The working principle of the thermodynamic expansion valve, the working principle and function of th

Principle Control of Thermostatic Expansion Valve and Electronic Expansion Valve1 Overview Energy saving and environmental protection are two major problems that need to be solved urgently. The World Summit on Sustainable Development was held in Johannesburg, South Africa, from 26 August to 4 September 2002. At the conference, the International Institute of Refrigeration published the "Refrigeration Industry's Commitment to Sustainable Development and Mitigation of Atmospheric Change", in which it was stated that the main challenge for the refrigeration industry comes from global warming.

Carbon dioxide emissions account for 80% of the refrigeration industry's impact on global warming. These indirect emissions are partly caused by the production of energy required for the operation of the refrigeration plant. Refrigeration, air conditioning and heat pumps consume about 15% of the electricity produced worldwide, indicating that the impact of indirect emissions is severe.

The document also proposes that in the next 20 years, the refrigeration industry must set an ambition to achieve one of the goals: a 30-50% reduction in energy consumption per refrigeration plant. In order to protect the environment, refrigeration companies should integrate energy conservation into the life cycle of refrigeration equipment.

As one of the four major components of the refrigeration cycle, the throttling device plays a very key role in the system, and it is an important part of the whole refrigeration equipment to reduce energy consumption by selecting and applying the appropriate throttling mechanism to match the refrigeration system. In this paper, the working principle and operating energy matching of the throttling mechanism will be analyzed, focusing on the working principle of the electronic expansion valve. 2 The working principle and matching of the traditional throttling mechanism The working principle of throttling is that when the refrigerant working fluid flows through the valve, the flow section suddenly shrinks, the fluid flow rate accelerates, the pressure drops, and the size of the pressure drop depends on the proportion of the flow section shrinkage.

The role of the throttling mechanism: 1) Throttling and depressurizing. When the refrigerant-saturated liquid at room temperature and high pressure flows through the throttle valve, it becomes a refrigerant liquid at low temperature and low pressure and produces a small flash gas.

And then to achieve the purpose of absorbing heat to the outside world.

2) Adjust the flow rate: The throttle valve controls the opening of the valve by feeling the change of the superheat of the refrigerant at the outlet of the evaporator through the temperature sensing bag, and regulates the flow rate of the refrigerant entering the evaporator to match the flow rate with the heat load of the evaporator. When the heat load of the evaporator increases, the valve opening also increases, and the refrigerant flow increases, and vice versa, the refrigerant flow decreases.

3) Control superheat: The throttling mechanism has the function of controlling the superheat of the refrigerant at the outlet of the evaporator, which not only keeps the heat transfer area of the evaporator fully utilized, but also prevents the suction liquid from damaging the compressor.

The working principle is to use the change of sensing temperature to change the opening degree of the valve hole, so as to change the flow rate of the refrigerant to achieve automatic adjustment. If the refrigerant is not a problem, it is a problem with the thermostatic expansion valve.

Expansion valve working principle:

The pressure value is automatically adjusted by the temperature difference, and then the system is brought to equilibrium.

Usually, there is a temperature difference between the temperature-sensitive line at the outlet and the evaporation temperature, which is called superheat.

The temperature sensor bag feels the evaporator.

After the outlet temperature, the entire sensing system is at the corresponding saturation pressure.

When the air conditioning system.

When the set temperature is equal to the temperature sensed by the thermosensor, the pressure up and down the expansion valve is equal, and the system is in equilibrium.

When the outlet temperature is too high, that is, the sensing temperature of the induction package is too high, and the pressure value above will become larger. The pressure plate of the expansion valve pushes the spool downward, making the expansion valve more open.

The spool enters the evaporator and becomes a gaseous state, so that the temperature in the evaporator drops, so that the air conditioning system reaches equilibrium again.

On the contrary, when the temperature is too low, the opening degree of the expansion valve will become smaller, which will cause the freon entering the evaporator to drop, so that the temperature in the evaporator will increase.

The role of the expansion valve:

1. Throttling and depressurizing.

Expansion valves are capable of making liquid refrigerants at high temperatures and pressures.

After throttling through its throttle hole, it becomes a low-temperature and low-pressure mist hydraulic refrigerant, which reduces the pressure and provides effective conditions for the evaporation of the refrigerant.

2. Adjust the flow rate.

The expansion valve is an important component of the refrigeration system, which can regulate the flow of refrigerant and ensure that the outlet of the evaporator is completely gaseous refrigerant. If the flow rate of the refrigerant is too small, it will lead to early evaporation, resulting in poor refrigeration effect; If the flow rate of the refrigerant is too large, the outlet contains liquid refrigerant, which will cause problems in the work of the pressure and shrinkage machine.

