阅读说明：本技术 水冷热泵机组及其控制方法 (Water-cooled heat pump unit and control method thereof ) 是由 张瑞台 李玉阁 张虹 张志平 王明久 张捷 王波 于 2020-12-31 设计创作，主要内容包括：本发明涉及制冷设备技术领域,具体提供了一种水冷热泵机组及其控制方法,旨在解决水冷热泵机组的压缩机超范围非正常运行的问题。本发明的水冷热泵机组的控制方法包括如下步骤：比较水冷热泵机组的机组蒸发温度和压缩机蒸发温度上限之间的大小关系；根据比较结果,选择性地调节机组蒸发温度直至其小于或等于压缩机蒸发温度上限,或者保持水冷热泵机组以当前冷却水泵频率和当前冷冻水泵频率运行。该控制方法根据机组蒸发温度和压缩机蒸发温度上限之间大小关系的比较结果,采取不同的控制策略,将机组蒸发温度控制在压缩机蒸发温度上限以内,保证了压缩机始终正常运行,确保了压缩机的使用寿命以及水冷热泵机组的正常运行。(The invention relates to the technical field of refrigeration equipment, in particular provides a water-cooling heat pump unit and a control method thereof, and aims to solve the problem that a compressor of the water-cooling heat pump unit abnormally operates in an over-range mode. The control method of the water-cooling heat pump unit comprises the following steps: comparing the magnitude relation between the unit evaporation temperature of the water-cooling heat pump unit and the upper limit of the compressor evaporation temperature; and selectively adjusting the unit evaporation temperature until the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature or keeping the water cooling and heating pump unit to operate at the current cooling water pump frequency and the current freezing water pump frequency according to the comparison result. According to the control method, different control strategies are adopted according to the comparison result of the size relation between the unit evaporation temperature and the upper limit of the compressor evaporation temperature, the unit evaporation temperature is controlled within the upper limit of the compressor evaporation temperature, the compressor is guaranteed to operate normally all the time, the service life of the compressor is guaranteed, and the normal operation of the water-cooling heat pump unit is guaranteed.)

1. A control method of a water-cooling heat pump unit is characterized by comprising the following steps:

comparing the magnitude relation between the unit evaporation temperature of the water-cooling heat pump unit and the upper limit of the compressor evaporation temperature;

and selectively adjusting the unit evaporation temperature until the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature or keeping the water-cooling heat pump unit to operate at the current cooling water pump frequency and the current chilled water pump frequency according to the comparison result.

2. The control method according to claim 1, wherein "selectively adjusting the unit evaporating temperature until it is less than or equal to the upper compressor evaporating temperature limit or keeping the water-cooling heat pump unit operating at the current cooling water pump frequency and the current chilled water pump frequency according to the comparison result" comprises the steps of:

when the unit evaporation temperature is greater than the upper limit of the compressor evaporation temperature, adjusting the unit evaporation temperature until the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature;

and when the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature, keeping the water-cooling heat pump unit to operate at the current cooling water pump frequency and the current freezing water pump frequency.

3. The control method according to claim 2, characterized by further comprising the steps of:

comparing the frequency of a chilled water pump of the water-cooling heat pump unit with the lowest frequency allowed by the chilled water pump and/or the size relation between the opening of the expansion valve and the minimum opening of the expansion valve;

when the unit evaporation temperature is greater than the upper limit of the compressor evaporation temperature, the unit evaporation temperature is adjusted until the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature, and the method comprises the following steps:

and when the unit evaporation temperature is higher than the upper limit of the compressor evaporation temperature, selectively adjusting the unit evaporation temperature by reducing the frequency of the chilled water pump or reducing the opening of the expansion valve until the unit evaporation temperature is lower than or equal to the upper limit of the compressor evaporation temperature according to the comparison result of the frequency of the chilled water pump and/or the opening of the expansion valve.

4. The control method according to claim 3, wherein "selectively adjusting the unit evaporation temperature by decreasing the chilled water pump frequency or decreasing the expansion valve opening degree until it is less than or equal to the compressor evaporation temperature upper limit according to the comparison result of the chilled water pump frequency and/or the expansion valve opening degree" comprises the steps of:

when the frequency of the chilled water pump is greater than or equal to the lowest allowable frequency of the chilled water pump, the unit evaporation temperature is adjusted by reducing the frequency of the chilled water pump until the frequency is less than or equal to the upper limit of the compressor evaporation temperature;

when the frequency of the chilled water pump is less than the lowest allowable frequency of the chilled water pump and the opening degree of the expansion valve is greater than the minimum opening degree of the expansion valve, the evaporation temperature of the unit is adjusted by reducing the opening degree of the expansion valve until the frequency is less than or equal to the upper limit of the evaporation temperature of the compressor;

and when the frequency of the chilled water pump is less than the lowest allowable frequency of the chilled water pump and the opening of the expansion valve is less than or equal to the minimum opening of the expansion valve, returning to the step of comparing the magnitude relation between the unit evaporation temperature of the water-cooling heat pump unit and the upper limit of the compressor evaporation temperature.

