Abstract:
A dryer having a waste heat recovery device includes a cabinet, a drum rotatably mounted within the cabinet and having a front surface and a rear surface, an intake duct configured to provide an intake flow path through which air flows into the drum, an exhaust duct configured to exhaust air coming from the drum out of the cabinet, a heater configured to heat air flowing into the drum, and an ambient air duct configured to inhale air from outside the cabinet and supply the air from outside the cabinet into the drum. The waste heat recovery device includes an evaporation unit configured to absorb heat from air that is exhausted from the drum, a condenser unit configured to transfer heat absorbed from the evaporation unit to ambient air that flows into the ambient air duct, and a heat transfer medium configured to transfer heat between the evaporation unit and the condenser unit. The ambient air duct is configured to communicate air from the ambient air duct into the intake duct at a point along a flow path between the drum and the heater.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2013-0071177, filed on Jun. 20, 2013, the contents of which are incorporated by reference herein in their entirety. 
       TECHNICAL FIELD 
       [0002]    The present application relates to a dryer with a waste heat recovery device, and more particularly, to a dryer having a device for recovering and reusing heat energy contained in air exhausted from the dryer. 
       BACKGROUND 
       [0003]    In general, a laundry treating apparatus having a drying function such as a washer or dryer is a device for putting the laundry in a state that washing is completed and the dehydration process is finished into the drum, and supplying hot air into the drum to evaporate the moisture of the laundry and dry the laundry. 
         [0004]    For example, a dryer may include a drum rotatably provided within the body to put the laundry thereinto, a drive motor configured to drive the drum, a blower fan configured to blow air into the drum, and a heating device configured to heat the air flowing into the drum. Furthermore, the heating device may use electrical resistance heat at high temperature generated using an electrical resistance or the heat of combustion generated by burning gas. 
         [0005]    Air coming out of the drum may contain the moisture of the laundry within the drum, thus becoming air under a medium temperature and humidity condition. Here, a dryer can be classified according to a method of treating the medium temperature and humid air, and can be divided into 1) a condensation type (circulation type) dryer for cooling air below its dew-point temperature through the condenser while circulating the medium temperature and humid air without being exhausted to the outside to condensate moisture contained in the medium temperature and humid air, and 2) an exhaustion type dryer for allowing the medium temperature and humid air to be directly exhausted and wasted to the outside. 
         [0006]    In case of the condensation type dryer, in order to condensate air exhausted from the drum, the air should be subject to the process of cooling below the dew-point temperature and heated through the heating device prior to being supplied to the drum. Here, a loss of heat energy contained in the air may be generated while being cooled during the condensation process, and an additional heater or the like may be needed to heat the air to a temperature required for drying. 
         [0007]    In case of the exhaustion type dryer, it may be required to exhaust the medium temperature and humid air to the outside and inhale ambient air to heat the air to a temperature level required for drying through a heating device. In particular, high temperature air being exhausted to the outside contains heat energy transferred by the heating device; because the air is exhausted and wasted to the outside, heat efficiency be reduced. 
         [0008]    Accordingly, in recent years, laundry treating apparatuses for collecting energy required to generate hot air and energy being exhausted to the outside without being used have been introduced to increase energy efficiency, and a laundry treating apparatus having a heat pump system has been introduced as an example of such laundry treating apparatus. The heat pump system may include two heat exchangers, a compressor and an expansion apparatus, and energy contained in the exhausted hot air is recovered and reused in heating up air being supplied to the drum, thereby increasing energy efficiency. 
         [0009]    Specifically, in the heat pump system, an evaporator is provided at the exhaust side, and a condenser at an inlet side of the drum, and thus thermal energy is transferred to refrigerant through the evaporator and then thermal energy contained in the refrigerant is transferred to air flowing into the drum through the condenser, thereby generating hot air using waste energy. Here, a heater for reheating air that has been heated up while passing through the evaporator may be additionally provided therein. 
         [0010]    However, the heat pump system should be additionally provided with a compressor, an expansion apparatus, and the like in addition to the two heat exchangers. As an alternative of the heat pump system, there exists also an example of using a heat pipe. The heat pipe can transfer heat from the high temperature side to the low temperature side while sealed refrigerant repeats evaporation and condensation with no additional power source. 
       SUMMARY 
       [0011]    Accordingly, an object of the present application is to provide a dryer having a waste heat recovery device capable of minimizing changes in drying performance even when used for a long period of time. 
