Multi-connected dry capillary radiation heat pump system and its refrigerant flow control method

Abstract

The present invention provides a multi-connected dry capillary radiation heat pump system and a refrigerant flow control method therefor. The multi-connected dry capillary radiation heat pump system includes a heat pump unit and a plurality of capillary tube groups for heat exchange in a room. The capillary tube groups are used to be laid at indoor wall and / or ceiling and / or floor positions to directly radiate heat to the indoor air. The capillary tube groups are directly laid on the indoor wall to directly exchange heat with the indoor environment. Compared with a conventional heat pump using water as the heat exchange medium, one heat exchange link is omitted, which can reduce heat loss, improve energy efficiency, and at the same time omit the heat exchange equipment for heat exchange between water and refrigerant, reducing costs. The refrigerant flow control method of the multi-connected dry capillary radiation heat pump system can store the excess refrigerant amount in the system cycle in the standby capillary tube groups, or when the refrigerant circulation amount in the system is insufficient, discharge the refrigerant stored in the capillary tube groups into the system to achieve dynamic balance of the refrigerant circulation amount in the system.

Description

Technical Field

[0001] The present invention relates to the field of heat pump systems, and particularly to a multi-connected dry capillary radiation heat pump system and a refrigerant flow control method thereof. Background Art

[0002] A capillary radiation heat pump is a heating and cooling device that uses thermal radiation to transfer heat. Its principle is to use capillary radiation heat exchange to eliminate the sensible heat load in the room, and adopt a dehumidification method to eliminate the latent heat load in the room, so as to realize the independent control of the temperature and humidity in the indoor environment. Because of its high efficiency, energy saving, good comfort and no noise indoors, it has entered ordinary households.

[0003] However, at present, all heat pumps are water-based systems, and the existing defects are as follows: 1) It is necessary to design a heat exchanger for heat exchange between the refrigerant and water, such as a shell-and-tube heat exchanger or a plate heat exchanger, with high cost. 2) The hot water generated by the heat exchanger then enters the radiator or capillary tube to conduct radiation heat dissipation. Water is used as the secondary coolant at the end, and there is secondary heat exchange between water and air, increasing heat loss; 3) There are risks of freezing the pipeline and water leakage, and the safety and reliability are not high. When the machine stops in winter, since the water does not flow, when the outdoor ambient temperature is below zero degree, the water in the water pipe freezes and expands, bursting the pipeline; 4) When the installation is not good, it is easy to leak water, damaging the room and items. For floor heating, the maintenance is extremely inconvenient and it is necessary to disassemble the floor for inspection.

[0004] The above defects limit the use of heat pumps with water as the heat exchange medium. The multi-connected dry capillary radiation heat pump, that is, the multi-connected direct expansion capillary radiation heat pump, can avoid the above problems. However, this system is different from the traditional multi-connected unit system. The end of the multi-connected unit is matched with an air duct machine, an embedded ceiling machine, etc., and the length of the copper tube in the evaporator is short, and the amount of refrigerant stored is small. For the multi-connected capillary radiation heat pump, the unit is matched with multiple sets of air duct machines and capillary tube groups, where the air duct machine is for refrigeration and the capillary tube is for radiation heating. Each set of capillary bundles is composed of multiple, even more than 10 capillary tubes with a length of 12-18m. The refrigerant fills all the capillary tubes and air duct machines, and the amount of refrigerant filled in the unit is large. On the other hand, when heating, some of the matching end capillary bundles may be in a standby state. If the existing refrigerant flow control method for heating in a multi-connected unit is adopted, that is, the standby end electronic expansion valve maintains a certain standby opening degree, it will cause energy waste and reduce the energy efficiency of the unit. If the standby end electronic expansion valve is closed, the refrigerant will accumulate in the standby capillary bundle and air duct machine. The amount of accumulated refrigerant is large, resulting in a small amount of refrigerant circulating in the system, making the unit lack refrigerant during operation and seriously affecting the heating effect. Furthermore, during the season conversion, such as using capillary radiation heating in winter and refrigerating in summer, a large amount of refrigerant accumulates in the capillary tube, resulting in insufficient refrigerant circulation in the system when the air duct machine refrigerates and no refrigeration effect. Summary of the Invention

[0005] The object of the present invention is to provide a multi-connected dry capillary radiation heat pump system to reduce the energy consumption caused by excessive heat exchange times. Another object of the present invention is to provide a refrigerant flow control method for a multi-connected dry capillary radiation heat pump system to prevent excessive accumulation of refrigerant in the capillary tubes, resulting in a shortage of refrigerant in the system.

[0006] A multi-connected dry capillary radiation heat pump system includes a heat pump unit and a plurality of capillary tube groups for heat exchange in a room. The capillary tube groups are used to be laid on the indoor walls and / or ceilings and / or floors to achieve direct radiation heat exchange with air, and the capillary tube groups are controlled for heat exchange by the heat pump unit.

[0007] In the above solution, the capillary tube groups are directly laid indoors for direct heat exchange with the indoor environment, without using water as an intermediate medium. This reduces the number of heat exchange times, improves energy efficiency, and at the same time reduces the heat exchange equipment for heat exchange between water and air, thus reducing costs.

[0008] Preferably, the heat pump unit includes a compressor. The liquid outlet of the compressor is sequentially connected with an oil separator and a four-way reversing valve through pipelines. The four-way reversing valve includes a C port, an E port, an S port, and a D port communicated with the oil separator.

