CN110887282A

CN110887282A - Method for preventing liquid from being carried in heat exchanger and air conditioner

Info

Publication number: CN110887282A
Application number: CN201911206469.XA
Authority: CN
Inventors: 王传华; 孙思; 温祖恒; 罗昭铭
Original assignee: Gree Electric Appliances Inc of Zhuhai
Current assignee: Gree Electric Appliances Inc of Zhuhai
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2020-03-17

Abstract

The invention discloses a method for preventing a heat exchanger from carrying liquid and an air conditioner, comprising the following steps: when the system meets the defrosting condition, the compressor is stopped; and judging whether the pressure difference value between the evaporator and the condenser is smaller than a preset value, and if so, starting the compressor. The invention can avoid the sudden change of the pressure in the shell and tube by judging the pressure difference to start and stop the compressor, thereby preventing the flash of the refrigerant, protecting the compressor from damage caused by liquid impact, meanwhile, arranging a filter screen in the shell and tube, avoiding the trouble of setting double air distributors, saving the cost, achieving the aim of solving the problem of liquid carrying when the flooded shell and tube heats and defrosts in a double-pipe manner on the control and the system, simplifying the system and reducing the cost.

Description

Method for preventing liquid from being carried in heat exchanger and air conditioner

Technical Field

The invention relates to the field of air conditioners, in particular to a method for preventing a heat exchanger from carrying liquid and an air conditioner.

Background

When the unit heats, the shell tube is a condenser, and a part of refrigerant liquid is accumulated on the shell side. When heating operation is switched to defrosting, the pressure of the shell tube is changed from high pressure to low pressure, liquid in the shell side is flashed due to sudden change of the pressure, and a flashed gas-liquid mixture enters the compressor to cause liquid impact. The liquid impact generates great impulsive force on the scroll disk, the scroll disk can be broken, the lubricating oil containing a large amount of liquid can reduce the viscosity of the refrigerant, an enough oil film cannot be formed on the friction surface, and the rapid abrasion of moving parts in the compressor is caused.

At present, a commonly used method for avoiding frost formation and liquid entrainment of a flooded shell-and-tube evaporator is to arrange double gas branches, which can effectively avoid liquid impact of a compressor, but increases the complexity of the system and simultaneously increases the cost.

Disclosure of Invention

The invention provides a method for preventing a heat exchanger from carrying liquid and an air conditioner, aiming at solving the technical problem that the mode for avoiding liquid impact of a compressor is complex in the prior art.

The technical scheme adopted by the invention is as follows:

the invention provides a method for preventing a heat exchanger from carrying liquid, which comprises the following steps:

when the system meets the defrosting condition, the compressor is stopped;

and judging whether the pressure difference value between the evaporator and the condenser is smaller than a preset value, and if so, starting the compressor.

Preferably, after the compressor is stopped, the step number of the electronic expansion valve is increased and then the difference value is judged.

The specific steps for increasing the electronic expansion valve are as follows: and increasing the step number of the electronic expansion valve to the maximum value.

The invention also comprises the following steps: and judging whether the exhaust pressure is greater than a second preset value, if so, switching off the electromagnetic valve of the four-way valve, and entering a defrosting mode.

Preferably, the evaporator is a flooded shell and tube.

Preferably, the condenser is a finned heat exchanger.

The invention also provides an air conditioner, which prevents the liquid from being carried by the heat exchanger by using the method for preventing the liquid from being carried by the heat exchanger, and the method specifically comprises the following steps: the system comprises a controller, an evaporator, a condenser, a compressor, an electronic expansion valve and a four-way valve.

Furthermore, a filter screen for intercepting liquid particles is arranged at the position of the evaporator close to the gaseous refrigerant outlet.

Preferably, the air conditioner is an air-cooled chiller.

Compared with the prior art, the invention can avoid sudden change of the pressure in the shell and tube by judging the mode of starting and stopping the compressor by the pressure difference to prevent the refrigerant from flashing, thereby protecting the compressor from damage caused by liquid impact, meanwhile, the filter screen is arranged in the shell and tube, the trouble of setting double air distributors can be avoided, the cost is saved, the problem of liquid carrying when the flooded shell and tube heats and defrosts is solved in control and on the system under double control, the system is simplified, and the cost is reduced.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

FIG. 1 is a flow chart of the present invention;

FIG. 2 is a schematic structural view of a shell and tube in an embodiment of the invention;

fig. 3 is a schematic sectional view taken along line a-a of fig. 2.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The principles and construction of the present invention will be described in detail below with reference to the drawings and examples.