5. The control method according to claim 4, characterized by further comprising the steps of:

comparing the relationship between the unit exhaust pressure of the water-cooling heat pump unit and the high-pressure early warning pressure of the unit;

when the frequency of the chilled water pump is less than the lowest allowable frequency of the chilled water pump and the opening degree of the expansion valve is greater than the minimum opening degree of the expansion valve, the unit evaporation temperature is adjusted by reducing the opening degree of the expansion valve until the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature, and the method comprises the following steps:

when the frequency of the chilled water pump is smaller than the lowest allowable frequency of the chilled water pump and the opening degree of the expansion valve is larger than the minimum opening degree of the expansion valve, selectively adjusting the unit evaporation temperature by reducing the opening degree of the expansion valve until the unit evaporation temperature is smaller than or equal to the upper limit of the compressor evaporation temperature or adjusting the unit exhaust pressure by increasing the frequency of the cooling water pump of the water-cooling heat pump unit until the unit exhaust pressure is smaller than the high-pressure early warning pressure of the unit according to the comparison result of the unit exhaust pressure.

6. The control method according to claim 5, wherein selectively adjusting the unit evaporation temperature by decreasing the opening degree of the expansion valve until it is less than or equal to the highest evaporation temperature of the compressor operation or adjusting the unit exhaust pressure by increasing the frequency of the cooling water pump of the water-cooled heat pump unit until it is less than the unit high-pressure warning pressure according to the comparison result of the unit exhaust pressures comprises the following steps:

when the exhaust pressure of the unit is smaller than the high-pressure early warning pressure of the unit, the evaporation temperature of the unit is adjusted by reducing the opening of the expansion valve until the exhaust pressure is smaller than or equal to the upper limit of the evaporation temperature of the compressor;

when the unit exhaust pressure is greater than or equal to the unit high-pressure early warning pressure, the unit exhaust pressure is adjusted by increasing the frequency of a cooling water pump of the water-cooling heat pump unit until the unit exhaust pressure is less than the unit high-pressure early warning pressure.

7. The control method according to claim 6, wherein the step of adjusting the unit exhaust pressure by increasing the frequency of a cooling water pump of the water-cooling heat pump unit until the unit exhaust pressure is lower than the unit high-pressure warning pressure comprises the following steps:

when the frequency of the cooling water pump is increased, the frequency of the cooling water pump is a preset value;

and after the water-cooled heat pump unit operates for a preset time with the increased frequency of the cooling water pump, returning to the step of comparing the size relation between the unit exhaust pressure of the water-cooled heat pump unit and the unit high-pressure early warning pressure.

8. The control method according to any one of claims 3 to 7, wherein "adjusting the unit evaporating temperature by reducing the chilled water pump frequency until it is less than or equal to the compressor operating maximum evaporating temperature" comprises the steps of:

reducing the frequency of the chilled water pump by a preset value;

and after the water-cooling heat pump unit is kept running for a preset time with the reduced frequency of the chilled water pump, returning to the step of comparing the size relationship between the unit evaporation temperature of the water-cooling heat pump unit and the upper limit of the compressor evaporation temperature.

9. The control method according to any one of claims 3 to 7, wherein "adjusting the unit evaporating temperature by decreasing the opening degree of the expansion valve until it is less than or equal to the compressor operation maximum evaporating temperature" comprises the steps of:

reducing the opening degree of the expansion valve by a preset value;

and after the water-cooling heat pump unit is kept running for a preset time with the reduced opening of the expansion valve, the step of comparing the size relation between the unit evaporation temperature of the water-cooling heat pump unit and the upper limit of the compressor evaporation temperature is returned.

10. A water-cooled heat pump unit comprising a controller, wherein the controller is configured to execute the control method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of refrigeration equipment, and particularly provides a water-cooling heat pump unit and a control method thereof.

Background

The water-cooled heat pump unit at least comprises a compressor, a condenser, an electronic expansion valve, an evaporator, a cooling tower, a cooling water pump and a chilled water pump. The condenser has a refrigerant flow path through which a refrigerant flows and a cooling water flow path through which cooling water flows, and the refrigerant flow path and the cooling water flow independently of each other, but the refrigerant and the cooling water flowing through the refrigerant flow path and the cooling water flow in heat exchange with each other. Similarly, the evaporator has a refrigerant flow path through which cooling water flows and a chilled water flow path through which chilled water flows, and the refrigerant flow path and the chilled water flow path are independent of each other, but the refrigerant and the chilled water flowing through both can exchange heat with each other.