[0009] The C port is sequentially connected with an outdoor fin heat exchanger, a main circuit electronic expansion valve, a high-pressure liquid receiver, and a liquid pipe stop valve through pipelines. The capillary tube group includes an end liquid pipe and an end gas pipe. The liquid pipe stop valve is connected to the end liquid pipes of a plurality of capillary tube groups through a manifold. A capillary tube electronic expansion valve is arranged on the pipeline between the capillary tube group and the manifold.

[0010] The E port is connected with a gas pipe stop valve through a pipeline. The gas pipe stop valve is connected to the end gas pipes of a plurality of capillary tube groups through a shunt pipe.

[0011] The S port is connected with a gas-liquid separator through a pipeline. The outlet of the gas-liquid separator is provided with a suction pipe communicated with the compressor.

[0012] Preferably, an exhaust temperature sensor is arranged on the pipeline between the compressor and the oil separator. A high-pressure pressure switch and a high-pressure pressure sensor are arranged on the pipeline between the oil separator and the four-way reversing valve. An end liquid pipe temperature sensor is arranged at the end liquid pipe. An end gas pipe temperature sensor and a solenoid valve are arranged at the end gas pipe. An indoor temperature sensor for detecting the indoor temperature is also included. An outdoor temperature sensor for detecting the outdoor unit ambient temperature and a coil temperature sensor for detecting the heat exchange coil temperature on the outdoor fin heat exchanger are arranged at the outdoor fin heat exchanger.

[0013] Preferably, an intake air temperature sensor, a low-pressure pressure sensor, and a low-pressure pressure switch are provided on the intake pipe. An oil return capillary is connected between the oil separator and the intake pipe, and the connection end of the oil return capillary is located between the intake air temperature sensor and the low-pressure pressure sensor.

[0014] A refrigerant flow control method for a multi-connected dry capillary radiation heat pump system includes the following steps:

[0015] S1. Start the compressor and enter the soft start state. The main electronic expansion valve is opened to 100 - 150 steps, and each capillary group enters the standby or startup state. The startup capillary groups enter the running state.

[0016] S2. Open the capillary electronic expansion valve corresponding to the standby capillary group to 100 - 120 steps, open the solenoid valve, and initially run for t time.

[0017] S3. Close the solenoid valve corresponding to the standby capillary group, and close the capillary electronic expansion valve corresponding to the standby capillary group after 15 - 20 s.

[0018] S4. The high-pressure pressure sensor collects the high-pressure pressure in real time.

[0019] Query the pressure-saturation temperature conversion table to obtain the saturation temperature corresponding to the high-pressure pressure, that is, the condensation temperature Pd_t. The exhaust temperature sensor collects the exhaust temperature Td in real time. Preset the upper limit value of the exhaust temperature Tdmax = 90 - 98 °C and the target condensation temperature Pd_t.tar = 38 - 42 °C. Define the exhaust superheat ΔTd = Td - Pd_t, and determine the refrigerant shortage and excess:

[0020] When the following conditions are simultaneously met, it is determined that the system has a refrigerant shortage:

[0021] The unit is running, and there is one or more standby capillary groups; Pd_t ≤ the saturation temperature corresponding to [Pd_t.tar corresponding pressure - 3 bar]; the exhaust temperature Td ≥ Tdmax.

[0022] When the following conditions are simultaneously met, it is determined that the system has an excess refrigerant:

[0023] The unit is running, and there is one or more standby capillary groups; P d_t ≥ Pd_t.tar; ΔTd ≤ 15 °C.

[0024] S5. When the system has a refrigerant shortage, perform shortage control:

[0025] Open the solenoid valve corresponding to the standby capillary group, and open the corresponding capillary electronic expansion valve to 100 - 120 steps.

[0026] When there is excess refrigerant in the system, excess control is carried out:

[0027] The solenoid valve corresponding to the standby capillary group remains closed, and the corresponding capillary electronic expansion valve is opened to 100 - 120 steps.

[0028] S6. During the lack-of-fluorine control process, when one of the following conditions is met, it is determined that the lack-of-fluorine control ends:

[0029] Pd_t ≥ the saturation temperature corresponding to [Pd_t.tar corresponding pressure - 0.5 bar]; Td < Tdmax - (15 - 18 °C); the unit performs defrosting operation or the whole machine shuts down;

[0030] During the excess control process, when one of the following conditions is met, it is determined that the excess control ends:

[0031] Pd_t ≤ the saturation temperature corresponding to [Pd_t.tar corresponding pressure - 0.5 bar]; ΔTd > 20 - 25 °C; the unit performs defrosting operation or the whole machine shuts down;

[0032] S7. After the lack-of-fluorine control ends, or after the excess control ends, or when there is no lack of fluorine and excess in the system, the capillary electronic expansion valve and solenoid valve corresponding to the standby capillary group remain closed.

[0033] In the above solution, the control of the standby capillary group is added, which can store the excess refrigerant amount in the system cycle into the standby capillary group, or when the refrigerant circulation amount in the system is insufficient, discharge the refrigerant stored in the capillary group into the system to achieve the dynamic balance of the refrigerant circulation amount in the system.

