Air conditioning system for paint booth

Abstract

To provide an air conditioning system for a paint booth capable of operating with high stability while reducing energy consumption during reheating and dehumidification operation.SOLUTION: A first heat pump 51 supplies heat to a preheater 22 and a reheater 25, and supplies cold to a cooling coil 24. A second heat pump 52 is provided between the preheater 22 and the reheater 25, and performs heat recovery. A control device 53 operates the second heat pump 52 to supply heat recovered by the preheater 22 to the reheater 25, so that the preheater 22 functions as a cooler and the reheater 25 functions as a heater during reheating and dehumidification operation. The first heat pump 51 is operated so that the cooling shortage by the preheater 22 is compensated for by cooling the cooling coil 24.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an air conditioning system for a paint booth. [Background technology]

[0002] Generally, a painting facility is equipped with devices such as a painting booth for applying paint to objects such as automobile bodies, and a drying oven for drying the paint on the objects that have passed through the painting booth. In such painting facilities, air whose temperature and humidity have been adjusted by a paint booth air conditioner is sent into the paint booth to paint the objects. The paint booth air conditioner is composed of devices such as a preheater, a cooling coil, a washer, a reheater, and a blower fan, and these devices are operated in combination to control the conditioned air to a target temperature and humidity (see, for example, Patent Documents 1 and 2).

[0003] In recent years, there has been a demand to reduce the amount of carbon dioxide gas emitted from painting equipment. To address this, it has been proposed to use a heat pump in the air conditioner for the painting booth to recover heat and reduce energy consumption. For example, it is possible to recover heat by performing a reheat dehumidification operation in the summer, but depending on the conditions of the outside air, the balance between the amount of heat used for dehumidification by cooling and the amount of heat used for heating by reheating may not be achieved.

[0004] Under these circumstances, various innovative paint booth air conditioners have been proposed (see, for example, Patent Document 3). Patent Document 3 discloses a technique in which a heating heat exchanger and a cooling heat exchanger of a paint booth air conditioner are used as a condenser and an evaporator of a heat pump, respectively. In addition, a radiator is provided between the compressor and the condenser in this heat pump, and excess heat is released by this radiator, thereby balancing the amount of heat used for dehumidification by cooling and the amount of heat used for heating by reheating. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3993358 [Patent Document 2] JP 2010-119901 A [Patent Document 3] JP 2013-242119 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of the above-mentioned conventional technology, since the heat is released by a radiator, it cannot be said that the energy efficiency is good. Also, the operation of the heat recovery heat pump tends to become unstable.

[0007] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide an air conditioning system for a paint booth that can operate with high stability while reducing energy consumption during reheat dehumidification operation. [Means for solving the problem]

[0008] In order to solve the above problems, the invention described in Means 1 provides an air conditioner for a paint booth, which has a preheater, a cooling coil, and a reheater, and adjusts the temperature and humidity of air taken in from the outside using the preheater, the cooling coil, and the reheater, and sends the conditioned air to a paint booth; a first heat pump connected to the preheater, the reheater, and the cooling coil, and capable of supplying heat to the preheater and the reheater and supplying cold heat to the cooling coil; a second heat pump provided between the preheater and the reheater for heat recovery; and a system for connecting the air conditioner for a paint booth, the first heat pump, and the second heat pump. and a control device that controls the operation of the second heat pump to bring the conditioned air closer to a set temperature and humidity, wherein the control device operates the second heat pump to supply heat recovered by the preheater to the reheater so that the preheater functions as a cooler and the reheater functions as a heater in a reheat dehumidification operation in which air that has been once cooled and dehumidified to near the dew point of the set temperature and humidity is heated to reach the set temperature and humidity, and operates the first heat pump to make up for any shortage in cooling by the preheater with cooling by the cooling coil.

[0009] Therefore, according to the invention described in the means 1, when the second heat pump operates during the reheat dehumidification operation, the preheater functions as a cooler to cool the outdoor air, while the heat recovered by the preheater is supplied to the reheater. In addition, in the reheater functioning as a heater, the cooled outdoor air is reheated using the heat recovered by the preheater. When there is a shortage of cooling by the preheater, the first heat pump operates to supply cold heat to the cooling coil. As a result, the shortage of cooling is compensated for by the cooling of the cooling coil. Therefore, there is no need to waste heat during the reheat dehumidification operation, and it is possible to efficiently use thermal energy, thereby reducing energy consumption. In addition, it can be operated with high stability compared to conventional devices.

[0010] The invention described in Means 2 has the gist that in Means 1, a normal operation mode and a summer operation mode are preset, and the control device automatically changes the operation mode so that the air conditioner operates in the normal operation mode in winter, spring, and autumn, and performs the reheat dehumidification operation in the summer operation mode in summer.

[0011] Therefore, according to the invention described in Means 2, the operation mode is automatically changed to an appropriate one for each season without the user having to carry out the mode change operation, so that labor saving can be achieved.