The refrigerant flow paths of the compressor, the condenser, the electronic expansion valve and the evaporator are connected by pipelines to form a refrigerant circulation loop. The cooling water circulation loop is formed by connecting cooling water flow paths of the cooling tower, the cooling water pump and the condenser through pipelines. The chilled water flow path and the chilled water pump of the evaporator form a chilled water circulation loop with the end equipment heat exchanger on the user side through pipelines.

When the water-cooling heat pump unit works, the compressor sucks the low-temperature and low-pressure refrigerant gas agent of the evaporator, and the refrigerant gas agent is compressed into high-temperature and high-pressure gas by the compressor and is discharged to the condenser; in the condenser, high-temperature and high-pressure refrigerant gas exchanges heat with cooling water and is condensed into normal-temperature and high-pressure refrigerating liquid, and the heated cooling water is conveyed to a cooling tower by a cooling water pump and is recycled after being cooled by air; the refrigerant liquid with a certain supercooling degree is cooled and decompressed by the electronic expansion valve and then enters the evaporator; in the evaporator, low-temperature low-pressure refrigerant exchanges heat with chilled water, the refrigerant gas absorbs the heat of the chilled water to become low-temperature low-pressure refrigerant gas with a certain superheat degree, the refrigerant gas is sucked into the compressor by the compressor to start a new cycle, and the chilled water passing through the evaporator is cooled and is conveyed to the heat exchanger of the end equipment by the chilled water pump to exchange heat with indoor air so as to continuously send cold air.

The compressor is one of the core functional elements of the water-cooling heat pump unit, the water-cooling heat pump unit is required to be operated within a specified limit temperature range, if the compressor is abnormally operated beyond the limit temperature range for a long time, the service life of the compressor is shortened, the compressor is burnt, and the water-cooling heat pump unit cannot be used.

In view of the above, those skilled in the art need to solve the problem of abnormal operation of the compressor of the water-cooled heat pump unit beyond the range.

Disclosure of Invention

In order to solve the problem that a compressor of the water-cooling heat pump unit abnormally operates beyond the range, the invention provides a control method of the water-cooling heat pump unit on the one hand.

The invention discloses a control method of a water-cooling heat pump unit, which comprises the following steps: comparing the magnitude relation between the unit evaporation temperature of the water-cooling heat pump unit and the upper limit of the compressor evaporation temperature; and selectively adjusting the unit evaporation temperature until the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature or keeping the water-cooling heat pump unit to operate at the current cooling water pump frequency and the current chilled water pump frequency according to the comparison result.

In a preferable embodiment of the above control method of the present invention, "selectively adjusting the unit evaporation temperature until it is less than or equal to the upper limit of the compressor evaporation temperature or keeping the water-cooling heat pump unit operating at the current cooling water pump frequency and the current chilled water pump frequency according to the comparison result" includes the following steps: when the unit evaporation temperature is greater than the upper limit of the compressor evaporation temperature, adjusting the unit evaporation temperature until the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature; and when the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature, keeping the water-cooling heat pump unit to operate at the current cooling water pump frequency and the current freezing water pump frequency.

In a preferable aspect of the above control method of the present invention, the control method further includes: comparing the frequency of a chilled water pump of the water-cooling heat pump unit with the lowest frequency allowed by the chilled water pump and/or the size relation between the opening of the expansion valve and the minimum opening of the expansion valve; when the unit evaporation temperature is greater than the upper limit of the compressor evaporation temperature, the unit evaporation temperature is adjusted until the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature, and the method comprises the following steps: and when the unit evaporation temperature is higher than the upper limit of the compressor evaporation temperature, selectively adjusting the unit evaporation temperature by reducing the frequency of the chilled water pump or reducing the opening of the expansion valve until the unit evaporation temperature is lower than or equal to the upper limit of the compressor evaporation temperature according to the comparison result of the frequency of the chilled water pump and/or the opening of the expansion valve.

In a preferable aspect of the above control method of the present invention, "selectively adjusting the unit evaporation temperature by decreasing the chilled water pump frequency or decreasing the expansion valve opening degree until it is less than or equal to the compressor evaporation temperature upper limit according to a comparison result of the chilled water pump frequency and/or the expansion valve opening degree" includes: when the frequency of the chilled water pump is greater than or equal to the lowest allowable frequency of the chilled water pump, the unit evaporation temperature is adjusted by reducing the frequency of the chilled water pump until the frequency is less than or equal to the upper limit of the compressor evaporation temperature; when the frequency of the chilled water pump is less than the lowest allowable frequency of the chilled water pump and the opening degree of the expansion valve is greater than the minimum opening degree of the expansion valve, the evaporation temperature of the unit is adjusted by reducing the opening degree of the expansion valve until the frequency is less than or equal to the upper limit of the evaporation temperature of the compressor; and when the frequency of the chilled water pump is less than the lowest allowable frequency of the chilled water pump and the opening of the expansion valve is less than or equal to the minimum opening of the expansion valve, returning to the step of comparing the magnitude relation between the unit evaporation temperature of the water-cooling heat pump unit and the upper limit of the compressor evaporation temperature.

