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Evaporators

When a SWEP BPHE is used as an evaporator, a secondary gas or liquid is cooled as it loses heat to the refrigerant.

The evaporator is one of the essential components in refrigerant systems. When a SWEP BPHE is used as an evaporator, a secondary gas or liquid is cooled as it loses heat to the refrigerant. The refrigerant boils and is converted into a gas, absorbing more energy. A SWEP evaporator provides a good, stable boiling process with a small temperature difference between the refrigerant and the secondary fluid. A low temperature difference means that a higher evaporation temperature is possible, which corresponds to a higher pressure. Reducing the pressure difference between the low-pressure side (evaporator) and the high-pressure side (condenser) will reduce the energy use in the compressor. The higher evaporation pressure will also increase the density of the refrigerant gas. For each stroke, the compressor will therefore transport more refrigerant through the system. Lower electricity consumption and higher refrigeration capacity will increase the total system efficiency (COP). 

The evaporation process accounts for most of the heat transfer area of the evaporator. Although the superheating only accounts for approximately 5% of the total heat of absorption, the gas heating process normally takes up 10-25% of the total heat transfer surface. 

The image above shows the effects of superheat in an evaporator. 
Operating with a small superheat (a) there is more active surface available to evaporate the refrigerant. The result is a higher evaporating temperature and COP.

If instead the evaporator is unstable, a higher superheat is required (c) which results in a lower evaporation temperature and COP.

SWEP evaporators facilitate stable and efficient operation down to very low refrigerant flow rates and low superheat, due to our patented distribution systems. The distribution device introduces a pressure drop at the refrigerant inlet that ensures high flow turbulence and evenly distributed flow over the plate package.