[0012] The invention described in Means 3 is characterized in that in Means 2, a first temperature and humidity measuring means is provided for measuring the temperature and humidity of the outside air, and a second temperature and humidity measuring means is provided for measuring the temperature and humidity of the conditioned air, and the control device automatically changes the operating mode based on the result of comparing the set temperature and humidity of the conditioned air with the temperature and humidity of the outside air measured by the first temperature and humidity measuring means.

[0013] Therefore, according to the invention described in means 3, automatic change of operation mode is performed based on the results of comparing the set temperature and humidity of the conditioned air with the temperature and humidity of the outside air, so that the operation mode can be changed more appropriately.

[0014] The invention described in Means 4 is a feature of Means 3 in which the control device defines the enthalpy of air at a set temperature and humidity when a set temperature and humidity point is plotted at a position corresponding to the set temperature and humidity on a psychrometric chart as a first reference enthalpy, and defines a range in which the enthalpy is greater than the first reference enthalpy and the humidity is higher than the absolute humidity of the set temperature and humidity point as a heat recovery range in which the second heat pump can be operated to recover heat, and when it is determined that the temperature and humidity of the outside air is within the heat recovery range, the control device automatically changes from the normal operation mode to the summer operation mode to operate the second heat pump.

[0015] The invention described in Means 5 is characterized in that, in any one of Means 2 to 4, the control device, immediately after changing from the normal operation mode to the summer operation mode, switches the flow path so as to supply heat recovered by the pre-heater to a heat storage tank to store the heat, and after heat storage is completed, supplies hot water in the heat storage tank to the re-heater. Effect of the Invention

[0016] As described above in detail, according to the inventions recited in claims 1 to 5, it is possible to provide an air conditioning system for a paint booth that can operate with high stability while reducing energy consumption during reheat dehumidification operation. [Brief description of the drawings]

[0017] [Figure 1] 1 is a block diagram for explaining an air conditioning system for a paint booth according to an embodiment of the present invention; [Diagram 2] 4 is a psychrometric chart for explaining the operation of the above system. [Diagram 3] 4 is a psychrometric chart for explaining the operation of the above system. [Figure 4] 4 is a psychrometric chart for explaining the operation of the above system. [Diagram 5] 4 is a psychrometric chart for explaining the operation of the above system. [Figure 6] 4 is a psychrometric chart for explaining the operation of the above system. [Figure 7] 4 is a psychrometric chart for explaining the operation of the above system. [Figure 8] FIG. 4 is a block diagram for explaining an air conditioning system for a paint booth according to another embodiment. [Figure 9] FIG. 4 is a block diagram for explaining an air conditioning system for a paint booth according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, a paint booth air conditioning system 11 according to one embodiment of the present invention will be described in detail with reference to FIGS.

[0019] The paint booth air conditioning system 11 of this embodiment shown in FIG. 1 includes a paint booth air conditioner 21, a first heat pump 51, a second heat pump 52, a control device 53, and the like.

[0020] A paint booth (not shown), to which the conditioned air generated by the paint booth air conditioning system 11 is supplied, is generally installed in an area of ​​a paint workpiece transport line for applying paint to the workpiece. The paint booth comprises a paint chamber, an air supply chamber provided above the paint chamber for supplying air in a downflow (a fixed direction from above to below) to the paint chamber, and an exhaust chamber provided below the paint chamber for exhausting the air within the paint chamber. In the paint booth of this embodiment, conditioned air discharged from the paint booth air conditioner 21 is supplied into the paint chamber by a downflow from the air supply chamber.

[0021] In the coating chamber of the coating booth, paint is sprayed from a coating machine (not shown) to coat the object. At this time, paint mist that is oversprayed from the coating machine is exhausted from the coating chamber to an exhaust chamber by the downflow of conditioned air acting in the coating chamber. In the exhaust chamber, the paint mist contained in the air is captured using booth circulating water, and the paint is recovered. The air exhausted from the exhaust chamber is released into the atmosphere by a blower fan.

[0022] As shown in Fig. 1, the paint booth air conditioner 21 in this embodiment is configured to include multiple types of air conditioning equipment. This paint booth air conditioner 21 is a device for adjusting the air taken in from outside the device to a predetermined temperature (e.g., about 23°C) and a predetermined humidity (e.g., about 70% RH) and sending the air to the paint booth. More specifically, this paint booth air conditioner 21 is equipped with a preheater 22 which is a preheating device, a washer 23 which is a humidifying device, a cooling coil 24 which is a cooling device, a reheater 25 which is a reheating device, and a blower fan 26.

