Question

Can the temperature of the hot fluid drop below the inlet temperature of the cold fluid at any location in a heat exchanger? Explain.

Short answer

Answer: The hot fluid's temperature cannot drop below the cold fluid's inlet temperature because heat transfer occurs naturally from a higher temperature to a lower temperature. If the hot fluid dropped below the cold fluid's inlet temperature, it would imply heat transfer in the opposite direction, which is not possible in a heat exchanger.

Step-by-step solution

Understand heat exchangers

A heat exchanger is a device used to transfer heat between two fluids without mixing them. It is typically used for heating or cooling processes in various industries. The main principle behind the operation of a heat exchanger is the exchange of heat energy between the hot fluid (with a higher temperature) and the cold fluid (with a lower temperature).

Analyze the process of heat exchange

The hot fluid flows through the heat exchanger and transfers its heat to the cold fluid. This causes the cold fluid to increase its temperature and the hot fluid to decrease its temperature. The process continues as long as there is a temperature difference between the two fluids.

Recognize the limitations of heat exchange

The heat exchange process is driven by the temperature difference between the hot and cold fluids. The heat transfer will continue until the temperature difference becomes minimal or the exchange process reaches equilibrium. However, there is always some difference in temperature between the fluids to ensure the heat transfer is still occurring.

Explain why the hot fluid's temperature cannot drop below the cold fluid's inlet temperature

The hot fluid cannot drop below the cold fluid's inlet temperature because it would mean that heat transfer is happening in the opposite direction – from the cold fluid to the hot fluid. However, this is not possible since heat transfer occurs naturally from a higher temperature (hot fluid) to a lower temperature (cold fluid). Hence, the hot fluid's temperature can never drop below the cold fluid's inlet temperature at any location in a heat exchanger. In conclusion, the temperature of the hot fluid cannot drop below the inlet temperature of the cold fluid at any location in a heat exchanger due to the nature of heat transfer, which always occurs from a higher temperature to a lower temperature.