阅读说明：本技术 一种热泵热水机组及其水流异常的控制方法 (Heat pump hot water unit and control method for water flow abnormity thereof ) 是由 罗建飞 曾奕 郭庆 唐于淞 郭旭 于 2020-04-08 设计创作，主要内容包括：本发明的热泵热水机组及其水流异常的控制方法,在机组化霜运行时,通过对第二换热器进出水温度进行检测,根据上述温度差值,判断水流是否异常,控制机组的运行。根据二者温差所处的范围,控制机组的运行,并结合环境温度的情况,进行判断,控制机组运行。本发明通过上述控制方式,可有效的判断热水机组水流是否异常,是否有产生冻结的风险,防止机组冻结,保证其安全运行。(According to the heat pump hot water unit and the control method for water flow abnormity of the heat pump hot water unit, when the unit is operated in defrosting mode, the temperature of inlet and outlet water of the second heat exchanger is detected, whether the water flow is abnormal or not is judged according to the temperature difference, and the operation of the unit is controlled. And controlling the operation of the unit according to the range of the temperature difference between the two, judging according to the condition of the environmental temperature, and controlling the operation of the unit. By the control mode, whether the water flow of the hot water unit is abnormal or not and whether the risk of freezing exists or not can be effectively judged, the unit is prevented from freezing, and the safe operation of the unit is ensured.)

1. A control method for abnormal water flow of a heat pump hot water unit is characterized by comprising the following steps: the unit comprises a refrigerant circuit and a user side circuit; the compressor, the four-way valve, the first heat exchanger, the throttling device and the second heat exchanger are communicated through pipelines to form a refrigerant loop; the second heat exchanger, the water pump and the user heating water system are communicated through a pipeline to form a user side loop; through the second heat exchanger, refrigerant in the refrigerant circuit can provide heat for water in the user side circuit; the control method comprises the following steps: s01: when the unit operates in a defrosting mode, after the unit operates for a third preset time t3, the water outlet temperature Tc and the water inlet temperature Tj of the second heat exchanger are detected, whether the water flow is abnormal or not is judged according to the difference value of the water outlet temperature Tc and the water inlet temperature Tj, and the operation of the unit is controlled.

2. The control method according to claim 1, characterized in that: in step S01, determining whether the water flow is abnormal according to the difference between the two values, and controlling the operation of the unit includes:

n01: and when Tj-Tc is larger than T3 or Tj-Tc is smaller than or equal to T5, the unit is shut down and abnormal water flow is displayed, wherein T3 is a third preset temperature difference, T5 is a fifth preset temperature difference, and T3 is larger than T5.

3. The control method according to claim 2, characterized in that: in step S01, controlling the operation of the unit further includes, according to a difference between the two values:

m01: when T4< Tj-Tc is not more than T3, detecting the antifreezing temperature Td of the second heat exchanger and the change rate delta Td of the antifreezing temperature in fifth preset time T5, and if Td is less than Tk or delta Td is greater than delta Tk, switching the unit to operate in a heating mode; otherwise, the unit normally operates the defrosting process;

m02: when T5 is more than Tj and less than or equal to T4, the unit defrosts normally; wherein, T4 is a fourth preset temperature difference, Tk is a preset anti-freezing temperature, and Δ Tk is a preset anti-freezing temperature change rate.

4. The control method according to claim 3, characterized in that: in step M01, after the unit is switched to the heating mode, the method further includes: after the operation is carried out for a fourth preset time T4, the temperature Tg of the refrigerant pipeline of the second heat exchanger is detected, if Tc-Tj is greater than a sixth preset temperature difference T6 and Tg is greater than a preset pipe temperature T7, the water circuit of the unit is judged to be abnormal, and the abnormal protection of the water flow is displayed; otherwise, judging that the water flow of the unit is normal, and enabling the unit to enter defrosting operation again.

5. The control method according to any one of claims 1 to 4, characterized in that: step S01 is preceded by: S01A, detecting the ambient temperature Th;

when Th is larger than or equal to T0, judging that the unit does not defrost;

and when the Th is less than T0, detecting the operation state of the unit, and when the operation is defrosting, executing a step S01, wherein T0 is a first preset environment temperature.

