Parallel double-evaporator cold storage and supply system and control method

Abstract

The invention relates to a parallel double-evaporator cold storage and supply system and a control method. A medium-temperature evaporator and an ice storage device integrating evaporators are connected in parallel and share the same inverter compressor, a condenser and a matched condenser fan; four operation modes of independent cold storage, independent direct cold supply, simultaneous cold storage cold supply and ice melting cold supply are realized; the controller is connected with the medium-temperature evaporator and the ice storage device integrated with the evaporator and used for flexibly switching operation modes according to the actual cold storage and supply requirements and the peak-valley electricity price policy, and low-energy-consumption and low-cost operation of the system is achieved. The control method comprises an independent cold storage operation mode, an independent direct cold supply operation mode, a simultaneous cold storage and cold supply operation mode and an ice melting and cold supply operation mode. The system form that the two evaporators are connected in parallel can achieve dual purposes, the evaporators and the ice storage device are integrated so that direct heat exchange between refrigerants and water can be achieved, the evaporation temperature of the refrigerants is increased, and low-energy-consumption and low-cost operation of the system is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of refrigeration and cold storage, and in particular to a parallel dual-evaporator cold storage and supply system and a control method. Background Art

[0002] The rapid increase in buildings and people's demand for comfort have led to an increase in the proportion of cooling energy consumption in building operating energy consumption year by year, and the proportion of total energy consumption during the summer peak period has reached 60%. During peak electricity consumption periods, the load on the power grid increases sharply, and during low electricity consumption periods, the power system may be idle, resulting in an imbalance in power supply and demand and a greater peak-valley load difference. Ice storage technology combines the peak-valley electricity price policy to make ice during low electricity price periods and store the cold in the ice storage device. During peak electricity consumption periods, ice is melted to provide cooling, reducing the operating power of the refrigeration unit, thereby shifting the electricity demand during peak periods to low electricity periods, which can effectively achieve "peak shifting and valley filling" and reduce operating costs.

[0003] The existing ice storage system is usually equipped with an ice storage refrigeration unit on the basis of the conventional refrigeration system to meet the cold storage demand. This method has problems such as low system equipment utilization rate, high initial investment cost, complex structure and large floor space. In addition, the traditional ice storage system adopts the method of transferring the heat between the refrigerant and the coolant in the evaporator of the refrigeration unit and then inputting the produced low-temperature coolant into the heat exchange unit of the ice storage device through the coolant pump to exchange heat with water to achieve ice storage. The refrigerant and water need to be exchanged twice with the coolant as the heat transfer medium (i.e. indirect expansion), which will also lead to a low evaporation temperature of the refrigerant and poor system operation energy efficiency. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the above-mentioned prior art and provide a parallel dual-evaporator cold storage and cooling system and control method. The dual-evaporator parallel system can achieve dual-purpose of one machine. According to the actual cold storage and cooling demand and the peak-valley electricity price policy, the operation mode can be flexibly switched to improve the integration of the system, ensure a high utilization rate of the refrigeration system equipment, and save investment costs. The integration of the evaporator and the ice storage device can realize direct heat exchange between the refrigerant and water (i.e., direct expansion), increase the evaporation temperature of the refrigerant, and realize low energy consumption and low-cost operation of the system.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A parallel dual-evaporator cold storage and supply system comprises a variable frequency compressor, a condenser and a matching condenser fan, a drying filter, a liquid storage tank, a three-way valve, a low-temperature electronic expansion valve, a medium-temperature electronic expansion valve, an ice storage device integrating a low-temperature evaporator, a medium-temperature evaporator, a pressure balancing valve, a refrigerant pump, a plate heat exchanger and a controller. The medium-temperature evaporator is connected in parallel with the ice storage device integrating the evaporator, and share the same set of variable frequency compressors, condensers and matching condenser fans, so as to realize four operating modes of separate cold storage, separate direct cold supply, simultaneous cold storage and cold supply, and ice melting and cold supply; the controller is connected to the medium-temperature evaporator and the ice storage device integrating the evaporator, and is used to flexibly switch the operating mode according to the actual cold storage and cooling demand and the peak-valley electricity price policy, and cooperates with the temperature sensor and the frequency converter to couple and control and adjust the operating frequency of the variable frequency compressor and the condenser fan, so as to realize low-energy consumption and low-cost operation of the system.

