A dual-source heat pump system for both hot and cold water supply and its control method

Abstract

This invention provides a dual-source heat pump system and control method for both hot and cold water supply. The system includes a water source heat pump unit, with its cold end connected to a plate heat exchanger and its hot end connected to a hot water storage tank. The plate heat exchanger is connected to an air compressor. The heat generated by the heat pump raises the water temperature in the hot water storage tank to meet heating demands. Simultaneously, the heat pump unit control mode is optimized to avoid excessively low cold-end outlet water temperatures due to excessive cooling, which could affect the equipment. It also avoids frequent start-stop cycles when the heat pump approaches the target temperature. The control process incorporates assessments of the heat pump unit's energy efficiency, ensuring efficient operation while meeting process requirements.

Description

Technical Field

[0001] This invention relates to a dual-source heat pump system for both hot and cold water supply and its control method, belonging to the field of heat pump technology. Background Technology

[0002] Compressed air is essential for all processes in cigarette production in cigarette factories, and the air compressor that produces compressed air generates a lot of heat during operation.

[0003] Most air compressor cooling systems currently send hot water, which has been heat-exchanged by the equipment, to a cooling tower, where the heat in the water is carried away through heat exchange with the outside air.

[0004] As a result, the waste heat generated during equipment operation is directly discharged without being effectively utilized, leading to a large waste of thermal energy and a low utilization rate of air compressor resources. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a dual-source heat pump system for both hot and cold water supply and a control method to solve the problems of large amounts of heat energy wastage and low resource utilization during the use of air compressors in the prior art.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0007] In a first aspect, the present invention provides a dual-source heat pump system for both cold and hot water supply, including a water source heat pump unit, wherein the cold end is connected to a plate heat exchanger and the hot end is connected to a hot water storage tank.

[0008] The plate heat exchanger is connected to the air compressor end.

[0009] Secondly, the present invention provides a control method for the above-mentioned dual-source heat pump system, comprising:

[0010] Based on the current cold end outlet water temperature Tc during the operation of the water source heat pump unit -out Target temperature of cold end outlet water Tc -set The relationship between the temperature difference eT and the cold end outlet water protection is used to adjust the calculation method of the load U of the water source heat pump unit, and the load U of the water source heat pump unit is calculated.

[0011] The operating condition U under the lowest energy efficiency index is calculated based on the pre-obtained heat pump energy efficiency curve. l-set ;

[0012] When the calculated load U of the water source heat pump unit is less than U l-set At the same time, the water source heat pump unit should be kept at the low load limit.

[0013] When the operating load U of the water source heat pump unit equals U l-setFurthermore, the outlet water temperature at the cold water end is still trending downwards, or T c-out <T c-set When necessary, the water source heat pump unit should be shut down.

[0014] Furthermore, the current outlet water temperature T at the cold end during the operation of the water source heat pump unit... c-out Target temperature T of cold end outlet water c-set and cold end outlet water protection temperature difference e T The relationship between these factors, and the method for calculating the load U of the water source heat pump unit, includes:

[0015] When T c-out -T c-set ≥e T At that time, the heat pump unit uses the hot end set temperature T h-set To control the target value, the hot end outlet water temperature T is used. h-out Perform PID calculations on the feedback value, and denote the result as U. h-pid At this time, the heat pump load U is:

[0016] U = U h-pid

[0017] When T c-out -T c-set <e T At that time, the control target of the heat pump unit was changed to the cold end set temperature T. c-set The feedback value is the cold end outlet water temperature T. c-out Perform PID calculations, and record the result as U. c-pid At this time, the heat pump load U is:

[0018] U = a·U c-pid

[0019] Where 'a' is the scaling factor, which is the rate of change (ROC) of the decreasing trend of the cold end outlet water temperature. c Sure.

