(A)Plain Tube (Water to Water):

1. The apparatus comprise of a pair of concentric tubes. Inner tube consists of copper tube through which hot water flows. 

2. While the outer tube consists of GI pipe through which cold water flows. The arrangement enables the parallel and counter flow of the cold water. 

3. The inlet and outlet temperatures and the flow measurement enable to find out the heat exchanged LMTD, and efficacy of the equipment.

(B) Finned Tube (Water to Air)

1. The apparatus involves of two concentric tubes. Inner tube consists of copper tube through which hot water flows. 

2. It is finned at its outer diameter to upsurge the heat transfer surface. While the outer tube consists of GI pipe through which cold air flows. 

3. The organisation enables the parallel and counter flow of the air. The inlet and outlet temperatures and the flow measurement enable to find out the heat exchanged LMTD, and efficiency of the equipment.