[0034] Preferably, the control method of the main circuit electronic expansion valve in the system includes the following steps:

[0035] A1. Start the compressor and enter the soft start stage. The main circuit electronic expansion valve is opened to the initial opening degree = 100 - 150 steps. The low-pressure pressure sensor collects the low-pressure pressure in real time, queries the pressure-saturation temperature comparison table to obtain the saturation temperature corresponding to the high-pressure pressure, that is, the evaporation temperature Ps_t. The suction temperature sensor collects the compressor suction temperature Ts in real time, and the coil temperature sensor collects the coil temperature Tdef in real time. Preset the minimum exhaust superheat ΔTdset.min = 15 - 18 °C and the maximum exhaust superheat ΔTdset.max = 45 - 48 °C, and define the suction superheat ΔTs = Ts - Tdef;

[0036] A2. When one of the following conditions is met, the soft start stage ends, and the main circuit electronic expansion valve adjusts the opening degree to keep ΔTs = 1 - 3 °C:

[0037] Td ≥ 90°C; Pd_t ≥ Pd_t.tar; Ps_t < 3 - 4°C; The soft start stage lasts for 8 minutes;

[0038] A3. When ΔTd < ΔTdset.min, the main electronic expansion valve makes a closing movement to make ΔTs n = ΔTs n-1 +1°C until one of the following conditions is met:

[0039] ΔTdset.min ≤ ΔTd ≤ ΔTdset.max; The main electronic expansion valve reaches the minimum opening = 80 - 100 steps;

[0040] When ΔTd > ΔTdset.max or Td > 100°C, the main electronic expansion valve makes an opening movement to make ΔTs n = ΔTs n-1 -1°C until one of the following conditions is met:

[0041] ΔTdset.min ≤ ΔTd ≤ ΔTdset.max and Td ≤ 100°C; The main electronic expansion valve reaches the maximum opening = 300 - 400 steps;

[0042] Where ΔTs n is the target suction superheat to be adjusted to in this cycle, and ΔTs n-1 is the suction superheat of the previous cycle, and the adjustment cycle is 3 minutes.

[0043] Preferably, the operating state of the starting capillary group during heating operation includes the following steps:

[0044] B1. The solenoid valve is opened, and the capillary electronic expansion valve is opened to the initial opening = 350 - 450 steps. The end liquid pipe temperature sensors corresponding to the starting capillary group detect the liquid pipe temperatures TeL.i in real time, and the average value of the liquid pipe temperatures corresponding to the starting capillary group is calculated

[0045] B2. When the temperature of a liquid pipe is reached, the capillary electronic expansion valve corresponding to this liquid pipe is closed by 15 steps every 3 minutes until the capillary electronic expansion valve reaches the minimum opening = 200 - 250 steps or

[0046] When the temperature of a liquid pipe is reached, the capillary electronic expansion valve corresponding to this liquid pipe is closed by 15 steps every 3 minutes until the capillary electronic expansion valve reaches the maximum opening = 450 - 480 steps or

[0047] Preferably, during the refrigeration operation, the main electronic expansion valve of the outdoor host is fully opened to 480 steps, the capillary electronic expansion valve corresponding to the standby capillary group is closed, and the corresponding solenoid valve is opened.

[0048] Preferably, when the defrost signal is sent during the refrigeration operation, the defrosting process includes the following steps:

[0049] C1. The four-way reversing valve is powered off and reversed, and the capillary electronic expansion valve corresponding to the standby capillary group is opened to the defrosting opening degree = 250 - 300 steps;

[0050] C2. After the system receives the defrosting completion command, the capillary electronic expansion valve corresponding to the standby capillary group is adjusted to the standby opening degree = 100 - 120 steps;

[0051] C3. Residual operation after defrosting is performed, and the solenoid valve remains open for 2 - 3 minutes;

[0052] C4. After the residual operation ends, the solenoid valve is closed, and the capillary electronic expansion valve is closed after 15 seconds. Description of the Drawings

[0053] Figure 1 It is a schematic diagram of the heat pump system of the present invention;

[0054] Figure 2 It is a schematic diagram of the refrigeration state of the heat pump system of the present invention;

[0055] Figure 3 It is a schematic diagram of the heating state of the heat pump system of the present invention;

[0056] Figure 4 It is a timing diagram of the heating process control;

[0057] Figure 5 It is a timing diagram of the defrosting process control;

[0058] Figure 6 It is a timing diagram of the refrigeration process control;

[0059] Description of the reference numerals: 11, indoor temperature sensor; 20, capillary tube group; 21, end liquid pipe; 22, end gas pipe; 23, capillary electronic expansion valve; 24, end liquid pipe temperature sensor; 25, end gas pipe temperature sensor; 26, solenoid valve; 30, compressor; 31, exhaust temperature sensor; 40, oil separator; 41, high-pressure pressure switch; 42, high-pressure pressure sensor; 50, four-way reversing valve; 51, port C; 52, port E; 53, port S; 54, port D; 60, outdoor finned heat exchanger; 61, outdoor temperature sensor; 62, coil temperature sensor; 71, main circuit electronic expansion valve; 72, high-pressure liquid receiver; 73, liquid pipe stop valve; 74, manifold; 75, gas pipe stop valve; 76, shunt pipe; 80, gas-liquid separator; 90, suction pipe; 91, suction temperature sensor; 92, low-pressure pressure sensor; 93, low-pressure pressure switch; 94, oil return capillary tube. Detailed implementation manners

[0060] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings.

[0061] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "bottom", "outer side", "front and back", etc. is the orientation or positional relationship shown in the state of the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0062] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the term "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0063] A multi-connected dry capillary radiation heat pump system includes a heat pump unit and a plurality of capillary tube groups 20 for heat exchange in a room. The capillary tube groups 20 are used to be laid on indoor walls and / or ceilings and / or floors to achieve direct radiation heat exchange with air, and the capillary tube groups 20 are controlled for heat exchange by the heat pump unit.