         [0012]    According to one aspect, a dryer having a waste heat recovery device includes a cabinet, a drum rotatably mounted within the cabinet and having a front surface and a rear surface, an intake duct configured to provide an intake flow path through which air flows into the drum, an exhaust duct configured to exhaust air coming from the drum out of the cabinet, a heater configured to heat air flowing into the drum, and an ambient air duct configured to inhale air from outside the cabinet and supply the air from outside the cabinet into the drum. The waste heat recovery device includes an evaporation unit configured to absorb heat from air that is exhausted from the drum, a condenser unit configured to transfer heat absorbed from the evaporation unit to ambient air that flows into the ambient air duct, and a heat transfer medium configured to transfer heat between the evaporation unit and the condenser unit. The ambient air duct is configured to communicate air from the ambient air duct into the intake duct at a point along a flow path between the drum and the heater. 
         [0013]    Implementations of this aspect may include one or more of the following features. For example, the waste heat recovery device may be disposed at a rear side of the drum. The waste heat recovery device may include one or more pulsating heat pipes (PHPs) and a casing in which the one or more PHPs is fixed, wherein the heat transfer medium may be sealed within each of the one or more PHPs. The intake duct may include a back duct located on the rear surface of the drum, and the ambient air duct may be disposed between the casing and the back duct. The casing may define an ambient air inlet port through which ambient air enters the casing, and the casing may be configured to guide ambient air that has passed through the ambient air inlet port into the ambient air duct. The back duct and the ambient air duct may define communication ports disposed to face each other, respectively, and the communication ports may be disposed at a location that is vertically lower than that of the ambient air inlet port. A plurality of the PHPs may extend along a flow direction of air being exhausted. Positions of the plurality of the PHPs may be staggered relative to each other. At least one of the one or more PHPs may include a plurality of fins on a portion corresponding to the condenser unit of the at least one PHP. The plurality of fins may not be included on at least a part of a portion corresponding to the evaporation unit of the one or more PHPs. 
         [0014]    According to another aspect, a dryer having a waste heat recovery device includes a cabinet, a drum rotatably mounted within the cabinet and having a front surface and a rear surface, an exhaust duct configured to exhaust air coming from the drum out of the cabinet, a gas heater configured to heat air flowing into the drum, a funnel configured to collect heated air generated by the gas heater, a back duct configured to supply the heated air discharged from the funnel to the drum, the back duct being located on the rear surface of the drum, and an ambient air duct configured to inhale air from outside the cabinet and supply the air from outside the cabinet into the drum. The waste heat recovery device includes an evaporation unit configured to absorb heat from air that is exhausted from the drum, a condenser unit configured to transfer heat absorbed from the evaporation unit to ambient air that flows into the ambient air duct, and a heat transfer medium configured to transfer heat between the evaporation unit and the condenser unit. The ambient air duct is configured to communicate air from the ambient air duct into the back duct. 
         [0015]    Implementations of this aspect may include one or more of the following features. For example, the waste heat recovery device may include one or more pulsating heat pipes (PHPs) and a casing in which the one or more PHPs is fixed, wherein the heat transfer medium may be sealed within each of the one or more PHPs. The casing may define an ambient air inlet port through which ambient air enters the casing, and the casing may be configured to guide ambient air that has passed through the ambient air inlet port into the ambient air duct. The ambient air inlet port may be located at an upper portion of the casing at position that is vertically higher than a position at which air is communicated from the ambient air duct into the back duct. The back duct may define a funnel insertion port into which an end portion of the funnel is inserted, and an inner diameter of the funnel insertion port may be greater than an outer diameter of the funnel. The back duct may define a funnel insertion port into which an end portion of the funnel is inserted, and an inner circumferential surface of the funnel insertion port may be configured to make contact with an outer circumferential surface of the funnel. 
         [0016]    According to yet another aspect, a dryer includes a cabinet, a drum rotatably mounted within the cabinet, a first heater configured to generate hot air; a blower that allows the hot air generated by the first heater to be inhaled into the drum and the hot air from the drum to be exhausted, and a second heater configured to heat ambient air using heat energy from the hot air being exhausted by the blower. The ambient air heated by the second heater is mixed with hot air downstream of the first heater before being supplied to the drum. 
         [0017]    Implementations of this aspect may include one or more of the following features. For example, the ambient air may be inhaled through an additional flow path that is separate from a flow path for the hot air before being mixed with the hot air. The blower may include a blower fan. The second heater may include a waste heat recovery means. 
         [0018]    The details of one or more implementations described in this specification are set forth in the accompanying drawings and the description below. Other potential features and aspects of the present application will become apparent from the descriptions, the drawings and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a schematic view of an example dryer having a waste heat recovery device. 