[0007] Furthermore, the ice storage device integrating the low-temperature evaporator is used for making ice and storing cold during the cold storage process, in which the refrigerant directly enters the ice storage device to absorb the heat of water without the need for secondary heat exchange, thereby improving the refrigeration energy efficiency.

[0008] Furthermore, the variable frequency compressor, condenser and matching condenser fan, drying filter, liquid storage tank, three-way valve, low-temperature electronic expansion valve, ice storage device integrating low-temperature evaporator and pressure balancing valve are connected in sequence by refrigerant pipelines to form a cold storage cycle; the variable frequency compressor, condenser and matching condenser fan, drying filter, liquid storage tank, three-way valve, medium-temperature electronic expansion valve, one-way solenoid valve, medium-temperature evaporator and pressure balancing valve are connected in sequence by refrigerant pipelines to form a direct cooling cycle.

[0009] Furthermore, the cold storage cycle and the direct cooling cycle constitute a refrigerant loop; the coolant pump and the plate heat exchanger constitute a coolant loop, and the coolant pipeline is connected to users for cooling.

[0010] Furthermore, one-way solenoid valves are respectively provided at the outlets of the medium-temperature evaporator and the ice storage device integrating the low-temperature evaporator; the medium-temperature evaporator is a shell-and-tube heat exchanger, in which the refrigerant and the coolant are exchanged for heat; the low-temperature electronic expansion valve and the medium-temperature electronic expansion valve are arranged at the outlet of the condenser and are connected in parallel.

[0011] Furthermore, the ice storage device integrating a low-temperature evaporator includes one or more ice storage devices integrating an evaporator, and the internal heat exchange unit of the ice storage device integrating an evaporator includes one or more ice storage units composed of a microchannel parallel flow tube evaporator, closed rectangular fins and a microchannel parallel flow tube refrigerant flow channel.

[0012] Furthermore, the microchannel parallel flow tube evaporator and the microchannel parallel flow tube refrigerant flow channel are connected in parallel, with an internal pressure bearing capacity of not less than 3.0 MPa, and a collector and a splitter distributed in the same direction are respectively arranged at the inlet and outlet thereof.

[0013] Furthermore, the cavity of the microchannel parallel flow tube evaporator, the cavity of the closed rectangular fin and the cavity of the microchannel parallel flow tube refrigerant flow channel are arranged vertically and staggered.

[0014] Furthermore, the box body of the ice storage device integrating the low-temperature evaporator is made of two layers of metal plates and is filled with insulation material to prevent the loss of cold; a space is left between the top of the box body and the top of the internal heat exchange unit to accommodate the volume expansion generated by the freezing of water into ice.

[0015] A control method for a parallel dual-evaporator cold storage and cooling system includes: a single cold storage operation mode, a single direct cooling operation mode, a simultaneous cold storage and cooling operation mode, and an ice melting and cooling operation mode, wherein:

[0016] The separate cold storage operation mode includes: when there is a low electricity price period and no cooling demand, the one-way solenoid valve at the outlet of the ice cold storage device integrating the low-temperature evaporator is opened, the cold storage component works, and other system components are closed, and the whole process realizes ice making and cold storage during the low electricity price period;

[0017] The separate direct cooling operation mode includes: when the cooling capacity can meet the cooling demand during non-off-peak electricity price period or peak electricity price period, the one-way solenoid valve at the outlet of the medium-temperature evaporator, the gate valve between the medium-temperature evaporator and the plate heat exchanger, and the coolant pump are opened, the cooling components are operated, and other system components are closed, and the cooling demand is met by the system directly in the whole process;

[0018] The simultaneous cold storage and cooling operation mode includes: when there is a demand for cooling during off-peak electricity price period, the one-way solenoid valve at the outlet of the medium-temperature evaporator, the ice storage device integrating the low-temperature evaporator, and the gate valve between the medium-temperature evaporator and the plate heat exchanger are opened, the refrigerant pump is turned on, and all system components are working, and the whole process realizes simultaneous storage and cooling during off-peak electricity price period;

[0019] The ice melting cooling operation mode includes: when the ice storage device still has surplus cooling capacity during peak electricity price periods or non-peak electricity price periods, the gate valve and the refrigerant pump between the ice storage device and the plate heat exchanger are opened, and other system components are closed. The cooling demand in the entire process is met by the ice storage device.