[0023] The preheater 22 is a type of temperature control means for adjusting the temperature of the taken-in air, and is a device for heating the air to preliminarily raise the temperature. The washer 23 is a type of humidity control means for adjusting the humidity of the taken-in air, and is a device for raising the humidity of the air by injecting water into the air that has passed through the preheater 22. The cooling coil 24 is a type of temperature control means for adjusting the temperature of the taken-in air, and is a cooling device for cooling the air that has passed through the washer 23 to lower the temperature. The reheater 25 is a type of temperature control means for adjusting the temperature of the taken-in air, and is a reheating device for reheating the air that has passed through the cooling coil 24 to raise the temperature. The blower fan 26 is an air compression device for compressing and sending the temperature- and humidity-controlled air (i.e., conditioned air) to the paint booth. That is, in the paint booth air conditioner 21 of this embodiment, the temperature and humidity of the air taken in from the outside are adjusted by the preheater 22, the washer 23, the cooling coil 24, and the reheater 25, and the conditioned air is sent to the paint booth.

[0024] A first temperature and humidity measuring means 61 (a first temperature sensor 63, a first humidity sensor 62) and a second temperature and humidity measuring means 66 (a second temperature sensor 68, a second humidity sensor 67) are provided at a plurality of locations in the paint booth air conditioner 21. Specifically, the paint booth air conditioner 21 is provided with a first temperature sensor 63, a first humidity sensor 62, a second temperature sensor 68, a second humidity sensor 67, and a third temperature sensor 69. The first temperature sensor 63 is a sensor that measures the temperature of the outside air before air conditioning, and is disposed near the outside air intake port of the paint booth air conditioner 21. The first humidity sensor 62 is a sensor that measures the humidity of the outside air before air conditioning, and is also disposed near the outside air intake port. The second temperature sensor 68 is a sensor that measures the temperature of the outside air (the conditioned air) after air conditioning, and is disposed on the outlet side of the blower fan 26 from which the conditioned air is sent out. The second humidity sensor 67 is a sensor that measures the humidity of the outside air (conditioned air) after air conditioning, and is also disposed on the outlet side of the blower fan 26. The third temperature sensor 69 is for measuring the temperature of the outside air that has passed through the preheater 22, and is disposed on the upstream side of the washer 23.

[0025] As shown in FIG. 1, the first heat pump 51 is connected to the preheater 22, the reheater 25, and the cooling coil 24, and is a device for supplying heat to the preheater 22 and the reheater 25 and supplying cold heat to the cooling coil 24. The first heat pump 51 of this embodiment is composed of a plurality of air-cooling heat pumps (not shown) connected in parallel. The air-cooling heat pump can switch between supplying hot water and supplying cold water. When supplying hot water, it takes heat from the atmosphere to heat the water and supplies hot water to the preheater 22 and the reheater 25. When supplying cold water, it takes heat from the water and dissipates it into the atmosphere, and supplies cold water to the cooling coil 24. In addition, by allocating some of the plurality of air-cooling heat pumps for cold water and the rest for hot water, it is also possible to simultaneously supply cold water and hot water. One of the secondary side ports of the first heat pump 51 is flow-connected to the first main flow path 35. The first main flow path 35 is divided into two branch flow paths, and each of the branch flow paths is flow-connected to the upstream side of the preheater 22 and the upstream side of the reheater 25. A first three-way valve 45 and a second three-way valve 46 are provided in each of these branch flow paths. The other of the ports on the secondary side of the first heat pump 51 is flow-connected to the upstream side of the cooling coil 24 via the second main flow path 36. Hot water can be supplied from the first heat pump 51 to the upstream side of the preheater 22 and the upstream side of the reheater 25 via the first main flow path 35. Cold water can be supplied from the first heat pump 51 to the upstream side of the cooling coil 24 via the second main flow path 36.

[0026] One of the ports on the primary side of the first heat pump 51 is flow-connected to the third main flow path 37. The third main flow path 37 is divided into two branch flow paths, and each of the branch flow paths is flow-connected to the downstream side of the preheater 22 and the downstream side of the reheater 25. Each of these branch flow paths is provided with a third three-way valve 41 and a fourth three-way valve 42. A first two-way valve 43 is provided between the third three-way valve 41 and the preheater 22, and a second two-way valve 44 is provided between the fourth three-way valve 42 and the preheater 22. The other of the ports on the primary side of the first heat pump 51 is flow-connected to the downstream side of the cooling coil 24 via the fourth main flow path 38. The hot water whose temperature has been reduced is returned to the first heat pump 51 from the downstream side of the preheater 22 and the downstream side of the reheater 25 via the third main flow path 37. Furthermore, cold water with an increased temperature is returned from the downstream side of the cooling coil 24 to the first heat pump 51 via the fourth main flow path .

