Brazed plate heat exchangers used for HVAC applications normally use a parallel flow to achieve the most efficient heat transfer. In a single-pass design, all the connections are located on one side of the heat exchanger, making installation very easy.
Alternate channel pattern
When used as an evaporator, the channels formed between the corrugated plates and corners are arranged so the two media flow through alternate channels, always in opposite directions (counter-current flow). The two-phase refrigerant (vapour + liquid) enters at the bottom left of the unit. The vapour quality depends on operating conditions in the refrigeration plant.
Evaporation of the liquid phase takes place inside the channels. Some degree of superheating is always required – hence the process being called "dry expansion". The dark blue and light blue arrows show the location of the refrigerant connections. The water (brine) to be cooled flows counter-currently in the opposite channel; the dark and light red arrows show where the water (brine) connections are.
AC line as condenser
When used as a condenser, the main components are still the same as for the evaporator. The refrigerant enters at the top left as a hot gas and starts to condense on the surface of the channels. Once fully condensed, it is then subcooled slightly, in a process called "free condensation". The dark and light blue arrows show the location of the brine connections. The refrigerant flows counter-currently in the opposite channel and is cooled. The dark and light red arrows show where the refrigerant connections are.
Brazed plate heat exchangers are widely used in refrigeration plants. They are normally used to transfer heat from the refrigerant – the primary fluid – and from water or brine as the secondary fluid.
Units in the Alfa Laval AC line of copper-brazed heat exchangers are mainly used as:
They can also be used as:
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