[0064] In the above solution, the capillary tube group 20 is directly laid indoors for direct heat exchange with the indoor environment without using water as an intermediate medium. This reduces the number of heat exchange processes, improves energy efficiency, and simultaneously reduces the heat exchange equipment for heat exchange between water and air, thereby reducing costs. The capillary tube group 20 is preferably laid at the floor and ceiling. Since cold air sinks and hot air rises, the capillary tube group 20 installed on the floor can be used for heating, and the capillary tube group 20 installed on the ceiling can be used for cooling. At the same time, the solution in this application is a heat pump system that does not generate wind. Using refrigerant as the heat exchange medium, there is only one heat exchange process, reducing heat loss, and there is no risk of water leakage or freezing of pipelines; adopting a multi-connected method, each capillary tube group 20 is independently controlled, and the capillary tube groups 20 that do not require temperature control consume zero energy; and only a local temperature control method is adopted for the indoor environment, which can significantly reduce energy consumption and achieve intelligent and precise temperature control indoors.

[0065] Preferably, the heat pump unit includes a compressor 30. The liquid outlet of the compressor 30 is sequentially connected with an oil separator 40 and a four-way reversing valve 50 through pipelines. The four-way reversing valve 50 includes a C port 51, an E port 52, an S port 53, and a D port 54 communicated with the oil separator 40.

[0066] The C port 51 is sequentially connected with an outdoor finned heat exchanger 60, a main circuit electronic expansion valve 71, a high-pressure liquid storage tank 72, and a liquid pipe stop valve 73 through pipelines. The capillary tube group 20 includes a terminal liquid pipe 21 and a terminal gas pipe 22. The liquid pipe stop valve 73 is connected to the terminal liquid pipes 21 of multiple capillary tube groups 20 through a manifold 74. A capillary tube electronic expansion valve 23 is arranged on the pipeline between the capillary tube group 20 and the manifold 74.

[0067] The E port 52 is connected with a gas pipe stop valve 75 through a pipeline. The gas pipe stop valve 75 is connected to the terminal gas pipes 22 of multiple capillary tube groups 20 through a shunt pipe 76.

[0068] The S port 53 is connected with a gas-liquid separator 80 through a pipeline. The outlet of the gas-liquid separator 80 is provided with a suction pipe 90 communicated with the compressor 30.

[0069] When the system is turned on to the heating mode, the compressor 30 is started, and the four-way reversing valve 50 is controlled to act so that the D port 54 and the E port 52 are communicated, and the C port 51 and the S port 53 are communicated. The medium in the compressor 30 flows along the following route:

[0070] Compressor 30 - Oil separator 40 - D port 54 - E port 52 - Gas pipe stop valve 75 - Shunt pipe 76 - Solenoid valve 26 - Terminal gas pipe 22 - Capillary tube group 20 - Terminal liquid pipe 21 - Capillary tube electronic expansion valve 23 - Manifold 74 - Liquid pipe stop valve 73 - High-pressure liquid storage tank 72 - Main circuit electronic expansion valve 71 - Outdoor finned heat exchanger 60 - C port 51 - S port 53 - Gas-liquid separator 80 - Suction pipe 90 - Compressor 30;

[0071] When the system turns on the refrigeration mode, the compressor 30 is started, and the four-way reversing valve 50 is controlled to act, so that the port D 54 is communicated with the port C 51, and the port E 52 is communicated with the port S 53. The medium in the compressor 30 flows along the following route:

[0072] Compressor 30 - Oil separator 40 - Port D 54 - Port C 51 - Outdoor fin heat exchanger 60 - Main circuit electronic expansion valve 71 - High-pressure liquid receiver 72 - Liquid pipe stop valve 73 - Manifold 74 - Capillary electronic expansion valve 23 - End liquid pipe 21 - Capillary tube group 20 - End gas pipe 22 - Solenoid valve 26 - Shunt pipe 76 - Gas pipe stop valve 75 - Port E 52 - Port S 53 - Gas-liquid separator 80 - Suction pipe 90 - Compressor 30;

[0073] As Figure 3 shown, the high-temperature and high-pressure gaseous refrigerant compressed by the DC compressor 30 passes through the oil separator 40, the four-way reversing valve 50, and the gas pipe stop valve 75, and then is branched through the shunt pipe 76. After each path of refrigerant passes through the solenoid valve 26, it enters each layer of capillary tube group 20, and exchanges radiant heat with the indoor ambient air of each layer to raise the temperature of each indoor environment. After the radiant heat exchange, the refrigerant in each layer of capillary tube group 20 passes through the capillary electronic expansion valve 23, and one path of refrigerant of the capillary tube at the bottom of the second layer passes through the capillary electronic expansion valve 23 and converges at the manifold 74. The converged refrigerant passes through the liquid pipe stop valve 73, the high-pressure liquid receiver 72, and the main circuit electronic expansion valve 71 and is throttled and then enters the outdoor fin heat exchanger 60 to exchange convective heat with the air. After the refrigerant absorbs heat and evaporates, it passes through the four-way reversing valve 50 and enters the gas-liquid separator 80. The liquid refrigerant deposits at the bottom of the gas-liquid separator 80, and the gaseous refrigerant returns to the compressor 30 for compression, completing the heating mode.