[0027] A first bypass flow path 40 is connected between the first main flow path 35 and the third main flow path 37. A third two-way valve 48 is provided on the first bypass flow path 40. A second bypass flow path 39 is connected between the second main flow path 36 and the fourth main flow path 38. A fourth two-way valve 47 is provided on the second bypass flow path 39. The first bypass flow path 40 allows hot water to flow from the first main flow path 35 to the third main flow path 37, passing through the paint booth air conditioner 21. The first bypass flow path 39 allows cold water to flow from the second main flow path 36 to the fourth main flow path 38, passing through the paint booth air conditioner 21.

[0028] The first to fourth three-way valves 41, 42, 45, 46 and the first to fourth two-way valves 43, 44, 47, 48 are all motor valves that adjust the opening degree or switch the flow path by energizing a motor.

[0029] As shown in FIG. 1, the second heat pump 52 is a device provided between the preheater 22 and the reheater 25 to recover heat. Specifically, one of the ports on the primary side of the second heat pump 52 is flow-connected to one end of the first sub-channel 31. The other end of the first sub-channel 31 is flow-connected to the third three-way valve 41 on the branch channel of the third main channel 37. That is, the first sub-channel 31 and the third main channel 37 are joined via the third three-way valve 41. The other of the ports on the primary side of the second heat pump 52 is flow-connected to one end of the second sub-channel 33. The other end of the second sub-channel 33 is flow-connected to the first three-way valve 45 on the branch channel of the first main channel 35. That is, the second sub-channel 33 and the first main channel 35 are joined via the first three-way valve 45. Then, on the primary side of the second heat pump 52, the heat medium flowing out from one port is supplied to the preheater 22 via the second sub-channel 33 and the branch channel of the first main channel 35. The heat medium that has passed through the preheater 22 is returned to the other port on the primary side of the second heat pump 52 via the branch channel of the third main channel 37 and the first sub-channel 31.

[0030] One of the ports on the secondary side of the second heat pump 52 is flow-connected to one end of the fourth sub-channel 34. The other end of the fourth sub-channel 34 is flow-connected to the second three-way valve 46 on the branch channel of the first main channel 35. That is, the fourth sub-channel 34 and the first main channel 35 are joined via the second three-way valve 46. The other of the ports on the secondary side of the second heat pump 52 is flow-connected to one end of the third sub-channel 32. The other end of the third sub-channel 32 is flow-connected to the second three-way valve 42 on the branch channel of the third main channel 37. That is, the third sub-channel 32 and the first main channel 35 are joined via the second three-way valve 42. Therefore, on the secondary side of the second heat pump 52, the heat medium flowing out from one port is supplied to the reheater 25 via the fourth sub-channel 34 and the branch channel of the first main channel 35. The heat medium that has passed through the reheater 25 passes through the branch passage of the third main passage 37 and the third sub-passage 32 and is returned to the other port on the secondary side of the second heat pump 52 .

[0031] The control device 53 in this embodiment is a device for controlling the operation of the air conditioning equipment, the operation of each motor valve, and the operation of the first heat pump 51 and the second heat pump 52 to control the conditioned air to approach the set temperature and humidity. The control device 53 is composed of one or more well-known computers consisting of a CPU, storage means (ROM, RAM), etc. This control device 53 is equipped with an air supply target input unit, an air supply setting calculation unit, an equipment control unit, etc. The equipment control unit includes a PID controller that controls the operation amount of the air conditioning equipment by PID control. Note that a program for temperature and humidity control is stored in the storage means of the control device 53, and the CPU in the control device 53 is configured to read out the program from the storage means and execute it sequentially. In addition to this program, data on a psychrometric chart (psychrometric chart table) that shows the state value of the air on a coordinate system is stored in the storage means. Incidentally, the enthalpy increases toward the upper right of the psychrometric chart, and decreases toward the lower left.

[0032] PID control (Proportional-Integral-Differential Control) is a type of feedback control, and refers to control in which an input value is controlled by three elements: the deviation between an output value and a target value, and its integral and differential. The PID controller of this embodiment has PID loops in the same number as the number of controlled objects (specifically, four). The PID controller and each of the motor valves (the first to fourth three-way valves 41, 42, 45, 46 and the first to fourth two-way valves 43, 44, 47, 48) are electrically connected to each of the above-mentioned sensors 62, 63, 67, 68, 69 via driver circuits not shown. The PID controller and each of the above-mentioned sensors 62, 63, 67, 68, 69 are also electrically connected. Therefore, the PID controller outputs a drive control signal to each controlled object, and the operation amount of each air conditioning device is PID-controlled by this. As a result, the outside air temperature and humidity are adjusted to reach the target temperature and humidity. At that time, the measurement results of the temperature and humidity are input from each of the above-mentioned sensors 62, 63, 67, 68, 69. Therefore, the PID controller is capable of performing feedback control based on the measurement results.

[0033] The air supply target input unit is electrically connected to the equipment control unit via the air supply setting calculation unit. The air supply target input unit is used to input target values ​​for temperature and humidity of the conditioned air to be supplied to the painting booth, and is configured to include means such as a keyboard, a touch panel, etc. An output signal from the air supply target input unit is input to the air supply setting calculation unit.

