CN108895697B

CN108895697B - Compression condensing system with refrigeration capacity being adjusted steplessly

Info

Publication number: CN108895697B
Application number: CN201810360343.7A
Authority: CN
Inventors: 昝世超; 张伟; 张欢; 刘贵芳; 黄静; 魏昇
Original assignee: HEFEI GENERAL ENVIRONMENT CONTROL TECHNOLOGY CO LTD; Hefei General Machinery Research Institute Co Ltd
Current assignee: HEFEI GENERAL ENVIRONMENT CONTROL TECHNOLOGY CO LTD; Hefei General Machinery Research Institute Co Ltd
Priority date: 2018-04-20
Filing date: 2018-04-20
Publication date: 2020-12-25
Anticipated expiration: 2038-04-20
Also published as: CN108895697A

Abstract

The invention belongs to the field of compression condensing systems, and particularly relates to a compression condensing system with stepless regulation of refrigeration capacity, which comprises a compression condensing part, a system self-adaption part, a variable capacity regulation part and a measurement control part; the system self-adaptation part is including breathing in cooling valve subassembly and hot gas bypass valve subassembly, the cooling valve subassembly of breathing in all links to each other through the pipeline with condenser, varactor regulation part, hot gas bypass valve subassembly all links to each other through the pipeline with oil content, varactor regulation part, cooling valve subassembly of breathing in, hot gas bypass valve subassembly all link to each other with vapour and liquid separator through the pipeline. The invention has the beneficial effects that: the invention provides a compression and condensation system with stepless regulation of refrigeration capacity, which controls a single expansion valve and related parameters through a measurement control system and realizes stepless regulation of the refrigeration capacity of the system on the basis of ensuring stable and reliable operation of the system.

Description

Compression condensing system with refrigeration capacity being adjusted steplessly

Technical Field

The invention belongs to the field of compression condensing systems, and particularly relates to a compression condensing system with stepless refrigeration capacity adjustment.

Background

The traditional performance test device for the refrigeration air conditioner product usually adopts a compressor with fixed capacity, and then uses electric heating with adjustable capacity to carry out opposite flushing on cold quantity so as to achieve constant temperature between test environments. This method will cause energy waste because the electric heating is used to offset the cooling capacity of the compressor. In order to solve the problem, the best method is to realize that the cold load and the heat load required by the environment can be independently and steplessly adjusted, only electric heating is needed to be put into the environment when the cold load exists in the environment, the balance of the cold load can be solved only by driving the electric heating by a power regulator, and the difficulty of the scheme is that the refrigeration capacity of the system needs to be steplessly adjusted when the heat load is balanced.

At present, the variable capacity regulation technology, the multi-machine parallel variable capacity technology and the liquid refrigerant storage variable capacity technology are mainly used at home and abroad, the latter two modes are not suitable for being popularized in a refrigerating air conditioner test device due to poor control precision, the variable frequency regulation technology has high control precision, but has higher cost and more complex control and is not beneficial to large-scale popularization, and therefore, a compression condensing system is developed in the text and can realize stepless regulation of the refrigerating capacity from zero to full load. The system introduces a hot gas bypass valve, an air suction cooling expansion valve, an electronic expansion valve and other auxiliary valve parts, controls the single sub expansion valve and related parameters through an automatic control system, and realizes stepless adjustment of the refrigerating capacity of the system on the basis of ensuring stable and reliable operation of the system.

Disclosure of Invention

In order to solve the above problems, the present invention aims to provide a compression and condensation system with stepless refrigeration capacity adjustment, which controls a single expansion valve and related parameters by a measurement control system, and realizes stepless refrigeration capacity adjustment of the system on the basis of ensuring stable and reliable operation of the system.

The invention provides the following technical scheme:

a compression condensing system with refrigeration capacity being adjusted steplessly comprises a compression condensing part, a system self-adapting part, a variable capacity adjusting part and a measurement control part;

the compression condensing part comprises a compressor, a condenser, an oil component and a gas-liquid separator, the compressor is connected with the gas-liquid separator and the oil component through pipelines, and the condenser is connected with the oil component through a pipeline;

the system self-adaptive part comprises a suction cooling valve assembly and a hot gas bypass valve assembly, the suction cooling valve assembly is connected with the condenser and the variable capacity regulating part through pipelines, the hot gas bypass valve assembly is connected with the oil component and the variable capacity regulating part through pipelines, and the suction cooling valve assembly and the hot gas bypass valve assembly are connected with the gas-liquid separator through pipelines;

the measurement control part is connected with the system self-adapting part and the variable capacity adjusting part through circuits.