[0020] The beneficial effects of the present invention are:

[0021] The present invention provides a parallel dual-evaporator cold storage and supply system and control method, which adopts a medium-temperature evaporator and an ice storage device integrating the evaporator in parallel, and shares the same set of variable frequency compressors, condensers and matching condenser fans and other system components, and can realize four operating modes: separate cold storage, separate direct cold supply, simultaneous cold storage and supply, and ice melting and supply. According to the actual cold storage and supply demand and the peak and valley electricity price policy, the operating mode can be flexibly switched, and the operating frequency of the compressor and the condenser fan can be adjusted in conjunction with the temperature sensor and the inverter coupling control method, so as to realize low energy consumption and low cost operation of the system.

[0022] The ice storage device, which integrates a low-temperature evaporator, uses refrigerant to directly exchange heat with water during the storage process. It has a simple structure, high integration, and does not require secondary heat exchange equipment, which improves the system energy efficiency. The refrigerant exchanges heat with ice through the internal heat exchange unit of the ice storage device, which belongs to the internal ice melting method. It solves the problems of low ice storage rate, water flow distribution blind spots, and "millennium ice" that exist in the existing direct expansion ice storage system that uses external ice melting. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural composition diagram of the parallel double evaporator cold storage and cooling system of the present invention;

[0024] Figure 2 This is a structural diagram of the ice storage device integrating an evaporator in one body of the present invention;

[0025] Description of the reference numerals: 11, variable frequency compressor; 12, condenser and matching condenser fan; 13, drying filter; 14, liquid storage tank; 15, three-way valve; 16, medium temperature electronic expansion valve; 17, medium temperature evaporator; 18, pressure balance valve; 19, low temperature electronic expansion valve; 120, ice storage device integrating evaporator; 121, refrigerant pump; 122, plate heat exchanger; 123, one-way solenoid valve; 124, one-way solenoid valve; 125, gate valve; 126, gate valve; 12 7. Temperature sensor; 128. Temperature sensor; 129. Temperature sensor; 130. Temperature sensor; 131. User; 132. Controller; 21. Microchannel parallel flow tube evaporator collector; 22. Microchannel parallel flow tube refrigerant flow channel splitter; 23. Microchannel parallel flow tube evaporator splitter; 24. Microchannel parallel flow tube refrigerant flow channel collector; 25. Microchannel parallel flow tube evaporator; 26. Microchannel microchannel parallel flow tube refrigerant flow channel; 27. Closed rectangular fin. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1 As shown, a parallel dual-evaporator cold storage and supply system in an embodiment of the present invention comprises a refrigerant loop and a secondary coolant loop. The refrigerant loop includes a cold storage cycle and a direct cold supply cycle. The cold storage cycle includes a variable frequency compressor 11, a condenser and a matching condenser fan 12, a drying filter 13, a liquid reservoir 14, a three-way valve 15, a low-temperature electronic expansion valve 19, a one-way solenoid valve 124, an ice storage device 120 integrating a low-temperature evaporator, and a pressure balancing valve 18. The above components are connected by refrigerant pipes to form a cold storage cycle; the direct cooling cycle includes a variable frequency compressor 11, a condenser and a matching condenser fan 12, a drying filter 13, a liquid reservoir 14, a three-way valve 15, a medium-temperature electronic expansion valve 16, a one-way solenoid valve 123, a medium-temperature evaporator 17 and a pressure balancing valve 18. The above components are connected by refrigerant pipes to form a direct cooling cycle; the refrigerant loop includes a refrigerant pump 121 and a plate heat exchanger 122, which are connected by refrigerant pipelines to provide cooling to users 131.

