JP7843915B2 - dehumidifier - Google Patents

Description

This technology relates to a dehumidifying device. In particular, it relates to a dehumidifying device that dehumidifies air by passing it through an evaporator and then through a reheater.

Conventionally, there are heat pump type dehumidifiers that use a reheater and evaporator installed in the room to be dehumidified to remove humidity from the indoor air. In a dehumidifier, the evaporator cools the air and condenses the moisture in it, and then the reheater reheats the air, sending the air with reduced humidity into the room.

Here, if the moisture removed from the air accumulates as frost on the evaporator, the dehumidifying capacity of the dehumidifier decreases. Therefore, the dehumidifier performs a defrosting operation to remove the frost periodically or based on changes in the refrigerant temperature.

Japanese Patent Publication No. 2020-085390

In recent years, the need for dehumidification has increased in the refrigeration sector, leading to a demand for expanded use of dehumidifiers and improved dehumidification capacity in low-temperature ranges. However, when indoor air temperatures are low, the amount of frost that accumulates on the evaporator increases, significantly reducing dehumidification capacity. This leads to an increased frequency of defrosting operations, reducing the efficiency of dehumidification in the dehumidifier.

Therefore, the objective is to obtain a dehumidifier that can improve the efficiency of defrosting operation.

To solve the above problems, the dehumidification device according to this disclosure comprises a refrigerant circuit through which the refrigerant circulates, with the following connected via piping: a compressor for compressing the refrigerant, an expansion valve for reducing the pressure of the refrigerant, a heat exchanger for exchanging heat between the air sent to the space to be dehumidified and the refrigerant, an evaporator for cooling the air that has passed through the heat exchanger to dehumidify it, and a reheater for heating the air that has passed through the evaporator and sending it to the space to be dehumidified; and a flow path switching device for switching the flow path within the refrigerant circuit between a flow path in state 1, where the heat exchanger cools the air, and a flow path in state 2, where the heat exchanger heats the air.

The disclosed dehumidifier includes a flow path switching device that switches the refrigerant flow path during dehumidification operation between state 1, where the heat exchanger cools the refrigerant, and state 2, where the heat exchanger heats the air. Therefore, by increasing the evaporation temperature of the refrigerant passing through the evaporator, frost formation in the evaporator can be suppressed. Furthermore, defrosting can be performed in the heat exchanger at this time. As a result, the defrosting time during defrosting operation can be shortened, and the efficiency of defrosting can be increased.

This diagram shows the configuration of the dehumidifier 100 according to Embodiment 1. This diagram illustrates the flow of refrigerant in the dehumidification operation mode of state 1 according to Embodiment 1. This diagram illustrates the flow of refrigerant in the dehumidification operation mode of state 2 according to Embodiment 1. This diagram illustrates the flow of refrigerant during defrosting operation in state 3 according to Embodiment 1. This diagram illustrates the process of switching states during the dehumidification operation of the control device 400 according to Embodiment 2. This diagram illustrates the process of switching the operating mode of the control device 400 according to Embodiment 2. This diagram illustrates the equipment layout in a side-flow type dehumidifier 100 according to Embodiment 3. This diagram illustrates the equipment layout in a top-flow type dehumidifier 100 according to Embodiment 3.

The dehumidifying device according to the embodiment will be described below with reference to the drawings. In the following drawings, parts with the same reference numerals are the same or equivalent and are common to the entire text of the embodiment described below. Also, the size relationships of each component in the drawings may differ from those of the actual components. Furthermore, the forms of the components shown in the entire specification are merely examples and are not limited to the forms described in the specification. In particular, the combination of components is not limited to the combinations in each embodiment, and components described in other embodiments can be applied to other embodiments. Furthermore, the high and low values of pressure and temperature are not determined in relation to absolute values, but are determined relatively in relation to the state and operation of the device, etc. Also, when there is no need to distinguish or specify multiple similar devices, etc. that are distinguished by subscripts, the subscripts may be omitted in the description.

Embodiment 1.
Figure 1 shows the configuration of a dehumidifier 100 according to Embodiment 1. The dehumidifier 100 according to Embodiment 1 has a compressor 110, a reheater 120, an expansion valve 130, an evaporator 140, and a heat exchanger 150 connected by piping to form a refrigerant circuit. The dehumidifier 100 also has a blower 160.

