In this work, an experimental study is conducted on the performance of heat pipes heat exchanger for the application of heat recovery in air conditioning. To carry out this work, a heat pipe heat exchanger is installed between fresh air and return air to cool the fresh air. Three test sections were used with different inner pipe diameters of 7.9, 10.2 and 16.56 mm. The fresh air inlet temperature was changed to be 30 ºC, 35 ºC, 40 ºC, 45 ºC and 50 ºC in order to simulate the change of ambient temperature. The ratio between cooled and fresh air was chosen to be 1, 1.5, 2 and 3. The results obtained indicated that the effectiveness of the heat pipe heat exchangers increases with both of the increase of fresh air inlet temperature and the ratio between cooled and fresh air.