           [0020]      FIG. 2  is a side view illustrating an internal structure of the dryer of  FIG. 1 . 
           [0021]      FIG. 3  is a perspective view illustrating a rear surface side of a drum in the dryer of  FIG. 1 . 
           [0022]      FIG. 4  is a perspective view illustrating a waste heat recovery device provided in the dryer of  FIG. 1 . 
           [0023]      FIG. 5  is a cross-sectional view along line A-A′ in  FIG. 4 . 
           [0024]      FIG. 6  is an enlarged cross-sectional view illustrating a pulsating heat pipe (PHP) provided in the dryer of  FIG. 1 . 
           [0025]      FIG. 7  is a schematic view of another example dryer having a waste heat recovery device. 
           [0026]      FIG. 8  is a schematic view of yet another example dryer having a waste heat recovery device. 
       
    
    
       [0027]    Like reference symbols in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0028]      FIG. 1  illustrates a dryer having a waste heat recovery device according to a first implementation of the present disclosure, and  FIG. 2  illustrates an internal structure of the first implementation.  FIG. 3  illustrates a rear surface side of a drum in the first implementation. Referring to  FIGS. 1 through 3 , the first implementation of a dryer  100  may include a cabinet  102  having a substantially rectangular parallelepiped shape, and a drum  104  for putting the laundry which is a drying object thereinto is rotatably mounted within the cabinet  102 . 
         [0029]    An air supply opening  104   a  is configured to supply hot air for drying the laundry, and the supplied hot air is passed through an inner portion of the drum and exhausted to a lint filter installation unit  106  connected to a lower end of the front surface portion. A lint filter for collecting foreign substances such as lint or the like separated from the laundry is mounted within the lint filter installation unit  106  and can be formed with a flow path (or a passage) for moving the exhausted hot air. 
         [0030]    Here, a funnel  112  for collecting hot air generated by a gas heater, which will be described later, is provided at a lower portion of the drum  104 , and an end portion of the funnel  112  is connected to a back duct  114 . 
         [0031]    The back duct  114  is located on a rear surface of the drum  104 , and performs the role of transferring hot air discharged from the funnel  112  to the air supply opening  104   a  of the drum  104 . The funnel  112  and the back duct  114  function as an intake duct  110  for guiding the air existing within the cabinet into the drum. Furthermore, a funnel insertion port  114   c  into which an end portion of the funnel is inserted is formed on the back duct  114 . An inner diameter of the funnel insertion port  114   c  is greater than an outer diameter of the funnel  112 , and therefore, it is configured such that air within the cabinet can be inhaled into the back duct  114  through a gap between an outer circumferential portion of the funnel  112  and an inner circumferential portion of the funnel insertion port  114   c.    
         [0032]    Here, the intake duct  110  may include the funnel  112  and the back duct  114 , but may not be necessarily limited to this configuration. For example, the funnel  112  and the back duct  114  may be integrally formed, or a separate duct may be additionally provided within the intake duct  110 . An exhaust portion  114   a  of the back duct  114  is disposed to face the air supply opening  104   a.    
         [0033]    A blower fan  108  for causing the flow of air is provided at the exhaust side of the lint filter installation unit  106 , and an exhaust duct  120  for discharging air exhausted from the drum to an outside of the cabinet  102  is provided at a rear side of the blower fan  108 . 
         [0034]    Furthermore, a gas heater is located on a front surface of the funnel  112 . The gas heater may include a gas nozzle  122  for spraying gas and a mixing pipe  124  for mixing gas sprayed from the gas nozzle and air. Referring to  FIG. 2 , a supporting bracket  126  for supporting the gas nozzle and mixing pipe can be provided on a bottom surface of the cabinet. 
         [0035]    When gas supplied through a gas pipe is sprayed through the gas nozzle and ignition is made, flame is generated from the mixing pipe  124  into the funnel  112 . As a result, air within the cabinet inhaled through the funnel  112  is heated by the flame and inhaled into the drum through the back duct  114 . 
         [0036]    On the other hand, air exhausted through the exhaust duct  120  contains higher temperature and humidity compared to the air around the cabinet, and thus has more heat energy. A waste heat recovery device  130  for collecting heat energy is located on a rear surface of the drum. Here, the waste heat recovery device  130  may be located out of the cabinet as illustrated in the drawing, or may be disposed within the cabinet. 
