JP3545315B2 - Air conditioner and humidity control method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an air conditioner using a vaporizing humidifier as a humidifier and a humidity control method.
[0002]
[Prior art]
In factories of the electronics and precision machinery industries, storage rooms for food preservation, animal breeding rooms for experiments, biological clean rooms, and the like, it is necessary to keep the indoor environment such as temperature and humidity constant. For this reason, in such equipment, an air conditioner for the purpose of maintaining a constant temperature and humidity in a room is installed.
[0003]
An example of such an air conditioner that has been conventionally proposed will be described below with reference to FIG. That is, in the figure, inside a housing 1 having an air intake port on the left side and an air supply port on the right side, a filter 2 for removing dust from outside air and a cooling coil 3 for cooling air by circulating cold water are provided from the air intake side. A heating coil 4 for heating the air by circulating hot water, a steam humidifier 5 for supplying steam generated by the boiler to the passage of the air to humidify the air, and a blower 6 for discharging the air outside the housing 1. ing. As the filter 2, for example, a medium-performance or HEPA filter is used.
[0004]
The cooling coil 3, the heating coil 4, and the steam humidifier 5 are provided with valves 7, 8, and 9 for controlling the flow rates of cold water, hot water, and steam, respectively. Further, a dew point temperature sensor 10a and a dry bulb temperature sensor 10b are attached to the humidified air supply port. These dew point temperature sensor 10a and dry bulb temperature sensor 10b are connected to a controller 10c. The controller 10c adjusts the valves 7, 9 based on the detected temperature from the dew point temperature sensor 10a so that the temperature and humidity of the supply air have a predetermined constant value, The steam humidifier 5 is configured to proportionally control the amount of steam. Further, the controller 10c adjusts the valves 7, 8 based on the temperature detected by the dry-bulb temperature sensor 10b so that the dry-bulb temperature of the supplied air becomes a predetermined constant value, and controls the cooling coil 3b. It is configured to proportionally control the amount of cold water inside and the amount of warm water inside the heating coil 4.
[0005]
The temperature and humidity control according to the prior art described above will be described below with reference to the psychrometric chart of FIG. 5 by taking the case where the set temperature on the indoor side is 23 ° C. and the set relative humidity is 45% as an example. . Note that Bw to Ew and Bs to Cs shown in FIG. 5 correspond to the state of air at the positions B to E shown in FIG.
[0006]
That is, when heating and humidification of air is required in winter or the like, the blower 6 is operated, and the valves 8 and 9 of the heating coil 4 and the steam humidifier 5 are opened. The outside air flowing from the air inlet (B point) of the housing 1 is heated by the heating coil 4 after the dust is filtered through the filter 2 (D point). As a result, the dry bulb temperature changes as shown by the solid line connecting Bw and Dw in FIG.
[0007]
Then, the heated air is humidified by the steam humidifier 5 (point E), and is supplied from the supply port by the blower 6. Since steam humidification involves heating, the dry bulb temperature and the relative humidity change as shown by the solid line connecting Dw and Ew in FIG.
[0008]
On the other hand, when the air needs to be dehumidified in summer or the like, the blower 6 is operated and the valve 7 of the cooling coil 3 is opened. Outside air flowing from the air inlet (point B) of the housing 1 is cooled by the cooling coil 3 after dust is filtered through the filter 2 (point C). As a result, the dry bulb temperature and the relative humidity change as shown by the dotted line connecting Bs and Cs in FIG. The cooled air is reheated by the heating coil 4 according to the indoor set temperature (point D), and is supplied from the supply port by the blower 6. This reheating is necessary to achieve constant temperature and constant humidity, for example, when the amount of generated indoor cooling load is small.
[0009]
[Problems to be solved by the invention]
By the way, in the case of humidification by the above-mentioned steam humidifier, a heat source of 100 ° C. or more is required, and energy cost is required because steam supplied from a boiler or the like is used. In addition, the steam humidifier requires a longer distance between the steam humidifier and the blower to increase the evaporation absorption distance until the steam is dispersed and absorbed by the flowing air. Becomes longer. Furthermore, in the above-mentioned conventional technology, the humidity control is performed by controlling the steam amount of the steam humidifier. However, the steam humidifier tends to cause unevenness due to local humidification, and the sensor is appropriately installed. It is difficult to determine the position, and it is difficult to make the downstream humidity uniform.
