Features

The heat and moisture exchange of the condenser is between the temperature difference of the main air and the boundary layer air tightly adhering to the outside surface of the heat exchanger.Vapor pressureThe process is conducted under adverse conditions. It can achieve two types of air treatment: when the air temperature of the boundary layer is below the dew point temperature of the main air, a dehumidifying cooling process, also known as a wet cooling process (wet condition), occurs; when the air temperature of the boundary layer is lower than that of the main air but still above its dew point temperature, an isothermal cooling process occurs (dry condition).

During the dehumidification cooling process, there is not only a temperature difference but also a vapor pressure difference between the boundary layer air and the bulk air. Therefore, not only sensible heat exchange occurs at the heat exchanger surface, but also latent heat exchange associated with moisture transfer. Consequently, the surface cooler under humid conditions has a greater heat exchange capacity compared to dry conditions. In other words, for the same surface cooler, when the dry bulb temperature of the treated air and the water temperature remain constant, the higher the wet bulb temperature of the air, the greater the cooling and dehumidifying capacity of the surface cooler. 

Thermo-mechanical Calculation

The air cooler is primarily used for air cooling and dehumidification, resulting in changes to both the air temperature and humidity content.

1. Heat Exchanger Efficiency of the Condenser

Full Heat Exchange EfficiencyIn the formula:—Dry bulb temperature of air before and after treatment, ℃;Cold water temperature, ℃.

(2) General Heat Exchange Efficiencyt3—Desired air temperature after treatment, in °C.

2. Heat Exchanger Thermal Calculation Type

There are two types: one is design-oriented, commonly used for selecting standard air coolers to meet known initial and final air parameters.

Processing requirements; The other is a verification type, commonly used to check how a certain type of air cooler can process air with specific air parameters to reach certain final parameters.

3. Heat Transfer Calculation Methods for Condensers

The Dry Bulb Temperature Efficiency Method—For a specific type of evaporative cooler, the thermodynamic calculation principles should meet the following conditions:

(1) Air Treatment Process Required EgShould equal the E that the condenser can achieveg；

(2) The required E for the air treatment process should equal the E that the cooling coil can achieve.

(3) The heat released by the air should equal the heat absorbed by the cold water.

4. Consideration of safety factor in the thermodynamic calculation of condensers

After prolonged use, the heat exchanger's thermal conductivity may decrease due to reasons such as accumulated dust on the outer surface and scaling on the inner surface. To ensure the continued safe and reliable operation of the heat exchanger under these conditions, a certain safety factor should be considered during selection and calculation. The safety factor can be accounted for by increasing the heat transfer area, such as by adding rows or increasing the windward area. However, due to limited product specifications, this method often does not allow for an exact safety factor or may complicate the selection and calculation process. Therefore, in engineering, it can be considered that:

(1) At the outset of calculation selection, the obtained EgMultiply by safety factor a. For cooling-only condensers, take a = 0.94; for dual-purpose chillers, take a = 0.9.

(2) Safety factors are not considered in the calculation process. After selecting the evaporator specifications, further reduce the calculated initial water temperature. The reduction in initial water temperature can be considered as 10% to 20% of the water temperature rise. 

Cautionary Notes

When the air conditioner is not in use during winter, the remaining water in the pipes should be drained to prevent freezing temperatures from causing the steel pipes to crack.

The water in the cooler should not contain impurities, such as sand.

(3) Ensure adequate insulation during winter to minimize heat loss or prevent pipe icing.