[0029] In the parallel dual-evaporator cold storage and cooling system, the three-way valve 15 has a liquid inlet and two liquid outlets, the liquid inlet is connected to the outlet of the liquid reservoir 14, and the two liquid outlets are respectively connected to the medium-temperature electronic expansion valve 16 and the low-temperature electronic expansion valve 19.

[0030] like Figure 2As shown, the ice storage device 120 with an integrated evaporator includes a microchannel parallel flow tube evaporator 25, a microchannel parallel flow tube refrigerant flow channel 26 and a closed rectangular fin 27. The two sides of the microchannel parallel flow tube evaporator 25 are respectively bonded with the closed rectangular fin 27 using thermal conductive silicone to reduce contact thermal resistance. The two sides of the microchannel parallel flow tube refrigerant flow channel 26 are respectively bonded with the closed rectangular fin 27 using thermal conductive silicone to reduce contact thermal resistance. The microchannel parallel flow tube evaporator 25 and the microchannel parallel flow tube refrigerant flow channel 26 are staggered, and the internal cavity is placed vertically. A microchannel parallel flow tube evaporator 25, a microchannel parallel flow tube refrigerant flow channel 26, and four closed rectangular fins 27 constitute an ice storage unit with an integrated evaporator. One or more ice storage units with integrated evaporators can be connected in series or in parallel to form an internal heat exchange unit of the ice storage device, and are placed in the ice storage box to form an ice storage device 120 with an evaporator. A gap is left between the internal heat exchange core of the ice storage device and the ice storage box to prevent the water from freezing into ice and expanding due to volume heat. The ice storage device 120 with an integrated evaporator can achieve efficient heat exchange between the three media of refrigerant, water / ice and refrigerant.

[0031] In the ice storage device 120 with an integrated evaporator, the microchannel parallel flow tube evaporator 25 and the microchannel parallel flow tube coolant flow channel 26 are connected in the following manner: Figure 2 As shown, when one or more microchannel parallel flow tube evaporators 25 are connected in parallel, the inlet and outlet are respectively provided with a collector 21 and a splitter 23 which are distributed in the same direction; when one or more microchannel parallel flow tube refrigerant flow channels 26 are connected in parallel, the inlet and outlet are respectively provided with a splitter 22 and a collector 24 which are distributed in the same direction.

[0032] Based on the above system, the present invention also proposes a control method for a parallel dual-evaporator cold storage and cooling system, which may include: a separate cold storage operation mode, a separate cooling operation mode, a simultaneous cold storage and cooling operation mode, and an ice melting and cooling operation mode. In this embodiment, the system operation mode is controlled by the controller 132 to open and close the one-way solenoid valve at the evaporator outlet and the plate heat exchanger inlet gate valve according to the peak and valley electricity price policy and the cooling demand.

[0033] Single cold storage operation mode: When it is the off-peak electricity price period and there is no cooling demand, the one-way solenoid valve 124 at the outlet of the ice storage device 120 integrated with the low-temperature evaporator is opened, and the refrigerant flows through the variable frequency compressor 11, the condenser and the matching condenser fan 12, the drying filter 13, the liquid storage tank 14, the three-way valve 15, the low-temperature electronic expansion valve 19, the one-way solenoid valve 124, the ice storage device 120 integrated with the low-temperature evaporator and the pressure balance valve 18 in sequence, and other system components are closed. At this time, the system provides cold capacity to the ice storage device to achieve ice making and cold storage.

[0034] Single cooling operation mode: When the cold storage capacity can meet the cooling demand during non-off-peak electricity price period or peak electricity price period, the one-way solenoid valve 123, gate valve 125 and coolant pump 121 at the outlet of the medium-temperature evaporator 17 are opened, and the refrigerant flows through the variable frequency compressor 11, condenser and matching condenser fan 12, dry filter 13, liquid storage tank 14, three-way valve 15, medium-temperature electronic expansion valve 16, one-way solenoid valve 123, medium-temperature evaporator 17 and pressure balance valve 18 in sequence, and other system components are closed. At this time, the system provides cold capacity to the coolant flowing through the plate heat exchanger 122, and realizes cooling to the user under the transportation of the coolant pump 121.