The compressor 110 compresses and discharges the inhaled refrigerant. In particular, in Embodiment 1, the compressor 110 is driven at a constant speed. The reheater 120 exchanges heat between the refrigerant and the indoor air sent into the room, which is the space to be dehumidified, causing the refrigerant to condense and liquefy. At this time, the reheater 120 heats the indoor air. The expansion valve 130 is a pressure reducing device that adjusts the pressure of the refrigerant, reduces the pressure to expand it, and adjusts the flow rate.

The evaporator 140 evaporates and vaporizes the refrigerant. At this time, the evaporator 140 cools the indoor air and condenses the moisture in the air. The heat exchanger 150 exchanges heat between the indoor air and the refrigerant. When the dehumidifier 100 operates in the dehumidification mode of State 1, which will be described later, the heat exchanger 150 functions as an evaporator, and when it operates in the dehumidification mode of State 2, which will be described later, the heat exchanger 150 functions as a condenser. In the dehumidifier 100 of Embodiment 1, the evaporator 140 and the heat exchanger 150 are connected in parallel in the refrigerant circuit. Generally, the condenser has a larger capacity than the evaporator. Therefore, in the dehumidification modes of State 1 and State 2, which will be described later, the reheater 120, evaporator 140, and heat exchanger 150 have capacities that satisfy the relationship reheater 120 > evaporator 140 + heat exchanger 150. Furthermore, this explanation assumes that the capacities of the evaporator 140 and the heat exchanger 150 are the same. However, this is not the only possible explanation.

The blower 160 sends and passes indoor air through the evaporator 140, heat exchanger 150, and reheater 120. In Embodiment 1, the blower 160 is positioned to pass indoor air through the heat exchanger 150, evaporator 140, and reheater 120 in that order. Here, the blower 160 is, for example, an axial flow fan that rotates around an axis.

Furthermore, the dehumidifier 100 in Embodiment 1 includes a flow path switching device 200 that switches the flow path of the refrigerant flowing in the refrigerant circuit depending on the operating mode. The flow path switching device 200 in Embodiment 1 includes, for example, a first solenoid valve 210, a second solenoid valve 220, a third solenoid valve 230 and a fourth solenoid valve 240, as well as a first check valve 250 and a second check valve 260.

The first solenoid valve 210, the second solenoid valve 220, the third solenoid valve 230, and the fourth solenoid valve 240 are on-off valves that open and close based on instructions from a control device 400, which will be described later, and allow or block the flow of refrigerant in the piping in which they are located. The first solenoid valve 210 is located in the piping between the discharge side of the compressor 110 and the reheater 120. The second solenoid valve 220 is located in the piping between the discharge side of the compressor 110 and the evaporator 140. The third solenoid valve 230 is located in the piping between the discharge side of the compressor 110 and the heat exchanger 150. The fourth solenoid valve 240 is located in the piping between the suction side of the compressor 110 and the heat exchanger 150.

Furthermore, the first check valve 250 and the second check valve 260 are valves that restrict the flow of refrigerant in the installed piping to one direction. The first check valve 250 prevents refrigerant from flowing from the heat exchanger 150 to the evaporator 140 in the piping connecting the evaporator 140 and the heat exchanger 150. The second check valve 260 is located in a bypass pipe 270 separate from the flow path where the third solenoid valve 230 is located, in the piping connecting the discharge side of the compressor 110 to the reheater 120 and the heat exchanger 150, and prevents refrigerant from flowing from the discharge side of the compressor 110 to the heat exchanger 150.

Furthermore, the dehumidifier 100 in Embodiment 1 has sensors that detect physical quantities used by the control device 400, which will be described later, when making a determination. The air temperature sensor 300 is a sensor that detects the temperature of the indoor air. For example, the air temperature sensor 300 detects the temperature of the indoor air drawn into the dehumidifier 100 by the drive of the blower 160. The expansion valve downstream temperature sensor 310 is a sensor that detects the temperature of the refrigerant that has passed through the expansion valve 130 during dehumidification operation. Here, the expansion valve downstream temperature sensor 310 is an evaporation temperature sensor, and the temperature detected by the expansion valve downstream temperature sensor 310 is the evaporation temperature ET, which will be described later. The suction temperature sensor 320 is a sensor that detects the suction side temperature, which is the temperature of the refrigerant on the suction side of the compressor 110. The air humidity sensor 330 is a sensor that detects the humidity of the indoor air.

