Patent Publication Number: US-2009224414-A1

Title: Evaporative humidifier

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an evaporative humidifier, and more particularly, to an evaporative humidifier which is installed to control temperature and humidity in a precision equipment factory such as a clean room. 
     2. Description of the Related Art 
     In the precision equipment factory such as a clean room, it is necessary to keep the temperature and humidity constant. An evaporative humidifier as disclosed in Japanese Patent Application Laid-Open No. 2001-317795 is known as a humidifying apparatus for performing temperature and humidity control in such a room. 
     The evaporative humidifier includes a heating coil, an evaporative humidifier, a cooling coil, a fan, a dry-bulb temperature sensor, and a dew-point temperature sensor, which are disposed from an air inlet side to an air outlet side of an air flow path formed by a housing. 
     The evaporative humidifier is composed of a humidifying module in which water is allowed to flow along the surface of a humidifying element such that the surface gets wet by allowing water to seep to the top portion of the humidifying element from a water supply pipe. The evaporative humidifier performs humidification by controlling the heating coil and the cooling coil such that a dew point after humidification detected by the dew-point temperature sensor becomes constant. Also, in the heating coil and the cooling coil, heating and cooling amounts are proportionally controlled based on a dew-point temperature detected by the dew-point temperature sensor. 
       FIG. 6  shows a general configuration of a conventional evaporative humidifier. In the evaporative humidifier  1 , an air inlet  2 A is formed on the upstream side of an air flow path  2  that is formed by a housing, and an air outlet  2 B for air whose temperature and humidity are regulated is formed on the downstream side of the air flow path  2 . A heating/cooling coil  3 , a humidifying element  4 , and a dew-point meter  5  are disposed in the air flow path  2  from the upstream side to the downstream side thereof. The opening and closing of a control valve of the heating/cooling coil  3  is controlled based on the dew-point temperature detected by the dew-point meter  5 , so as to control the heating and cooling amounts. 
     Humidification amount control in the evaporative humidifier  1  is performed by controlling the temperature of inlet air flowing in from the air inlet  2 A by the heating/cooling coil  3 .  FIG. 7  shows a psychrometric chart showing a control method thereof. In  FIG. 7 , it is shown that the temperature of the inlet air is heated and the heated air humidified, so that the air is controlled to have a target humidity. 
     SUMMARY OF THE INVENTION 
     However, the method of controlling a humidification amount shown in  FIG. 7  has such a problem that when a humidifier to be attached to an outside air conditioner is assumed, the humidifier is very difficult to control in the intermediate season such as spring or autumn in which the humidity of air around the inlet is close to the target humidity since the evaporative humidifier  1  has only ON/OFF control. 
     That is, if the inlet humidity (initial value) is 40% when a targeted relative humidity is 50% as shown in  FIG. 8 , the humidifier is turned ON, and humidification is performed in large amounts. As a result, the humidity of outlet air largely exceeds 50%, and thus, the humidifier is turned OFF. Soon after a short period of time, the humidity around the dew-point meter returns to 40% that is the humidity of outside air, and the humidifier is turned ON again. As described above, in the intermediate season in which a difference between the target humidity and the humidity of outside air is small, the humidifier is alternately turned ON/OFF with frequency as shown in  FIG. 8 , and the humidifier is thereby unnecessarily operated, which is not preferable. 
     As a first solution to solve the problem, the sensor sensitivity of the control valve of the humidifier may be lowered. Accordingly, the humidifier is not turned ON even if the humidity is low to a certain extent, so that the humidity value is prevented from fluctuating up and down due to the ON/OFF control. 
     However, in the case of the first solution, once the humidifier is turned ON, humidification is performed in substantial amounts. Thus, the control cannot be considered as appropriate control. 
     On the other hand, as a second solution, a method of excessively heating the inlet air (outside air) more than normal first, humidifying the air, and subsequently, dehumidifying and cooling the humidified high-temperature air by the cooling coil, so as to control the air to have the target humidity may be employed as shown in a psychrometric chart in  FIG. 9 . According to the control method, there is such an advantage that accurate control is enabled since the control by cooling is easier than the control by heating and humidification. 
     However, the second solution has such a disadvantage that the running cost is increased since a great deal of energy is required for the excess heating. 
     The present invention has been made in view of such circumstances, and it is an object of the present invention to provide an evaporative humidifier capable of accurately performing humidity control without unnecessarily operating a humidifying device and without wasting energy. 
     In order to achieve the above object, the present invention provides an evaporative humidifier which humidifies air by allowing the air to pass through a humidifying element of a humidifying device, comprising: a plurality of humidifying modules which is formed by dividing the humidifying element via a partition member; a water supply device with a valve which is provided in each of the divided humidifying modules; and a control device which controls opening and closing of the valve with respect to each device. 