6. The control method according to claim 5, characterized in that: in step S01A, when Th is greater than or equal to T0, the method further comprises: after the unit is heated and operated for a first preset time T1, detecting and judging a difference value Tc-Tj between the water outlet temperature Tc and the water inlet temperature Tj of the second heat exchanger, and when the Tc-Tj is greater than T1, stopping the unit and displaying that the water flow is abnormal; and when Tc-Tj is less than or equal to T1, the unit normally operates to heat, wherein T1 is a first preset temperature difference.

7. The control method according to claim 5, characterized in that: in the step S01A, when Th is less than T0, the running state of the unit is detected, when the unit runs for heating, the difference Tc-Tj between the water outlet temperature Tc and the water inlet temperature Tj of the second heat exchanger is detected and judged after the unit runs for a second preset time T2, and when Tc-Tj is greater than T2, the unit is shut down and abnormal water flow is displayed; and when Tc-Tj is less than or equal to T2, the unit normally operates to heat, wherein T2 is a second preset temperature difference.

8. The control method according to claim 7, characterized in that: the second preset temperature difference T2 is set in the following manner: t2 is k × T + h, where T is the operation time after the unit starts heating or the time after the unit starts heating after defrosting, and the unit is minutes, k and h are constants, k is-0.05, and h is 10.

9. A heat pump hot water unit is characterized in that: the heat pump hot water unit adopts the control method of any one of claims 1 to 8.

10. The heat pump water heating unit according to claim 9, wherein: the second heat exchanger is provided with the sensor for measuring the water inlet temperature Tj, the water outlet temperature Tc and the anti-freezing temperature Td.

Technical Field

The invention belongs to the field of heating, and particularly relates to a heat pump hot water unit and a control method for water flow abnormity of the heat pump hot water unit.

Background

The heat pump hot water unit absorbs low-temperature heat sources in air, can continuously provide hot water for daily life 24 hours all the year round regardless of severe weather such as cold winter, night, rainy days, snowy days and the like, and can be connected with heating plates or floor heating in winter to perform heating operation so as to meet the requirement of all-weather operation.

In the defrosting process of the heat pump unit, defrosting can be realized by switching the flow direction of a refrigerant (a refrigerant) through the four-way valve, but at the moment, a process of refrigerating water in a short time exists in the water side heat exchanger. When a water pump fault of a user or water flow fluctuation of a water system pipeline occurs in the defrosting process of the unit, the frost crack of the water side heat exchanger is easily caused, and the use of the unit is seriously influenced.

Therefore, the heat pump system needs to judge the condition of insufficient flow of the water outlet system in time, and the safe and efficient operation of the unit is ensured.

Disclosure of Invention

In view of the above, the present invention provides a heat pump heating unit and a method for controlling water flow abnormality thereof. The problem of the defrosting in-process, lead to the second heat exchanger (water side heat exchanger) to produce low-temperature water, when rivers are unusual, lead to the heat exchanger frost crack very easily when the temperature of water is less than 0 ℃ is solved. The invention detects and judges the system parameters of the unit in the defrosting process, and timely screens and protects faults.

Specifically, the method comprises the following steps: a control method for abnormal water flow of a heat pump hot water unit comprises a refrigerant circuit and a user side circuit; the compressor, the four-way valve, the first heat exchanger, the throttling device and the second heat exchanger are communicated through pipelines to form a refrigerant loop; the second heat exchanger, the water pump and the user heating water system are communicated through a pipeline to form a user side loop; through the second heat exchanger, the refrigerant in the refrigerant circuit provides heat to the water in the user-side circuit; the method comprises the following steps: s01: when the unit operates in a defrosting mode, after the unit operates for a third preset time t3, the water outlet temperature Tc and the water inlet temperature Tj of the second heat exchanger are detected, and the operation of the unit is controlled according to the difference value Tj-Tc of the water outlet temperature Tc and the water inlet temperature Tj.

Preferably, in step S01, the controlling the operation of the unit according to the difference Tj-Tc between the two includes: n01: and when Tj-Tc is larger than T3 or Tj-Tc is smaller than or equal to T5, the unit is shut down and water flow abnormal protection is displayed, wherein T3 is a third preset temperature difference, T5 is a fifth preset temperature difference, and T3 is larger than T5.