The control device 400 controls the equipment within the dehumidifier 100. In particular, the control device 400 controls the opening and closing of the first solenoid valve 210 to the fourth solenoid valve 240 in the flow path switching device 200, thereby controlling the flow path of the refrigerant in the refrigerant circuit. In this embodiment 1, the control device 400 includes a state determination unit 410, a flow path control unit 420, and a timing unit 430. The state determination unit 410 determines whether to change the operating mode based on the physical quantity data in the signal sent from the sensor. The flow path control unit 420 opens and closes the first solenoid valve 210 to the fourth solenoid valve 240 based on the determination of the state determination unit 410, thereby switching the flow path. The timing unit 430 has a timer and performs timing. The time measured by the timing unit 430 is used by the state determination unit 410 when making a determination.

Here, the control device 400 is assumed to be composed of a microcomputer having a control arithmetic processing unit such as a CPU (Central Processing Unit). The control device 400 then executes processing based on the program and realizes the processing. The control device 400 also has a volatile storage device (not shown) such as RAM (Random Access Memory) that can temporarily store data, and a non-volatile auxiliary storage device (not shown) such as flash memory that can store data and programs for a long period of time.

Figure 2 is a diagram illustrating the flow of refrigerant in the dehumidification operation mode of State 1 according to Embodiment 1. The arrows in Figure 2 indicate the flow of refrigerant in the flow path within the refrigerant circuit during operation in the dehumidification operation mode when State 1 is reached. In the dehumidification operation mode of State 1, the heat exchanger 150 functions as an evaporator. In the dehumidification operation mode of State 1, the dehumidifier 100 performs normal dehumidification by having the evaporator 140 and the heat exchanger 150 cool the indoor air. In State 1, the control device 400 opens the first solenoid valve 210 and the fourth solenoid valve 240, and closes the second solenoid valve 220 and the third solenoid valve 230. In Figure 2, the filled-in valves are valves that block the flow of refrigerant (the same applies to the following figures).

The high-temperature and high-pressure gaseous refrigerant, compressed and discharged by the compressor 110, passes through the first solenoid valve 210 and flows into the reheater 120. There, the refrigerant condenses and liquefies by exchanging heat with the indoor air. The liquefied refrigerant passes through the expansion valve 130. As it passes through the expansion valve 130, the refrigerant is depressurized and becomes a two-phase gas-liquid state. The refrigerant, now in a two-phase gas-liquid state after being depressurized in the expansion valve 130, passes through the evaporator 140 and the first check valve 250 to the heat exchanger 150, where it evaporates and becomes a gas by exchanging heat with the indoor air.

Then, in the evaporator 140 and heat exchanger 150, the refrigerant evaporates by exchanging heat with the indoor air, and the gasified refrigerant that flows out of the evaporator 140 is drawn into the compressor 110. The gasified refrigerant that flows out of the heat exchanger 150 also passes through the fourth solenoid valve 240 and is drawn into the compressor 110.

Figure 3 is a diagram illustrating the refrigerant flow in the dehumidification operation mode of state 2 according to Embodiment 1. The arrows in Figure 3 indicate the refrigerant flow during operation in the dehumidification operation mode when the flow path in the refrigerant circuit is in state 2. In the dehumidification operation mode of state 2, the heat exchanger 150 functions as a condenser.

As mentioned above, the heat exchanger 150 is located upstream (windward) in the flow of indoor air supplied from the blower 160. Therefore, the indoor air heated by the heat exchanger 150 passes through the evaporator 140, suppressing frost formation on the evaporator 140. Also, because the heat exchanger 150 is located upstream, it is more prone to frost formation than the evaporator 140. Therefore, in state 2, the heat exchanger 150 heats the indoor air, allowing the dehumidifier 100 to defrost the heat exchanger 150 while performing dehumidification. In state 2, the control device 400 opens the third solenoid valve 230 and closes the first solenoid valve 210, the second solenoid valve 220, and the fourth solenoid valve 240.

The high-temperature, high-pressure gaseous refrigerant, compressed and discharged by the compressor 110, passes through the third solenoid valve 230 and flows into the heat exchanger 150. The refrigerant becomes a two-phase gas-liquid state by exchanging heat with the indoor air. The two-phase gas-liquid refrigerant then passes through the bypass piping 270 and the second check valve 260 and flows into the reheater 120. After passing through the reheater 120, the refrigerant condenses and liquefies.

