When a SWEP BPHE is used as a condenser it receives refrigerant gas from the compressor.
The condenser is an essential component in refrigerant systems. When a SWEP BPHE is used as a condenser it receives refrigerant gas from the compressor. Heat transferred from the refrigerant to a water circuit may then be utilized for residential heating or hot tap water. Heat is transferred through gas cooling, condensation and subcooling of the liquid refrigerant, and the SWEP BPHE design enables efficient heat transfer in all three heat transfer regions. The temperature difference between the condenser inlet and outlet is thereby fully utilized by increasing the water temperature to approach or even exceed the condensing temperature.
The minimum temperature difference between the refrigerant and the secondary fluid in a counter-current condenser, the pinch, generally occurs at the beginning of the condensation process, point (b). This is particularly sensitive in a heat pump condenser because the temperature difference, between the condensing temperature and the leaving temperature of the secondary fluid (the temperature approach) is very small.
Reducing the temperature approach in an exaggerated manner risks unstable and partial condensing. The condenser performance of SWEP BPHEs has been tested and verified for close temperature approaches down to zero or even negative values between the condensing temperature and the leaving water temperature.
Heat pumps may be equipped with dedicated desuperheaters to make full use of the high-temperature (65-90 °C) gas from the compressor. It is single-phase heat transfer, with the temperature of the refrigerant gas falling typically by 20-50K. By charging a water accumulator with a heat pump, high-temperature water can be produced with an increased operational COP.
The refrigerant normally leaves the condenser at a temperature slightly lower than the saturation temperature. This subcooling represents approximately 2-5% of the total heat rejection and is necessary to avoid flash gas before the expansion valve. A dedicated subcooler can further reduce the temperature of the condensate, with several benefits. Increasing the subcooling reduces the amount of flash gas after the expansion valve. This increases the refrigeration effect because more liquid refrigerant will be available for evaporation. The improvement in the system performance, COP, is 0.5-2% per degree subcooling, depending on the type of refrigerant and the operating conditions.
SWEP offers various compact and cost-effective subcooler models depending on the system requirements.