     In the present invention, a desired humidity is obtained by supplying water only to a humidifying module required for humidification. Air simply passes through a humidifying module to which water is not supplied. Accordingly, air obtained by mixing humidified air passing through the humidifying module which is wet with water being supplied thereto (wet zone) and non-humidified air passing through the humidifying module to which water is not supplied (dry zone) is blown out from an outlet of the evaporative humidifier. The mixture amount (mixture ratio) is controlled by the opening and closing of the valve, so that a desired humidity is obtained. Therefore, with the evaporative humidifier of the present invention, humidity control can be accurately performed without unnecessarily operating the humidifying device and without wasting energy. 
     Also, according to the present invention, the humidifying element is preferably formed into a rectangular shape in section so as to have the same thickness with respect to an air passing direction, or into a substantially triangular shape in section so as to have a gradually changing thickness with respect to the air passing direction. 
     With the present invention, by forming the humidifying element into the rectangular shape in section, the humidity proportionally rises or falls in accordance with the number of humidifying modules to which water is supplied. Also, by forming the humidifying element into the substantially triangular shape in section, the humidity rises or falls in a curve in accordance with the number of humidifying modules to which water is supplied. The humidifying elements are selected according to a humidity environment of outside air introduced into the evaporative humidifier. 
     Furthermore, according to the present invention, a dew-point detecting device which detects a dew point of the air passing through the humidifying device is preferably provided, wherein the control device controls the opening and closing of the valve with respect to each valve based on the dew point detected by the dew-point detecting device. 
     With the present invention, the control device feedback-controls the opening and closing of the valve with respect to each valve based on the dew point detected by the dew-point detecting device, so that a desired humidity can be obtained. 
     Moreover, the present invention preferably further comprises a heating/cooling device which heats/cools the air, wherein a heating amount by the heating/cooling device is controlled to obtain air having a desired temperature. 
     Accordingly, with the evaporative humidifier of the present invention, the air having a desired temperature and humidity can be supplied into a room. 
     As described above, according to the evaporative humidifier of the present invention, humidity control can be accurately performed without unnecessarily operating the humidifier and without wasting energy. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a configuration of an evaporative humidifier according to an embodiment; 
         FIG. 2  is a perspective view showing a configuration of a humidifying device according to a first embodiment; 
         FIG. 3  is a perspective view showing a configuration of a humidifying device according to a second embodiment; 
         FIG. 4  is a perspective view showing a configuration of a humidifying device according to a third embodiment; 
         FIG. 5  is a graph showing an increase in humidity relative to a degree of opening of a water supply electromagnetic valve; 
         FIG. 6  is a block diagram showing a general configuration of a conventional evaporative humidifier; 
         FIG. 7  is a psychrometric chart for explaining one example of a method of controlling a humidification amount in a conventional evaporative humidifier; 
         FIG. 8  is a view serially showing ON/OFF of a humidifier when a target humidity is 50%; and 
         FIG. 9  is a psychrometric chart for explaining one example of a method of controlling a humidification amount in a conventional evaporative humidifier. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, preferable embodiments of an evaporative humidifier according to the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a block diagram showing a configuration of an evaporative humidifier  10  according to an embodiment. 
     The evaporative humidifier  10  shown in  FIG. 1  includes a humidification flow path  12  formed by a housing case. An air inlet  14  for introducing outside air and an air outlet  16  for discharging conditioned air whose temperature and humidity are regulated into a room are formed at the ends of the humidification flow path  12 . A cooling/heating coil  18  is provided on the upstream side of the humidification flow path  12 . Air (outside air) flowing in the humidification flow path  12  is cooled or heated to a desired temperature by a cooling/heating medium supplied to the cooling/heating coil  18 . 
     A thermometer  20  is provided on the downstream side of the humidification flow path  12  from the cooling/heating coil  18 . The temperature of air passing through the cooling/heating coil  18  is measured by the thermometer  20 . The amount or temperature of the cooling/heating medium to be supplied to the cooling/heating coil  18  is feedback-controlled by an unillustrated control device based on the measured air temperature. A humidifying device  22  according to a first embodiment is provided on the downstream side of the humidification flow path  12  from the thermometer  20 . Also, a dew-point meter (dew-point detecting device)  24  is provided on the downstream side of the humidification flow path  12  from the humidifying device  22 . 