Preferably, the suction cooling valve assembly comprises a suction cooling valve and a first electromagnetic valve connected with the suction cooling valve, and the hot gas bypass valve assembly comprises a hot gas bypass valve and a second electromagnetic valve connected with the hot gas bypass valve; the first electromagnetic valve is connected with the condenser and the variable volume adjusting part through pipelines, the second electromagnetic valve is connected with the oil content and the variable volume adjusting part through pipelines, and the air suction cooling valve and the hot gas bypass valve are connected with the gas-liquid separator through pipelines.

Preferably, the varactor adjusting part includes electronic expansion valve subassembly, hot gas defrosting valve subassembly, divides liquid device and evaporimeter, electronic expansion valve subassembly and solenoid valve one, the condenser all passes through the pipeline and links to each other, hot gas defrosting valve subassembly and solenoid valve two, oil content all pass through the pipeline and link to each other, electronic expansion valve subassembly, hot gas defrosting valve subassembly all pass through the pipeline and divide liquid device to link to each other, divide liquid device still to link to each other with the evaporimeter.

Preferably, the electronic expansion valve assembly comprises an electronic expansion valve and a third electromagnetic valve connected with the electronic expansion valve, the hot gas defrosting valve assembly comprises a hot gas defrosting valve and a fourth electromagnetic valve connected with the hot gas defrosting valve, the third electromagnetic valve is connected with the first electromagnetic valve and the condenser through pipelines, the fourth electromagnetic valve is connected with the second electromagnetic valve and the oil component through pipelines, and the electronic expansion valve and the hot gas defrosting valve are connected with the liquid separating device through pipelines.

Preferably, the measurement control part comprises a PLC-CPU unit, a PLC analog input module, a PLC analog output module, a PLC switching value output module, a cold and hot regulation meter, a temperature sensor and a pressure sensor, wherein the PLC-CPU unit is electrically connected with the PLC analog input module, the PLC analog output module and the PLC switching value output module, the PLC switching value output module is electrically connected with a first electromagnetic valve, a second electromagnetic valve, a third electromagnetic valve and a fourth electromagnetic valve, the PLC analog input module is electrically connected with the temperature sensor, the pressure sensor and the cold and hot regulation meter, the PLC analog output module is electrically connected with the electronic expansion valve, and the temperature sensor and the pressure sensor are arranged on an outlet pipe of the evaporator.

The invention has the beneficial effects that: the invention provides a compression and condensation system with stepless regulation of refrigeration capacity, which controls a single expansion valve and related parameters through a measurement control system and realizes stepless regulation of the refrigeration capacity of the system on the basis of ensuring stable and reliable operation of the system.

Drawings

FIG. 1 is a schematic diagram of a compression and condensation system;

FIG. 2A is a schematic diagram of enthalpy of compression and condensation system versus intermediate cold output of adaptive variable capacity system;

FIG. 2B is a diagram of the principle enthalpy of compression-adaptive variable capacity system 100% cold output for a compression condensing system;

FIG. 3 is a graph of the major factors of electronic expansion valve control;

FIG. 4A is a diagram showing the relationship between the output signals of the electronic expansion valve and the cold/heat meter when a compressor is turned on;

FIG. 4B is a diagram showing the relationship between the electronic expansion valve of the first compressor and the output signal of the cold/hot meter when the two compressors are started;

FIG. 4C is a graph showing the relationship between the electronic expansion valve of the compressor and the output signal of the cold/hot meter after the two compressors are opened.

The designations in the drawings have the following meanings:

1-compressor 2-condenser 4-oil content 9-electromagnetic valve three 10-electronic expansion valve 12-evaporator 13-gas-liquid separator 14-suction cooling valve 15-electromagnetic valve one 16-hot gas bypass valve 17-electromagnetic valve two 18-electromagnetic valve four 19-hot gas defrosting valve 20-temperature sensor 21-pressure sensor

Detailed Description

The present invention will be described in detail with reference to the following examples.

The compression condensing system of the invention is mainly divided into four parts: the device comprises a compression condensation part, a system self-adaption part, a variable capacity adjusting part and a measurement control part;

a compression condensation part: the part mainly comprises a compressor 1, a condenser 2, oil 4 and a gas-liquid separator 13. The condenser adopts a water-cooled type, the condenser fully cools the high-temperature high-pressure gaseous refrigerant, heat is taken away by cooling water, and the refrigerant is changed into a high-pressure liquid refrigerant after passing through the condenser.

