阅读说明：本技术 一种兆瓦级离心低温空气源热泵系统气液分离控制方法 (Gas-liquid separation control method for megawatt centrifugal low-temperature air source heat pump system ) 是由 陈盼盼 李一静 任翠蕾 于 2020-05-29 设计创作，主要内容包括：本发明公开了一种兆瓦级离心低温空气源热泵系统气液分离控制方法,属于制冷行业技术领域。首先对气液分离器进行改进,入口连接蒸发器,出口连接压缩机。低温时,蒸发器排出气态的制冷剂从气液分离器的入口进入,产生气液两相流,液态制冷剂沉积在气液分离器的底部,气态制冷剂从出口进入压缩机。然后液位计实时监测液态制冷剂液位高度,当高度达到阈值时,启动所有电加热,液态制冷剂维持继续升高,直至液体制冷剂达到控制液位。最后当压缩机入口的气态制冷剂过热度达到设定标准时,停止少数电加热,保持过热度满足标准。否则,保持全部电加热的持续开启,保证压缩机避免带液运转。本发明应用更加简单,减小大面积推广的难度。(The invention discloses a gas-liquid separation control method for a megawatt centrifugal low-temperature air source heat pump system, and belongs to the technical field of refrigeration industry. Firstly, the gas-liquid separator is improved, the inlet is connected with the evaporator, and the outlet is connected with the compressor. At low temperature, gaseous refrigerant discharged by the evaporator enters from the inlet of the gas-liquid separator to generate gas-liquid two-phase flow, liquid refrigerant is deposited at the bottom of the gas-liquid separator, and gaseous refrigerant enters the compressor from the outlet. And then the liquid level meter monitors the liquid level height of the liquid refrigerant in real time, when the height reaches a threshold value, all electric heating is started, and the liquid refrigerant keeps continuously rising until the liquid refrigerant reaches a control liquid level. And finally, stopping a few electric heating when the superheat degree of the gas refrigerant at the inlet of the compressor reaches a set standard, and keeping the superheat degree to meet the standard. Otherwise, the continuous opening of all the electric heating is kept, and the compressor is ensured to avoid liquid-carrying operation. The invention is simpler to apply and reduces the difficulty of large-area popularization.)

1. A gas-liquid separation control method for a megawatt centrifugal low-temperature air source heat pump system is characterized by comprising the following specific steps:

step one, improving a gas-liquid separator, wherein an inlet is connected with an evaporator, and an outlet is connected with a compressor;

the improved gas-liquid separator is as follows:

a refrigeration shielding pump is arranged on the outer side of the gas distribution cylinder body and is divided into two pipelines, namely an inlet pipeline and an outlet pipeline, wherein the inlet of the inlet pipeline penetrates through the inside of the gas distribution cylinder body and extends to the bottommost part of the gas distribution cylinder body through an elbow; the outlet of the outlet pipeline is connected with an independent liquid storage device;

welding a separation screen at the upper end inside the gas separation cylinder, and keeping the horizontal inclination angle of the separation screen between 3 and 5 degrees; at the bottom end of the gas distribution cylinder, two blind pipes penetrate through and extend into the gas distribution cylinder; two ends of each blind pipe are respectively provided with an electric heater, and the temperature of the bottom of the gas distribution cylinder is kept to be increased through the electric heaters;

step two, when the temperature is low, gaseous refrigerant discharged from the outlet of the evaporator enters from the inlet of the gas-liquid separator to generate gas-liquid two-phase flow;

thirdly, because the superheat degree of the refrigerant is small or no superheat degree exists, the liquid refrigerant is deposited at the bottom of the gas-liquid separator, and the gaseous refrigerant enters the inlet of the compressor from the outlet of the gas-liquid separator;

step four, accumulating the liquid refrigerant at the bottom of the gas-liquid separator, monitoring the liquid level height in real time by a liquid level meter arranged on the gas-liquid separator, transmitting a signal to an upper computer by the liquid level meter when the height reaches a threshold value, and starting all electric heating;

step five, at the initial stage of starting the electric heating, the liquid refrigerant at the bottom of the gas-liquid separator keeps rising continuously, and when the electric heating reaches a completely normal state, whether the liquid refrigerant at the bottom of the gas-liquid separator reaches a control liquid level is judged, if so, the step six is carried out, otherwise, the liquid level meter continuously monitors the height of the liquid refrigerant in real time until the liquid refrigerant reaches the control liquid level, and the step six is carried out;