[0074] As Figure 2As shown in the figure, the high-temperature and high-pressure gaseous refrigerant compressed by the compressor 30 passes through the oil separator 40 and the four-way reversing valve 50, and enters the outdoor fin heat exchanger 60 to conduct convective heat exchange with the outdoor air. After condensing and releasing heat, it becomes a medium-temperature and medium-pressure liquid refrigerant, and then passes through the main electronic expansion valve 71, the high-pressure liquid receiver 72, the liquid pipe stop valve 73, and the manifold 74. Then, one path of the refrigerant is branched after passing through the manifold 74. Each path of the refrigerant passes through the capillary electronic expansion valve 23 for throttling and then enters each layer of capillaries to conduct radiative heat exchange with the indoor ambient air to cool each indoor environment. After the radiative heat exchange, one path of the refrigerant in the capillary tube group 20 passes through the solenoid valve 26 and converges with other paths of the refrigerant in the shunt pipe 76. The converged refrigerant then passes through the gas pipe stop valve 75 and the four-way reversing valve 50 and enters the gas-liquid separator 80. The liquid refrigerant deposits at the bottom of the gas-liquid separator, and the gaseous refrigerant returns to the compressor 30 for compression, completing the refrigeration mode and controlling the temperature of the indoor environment. In the above solution, the switching between refrigeration and heating is directly achieved through the switching of the four-way reversing valve 50, so that refrigeration and heating can be achieved without two sets of systems, reducing the system equipment.

[0075] Preferably, an exhaust temperature sensor 31 is provided on the pipeline between the compressor 30 and the oil separator 40, a high-pressure pressure switch 41 and a high-pressure pressure sensor 42 are provided on the pipeline between the oil separator 40 and the four-way reversing valve 50, a terminal liquid pipe temperature sensor 24 is provided at the terminal liquid pipe 21, a terminal gas pipe temperature sensor 25 and a solenoid valve 26 are provided at the terminal gas pipe 22, and an indoor temperature sensor 11 for detecting the temperature in the room is further included. An outdoor temperature sensor 61 for detecting the outdoor unit ambient temperature and a coil temperature sensor 62 for detecting the heat exchange coil temperature on the outdoor fin heat exchanger 60 are provided at the outdoor fin heat exchanger 60. Each sensor is used to detect the system and provide parameters, and the system controls according to the parameters. The coil temperature sensor 62 is used to collect the coil temperature Tdef in real time. The preset minimum exhaust superheat ΔTdset.min = 15 - 18 °C and the maximum exhaust superheat ΔTdset.max = 45 - 48 °C are defined, and the suction superheat ΔTs = Ts - Tdef; the system is controlled according to the suction superheat ΔTs.

[0076] Preferably, a suction temperature sensor 91, a low-pressure pressure sensor 92, and a low-pressure pressure switch 93 are provided on the suction pipe 90. A return oil capillary 94 is connected between the oil separator 40 and the suction pipe 90, and the connection end of the return oil capillary 94 is located between the suction temperature sensor 91 and the low-pressure pressure sensor 92. The return oil capillary 94 is used to return the excessive medium in the oil separator 40 to the system. The high-pressure pressure switch 41 and the high-pressure pressure sensor 42 are arranged in sequence along the flow direction, and the suction temperature sensor 91, the low-pressure pressure sensor 92, and the low-pressure pressure switch 93 are arranged in sequence along the flow direction.

[0077] A refrigerant flow control method for a multi - connected dry capillary radiation heat pump system, as Figure 4 shown, includes the following steps:

[0078] S1. Start the compressor and enter the soft - start state. The main electronic expansion valve 71 is opened to 100 - 150 steps. Each capillary group 20 enters the standby or startup state, and the startup capillary groups 20 enter the running state;

[0079] S2. The capillary electronic expansion valve 23 corresponding to the standby capillary group 20 is opened to 100 - 120 steps, the solenoid valve 26 is opened, and the initial operation is for t time;

[0080] S3. The solenoid valve 26 corresponding to the standby capillary group 20 is closed. After 15 - 20 s, the capillary electronic expansion valve 23 corresponding to the standby capillary group 20 is closed;

[0081] S4. The high - pressure pressure sensor 42 collects the high - pressure pressure in real - time, queries the pressure - saturation temperature comparison table to obtain the saturation temperature corresponding to the high - pressure pressure, that is, the condensation temperature Pd_t. The exhaust temperature sensor 31 collects the exhaust temperature Td in real - time. The preset upper limit value of the exhaust temperature Tdmax = 90 - 98 °C and the target condensation temperature Pd_t.tar = 38 - 42 °C are set. Define the exhaust superheat ΔTd = Td - Pd_t, and determine the lack of refrigerant and excess refrigerant:

[0082] When the following conditions are met simultaneously, it is determined that the system lacks refrigerant:

[0083] The unit is running, and there is one or more standby capillary groups 20; Pd_t ≤ the saturation temperature corresponding to [Pd_t.tar corresponding pressure - 3 bar]; the exhaust temperature Td ≥ Tdmax;

[0084] When the following conditions are met simultaneously, it is determined that the system has excess refrigerant:

[0085] The unit is running, and there is one or more standby capillary groups 20; P d_t ≥ Pd_t.tar; ΔTd ≤ 15 °C.

[0086] S5. When the system lacks refrigerant, perform lack - of - refrigerant control:

[0087] The solenoid valve 26 corresponding to the standby capillary group 20 is opened, and the corresponding capillary electronic expansion valve 23 is opened to 100 - 120 steps; at this time, the refrigerant in the standby capillary group 20 is discharged into the system.

[0088] When the system has excess refrigerant, perform excess - refrigerant control:

[0089] The solenoid valve 26 corresponding to the standby capillary group 20 remains closed, and the corresponding capillary electronic expansion valve 23 is opened to 100 - 120 steps; at this time, the refrigerant in the system enters the standby capillary group 20.

