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CN-122015349-A - Subcooler and deep subcooler for refrigerating system and control method thereof

CN122015349ACN 122015349 ACN122015349 ACN 122015349ACN-122015349-A

Abstract

The invention discloses a subcooler and a deep subcooler for a refrigerating system and a control method thereof, and belongs to the technical field of refrigeration. The deep subcooler comprises a subcooling heat exchange unit, an independent cold source loop and a pressure control valve, wherein the subcooling heat exchange unit is connected in series between a high-pressure liquid storage device and a throttling device, the primary liquid refrigerant is deeply cooled to be equal to or close to a target value of evaporation temperature by utilizing low-temperature cold energy provided by a low-pressure evaporation system or the independent cold source loop, the independent cold source is driven by a compressor with the minimum refrigerating energy in the system, and an air return pipeline of the independent cold source is bridged with air return pipelines of other compressors of the system through an outlet pressure balance valve so as to fully utilize the abundant refrigerating energy. By monitoring the temperature of the supercooled liquid, the opening of the pressure control valve is fed back and regulated to change the evaporating pressure of the cold source loop, so that the accurate closed-loop control of the supercooling temperature is realized, the throttling flash gas can be obviously reduced or even eliminated, the effective refrigerating capacity of unit refrigerant and the heat exchange efficiency of the evaporator are improved, and the energy efficiency of the system is greatly improved.

Inventors

  • WANG JUNTING
  • XUE QIUXIA
  • MA XINYU
  • ZHANG SHUN
  • ZHANG SHOUGUO

Assignees

  • 菏泽市花王科技工贸有限公司
  • 张守国

Dates

Publication Date
20260512
Application Date
20260407

Claims (9)

  1. 1. The subcooler and the deep subcooler for the refrigerating system comprise a main compressor (1), an auxiliary compressor (2), a condenser (3), a high-pressure liquid receiver (4), a subcooling heat exchange unit (5), a throttling device (6), an evaporator (7) and an outlet pressure control valve (8) which are sequentially connected through pipelines, and are characterized by further comprising the subcooling heat exchange unit (5) and a primary side flow path and a secondary side flow path which are mutually heat exchanged, wherein the primary side flow path is connected in series between the outlet of the high-pressure liquid receiver (4) and the inlet of the throttling device (6); the refrigerator is provided with an independent cold source loop which is used for providing cold for a secondary side flow path of the supercooling heat exchange unit (5), the cold source loop comprises a supercooling special auxiliary compressor and a pressure control valve (8), the cold source loop is arranged on a return air pipe of the independent cold source loop or on the supercooling heat exchange unit (5) and is used for regulating and stably controlling the evaporation pressure of the secondary side of the supercooling heat exchange unit (5) to be stable at a saturation pressure which is lower than the evaporation pressure of a main refrigerating system by 3 ℃; wherein the supercooling heat exchange unit (5) is configured to cool the primary liquid refrigerant flowing through the primary side flow path thereof to a target temperature Reducing the flash gas generation amount of the primary liquid refrigerant throttled by the throttling device (6) to 0; The target temperature The method meets the following conditions: In the formula, The temperature of the supercooled liquid is expressed as degrees centigrade (°c); the evaporation temperature of the evaporator (7) of the main refrigeration system is given in degrees celsius (°c).
  2. 2. Subcooler and deep subcooler for a refrigeration system according to claim 1, characterized in that the auxiliary compressor dedicated for subcooling has a rated refrigeration capacity smaller than or equal to the rated refrigeration capacity of the main compressor (1) of the refrigeration system, and preferably is the one compressor of the refrigeration system having the smallest rated refrigeration capacity.
  3. 3. The subcooler and deep subcooler for a refrigeration system of claim 1 wherein the heat transfer temperature difference when the device is configured as a deep subcooler I.e. the primary liquid refrigerant temperature after subcooling is 3 ℃ higher than the evaporator (7) evaporating temperature, i.e. the cold source circuit evaporating temperature is 3 ℃ lower than the main system evaporator (7) evaporating temperature, the target temperature when the device is configured as a subcooler The difference between the temperature and the actual temperature is 3 ℃, and the generation amount of the flash gas is less than or equal to 2 percent at the moment; The actual temperature The method meets the following conditions: In the formula, The temperature of the supercooled liquid is expressed as degrees centigrade (°c); the evaporation temperature of the evaporator (7) of the main refrigeration system is given in degrees celsius (°c).
  4. 4. The subcooler and deep subcooler for a refrigeration system as set forth in claim 1 wherein the heat transfer temperature difference The range of the values is as follows To the point of Preferred heat transfer temperature differences Is that More preferably, the supercooling heat exchange unit (5) is configured to have a preset heat exchange area so as to perform heat transfer at the temperature difference Is that Cooling the primary liquid refrigerant to the target temperature (To+3°C)。
  5. 5. The subcooler and deep subcooler for a refrigeration system as set forth in claim 1, wherein the subcooling heat exchange unit (5) is one of a vertical or horizontal shell and tube heat exchanger, a plate heat exchanger, a double pipe heat exchanger and a heat exchange tube in a vessel.
  6. 6. A subcooler and deep subcooler for a refrigeration system as set forth in claim 1 wherein said primary liquid refrigerant is all active refrigerant.
  7. 7. A refrigeration system comprising the deep subcooler and subcooler of any one of claims 1-6.
  8. 8. A control method for the subcooler and the deep subcooler as set forth in any one of claims 1-6, comprising the steps of: s1, setting target temperature The target temperature of the deep subcooler meets the following conditions: In the formula, The evaporation temperature of the evaporator (7) is given in degrees celsius (°c); the evaporation temperature of the main refrigeration system is expressed as degrees centigrade (°c); the target temperature of the subcooler meets the following conditions: + In the formula, The evaporation temperature of the evaporator (7) is given in degrees celsius (°c); is a preset heat transfer temperature difference, the unit is degrees centigrade (°c), and ; Evaporating temperature for the main refrigeration system; the evaporation temperature of the main refrigeration system is expressed as degrees centigrade (°c); S2, when the device is configured as a subcooler, starting a refrigerating system, and controlling the subcooling temperature by adjusting the liquid supply amount of the secondary side of the subcooling heat exchange unit (5), when the device is configured as a deep subcooler, starting an independent cold source loop, and controlling the evaporating temperature of the secondary side to be always lower than the evaporating temperature of the main refrigerating system by using a pressure control valve (8); S3, monitoring the supercooling temperature of the primary liquid refrigerant flowing out from the primary side flow outlet of the supercooling heat exchange unit (5) ; S4, according to And (3) with Correspondingly adjusts the operation parameters to make Is stabilized by Or to+3 ℃, wherein the subcooling heat exchange unit (5) is adjusted To ensure the subcooling liquid temperature by adjusting the secondary side liquid supply amount in the subcooler mode The evaporation temperature is 3 ℃ or lower, the formation amount of flash gas is less than or equal to 2%, and the opening degree of the pressure control valve (8) is adjusted in a deep subcooler mode so as to control the evaporation pressure of the secondary side of the subcooling heat exchange unit (5) to be lower than the formation amount of the flash gas at the time of 3 ℃ of the main refrigeration system.
  9. 9. The control method according to claim 8, wherein in the step S1, the heat transfer temperature difference The range of the values is as follows To the point of Preferred heat transfer temperature differences Is that 。