In a preferable aspect of the above control method of the present invention, the control method further includes: comparing the relationship between the unit exhaust pressure of the water-cooling heat pump unit and the high-pressure early warning pressure of the unit; when the frequency of the chilled water pump is less than the lowest allowable frequency of the chilled water pump and the opening degree of the expansion valve is greater than the minimum opening degree of the expansion valve, the unit evaporation temperature is adjusted by reducing the opening degree of the expansion valve until the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature, and the method comprises the following steps: when the frequency of the chilled water pump is smaller than the lowest allowable frequency of the chilled water pump and the opening degree of the expansion valve is larger than the minimum opening degree of the expansion valve, selectively adjusting the unit evaporation temperature by reducing the opening degree of the expansion valve until the unit evaporation temperature is smaller than or equal to the upper limit of the compressor evaporation temperature or adjusting the unit exhaust pressure by increasing the frequency of the cooling water pump of the water-cooling heat pump unit until the unit exhaust pressure is smaller than the high-pressure early warning pressure of the unit according to the comparison result of the unit exhaust pressure.

In a preferable embodiment of the above control method of the present invention, "selectively adjusting the evaporation temperature of the unit by decreasing the opening of the expansion valve until the evaporation temperature is less than or equal to the highest evaporation temperature of the compressor operation, or adjusting the exhaust pressure of the unit by increasing the frequency of the cooling water pump of the water-cooled heat pump unit until the exhaust pressure is less than the high-pressure warning pressure of the unit" according to the comparison result of the exhaust pressures of the unit includes the following steps: when the exhaust pressure of the unit is smaller than the high-pressure early warning pressure of the unit, the evaporation temperature of the unit is adjusted by reducing the opening of the expansion valve until the exhaust pressure is smaller than or equal to the upper limit of the evaporation temperature of the compressor; when the unit exhaust pressure is greater than or equal to the unit high-pressure early warning pressure, the unit exhaust pressure is adjusted by increasing the frequency of a cooling water pump of the water-cooling heat pump unit until the unit exhaust pressure is less than the unit high-pressure early warning pressure.

In a preferred embodiment of the above control method of the present invention, "adjusting the unit exhaust pressure by increasing the frequency of the cooling water pump of the water-cooled heat pump unit until the unit exhaust pressure is lower than the unit high-pressure warning pressure" includes the following steps: when the frequency of the cooling water pump is increased, the frequency of the cooling water pump is a preset value; and after the water-cooled heat pump unit operates for a preset time with the increased frequency of the cooling water pump, returning to the step of comparing the size relation between the unit exhaust pressure of the water-cooled heat pump unit and the unit high-pressure early warning pressure.

In a preferable embodiment of the above control method of the present invention, the "adjusting the unit evaporation temperature by reducing the frequency of the chilled water pump until the unit evaporation temperature is less than or equal to the maximum evaporation temperature of the compressor operation" includes the following steps: reducing the frequency of the chilled water pump by a preset value; and after the water-cooling heat pump unit is kept running for a preset time with the reduced frequency of the chilled water pump, returning to the step of comparing the size relationship between the unit evaporation temperature of the water-cooling heat pump unit and the upper limit of the compressor evaporation temperature.

In a preferable embodiment of the above control method of the present invention, the "adjusting the unit evaporation temperature by decreasing the opening degree of the expansion valve until it is less than or equal to the highest evaporation temperature of the compressor operation" includes the following steps: reducing the opening degree of the expansion valve by a preset value; and (3) after the water-cooling heat pump unit is kept running for a preset time length with the reduced opening degree of the expansion valve, returning to the step of comparing the size relation between the unit evaporation temperature of the water-cooling heat pump unit and the upper limit of the compressor evaporation temperature.

The control method of the water-cooling heat pump unit comprises the following steps: comparing the magnitude relation between the unit evaporation temperature of the water-cooling heat pump unit and the upper limit of the compressor evaporation temperature; and selectively adjusting the unit evaporation temperature until the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature or keeping the water cooling and heating pump unit to operate at the current cooling water pump frequency and the current freezing water pump frequency according to the comparison result.