[0020] Furthermore, the method for calculating the rate of change of the decreasing trend of the cold end outlet water temperature includes:

[0021] Select a time window of fixed length k, collect k temperature values ​​within the window, and calculate their mean. The window slides backward at a distance of m; selecting n windows will yield the desired result. Furthermore, the temperature change trend can be obtained through comparison;

[0022] The rate of change of the cold end outlet water temperature is calculated based on the temperature change trend. The calculation formula is as follows:

[0023] Furthermore, the operating condition U under the minimum energy efficiency index l-setThe system is updated periodically based on the actual operating conditions of the water source heat pump unit.

[0024] Thirdly, the present invention provides a control device, comprising:

[0025] The load calculation module for the water source heat pump unit is used to calculate the current outlet water temperature T at the cold end during the operation of the water source heat pump unit. c-out Target temperature T of cold end outlet water c-set and cold end outlet water protection temperature difference e T The relationship between the two factors is used to adjust the calculation method of the load U of the water source heat pump unit, and the load U of the water source heat pump unit is calculated.

[0026] The calculation module is used to calculate the operating condition U under the lowest energy efficiency index based on the pre-acquired heat pump energy efficiency curve. l-set ;

[0027] The first control module is used when the calculated load U of the water source heat pump unit is less than U0. l-set At the same time, the water source heat pump unit should be kept at the low load limit.

[0028] The second control module is used when the operating load U of the water source heat pump unit equals U l-set Furthermore, the outlet water temperature at the cold water end is still trending downwards, or T c-out <T c-set When necessary, the water source heat pump unit should be shut down.

[0029] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0030] This invention provides a dual-source heat pump system and control method, including a water source heat pump unit. The cold end of the heat pump is connected to a plate heat exchanger, and the hot end is connected to a hot water storage tank. The plate heat exchanger is connected to an air compressor. The heat generated by the heat pump raises the water temperature in the hot water storage tank to meet heating demands. Simultaneously, the heat pump unit control mode is optimized to avoid excessively low cold-end water temperatures affecting the equipment due to excessive cooling, and to prevent frequent start-stop cycles when the heat pump approaches the target temperature. The control process incorporates assessment of the heat pump unit's energy efficiency, ensuring efficient operation while meeting process requirements. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a dual-source heat pump system for both hot and cold water supply, provided as an embodiment of the present invention. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0033] Example 1

[0034] Figure 1 This is a schematic diagram of a dual-source heat pump system for both hot and cold water supply provided in this embodiment. Figure 1 As shown, the dual-source heat pump system includes a water source heat pump unit, whose cold end is connected to a plate heat exchanger and whose hot end is connected to a hot water storage tank; the plate heat exchanger is connected to the air compressor end.

[0035] The cold end of the water source heat pump unit is connected to a plate heat exchanger and exchanges heat with the air compressor cooling water. The hot end is connected to a hot water storage tank. The heat generated by the heat pump increases the water temperature in the hot water storage tank to meet the heating demand, thereby improving the overall energy efficiency of the waste heat recovery system of the air compressor equipment and increasing the utilization rate of air compressor resources.

[0036] Example 2

[0037] This embodiment describes a control method for a dual-source heat pump system with both hot and cold water supply according to Embodiment 1, including:

[0038] Based on the current cold end outlet water temperature T during the operation of the water source heat pump unit c-out Target temperature T of cold end outlet water c-set and cold end outlet water protection temperature difference e T The relationship between the two factors is used to adjust the calculation method of the load U of the water source heat pump unit, and the load U of the water source heat pump unit is calculated.

[0039] The operating condition U under the lowest energy efficiency index is calculated based on the pre-obtained heat pump energy efficiency curve. l-set ;

[0040] When the calculated load U of the water source heat pump unit is less than U l-set At the same time, the water source heat pump unit should be kept at the low load limit.

[0041] When the operating load U of the water source heat pump unit equals U l-set Furthermore, the outlet water temperature at the cold water end is still trending downwards, or T c-out <T c-set When necessary, the water source heat pump unit should be shut down.