Description

Subcooler and deep subcooler for refrigerating system and control method thereof Technical Field The invention relates to the technical field of refrigeration systems, in particular to a subcooler and a deep subcooler for a refrigeration system and a control method thereof. Background In a conventional vapor compression refrigeration cycle, after a high pressure condensed liquid refrigerant flows through a throttling device, a large amount of flash gas is generated because the pre-throttling temperature is higher than the saturation temperature corresponding to the post-throttling pressure. This phenomenon results from the inherent nature of thermodynamic "sensible heat deficiency, latent heat replenishment", in that the throttling process is approximated by an adiabatic isenthalpic process, the sensible heat of the liquid before throttling being insufficient to provide the required enthalpy at the post-throttling pressure, and part of the liquid having to absorb latent heat by evaporation to make up for this enthalpy difference, thus forming a flash gas (flash phenomenon). The flash gas cannot effectively participate in the whole refrigeration cycle through the phase change latent heat, only can exchange heat in a sensible heat form, and directly has three adverse effects, namely, firstly, the effective refrigerating capacity of a unit mass refrigerant is reduced, the flash gas flows through the evaporator as a gas phase, the refrigerating effect of the phase change latent heat cannot be exerted, secondly, the flow resistance of a system is increased, the flow resistance of a gas-liquid two-phase flow is far greater than that of single-phase liquid, the actual evaporation pressure of the evaporator is increased, the compressor needs to consume more effective work to maintain the whole refrigeration cycle, thirdly, the effective heat exchange area of the evaporator is occupied, the flash gas needs to occupy a large amount of the actual heat exchange area of the evaporator for passing, the effective heat exchange efficiency of the evaporator is reduced, the actual evaporation pressure is possibly reduced, and the compression work is further increased. Eventually leading to a significant reduction in the coefficient of energy efficiency (COP) of the system. In order to reduce the flash gas, various supercooling schemes appear in the prior art, but all have obvious technical limitations: (1) The conventional regenerative cycle supercooling is that the supercooling degree is limited by the temperature of the returned air by using the supercooling of the returned air, and the temperature of liquid after supercooling is higher than the evaporation temperature by 8 ℃ generally, so that deep supercooling is difficult to realize, and a large amount of flash gas still exists after throttling; (2) Two-stage compression and intermediate cooling, namely, the liquid refrigerant can be supercooled to about 5 ℃ higher than the saturation temperature corresponding to the intermediate pressure, the supercooling depth is limited, and flash gas cannot be fundamentally inhibited; (3) The existing external supercooling unit or economizer can provide extra cooling capacity, but the supercooling temperature of a cold source is usually too high, so that the temperature of supercooled liquid is not matched with that of a main system, the energy consumption is high, precise closed-loop control is lacked, and the supercooling effect is unstable. In summary, the prior art is unable to radically eliminate the choked flash gas. Therefore, there is a need in the industry for a refrigeration system subcooling device that can deep subcool a primary liquid refrigerant in a main cycle to a temperature near or equal to the evaporating temperature, minimize or even completely eliminate flash gas, operate stably and controllably, and have optimal system energy efficiency. Disclosure of Invention In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a subcooler and a deep subcooler for a refrigeration system and a control method thereof, so as to solve the above-mentioned problems in the prior art. To achieve the above object, a specific embodiment of the present invention provides a deep subcooler for a refrigeration system comprising a main compressor, an auxiliary compressor, a condenser, a high pressure receiver, a subcooling heat exchange unit, a throttling device, an evaporator, and an outlet pressure control valve connected in this order by piping, a subcooling heat exchange unit having a primary side flow path and a secondary side flow path which exchange heat with each other, the primary side flow path being connected in series between an outlet of the high pressure receiver and an inlet of the throttling device, a subcooler having a separate cold source circuit for supplying cold to the secondary side flow path of the subcooling heat exchange unit, the cold source circuit comprisi