Preferably, in step S01, the controlling the operation of the unit according to the difference Tj-Tc between the two values further includes: m01: when T4< Tj-Tc is not more than T3, detecting the antifreezing temperature Td of the second heat exchanger and the change rate delta Td of the antifreezing temperature in fifth preset time T5, and if Td is less than Tk or delta Td is greater than delta Tk, switching the unit to operate in a heating mode; otherwise, the unit normally operates the defrosting process; m02: and when T5 is more than Tj and less than or equal to T4, the unit normally carries out defrosting, wherein T4 is a fourth preset temperature difference, Tk is a preset anti-freezing temperature, and delta Tk is a preset anti-freezing temperature change rate.

Preferably, in step M01, after the unit is switched to the heating mode, the method further includes: after the operation is carried out for a fourth preset time T4, the temperature Tg of the refrigerant pipeline of the second heat exchanger is detected, if Tc-Tj is greater than a sixth preset temperature difference T6 and Tg is greater than a preset pipe temperature T7, the water circuit of the unit is judged to be abnormal, and the abnormal protection of the water flow is displayed; otherwise, judging that the water flow of the unit is normal, and enabling the unit to enter defrosting operation again.

Preferably, step S01 is preceded by: S01A, detecting the ambient temperature Th; when Th is larger than or equal to T0, judging that the unit does not defrost; and when the Th is less than T0, detecting the operation state of the unit, and when the operation is defrosting, executing a step S01, wherein T0 is a first preset environment temperature.

Preferably, in step S01A, when Th ≧ T0, the method further includes: after the unit is heated and operated for a first preset time T1, detecting and judging a difference value Tc-Tj between the water outlet temperature Tc and the water inlet temperature Tj of the second heat exchanger, and when the Tc-Tj is greater than T1, stopping the unit and displaying that the water flow is abnormal; and when Tc-Tj is less than or equal to T1, the unit normally operates to heat, wherein T1 is a first preset temperature difference.

Preferably, in step S01a, when Th is less than T0, detecting an operation state of the unit, when the unit is operated for heating, after the unit is operated for a second preset time T2, detecting and determining a difference value Tc-Tj between an outlet water temperature Tc and an inlet water temperature Tj of the second heat exchanger, and when Tc-Tj > T2, the unit is shut down and displays that the water flow is abnormal; and when Tc-Tj is less than or equal to T2, the unit normally operates to heat, wherein T2 is a second preset temperature difference. A heat pump heating unit.

Preferably, the second preset temperature difference T2 is set in the following manner: t2 is k × T + h, where T is the operation time after the unit starts heating or the time after the unit starts heating after defrosting, and is expressed in minutes, k and h are empirical constants, k is-0.05, and h is 10.

In addition, the invention provides a heat pump hot water unit, and the hot water unit adopts any one of the control methods of the invention.

Preferably, the second heat exchanger is provided with sensors for measuring the inlet water temperature Tj, the outlet water temperature Tc and the anti-freezing temperature.

Has the advantages that:

according to the invention, the temperature of the inlet water and the outlet water of the second heat exchanger is obtained by obtaining the operation parameters of the heat pump hot water unit, interval judgment is carried out according to the temperature difference of the inlet water and the outlet water of the second heat exchanger, whether the water flow is abnormal or not is timely found according to the temperature difference, freezing is prevented, and the safe operation of the unit is effectively protected.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The above and other objects, features and advantages of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings. The drawings described below are merely some embodiments of the present disclosure, and other drawings may be derived from those drawings by those of ordinary skill in the art without inventive effort.

Fig. 1 is a schematic view of a heat pump heating unit according to an embodiment of the present invention.

Fig. 2 is a schematic flow chart of a method for controlling abnormal water flow of a heat pump heating unit according to an embodiment of the present invention.