[0090] S6. During the lack-of-refrigerant control process, when one of the following conditions is met, it is determined that the lack-of-refrigerant control ends:

[0091] Pd_t ≥ the saturation temperature corresponding to [Pd_t.tar corresponding pressure - 0.5 bar]; Td < Tdmax - (15 - 18 °C); the unit performs defrosting operation or the whole machine shuts down;

[0092] During the over-surplus control process, when one of the following conditions is met, it is determined that the over-surplus control ends:

[0093] Pd_t ≤ the saturation temperature corresponding to [Pd_t.tar corresponding pressure - 0.5 bar]; ΔTd > 20 - 25 °C; the unit performs defrosting operation or the whole machine shuts down;

[0094] S7. After the lack-of-refrigerant control ends or the over-surplus control ends or when there is no lack of refrigerant and over-surplus in the system, the capillary electronic expansion valve 23 and the solenoid valve 26 corresponding to the standby capillary group 20 remain closed.

[0095] In the above solution, the startup and standby of the capillary group 20 are determined by the remote control or according to the ambient temperature. There is a lot of prior art in this regard, so it will not be elaborated here. The control of the standby capillary group 20 is added. By storing the over-surplus medium in the standby capillary group 20 or supplementing the medium in the standby capillary group 20 to the system, it is prevented that too much refrigerant accumulates in the capillary, resulting in a shortage of refrigerant in the system.

[0096] As Figure 5 shown, the control method of the main circuit electronic expansion valve 71 in the system includes the following steps:

[0097] A1. Start the compressor and enter the soft start stage. The main circuit electronic expansion valve 71 is opened to the initial opening = 100 - 150 steps. The low-pressure pressure sensor 92 collects the low-pressure pressure in real time, queries the pressure-saturation temperature conversion table to obtain the saturation temperature corresponding to the high-pressure pressure, that is, the evaporation temperature Ps_t. The suction temperature sensor collects the compressor suction temperature Ts in real time, and the coil temperature sensor 62 collects the coil temperature Tdef in real time. Preset the minimum exhaust superheat ΔTdset.min = 15 - 18 °C and the maximum exhaust superheat ΔTdset.max = 45 - 48 °C, and define the suction superheat ΔTs = Ts - Tdef;

[0098] A2. When one of the following conditions is met, the soft start stage ends, and the main circuit electronic expansion valve 71 adjusts the opening to maintain ΔTs = 1 - 3 °C:

[0099] Td ≥ 90 °C; Pd_t ≥ Pd_t.tar; Ps_t < 3 - 4 °C; The soft start phase lasts for 8 min;

[0100] A3. When ΔTd < ΔTdset.min, the main electronic expansion valve 71 makes a small closing movement to make ΔTs n = ΔTs n-1 + 1 °C until one of the following conditions is met:

[0101] ΔTdset.min ≤ ΔTd ≤ ΔTdset.max; The main electronic expansion valve 71 reaches the minimum opening = 80 - 100 steps;

[0102] When ΔTd > ΔTdset.max or Td > 100 °C, the main electronic expansion valve 71 makes a large opening movement to make ΔTs n = ΔTs n-1 - 1 °C until one of the following conditions is met:

[0103] ΔTdset.min ≤ ΔTd ≤ ΔTdset.max and Td ≤ 100 °C; The main electronic expansion valve 71 reaches the maximum opening = 300 - 400 steps;

[0104] Where ΔTs n is the target suction superheat to be adjusted to within this cycle, and ΔTs n-1 is the suction superheat of the previous cycle. The adjustment cycle is 3 min. A pre - start phase is added to prevent the system from starting directly, which may cause damage to the system due to too much or too little refrigerant in the system. At the same time, through the correction control adjustment of the main electronic expansion valve 71, the exhaust superheat of the temperature control system is controlled within a certain range to ensure the stable and reliable operation of the compressor.

[0105] As Figure 6 shown, the operating state of the starting capillary tube group 20 during the heating operation includes the following steps:

[0106] B1. The solenoid valve 26 is opened, the capillary electronic expansion valve 23 is opened to the initial opening = 350 - 450 steps, and the end liquid pipe temperature sensors 24 corresponding to the starting capillary tube group 20 detect the liquid pipe temperatures TeL.i in real - time, and the average value of the liquid pipe temperatures corresponding to the starting capillary tube group 20 is calculated

[0107] B2. When the temperature of a liquid pipe is such that, the corresponding capillary electronic expansion valve 23 of this liquid pipe is closed by 15 steps every 3 minutes until the capillary electronic expansion valve 23 reaches the minimum opening = 200 - 250 steps or

[0108] When the temperature of the liquid pipe is such and such, the capillary electronic expansion valve 23 corresponding to the liquid pipe closes 15 steps every 3 minutes until the capillary electronic expansion valve 23 reaches the maximum opening degree = 450 - 480 steps or

[0109] Preferably, during refrigeration operation, the main electronic expansion valve is fully opened to 480 steps, the capillary electronic expansion valve 23 corresponding to the standby capillary group 20 is closed, and the corresponding solenoid valve 26 is opened. In this way, the system can achieve independent temperature control for each room, locally control the temperature of the rooms with heat exchange requirements, and have zero energy consumption for the rooms without heat exchange requirements. The system can provide a uniform temperature field without blowing during the heat exchange process, achieve intelligent and precise temperature control, greatly reduce the energy consumption during the heat exchange process, improve the temperature control effect, and reduce the initial investment of the equipment. During refrigeration operation, the control methods of the capillary electronic expansion valve 23 and the solenoid valve 26 on the capillary group 20 in operation are prior arts, and the specific control methods are the same as the solutions in the Chinese patent CN110822635A of the applicant's prior application.