The liquefied refrigerant passes through the expansion valve 130. As it passes through the expansion valve 130, the refrigerant is depressurized and becomes a two-phase gas-liquid state. The refrigerant, now in a two-phase gas-liquid state after being depressurized in the expansion valve 130, passes through the evaporator 140, where it exchanges heat with the indoor air, evaporates, and becomes a gas. The gasified refrigerant that flows out of the evaporator 140 is then drawn into the compressor 110.

Figure 4 is a diagram illustrating the flow of refrigerant during defrosting operation in state 3 according to Embodiment 1. The arrows in Figure 4 indicate the flow of refrigerant during operation in the defrosting mode when the flow path in the refrigerant circuit is in state 3. In the defrosting mode of state 3, the dehumidifier 100 performs a defrosting operation to defrost the evaporator 140. In state 3, the control device 400 opens the second solenoid valve 220 and closes the first solenoid valve 210, the third solenoid valve 230, and the fourth solenoid valve 240. The control device 400 also closes the expansion valve 130.

The high-temperature, high-pressure gaseous refrigerant, compressed and discharged by the compressor 110, passes through the second solenoid valve 220 and flows into the evaporator 140. The gaseous refrigerant exchanges heat with the frost on the evaporator 140, melting the frost and removing it from the evaporator 140. The refrigerant that has flowed out of the evaporator 140 is drawn back into the compressor 110.

As described above, the dehumidifier 100 in Embodiment 1 has an evaporator 140 and a heat exchanger 150 connected in parallel by piping in the refrigerant circuit. The control device 400 controls the first solenoid valve 210 to the fourth solenoid valve 240 of the flow path switching device 200 to switch the flow path of the refrigerant during dehumidification operation between state 1 and state 2. During dehumidification operation in state 2, the heat exchanger 150 heats the indoor air, and the heated indoor air passes through the evaporator 140, thereby increasing the evaporation temperature ET. This suppresses frost formation on the evaporator 140. At this time, the heat exchanger 150 can defrost while heating the indoor air. Therefore, even when the dehumidifier 100 performs defrosting operation, it is only necessary to defrost the evaporator 140, and the defrosting operation time can be shortened. For this reason, the dehumidifier 100 in Embodiment 1 can increase the efficiency of dehumidification. While not limited to these applications, it is particularly effective for dehumidifying environments such as refrigerated spaces, which have a low-temperature, high-humidity atmosphere.

Furthermore, the compressor 110 of the dehumidifier 100 in Embodiment 1 is a constant-speed compressor with a constant rotational speed. Therefore, compared to a variable-speed compressor, it is possible to improve the efficiency of dehumidification operation with a less expensive configuration.

Embodiment 2.
Figure 5 illustrates the process of switching states during dehumidification operation of the control device 400 according to Embodiment 2. Based on the evaporation temperature ET [°C], the control device 400 performs a determination process to switch the flow of refrigerant in the refrigerant circuit to state 1 or state 2 as described in Embodiment 1.

The control device 400 determines whether the current flow path state of the refrigerant circuit is in dehumidification operation mode according to state 1 (step S1). If the control device 400 determines that it is in state 1, it further determines whether the evaporation temperature ET [°C] has remained below the first control temperature To [°C] for a set time t1 [seconds] (step S2). Here, the set time t1 [seconds] is a time that has been set arbitrarily in advance. The first control temperature To is a temperature that has been set arbitrarily in advance, for example, 0 [°C].

If the control device 400 determines that the conditions of step S2 are met, it assumes that the evaporator 140 and heat exchanger 150 are in an operating state where frost is likely to form. Then, the control device 400 opens the third solenoid valve 230 and closes the first solenoid valve 210 and the fourth solenoid valve 240, switching the flow path of the refrigerant circuit to state 2 (step S3). On the other hand, if the control device 400 determines that the conditions of step S2 are not met, it continues in state 1 (step S4).

On the other hand, if the control device 400 determines in step S1 that the state is not state 1, it further determines whether the evaporation temperature ET [°C] has continuously exceeded the second control temperature To + α [°C] for a set time t1 [seconds] (step S5). Here, α is a value set as a margin to prevent frequent switching to state 1 or state 2.

If the control device 400 determines that the conditions of step S5 are met, it determines that the operating state is such that frost formation on the evaporator 140 and heat exchanger 150 is unlikely to occur. Then, the control device 400 opens the first solenoid valve 210 and the fourth solenoid valve 240 and closes the third solenoid valve 230, switching the flow path of the refrigerant circuit to state 1 (step S6). On the other hand, if the control device 400 determines that the conditions of step S5 are not met, it continues in state 2 (step S7).