The system self-adapting part: the system mainly comprises a suction cooling valve 14, a hot gas bypass valve 16, a first electromagnetic valve 15 and a second electromagnetic valve 17 which correspond to the suction cooling valve, wherein the compressor has an operating range, the compressor can give a fault alarm when operating in a limit state and can influence the service life of the compressor, in order to ensure that the compressor always operates in a comfortable area of the operating range when the capacity requirement of the whole system is changed, the system is provided, the suction cooling valve mainly regulates the flow rate of high-pressure liquid refrigerant from a condenser (the process completes throttling evaporation), the hot gas bypass valve mainly regulates the flow rate of high-temperature high-pressure gaseous refrigerant from the exhaust side of the compressor (the process completes isenthalpic throttling), the suction cooling valve and the high-pressure liquid refrigerant are mixed and then subjected to heat exchange, and the heat exchange is recombined into low-temperature low-pressure gaseous refrigerant. The system can ensure that the compressor has proper suction pressure and enough superheat degree under the condition that the capacity requirement of the evaporator is zero, namely the electronic expansion valve is completely closed, so that the whole system can be separated from the evaporator to operate independently, and a foundation is provided for stepless regulation of the capacity of the evaporator. The pressure-enthalpy diagram of the system principle is shown in figure 2.

A variable-capacitance adjusting part: the part mainly comprises an electronic expansion valve 10 and a corresponding electromagnetic valve III 9 thereof, a liquid separating device 11, an evaporator 12, a hot gas defrosting valve 19 and a corresponding electromagnetic valve IV 18 thereof, the part mainly provides a cold source capable of being adjusted in a stepless mode for the system, and after the former parts are taken as a basis, the flow of refrigerant flowing through the evaporator can be controlled according to requirements as long as the opening degree of the electronic expansion valve is adjusted, so that the stepless adjustment of the cold quantity is realized. When the evaporation pressure is too low under part of working conditions, the hot gas defrosting valve 19 can be opened to complete defrosting in order to prevent the evaporator from frosting.

A measurement control section: the part mainly comprises a PLC-CPU unit, a PLC analog input module, a PLC switching value output module, a PLC analog output module, a cold and hot adjusting meter, a temperature sensor 20, a pressure sensor 21, a solenoid valve III 9 and a solenoid valve IV 18 which respectively correspond to an electronic expansion valve 10 and a hot gas defrosting valve 19, wherein the solenoid valve III 9 is opened when the electronic expansion valve 10 needs to work, and the solenoid valve IV 18 is opened when the hot gas defrosting valve 19 needs to work; the temperature sensor and the pressure sensor are mainly used for collecting the refrigerant pressure and the refrigerant temperature on the outlet main pipe of the evaporator and converting the refrigerant pressure and the refrigerant temperature into internal digital signals through the PLC, so that the superheat degree of the refrigerant at the outlet of the evaporator at the moment is indirectly calculated; the cold and hot adjusting meter is mainly used for outputting the refrigerating capacity demand percentage of the evaporating coil, the signal is also collected by the PLC, and the actual output value of the electronic expansion valve is finally determined through internal comprehensive calculation.

The schematic diagram of the system is shown in fig. 1, in the system, high-pressure gas discharged by a compressor is divided into two parts, one part is condensed by a condenser and then liquid-phase throttling, evaporation and refrigeration are carried out, the other part is subjected to gas-phase isenthalpic throttling by hot gas through a regulating valve to reach the same pressure of liquid phase, and then the two parts of fluid are mixed to a compressor suction state. The coupling action of the key valve piece can ensure that the compressor runs in a comfortable state and can also be combined with the control of the electronic expansion valve to finish the accurate stepless regulation of the cooling capacity.

The compression condensing system mainly comprises an air suction cooling valve, a hot gas bypass valve, an electronic expansion valve, an evaporation pressure regulating valve, an oil return electromagnetic valve and other auxiliary valve parts, wherein the air suction cooling valve and the hot gas bypass valve are used for matching and adjusting basic air suction pressure and air suction superheat degree of a compressor and ensuring the operation of the compressor under a full-load working condition, the electronic expansion valve and a control system are used for ensuring that the output cold quantity of the system is continuously adjustable, and the whole system can be used for a refrigerating air conditioner product performance testing device after being matched with an evaporator and is used for realizing accurate control of the environment temperature.

Control strategy

Hot gas bypass valve and intake cooling valve: in order to ensure that the system can stably operate, the compressor is started firstly after a starting command, meanwhile, the hot gas bypass valve and the air suction cooling electromagnetic valve are opened, the two valves act together, the whole compression and condensation system can complete circulation when a cold quantity demand signal of the system is zero, the whole system is ensured to operate under the lowest power consumption, the opening of the electronic expansion valve is increased when the cold quantity demand signal is increased, and the evaporator is put into operation. If the compressor fails to start, the two valves are closed accordingly.