According to the control method, different control strategies are adopted according to the comparison result of the size relation between the unit evaporation temperature and the upper limit of the compressor evaporation temperature, the unit evaporation temperature is controlled within the upper limit of the compressor evaporation temperature, the compressor is guaranteed to operate normally all the time, the service life of the compressor is guaranteed, and the normal operation of the water-cooling heat pump unit is guaranteed.

In another aspect, the present invention also provides a water-cooling heat pump unit, which includes a controller configured to execute the control method described above.

It should be noted that the water-cooled heat pump unit of the present invention has all the technical effects of the above control method, and those skilled in the art can obtain the control method without doubt according to the foregoing description, so that no further description is provided herein.

Drawings

FIG. 1 is a schematic structural diagram of a water-cooled heat pump unit according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of allowable operating temperature ranges of a compressor for a cold water heat pump unit;

FIG. 3 is a main control flow of the control method of the water-cooled heat pump unit of the present invention;

FIG. 4 is a detailed control flow chart of the control method of the water-cooling heat pump unit of the present invention.

Wherein, the one-to-one correspondence between component names and reference numbers in fig. 1 is:

1 compressor, 2 condenser, 3 evaporator, 4 expansion valve, 5 cooling tower, 6 cooling water pump,

7 chilled water pump, 8 low pressure sensor, 9 high pressure sensor.

Detailed Description

Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention.

For the convenience of understanding and brevity of description, the following description is provided in conjunction with the control method of the water-cooled heat pump unit, and the advantageous effects will not be repeated.

Referring to fig. 1, fig. 1 is a schematic structural diagram of an embodiment of a water-cooling heat pump unit of the present invention, wherein solid arrows in fig. 1 represent a flow direction of a refrigerant, hollow arrows represent a flow direction of chilled water, and line arrows represent a flow direction of cooling water.

In this embodiment, the water-cooled heat pump unit at least includes a compressor 1, a condenser 2, an evaporator 3, an expansion valve 4, a cooling tower 5, a cooling water pump 6, and a chilled water pump 7. The condenser 2 has a refrigerant flow path through which a refrigerant flows and a cooling water flow path through which cooling water flows, and the refrigerant flow path and the cooling water flow are independent from each other, but the refrigerant and the cooling water flowing through the refrigerant flow path and the cooling water flow in heat exchange with each other. Similarly, the evaporator 3 has a refrigerant flow path through which cooling water flows and a chilled water flow path through which chilled water flows, and the refrigerant flow path and the chilled water flow path are independent of each other, but the refrigerant and the chilled water flowing through both can exchange heat with each other.

The refrigerant flow paths of the compressor 1, the condenser 2, the expansion valve 4, and the evaporator 3 are connected by pipes to form a refrigerant circulation circuit. The cooling tower 5, the cooling water pump 6 and the cooling water flow path of the condenser 2 are connected by a pipeline to form a cooling water circulation loop. The chilled water flow path of the evaporator 3 and the chilled water pump 7 form a chilled water circulation loop with the end equipment heat exchanger on the user side through a pipeline.

When the water-cooling heat pump unit works, the compressor 1 sucks the low-temperature and low-pressure refrigerant gas agent of the evaporator 3, the refrigerant gas agent is compressed into high-temperature and high-pressure gas by the compressor 1, and the high-temperature and high-pressure gas is discharged to the condenser 2; in the condenser 2, the refrigerant gas with high temperature and high pressure exchanges heat with cooling water, and is condensed into refrigeration liquid with normal temperature and high pressure, and the cooling water after temperature rise is conveyed to a cooling tower 5 by a cooling water pump 6 and is recycled after air cooling; the refrigerant liquid with a certain supercooling degree is cooled and decompressed by an expansion valve 4 and then enters an evaporator 3; in the evaporator 3, the low-temperature and low-pressure refrigerant exchanges heat with the chilled water, absorbs the heat of the chilled water to become low-temperature and low-pressure refrigerant gas with a certain superheat degree, then is sucked into the compressor 1 by the compressor 1, starts a new cycle, and the chilled water passing through the evaporator 3 is cooled and cooled, is delivered to the end equipment heat exchanger by the chilled water pump 7, exchanges heat with indoor air, and continuously sends cold air out.

The compressor 1 is one of the core functional elements of the water-cooling heat pump unit, and the water-cooling heat pump unit is to ensure that the compressor 1 works within a specified temperature range when working, the meaning of the normal working temperature range of the compressor 1 is briefly illustrated below with reference to fig. 2, fig. 2 is a schematic diagram of the allowable working temperature range of the compressor for the cold water heat pump unit, wherein the abscissa represents the evaporation temperature of the compressor, and the ordinate represents the condensation temperature of the compressor.

