second time after the first time elapses, the processor  192  may open the second damper  340  and operate the first blower  109   a  ( 1710 ). 
     The second drying operation may be performed for a preset drying time (for example, 20 minutes). According to an elapse of the drying time after the second drying operation starts, the processor  192  may identify that the total heat exchanger  110  has been completely dried, and finish the drying operation for the total heat exchanger  110  ( 1707 ). 
     As described above, the ventilation apparatus and the control method thereof may prevent a mold from being formed in the total heat exchanger by performing a drying operation for the total heat exchanger. Accordingly, a life cycle of the total heat exchanger may increase, and quality of air that is supplied to a room space may also be improved. 
     The ventilation apparatus and the control method thereof may easily manage the total heat exchanger according to a user&#39;s selection or a preset schedule. 
     Meanwhile, the disclosed embodiments may be implemented in the form of a recording medium that stores instructions executable by a computer. The instructions may be stored in the form of program codes, and when executed by a processor, the instructions may create a program module to perform operations of the disclosed embodiments. 
     A machine-readable storage medium may be provided in the form of a non-transitory storage medium, wherein the term ‘non-transitory’ simply means that the storage medium is a tangible device, and does not include a signal (e.g., an electromagnetic wave), but this term does not differentiate between where data is semi-permanently stored in the storage medium and where the data is temporarily stored in the storage medium. For example, a ‘non-transitory storage medium’ may include a buffer in which data is temporarily stored. 
     The method according to various embodiments of the disclosure may be included and provided in a computer program product. The computer program product may be traded as a product between a seller and a buyer. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read only memory (CD-ROM)), or be distributed (e.g., downloadable or uploadable) online via an application store (e.g., Play Store™) or between two user devices (e.g., smart phones) directly. When distributed online, at least part of the computer program product (e.g., a downloadable app) may be temporarily generated or at least temporarily stored in the machine-readable storage medium, such as a memory of the manufacturer&#39;s server, a server of the application store, or a relay server. 
     So far, the disclosed embodiments have been described with reference to the accompanying drawings. It will be understood by one of ordinary skill in the technical art to which the disclosure belongs that the disclosure can be embodied in different forms from the disclosed embodiments without changing the technical spirit and essential features of the disclosure. Thus, it should be understood that the disclosed embodiments described above are merely for illustrative purposes and not for limitation purposes in all aspects.