Device and control method for preventing liquid return in a compression condensing unit

Abstract

The present invention relates to a device for preventing liquid return in a compression condensation unit, comprising: a suction pressure sensor installed on the suction pipe connected to the suction port of the compressor for detecting the suction pressure; a suction temperature sensor installed on the suction pipe for detecting the suction temperature; a cut-off solenoid valve installed on the suction pipe and located between the compressor and the evaporator; an electronic expansion valve installed on the suction pipe and in parallel with the cut-off solenoid valve; an electric heating device installed on the suction pipe and located between the electronic expansion valve and the compressor; and a controller respectively connected to the suction pressure sensor, the suction temperature sensor, the cut-off solenoid valve, the electronic expansion valve and the electric heating device. This device can effectively avoid liquid return during the operation of the compressor, prevent the compressor from being damaged by liquid return, and has the advantages of simple structure, convenient installation and control, low cost, high operability and good prevention effect on liquid hammer.

Description

Technical Field

[0001] The present invention relates to a refrigeration system, in particular to a device and a control method for preventing liquid return in a compression condensation unit. Background Art

[0002] During the operation of a refrigeration system, due to reasons such as excessive refrigerant charge, improper adjustment or too large an opening of an expansion valve, incorrect closing or leakage of a solenoid valve, and poor evaporation of an evaporator, the refrigerant in the suction pipeline may not be completely vaporized, resulting in a large amount of refrigerant liquid in the return air pipeline of the system. Since the liquid is incompressible, it will not only cause impact and vibration when entering the compressor, but may also damage the compressor.

[0003] Conventional methods for preventing liquid slugging include: installing a gas separator in the suction pipeline, selecting a crankcase heating wire, etc. However, due to the failure of equipment or measures during actual operation, the risk of liquid return still exists. Summary of the Invention

[0004] To solve the above problems, the present invention provides a device for preventing liquid return in a compression condensation unit that can effectively avoid liquid return when the compressor is running. The specific technical solution is as follows:

[0005] A device for preventing liquid return in a compression condensation unit includes: a suction pressure sensor installed on the suction pipeline connected to the suction port of the compressor for detecting the suction pressure; a suction temperature sensor installed on the suction pipeline for detecting the suction temperature; a cut-off solenoid valve installed on the suction pipeline and located between the compressor and the evaporator; an electronic expansion valve installed on the suction pipeline and in parallel with the cut-off solenoid valve; an electric heating device installed on the suction pipeline and located between the electronic expansion valve and the compressor; and a controller respectively connected to the suction pressure sensor, the suction temperature sensor, the cut-off solenoid valve, the electronic expansion valve, and the electric heating device for controlling the suction superheat of the suction pipeline according to the suction temperature and the suction pressure.

[0006] Preferably, the suction temperature sensor includes: a first temperature sensor located between the cut-off solenoid valve and the evaporator; and a second temperature sensor located between the electric heating device and the compressor; the suction superheat includes a first suction superheat and a second suction superheat: the first suction superheat = the temperature detected by the first temperature sensor - the saturation temperature corresponding to the suction pressure sensor; the second suction superheat = the temperature detected by the second temperature sensor - the saturation temperature corresponding to the suction pressure sensor.

[0007] A control method for a device to prevent liquid return in a compression condensing unit, comprising:

[0008] Collect the suction pressure and suction temperature of the suction pipe, and control the first suction superheat degree and the second suction superheat degree of the suction pipe according to the collected suction pressure and suction temperature;

[0009] When the first suction superheat degree is higher than the set superheat degree, the electric heating device stops working, the cut-off solenoid valve opens, and the electronic expansion valve closes;

[0010] When the first suction superheat degree is less than the set superheat degree, the cut-off solenoid valve on the suction pipe closes, the electronic expansion valve opens to the minimum opening degree, and at the same time the electric heating device starts to heat the refrigerant flowing through the suction pipe; when the second suction superheat degree is greater than the set superheat degree, the opening degree of the electronic expansion valve gradually increases according to the set time interval and amplitude;