[0034] The air supply setting calculation unit is electrically connected to the sensors 62, 63, 67, 68, and 69. Therefore, the measured values ​​of temperature and humidity output from the sensors 62, 63, 67, 68, and 69 are input to the air supply setting calculation unit. The air supply setting calculation unit performs a predetermined calculation based on the input target values ​​of temperature and humidity and the measured values, sets target values ​​of the operation amounts of each air conditioning device based on the calculation results, and outputs the target values ​​to the PID controller. The control device 53 is configured to automatically change the operation mode based on the measurement results of the first temperature and humidity measuring means 61 and the set values ​​of the air supply conditions (for example, the air volume value of the blower fan 26).

[0035] Next, the operation of the system 11 of this embodiment will be described with reference to the psychrometric charts of FIGS.

[0036] In this system 11, a normal operation mode and a summer operation mode are preset. The control device 53 automatically changes the operation mode so that the system operates in the normal operation mode in winter, spring, and fall, and performs reheat dehumidification operation in the summer operation mode in summer. For example, the control device 53 may constantly monitor the temperature and humidity of the surrounding outdoor air, and automatically change the operation mode based on the result of comparing the set temperature and humidity of the conditioned air with the outdoor air temperature and humidity, or may automatically change the operation mode using other methods (such as a method based on the calendar).

[0037] In the normal operation mode, the control device 53 basically operates only the first heat pump 51 and stops the second heat pump 52. At this time, the control device 53 controls the switching of the first to fourth three-way valves 41, 42, 45, 46 to block communication between the second sub-path 33 and the fourth sub-path 34 and the first main path 35, and to block communication between the first sub-path 31 and the third sub-path 32 and the third main path 37. Therefore, the first heat pump 51 can supply hot water to the pre-heater 22 and the re-heater 25, and cold water to the cooling coil 24.

[0038] The psychrometric chart in FIG. 2 shows the state when operating in the normal operation mode. In FIG. 2, the set temperature and humidity point P2 is plotted at a position corresponding to the set temperature and humidity (see △ in the figure), and the outdoor air temperature and humidity point P1 is plotted at a position corresponding to the outdoor air temperature and humidity at that time (see ◯ in the figure). FIG. 2 shows an example in which the outdoor air temperature is lower than the set temperature and humidity, and the outdoor air absolute humidity is lower than the set humidity. The control device 53 defines and stores the enthalpy of the air at the set temperature and humidity as the first reference enthalpy. In FIG. 2, the isoenthalpy line showing this first reference enthalpy is given the symbol E1, and the isoenthalpy line to which the outdoor air temperature and humidity point P1 belongs is given the symbol E0. When taking in outside air to obtain conditioned air, the control device 53 uses the preheater 22 to heat the taken-in outdoor air, thereby increasing the temperature of the taken-in outdoor air. That is, the state point is moved to the right in FIG. 2. When the temperature of the taken-in outside air reaches the isoenthalpy line E1, the control device 53 then uses the washer 23 to humidify the air, controlling it to approach the set temperature and humidity point P2. Note that the arrow R1 in Fig. 2 indicates the movement path of the state point.

[0039] FIG. 3 shows a psychrometric chart for the summer operation mode. In FIG. 3, an outdoor temperature and humidity point P1 is plotted at a position where the outdoor temperature is higher than the set temperature and the outdoor absolute humidity is higher than the set humidity (see the circle in the figure). FIG. 3 shows an isenthalpy line E1 to which the set temperature and humidity point P2 belongs, and an isenthalpy line E3 to which the outdoor temperature and humidity point P1 belongs. FIG. 3 also shows an isenthalpy line E2 to which the dew point P3 (reheat start point) of the set temperature and humidity belongs, that is, the point where the absolute humidity is equal to the set humidity and the temperature is lower than the set temperature. The enthalpy required for cooling is represented by ΔE32, and the enthalpy required for reheating is represented by ΔE12.

[0040] Fig. 4 shows a psychrometric chart in the summer operation mode like Fig. 3, but a first heat recovery range Z1 is added. The control device 53 defines and stores the range where the enthalpy is greater than the first reference enthalpy and the absolute humidity is higher than the set temperature and humidity point P2 as the first heat recovery range Z1 in which the second heat pump 52 can be operated to recover heat. When the control device 53 determines that the temperature and humidity of the outside air are within the first heat recovery range Z1, it automatically changes the operation mode from the normal operation mode to the summer operation mode.

