Question

In parallel flow heat exchangers...

Answer 1

Answer:

The correct answer is letter c: The exit temperature of hot fluid is always more than the exit temperature of cold fluid

Explanation:

Heat exchangers are used to exchange heat between two fluids so they are helpfull in cooling and heating processes. After the exchange the temperatures of the fluids that participate are changed so both option d and b: (The exit temperature of hot fluid is always equal to the exit temperature of cold fluid) and (We cannot predict comparison between exit temperatures of hot fluid and cold fluid) are INCORRECT.

In which has to be with option a: (The exit temperature of hot fluid is always less than the exit temperature of cold fluid). It is INCORRECT because the maximum temperature that can be reached by the cold fluid is the one that has the hot fluid. That is the ideal situation of thermal equilibrium in which both fluids leave the exchanger at the same temperature, that does no happen, so the real situation is the one described in option c "The exit temperature of hot fluid is always more than the exit temperature of cold fluid". Both fluids exchange heat till the force that may that possible allows that, that force is the difference of temperature between them so when that difference reachs a minimum the process stops.