[0035] Simultaneous cold storage and cooling operation mode: When the electricity price is low and there is a demand for cooling, the one-way solenoid valve 124 at the outlet of the ice storage device 120 integrated with the low-temperature evaporator, the one-way solenoid valve 123 at the outlet of the medium-temperature evaporator 17, the gate valve 125, the gate valve 126 and the refrigerant pump 121 are opened, and the refrigerant flows in the following directions: the variable frequency compressor 11, the condenser and the matching condenser fan 12, the drying filter 13, the liquid storage tank 14, the three-way valve 15, the parallel-arranged medium-temperature electronic expansion valve 16 and the low-temperature electronic expansion valve 19, the parallel-arranged medium-temperature evaporator 17 and the ice storage device 120 integrated with the evaporator. At this time, the system simultaneously provides cold capacity to the ice storage device 120 integrated with the evaporator and the refrigerant flowing through the plate heat exchanger 122 to realize ice storage and cooling for users.

[0036] Ice melting and cooling operation mode: When there is still enough cold storage capacity in the ice storage device during the peak electricity price period or the non-peak electricity price period, the gate valve 126 and the coolant pump 121 are opened, and other system components are closed. At this time, the ice storage device 120 with an integrated evaporator melts ice and releases cold to provide cold capacity to the coolant flowing through the plate heat exchanger 122, and the coolant pump 121 delivers cold to the user.

[0037] The control method of the parallel dual-evaporator cold storage and cooling system also includes: the opening of the medium-temperature electronic expansion valve 16 and the low-temperature electronic expansion valve 19 is controlled by the controller 132 according to the superheat of the refrigerant at the outlet of the medium-temperature electronic expansion valve 16 and the low-temperature electronic expansion valve 19.

[0038] The control method of the parallel dual-evaporator cold storage and cooling system also includes: the speed of the variable frequency compressor 11 and the speed of the condenser fan 12 are controlled by the controller 132 according to the inlet and outlet temperature difference of the low-temperature evaporator 120 and the medium-temperature evaporator 17. The inlet and outlet temperature difference of the low-temperature evaporator 120 and the medium-temperature evaporator 17 is monitored and obtained by the temperature sensor 129, the temperature sensor 130, the temperature sensor 127, and the temperature sensor 128.

Claims

1. A parallel dual evaporator cold storage and cooling system, characterized in that: It includes a variable frequency compressor, a condenser and a matching condenser fan, a drying filter, a liquid storage tank, a three-way valve, a low-temperature electronic expansion valve, a medium-temperature electronic expansion valve, an ice storage device integrating a low-temperature evaporator, a medium-temperature evaporator, a pressure balancing valve, a refrigerant pump, a plate heat exchanger and a controller. The medium-temperature evaporator is connected in parallel with the ice storage device integrating the evaporator, and share the same set of variable frequency compressors, condensers and matching condenser fans to achieve four operating modes: separate cold storage, separate direct cold supply, simultaneous cold storage and cold supply, and ice melting and cold supply; the controller is connected to the medium-temperature evaporator and the ice storage device integrating the evaporator, and is used to flexibly switch the operating mode according to the actual cold storage and cooling demand and the peak-valley electricity price policy, and cooperates with the temperature sensor and the frequency converter coupling control to adjust the operating frequency of the variable frequency compressor and the condenser fan to achieve low energy consumption and low cost operation of the system.

2. The parallel dual-evaporator cold storage and cooling system according to claim 1 is characterized in that: The ice storage device integrating the low-temperature evaporator is used for making ice and storing cold during the cold storage process when the refrigerant directly enters the ice storage device to absorb the heat of water without the need for secondary heat exchange, thereby improving the refrigeration energy efficiency.

3. The parallel dual-evaporator cold storage and cooling system according to claim 1, characterized in that: The variable frequency compressor, condenser and matching condenser fan, drying filter, liquid storage tank, three-way valve, low-temperature electronic expansion valve, ice storage device integrating low-temperature evaporator and pressure balancing valve are connected in sequence by refrigerant pipelines to form a cold storage cycle; the variable frequency compressor, condenser and matching condenser fan, drying filter, liquid storage tank, three-way valve, medium-temperature electronic expansion valve, one-way solenoid valve, medium-temperature evaporator and pressure balancing valve are connected in sequence by refrigerant pipelines to form a direct cooling cycle.

