The main advantages of dry expansion chillers over the flooded type are the lower amount of refrigerant required for heat exchange and the positive oil return safety to the compressor. Also, as previously established, the possibility of damaging the chiller in the event of freezing is always less considerable when the cooled liquid is circulated over the tubes rather than through them.
In order to maintain the velocity of the liquid within the limits which will produce a more effective rate of pressure drop in the heat transfer, the velocity of the cooled liquid circulating over the tubes is controlled by varying the length and
distances from the segment deflector plates. When the high flow rate and / or liquid viscosity is low, extensive and spaced baffle plates are used to reduce speed and minimize pressure drop through the cooler.
When the flow rate is low or the viscosity is high, the baffle plates are less spaced narrower in order to increase the fluid velocity and improve the coefficient of heat transmission.
The number and length of coolant circuits required to maintain the refrigerant velocity through the cooling tubes within acceptable limits depends on the total charge of the cooler and the ratio of the flow rate of the cooled liquid to the actual average temperature difference . Since these factors vary with individual application, in fact, a well-designed optimal coolant circuit also varies with individual application. For this reason, the coolers are accessible with both multiple refrigerant circuits as well as simple and of varying lengths. The number and lengths are varied. They also depend on the length of the tube and the arrangement of the end baffles or the coolant inlets that are screwed to the tube blades at the ends of the cooler. The arrangement of the coolant circuit for any standard cooler can be changed by changing the coolant inlets.