[0010]
To cope with this, a method using a vaporizing humidifier that can humidify using relatively low-temperature energy is considered. However, since humidification by a vaporizing humidifier involves a temperature drop, it is difficult to obtain a sufficient humidification amount and control accuracy by simply applying to the above-described conventional technology. It can be heated to a temperature at which a sufficient amount of humidification can be obtained even if the dry bulb temperature is lowered by humidification, and its application is limited to ON / OFF control where the accuracy of humidity does not matter much. For this reason, it has not been used when high-precision temperature and humidity control is required, such as in animal houses and semiconductor factories.
[0011]
The present invention has been proposed in order to solve the above-described problems of the related art, and its object is to reduce running cost, and to achieve high-precision control while suppressing increase in size. An object of the present invention is to provide an air conditioner and a humidity control method.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, an air conditioner according to the first aspect of the present invention provides a cooling water circulation type cooling coil for performing dehumidification and cooling in an air flow path between an air intake and an air supply port. A vaporizing humidifier, a first heating coil of a hot water circulation type disposed upstream thereof for enabling vaporization humidification by the vaporizing humidifier, and adjusting a dry bulb temperature of supply air. And a second heating coil of a hot water circulation type for performing the heating, wherein the first heating coil includes a plurality of coils, and the plurality of coils flow hot water in order from a preceding coil to a following coil. Communicated as such, the evaporative humidifier includes a plurality of stages of humidifiers, the plurality of stages of humidifiers are respectively disposed downstream of each of the plurality of coils, near the air supply port, A dew point sensor and a dry bulb temperature sensor are provided, and the dew point sensor is detected. A predetermined amount of dehumidification by controlling the flow rate of cold water of the cooling coil based on the value, and vaporizing humidification downstream of the first heating coil while controlling the flow rate of hot water based on the detection value of the dew point sensor. A predetermined amount of humidification by performing, and a predetermined amount of cooling by controlling the cooling water flow rate of the cooling coil based on the detection value of the dry bulb temperature sensor, and the above based on the detection value of the dry bulb temperature sensor A control device is provided that can selectively perform a predetermined amount of heating by controlling the flow rate of hot water in the second heating coil, and thereby keep the humidity and temperature of the supply air at predetermined predetermined values. It is characterized by having.
[0013]
According to a second aspect of the present invention, in the humidity control method of adjusting the temperature and humidity of the air introduced from the air inlet and supplying the air from the air supply port, the detection value of the dew point sensor disposed near the air supply port is adjusted. Based on a predetermined amount of dehumidification by controlling the flow rate of chilled water of a chilled water circulation type cooling coil based on the detected value of the dew point sensor, a first circulating type of hot water circulating type in which hot water flows in the order from front to rear in a multi-stage configuration . A predetermined amount of humidification by performing humidification by a plurality of vaporizing humidifiers disposed downstream of each stage of the first coil while controlling the flow rate of hot water of the heating coil, A predetermined amount of cooling by controlling the flow rate of the chilled water of the cooling coil based on the detection value of the dry bulb temperature sensor disposed near the supply port, and the vaporization based on the detection value of the dry bulb temperature sensor. Under humidifier A predetermined amount of heating by controlling the flow rate of hot water of a second heating coil of a hot water circulation type disposed on the side is selectively performed, so that the humidity and temperature of the supply air are set to a predetermined constant value. It is characterized by a value.
[0014]
According to the first and second aspects of the present invention, at the time of heating and humidifying in winter or the like, the air flowing in from the air intake is heated by the first heating coil, humidified by the vaporizing humidifier, and further cooled by the second heating coil. Is supplied from the air supply port after the heating by the heating coil is performed. At this time, the required amount of humidification can be achieved by controlling the flow rate of the hot water of the first heating coil based on the detection value of the dew point sensor. Therefore, humidification steam such as steam humidification becomes unnecessary, and for example , heating using low-temperature hot water of about 30 ° C. to 40 ° C., which can be stably obtained in large quantities from refrigerator cooling water , becomes possible. Therefore, running costs can be saved and energy savings can be realized. Since the vaporizing humidifier is installed in the entire air passage, it can humidify uniformly, and the humidification amount is controlled based on the detection value of the dew point sensor arranged near the air supply port. Since the control is performed by controlling the flow rate of the hot water of one heating coil, highly accurate humidity control based on the absolute humidity can be performed. Further, by performing heating by the first heating coil and humidification by the evaporative humidifier a plurality of times, it is possible to humidify to a target humidity while compensating for a temperature decrease due to the evaporative humidification. Further, since the evaporative absorption distance as in the case of steam humidification is not required, the size can be significantly reduced in the flow channel direction.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the air conditioner of the present invention will be specifically described with reference to the drawings. Note that the same members as those in the conventional technique shown in FIG.