[0011] When the first suction superheat degree is less than the set superheat degree and the second suction superheat degree is greater than the set superheat degree, increase the opening degree of the electronic expansion valve and continue to continuously detect the second suction superheat degree; during the detection, if the second suction superheat degree continuously remains greater than the set superheat degree, continue to increase the opening degree of the electronic expansion valve until the electronic expansion valve is fully opened; if the second suction superheat degree continuously remains less than the set superheat degree during the continuous detection, the electronic expansion valve gradually reduces the opening degree until it is reduced to the minimum opening degree; if at the minimum opening degree, the second suction superheat degree still continuously remains lower than the set superheat degree, the electronic expansion valve will ensure that the liquid refrigerant in the suction pipe is fully vaporized by the way of closing completely at intervals and then opening to the minimum opening degree at intervals, while avoiding too low pressure in the suction pipe resulting in low-pressure protection of the compressor.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The device for preventing liquid return in a compression condensing unit provided by the present invention can effectively avoid liquid return during the operation of the compressor, avoid damage to the compressor caused by liquid return, and has the advantages of simple structure, convenient installation and control, low cost, small modification to the existing refrigeration system, high operability, good prevention effect on liquid hammer, and convenient use in engineering practice. Description of the Drawings

[0014] Figure 1 is the structural schematic diagram of the present invention. Detailed Embodiments

[0015] The present invention will be further described below in conjunction with the accompanying drawings.

[0016] Embodiment 1

[0017] AsFigure 1 As shown in the figure, a device for preventing liquid return in a compression condensing unit includes a controller 6, and a suction pressure sensor 2, a suction temperature sensor, a cut-off solenoid valve 4, an electronic expansion valve 5, and an electric heating device 7, all of which are connected to the controller 6.

[0018] The suction pressure sensor 2 is installed on the suction pipe 15 connected to the suction port of the compressor 14 for detecting the suction pressure; the suction temperature sensor is installed on the suction pipe 15 for detecting the suction temperature; the cut-off solenoid valve 4 is installed on the suction pipe 15 and is located between the compressor 14 and the evaporator 13; the electronic expansion valve 5 is installed on the suction pipe 15 and is in parallel with the cut-off solenoid valve 4; the electric heating device 7 is installed on the suction pipe 15 and is located between the electronic expansion valve 5 and the compressor 14.

[0019] Among them, the suction temperature sensor includes a first temperature sensor 31 and a second temperature sensor 32, both of which are installed on the suction pipe 15. The first temperature sensor 31 is located between the cut-off solenoid valve 4 and the evaporator 13; the second temperature sensor 32 is located between the electric heating device 7 and the compressor 14. The first temperature sensor 31 and the second temperature sensor 32 are both connected to the controller 6. The first temperature sensor 31 is used to calculate the first superheat degree, and the first superheat degree = the temperature detected by the first temperature sensor 31 - the saturation temperature corresponding to the pressure sensor 2. This superheat degree is used to control the start and stop of the liquid return prevention device. The second temperature sensor 32 is used to calculate the second superheat degree, and the second superheat degree = the temperature detected by the second temperature sensor 32 - the saturation temperature corresponding to the pressure sensor 2. This superheat degree is used to control the opening degree of the electronic expansion valve 5. When the second superheat degree is greater than the set value, the opening degree of the electronic expansion valve is gradually increased at a set time interval and an increasing amplitude.

[0020] The controller 6 is an existing controller of the refrigeration system.

[0021] The condenser 11, the expansion valve 12, the evaporator 13, and the compressor 14 are sequentially connected to form a refrigeration system.

[0022] The electric heating device 7 can be an electric heating wire or an electric heating film, etc., and is used to heat the suction pipe 15.

[0023] Embodiment 2

[0024] On the basis of the above Embodiment 1, as Figure 1 shown in the figure, a control method for a device for preventing liquid return in a compression condensing unit includes:

[0025] Collect the suction pressure and suction temperature of the suction pipe 15, and control the first suction superheat degree and the second suction superheat degree of the suction pipe 15 according to the collected suction pressure and suction temperature;

[0026] When the first suction superheat is higher than the set superheat, the electric heating device 7 stops working, the cut-off solenoid valve 4 opens, and the electronic expansion valve 5 closes;

[0027] When the first suction superheat is less than the set superheat, the stop solenoid valve 4 on the suction pipe 15 is closed, the electronic expansion valve 5 is opened to the minimum opening, and the electric heating device 7 starts to heat the refrigerant flowing in the suction pipe 15; when the second suction superheat is greater than the set superheat, the opening of the electronic expansion valve 5 is gradually increased according to the set delay interval and amplitude;

