Characteristics and Selection Methods of Chiller Evaporators
The chiller evaporator is a very important part of the four major components of refrigeration. The low-temperature condensed liquid passes through the evaporator and the outside air for heat exchange, absorbing heat to achieve the cooling effect. For the evaporator used for small chillers, we call it a low temperature evaporator, so what are the characteristics of the chiller evaporator? How to choose the right type of chiller evaporator? Let’s take a look at the following.
Evaporator features of low temperature chiller:
In the low-temperature evaporator, if it is a flooded chiller, the liquid column of the refrigerant in the evaporator cannot be too high, so as to avoid increasing the pressure of the liquid column at the bottom of the evaporator, increasing the evaporation temperature, and reducing the uniform temperature difference between the refrigerant and the air. , thereby reducing the cooling effect of the evaporator.
The heat transfer coefficient on the air side of the low-temperature evaporator is small, and the evaporator is often used to improve the heat transfer effect. The low-temperature evaporator is easily blocked by frost. Therefore, the fin spacing of the low temperature evaporator is larger than that of the normal temperature chiller, and the fin spacing is usually 6~10mm.
The choice of the evaporator of the chiller:
1. The water tank immersion evaporator uses an open circulation system with non-volatile refrigerant. For the production process of ice-making with brine ice-making pools, a closed-loop system cannot be used, so this type of evaporator is the only desirable type. Tank immersion evaporators are also available for chilled or bagged foods in brine, as well as chiller refrigeration systems with centralized spray air conditioning.
2. Salt water is very corrosive to ferrous metals, and when it comes into contact with air, its rusting effect is more severe. Therefore, when the production process allows, a closed loop should be used as much as possible. For volatile refrigerant circulation systems, closed circulation must be used. In both cases, the horizontal shell and tube evaporator for the chiller is the most suitable type.
3. When the bench-type chiller adopts a water tank immersion or shell-and-tube evaporator, the working temperature of the refrigerant should be about 5°C higher than that of the refrigerant evaporator, and the freezing point of the refrigerant should be higher than the refrigerant evaporation temperature. 5~8℃ lower (5~6℃ for water tank immersion evaporator, 6~8℃ for shell and tube evaporator).
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