As shown in fig. 1, the present invention provides a method for preventing liquid-carrying in a heat exchanger, comprising the steps of: when the system meets the defrosting condition, the compressor is controlled to stop; and judging whether the pressure difference (absolute value) between the evaporator and the condenser is smaller than a preset value, if so, indicating that the pressure of the system tends to be balanced, starting the compressor, and if not, stopping the compressor. The sudden change of the pressure in the shell tube can be avoided by judging the pressure difference, so that the flash vaporization of the refrigerant is prevented, and the damage of liquid impact on the compressor is avoided.

The compressor is controlled to stop in a way that the unit is shut down according to a normal shutdown process, after the compressor is shut down, the step number of the electronic expansion valve is increased, then the pressure difference value between the evaporator and the condenser is judged, the balance of the system pressure can be accelerated, the shutdown time of the compressor is reduced, and in a specific embodiment, the step number of the electronic expansion valve can be directly increased to the maximum value.

After the compressor is started, the invention also comprises the following steps: and judging whether the exhaust pressure (P row) of the compressor is greater than a second preset value, if so, indicating that the four-way valve has enough pressure to carry out reversing, controlling the electromagnetic valve of the four-way valve to be powered off, automatically reversing the pressure of the four-way valve to enter a defrosting mode, and if not, keeping the electromagnetic valve of the four-way valve in an open state to ensure that the four-way valve cannot be reversed.

In a specific embodiment, in a state that the four-way valve is switched to the rear direction, the evaporator (i.e., the indoor heat exchanger) is a flooded shell and tube, and the condenser (i.e., the outdoor heat exchanger requiring defrosting) is a finned heat exchanger.

The invention also provides an air conditioner, in particular to an air-cooled water chilling unit or an air-cooled hot water unit, which prevents the liquid from being carried by the heat exchanger by using the method for preventing the liquid from being carried by the heat exchanger, and the air conditioner specifically comprises the following steps: the controller, the evaporator, the condenser, the compressor, the electronic expansion valve and the four-way valve are arranged, and the evaporator, the condenser and the compressor are respectively provided with a pressure sensor for detecting corresponding pressure.

As shown in fig. 2 and 3, a filter screen 2 is arranged at a refrigerant outlet 11 of a flooded shell and tube 1 (i.e. an evaporator) close to the upper part, the filter screen 2 utilizes the difference of the sizes of liquid and gas particles, when the liquid refrigerant boils, the liquid refrigerant is filtered down when the gas-liquid mixture passes through the filter screen and flows back to the shell and tube under the action of gravity, and the gas refrigerant passes through the filter screen and comes out from the upper part of the evaporator.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A method of preventing liquid carry-over in a heat exchanger, comprising the steps of:

when the system meets the defrosting condition, the compressor is stopped;

2. The method of preventing liquid carry over in a heat exchanger of claim 1, wherein after shutdown of the compressor, the number of steps of the electronic expansion valve is increased and the difference is determined.

3. The method for preventing liquid carrying in a heat exchanger according to claim 2, wherein the step number of the electronic expansion valve is increased by: and increasing the step number of the electronic expansion valve to the maximum value.

4. The method of preventing liquid carry-over in a heat exchanger of claim 1, further comprising the steps of: and judging whether the exhaust pressure is greater than a second preset value, if so, switching off the electromagnetic valve of the four-way valve, and entering a defrosting mode.

5. An air conditioner, characterized in that the method for preventing the liquid carrying of the heat exchanger according to any one of claims 1 to 4 is used to prevent the liquid carrying of the heat exchanger.

6. The air conditioner according to claim 5, comprising: the system comprises a controller, an evaporator, a condenser, a compressor, an electronic expansion valve and a four-way valve.

7. The air conditioner according to claim 6, wherein the evaporator is provided with a filter screen intercepting liquid particles at a position near the refrigerant outlet.

8. The air conditioner of claim 6, wherein the evaporator is a flooded shell and tube.

9. The air conditioner of claim 6, wherein the condenser is a finned heat exchanger.

10. The air conditioner according to claim 5, wherein the air conditioner is an air-cooled chiller.