Liquid pipe solenoid valve: in the closed state for a period of time (15S) during which the compressor is initially operated, the refrigerant stored in the evaporator first participates in the circulation so as not to cause a liquid impact due to an excessive amount of refrigerant stored in the evaporator to protect the compressor.

Hot-gas defrosting electromagnetic valve: the hot gas defrosting electromagnetic valve is matched with the hot gas defrosting valve for use to prevent the evaporator coil from frosting, the hot gas defrosting electromagnetic valve is opened when the compressor is in an operating state and the cold requirement is less than 10%, the hot gas defrosting electromagnetic valve is closed when the cold requirement is recovered to be more than 40%, and the middle has a return difference of 30%.

Electronic expansion valve: the opening of the electronic expansion valve determines the output of the cooling capacity of the system, the accuracy of the system for controlling the ambient temperature depends on the control of the electronic expansion valve, the control of the electronic expansion valve is the most critical control point in the whole system, the SER and SEI series expansion valves of the SPORLAN are adopted, the expansion valve controller adopts the IB series controller of the SPORLAN, the control resolution of the valve is 1/1600, and the requirement of the output accuracy 1/1000 of the regulation table is better. The main factors controlling the valve are shown in figure 3.

In order to realize accurate control of the electronic expansion valve, OMRON CJ2 series PLC is introduced, CJ1W-PTS51 temperature input units are used for collecting and converting the suction temperature of the compressor, CJ1W-AD081-V1 analog quantity input units are used for collecting and converting the suction pressure of the compressor, and CJ1W-DA08C analog quantity output units are used for realizing the opening control of the electronic expansion valve, and the specific implementation of the nodes is described as follows:

collecting the air suction pressure: a pressure sensor is arranged at an air suction port of the compressor, a direct current 4-20 mA signal is output, and the signal enters a PLC analog quantity acquisition module and is converted into a pressure signal;

collecting the air suction temperature: the thermocouple is directly connected to the PLC thermocouple module by arranging the thermocouple on the air suction pipeline of the compressor, and is converted into a temperature signal from the inside of the module; as shown in table 1 in detail,

TABLE 1

Calculation of degree of superheat of intake air: and calculating the air suction temperature and the air suction pressure of the compressor according to the two steps, and storing a working medium physical property table in a PLC memory, wherein the physical property table selects data between 50 ℃ below zero and 50 ℃ according to actual needs and stores the data in a DM area of the PLC, and because the area of the PLC is a power-off storage area, all pressure and data corresponding to the saturation temperature are stored in the area and cannot be lost due to the power-off of a system. Because of the limitation of storage capacity, all data of a refrigerant working medium physical property table can not be stored in the PLC, the scheme adopts a method of storing a group of data at intervals of 10kPa, the accuracy and the practicability are considered, a practical interpolation method of a program is used for calculating the saturation temperature corresponding to each actual pressure, and then the superheat degree is calculated according to the difference between the actual temperature and the saturation temperature.

Outputting a cold and hot meter: the UT series cold and heat meter is adopted, cold side signals of the cold and heat meter are introduced into the PLC and serve as the most main adjusting signal source of the electronic expansion valve, and as the system can be composed of one compressor or two compressors, for the system of one compressor, adjusting signals output by the cold and heat meter can be directly synthesized with other conditions and then directly output to the electronic expansion valve; for a system formed by two compressors, when only one compressor is started, the output of a cold and heat meter is 0-100%, and the expansion valve corresponding to the compressor is directly adjusted; when two compressors are started, firstly, which one is started firstly, is judged, 0-50% of signal parts (namely DC 4-12 mA) of the cold and hot meters are used firstly, 50-100% of the cold and hot meters are used secondly (namely DC 12-20 mA), 0-50% of actual signals of the cold and hot meters correspond to 0-100% of the opening degree of the electronic expansion valve of the single compressor, 50-100% of the cold and hot meters correspond to 0-100% of the opening degree of the electronic expansion valve of the later-started compressor, all conditions are marked by the following curves, as shown in fig. 4, an X axis represents output signals of the cold and hot meters (0-100% corresponds to 4-20 mA), and a Y axis represents signals (0-100% corresponds to DV 4-20 mA) which are output to the electronic expansion valve after being converted by a PLC.