[0041] In this case, the outside air taken in is once cooled to near the dew point P3 of the set temperature and humidity to be dehumidified, and then the air is heated to reach the set temperature and humidity, in a reheat dehumidification operation. The arrow R2 in FIG. 4 indicates the movement path of the state point when the reheat dehumidification operation is performed. In performing the reheat dehumidification operation, the control device 53 operates the second heat pump 52 in addition to the first heat pump 51. Specifically, the control device 53 controls the switching of the first to fourth three-way valves 41, 42, 45, and 46 to communicate between the second sub-path 33 and the fourth sub-path 34 and the branch path of the first main path 35, and to block communication with the first main path 35. In addition, the control device 53 communicates between the first sub-path 31 and the third sub-path 32 and the branch path of the third main path 37, and to block communication with the third main path 37. Therefore, the first heat pump 51 is able to supply cold water to the cooling coil 24, while hot water is no longer supplied to the preheater 22 and the reheater 25. In addition, the second heat pump 52 supplies cold water to the preheater 22 and hot water to the reheater 25. In other words, the control device 53 operates the second heat pump 52 to supply heat recovered by the preheater 22 to the reheater 25, so that the preheater 22 functions as a cooler and the reheater 25 functions as a heater.

[0042] In the psychrometric chart for the summer operation mode shown in FIG. 4, the enthalpy of the heat cooled by the preheater 22 is represented by ΔE34, and the enthalpy required for reheating by the reheater 25 is represented by ΔE12. These two enthalpies ΔE34 and ΔE12 are equal. As explained above, when comparing the enthalpy ΔE32 that needs to be cooled with the enthalpy ΔE34 of the heat cooled by the preheater 22, it is found that ΔE32 is larger. Therefore, the cooling by the preheater 22 alone is insufficient. In this case, the first heat pump 51 is operated so that the shortage of cooling by the preheater 22 (ΔE32-ΔE34=ΔE42) is compensated for by cooling by the supply of cold water from the cooling coil 24.

[0043] FIG. 5 shows a psychrometric chart in the summer operation mode, as in FIG. 3 and FIG. 4, but a second heat recovery possible range Z2 is added. The control device 53 defines and stores the right-angled triangular range below the first heat recovery possible range Z1 in the psychrometric chart shown in FIG. 5 as the second heat recovery possible range Z2. The second heat recovery possible range Z2 indicates a range in which the enthalpy is somewhat larger than the first reference enthalpy and the temperature is higher than the set temperature and humidity point P2. The second heat recovery possible range Z2 is also a range in which the second heat pump 52 can be operated to recover heat, similar to the first heat recovery possible range Z1. The control device 53 is also configured to automatically change the normal operation mode to the summer operation mode when it is determined that the temperature and humidity of the outside air are within the second heat recovery possible range Z2.

[0044] In this case, the outside air taken in is cooled to near the dew point P3 of the set temperature and humidity, and then the air is heated to reach the set temperature and humidity in a reheat dehumidification operation. However, before cooling, the air is humidified by the washer 23, so that the state point moves along the isoenthalpy line E5. The arrow R3 in Fig. 5 indicates the path of movement of the state point when the reheat dehumidification operation is performed.

[0045] Therefore, according to this embodiment, the following effects can be obtained.

[0046] (1) In the paint booth air conditioning system 11 of this embodiment, when the second heat pump 52 operates during reheat dehumidification operation, the preheater 22 functions as a cooler to cool the outside air, while the heat recovered by the preheater 22 is supplied to the reheater 25. In addition, in the reheater 25 functioning as a heater, the cooled outside air is reheated using the heat recovered by the preheater 22. When there is a shortage of cooling by the preheater 22, the first heat pump 51 operates to supply cold heat to the cooling coil 24. As a result, the shortage of cooling is compensated for by the cooling of the cooling coil 24. Therefore, there is no need to waste heat during reheat dehumidification operation, and it is possible to efficiently use thermal energy, thereby reducing energy consumption.

[0047] In addition, in this embodiment, the cooling coil 24 serves as a cooling device that backs up the preheater 22 that functions as a cooler. Therefore, there is no need to consider the heat balance for the second heat pump 52 alone, making it possible to provide a system that is easy to apply. In addition, in this embodiment, the operating range of the second heat pump 52 is set in advance, making it possible to provide the system 11 that can operate more stably than conventional devices.

[0048] (2) In the paint booth air conditioning system 11 of this embodiment, a normal operation mode and a summer operation mode are preset. The control device 53 automatically changes the operation mode so that the system operates in the normal operation mode in winter, spring, and autumn, and performs reheat dehumidification operation in the summer operation mode in summer. Therefore, even if the user does not perform the mode change operation himself, the operation mode is automatically changed to an appropriate mode for each season, which can reduce labor.

[0049] (3) The paint booth air conditioning system 11 of this embodiment includes a first temperature and humidity measuring means 61 that measures the temperature and humidity of the outside air, and a second temperature and humidity measuring means 62 that measures the temperature and humidity of the conditioned air. The control device 53 automatically changes the operation mode based on the result of comparing the set temperature and humidity of the conditioned air with the temperature and humidity of the outside air measured by the first temperature and humidity measuring means 61. Therefore, the operation mode can be changed more appropriately according to the change in the temperature and humidity of the outside air at that time.

