In a counter flow heat exchanger, for the hot fluid the heat capacity $$= 2kJ/kg$$ $$K,$$ mass flow rate $$= 5 kg/s,$$ inlet temperature $$ = {150^ \circ }C$$, outlet temperature $$ = {100^ \circ }C$$. For the cold fluid, heat capacity $$= 4 kJ/kg$$ $$K,$$ mass flow rate $$= 10 kg/s,$$ inlet temperature=$$ = {20^ \circ }C$$. Neglecting heat transfer to the surroundings, the outlet temperature of the cold fluid in $$ = {^ \circ }C$$ is

Air enters a counter-flow heat exchanger at $${7^ \circ }C$$ and leaves at $${40^ \circ }C$$. Water enters at $${30^ \circ }C$$ and leaves at $${50^ \circ }C$$. The $$LMTD$$ in deg $$C$$ is

In certain $$HE,$$ both the fluids have identical mass flow rate-specific heat product. The hot fluid enters at $${76^ \circ }C$$ and leaves at $${47^ \circ }C$$ and the cold fluid entering at $${28^ \circ }C$$ leave at $${55^ \circ }C$$. The effectiveness of the heat exchanger $$(HE)$$ is