European and American refrigeration technology

High efficiency • Energy saving • Environmental protection • Smart

　　In a flooded evaporator, the refrigerant goes through the shell side and the ice water goes through the tube side. In other words, the refrigerant goes outside the copper tube and the ice water goes inside the copper tube.

　　The opposite is true for dry evaporators. The refrigerant goes through the tube side while the ice water goes through the shell side. In other words, the refrigerant goes inside the copper tube and the ice water goes outside the copper tube.

　　Comparison of the two:

　　1. Working conditions and reliability

　　The flooded unit has many parts, complex circuits, and low unit operation reliability; dry unit has fewer parts, simple circuits, and reliable unit operation. The flooded unit is suitable for operation under constant operating conditions, and changes in operating conditions are likely to cause the unit to malfunction, while the dry unit can adapt to variable operating conditions.

　　2. Oil return performance

　　When the lubricating oil and refrigerant are mutually soluble, the oil return power of the flooded evaporator is the ejector pump, and the oil return is difficult and unstable, and the oil return condition directly affects the working conditions of the unit. The oil return power of the dry-type unit is high and low pressure difference, and the oil return is stable and convenient.

　　3. Liquid filling volume

　　The shell of the flooded evaporator is filled with refrigerant and has a large amount of liquid. It is mostly used for open-type compressors with easy refrigerant leakage and some screw compressors with large cooling capacity. The refrigerant charge of dry evaporator is only 1/2 to 1/3 of that of flooded evaporator.

　　4. Energy efficiency

　　The flooded unit has high energy efficiency, and the same input power flooded unit has a large cooling capacity, and the cooling capacity is 10%~12% larger than that of a dry unit.

　　5. Cost

　　The cost of the liquid unit is high, and the cost of the dry unit is low.

　　Advantages and disadvantages of flooded

　　Advantages: The evaporator has high heat exchange efficiency and higher energy efficiency than the dry evaporator. The same cooling capacity unit is slightly smaller than the dry type.

　　Disadvantages:

　　1. It is necessary to add a liquid level control device or a superheat control device to ensure that the flow of refrigerant entering the evaporator can maintain the liquid level at an appropriate height.

　　2. The price of the liquid level control device or the superheat control device is quite expensive, the maintenance and adjustment are very troublesome, and the adaptability is poor when the unit conforms to changes.

　　3. If the liquid level of the refrigerant in the evaporator is lowered, the refrigerating oil in the evaporator that is compatible with the refrigerant will not easily return to the compressor. The compressor may lose oil, which may directly cause the compressor to burn.

　　4. If the liquid level of the refrigerant in the evaporator is raised, the refrigerant will enter the compressor in liquid form, causing liquid compression, which will also cause the compressor to burn.

　　5. The charge of refrigerant and refrigerating oil in the whole system is more than twice that of dry type, and the maintenance cost will increase in the future.

　　6. Since the oil return of the flooded evaporator is very troublesome, the quality of the refrigerating oil is very high, and the refrigerating oil must be guaranteed to work under high quality. After using for a period of time, because the refrigerating oil will gradually thicken, it will be very difficult to return the oil and must be replaced immediately. Its life cycle is shortened by more than half compared with the dry evaporator, which greatly increases the operating cost.