[0050] (4) A modification of the paint booth air conditioning system 11 of this embodiment will be described below. FIG. 6 shows a psychrometric chart in the summer operation mode. The second heat pump 52 has a compressor (not shown) inside, and when the second heat pump 52 is operating, the compressor generates heat by energization. Thus, the heat medium is heated when passing through the compressor. For this reason, when operating this system 11, it is desirable to take into account the heating by the compressor from the viewpoint of improving control accuracy and energy efficiency. The control device 53 defines and stores an enthalpy that is shifted downward from the first reference enthalpy in consideration of the heating by the compressor of the second heat pump 52 as the second reference enthalpy. The control device 53 defines and stores a range between the first reference enthalpy and the second reference enthalpy, which is higher in humidity than the absolute humidity of the set temperature and humidity point P2, as the first heat recovery expansion range Z1a in which the second heat pump 52 can be operated to recover heat. 6, the first heat recovery expansion range Z1a is adjacent to the lower left end of the first heat recovery range Z1, and is distinguished from the first heat recovery range Z1 by adding a different hatching. When the control device 53 determines that the temperature and humidity of the outside air is within the first heat recovery range Z1 or the first heat recovery expansion range Z1a, it automatically changes the operation mode from the normal operation mode to the summer operation mode and operates the second heat pump 52.

[0051] FIG. 7 shows a psychrometric chart in the summer operation mode, similar to FIG. 6. The control device 53 defines and stores the area adjacent to the second heat recovery possible range Z2 as the second heat recovery possible extended range Z2a in which heat recovery can be performed by operating the second heat pump 52. In FIG. 7, the second heat recovery possible extended range Z2a is adjacent to the second heat recovery possible range Z2, and is distinguished from the second heat recovery possible range Z2 by adding hatching different from that of the second heat recovery possible range Z2. The control device 53 also automatically changes the normal operation mode to the summer operation mode and operates the second heat pump 52 when it determines that the temperature and humidity of the outdoor air are within the second heat recovery possible range Z2 or the second heat recovery possible extended range Z2a. Therefore, according to the system 11 of this modified example, the heat generated by the second heat pump 52 itself is effectively utilized, so that the energy consumption required for air conditioning can be further reduced.

[0052] Each embodiment of the present invention may be modified as follows.

[0053] For example, a warm-up operation may be performed by configuring the paint booth air conditioning system 11A of another embodiment shown in FIG. 8. In this system 11A, a buffer tank 71 (heat storage tank) is provided in the third sub-path 32. In addition, a third bypass path 72 is provided between the third sub-path 32 and the fourth sub-path 34, and a fifth two-way valve 73 is provided on the third bypass path 72. In this system 11A, the control device 53 does not immediately control the supply of heat recovered by the preheater 22 to the reheater 25 immediately after changing from the normal operation mode to the summer operation mode. At this time, the control device 53 blocks the path that supplies hot water from the fourth sub-path 34 to the reheater 25, while opening the fifth two-way valve 73 on the third bypass path 72 to circulate hot water to the buffer tank 71. In other words, the heat recovered by the preheater 22 is supplied to the buffer tank 71 to store heat in advance. After the heat storage is completed, the control device 35 blocks the third bypass flow path 72 and opens the flow path that supplies hot water from the fourth sub-flow path 34 to the reheater 25. As a result, the hot water in the buffer tank 71 that has become sufficiently hot can be supplied to the reheater 25 immediately after the flow path is switched.

[0054] For example, the paint booth air conditioning system 11B may be configured as another embodiment shown in FIG. 9. In this system 11B, the installation position of the second heat pump 52 is different from that of the above embodiment. That is, the second heat pump 52 is connected to the first main flow path 35 through a flow path 87 and is connected to the second main flow path 36 through a flow path 86. A buffer tank 83 is provided on the third main flow path 37, and the buffer tank 83 is connected to the second heat pump 52 through a flow path 85. A buffer tank 82 is provided on the fourth main flow path 38, and the buffer tank 82 is connected to the second heat pump 52 through a flow path 84. Therefore, in this system 11B, the hot water from the second heat pump 52 is supplied to the preheater 22 and the reheater 25. The hot water discharged from the preheater 22 and the reheater 25 is temporarily stored in the buffer tank 83 and then returned to the second heat pump 52. Furthermore, cold water from the second heat pump 52 is supplied to the cooling coil 24. The cold water discharged from the cooling coil 24 is temporarily stored in a buffer tank 82 and then returned to the second heat pump 52. For example, if there is a shortage of heating by the second heat pump 52 due to a problem or the like, control is performed so that hot water is also supplied from the first heat pump 51 by switching the flow path. That is, according to this configuration, it becomes possible for the first heat pump 51 to back up the shortage of heating by the second heat pump 52.

