ANS:B -

In a counter-current heat exchanger, the direction of flow of the hot fluid is opposite to the direction of flow of the cold fluid. This arrangement allows for a larger temperature gradient along the length of the heat exchanger, resulting in more efficient heat transfer. Given the temperature conditions provided:

• h=50∘CTh​=50∘C (inlet temperature of hot fluid)
• c=60∘CTc​=60∘C (inlet temperature of cold fluid)

And since the temperature difference between the two streams is the same everywhere along the length (in=50∘C−30∘C=20∘CΔT=Th,in​−Tc,in​=50∘C−30∘C=20∘C), the temperature profile should satisfy the condition where the hot fluid gradually decreases in temperature along the length of the heat exchanger, while the cold fluid gradually increases in temperature along the length. This means that as we move along the length of the heat exchanger, the temperature of the hot fluid should decrease, and the temperature of the cold fluid should increase. Therefore, the direction of flow of the hot fluid should be from a higher temperature region to a lower temperature region. So, the direction of flow of the hot fluid should be opposite to the direction of flow of the cold fluid, as observed in a counter-current heat exchanger.