Wherein: 1-a compressor, 2-a vapor-liquid separator, 3-a four-way valve, 4-a first heat exchanger, 5-a fan, 6-a throttling device, 7-a second heat exchanger, 8-a water pump, 9-a user heating water system, 10-a water inlet temperature measuring point, 11-a water outlet temperature measuring point and 12-an anti-freezing temperature measuring point.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals denote the same or similar parts in the drawings, and thus, a repetitive description thereof will be omitted.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the subject matter of the present disclosure can be practiced without one or more of the specific details, or with other methods, components, devices, steps, and so forth. In other instances, well-known methods, devices, implementations, or operations have not been shown or described in detail to avoid obscuring aspects of the disclosure.

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various structures, these structures should not be limited by these terms. These terms are used to distinguish one structure from another structure. Thus, a first structure discussed below may be termed a second structure without departing from the teachings of the disclosed concept. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It is to be understood by those skilled in the art that the drawings are merely schematic representations of exemplary embodiments, and that the blocks or processes shown in the drawings are not necessarily required to practice the present disclosure and are, therefore, not intended to limit the scope of the present disclosure.

The following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings 1 and 2:

the following symbols in the present invention are explained as follows: th: an outdoor ambient temperature; tj: detecting the water inlet temperature of the water side heat exchanger; tc: detecting the water outlet temperature of the water side heat exchanger; td: the anti-freezing temperature of the water side heat exchanger is detected; Δ Td: detecting the change rate of the anti-freezing temperature of the waterway heat exchanger; tg: and detecting the temperature of the refrigerant pipe of the water side heat exchanger.

t 1: the first preset time is the time (frostless) of unit heating operation (the value is 0-10 min, preferably 3 min); t 2: the second preset time is the time (frosting) of unit heating operation (the value is 0-5 min, preferably 2 min); t 3: the third preset time is the defrosting operation time of the unit (the value is 0-150 s, preferably 60 s); t 4: the fourth preset time is the time (the value is 0-10 min, preferably 4 min) for the operation of defrosting-heating of the unit; t 5: and the fifth preset time is preferably 30S.

T0: presetting an ambient temperature, and presetting an interval judgment value (the value is 0-30 ℃, preferably 10 ℃) of an ambient temperature interval; t1: a first preset temperature difference, namely a preset water temperature judgment value (the value is 0-30 ℃, preferably 12 ℃), of the temperature difference of inlet and outlet water; t2: a second preset temperature difference, namely a preset water temperature judgment value (the value is 0-30 ℃) of the water inlet and outlet temperature difference; t3: a third preset temperature difference, namely a preset water temperature judgment value (the value is 0-30 ℃, preferably 10 ℃) of the water inlet and outlet temperature difference; t4: a fourth preset temperature difference, namely a preset water temperature judgment value (the value is 0-30 ℃, preferably 6 ℃) of the water inlet and outlet temperature difference; t5: a fifth preset temperature difference, namely a preset water temperature judgment value (the value is 0-2 ℃, preferably 0.5 ℃) of the water inlet and outlet temperature difference; t6: a sixth preset temperature difference, namely a preset water temperature judgment value (the value is 0-30 ℃, preferably 8 ℃) of the water inlet and outlet temperature difference; t7: presetting a pipe temperature, namely presetting a pipe temperature judgment value (the value is 0-100 ℃, preferably 60 ℃) of the temperature of a refrigerant pipe of the water side heat exchanger; tk: presetting an antifreezing temperature, and presetting a judgment value (the value is 0-10 ℃, preferably 2 ℃) of the antifreezing temperature of the waterway heat exchanger; Δ Tk: presetting an antifreezing temperature difference and a preset judgment value (the value is 0-10 ℃, and preferably 1.5 ℃) of the change rate of the antifreezing temperature of the water path heat exchanger.

The preset parameter values are not limited to the above-mentioned parameter values, and those skilled in the art may adopt parameter values different from the above-mentioned specific values through experiments or experiences according to the actual set conditions, and all of them are within the protection scope of the present invention.

As shown in fig. 1, the heat pump hot water unit according to the embodiment of the present invention includes a refrigerant circuit and a user side circuit; the compressor 1, the four-way valve 3, the first heat exchanger 4, the throttling device 6 and the second heat exchanger 7 are communicated through pipelines to form a refrigerant loop; the second heat exchanger 7, the water pump 8 and the user heating water system 9 are communicated through pipelines to form a user side loop; the refrigerant in the refrigerant circuit provides heat to the water in the user side circuit via the second heat exchanger 7. Wherein, the second heat exchanger 7 is provided with sensors for measuring the water inlet temperature Tj, the water outlet temperature Tc and the anti-freezing temperature. The second heat exchanger 7 of the present invention is also called a water side heat exchanger, and the heat pump hot water unit of the present invention is also called a heat pump heating unit.