         [0037]    The waste heat recovery device  130  inhales and heats ambient air and then supplies the air to the back duct  114 . Thus, the ambient air is heated while passing through the waste heat recovery device  130 , and moves along an ambient air duct  140  disposed between the back duct  114  and the waste heat recovery device  130 . The ambient air duct  140  is formed such that ambient air is inhaled through the surrounding area of an upper end portion thereof and moves toward a lower side thereof. In some cases, the waste heat recovery device can be a heater. 
         [0038]    The ambient air duct  140  is communicated with the intake duct  110  between the drum  104  and heater. For example, the ambient air duct  140  is communicated with the back duct  114 . 
         [0039]    An ambient air outlet port  142  is disposed at a lower end portion of the ambient air duct  140  and faces an ambient air inlet port  114   b  formed at the back duct  114 . Accordingly, the heated ambient air is inhaled into the back duct  114  through the ambient air outlet port  142  and then mixed with hot air discharged from the funnel  112  before being supplied to the drum  104 . 
         [0040]    In some cases, the waste heat recovery device  130  may include a pulsating heat pipe (PHP)  132  (refer to  FIG. 4 ) and a casing  134  within which the PHP  132  can be accommodated. The casing  134  can have an extended rectangular parallelepiped shape, and can be positioned within the cabinet by a fixed bracket  150  (refer to  FIG. 3 ). An expansion pipe portion  136  having a substantially rectangular shaped cross-section for communicating with the exhaust duct  120  is disposed at a lower portion of the casing  134 . The expansion pipe portion  136  has a larger cross-sectional area compared to that of the exhaust duct  120 . With this structure, air exhausted from the exhaust duct  120  can be brought into contact with the PHP  132  over a larger area, than if the air contacted the PHP  132  directly from the exhaust duct  120 . An exhaust port  136   a  can be provided on one lateral surface of the expansion pipe portion  136 , and air is exhausted to an outside of the cabinet through the exhaust port  136   a.    
         [0041]    An ambient air inhalation port  138  for inhaling ambient air is formed at an upper portion of the casing  134 . The ambient air inhalation port  138  has an area capable of exposing all the condenser unit of the PHP  132  which will be described later, and aligned with respect to an ambient air inlet port  144  provided in the ambient air duct  140 . Accordingly, ambient air is inhaled to the ambient air duct  140  through the ambient air inhalation port  138  and the ambient air inlet port  144 , and heated while being brought into contact with the PHP  132  during the process. 
         [0042]    The back duct  114  and the ambient air duct  140  comprise communication ports  114   b,    142  disposed to face each other, respectively, and the communication ports are disposed at a location lower than that of the ambient air inlet inhalation port  138 . 
         [0043]    The back duct  114  can be mounted on a rear supporter  104   b  that supports a rear surface of the drum  104 , and an upper end portion thereof can have a fan shape to minimize flow resistance applied to hot air flowing into the drum  104 . Furthermore, the back duct  114 , the ambient air duct  140 , and casing  134  are fixed in a state where they are brought into contact with each other. As a result, heat energy transferred from the back duct  114  can be transferred to ambient air passing through the ambient air duct  140 , thereby minimizing thermal loss from the back duct  114 . 
         [0044]    Referring to  FIG. 4 , a plurality of the PHPs  132  are disposed according to the flow direction of air being exhausted. For example, the plurality of PHPs  132  are disposed within the casing  134  to be extended in a vertical direction. The PHP  132  generally has a tube shape, and a heat transfer medium is sealed therein. The plurality of PHPs  132  can be disposed to form total three columns as illustrated in  FIG. 5 . Of course, the configuration of PHPs  132  may not be necessarily limited to three columns, and may be also disposed to form one or any number of columns. 
         [0045]    As illustrated in  FIG. 5 , positions of the PHPs  132  may be staggered relative to each other to maximize the amount of exhausted hot air or inhaled ambient air that is brought into contact with the PHPs  132 . 
         [0046]    Referring to  FIG. 6 , the PHP  132  may include an evaporation unit  132   a  located within the expansion pipe portion  136  and a condenser unit  132   b  exposed through the ambient air inhalation port  138 . The evaporation unit  132   a  absorbs heat energy contained in the exhausted air to evaporate the heat transfer medium sealed therein. The evaporated heat transfer medium rises up and moves to the condenser unit  132   b,  where the heat transfer medium condenses while transferring heat to ambient air and moves again to the evaporation unit  132   a . Here, in order to enhance heat transfer efficiency, a plurality of fins  132   c  may be formed on a portion of the PHP  132  corresponding to the condenser unit  132   b.  In some cases, such fins may not be formed on a portion of the PHP  132  corresponding to the evaporation unit  132   a.    