4. The parallel dual-evaporator cold storage and cooling system according to claim 3 is characterized in that: The cold storage cycle and the direct cold supply cycle constitute a refrigerant loop; the coolant pump and the plate heat exchanger constitute a coolant loop, and the coolant pipeline is connected to users for cooling.

5. The parallel dual-evaporator cold storage and cooling system according to claim 1, characterized in that: The medium-temperature evaporator and the ice storage device integrating the low-temperature evaporator are respectively provided with a one-way solenoid valve at the outlet; the medium-temperature evaporator is a shell-and-tube heat exchanger, and the refrigerant and the coolant are exchanged for heat inside; the low-temperature electronic expansion valve and the medium-temperature electronic expansion valve are arranged at the condenser outlet and are connected in parallel.

6. The parallel dual-evaporator cold storage and cooling system according to claim 1, characterized in that: The ice storage device integrating a low-temperature evaporator includes one or more ice storage devices integrating an evaporator. The internal heat exchange unit of the ice storage device integrating an evaporator includes one or more ice storage units composed of a microchannel parallel flow tube evaporator, a closed rectangular fin and a microchannel parallel flow tube refrigerant flow channel.

7. The parallel dual-evaporator cold storage and cooling system according to claim 6, characterized in that: The microchannel parallel flow tube evaporator and the microchannel parallel flow tube refrigerant flow channel are connected in parallel, with an internal pressure bearing capacity of not less than 3.0 MPa, and a collector and a splitter distributed in the same direction are respectively arranged at the inlet and outlet thereof.

8. The parallel dual-evaporator cold storage and cooling system according to claim 6, characterized in that: The cavity of the microchannel parallel flow tube evaporator, the cavity of the closed rectangular fin and the cavity of the microchannel parallel flow tube refrigerant flow channel are arranged vertically and staggered.

9. The parallel dual-evaporator cold storage and supply system according to claim 6, characterized in that: The box body of the ice storage device integrating the low-temperature evaporator is made of two layers of metal plates and is filled with insulation material to prevent the loss of cold. A space is left between the top of the box body and the top of the internal heat exchange unit to accommodate the volume expansion generated by water freezing into ice.

10. A control method for a parallel dual-evaporator cold storage and cooling system according to any one of claims 1 to 9, characterized in that: include: Single cold storage operation mode, single direct cooling operation mode, simultaneous cold storage and cooling operation mode and ice melting and cooling operation mode, among which: The separate cold storage operation mode includes: when there is a low electricity price period and no cooling demand, the one-way solenoid valve at the outlet of the ice cold storage device integrating the low-temperature evaporator is opened, the cold storage component works, and other system components are closed, and the whole process realizes ice making and cold storage during the low electricity price period; The separate direct cooling operation mode includes: when the cooling capacity can meet the cooling demand during non-off-peak electricity price period or peak electricity price period, the one-way solenoid valve at the outlet of the medium-temperature evaporator, the gate valve between the medium-temperature evaporator and the plate heat exchanger, and the coolant pump are opened, the cooling components are operated, and other system components are closed, and the cooling demand is met by the system directly in the whole process; The simultaneous cold storage and cooling operation mode includes: when there is a demand for cooling during off-peak electricity price period, the one-way solenoid valve at the outlet of the medium-temperature evaporator, the ice storage device integrating the low-temperature evaporator, and the gate valve between the medium-temperature evaporator and the plate heat exchanger are opened, the refrigerant pump is turned on, and all system components are working, and the whole process realizes simultaneous storage and cooling during off-peak electricity price period; The ice melting cooling operation mode includes: when the ice storage device still has surplus cooling capacity during peak electricity price periods or non-peak electricity price periods, the gate valve and the refrigerant pump between the ice storage device and the plate heat exchanger are opened, and other system components are closed. The cooling demand in the entire process is met by the ice storage device.

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