[0016]
1. First embodiment 1-1. 1. Configuration First, a first embodiment of the present invention will be described with reference to FIGS. The present embodiment is an embodiment applied when the temperature of hot water used for heating is a low temperature of, for example, about 30 ° C. to 40 ° C. That is, inside the housing 1, the filter 2, the heating coil 40, the vaporizing humidifier 50, the cooling coil 3, the heating coil 60, and the blower 6 are arranged from the air intake side.
[0017]
The heating coil 40 is provided by being branched into two parts, a former coil 41 on the upstream side and a latter coil 42 on the downstream side. The two coils are connected so that hot water flows from the first coil 41 to the second coil 42 in this order. However, the hot water inlet side is set downwind so that the hot water flowing through the front-stage coil 41 and the rear-stage coil 42 has a counterflow to the air flow.
[0018]
The evaporative humidifier 50 has a two-stage configuration including a first humidifier 51 arranged downstream of the former coil 41 and a second humidifier 52 arranged downstream of the latter coil 42. The vaporizing humidifier 50 performs humidification by dropping water from a water supply pipe 50a and passing air through a humidifying module 50b having a wet surface. It is desirable that the vaporizing humidifiers 50 each have a saturation efficiency of about 80%, but it is also applicable to those having a saturation efficiency of less than this.
[0019]
The extra water dropped from each humidification module 50b is collected in a water tank 50c arranged at a lower part, and connected to a pipe so that the water is circulated and supplied to a water supply pipe 50a by a pump 50d. In addition, the inlet side of each of the cold water and the hot water is set downwind so that the cold water and the hot water flowing through the cooling coil 3 and the heating coil 60 flow counter to the air flow.
[0020]
The heating coil 40, the cooling coil 3 and the heating coil 60 as described above are provided with valves 80, 7, and 90 for controlling the flow rates of cold water and hot water, respectively. Further, a dew point temperature sensor 11 for detecting a dew point temperature of the supply air and a dry bulb temperature sensor 12 for detecting a dry bulb temperature of the supply air are attached to the supply port of the humidified air. The valves 80 and 7 and the dew point temperature sensor 11 are connected to a controller 11a. The valves 7, 90 and the dry bulb temperature sensor 12 are connected to a controller 12a.
[0021]
The controller 11a is configured to proportionally control the amount of hot water in the heating coil 40 based on the dew point temperature detected by the dew point temperature sensor 11. The controller 12 a is configured to proportionally control the amount of hot water in the heating coil 60 based on the dry-bulb temperature detected by the dry-bulb temperature sensor 12. The cooling coil 3 is configured to perform proportional control by the controllers 11a and 12a based on the detection values of the dew point temperature sensor 11 and the dry bulb temperature sensor 12, as in the related art.
[0022]
1-2. The operation of the present embodiment having the above-described configuration will be described with reference to the psychrometric chart of FIG. 2 in a case where the set temperature on the indoor side is 23 ° C. and the set relative humidity is 45%. The description will be made separately for heating and humidifying (mainly in winter) and cooling and dehumidifying (mainly in summer). Note that Bw to Fw and Bs to Gs shown in FIG. 2 correspond to the state of the air at the positions B to G shown in FIG. Also, specific values such as temperature and humidity are examples, and the present invention is not limited to these values. In addition, the temperature rise by the fan and the relative humidity decrease due to the fan are not considered here for easy understanding.