As shown in fig. 1, a gas-liquid separator 2 may be further provided between the compressor 1 and the four-way valve 3. The hot water unit also comprises a fan 5 for accelerating the heat exchange of the first heat exchanger 4. The second heat exchanger 7 is also provided with a water inlet temperature measuring point 10, a water outlet temperature measuring point 11 and an anti-freezing temperature measuring point 12, and the temperature of the positions is detected through a sensor or a temperature sensing bulb. The throttle 6 may be an electronic expansion valve.

As shown in fig. 2, which illustrates a control method for water flow abnormality of a heat pump hot water unit, a water side heat exchanger generates low-temperature water due to the water flow abnormality during defrosting of the heat pump hot water unit, and the heat exchanger is very likely to be frozen when the water temperature is lower than 0 ℃. In the defrosting process, a unit (system) is in refrigerating operation, the water side heat exchanger is an evaporation side, a refrigerant absorbs heat from the heat exchanger, and if the water flow of the water system is abnormal slightly and the like, the heat of the water system heat exchanger is lost, so that water is frozen and the water side heat exchanger is easily cracked.

The invention detects and judges system parameters in the defrosting process, and timely screens and protects faults. According to the invention, by acquiring the parameters of the heat pump hot water unit during operation, interval judgment is carried out according to different water path heat exchange temperature differences, and judgment is carried out by utilizing parameters such as preset antifreezing temperature of a water path, so that system abnormity is found and protected in time. When the hidden danger of too low water temperature exists in the defrosting process, the unit can be switched to a heating state, whether the water flow is abnormal or not is judged through heating operation parameters, if the water flow is abnormal, the unit is protected, and if the water flow is not abnormal, the unit is defrosted again.

The method for controlling the water flow abnormity of the heat pump water heater unit in the embodiment of the invention can comprise at least one of the following steps: step S01A, detecting the ambient temperature Th; when Th is larger than or equal to T0, the unit is determined to be operated in a higher environment range, and the unit is judged not to be defrosted; and when Th is less than T0, detecting the operation state of the unit, and when the unit operates for defrosting, executing the next step, wherein T0 is the preset ambient temperature.

In step S01A, when Th is greater than or equal to T0, the method further comprises: after the unit is heated and operated for a first preset time T1, detecting and judging a difference value Tc-Tj between the water outlet temperature Tc and the water inlet temperature Tj of the second heat exchanger 7, and when the Tc-Tj is greater than T1, stopping the unit and displaying that the water flow is abnormal; when Tc-Tj is less than or equal to T1, the unit operates normally to heat. When the difference value of Tc-Tj is large, the water outlet temperature is obviously higher than the water inlet temperature after the heat exchanger on the water side absorbs the heat of the refrigerant, the flow of a water system is at a low risk, and the unit is shut down and abnormal protection of water flow is displayed. When the difference value between the water side heat exchanger and the water side heat exchanger is small, the water outlet temperature is higher than the water inlet temperature after the heat of the refrigerant is absorbed by the water side heat exchanger, the requirement of the water outlet water is normally met, the unit is not abnormal in operation, and the unit is normally operated to heat.

In the step S01A, when Th is less than T0, the running state of the unit is detected, when the unit runs for heating, after the unit runs for a second preset time T2, the difference Tc-Tj between the water outlet temperature Tc and the water inlet temperature Tj of the second heat exchanger 7 is detected and judged, and when Tc-Tj is greater than T2, the unit is shut down and abnormal water flow is displayed; when Tc-Tj is less than or equal to T2, the unit operates normally to heat. Wherein, T2 is a result of data fitting, T2 is k T + h, T is the operation time after the unit starts heating or the time after the unit starts heating after defrosting, k and h take the value experience of k-0.05 and h 10, where the unit of T is min. When Th is less than T0, the heat exchange of the unit is complex, the fins of the first heat exchanger 4 continuously frost after the unit operates to heat, so that the difference value of Tc-Tj continuously changes, T2 is obtained by fitting experimental data under different environments, namely T2 is represented by a linear relation in k T + h, and a better effect can be achieved through the judgment. When Tc-Tj is larger than T2, namely when the difference between the Tc and the Tj is large, the water outlet temperature is obviously higher than the water inlet temperature after the heat of the refrigerant is absorbed by the water side heat exchanger, the heat absorption of the water flow in the heat exchanger is obvious, the water system flow is low, the unit is shut down, and the abnormal protection of the water flow is displayed. When Tc-Tj is less than or equal to T2, the unit operates normally to heat.

