The heat pipe heat exchangers are used in heat recovery applications to cool the incoming fresh air in air conditioning applications.

Two streams of fresh and return air have been connected with heat pipe heat exchanger to investigate the thermal performance and effectiveness of heat recovery system. Ratios of mass flow rate between return and fresh air of 1, 1.5 and 2.3 have been adapted to validate the

heat transfer and the temperature change of fresh air. Fresh air inlet temperature of 32–40C has been controlled, while the inlet return

air temperature is kept constant at about 26C. The results showed that the temperature changes of fresh and return air are increased

with the increase of inlet temperature of fresh air. The effectiveness and heat transfer for both evaporator and condenser sections are also

increased to about 48%, when the inlet fresh air temperature is increased to 40C. The effect of mass flow rate ratio on effectiveness is

positive for evaporator side and negative for condenser side. The enthalpy ratio between the heat recovery and conventional air mixing is

increased to about 85% with increasing fresh air inlet temperature. The optimum effectiveness of heat pipe heat exchanger is estimated

and compared with the present experimental data. The results showed that the effectiveness is close to the optimum effectiveness at fresh

air inlet temperature near the fluid operating temperature of heat pipes.