Figure 6 illustrates the process of switching the operating mode of the control device 400 according to Embodiment 2. The control device 400 performs a determination process to switch between dehumidification operation mode and defrosting operation mode based on the evaporation temperature ET [°C].

The control device 400 determines whether the system is in dehumidification mode (state 1 or state 2) (step S11). If the control device 400 determines that the system is not operating in dehumidification mode, it continues operation in the current state (step S13) and terminates the process.

On the other hand, if the control device 400 determines that the operation is in the dehumidification mode of state 2, it further determines whether the state in which the evaporation temperature ET [°C] is below the third control temperature Td [°C] and the compressor suction superheat SH is below the set temperature Tsh has continued for a set time t2 [seconds] (step S12). Here, the compressor suction superheat SH is the temperature difference between the suction side temperature detected by the suction temperature sensor 320 and the evaporation temperature ET detected by the expansion valve downstream temperature sensor 310. The set temperature Tsh is a temperature that has been arbitrarily set in advance. The third control temperature Td is set to a value lower than the first control temperature To. The set time t2 [seconds] is a time that has been arbitrarily set in advance. The set time t2 is set to be longer than the set time t1.

If the control device 400 determines that the conditions in step S12 are not met, it continues operation in the current state (step S13) and terminates the process. On the other hand, if the control device 400 determines that the conditions in step S12 are met, it opens the second solenoid valve 220, closes the first solenoid valve 210, the third solenoid valve 230, and the fourth solenoid valve 240, switches the flow path of the refrigerant circuit to state 3 (step S14), and terminates the process.

As described above, in the dehumidifier 100 of Embodiment 2, the state determination unit 410 of the control device 400 determines whether to switch between operation in state 1 dehumidification mode or state 1 dehumidification mode based on the evaporation temperature ET of the refrigerant circuit. When the evaporation temperature ET remains low for a certain period of time, operation in state 2 dehumidification mode raises the evaporation temperature ET, thereby suppressing frost formation.

Furthermore, the state determination unit 410 determines whether to operate in the defrosting operation mode of state 3 based on the evaporation temperature ET and the compressor suction superheating degree SH. Therefore, the dehumidifier 100 can perform defrosting under more appropriate conditions, thereby increasing the efficiency of the dehumidification operation. In this case, in the dehumidifier 100 of the second embodiment, the control device 400 controls the system to switch from the dehumidification operation mode of state 2 to the defrosting operation mode of state 3. Therefore, it is possible to prevent residual frost from remaining on the heat exchanger 150 after the defrosting operation is completed.

Embodiment 3.
Figure 7 illustrates the equipment layout in a side-flow type dehumidifier 100 according to Embodiment 3. Figure 8 illustrates the equipment layout in a top-flow type dehumidifier 100 according to Embodiment 3.

The side-flow type dehumidifier 100 shown in Figure 7 has an air outlet for indoor air on the side of the housing. In the dehumidifier 100 of Figure 7, the rotation axis of the blower 160 is positioned horizontally, and indoor air is blown out in the side direction. The top-flow type dehumidifier 100 shown in Figure 8 has an air outlet for indoor air on the top surface of the housing. In the dehumidifier 100 of Figure 8, the rotation axis of the blower 160 is positioned vertically, and indoor air is blown out in the upward direction.

As shown in Figures 7 and 8, the dehumidifier 100 may be of either a side-flow or top-flow type. In either type, the structure should allow indoor air to flow through the heat exchanger 150, evaporator 140, and reheater 120 in that order.

Furthermore, while the dehumidifier 100 in Figures 7 and 8 incorporates a compressor 110, the configuration is not limited to this. For example, if the compressor 110 cannot be housed in a single enclosure due to the structure or size of the device, the compressor 110 may be housed in a separate enclosure and connected to the reheater 120 and other components via piping.

Here, the dehumidifier 100 has been described as having two evaporators, an evaporator 140 and a heat exchanger 150, connected in parallel by piping. However, three or more evaporators 140 and heat exchangers 150 may be connected in parallel by piping. Furthermore, for example, when the control device 400 switches the flow path by controlling the flow path switching device 200 during operation in the dehumidification operation mode of state 2, it may be configured so that the evaporator or other component that is furthest upstream (most windward) in relation to the airflow heats the indoor air.