Referring to fig. 2, when the water-cooling heat pump unit works, the compressor 1 can normally operate when the evaporating temperature and the condensing temperature of the compressor are within the temperature range indicated by the black frame, so that the normal operation of the water-cooling heat pump unit is ensured. For example, in fig. 2, the upper limit of the evaporating temperature of the compressor allowed by the normal operation of the compressor is 10 ℃, the lower limit of the evaporating temperature of the compressor allowed by the normal operation of the compressor 1 is-10 ℃, the upper limit of the condensing temperature of the compressor allowed by the normal operation of the compressor 1 is 50 ℃, and the lower limit of the condensing temperature of the compressor allowed by the normal operation of the compressor 1 is 20 ℃.

In the existing cold water heat pump unit, the protection of the temperature range of the normal operation of the compressor 1 is mainly realized by high-low pressure protection of the unit, the over-low temperature of the cooling water inlet and the low temperature of the chilled water outlet, wherein the high-pressure protection mainly protects the upper limit of the condensation temperature of the compressor, the low-pressure protection and the low temperature of the chilled water outlet mainly protect the lower limit of the evaporation temperature of the compressor, the over-low temperature of the cooling water inlet mainly protects the lower limit of the condensation temperature of the compressor 1, but the upper limit of the evaporation temperature of the compressor has no corresponding and effective protection. If the compressor 1 of the cold water heat pump unit exceeds the upper limit of the evaporation temperature of the compressor for a long time and is abnormally operated, the compressor 1 is in a high-power high-heating operation state, the service life of the compressor 1 is slightly influenced, and the condition that the motor of the compressor 1 is burnt out can be generated.

Therefore, the invention provides a control method of a cold water heat pump unit, which aims to control the unit evaporation temperature within the upper limit of the compressor evaporation temperature and avoid the problems caused by the fact that the compressor does not operate in an out-of-range mode.

Referring to fig. 3, the control method of the cold water heat pump unit of the present invention includes the following main steps:

s1, comparing the relationship between the unit evaporation temperature of the water-cooling heat pump unit and the upper limit of the compressor evaporation temperature;

and S2, selectively adjusting the unit evaporation temperature until the unit evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature or keeping the water cooling and heating pump unit to operate at the current cooling water pump frequency and the current freezing water pump frequency according to the comparison result.

According to the control method of the cold water heat pump unit, different control strategies are adopted according to the comparison result of the magnitude relation between the unit evaporation temperature and the upper limit of the compressor evaporation temperature, the unit evaporation temperature is controlled within the upper limit of the compressor evaporation temperature, the compressor is guaranteed to run normally all the time, the service life of the compressor is guaranteed, and the normal running of the water cooling heat pump unit is guaranteed.

For better understanding and simplicity of description, the control method of the cold water heat pump unit of the present invention will be described in detail below with reference to fig. 4 by taking the cold water heat pump unit executing the control method as an example. FIG. 4 is a detailed control flow chart of the control method of the water-cooling heat pump unit of the present invention. The cold water heat pump unit comprises a controller, and the controller is configured to execute the control method of the invention.

Referring to fig. 4, the control method of the hot and cold water pump unit of the present embodiment includes the following detailed steps:

s10, comparing the operation time t of the compressor with the maximum allowable out-of-range operation time t of the compressor_smaxThe magnitude relationship between them; if t is>t_smax(i.e., the compressor operation time period is longer than the maximum compressor operation allowed out-of-range time period), step S11 is executed, if t ≦ tt_smax(i.e., the operation time period of the compressor is less than or equal to the maximum operation time period of the compressor over the range), the process returns to S10.

Since the operation range of the compressor is easily out of the specified temperature range at the initial starting stage of the compressor, and the compressor is not damaged substantially due to the out-of-range abnormality in a short period of time, for this reason, the maximum allowable out-of-range operation time of the compressor is preset in this embodiment, and the step S11 is executed when the operation time of the compressor exceeds the maximum allowable out-of-range operation time of the compressor, so as to ensure the normal starting of the compressor. Of course, the control method of the present invention may omit step S10 and directly perform step S11.

S11, comparing the evaporation temperature T of the unit_zAnd upper limit of compressor evaporating temperature T_zsmaxThe magnitude relationship between them.

It should be noted that, referring to fig. 1, a low-pressure sensor 8 is installed on a pipeline at a suction port of the compressor, and the low-pressure sensor 8 is used for detecting a pressure value at the suction port of the compressor, and then finding a saturation temperature of the corresponding refrigerant according to the pressure value, where the saturation temperature is an evaporation temperature of the unit.

In the present embodiment, the control method selectively adjusts the unit evaporating temperature until it is less than or equal to the upper limit of the compressor evaporating temperature, or keeps the water cooling and heating pump unit operating at the current cooling water pump frequency and the current freezing water pump frequency, according to the comparison result of step S11.