[0023]
1-2-1. When heating and humidification of air is required as in winter during heating and humidification, the blower 6 and the vaporizing humidifier 50 are operated, and the valve 80 of the heating coil 40 is opened. The air that has flowed in from the air inlet (point B) of the housing 1 is heated by the former-stage coil 41 after the dust is filtered through the filter 2 (point C). As a result, the dry bulb temperature changes as indicated by the solid line connecting Bw and Cw in FIG.
[0024]
The air heated by the former-stage coil 41 is humidified by the first humidifier 51 (point D). At this time, since the vaporization humidification involves a temperature decrease, the dry bulb temperature and the relative humidity change as shown by the solid line connecting Cw and Dw in FIG. The air humidified by the first humidifier 51 is heated by the subsequent coil 42 (point E). As a result, the dry bulb temperature changes as shown by the solid line connecting Dw and Ew in FIG.
[0025]
The air heated by the rear coil 42 is humidified by the second humidifier 52 (point F), and is supplied from the supply port by the blower 6. As a result, the dry bulb temperature and the relative humidity change as shown by the solid line connecting Ew and Fw in FIG.
[0026]
The vaporizing humidifiers 50 each have a saturation efficiency of 80%. The first stage humidification is performed after the first stage heating, and the second humidification is performed after the second stage heating. However, since the heating temperature is controlled by the outlet-side dew point temperature sensor 11, F in FIG. The air at the point may have a fixed absolute humidity predetermined value. Here, assuming that the inlet air dry-bulb temperature is t ₁ , the inlet air wet-bulb temperature is t _{1 ′} , and the outlet air dry-bulb temperature is t ₂ , the saturation efficiency ηs is expressed by the following equation 1.
[0027]
(Equation 1)
ηs = (t ₁ −t ₂ ) / (t ₁ −t _{1 ′} ) Equation 1
This is shown by applying specific numerical values in the example shown in FIG. 2, and the outlet air dry-bulb temperatures at points C to F change as follows.
Dw: (22−t ₂ ) / (22−9) = 0.8 Equation 2
Therefore, in the process from the point C to the point D, that is, Cw → Dw, t ₂ = 11.6 (° C.).
[Equation 3]
Fw: (18−t ₂ ) / (18−11.8) = 0.8 Equation 3
Therefore, t ₂ = 13.04 (° C.) from the point E to the point F, that is, from Ew to Fw.
[0028]
As described above, the dry bulb temperature is 22 ° C. at the point C, the dry bulb temperature is 11.6 ° C. at the point D, the dry bulb temperature is 18.0 ° C. at the point E, and the dry bulb temperature is 13.04 ° C. at the point F. , And in this process, the relative humidity and the absolute humidity increase. The temperature of the hot water flowing through the heating coil 40 is, for example, approximately 35 ° C. to 36 ° C. when the hot water flowing into the former coil 41 is about 30 ° C. to 29 ° C. after the heat exchange in the former coil 41. Thus, the above-described heating is performed.
[0029]
The flow rate of the hot water in the above-described heating coil 40 is determined based on the dew point temperature value detected by the dew point temperature sensor 11 installed at the supply port. (Relative humidity) is adjusted by the controller 12a by proportionally controlling the opening of the valve 80.
[0030]
If reheating is required in relation to the indoor set temperature, the valve 90 is opened and heating by the heating coil 60 is performed (point H). The flow rate of the hot water in the heating coil 60 is based on the dry-bulb temperature detected by the dry-bulb temperature sensor 12 installed in the air supply port, and the dry-bulb temperature of the supply air is an optimum value in relation to the indoor set temperature. Thus, the controller 12a is adjusted by proportionally controlling the valve 90.
[0031]
1-2-2. Next, when it is necessary to dehumidify air in summer or the like, the blower 6 is operated and the valve 7 of the cooling coil 3 is opened. After the dust flowing through the air inlet (B point) of the housing 1 is filtered through the filter 2, the air is cooled by the cooling coil 3 (G point) and supplied from the supply port by the blower 6. As a result, the dry bulb temperature and the relative humidity change as indicated by the dotted line connecting Bs and Gs in FIG. The flow rate of the chilled water in the cooling coil 3 is based on the dew point temperature sensor 11 and the dry bulb temperature sensor 12 installed at the supply port, and the absolute humidity of the supply air is set to the indoor set humidity (relative humidity) in relation to the indoor set temperature. The controller 11a, 12a adjusts the opening degree of the valve 7 by proportional control so that the value satisfies the following condition. If further heating is required in relation to the indoor set temperature, the valve 90 is opened and heating by the heating coil 60 is performed in the same manner as described above (point H).