Furthermore, in Embodiments 1 and 2, the temperature detected by the expansion valve downstream temperature sensor 310 was used as the evaporation temperature ET, but this is not the only option. For example, a pressure sensor may be provided on the suction side of the compressor 110 of the refrigerant circuit, and the saturation temperature calculated from the pressure detected by the pressure sensor may be used as the evaporation temperature ET. Alternatively, the state determination unit 410 of the control device 400 may directly use the pressure detected by the pressure sensor for determination.

Furthermore, in Embodiments 1 and 2, the state determination unit 410 of the control device 400 used the evaporation temperature ET for determination, but it is not limited to this. For example, the state determination unit 410 may perform the determination using the temperature or humidity of the indoor air flowing into the dehumidifier 100.

Furthermore, while the dehumidifier 100 of Embodiments 1 and 2 switches the flow path between states 1 and 3 using the first solenoid valve 210 to the fourth solenoid valve 240 of the flow path switching device 200, the invention is not limited to this. For example, another type of valve, such as a three-way valve, may be used to switch the flow path in the refrigerant circuit between states 1 and 3.

In Embodiment 1 and other embodiments, the dehumidifier 100 was described as a standalone device, but it is not limited to this. For example, it can be configured as part of an air conditioning system, cooling system, or refrigeration system. It can also be configured as part of a system.

100 Dehumidifier, 110 Compressor, 120 Reheater, 130 Expansion valve, 140 Evaporator, 150 Heat exchanger, 160 Blower, 200 Flow path switching device, 210 First solenoid valve, 220 Second solenoid valve, 230 Third solenoid valve, 240 Fourth solenoid valve, 250 First check valve, 260 Second check valve, 270 Bypass piping, 300 Air temperature sensor, 310 Expansion valve downstream temperature sensor, 320 Intake temperature sensor, 330 Air humidity sensor, 400 Control device, 410 State determination unit, 420 Flow path control unit, 430 Timing unit.

Claims (7)

A compressor for compressing the refrigerant, an expansion valve for reducing the pressure of the refrigerant, a heat exchanger for exchanging heat between the refrigerant and the air sent to the space to be dehumidified, an evaporator for cooling and dehumidifying the air that has passed through the heat exchanger, and a reheater for heating the air that has passed through the evaporator and sending it to the space to be dehumidified are connected by piping, and a refrigerant circuit through which the refrigerant circulates,
A dehumidifying device comprising a flow path switching device that switches the flow path in the refrigerant circuit between a flow path in state 1 where the heat exchanger cools the air and a flow path in state 2 where the heat exchanger heats the air. The dehumidifier according to claim 1, wherein the flow path switching device switches the flow path in the refrigerant circuit to the flow path in state 3 for defrosting the evaporator. A bypass pipe connecting the reheater and the heat exchanger,
The flow path switching device has on/off valves installed between the discharge side piping of the compressor and the heat exchanger, and between the discharge side piping of the compressor and the reheater, respectively.
The dehumidifier according to claim 1 or 2, wherein, in the flow path of state 2, the on-off valve between the discharge side piping of the compressor and the heat exchanger is opened, the on-off valve between the discharge side piping of the compressor and the reheater is closed, and the flow path is such that the refrigerant discharged by the compressor passes through the heat exchanger, the reheater, the expansion valve and the evaporator in that order. An evaporation temperature sensor for detecting the evaporation temperature of the refrigerant circuit,
The system includes a control device that controls the flow path switching of the aforementioned flow path switching device,
The dehumidifier according to claim 1 or 2 , wherein the control device controls the switching of the flow path of the flow path switching device based on the evaporation temperature. The dehumidifier according to claim 4, wherein the control device determines that the evaporation temperature remains lower than a predetermined control temperature To for a predetermined set time t1, and instructs the flow path switching device to switch from the flow path in state 1 to the flow path in state 2. An evaporation temperature sensor for detecting the evaporation temperature of the refrigerant circuit,
An intake temperature sensor for detecting the intake side temperature of the compressor,
The system includes a control device that controls the flow path switching of the aforementioned flow path switching device,
The dehumidifier according to claim 2, wherein the control device controls the switching of the flow path to the flow path of state 3 by the flow path switching device based on the temperature difference between the evaporation temperature and the intake side temperature and the evaporation temperature. The dehumidifier according to claim 6, wherein the control device determines that the evaporation temperature remains lower than a predetermined control temperature Td for a predetermined set time t2, and instructs the flow path switching device to switch from the flow path in state 2 to the flow path in state 3.