The current cooling water pump frequency refers to the current frequency of a cooling water pump of the water-cooling heat pump unit, and similarly, the current chilled water pump frequency refers to the current frequency of a chilled water pump of the water-cooling heat pump unit. In this embodiment, the cooling water pump and the chilled water pump are frequency conversion water pumps, and the frequency and the water flow of the frequency conversion water pump are in positive correlation, that is, the higher the frequency of the frequency conversion water pump is, the higher the water flow pumped by the frequency conversion water pump is.

Specifically, when T is_z>T_zsmaxWhen the temperature of the unit is higher than the upper limit of the evaporating temperature of the compressor, the evaporating temperature of the unit is adjusted until the evaporating temperature of the unit is lower than or equal to the upper limit of the evaporating temperature of the compressor, and when T is higher than the upper limit of the evaporating temperature of the compressor_z≤T_zsmaxTime (machine in time)The group evaporation temperature is less than or equal to the upper limit of the compressor evaporation temperature) to perform step S210, i.e., to keep the water-cooling heat pump unit running at the current cooling water pump frequency and the current chilled water pump frequency.

When T is_z>T_zsmaxThe adjusting method for adjusting the evaporation temperature of the unit until the evaporation temperature is less than or equal to the upper limit of the evaporation temperature of the compressor comprises the following steps:

s20, comparing the frequency f of the chilled water pump_dAnd the lowest frequency f of the operation of the chilled water pump_dsminThe magnitude relationship between them; and according to the comparison result, selectively adjusting the evaporation temperature of the unit by reducing the frequency of the chilled water pump or reducing the opening degree of the expansion valve until the evaporation temperature is less than or equal to the upper limit of the evaporation temperature of the compressor.

Specifically, when the comparison result of step S20 is: f. of_d≥f_dsminWhen the frequency of the chilled water pump is greater than or equal to the lowest allowable frequency of the chilled water pump, the evaporation temperature of the unit is adjusted by reducing the frequency of the chilled water pump until the frequency is less than or equal to the upper limit of the evaporation temperature of the compressor.

The frequency of a freezing water pump of the cold water heat pump unit is reduced, the flow of the freezing water is reduced, the temperature difference between the inlet water and the outlet water of the freezing water is increased, and the evaporation temperature of the unit is reduced.

With continued reference to fig. 4, in the present embodiment, the adjusting method for "adjusting the evaporating temperature of the unit by reducing the frequency of the chilled water pump until the evaporating temperature is less than or equal to the upper limit of the evaporating temperature of the compressor" includes the following steps:

s21, reducing the frequency of the chilled water pump by a preset value;

and S22, after the water cooling and heating pump unit is kept to operate for a preset time at the reduced frequency of the chilled water pump, returning to the step S11, and continuously comparing the size relation between the unit evaporation temperature and the upper limit of the compressor evaporation temperature.

In this embodiment, the purpose of step S20 is to prevent the problem that the frequency of the chilled water pump is forcibly reduced to cause damage to the chilled water pump when the frequency of the chilled water pump is already lower than the lowest allowable frequency of the chilled water pump, so as to ensure the chilled water pump to operate normally.

In addition, the steps S21 and S22 are to reduce the frequency of the chilled water pump in a relatively gentle rhythm, so as to prevent the problem of high-low pressure imbalance in the unit caused by the instantaneous large change of the high-low pressure side pressure of the compressor, and ensure the normal operation of the chilled water heat pump unit. And reducing a specific numerical value in a preset value of the frequency of the chilled water pump so as not to unbalance the high pressure and the low pressure of the unit after adjustment.

When the comparison result of step S20 is: when f is_d<f_dsmin(namely the frequency of the chilled water pump is less than the lowest allowable frequency of the chilled water pump), the evaporation temperature of the unit is adjusted by reducing the opening degree of the expansion valve until the evaporation temperature is less than or equal to the upper limit of the evaporation temperature of the compressor.

In this embodiment, the adjusting method for adjusting the evaporation temperature of the unit by reducing the opening of the expansion valve until the evaporation temperature is less than or equal to the upper limit of the evaporation temperature of the compressor includes the following steps:

s23, comparing opening K of expansion valve with minimum opening K of expansion valve_sminThe magnitude relationship between them; when the frequency of the chilled water pump is less than the lowest allowable frequency of the chilled water pump, selectively adjusting the evaporation temperature of the unit by reducing the opening degree of the expansion valve until the evaporation temperature is less than or equal to the upper limit of the evaporation temperature of the compressor according to the comparison result of the step S23, or returning to the step S11.