[0032]
1-3. Effects The effects of the present embodiment as described above are as follows. That is, the high-temperature energy required for the steam humidifier is not required, so that the running cost can be significantly reduced. In particular, relatively low-temperature hot water used in the heating coils 40 and 60 can be stably obtained in large quantities from, for example, refrigerator cooling water, so that the energy consumption can be significantly reduced. And cost savings.
[0033]
Further, the amount of humidification by the vaporizing humidifier 50 capable of uniformly humidifying the entire air passage can be proportionally controlled by adjusting the flow rate of hot water of the heating coil 40 based on the dew point temperature. Humidity control becomes possible.
[0034]
Further, by performing heating by the heating coil 40 and humidification by the vaporizing humidifier 50 a plurality of times, it is possible to humidify to a target humidity while compensating for a temperature decrease due to the vaporizing humidification. By using the most downstream heating coil 60, the supply air can be set to the target temperature.
[0035]
Further, the present embodiment is provided with the plurality of heating coils 40 and 60 and the vaporizing humidifier 50. However, since the evaporative absorption distance as in the case of using the steam humidifier is unnecessary, the above-described conventional method is used. The size can be substantially the same as that of the technology, and the increase in size can be suppressed.
[0036]
2. Second embodiment 2-1. Configuration Next, a second embodiment of the present invention will be described below with reference to FIGS. This embodiment is an embodiment applied to a case where the temperature of hot water used for heating is, for example, a high temperature of 40 ° C. or higher. That is, in this embodiment, as shown in FIG. 3, the heating coil 40 'and the vaporizing humidifier 50' which are alternately arranged in the first embodiment are each one. , The length from the air intake to the air supply port is reduced. The other configuration is the same as that of the first embodiment.
[0037]
2-2. Operation The operation of the present embodiment as described above will be described under the same conditions as in the first embodiment. B'w to D'w and B's to E's shown in FIG. 2 correspond to the state of air at the positions B 'to E' shown in FIG. That is, when heating and humidification of air is required as in winter, the blower 6 and the vaporizing humidifier 50 are operated, and the valve 80 of the heating coil 40 'is opened. The air flowing from the air inlet (point B) of the housing 1 is heated by the heating coil 40 '(point C') after dust is filtered through the filter 2. As a result, the dry-bulb temperature changes as indicated by a dashed line connecting B'w and C'w in FIG.
[0038]
The air heated by the heating coil 40 'is humidified by a vaporizing humidifier 50' (point D '). At this time, since vaporization humidification involves a temperature decrease, the dry-bulb temperature and the relative humidity change as indicated by a dashed line connecting C'w and D'w in FIG. This is shown by applying a specific numerical example to Equation 1 above, and the outlet air dry-bulb temperature at points C ′ to D ′ changes as follows:
D′ w: (32−t ₂ ) / (32−13) = 0.8 Equation 4
Accordingly, in the process from the point C ′ to the point D ′, that is, C′w → D′ w, t ₂ = 16.8 (° C.). Other operations are the same as those in the first embodiment.
[0039]
2-3. According to the present embodiment as described above, it is assumed that high-temperature hot water is used. Therefore, even if the number of the heating coil 60 'and the number of the vaporizing humidifiers 50' are omitted, the above-described first embodiment is used. The same functions and effects as those of the embodiment can be obtained, and the overall length can be significantly reduced, so that a compact air conditioner can be configured.
[0040]
3. Other Embodiments The present invention is not limited to the above embodiments. For example, a method of performing heating and humidification with a heating coil and a vaporizing humidifier in three or more stages according to the capabilities of a heating coil and a vaporizing humidifier, the accuracy of hot water temperature, indoor temperature and humidity, and control temperature and humidity is considered. Can be In addition, the present invention can be applied not only to an air conditioner dedicated to outside air processing, but also to a circulating air conditioner that mixes and processes outside air and air from a room.