the electric heating is used for evaporating the liquid refrigerant at the bottom of the gas-liquid separator into a gaseous refrigerant, and inputting the gaseous refrigerant into the inlet of the compressor;

step six, the liquid level meter transmits a signal of controlling the liquid level to an upper computer, the upper computer starts a refrigeration shielding pump, and simultaneously opens an electric regulating valve of an outlet pipeline of the shielding pump, so that the liquid refrigerant is transferred into the liquid storage device, the liquid level at the bottom of the gas-liquid separator displays 0, and the shielding pump and the regulating valve stop simultaneously;

step seven, judging whether the superheat degree of the gaseous refrigerant at the inlet of the compressor reaches a set standard, if so, stopping a few electric heating, and keeping the superheat degree of the gaseous refrigerant at the inlet of the compressor to meet the standard; otherwise, the continuous opening of all the electric heating is kept, and the compressor is ensured to avoid liquid-carrying operation.

2. The method as claimed in claim 1, wherein the threshold value in step four is artificially set to 1/3 height of the cylinder radius of the gas-liquid separator.

3. The gas-liquid separation control method of the megawatt-level centrifugal low-temperature air source heat pump system as claimed in claim 1, wherein the seventh step specifically comprises:

when the electric heating is completely started, the height of the liquid refrigerant accumulated at the bottom of the gas-liquid separator still reaches the control liquid level, the upper computer continuously starts the refrigeration shielding pump to transfer the liquid refrigerant to the inside of the liquid reservoir, and the suction state of the inlet of the compressor is indirectly controlled by controlling the starting and stopping of the refrigeration shielding pump and the electric regulating valve and the number and duration of the electric heating starting, so that the compressor is prevented from running with liquid.

Technical Field

The invention belongs to the technical field of refrigeration industry, and particularly relates to a gas-liquid separation control method for a megawatt centrifugal low-temperature air source heat pump system.

Background

The general principle of the vapor-liquid separator in the industry is that saturated gas enters the separator to lose weight instantly and separate the saturated gas from the gas by utilizing different specific gravities of the gas and the liquid, and the flow velocity of the outlet gas is utilized to form vortex to deposit the liquid with large specific gravity to the lower part of the separator, and the separated gas flows out from the upper part of the separator.

For a megawatt low-temperature centrifugal air source heat pump, when the ambient temperature is very low, the heat exchange of an evaporator is influenced, the superheat degree of a refrigerant is very low, the specific gravity of a liquid phase is increased, and the liquid-carrying operation of a compressor is easy to generate. The existing commonly used gas-liquid separator has poor effect when processing large-flow two-phase flow separation and needs to be further optimized.

Disclosure of Invention

The invention provides a gas-liquid separation control method of a megawatt centrifugal low-temperature air source heat pump system, aiming at the problems, well solving the problem of gas-liquid two-phase separation of a refrigerant when the ambient temperature of the megawatt centrifugal low-temperature air source heat pump is too low, protecting a compressor from damage caused by liquid impact and improving the stability of system operation.

The gas-liquid separation control method of the megawatt-level centrifugal low-temperature air source heat pump system comprises the following specific steps:

step one, improving a gas-liquid separator, wherein an inlet is connected with an evaporator, and an outlet is connected with a compressor;

the improved gas-liquid separator is as follows:

a refrigeration shielding pump is arranged on the outer side of the gas distribution cylinder body and is divided into two pipelines, namely an inlet pipeline and an outlet pipeline, wherein the inlet of the inlet pipeline penetrates through the inside of the gas distribution cylinder body and extends to the bottommost part of the gas distribution cylinder body through an elbow; the outlet of the outlet pipeline is connected with an independent liquid storage device;

welding a separation screen at the upper end inside the gas separation cylinder, and keeping the horizontal inclination angle of the separation screen between 3 and 5 degrees; at the bottom end of the gas distribution cylinder, two blind pipes penetrate through and extend into the gas distribution cylinder; two ends of each blind pipe are respectively provided with an electric heater, and the temperature of the bottom of the gas distribution cylinder is kept to be increased through the electric heaters;

step two, when the temperature is low, gaseous refrigerant discharged from the outlet of the evaporator enters from the inlet of the gas-liquid separator to generate gas-liquid two-phase flow;

