Heat recovery refrigeration units and their control methods

Abstract

This invention discloses a heat recovery refrigeration unit and its control method. The heat recovery refrigeration unit includes a compressor, a heat recovery unit, a condenser, and an evaporator connected in sequence. A first branch and a second branch are connected in parallel between the heat recovery unit and the condenser. A pressure maintaining valve is installed on the first branch, and a first switching valve is installed on the second branch. When heat recovery is required, the first switching valve is opened, and the pressure maintaining valve is opened. The pressure within the heat recovery unit is adjusted by the pressure maintaining valve to regulate the hot water supply temperature. This invention solves the problem of low hot water supply temperature in existing heat recovery units, effectively utilizing waste heat to meet hot water demand while achieving energy conservation and environmental protection.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, and more specifically, to a heat recovery refrigeration unit and its control method. Background Technology

[0002] During cooling operation, screw chillers release high-temperature, high-pressure refrigerant gas from the compressor, which condenses and releases heat in the condenser. In conventional chillers, this condensation heat is typically discharged into the surrounding environment via cooling towers or cooling fans. This represents a significant waste for heat-demanding locations such as hotels, factories, and hospitals, and also contributes to environmental pollution. Heat recovery technology addresses this by recovering and reusing the substantial amount of waste heat discharged from the chiller during operation, serving as a final or primary heat source for the user.

[0003] When the gaseous refrigerant flows from the compressor into the condenser, it is in a superheated state. Partial heat recovery involves recycling this heat. A heat exchanger is added between the compressor and the conventional condenser to extract heat from the superheated refrigerant. In this type of heat recovery, only superheat is recovered. Water is exchanged on one side, and the refrigerant discharged from the compressor is on the other. The amount of hot water provided is small, or the hot water supply temperature is low and uncontrollable. When using refrigerants with low exhaust superheat and low sensible heat (e.g., R134a) for partial heat recovery, the partial heat recovery water temperature is greatly affected by the condensing temperature, the hot water supply temperature is low, and the recovered residual heat is also relatively small, failing to meet the heat recovery temperature requirements.

[0004] There is currently no effective solution to the problem of low hot water supply temperature in heat recovery devices in related technologies. Summary of the Invention

[0005] This invention provides a heat recovery refrigeration unit and its control method to at least solve the problem of low hot water supply temperature in heat recovery units in the prior art.

[0006] To address the aforementioned technical problems, according to one aspect of the present invention, a heat recovery refrigeration unit is provided, comprising: a compressor, a heat recovery unit, a condenser, and an evaporator connected in sequence; a first branch and a second branch connected in parallel are provided between the heat recovery unit and the condenser, a pressure maintaining valve is provided on the first branch, and a first switching valve is provided on the second branch. When heat recovery is required, the first switching valve is opened, and the pressure maintaining valve is opened, thereby adjusting the pressure inside the heat recovery unit to regulate the hot water supply temperature.

[0007] Furthermore, when heat recovery is not required, the pressure maintaining valve is closed and the first switching valve is closed, making the heat recovery unit and the condenser a single unit, which is then used as a condenser.

[0008] Furthermore, the pressure maintaining valve includes a pressure inlet, a pressure outlet, and a pressure balancing port. The pressure inlet and pressure outlet are located on the first branch, and the pressure balancing port is used to control the opening pressure of the pressure maintaining valve in order to regulate the pressure inside the heat recovery unit.

[0009] Furthermore, the pressure balancing port is connected to the condenser through a third branch. A second switching valve is also installed on the third branch to control the opening and closing of the third branch. When the third branch is connected, the pressure inside the heat recovery unit is regulated by the pressure of the condenser.

[0010] Furthermore, the pressure balancing port is also connected to the evaporator via a fourth branch, wherein the third and fourth branches are set in parallel; a third switching valve is also installed on the fourth branch to control the opening and closing of the fourth branch. When the fourth branch is connected, the pressure in the heat recovery unit is regulated by the pressure of the evaporator.

[0011] According to another aspect of the present invention, a control method for a heat recovery refrigeration unit is provided, applied to the heat recovery refrigeration unit as described above. The method includes: detecting whether heat recovery is required in the heat recovery refrigeration unit; when heat recovery is required, adjusting the pressure inside the heat recovery unit through a pressure maintaining valve to adjust the hot water supply temperature; when heat recovery is not required, controlling the heat recovery unit and the condenser to become one unit and be used as a condenser.

