A most elaborate design is used for secondary refrigerant cooling which tank the form of a shell and tube vessel.
Such a type is illustrated in 9.5 and employs direct expansion.
in this case the refrigerant passes through the tube and the secondary refrigerant is passes over the tube bank.
the refrigerant is sprayed into the tube so as to ensure an even distrbution through all the tube.
any oil present is not spray and drains away.
in this type of evaporator two features are employ to improve heat transfer efficiency.
on the refrigerant side there is a centre tube with a spiral fin fitted around it or the insert may be in the form of an aluminium star which has a spiral twist o it.
Also baffles are arranged on the brine side to deflect the brine across the tube bank