[0042] The control method for a dual-source heat pump system (cold and hot water supply) provided in this embodiment involves the following steps in its application:

[0043] S1: Define the current outlet water temperature at the cold end of the water source heat pump unit as T. c-out The current outlet water temperature at the hot end of the water source heat pump unit is T. h-out The target outlet water temperature of the water source heat pump unit is T. c-set The target outlet water temperature of the water source heat pump unit is T. h-set The cold end outlet water protection temperature difference of the water source heat pump unit is e T;

[0044] S2: The system operates on T c-out The changing trend is determined in real time to obtain the temperature change trend;

[0045] S3: Based on the T process during the operation of the water source heat pump unit c-out T c-set and e T The calculation method for the load U of a water source heat pump unit under the relationship between operating conditions;

[0046] S4: Define the minimum energy efficiency index (COP) for water source heat pump units. l-set The operating condition U under the lowest energy efficiency index is calculated based on the heat pump energy efficiency curve. l-set ;

[0047] S5: When the calculated load U of the water source heat pump unit is less than U l-set At that time, the water source heat pump unit maintains operation at the low load limit; when the operating load of the water source heat pump unit is U... l-set Furthermore, the outlet water temperature at the cold water end is still trending downwards or T c-out <T c-set At that time, the water source heat pump unit stopped operating;

[0048] The energy efficiency curve of a heat pump can be obtained through existing experimental measurements, data processing, modeling, and verification adjustments.

[0049] In this embodiment, the method for obtaining the temperature change trend in S2 is as follows:

[0050] Select a time window of fixed length k, collect k temperature values ​​within the window, and calculate their average. The window slides backward at a distance of m, and n windows can be selected to obtain the temperature change trend.

[0051] In this embodiment, during the operation of the water source heat pump unit, T c-out T c-set and e T The relationship conditions include:

[0052] Operating Condition 1: When T c-out -T c-set ≥e T At that time, the heat pump unit uses the hot end set temperature T h-set To control the target value, the hot end outlet water temperature T is used. h-out Perform PID calculations on the feedback value, and denote the result as U. h-pid At this time, the heat pump load U is:

[0053] U = U h-pid

[0054] Working condition 2: When t c-out -T c-set <e T At that time, the control target of the heat pump unit was changed to the cold end set temperature T. c-set The feedback value is the cold end outlet water temperature T. c-out Perform PID calculations, and record the result as U. c-pid At this time, the heat pump load U is:

[0055] U = a·U c-pid

[0056] Where 'a' is the scaling factor, which is the rate of change (ROC) of the decreasing trend of the cold end outlet water temperature. c Sure, By adjusting the load of the water source heat pump unit by scaling factor 'a', the downward trend of temperature is reduced, thereby keeping the cold end outlet water temperature in a stable state and preventing it from continuously decreasing due to excessive cooling capacity.

[0057] The minimum operating load limit of the water source heat pump unit is calculated based on the set minimum energy efficiency index and energy efficiency curve, and is periodically updated according to the actual operating conditions of the unit; when the calculated heat pump load is less than the set minimum load limit (U < U l-set The heat pump remains at its lowest operating limit; when the heat pump operating load U has reached its lowest limit (U... l-set And when the cold end outlet water temperature is still decreasing, or the cold end outlet water temperature is lower than the set temperature (T) c-out <T c-set The heat pump unit stops operating, thereby optimizing the control mode of the water source heat pump unit, avoiding the impact of excessively low cold end water temperature caused by excessive cooling, and also avoiding frequent start-stop of the heat pump when it approaches the target temperature; at the same time, the energy efficiency of the heat pump unit is judged in the control process, ensuring that the equipment operates efficiently while meeting process requirements.

[0058] In this embodiment, U in S4 l-set The data is updated periodically based on the actual operating conditions of the water source heat pump unit to ensure the accuracy of the calculations.