[0012] Furthermore, regulating the pressure within the heat recovery unit via the pressure maintaining valve includes: controlling the first switching valve to open and controlling the pressure balance port of the heat recovery unit to open; controlling the heat recovery unit and the condenser to become one unit includes: controlling the first switching valve to close and controlling the pressure balance port of the heat recovery unit to close.

[0013] Furthermore, controlling the opening of the pressure balance port of the heat recovery unit includes: acquiring the heat recovery return water temperature and the cooling water outlet temperature, calculating the temperature difference between the heat recovery return water temperature and the cooling water outlet temperature; and controlling the opening of the pressure balance port based on the temperature difference.

[0014] Furthermore, the pressure balance port is opened according to the temperature difference control, including: when the temperature difference is greater than a preset threshold, controlling the second switch valve to close and the third switch valve to open; when the temperature difference is less than or equal to the preset threshold, controlling the second switch valve to open and the third switch valve to close.

[0015] According to another aspect of the present invention, a storage medium containing computer-executable instructions is provided, which, when executed by a computer processor, are used to perform the heat recovery refrigeration unit control method described above.

[0016] This invention provides a solution for intelligently controlling the hot water supply temperature. A heat recovery unit is installed on the heat recovery chiller, and a pressure maintaining valve is installed between the heat recovery unit and the condenser. This valve is used to adjust the heat recovery pressure of the heat recovery unit when heat recovery is needed, thereby regulating the hot water supply temperature. A first switching valve is also provided to disconnect when heat recovery is needed, allowing the pressure maintaining valve to regulate the pressure within the heat recovery unit. By adding a pressure maintaining valve at the outlet of the heat recovery unit to control and regulate the condensing pressure, the problem of low hot water supply temperature in the heat recovery system is solved, the hot water supply temperature of the heat recovery system is increased, waste heat is effectively utilized, energy is saved and environmentally friendly, and user needs are met. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an optional structure of a heat recovery refrigeration unit according to an embodiment of the present invention; Figure 2 This is a schematic diagram of another optional structure of the heat recovery refrigeration unit according to an embodiment of the present invention; Figure 3 This is an optional flowchart of a heat recovery refrigeration unit control method according to an embodiment of the present invention; Figure 4 This is another optional flowchart of the heat recovery refrigeration unit control method according to an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. Compressor; 2. Heat recovery unit; 3. Condenser; 4. Evaporator; 5. Pressure maintaining valve; 6. First switching valve; 7. Second switching valve; 8. Third switching valve; 9. Throttling device. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0021] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0022] It should be understood that although the terms first, second, third, etc., may be used to describe controllers in embodiments of the present invention, these controllers should not be limited to these terms. These terms are only used to distinguish controllers connected to different devices. For example, without departing from the scope of embodiments of the present invention, a first controller may also be referred to as a second controller, and similarly, a second controller may also be referred to as a first controller.

[0023] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0024] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0025] The optional embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0026] Example 1 In a preferred embodiment 1 of the present invention, a heat recovery refrigeration unit is provided, specifically... Figure 1 This diagram illustrates one possible structural design of the unit, such as... Figure 1 As shown, the unit includes: The compressor 1, heat recovery unit 2, condenser 3, and evaporator 4 are connected in sequence. A first branch and a second branch are connected in parallel between the heat recovery unit 2 and the condenser 3. A pressure maintaining valve 5 is installed on the first branch, and a first switching valve 6 is installed on the second branch. When heat recovery is required, the first switching valve 6 is opened and the pressure maintaining valve 5 is opened. The pressure inside the heat recovery unit 2 is adjusted by the pressure maintaining valve 5 to regulate the hot water supply temperature.

[0027] When heat recovery is not required, the pressure maintaining valve 5 is closed and the first switching valve 6 is closed, making the heat recovery unit 2 and the condenser 3 integrated and used as the condenser 3. At this time, the heat recovery unit also participates in the refrigerant circulation and plays a role. Furthermore, the above scheme does not require shielding or short-circuiting the heat recovery unit when there is no need for heat recovery, thus improving the utilization value of the heat recovery unit.

[0028] The above embodiments provide a solution for intelligently controlling the hot water supply temperature. A heat recovery unit is installed on the heat recovery chiller, and a pressure maintaining valve is installed between the heat recovery unit and the condenser. This valve is used to adjust the heat recovery pressure of the heat recovery unit when heat recovery is needed, thereby regulating the hot water supply temperature. A first switching valve is also provided to disconnect when heat recovery is needed, allowing the pressure within the heat recovery unit to be adjusted via the pressure maintaining valve. By adding a pressure maintaining valve at the outlet of the heat recovery unit to control and regulate the condensing pressure, the problem of low hot water supply temperature in the heat recovery system is solved, the hot water supply temperature of the heat recovery system is increased, waste heat is effectively utilized, energy is saved and environmentally friendly, and user needs are met.

