Functions and Types of Condensers in Refrigeration System

Figure 1: Condensers.

Condenser, a component of the refrigeration system, is a type of heat exchanger that can convert gas or vapor into liquid, and transfer the heat in the tube to the surrounding air in a very fast speed. The working process of the condenser is an exothermic process, so the temperature of the condenser is relatively high.

Condensers have a wide range of applications in the industrial field.
Many condensers are used in power plants to condense the steam discharged from the turbine;
Condensers are used in refrigeration area to condense refrigerant vapors such as ammonia and Freon;
Condensers are used in the petrochemical industry to condense hydrocarbons and other chemical vapors;
During the distillation process, the device that transforms the steam into liquid is also called a condenser.

So what kind of role does the condenser play in the refrigeration system? All condensers operate for removing heat from a gas or vapor. This article mainly introduces the functions and main types of condensers in refrigeration systems.

1. Function of Condenser

For vapor compression refrigeration systems, the function of the condenser is to condense the high-temperature refrigerant vapor discharged from the compressor into liquid refrigerant to complete the heat exchange of the refrigeration system. In the refrigeration system, the evaporator, condenser, compressor and throttle valve are the four essential parts.

Among them, the evaporator is a device that transports cold energy. The refrigerant in the evaporator absorbs the heat of the surrounding object to achieve refrigeration.
The compressor is the heart, which plays the role of sucking in, compressing, and transporting refrigerant vapor.
The condenser is a device that releases heat, and transfers the heat absorbed in the evaporator together with the heat transformed by the work of the compressor to the cooling medium.
The throttle valve plays the role of throttling and reducing the pressure of the refrigerant, and at the same time controls and adjusts the amount of refrigerant liquid flowing into the evaporator, and divides the system into two parts: the high-pressure side and the low-pressure side.

Figure 2: Working principle diagram of refrigeration system.

In a condenser, refrigerant gas passes through a long tube (usually coiled into a solenoid) to release heat to the surrounding air. A metal such as copper is a good conductor of heat and is often used to transport vapor in a condenser. The condenser is usually cooled by normal temperature fluids such as air and water, and sometimes by other fluids with lower temperatures.
In order to improve the efficiency of the condenser, heat sinks with excellent thermal conductivity are often added to the pipes to increase the heat dissipation area and to accelerate heat dissipation, and the air convection is accelerated through the fan to take away the heat.

The condenser is an important device for the refrigeration system to release heat to the surrounding environment. Therefore, whether the condenser is good or bad will directly affect the cooling capacity and cooling efficiency of the refrigeration system.

1.1 Three Functions of Air Conditioner Condenser

The following will take the air conditioner condenser as an example to talk about the three major functions of the condenser. The air conditioner condenser is used in refrigeration and air conditioning systems, and the refrigerant liquid in the tube directly exchanges heat with the air outside to achieve the effect of cooling the air.

The condenser, that is, the outdoor heat exchanger, is a high-pressure equipment of the system when cooling (the cooling and heating heat pump type is low-pressure equipment when heating), and is installed between the compressor exhaust port and the throttling device (capillary tube or electronic expansion valve). The high-temperature and high-pressure gas discharged from the air-conditioning compressor enters the condenser, and is cooled by copper tubes and aluminum foil.
Air conditioners, equipped with axial flow cooling fans, are air-cooled, so that the pressure of the refrigerant does not change and the temperature is dropping during the cooling and condensation process when becoming from gas to liquid.

Figure 3: Air conditioner condenser.

The process of refrigerant change in the condenser can be regarded as an isothermal change process in theory. In fact, it has three functions.
(1)One is that the surrounding air takes away the superheated part of the high-temperature air-conditioning refrigerant gas discharged by the compressor, making it dry and saturated vapor;
(2)The second is to make the refrigerant vapor liquefy at constant saturation temperature;
(3)The third is to play a cooling role. When the air temperature is lower than the condensation temperature, the liquefied refrigerant is further cooled to the same temperature as the surrounding air.

2. Types of Condensers

With the continuous development of the refrigeration industry and the rapid expansion of its applications, there are various types of condensers. Commonly used condensers can be simply divided into three types according to the cooling medium they use:
(1) Air-cooled type
(2) Water-cooled type
(3) Evaporative condenser.

2.1 Air-Cooled Condenser

The air-cooled condense refers to a condenser that condenses refrigerant vapor into a liquid by the air in the surrounding environment. In this type of condenser, the heat released by the heat medium is taken away by the air, and the air can be natural convection or forced convection from a fan.

According to the air flow mode, air-cooled condensers can be divided into two types: natural convection type and forced convection type.

Figure 4: Air-cooled condenser.

2.2 Water-Cooled Condenser

Water-cooled condensers use water for cooling. Since the thermal conductivity and specific heat capacity of water are much higher than those of air, the water-cooled condenser has a large condensation capacity and is suitable for systems with large cooling capacity requirements.
The cooling water can be natural water, tap water or circulating water that passes through the water cooling tower. Natural water is easy to foul the condenser, which needs to be cleaned frequently. Tap water is commonly used for small devices, and circulating water is used for large and medium-sized devices.

According to different structures, water-cooled condensers can be divided into three types: horizontal shell and tube type, vertical shell and tube type and double tube type.

2.3 Evaporative Condenser

In this type of condenser, the heat medium is cooled by water and air at the same time, but it is mainly cooled by cooling water absorbing heat and evaporating on the surface of the heat transfer tube. The role of air is mainly to speed up the evaporation of water to improve the cooling efficiency.

This type of condenser consumes very little water. It is the preferred type of condenser for areas with dry air, low water temperature and insufficient water, and is very suitable for use in suburban and rural areas.

Figure 5: Working principle diagram of evaporative condenser.

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