[0059] Example 3

[0060] This embodiment provides a control device, including:

[0061] The load calculation module for the water source heat pump unit is used to calculate the current outlet water temperature T at the cold end during the operation of the water source heat pump unit. c-out Target temperature T of cold end outlet water c-set and cold end outlet water protection temperature difference e T The relationship between the two factors is used to adjust the calculation method of the load U of the water source heat pump unit, and the load U of the water source heat pump unit is calculated.

[0062] The calculation module is used to calculate the operating condition U under the lowest energy efficiency index based on the pre-acquired heat pump energy efficiency curve. l-set ;

[0063] The first control module is used when the calculated load U of the water source heat pump unit is less than U0. l-set At the same time, the water source heat pump unit should be kept at the low load limit.

[0064] The second control module is used when the operating load U of the water source heat pump unit equals U l-set Furthermore, the outlet water temperature at the cold water end is still trending downwards, or T c-out <T c-set When necessary, the water source heat pump unit should be shut down.

[0065] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A control method for a dual-source heat pump system (cold and hot water supply), the system comprising: A water source heat pump unit, wherein the cold end is connected to a plate heat exchanger and the hot end is connected to a hot water storage tank, and the plate heat exchanger is connected to an air compressor, characterized in that the control method includes: Based on the current outlet water temperature at the cold end during the operation of the water source heat pump unit Target temperature of cold end outlet water and cold end outlet water protection temperature difference The relationship between the loads is adjusted, the calculation method for the load U of the water source heat pump unit is adjusted, and the load U of the water source heat pump unit is calculated, including: when At that time, the heat pump unit uses the hot end set temperature. To control the target value, the hot end outlet water temperature is used. Perform PID calculations on the feedback value, and record the result as follows: At this time, the heat pump load for: when At that time, the control target of the heat pump unit was changed to the cold end set temperature. The feedback value is the cold end outlet water temperature. Perform PID calculation, and record the result as follows: At this time, the heat pump load for: Where 'a' is the scaling factor, which is the rate of change of the decreasing trend of the cold end outlet water temperature. Sure; The operating conditions under the lowest energy efficiency index are calculated based on the pre-obtained heat pump energy efficiency curve. ; When the calculated load U of the water source heat pump unit is less than At the same time, the water source heat pump unit is controlled to operate at the low load limit; When the operating load U of the water source heat pump unit is equal to Furthermore, the temperature of the cold water outlet is still trending downwards, or When necessary, the water source heat pump unit should be shut down.

2. The control method for the dual-source heat pump system with both hot and cold water supply according to claim 1, characterized in that, The method for calculating the rate of change of the decreasing trend of the cold end outlet water temperature includes: Select a time window of fixed length k, collect k temperature values ​​within the window, and calculate their mean. The window slides backward at a distance of m, and selecting n windows will yield the result. Then, by comparison, the trend of temperature change can be obtained; The rate of change of the cold end outlet water temperature is calculated based on the temperature change trend. The calculation formula is as follows: .

3. The control method for the dual-source heat pump system with both hot and cold water supply according to claim 1, characterized in that, Operating conditions under the minimum energy efficiency index The system is updated periodically based on the actual operating conditions of the water source heat pump unit.

4. A control device for implementing the control method of the dual-source heat pump system for cold and hot water supply as described in any one of claims 1-3, characterized in that, include: The load calculation module for the water source heat pump unit is used to calculate the current outlet water temperature at the cold end during the operation of the water source heat pump unit. Target temperature of cold end outlet water and cold end outlet water protection temperature difference The relationship between the two factors is used to adjust the calculation method of the load U of the water source heat pump unit, and the load U of the water source heat pump unit is calculated. The calculation module is used to calculate the operating conditions under the lowest energy efficiency index based on the pre-acquired heat pump energy efficiency curve. ; The first control module is used when the calculated load U of the water source heat pump unit is less than... At the same time, the water source heat pump unit is controlled to operate at the low load limit; The second control module is used when the operating load U of the water source heat pump unit is equal to... Furthermore, the temperature of the cold water outlet is still trending downwards, or When the time comes, the water source heat pump unit will stop operating.

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