[0029] In a preferred embodiment of the present invention, the pressure maintaining valve 5 includes a pressure inlet, a pressure outlet, and a pressure balancing port. The pressure inlet and pressure outlet are located on the first branch. The pressure balancing port is used to control the opening pressure of the pressure maintaining valve 5 to regulate the pressure inside the heat recovery unit 2. The balancing port of the pressure balancing valve is externally connected to a balancing pipe. The flow rate between the inlet and outlet is adjusted by the pressure in the balancing pipe, thereby controlling the pressure inside the heat recovery unit 2.

[0030] As an optional implementation, the pressure balancing port is connected to the condenser 3 through a third branch. A second switching valve 7 is also provided on the third branch to control the opening and closing of the third branch. When the third branch is connected, the pressure in the heat recovery unit 2 is regulated by the pressure of the condenser 3.

[0031] Optionally, the pressure balancing port is also connected to the evaporator 4 via a fourth branch, wherein the third branch and the fourth branch are arranged in parallel; a third switching valve 8 is also provided on the fourth branch to control the opening and closing of the fourth branch. When the fourth branch is connected, the pressure in the heat recovery unit 2 is regulated by the pressure of the evaporator 4.

[0032] In the above embodiment, the pressure balance port is connected to the evaporator 4 and the condenser 3 respectively, so as to adjust the inlet and outlet flow rate by using the pressure of the evaporator 4 or the condenser 3. The pressure in the evaporator 4 and the condenser 3 is different, so the connection can be determined as needed. Preferably, when it is necessary to increase the pressure in the heat recovery unit 2, it is connected to the condenser 3.

[0033] Figure 2 Another alternative structural schematic diagram of the heat recovery refrigeration unit is also shown, such as... Figure 2As shown, the unit has heat recovery water supply, heat recovery return water, cooling water inlet, cooling water outlet, chilled water inlet, and chilled water outlet. Each water circuit exchanges heat with the heat exchange tubes in the heat exchanger before flowing out. The mixture of oil and refrigerant discharged from the compressor enters the heat recovery unit for heat exchange, and then enters the condenser for heat exchange. After being throttled by the throttling device, it becomes a low-temperature, low-pressure liquid and returns to the evaporator. A switching valve and a pressure maintaining valve are installed between the heat recovery unit and the condenser. When heat recovery is not required, the first switching valve is open, and the heat recovery unit and the condenser become a single unit. When heat recovery is required, the first switching valve is closed, and the second and third switching valves are opened as needed.

[0034] Example 2 In a preferred embodiment 2 of the present invention, a control method for a heat recovery refrigeration unit is provided, which is applied to the heat recovery refrigeration unit in embodiment 1 above. Specifically, Figure 3 An optional flowchart of the method is shown, such as Figure 3 As shown, the method includes the following steps S302-S306: S302: Check whether the heat recovery refrigeration unit requires heat recovery; S304: When heat recovery is required, the pressure inside the heat recovery unit is regulated by the pressure maintaining valve to regulate the hot water supply temperature. S306: When heat recovery is not required, the heat recovery unit and condenser are integrated and used as a condenser.

[0035] The above embodiments provide a solution for intelligently controlling the hot water supply temperature. A heat recovery unit is installed on the heat recovery chiller, and a pressure maintaining valve is installed between the heat recovery unit and the condenser. This valve is used to adjust the heat recovery pressure of the heat recovery unit when heat recovery is needed, thereby regulating the hot water supply temperature. A first switching valve is also provided to disconnect when heat recovery is needed, allowing the pressure within the heat recovery unit to be adjusted via the pressure maintaining valve. By adding a pressure maintaining valve at the outlet of the heat recovery unit to control and regulate the condensing pressure, the problem of low hot water supply temperature in the heat recovery system is solved, the hot water supply temperature of the heat recovery system is increased, waste heat is effectively utilized, energy is saved and environmentally friendly, and user needs are met.

[0036] Regulating the pressure within the heat recovery unit via a pressure maintaining valve includes: controlling the first switching valve to open and controlling the pressure balance port of the heat recovery unit to open. Controlling the heat recovery unit and condenser to become one unit includes: controlling the first switching valve to close and controlling the pressure balance port of the heat recovery unit to close.