[0028] When the first suction superheat is less than the set superheat, and the second suction superheat is greater than the set superheat, the opening of the electronic expansion valve 5 is increased, and the second suction superheat is continuously detected; if the second suction superheat is continuously greater than the set superheat during the detection period, the opening of the electronic expansion valve 5 is continuously increased until the electronic expansion valve 5 is fully opened; if the second suction superheat is continuously less than the set superheat during the continuous detection period, the electronic expansion valve 5 gradually reduces the opening until it is reduced to the minimum opening; if at the minimum opening, the second suction superheat is still continuously lower than the set superheat, the electronic expansion valve 5 will ensure that the liquid refrigerant in the suction pipe is fully vaporized by closing it at intervals and then opening it at intervals to the minimum opening, while avoiding the pressure in the suction pipe being too low to cause low-pressure protection of the compressor.

[0029] After fully closing, the electronic expansion valve is opened to the minimum opening. The closing time is usually within 5 seconds.

[0030] The superheat is usually 3-7K. Depending on the application environment and system configuration of the refrigeration system, the on-site setting value of the superheat will be adjusted accordingly within this range.

[0031] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the protection scope of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without paying creative labor, and these methods will fall within the protection scope of the claims of the present invention.

Claims

1. A device for preventing liquid return in a compression condensing unit, characterized in that, Comprising: An intake pressure sensor (2), which is installed on the suction pipe (15) connected to the intake port of the compressor (14) and is used to detect the intake pressure; An intake temperature sensor, which is installed on the suction pipe (15) and is used to detect the intake temperature; A cut-off solenoid valve (4), which is installed on the suction pipe (15) and is located between the compressor (14) and the evaporator (13); An electronic expansion valve (5), which is installed on the suction pipe (15) and is connected in parallel with the cut-off solenoid valve (4); An electric heating device (7), which is installed on the suction pipe (15) and is located between the electronic expansion valve (5) and the compressor (14); and A controller (6), which is respectively connected to the intake pressure sensor (2), the intake temperature sensor, the cut-off solenoid valve (4), the electronic expansion valve (5) and the electric heating device (7), and is used to control the suction superheat degree of the suction pipe (15) according to the intake temperature and the intake pressure; The intake temperature sensor includes: A first temperature sensor (31), which is located between the cut-off solenoid valve (4) and the evaporator (13); and A second temperature sensor (32), which is located between the electric heating device (7) and the compressor (14); The suction superheat degree includes a first suction superheat degree and a second suction superheat degree: The first suction superheat degree = the temperature detected by the first temperature sensor (31) - the saturation temperature corresponding to the intake pressure sensor (2); The second suction superheat degree = the temperature detected by the second temperature sensor (32) - the saturation temperature corresponding to the intake pressure sensor (2); The controller (6) is executed according to the control method of the device for preventing liquid return of the compression condensation unit. The control method of the device for preventing liquid return of the compression condensation unit includes: Collecting the intake pressure and the intake temperature of the suction pipe (15), and controlling the first suction superheat degree and the second suction superheat degree of the suction pipe (15) according to the collected intake pressure and intake temperature; When the first suction superheat degree is higher than the set superheat degree, the electric heating device (7) stops working, the cut-off solenoid valve (4) opens, and the electronic expansion valve (5) closes; When the first suction superheat degree is less than the set superheat degree, the cut-off solenoid valve (4) on the suction pipe (15) closes, the electronic expansion valve (5) opens to the minimum opening degree, and at the same time the electric heating device (7) starts to heat the refrigerant flowing through the suction pipe (15); when the second suction superheat degree is greater than the set superheat degree, the opening degree of the electronic expansion valve (5) gradually increases according to the set time interval and amplitude; When the first suction superheat is less than the set superheat and the second suction superheat is greater than the set superheat, increase the opening degree of the electronic expansion valve (5), and continue to continuously detect the second suction superheat; during the detection, if the second suction superheat continuously remains greater than the set superheat, continue to increase the opening degree of the electronic expansion valve (5) until the electronic expansion valve (5) is fully opened; if the second suction superheat continuously remains less than the set superheat during the continuous detection, the electronic expansion valve (5) gradually reduces the opening degree until it is reduced to the minimum opening degree; if, at the minimum opening degree, the second suction superheat still continuously remains lower than the set superheat, the electronic expansion valve (5) will ensure that the liquid refrigerant in the suction pipe is fully vaporized by closing completely at intervals and then opening to the minimum opening degree at intervals, while avoiding excessively low pressure in the suction pipe that may cause low-pressure protection of the compressor.

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