Shell and tube type heat exchanger

Heat exchangers are the machinery in which heat transfer takes place, one of its type used on ship is shell and tube type. Heat transfer takes place in mix flow pattern in this heat exchanger (cross flow, counter flow and parallel flow).The coolant flows through the tubes while the fluid to be cooled surrounds the tubes (Intercooler of compressors is exception).

Shell is made up of cast iron with end covers on either side and bundle of tubes is held inside the shell.The tubes are made up of aluminum brass and these tubes are sealed into the naval brass tube plates at both ends,one plate is fixed while other is free to allow for expansion & contration of the tubes.The tube bundle has baffles fitted which supports the stack and also serves to direct the liquid to be cooled up and down over the tubes for better cooling.

The fixed end plate is sandwiched between the shell and the end cover with gaskets on either side.The movable plate is provided with synthetic rubber 'o' rings for free expansion and contraction.If the liquid on either side leaks pass the seal it will come out of the tell tale hole which is presnt between the two 'o' rings and leakage is easily identified.

The end cover serves as inlet,outlet and return chamber.The inlet and outlet chamber is divided with the help of partition wall which provides two pass for the cooling tubes(''pass'' here means a set of tubes between bends or the turning of the flow).

The end covers are provided with inspection doors 2 on the inlet chamber,4 on the return chamber and 2 on the outlet chamber.The inspection cover serves 3 functions 

1. Inspects tubes for any leakage 
2. Holding the Sacrificial anode
3. Removing any physical obstruction in the stack of tubes

Zinc sacrificial anodes are fitted on the end covers,these anodes sacrifices itself to protect the tubes and shell from corrosion.

Temperature gauges are provided at the inlet and outlet of both the liquid to keep a check on the operation of the exchanger.Air vent and drain is also provided at both sides.