[0037] Specifically, controlling the opening of the pressure balance port of the heat recovery unit includes: acquiring the heat recovery return water temperature and the cooling water outlet temperature, calculating the temperature difference between the heat recovery return water temperature and the cooling water outlet temperature; and controlling the opening of the pressure balance port based on the temperature difference. When the temperature difference is greater than a preset threshold, the second switch valve 7 is closed and the third switch valve is opened; when the temperature difference is less than or equal to the preset threshold, the second switch valve 7 is opened and the third switch valve is closed.

[0038] In a preferred embodiment 2 of the present invention, another method for controlling a heat recovery refrigeration unit is also provided, specifically... Figure 4 An optional flowchart of the method is shown, such as Figure 4 As shown, the method includes the following steps S401-S411: S401: Start; S402: Is the heat recovery function enabled? If yes, proceed to step S403; otherwise, proceed to step S404. S403: The first switch valve is open, and the second switch valve 7 and the third switch valve are closed; First, determine whether the unit needs heat recovery function. If heat recovery function is not needed, the first switch valve is open, and the second switch valve 7 and the third switch valve are closed. S404: The first switch valve is closed; if heat recovery is required, the first switch valve is closed, and the temperature difference between the heat recovery return water and the cooling water outlet is detected. S405: Heat recovery return water - cooling water outlet > If T is true, proceed to step S406; otherwise, proceed to step S409. S406: Second switching valve 7 is open, third switching valve is closed; when temperature difference > set temperature At time T, the second switch valve 7 opens and the third switch valve closes. Next, the difference between the heat recovery unit pressure Pb and the condenser pressure Pa is determined. S407: Heat recovery unit pressure Pb - Condenser pressure Pa ≥ P, if yes, proceed to step S408; S408: Pressure maintaining valve is open; if the difference between Pb and Pa is ≤0, the spring force of the pressure maintaining valve is... As pressure P increases, the valve opening pressure increases, leading to a rise in pressure within the heat recovery unit. If the difference between Pb and Pa is greater than 0 and less than or equal to the set differential pressure value, the spring force of the pressure maintaining valve will increase. With P constant, the valve opening pressure remains constant, and the pressure inside the heat recovery unit increases. If the difference between Pb and Pa is greater than 0 and greater than the set differential pressure value, then the spring force of the pressure maintaining valve will increase. As P decreases, the valve opening pressure decreases, and the pressure inside the heat recovery unit decreases. S409: Second switch valve 7 is closed, third switch valve is open; S410: Heat recovery unit pressure Pb - Evaporator pressure Pc ≥ P, if yes, proceed to step S411; S411: Pressure maintaining valve is open. If the difference between Pb and Pa is ≤0, the spring force of the pressure maintaining valve is... As pressure P increases, the valve opening pressure increases, leading to a rise in pressure within the heat recovery unit. If the difference between Pb and Pa is greater than 0 and less than or equal to the set differential pressure value, the spring force of the pressure maintaining valve will increase. With P constant, the valve opening pressure remains constant, and the pressure inside the heat recovery unit increases. If the difference between Pb and Pa is greater than 0 and greater than the set differential pressure value, then the spring force of the pressure maintaining valve will increase. As P decreases, the valve opening pressure decreases, and the pressure inside the heat recovery unit decreases.

[0039] The aforementioned intelligent hot water temperature control solution addresses the issue that the water temperature in some heat recovery units is greatly affected by the condensing temperature. When the cooling water outlet temperature is low, the hot water supply temperature is also low, resulting in less recovered waste heat and an inability to meet the heat recovery temperature requirements. In this invention, when the cooling water outlet temperature is low, the pressure in the heat recovery unit and the condenser are monitored. If the pressure difference between the heat recovery unit and the condenser is less than the pressure setting value for the pressure maintaining valve, the pressure maintaining valve cannot be opened, and the pressure in the hot water recovery unit will continue to rise, meeting the requirement of a high temperature for the heat recovery return water.

[0040] Example 3 Based on the heat recovery refrigeration unit control method provided in Embodiment 2 above, in a preferred embodiment 3 of the present invention, a storage medium containing computer-executable instructions is also provided. When executed by a computer processor, the computer-executable instructions are used to execute the heat recovery refrigeration unit control method as described above.