Controlling an electronic expansion valve: except for the control of a hot gas bypass electromagnetic valve, an air suction cooling electromagnetic valve, a liquid pipe electromagnetic valve, a hot gas defrosting electromagnetic valve and other auxiliary valves, the cold output by the whole system is finally controlled by the opening degree of an electronic expansion valve, the key steps generate an output independently, and the system finally integrates the outputs: a. the output value calculated by the suction superheat PID algorithm; b. the output value calculated by the lowest suction pressure PID algorithm; c. the output value generated by the combined action of the cold and hot meter and the PLC; d. the maximum opening value set during system debugging is finally taken as the output value of the electronic expansion valve during PLC calculation, so that the stable operation of the whole system is realized by accurately controlling the main electronic expansion valve and a series of auxiliary valves, and the stepless regulation of cooling capacity is completed.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A compression condensing system with refrigeration capacity being adjusted steplessly is characterized by comprising a compression condensing part, a system self-adaptive part, a variable capacity adjusting part and a measurement control part;

the compression condensing part comprises a compressor (1), a condenser (2), oil (4) and a gas-liquid separator (13), the compressor (1), the gas-liquid separator (13) and the oil (4) are connected through pipelines, and the condenser (2) and the oil (4) are connected through pipelines;

the system self-adaptive part comprises a suction cooling valve assembly and a hot gas bypass valve assembly, the suction cooling valve assembly is connected with the condenser (2) and the variable-capacity regulating part through pipelines, the hot gas bypass valve assembly is connected with the oil component (4) and the variable-capacity regulating part through pipelines, and the suction cooling valve assembly and the hot gas bypass valve assembly are connected with a gas-liquid separator (13) through pipelines;

the measurement control part is connected with the system self-adaptive part and the variable capacitance adjusting part through circuits;

the air suction cooling valve assembly comprises an air suction cooling valve (14) and a first electromagnetic valve (15) connected with the air suction cooling valve (14), and the hot gas bypass valve assembly comprises a hot gas bypass valve (16) and a second electromagnetic valve (17) connected with the hot gas bypass valve (16); the first electromagnetic valve (15) is connected with the condenser (2) and the variable-volume adjusting part through pipelines, the second electromagnetic valve (17) is connected with the oil component (4) and the variable-volume adjusting part through pipelines, and the air suction cooling valve (14) and the hot gas bypass valve (16) are connected with the gas-liquid separator (13) through pipelines;

the variable-capacitance adjusting part comprises an electronic expansion valve assembly, a hot gas defrosting valve assembly, a liquid separating device (11) and an evaporator (12), the electronic expansion valve assembly is connected with a first electromagnetic valve (15) and a condenser (2) through pipelines, the hot gas defrosting valve assembly is connected with a second electromagnetic valve (17) and an oil component (4) through pipelines, the electronic expansion valve assembly and the hot gas defrosting valve assembly are connected with the liquid separating device (11) through pipelines, and the liquid separating device (11) is further connected with the evaporator (12);

the electronic expansion valve assembly comprises an electronic expansion valve (10) and a solenoid valve III (9) connected with the electronic expansion valve (10), the hot gas defrosting valve assembly comprises a hot gas defrosting valve (19) and a solenoid valve IV (18) connected with the hot gas defrosting valve (19), the solenoid valve III (9), the solenoid valve I (15) and the condenser (2) are connected through pipelines, the solenoid valve IV (18), the solenoid valve II (17) and the oil component (4) are connected through pipelines, and the electronic expansion valve (10) and the hot gas defrosting valve (19) are connected with the liquid separating device (11) through pipelines;

the measurement control part comprises a PLC-CPU unit, a PLC analog input module, a PLC analog output module, a PLC switching value output module, a cold and hot adjusting meter, a temperature sensor (20) and a pressure sensor (21), wherein the PLC-CPU unit is electrically connected with the PLC analog input module, the PLC analog output module and the PLC switching value output module, the PLC switching value output module is electrically connected with a first electromagnetic valve (15), a second electromagnetic valve (17), a third electromagnetic valve (9) and a fourth electromagnetic valve (18), the PLC analog input module is electrically connected with the temperature sensor (20), the pressure sensor (21) and the cold and hot adjusting meter, the PLC analog output module is electrically connected with an electronic expansion valve (10), and the temperature sensor (20) and the pressure sensor (21) are arranged on an outlet pipe of the evaporator (12);

the control method of the electronic expansion valve comprises the following steps that the system integrates the following outputs:

a. the output value calculated by the suction superheat PID algorithm;

b. the output value calculated by the lowest suction pressure PID algorithm;

c. the output value generated by the combined action of the cold and hot meter and the PLC;

d. setting a maximum opening value during system debugging;

and taking the minimum value of the four values as the output value of the electronic expansion valve during the final PLC calculation.