         [0047]    A small amount of lint or foreign substances may be contained in the exhausted air, and thus when fins are formed on portions corresponding to the evaporation unit  132   a,  the lint or the like may be caught in the fins to obstruct the flow of air and heat transfer. However, in some cases, the fins may be also formed on portions corresponding to the evaporation unit  132   a  by establishing the spacing between such fins to be greater than those of fins that are on portions corresponding to the condenser unit  132   b.    
         [0048]    Therefore, at least some of the PHPs  132  is formed with the plurality of fins  132   c  for expanding their surface area on a portion corresponding to the condenser unit  132   b.  The fins  132   c  may be not formed on at least part of a portion corresponding to the evaporator of the PHPs  132 . 
         [0049]    The PHP transports latent heat contained in working fluid due to the vibration of working fluid generated between the evaporation unit and condenser unit to transfer heat. Accordingly, there is no wick for flowing liquid that has been condensed in the condenser unit back to the evaporation unit, thereby resulting in a simple structure and allowing various types of fabrication. Here, the PHP may have a tube shape as illustrated in the drawing and, in some cases, can have an internally partitioned flat tube shape. 
         [0050]    Hereinafter, an exemplary operation of the first implementation will be described. 
         [0051]    During the drying process, air is moved along the intake duct and exhaust duct by a blower fan. The air within the cabinet that is inhaled into the intake duct, particularly the funnel, is heated by the gas heater to temperatures of about 700-800° C. The hot air is inhaled into the back duct, mixed with air within the cabinet inhaled through a gap between the funnel insertion port and the funnel, and cooled to be within a predetermined temperature range. At the same time, ambient air is also inhaled into the waste heat recovery device by the blower fan. The inhaled ambient air is heated while passing through the condenser unit, after which it moves along the ambient air duct and is subsequently supplied to the back duct. 
         [0052]    Accordingly, the hot and ambient air are mixed within the back duct, and as a result, hot air having a temperature of approximately 250° C. is supplied into the drum. When a gas heater is used, air at normal temperature should be mixed with the hot air to cool the air to a suitable temperature since the temperature of the hot air is high as described above. According to the foregoing implementation, the air being supplied for cooling has a temperature higher than the normal temperature, thereby reducing the amount of gas supplied to the gas heater. 
         [0053]    Furthermore, the supplied ambient air is supplied through an additional flow path (or an additional passage) separated from the intake duct before being mixed. Therefore, the intake duct is not affected even when foreign substances have accumulated in the condenser unit; as such, the dryer is able to constantly maintain the drying performance even if used for a long period of time. 
         [0054]    According to the first implementation, the funnel insertion port and an outer circumferential portion of the funnel are separated from each other. However, in another implementation, an inner circumferential surface of the funnel insertion port  114   c ′ may be brought into contact with an outer circumferential surface of the funnel as illustrated in  FIG. 7 . In this case, the cooling of the hot air is entirely carried out by ambient air, thereby further reducing the amount of used gas. 
         [0055]    Furthermore, the present disclosure may not be necessarily limited to a case where the gas heater is used, and may be also applicable to a case where an electric heater is used. For example, as illustrated in  FIG. 8 , an electric heater  122 ′ may be provided in the intake duct instead of the gas heater. Here, in case of an electric heater, the temperature of the generated hot air can be freely adjusted, and thus the cooling of hot air as in the gas heater may not be required. Accordingly, as illustrated in the implementation shown in  FIG. 7 , an inner circumferential surface of the funnel insertion port  114   c ′ can be brought into contact with an outer circumferential surface of the funnel. 
         [0056]    Here, ambient air heated by a waste heat recovery device has a temperature lower than that of the electric heater and thus the temperature of hot air mixed in the back duct is lower than that of hot air immediately subsequent to passing through the electric heater. Accordingly, the temperature of hot air that has passed through the electric heater is set to be higher than 250° C., which is a temperature of hot air supplied to the drum. 
         [0057]    When an electric heater is used, a heat pump may be provided at the same time. In other words, a condenser of the heat pump may be provided at a front end of the intake duct to heat air in advance and then selectively heat the air using the electric heater. In this case, the heated ambient air may flow between the condenser and the electric heater or flow to a downstream side of the heater. 
         [0058]    It will be apparent to those skilled in the art that this application is not intended to be limited to the above-described implementations and drawings, and various changes or modifications may be made therein without departing from the scope and the technical sprit of this application.