[0041] The above embodiments provide a solution for intelligently controlling the hot water supply temperature. A heat recovery unit is installed on the heat recovery chiller, and a pressure maintaining valve is installed between the heat recovery unit and the condenser. This valve is used to adjust the heat recovery pressure of the heat recovery unit when heat recovery is needed, thereby regulating the hot water supply temperature. A first switching valve is also provided to disconnect when heat recovery is needed, allowing the pressure within the heat recovery unit to be adjusted via the pressure maintaining valve. By adding a pressure maintaining valve at the outlet of the heat recovery unit to control and regulate the condensing pressure, the problem of low hot water supply temperature in the heat recovery system is solved, the hot water supply temperature of the heat recovery system is increased, waste heat is effectively utilized, energy is saved and environmentally friendly, and user needs are met.

[0042] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not invented by the invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0043] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A heat recovery refrigeration unit, characterized in that, include: The compressor (1), heat recovery unit (2), condenser (3) and evaporator (4) are connected in sequence. A first branch and a second branch are provided in parallel between the heat recovery unit (2) and the condenser (3). A pressure maintaining valve (5) is provided on the first branch and a first switching valve (6) is provided on the second branch. When heat recovery is required, the first switching valve (6) is turned off and the pressure maintaining valve (5) is turned on. The pressure in the heat recovery unit (2) is adjusted by the pressure maintaining valve (5) to adjust the hot water supply temperature. The pressure maintaining valve (5) includes a pressure inlet, a pressure outlet and a pressure balance port. The pressure inlet and the pressure outlet are located on the first branch. The pressure balance port is used to control the opening pressure of the pressure maintaining valve (5) to regulate the pressure inside the heat recovery unit (2).

2. The heat recovery refrigeration unit according to claim 1, characterized in that, When heat recovery is not required, the pressure maintaining valve (5) is closed and the first switching valve (6) is closed, so that the heat recovery unit (2) and the condenser (3) become one unit and are used as a condenser.

3. The heat recovery refrigeration unit according to claim 1, characterized in that, The pressure balance port is connected to the condenser (3) through a third branch. A second switch valve (7) is also provided on the third branch to control the opening and closing of the third branch. When the third branch is connected, the pressure in the heat recovery unit (2) is adjusted by the pressure of the condenser (3).

4. The heat recovery refrigeration unit according to claim 3, characterized in that, The pressure balance port is also connected to the evaporator (4) through a fourth branch, wherein the third branch and the fourth branch are arranged in parallel; a third switch valve (8) is also provided on the fourth branch to control the opening and closing of the fourth branch. When the fourth branch is connected, the pressure in the heat recovery unit (2) is adjusted by the pressure of the evaporator (4).

5. A control method for a heat recovery refrigeration unit, applied to a heat recovery refrigeration unit as described in any one of claims 1 to 4, characterized in that, The method includes: Inspect whether the heat recovery refrigeration unit requires heat recovery; When heat recovery is required, the pressure inside the heat recovery unit is regulated by a pressure maintaining valve to regulate the hot water supply temperature. When heat recovery is not required, the heat recovery unit and the condenser are integrated and used as a single unit.

6. The method according to claim 5, characterized in that, The method of regulating the pressure inside the heat recovery unit through the pressure maintaining valve includes: controlling the first switching valve to open and controlling the pressure balance port of the heat recovery unit to open. Controlling the heat recovery unit and condenser to become one unit includes: controlling the first switching valve to close and controlling the pressure balance port of the heat recovery unit to close.

7. The method according to claim 6, characterized in that, Controlling the opening of the pressure balance port of the heat recovery unit includes: Obtain the heat recovery return water temperature and the cooling water outlet temperature of the condenser, and calculate the temperature difference between the heat recovery return water temperature and the cooling water outlet temperature; The pressure balance port is opened based on the temperature difference.

8. The method according to claim 7, characterized in that, The pressure balance port is connected to the condenser (3) via a third branch. A second switch valve (7) is also provided on the third branch to control the opening and closing of the third branch. When the third branch is connected, the pressure in the heat recovery unit (2) is adjusted by the pressure of the condenser (3). The pressure balance port is also connected to the evaporator (4) via a fourth branch. The third branch and the fourth branch are arranged in parallel. A third switch valve (8) is also provided on the fourth branch to control the opening and closing of the fourth branch. When the fourth branch is connected, the pressure in the heat recovery unit (2) is adjusted by the pressure of the evaporator (4). Controlling the opening of the pressure balance port based on the temperature difference includes: When the temperature difference exceeds a preset threshold, the second switching valve is closed and the third switching valve is opened. When the temperature difference is less than or equal to the preset threshold, the second switching valve is controlled to open and the third switching valve is controlled to close.

9. A storage medium containing computer-executable instructions, characterized in that, The computer-executable instructions, when executed by a computer processor, are used to perform the heat recovery refrigeration unit control method as described in any one of claims 5 to 8.

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