[0041]
In addition, replenishment of the humidifying water to the vaporizing humidifier does not necessarily have to be a circulation type. When vaporizing humidification is performed in general air conditioning, it is common to use city water in one pass while continuously draining 20 to 30% of the humidification amount. The supply source of the cold water to the cooling coil and the supply source of the hot water to the heating coil may be any.
[0042]
In addition, for example, if the humidifying modules of the vaporizing humidifier are of the lateral draw-out type, a maintenance space in the air circulation direction is not required, and the installation space length can be further reduced. Further, the type of the cooling coil or the heating coil is not limited as long as it is a heat exchanger for cooling or heating whose input heat quantity can be controlled.
[0043]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an air conditioner and a humidity control method capable of reducing running costs, suppressing an increase in size, and performing highly accurate control.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of an air conditioner of the present invention.
FIG. 2 is a psychrometric chart showing an example of temperature and humidity control according to the embodiment of FIGS. 1 and 3;
FIG. 3 is a configuration diagram showing a second embodiment of the air conditioner of the present invention.
FIG. 4 is a configuration diagram illustrating an example of a conventional air conditioner.
FIG. 5 is a psychrometric chart showing an example of temperature and humidity control according to the prior art of FIG. 4;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Housing 2 ... Filter 3 ... Cooling coil 4, 40, 40 ', 60 ... Heating coil 5 ... Steam humidifier 6 ... Blower 7, 8, 9, 80, 90 ... Valve 10a, 11 ... Dew point temperature sensor 10b, 12 Dry-bulb temperature sensors 10c, 11a, 12a Controller 41 Front-stage coil 42 Rear-stage coil 50, 50 'Vaporization humidifier 51 First humidifier 52 Second humidifier 50a Water pipe 50b Humidification Module 50c: water tank 50d: pump

Claims (2)

In the air flow path between the air inlet and the air supply port, a cooling coil of a chilled water circulation type for performing dehumidification and cooling, a vaporizing humidifier, and vaporizing humidification by the vaporizing humidifier are enabled. A first heating coil of a hot-water circulation type arranged upstream of the first heating coil, and a second heating coil of a hot-water circulation type for adjusting a dry-bulb temperature of supply air,
The first heating coil includes a multi-stage coil,
The coils of the plurality of stages are communicated so that hot water flows in order from the coil of the preceding stage to the coil of the subsequent stage,
The evaporative humidifier includes a multi-stage humidifier,
The plurality of stages of humidifiers are respectively disposed downstream of the plurality of stages of coils,
In the vicinity of the air supply port, a dew point sensor and a dry bulb temperature sensor are provided,
A predetermined amount of dehumidification by controlling the cold water flow rate of the cooling coil based on the detection value of the dew point sensor, and downstream of the first heating coil while controlling the hot water flow rate based on the detection value of the dew point sensor. A predetermined amount of humidification by performing vaporization humidification on the side, a predetermined amount of cooling by controlling the flow rate of cold water of the cooling coil based on a detection value of the dry bulb temperature sensor, and a detection of the dry bulb temperature sensor By selectively performing a predetermined amount of heating by controlling the flow rate of the hot water of the second heating coil based on the value, the humidity and temperature of the supply air can be set to predetermined constant values. An air conditioner characterized by providing a simple control device. In the humidity control method of adjusting the temperature and humidity of the air introduced from the air intake and supplying the air from the air supply port,
A predetermined amount of dehumidification by controlling the flow rate of the chilled water of the chilled water circulation type cooling coil based on a detection value of a dew point sensor disposed near the air supply port,
Based on the detection value of the dew point sensor, while controlling the hot water flow rate of the hot water circulation type first heating coil in which the hot water flows in the order from the front stage to the rear stage in a multi-stage configuration, each downstream of each stage of the first coil is controlled. A predetermined amount of humidification by performing humidification by a plurality of vaporization humidifiers disposed on the side,
A predetermined amount of cooling by controlling the cooling water flow rate of the cooling coil based on a detection value of a dry bulb temperature sensor disposed near the air supply port;
A predetermined amount of heating by controlling a hot water flow rate of a hot water circulation type second heating coil disposed downstream of the evaporative humidifier, based on a detection value of the dry bulb temperature sensor;
The humidity and temperature of the supply air are set to predetermined constant values by selectively performing the following.

Images