     A humidifying element  26  which constitutes the humidifying device  22  according to the first embodiment is disposed in a direction perpendicular to a flow direction A of the introduced outside air as shown in  FIG. 2 . The humidifying element  26  is formed into a rectangular shape in section along the outside air flow direction A, and has the same thickness over the entire area. Furthermore, the humidifying element  26  is divided in the vertical direction into four humidifying modules  26 A,  26 B,  26 C, and  26 D. The adjacent humidifying modules  26 A to  26 D are divided by separators (partition members)  28 , so that water does not enter from the adjacent humidifying modules  26 A to  26 D. The division number of the humidifying element  26  is not limited to four, and the humidifying element  26  may be divided into two or more humidifying modules. However, by dividing the humidifying element  26  into a plurality of humidifying modules, humidity control described below will be precisely performed. 
     A water supply unit  30  which constitutes the humidifying device  22  includes four nozzles  30 A,  30 B,  30 C, and  30 D which respectively supply water to the humidifying modules  26 A,  26 B,  26 C, and  26 D. The surfaces of the humidifying modules  26 A to  26 D get wet by allowing water to seep from the nozzles  30 A to  30 D, and air flowing in the humidification flow path  12  is allowed to pass through the humidifying modules  26 A to  26 D, so as to perform humidification. Extra water dropping from the humidifying modules  26 A to  26 D is collected in a drain pan  32  located below the humidifying element  26 . 
     In a water supply pipe  31  on which the nozzles  30 A to  30 D of the water supply unit  30  are provided, water supply electromagnetic valves (valves)  34 A,  34 B,  34 C, and  34 D are provided corresponding to the nozzles  30 A,  30 B,  30 C, and  30 D. That is, when the water supply electromagnetic valve  34 A on the upstream side is opened in response to water supply, water is supplied to the humidifying module  26 A from the nozzle  30 A. When the water supply electromagnetic valves  34 A and  34 B are opened, water is supplied to the humidifying modules  26 A and  26 B from the nozzles  30 A and  30 B. Similarly, when the water supply electromagnetic valves  34 A to  34 C are opened, water is supplied to the humidifying modules  26 A to  26 C from the nozzles  30 A to  30 C, and when the water supply electromagnetic valves  34 A to  34 D are opened, water is supplied to the humidifying modules  26 A to  26 D from the nozzles  30 A to  30 D. In other words, by controlling the opening and closing of the water supply electromagnetic valves  34 A to  34 D, the humidifying module to which water is to be supplied is selected from the humidifying modules  26 A to  26 D. Accordingly, the humidifying module which gets wet with water (wet zone) and the humidifying module to which water is not supplied (dry zone) are formed in one humidifying element  26 . 
     On the other hand, the opening and closing of the water supply electromagnetic valves  34 A to  34 D is controlled by a valve control unit  36  shown in  FIG. 1 . The valve control unit  36  controls the opening and closing of the water supply electromagnetic valves  34 A to  34 D such that a desired humidity is obtained based on a dew point detected by the dew-point meter  24 . 
     That is, in the evaporative humidifier  10  according to the embodiment, a desired humidity is obtained by supplying water only to the humidifying module required for humidification in the humidifying element  26 . Air simply passes through the humidifying module to which water is not supplied. Therefore, air obtained by mixing humidified air passing through the humidifying module which gets wet with water being supplied thereto (wet zone) and non-humidified air passing through the humidifying module to which water is not supplied (dry zone) is blown out from the outlet  16  of the evaporative humidifier  10 . The mixture amount (mixture ratio) is controlled by the opening and closing of the water supply electromagnetic valves  34 A to  34 D, so as to obtain a desired humidity. To be more specific, the valve control unit  36  feedback-controls the opening and closing of each of the water supply electromagnetic valves  34 A to  34 D based on the dew point detected by the dew-point meter  24 , so that a desired humidity can be obtained. 
     As described above, according to the evaporative humidifier  10  of the embodiment, the humidifying device  22  maintains a stable ON state to perform humidity regulation. Therefore, the humidifying device  22  is not unnecessarily operated in comparison with a humidifying device which is frequently turned ON/OFF as in a conventional case, and energy is not wasted since excess heating by the cooling/heating coil  18  is not required. Since the mixture ratio of the humidified air and non-humidified air is controlled to perform humidity regulation, humidity control can be accurately performed. 
     Also, according to the evaporative humidifier  10  of the embodiment, the amount or temperature of the cooling/heating medium to be supplied to the cooling/heating coil  18  is controlled by the unillustrated control device based on the air temperature measured by the thermometer  20  such that the air has a desired temperature. Accordingly, the air having a desired temperature and humidity can be supplied into a room according to the evaporative humidifier  10 . 
