A closed loop heat pump dryer (HPD) system was preferred at drying processes. Because it gains sensible and latent heat from hot and humid drying air exhausted. This study deals with the drying of four different agricultural products at 40 degrees C drying chamber temperature via heat pump assisted dryer with closed. Different from literature in this system, drying air temperature in dryer cabinet was controlled by cutting in external condenser with internal condenser. Besides, mean coefficient of performance of HP system was calculated by considering activation rate of external condenser with internal condenser. Experiments were performed on 5 mm thick slices of banana, kiwi apple and melon with an air flow of 1 m/s without any prior modification. At the end of study, the highest SMER value of 0,332 kg/kWh was obtained with melon, whereas the lowest value of 0,232 kg/kWh with banana. The highest mean performance coefficients of whole system (COPsys) were calculated as 2.75 with kiwi whereas the lowest value of 2.49 with banana.