Specifically, when f_d<f_dsminAnd K is>K_sminTime (the opening K of the expansion valve is larger than the minimum opening K of the expansion valve_smin) The unit evaporation temperature is adjusted by reducing the opening degree of the expansion valve until it is less than or equal to the upper limit of the compressor evaporation temperature, otherwise, the process returns to step S11.

The step S23 is provided in this embodiment to prevent the expansion valve from being damaged due to the forced reduction of the opening degree of the expansion valve when the opening degree of the expansion valve has reached the minimum opening degree, and finally the cold water heat pump unit is stopped.

With continued reference to fig. 4, the control method of the present embodiment further includes the following steps:

s24, comparing unit exhaust pressure P_pHigh-pressure early warning pressure P of harmony unit_smaxThe magnitude relationship between them.

Referring to fig. 1, a high-pressure sensor 9 is installed on an exhaust side pipeline of a compressor of the water-cooling heat pump unit, the high-pressure sensor 9 is used for detecting a pressure value at an exhaust port of the compressor, and then a saturation temperature of a corresponding refrigerant is found according to the pressure value, wherein the saturation temperature is a unit condensation temperature.

When f is_d<f_dsminAnd K is>K_sminAnd then, according to the comparison result of the step S24, selectively adjusting the evaporation temperature of the unit by reducing the opening of the expansion valve until the evaporation temperature is less than or equal to the upper limit of the evaporation temperature of the compressor, or adjusting the exhaust pressure of the unit until the exhaust pressure is less than the high-pressure early warning pressure of the unit.

Specifically, when f_d<f_dsmin，K>K_sminAnd P is_p<P_smaxAnd when the temperature is lower than the upper limit of the evaporation temperature of the compressor, the evaporation temperature of the unit is adjusted by reducing the opening degree of the expansion valve until the temperature is lower than or equal to the upper limit of the evaporation temperature of the compressor.

The adjusting method for adjusting the evaporation temperature of the unit by reducing the opening of the expansion valve until the evaporation temperature is less than or equal to the upper limit of the evaporation temperature of the compressor specifically comprises the following steps:

s25, reducing the opening of the expansion valve by a preset value;

and S26, after the water cooling and heating pump unit is kept running for a preset time length with the reduced opening degree of the expansion valve, returning to the step S11.

Along with the reduction of the opening degree of the expansion valve, the unit evaporation temperature of the water-cooling heat pump unit is reduced. Further, the steps S25 and S26 are to reduce the opening of the expansion valve in a relatively gentle rhythm, so as to prevent the problem of high-low pressure imbalance in the chiller caused by the instantaneous large change of the high-low pressure side pressure of the compressor, and to ensure the normal operation of the chilled water heat pump set.

When f is_d<f_dsmin，K>K_sminAnd P is_p≥P_smaxAnd when the pressure of the exhaust of the unit is regulated by increasing the frequency of the cooling water pump until the pressure is smaller than the high-pressure early warning pressure of the unit.

With continued reference to fig. 4, in this embodiment, before adjusting the unit exhaust pressure by increasing the frequency of the cooling water pump until it is less than the unit high-pressure warning pressure, the control method further includes the following steps:

s27, comparing the frequency f of the cooling water pump_qAnd cooling water pump allowed maximum frequency f_qsamxThe magnitude relationship between them.

When f is_q<f_qsminWhen the pressure of the unit is lower than the high-pressure early warning pressure of the unit, the frequency of the cooling water pump is increased to adjust the exhaust pressure of the unit; when f is_q≥f_qsminIf so (i.e., the cooling water pump frequency is greater than or equal to the cooling water pump allowable maximum frequency), the process returns to step S24.

The step S27 is provided in this embodiment to prevent the cooling water pump from being damaged due to the forced increase of the frequency of the cooling water pump when the frequency of the cooling water pump is the highest allowable frequency of the water pump.

More specifically, when the frequency of the cooling water pump is less than the highest allowable frequency of the cooling water pump, the adjusting method for adjusting the unit exhaust pressure by increasing the frequency of the cooling water pump until the unit exhaust pressure is less than the unit high-pressure early warning pressure comprises the following steps:

s28, increasing the frequency of the cooling water pump by a preset value;

and S29, after the water cooling and heating pump unit is kept running for a preset time length at the increased cooling water pump frequency, returning to the step S24.

The frequency of a cooling water pump of the cold water heat pump unit is increased, the water flow of cooling water is increased, the temperature difference of inlet and outlet water of the cooling water is reduced, the condensation temperature is reduced, and the exhaust pressure of the unit is reduced.

Similarly, the purpose of steps S28 and S29 is to increase the frequency of the cooling water pump with a relatively moderate pace, so as to prevent the problem of high-low pressure imbalance in the chiller caused by the instantaneous large change of the high-low pressure side pressure of the compressor, and to ensure the normal operation of the chilled water heat pump set.

So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.