       FIG. 3  and  FIG. 4  respectively show a humidifying device  122  according to a second embodiment, and a humidifying device  222  according to a third embodiment. 
     Humidifying elements  126  and  226  of the humidifying devices  122  and  222  are formed into a substantially triangular shape in section so as to have a gradually changing thickness with respect to the air passing direction A. 
     The humidifying element  126  shown in  FIG. 3  is formed to become gradually thicker from the upstream side to the downstream side in a water supply direction. The humidifying element  226  shown in  FIG. 4  is formed to become gradually thinner from the upstream side to the downstream side in the water supply direction. 
     The humidifying element  126  shown in  FIG. 3  is divided in the vertical direction into three humidifying modules  126 A,  126 B, and  126 C. The adjacent humidifying modules  126 A to  126 C are divided by separators  128 . Also, the humidifying element  226  shown in  FIG. 4  is divided in the vertical direction into six humidifying modules  226 A,  226 B,  226 C,  226 D,  226 D,  226 E and  226 F. The adjacent humidifying modules  226 A to  226 F are divided by separators  228 . The division numbers of the humidifying elements  126  and  226  are not limited to the above numbers. 
     A water supply unit  130  of the humidifying device  122  in  FIG. 3  includes three water supply pipes  133  coupled to a main pipe  131 . A plurality of injection holes (not shown) are formed in the bottom portions of the water supply pipes  133  such that water is injected from the injection holes to the humidifying modules  126 A to  126 C. Also, a single water supply electromagnetic valve  134 A is provided at the base portion of the water supply pipes  133 . Water supply electromagnetic valves  134 B are respectively provided on the upstream sides of the water supply pipes  133 , and water supply electromagnetic valves  134 C are respectively provided on the downstream sides of the water supply pipes  133 . 
     Therefore, when the water supply electromagnetic valve  134 A is opened, water is injected from the injection holes formed in the respective water supply pipes  133  between the water supply electromagnetic valve  134 A and the respective water supply electromagnetic valves  134 B, and water is thereby supplied to the humidifying module  126 A of the humidifying element  122 . When the water supply electromagnetic valve  134 A and the respective water supply electromagnetic valves  134 B are opened, water is injected from the injection holes formed in the respective water supply pipes  133  between the water supply electromagnetic valve  134 A and the respective water supply electromagnetic valves  134 C, and water is thereby supplied to the humidifying modules  126 A and  126 B of the humidifying element  122 . Furthermore, when the water supply electromagnetic valve  134 A, the respective water supply electromagnetic valves  134 B and the respective water supply electromagnetic valves  134 C are opened, water is injected from the injection holes formed in all the water supply pipes  133 , and water is thereby supplied to the humidifying modules  126 A to  126 C of the humidifying element  122 . That is, by controlling the opening and closing of the water supply electromagnetic valves  134 A to  134 C, the humidifying module to which water is to be supplied is selected from the humidifying modules  126 A to  126 C. Accordingly, the humidifying module which gets wet with water (wet zone) and the humidifying module to which water is not supplied (dry zone) are formed in one humidifying element  126 . The opening and closing of the water supply electromagnetic valves  134 A to  134 C is controlled by a valve control unit (not shown in  FIG. 3 ) in a similar manner to  FIG. 1 . The valve control unit controls the opening and closing of the water supply electromagnetic valves  134 A to  134 C based on the dew point detected by the dew-point meter  24  such that a desired humidity is obtained in a similar manner to  FIG. 1 . In the humidifying device  122  according to the second embodiment, water is also supplied only to the humidifying module required for humidification in the humidifying element  126 , so as to obtain a desired humidity. 
     A water supply unit  230  of the humidifying device  222  in  FIG. 4  includes a conical pipe  231  having injection holes  231  A formed in its bottom portion. Water is injected from the injection holes  23 IA to the humidifying modules  226 A to  226 F. Also, water supply electromagnetic valves  234 A,  234 B,  234 C,  234 D,  234 E and  234 F are provided at predetermined intervals from the upstream side to the downstream side of the conical pipe  231 . The water supply electromagnetic valves  234 A to  234 F are located at positions corresponding to the humidifying modules  226 A to  226 F as described below. 
