What is Efficiency of shell and tube heat exchanger?

Answer 1

A shell and tube heat exchanger will have two fluids flowing through continuously. The fluid in the tube will typically be the important fluid, the fluid you are trying to heat or cool. The fluid in the shell will then be the fluid that is heating or cooling the the fluid in the tube.

Take a steam heat exchanger for example. Steam condenses in shell, while the the fluid in the tube picks up the heat from the steam. And in a perfectly efficient steam heat exchanger, all the heat lost from the steam would be recovered by the liquid in the tube.

But nothing is perfect. A little bit of the steam's heat makes the outer shell hot, and that in turn heats the room. Heat is lost from the steam into places other than the fluid in the tube. So efficiency measures how much of the heat lost by the shell fluid makes it into the tube fluid.

Efficiency (for heating) = Amount of Heat that went toward heating the fluid divided by the amount of heat that was lost by the heating fluid.

So an efficiency of 1 is perfect. For every 1 unit of heat absorbed by the tube fluid, we spent 1 unit of heat from the fluid in the shell fluid.

And if the efficiency is 0.9, or 90%, then for every 10 units of heat that the shell fluid lost, the tube fluid gained 9.

Sometimes efficiencies are as bad as 40%. In this case for every 10 units of heat lost by the heating fluid, 4 units are gained by the fluid.

A slightly different definition of efficiency applies to cooling:

Efficiency = Amount of heat lost by the tube fluid divided by the amount of heat gained by the shell fluid.

Same story, if the shell fluid gains 5 units of heat, and tube fluid loses 4, then the efficiency is 0.8 or 80%.

Answer 2

To cool oil the chilled water goes through the tube side and the hot oil to be cooled will go through the shell side of the unit.