thirdly, because the superheat degree of the refrigerant is small or no superheat degree exists, the liquid refrigerant is deposited at the bottom of the gas-liquid separator, and the gaseous refrigerant enters the inlet of the compressor from the outlet of the gas-liquid separator;

step four, accumulating the liquid refrigerant at the bottom of the gas-liquid separator, monitoring the liquid level height in real time by a liquid level meter arranged on the gas-liquid separator, transmitting a signal to an upper computer by the liquid level meter when the height reaches a threshold value, and starting all electric heating;

the threshold value is artificially set as 1/3 height value of the radius of the cylinder body of the gas-liquid separator;

step five, at the initial stage of starting the electric heating, the liquid refrigerant at the bottom of the gas-liquid separator keeps rising continuously, and when the electric heating reaches a completely normal state, whether the liquid refrigerant at the bottom of the gas-liquid separator reaches a control liquid level is judged, if so, the step six is carried out, otherwise, the liquid level meter continuously monitors the height of the liquid refrigerant in real time until the liquid refrigerant reaches the control liquid level, and the step six is carried out;

the control liquid level is set according to the test result of the actual field;

the electric heating is used for evaporating the liquid refrigerant at the bottom of the gas-liquid separator into a gaseous refrigerant, and inputting the gaseous refrigerant into the inlet of the compressor;

and step six, the liquid level meter transmits a signal of controlling the liquid level to an upper computer, the upper computer starts the refrigeration shielding pump, and simultaneously opens an electric regulating valve of an outlet pipeline of the shielding pump, so that the liquid refrigerant is transferred into the liquid storage device, the liquid level at the bottom of the gas-liquid separator displays 0, and the shielding pump and the regulating valve stop simultaneously.

Step seven, judging whether the superheat degree of the gaseous refrigerant at the inlet of the compressor reaches a set standard, if so, stopping a few electric heating, and keeping the superheat degree of the gaseous refrigerant at the inlet of the compressor to meet the standard; otherwise, the continuous opening of all the electric heating is kept, and the compressor is ensured to avoid liquid-carrying operation.

When the electric heating is completely started, the height of the liquid refrigerant accumulated at the bottom of the gas-liquid separator still reaches the control liquid level, the upper computer continuously starts the refrigeration shielding pump to transfer the liquid refrigerant to the inside of the liquid reservoir, and the suction state of the inlet of the compressor is indirectly controlled by controlling the starting and stopping of the refrigeration shielding pump and the electric regulating valve and the number and duration of the electric heating starting, so that the compressor is prevented from running with liquid.

The invention has the advantages that:

due to technical limitation, the megawatt low-temperature centrifugal air source is rarely applied to engineering, and the stability and good economy of the continuous operation of the whole system are determined by the quality of the gas-liquid separation effect under the low-temperature working condition. The application of the gas-liquid separator can reduce the possibility of air suction and liquid entrainment of the compressor under the low-temperature working condition, so that the application of the centrifugal low-temperature air source heat pump unit is simpler, and the difficulty of large-area popularization is reduced.

Drawings

FIG. 1 is a flow chart of a gas-liquid separation control method of a megawatt centrifugal low-temperature air source heat pump system according to the invention;

FIG. 2 is a front elevational view of an improved gas-liquid separator employed in the present invention;

FIG. 3 is a sectional view of the interior of an improved gas-liquid separator employed in the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

The invention provides a gas-liquid separation control method of a megawatt centrifugal low-temperature air source heat pump system, which improves a conventional gas-liquid separator: increase electrical heating and improve electrical heating's locating position, adjust separation silk screen installation angle, canned motor pump entry elbow design etc. in inside, combine the remote analog signal of level gauge, the monitoring gas divides the liquid level, control refrigeration canned motor pump and electric control valve open and stop to and the number of times and the duration that electrical heating starts, thereby the state of breathing in of indirect control compressor entry makes the compressor avoid taking liquid operation, reaches the effect of automatic continuous operation.