     That is, when the water supply electromagnetic valve  234 A is opened, water is injected from the injection holes  231 A formed in the conical pipe  231  between the water supply electromagnetic valve  234 A and the water supply electromagnetic valve  234 B, and water is thereby supplied to the humidifying module  226 A of the humidifying element  222 . When the water supply electromagnetic valves  234 A and  234 B are opened, water is injected from the injection holes  231 A between the water supply electromagnetic valve  234 A and the water supply electromagnetic valve  234 C, and water is thereby supplied to the humidifying modules  226 A and  226 B. Furthermore, when the water supply electromagnetic valves  234 A to  234 C are opened, water is injected from the injection holes  231 A between the water supply electromagnetic valve  234 A and the water supply electromagnetic valve  234 D, and water is thereby supplied to the humidifying modules  226 A to  226 C. Similarly, when the water supply electromagnetic valves  234 A to  234 D are opened, water is injected from the injection holes  231 A between the water supply electromagnetic valve  234 A and the water supply electromagnetic valve  234 E, and water is thereby supplied to the humidifying modules  226 A to  226 D, and when the water supply electromagnetic valves  234 A to  234 E are opened, water is injected from the injection holes  231 A between the water supply electromagnetic valve  234 A and the water supply electromagnetic valve  234 F, and water is thereby supplied to the humidifying modules  226 A to  226 E. Finally, when all the water supply electromagnetic valves  234 A to  234 F are opened, water is injected from all the injection holes  231 A of the conical pipe  231 , and water is thereby supplied to the humidifying modules  226 A to  226 F. 
     That is, by controlling the opening and closing of the water supply electromagnetic valves  234 A to  234 F, the humidifying module to which water is to be supplied is selected from the humidifying modules  226 A to  226 F. Accordingly, the humidifying module which gets wet with water (wet zone) and the humidifying module to which water is not supplied (dry zone) are formed in one humidifying element  226 . The opening and closing of the water supply electromagnetic valves  234 A to  234 F is controlled by a valve control unit (not shown in  FIG. 4 ) in a similar manner to  FIG. 1 . The valve control unit controls the opening and closing of the water supply electromagnetic valves  234 A to  234 F based on the dew point detected by the dew-point meter  24  such that a desired humidity is obtained in a similar manner to  FIG. 1 . In the humidifying device  222  according to the third embodiment, water is also supplied only to the humidifying module required for humidification in the humidifying element  226 , so as to obtain a desired humidity. 
     Next, a graph shown in  FIG. 5  will be described. 
     In the graph, the vertical axis represents a humidity around the outlet, and the horizontal axis represents a degree of opening of the water supply electromagnetic valve that is opened. To describe the degree of opening with reference to the humidifying element  26  including the four water supply electromagnetic valves  34 A to  34 D shown in  FIG. 2 , for example, the degree of opening is 25% when only the water supply electromagnetic valve  34 A is opened, 50% when the water supply electromagnetic valves  34 A and  34 B are opened, 75% when the water supply electromagnetic valves  34 A to  34 C are opened, and 100% when all the water supply electromagnetic valves  34 A to  34 D are opened. 
     The line A in the graph represents the humidifying element  26  shown in  FIG. 2 , the line B the humidifying element  126  shown in  FIG. 3 , and the line C the humidifying element  226  shown in  FIG. 4 . 
     Since the humidifying element  26  shown in  FIG. 2  has the uniform thickness, the degree of opening is directly reflected in a surface area ratio of the wet and non-wet humidifying modules, and the ratio is reflected as the humidity of the outlet. Therefore, the rate of humidity increase rises in proportion to the degree of opening in comparison with the humidifying elements  126  and  226  shown in  FIGS. 3 and 4 . 
     On the other hand, the increases in the humidifying elements  126  and  226  shown in  FIGS. 3 and 4  are changed in a curve as in the lines B and C due to a difference in the thickness of the humidifying module. For example, in the case of the humidifying element  126  in  FIG. 3 , when the degree of opening is small, a small amount of low-humidity air passing through the wet zone and a large amount of air passing through the dry zone are mixed, so that the air has a low humidity. As the degree of opening is larger, the thickness of the humidifying element  126  is larger, and the air has a higher humidity. In the case of the humidifying element  226  in  FIG. 4 , an effect opposite to that of the humidifying element  126  in  FIG. 3  is obtained. 
     In the case of the humidifying element  26  in  FIG. 2 , the humidity can be proportionally and gradually controlled by reducing the size of the evaporative humidifier. Also, since the amount of water used is decreased, the running cost can be also reduced. 
     Also, according to the humidifying elements  126  and  226  shown in  FIGS. 3 and 4 , the humidity can be proportionally and gradually controlled in a more compact and accurate manner than the humidifying element  26  in  FIG. 2 . The humidifying element  126  in  FIG. 3  is useful in a case where the evaporative humidifier is controlled in an environment in which outside air has a low humidity, and the humidifying element  226  in  FIG. 4  is useful in a case where the evaporative humidifier is controlled in an environment in which outside air has a high humidity.