[0110] Preferably, when the defrosting signal is sent during the refrigeration operation process, the defrosting process includes the following steps:

[0111] C1. The four-way reversing valve 50 is powered off and reversed, and the capillary electronic expansion valve 23 corresponding to the standby capillary group 20 is opened to the defrosting opening degree = 250 - 300 steps;

[0112] C2. After the system receives the defrosting completion command, the capillary electronic expansion valve 23 corresponding to the standby capillary group 20 is adjusted to the standby opening degree = 100 - 120 steps;

[0113] C3. Perform the residual operation after defrosting, and the solenoid valve 26 remains open for 2 - 3 minutes;

[0114] C4. After the residual operation ends, the solenoid valve 26 is closed, and the capillary electronic expansion valve 23 is closed after 15 seconds. The residual operation after defrosting facilitates the discharge of the refrigerant accumulated in the standby capillary group 20.

[0115] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. A refrigerant flow control method for a multi-connected dry capillary radiation heat pump system. The multi-connected dry capillary radiation heat pump system includes a heat pump unit and a plurality of capillary groups (20) for heat exchange in a room. The capillary groups (20) are used to be laid on indoor walls and / or ceilings and / or floors to achieve direct radiation heat exchange with air, and the capillary groups (20) are controlled for heat exchange by the heat pump unit. The heat pump unit includes a compressor (30). The liquid outlet of the compressor (30) is sequentially connected with an oil separator (40) and a four-way reversing valve (50) through pipelines. The four-way reversing valve (50) includes a C port (51), an E port (52), an S port (53), and a D port (54) communicated with the oil separator (40). The C port (51) is sequentially connected with an outdoor fin heat exchanger (60), a main circuit electronic expansion valve (71), a high-pressure liquid receiver (72), and a liquid pipe stop valve (73) through pipelines. The capillary group (20) includes an end liquid pipe (21) and an end gas pipe (22). The liquid pipe stop valve (73) is connected to the end liquid pipes (21) on a plurality of capillary groups (20) through a manifold (74). A capillary electronic expansion valve (23) is arranged on the pipeline between the capillary group (20) and the manifold (74). The E port (52) is connected to an air pipe stop valve (75) through a pipeline. The air pipe stop valve (75) is connected to the end air pipes (22) on a plurality of capillary tube groups (20) through a shunt pipe (76); the S port (53) is connected to a gas-liquid separator (80) through a pipeline, and an air suction pipe (90) communicating with the compressor (30) is arranged at the outlet of the gas-liquid separator (80); an exhaust temperature sensor (31) is arranged on the pipeline between the compressor (30) and the oil separator (40), a high-pressure pressure switch (41) and a high-pressure pressure sensor (42) are arranged on the pipeline between the oil separator (40) and the four-way reversing valve (50), an end liquid pipe temperature sensor (24) is arranged at the end liquid pipe (21), an end air pipe temperature sensor (25) and an electromagnetic valve (26) are arranged at the end air pipe (22), and an indoor temperature sensor (11) for detecting the temperature in the room is further included. An outdoor temperature sensor (61) for detecting the ambient temperature of the outdoor unit and a coil temperature sensor (62) for detecting the temperature of the heat exchange coil on the outdoor fin heat exchanger (60) are arranged at the outdoor fin heat exchanger (60); an air suction temperature sensor (91), a low-pressure pressure sensor (92), and a low-pressure pressure switch (93) are arranged on the air suction pipe (90), a return oil capillary (94) is connected between the oil separator (40) and the air suction pipe (90), and the connecting end of the return oil capillary (94) is located between the air suction temperature sensor (91) and the low-pressure pressure sensor (92); it is characterized in that The refrigerant flow control method for the multi-connected dry capillary radiation heat pump system includes the following steps: S1. Start the compressor and enter the soft start state. The main circuit electronic expansion valve (71) is opened to 100 - 150 steps. Each capillary group (20) enters the standby or startup state, and the startup capillary groups (20) enter the running state. S2. The capillary electronic expansion valve (23) corresponding to the standby capillary group (20) is opened to 100 - 120 steps, the solenoid valve (26) is opened, and the initial operation is for t time. S3. The solenoid valve (26) corresponding to the standby capillary group (20) is closed, and after 15 - 20 s, the capillary electronic expansion valve (23) corresponding to the standby capillary group (20) is closed. S4. The high-pressure pressure sensor (42) collects the high-pressure pressure in real time, and queries the pressure-saturation temperature comparison table to obtain the saturation temperature corresponding to the high-pressure pressure, that is, the condensation temperature Pd_t. The exhaust temperature sensor (31) collects the exhaust temperature Td in real time. The preset exhaust temperature upper limit value Tdmax = 90 - 98 °C and the target condensation temperature Pd_t.tar = 38 - 42 °C are set. Define the exhaust superheat ΔTd = Td - Pd_t, and determine the refrigerant shortage and excess: When the following conditions are simultaneously met, it is determined that the system refrigerant is short of fluorine: The unit is running, and there is one or more standby capillary groups (20); Pd_t ≤ the saturation temperature corresponding to [Pd_t.tar corresponding pressure - 3 bar]; the exhaust temperature Td ≥ Tdmax; When the following conditions are simultaneously met, it is determined that the system refrigerant is excessive: The unit is operating, and there is one or more standby capillary tube groups (20); P d_t ≥Pd_t.tar; ΔTd ≤ 15°C; S5. When the system refrigerant is short of fluorine, perform fluorine shortage control: The solenoid valve (26) corresponding to the standby capillary group (20) is opened, and the corresponding capillary electronic expansion valve (23) is opened to 100 - 120 steps. When there is excessive refrigerant in the system, carry out excessive control: The solenoid valve (26) corresponding to the standby capillary tube group (20) remains closed, and the corresponding capillary electronic expansion valve (23) is opened to 100 - 120 steps; S6. When one of the following conditions is met during the lack - of - refrigerant control, it is determined that the lack - of - refrigerant control ends: The saturation temperature corresponding to Pd_t≥[the pressure corresponding to Pd_t.tar - 0.5 bar]; Td < Tdmax-(15 - 18 °C); The unit performs defrosting operation or the whole machine shuts down; When one of the following conditions is met during the excessive control, it is determined that the excessive control ends: The saturation temperature corresponding to Pd_t≤[the pressure corresponding to Pd_t.tar - 0.5 bar]; ΔTd > 20 - 25 °C; The unit performs defrosting operation or the whole machine shuts down; S7. After the lack - of - refrigerant control ends, or after the excessive control ends, or when the system is neither lacking refrigerant nor excessive, the capillary electronic expansion valve (23) and the solenoid valve (26) corresponding to the standby capillary tube group (20) remain closed.

