Exercise-1

 Regenerator receives hot flue gases at   and cold air at , the flue gases leave at   and the air is  preheated to . As estimated of the heat given up by the flue gases is heat lost to the regenerator surroundings, and the rest  is recovered in the preheated air. It may be assumed for estimating purposes that  for flue gases and  for air, independent of temperature. Estimate over all thermal efficiency, efficiency limit, and relative efficiency for this heat exchange operation.

Suppose now that the depth of the regenerator is increased to 2.5 times in such a way to double   the heat exchange area   while keeping constant the over-all heat transfer coefficient .The quantities  and entering temperatures of the flue gases and air will be kept the same. Heat losses are same as  that in above case . Estimate for the enlarged regenerator (a) air preheat temperature, (b) over-all  thermal efficiency and relative thermal efficiency