The condenser is an essential component in refrigerant systems.
The normal function of a condenser is to transform hot discharge gas from the compressor to a slightly sub-cooled liquid flow, by transferring heat from the refrigerant gas to the secondary cooling liquid.
Condensers do more than condensation
The basic operation of condensers is divided into three parts: desuperheating, condensation and sub-cooling. All three operations can be carried out inside the condenser. The total heat transfer is called the Total Heat of Rejection (THR). Alternatively, the desuperheating or sub-cooling operation can be carried out in a separate heat exchanger.
Refrigeration condensers with high efficiency
When a SWEP brazed plate heat exchanger 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´s brazed plate heat exchangers 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.
Desuperheating with condensers
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.
Subcooling with condensers
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.
Heat exchangers that take latent heat from a saturated vapour at a constant temperature
Condensers in the context of brazed plate heat exchangers are heat exchangers that take latent heat from a saturated vapour at a constant temperature to convert the vapour to a liquid. For most cases in brazed plate heat exchangers this is in applications such as refrigeration or air-conditioning where heat is taken from a refrigerant and given to a fluid such as water to be expelled into the atmosphere via cooling towers.
A brazed plate heat exchanger uses a secondary fluid, such as water, which is at a lower temperature than the refrigerant vapour. Latent heat of the vapour is transferred to the secondary fluid as sensible heat and hence converts the refrigerant to a liquid without changing its temperature.
Condensers can last 15 years
If correctly designed, installed and maintained, a brazed plate heat exchanger condenser can last typically 15 years. This is dependent on on no excessive thermal stresses that can be imparted by the compressor, and that water quality is of a standard that does not lead to fouling or corrosion.
Freezing may occur when operating a refrigeration or heat pump cycle in reverse or running in de-frost mode. Design provisions can be made to stop the freezing from occurring.