Step S01: when the unit operates in a defrosting mode, after the unit operates for a third preset time t3, the water outlet temperature Tc and the water inlet temperature Tj of the second heat exchanger 7 are detected, and the operation of the unit is controlled according to the difference value Tj-Tc between the water outlet temperature Tc and the water inlet temperature Tj.

In step S01, controlling the operation of the unit according to the difference Tj-Tc between the two values includes: n01: when Tj-Tc is larger than T3 or Tj-Tc is smaller than or equal to T5, the unit is shut down and water flow abnormal protection is displayed, and T3 is larger than T5. When Tj-Tc is larger than T3, the water flow is less; when Tj-Tc is less than or equal to T5, the heat exchanger may not exchange heat, so that the temperature difference between the front and the back of the heat exchanger is almost zero, the water system has no flow, the unit is shut down, and the abnormal protection of water flow is displayed.

In step S01, controlling the operation of the unit according to the difference Tj-Tc between the two values further includes: m01: and when T4< Tj-Tc is less than or equal to T3, detecting the antifreezing temperature Td of the second heat exchanger 7 and the change rate delta Td of the antifreezing temperature at a fifth preset time T5, wherein the fifth preset time can be 30 s. If Td < Tk or delta Td > [ delta ] Tk indicates that the freezing prevention temperature at the moment is lower than the preset freezing prevention temperature or the freezing prevention temperature of the heat exchanger is changed rapidly, indicates that the temperature of the water system is lower or the water temperature is changed rapidly at the moment, and the risk of freezing and cracking of the heat exchanger is caused by the water system, the unit is switched to the heating mode to operate. If Td >. DELTA.Tk, the rate of change is too great, indicating insufficient water flow. Otherwise, the unit normally operates the defrosting process.

In step M01, after the unit is switched to the heating mode, the method further includes: after the operation is carried out for a fourth preset time T4, the temperature Tg of a refrigerant pipeline of the second heat exchanger 7 is detected, if Tc-Tj is greater than a sixth preset temperature difference T6 and Tg is greater than a seventh preset temperature T7, the fact that the temperature difference between the front and the back of the heat exchanger is too large or the temperature of a refrigerant pipe is too high after the unit is switched to the heating operation and the water flow on the water side of the heat exchanger is too low is indicated, the water channel of the unit is judged to be abnormal, and the water flow abnormal protection is displayed; otherwise, judging that the water flow of the unit is normal, and the unit enters the defrosting operation again, and if the T4 (Tj-Tc) is detected to be less than or equal to T3 in the operation, the unit can defrost normally.

M02: when T5< Tj-Tc ≦ T4, the operation is shown to be in a reasonable range, and the unit normally carries out defrosting.

Has the advantages that:

according to the control method for the water flow abnormity of the heat pump water heater unit, when the unit is in defrosting operation, the temperature of inlet and outlet water of the second heat exchanger is detected, whether the water flow is abnormal or not is judged according to the temperature difference, and the operation of the unit is controlled. And controlling the operation of the unit according to the range of the temperature difference between the two, judging according to the condition of the environmental temperature, and controlling the operation of the unit. By the control mode, whether the water flow of the hot water unit is abnormal or not and whether the risk of freezing exists or not can be effectively judged, the unit is prevented from freezing, and the safe operation of the unit is ensured.

Exemplary embodiments of the present disclosure are specifically illustrated and described above. It is to be understood that the present disclosure is not limited to the precise arrangements, instrumentalities, or instrumentalities described herein; on the contrary, the disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.