The gas-liquid separation control method of the megawatt-level centrifugal low-temperature air source heat pump system comprises the following specific steps as shown in figure 1:

step one, improving a gas-liquid separator, wherein an inlet is connected with an evaporator, and an outlet is connected with a compressor;

the improved gas-liquid separator is as follows:

the refrigeration shielding pump is arranged on the outer side of the gas distribution cylinder and is divided into two pipelines, namely an inlet pipeline and an outlet pipeline, wherein an inlet of the inlet pipeline penetrates through the inside of the gas distribution cylinder and extends to the bottommost part of the gas distribution cylinder through an elbow, so that the liquid level in the cylinder can be reduced to the lowest level when the shielding pump is started; the outlet of the outlet pipeline is connected with an independent liquid storage device; the outlet pipeline of the refrigeration shielding pump is also provided with a shielding pump loop which is connected above the gas distribution inlet and extends into the gas distribution inlet; the design of the canned motor pump loop ensures the cooling of the motor of the loop, reduces the possibility of damaging the canned motor pump, and ensures that the canned motor pump can be started at any time.

Welding a separation screen at the upper end inside the gas separation cylinder, and keeping the horizontal inclination angle of the separation screen between 3 and 5 degrees; the inclined arrangement can increase the safe liquid level, and when the gas separation liquid level is very high, the separation silk screen still has good separation effect; at the bottom end of the gas distribution cylinder, two blind pipes penetrate through and extend into the gas distribution cylinder; two ends of each blind pipe are respectively provided with an electric heater, the temperature of the bottom of the gas distribution cylinder is kept to be increased through the electric heaters, and the electric heaters are arranged at the lowest part of the cylinder, so that liquid refrigerants can be better heated when the liquid level is low;

meanwhile, four liquid sight glasses are arranged outside the gas separation cylinder body, so that convenience in on-site observation in the operation process is ensured. A manhole is arranged on the gas separation cylinder body, so that the convenience of system filth blockage and subsequent maintenance is ensured.

Step two, when the temperature is low, gaseous refrigerant discharged from the outlet of the evaporator enters from the inlet of the gas-liquid separator to generate gas-liquid two-phase flow;

thirdly, because the superheat degree of the refrigerant is small or no superheat degree exists, the liquid refrigerant is deposited at the bottom of the gas-liquid separator, and the gaseous refrigerant enters the inlet of the compressor from the outlet of the gas-liquid separator;

step four, accumulating the liquid refrigerant at the bottom of the gas-liquid separator, monitoring the liquid level height in real time by a liquid level meter arranged on the gas-liquid separator, transmitting a signal to an upper computer by the liquid level meter when the height reaches a threshold value, and starting all electric heating;

the threshold value is artificially set as 1/3 height value of the radius of the cylinder body of the gas-liquid separator;

step five, at the initial stage of starting the electric heating, the liquid refrigerant at the bottom of the gas-liquid separator keeps rising continuously, and when the electric heating reaches a completely normal state, whether the liquid refrigerant at the bottom of the gas-liquid separator reaches a control liquid level is judged, if so, the step six is carried out, otherwise, the liquid level meter continuously monitors the height of the liquid refrigerant in real time until the liquid refrigerant reaches the control liquid level, and the step six is carried out;

the control liquid level is set according to the test result of the actual field, and the control liquid level is set to be 1/2 of the radius of the cylinder body of the gas-liquid separator in the embodiment;

the electric heating is used for evaporating the liquid refrigerant at the bottom of the gas-liquid separator into a gaseous refrigerant, and inputting the gaseous refrigerant into the inlet of the compressor;

and step six, the liquid level meter transmits a signal of controlling the liquid level to an upper computer, the upper computer starts the refrigeration shielding pump, and simultaneously opens an electric regulating valve of an outlet pipeline of the shielding pump, so that the liquid refrigerant is transferred into the liquid storage device, the liquid level at the bottom of the gas-liquid separator displays 0, and the shielding pump and the regulating valve stop simultaneously.

The electric regulating valve can regulate the liquid flow according to the requirement;

step seven, judging whether the superheat degree of the gaseous refrigerant at the inlet of the compressor reaches a set standard, if so, stopping a few electric heating, and keeping the superheat degree of the gaseous refrigerant at the inlet of the compressor to meet the standard; otherwise, keeping the continuous opening of all the electric heaters; the compressor is ensured to avoid liquid-carrying operation.

The superheat degree standard is set on site according to the actual situation;

the suction state of the inlet of the compressor is indirectly controlled by controlling the starting and stopping of the refrigeration shielding pump and the electric regulating valve and the number and duration of the electric heating starting, so that the compressor is prevented from running with liquid and the automatic continuous running effect is achieved.