Thermostatic expansion valves.

Installed in the evaporator.

The inlet, often referred to as the expansion valve, serves two main purposes:

1. Throttling: liquid refrigerant with high temperature and high pressure.

After throttling through the throttle hole of the expansion valve, it becomes a low-temperature and low-pressure mist hydraulic refrigerant, creating conditions for the evaporation of the refrigerant;

2. Control the flow of refrigerant: the liquid refrigerant entering the evaporator, after passing through the evaporator, the refrigerant evaporates from the liquid state to the gaseous state, absorbs heat, and reduces the temperature in the car. The expansion valve controls the flow of refrigerant to ensure that the outlet of the evaporator is completely gaseous refrigerant, if the flow rate is too large, the outlet contains liquid refrigerant, which may enter the compressor to produce liquid shock, if the refrigerant flow is too small, the evaporation is completed in advance, resulting in insufficient refrigeration;

The expansion valve is an important component in the refrigeration system, generally installed between the liquid reservoir and the evaporator, the expansion valve makes the liquid refrigerant at medium temperature and high pressure become wet steam at low temperature and low pressure through its throttling, and then the residual refrigerant is prepared to absorb heat in the evaporator to achieve the refrigeration effect, and the expansion valve passes the superheat at the end of the evaporator.

Change to control the flow of the valve and prevent the use of the evaporator area without the phenomenon of sappra rolling foot and knocking on the cylinder.

Thermostatic expansion valve, also known as temperature regulating valve, in the refrigeration system, the thermostatic expansion valve is installed on the liquid supply pipeline of the evaporator inlet, and has three functions

Throttling and depressurizing. The high-temperature and high-pressure refrigerant after condensation of the condenser is throttled and depressurized to become a low-temperature and low-pressure vapor-liquid mixture that is easy to evaporate, enters the evaporator for evaporation, and absorbs external heat.

Regulate the flow rate. Based on the temperature signal from the sensing bag or the head of the airbox, the expansion valve automatically adjusts the flow of refrigerant into the evaporator to meet the changing needs of the refrigeration load.

Maintain a certain amount of overheat to prevent liquid shock and abnormal overheating.

The expansion valve makes the evaporation appliance have a certain degree of superheat through the adjustment of the flow rate, ensures the effective utilization of the total volume of the evaporator, and avoids the liquid refrigerant from entering the compressor and causing liquid shock; At the same time, it can control the overheating within a certain range to prevent the occurrence of abnormal overheating.

As a kind of throttle beam fierce flow mechanism in the refrigeration system, the expansion valve is one of the four basic system components necessary to realize the refrigeration cycle. It mainly has the following functions: throttling and depressurizing is mainly manifested in throttling and depressurizing the liquid refrigerant at room temperature and high pressure after condensation of the condenser, and then adjusting the flow of refrigerant flowing through the evaporator and controlling the superheat of the evaporator outlet.

The magnitude of this superheat is equal to the return air temperature of the system minus the evaporation temperature.

An electronic expansion valve is a type of throttle valve in a refrigeration system.

Throttle valves can usually be divided into capillary throttling, thermal expansion valve throttling (internal balance, external balance) and electronic expansion valve throttling, and expander throttling (however, this is usually not seen).

The main advantage of the electronic expansion valve is the ability to precisely control the refrigerant flow and thus the evaporation temperature. It is usually used in places where temperature control accuracy is required to be relatively high. Electronic expansion valves can work normally above -70 degrees, but thermal expansion valves can only reach a minimum of -60 degrees.

1. Throttling: liquid refrigerant with high temperature and high pressure.

Pass through the expansion valve.

After throttling, it becomes a low-temperature and low-pressure mist hydraulic refrigerant, which creates conditions for the evaporation of refrigerant

2) Control the flow of refrigerant: into the evaporator.

After passing through the evaporator, the refrigerant evaporates from the liquid state to the gaseous state, absorbing heat and reducing the temperature in the car. The expansion valve controls the flow of refrigerant to ensure that the outlet of the evaporator is completely gaseous refrigerantIf the refrigerant flow rate is too small, the evaporation will be completed in advance, resulting in insufficient refrigeration.

It mainly plays the role of throttling and depressurizing and regulating the flow rate. At the same time, it also has the function of preventing wet compression and liquid shock, protecting the compressor and abnormal overheating.