[0055] In the above embodiment, the control device 53 is configured to automatically switch between the normal operation mode and the summer operation mode that are set in advance based on a predetermined condition, but the present invention is not limited to this. For example, the user may switch between the normal operation mode and the summer operation mode by himself / herself.

[0056] In the above embodiment, the paint booth air conditioner 21 includes the preheater 22, the washer 23, the cooling coil 24, the reheater 25, and the blower fan 26, but is not limited to this. For example, the paint booth air conditioner 21 may include the preheater 22, the cooling coil 24, the reheater 25, and the blower fan 26, but may not include the washer 23.

[0057] Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-mentioned embodiments will be listed below.

[0058] (1) In the above-mentioned means 3, The second heat pump includes a compressor, The control device includes: The enthalpy of air at the set temperature and humidity when a set temperature and humidity point is plotted at a position corresponding to the set temperature and humidity on a psychrometric chart is defined as a first reference enthalpy; Taking into account the heating by the compressor of the second heat pump, an enthalpy shifted downward from the first reference enthalpy is defined as a second reference enthalpy; A range in which the enthalpy is greater than the first reference enthalpy and the humidity is higher than the absolute humidity of the set temperature and humidity point is defined as a heat recovery range in which the second heat pump can be operated to recover heat; A range between the first reference enthalpy and the second reference enthalpy and having a higher humidity than the humidity of the set temperature and humidity point is defined as a heat recovery expansion range in which the second heat pump can be operated to recover heat, When it is determined that the temperature and humidity of the outdoor air are within the heat recovery range or the heat recovery extended range, the normal operation mode is automatically changed to the summer operation mode, and the second heat pump is operated.

[0059] 11, 11A: Air conditioning system for paint booth 21: Paint booth air conditioner 22: Preheater 24: Cooling coil 25: Lehita 51: The first heat pump 52: Second heat pump 53: Control device 61: First temperature and humidity measuring means 66: Second temperature and humidity measuring means 71: Heat storage tank E1: Isoenthalpy line showing the first reference enthalpy P2: Set temperature and humidity point Z1: The first heat recovery range as the heat recovery range

Claims

1. an air conditioner for a paint booth, comprising a preheater, a cooling coil, and a reheater, and adjusting the temperature and humidity of air taken in from the outside by the preheater, the cooling coil, and the reheater, and supplying the conditioned air to the paint booth; a first heat pump connected to the preheater, the reheater, and the cooling coil, capable of supplying heat to the preheater and the reheater, and capable of supplying cold heat to the cooling coil; a second heat pump provided between the preheater and the reheater for recovering heat; a control device that controls the operation of the paint booth air conditioner, the first heat pump, and the second heat pump to bring the conditioned air closer to a set temperature and humidity; Equipped with The control device includes: In the reheat dehumidification operation, the air is first cooled to near the dew point of the set temperature and humidity, and then heated to reach the set temperature and humidity. operating the second heat pump to supply heat recovered by the preheater to the reheater so that the preheater functions as a cooler and the reheater functions as a heater; When there is a shortage of cooling by the preheater, the first heat pump is operated so as to make up for the shortage by cooling the cooling coil. An air conditioning system for a paint booth.

2. A normal operation mode and a summer operation mode are preset. The control device automatically changes the operation mode so that the normal operation mode is performed in winter, spring, and autumn, and the reheat dehumidification operation is performed in the summer operation mode in summer.

2. The paint booth air conditioning system according to claim 1.

3. The device includes a first temperature and humidity measuring means for measuring the temperature and humidity of the outside air, and a second temperature and humidity measuring means for measuring the temperature and humidity of the conditioned air, The control device automatically changes the operation mode based on a result of comparing the set temperature and humidity of the conditioned air with the temperature and humidity of the outside air measured by the first temperature and humidity measuring means.

3. The paint booth air conditioning system according to claim 2.

4. The control device includes: The enthalpy of air at the set temperature and humidity when a set temperature and humidity point is plotted at a position corresponding to the set temperature and humidity on a psychrometric chart is defined as a first reference enthalpy, a range in which the enthalpy is greater than the first reference enthalpy and the humidity is greater than the absolute humidity of the set temperature and humidity point is defined as a heat recovery possible range in which the second heat pump can be operated to recover heat, When it is determined that the temperature and humidity of the outside air are within the heat recovery range, the normal operation mode is automatically changed to the summer operation mode, and the second heat pump is operated.

4. The paint booth air conditioning system according to claim 3.

5. 5. The paint booth air conditioning system according to claim 2, wherein the control device switches the flow path so that immediately after changing from the normal operation mode to the summer operation mode, the heat recovered by the pre-heater is supplied to a heat storage tank to store the heat, and after the heat storage is completed, the control device supplies the hot water in the heat storage tank to the re-heater.

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