2. The refrigerant flow control method of the multi-connected dry capillary radiation heat pump system according to claim 1, characterized in that: The control method of the main - circuit electronic expansion valve (71) in the system includes the following steps: A1. Start the compressor and enter the soft - start stage. The main - circuit electronic expansion valve (71) is opened to the initial opening degree = 100 - 150 steps. The low - pressure pressure sensor (92) collects the low - pressure pressure in real - time, queries the pressure - saturation temperature conversion table to obtain the saturation temperature corresponding to the low - pressure pressure, that is, the evaporation temperature Ps_t. The suction - temperature sensor collects the compressor suction temperature Ts in real - time, the coil - temperature sensor (62) collects the coil temperature Tdef in real - time. Preset the minimum exhaust superheat ΔTdset.min = 15 - 18 °C and the maximum exhaust superheat ΔTdset.max = 45 - 48 °C, and define the suction superheat ΔTs = Ts - Tdef; A2. When one of the following conditions is met, the soft - start stage ends, and the main - circuit electronic expansion valve (71) adjusts the opening degree to keep ΔTs = 1 - 3 °C: Td≥90 °C; Pd_t≥Pd_t.tar; Ps_t < 3 - 4 °C; The soft - start stage lasts for 8 min; A3. When ΔTd < ΔTdset.min, the main electronic expansion valve (71) makes a small closing action to make ΔTs n = ΔTs n-1 + 1 °C until one of the following conditions is met: ΔTdset.min≤ΔTd≤ΔTdset.max; The main - circuit electronic expansion valve (71) reaches the minimum opening degree = 80 - 100 steps; When ΔTd > ΔTdset.max or Td > 100 °C, the main electronic expansion valve (71) performs an opening operation to make ΔTs n = ΔTs n-1 -1 °C until one of the following conditions is met: ΔTdset.min≤ΔTd≤ΔTdset.max and Td≤100 °C; The main - circuit electronic expansion valve (71) reaches the maximum opening degree = 300 - 400 steps; where ΔTs n is the target suction superheat to be adjusted in this cycle, and ΔTs n-1 is the suction superheat of the previous cycle, and the adjustment cycle is 3 min.

3. The refrigerant flow control method of the multi-connected dry capillary radiation heat pump system according to claim 1, characterized in that: The operating state of the on - heating - operation start - up capillary tube group (20) includes the following steps: B1. The solenoid valve (26) is opened, and the capillary electronic expansion valve (23) is opened to an initial opening degree = 350 - 450 steps. The end liquid pipe temperature sensors (24) corresponding to the capillary tube group (20) during startup detect the liquid pipe temperatures TeL.i of each liquid pipe in real time, and the average value of the liquid pipe temperatures corresponding to the capillary tube group (20) during startup is calculated. B2. When the temperature of a liquid pipe is such that, the capillary tube electronic expansion valve (23) corresponding to this liquid pipe closes 15 steps every 3 minutes until the capillary tube electronic expansion valve (23) reaches the minimum opening degree = 200 - 250 steps or When the temperature of the liquid pipe is such that, the capillary tube electronic expansion valve (23) corresponding to this liquid pipe closes 15 steps every 3 minutes until the capillary tube electronic expansion valve (23) reaches the maximum opening degree = 450 - 480 steps or 4. The refrigerant flow control method of the multi-connected dry capillary radiation heat pump system according to claim 3, characterized in that: During the refrigeration operation, the main - circuit electronic expansion valve of the outdoor main unit is fully opened to 480 steps, the capillary electronic expansion valve (23) corresponding to the standby capillary tube group (20) is closed, and the corresponding solenoid valve (26) is opened.

5. The refrigerant flow control method of the multi-connected dry capillary radiation heat pump system according to claim 1, characterized in that: When the system issues a defrosting signal during the refrigeration operation, its defrosting process includes the following steps: C1. The four - way reversing valve (50) is powered off and reversed, and the capillary electronic expansion valve (23) corresponding to the standby capillary tube group (20) is opened to the defrosting opening degree = 250 - 300 steps; C2. After the system receives the defrost completion command, the capillary electronic expansion valve (23) corresponding to the standby capillary tube group (20) is adjusted to the standby opening degree = 100 - 120 steps; C3. After defrosting, perform residual operation, and the solenoid valve (26) remains open for 2 - 3 minutes; C4. After the residual operation ends, the solenoid valve (26) closes, and the capillary electronic expansion valve (23) closes after 15 seconds.

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