Construction of condenser plays important role for efficient operation of energy systems. In this system a heat pipe is utilized for heat transfer. The condensation part of the heat pipe is situated on top of the heating zone. The condenser is placed in the heating zone and is used for efficient heat transfer from one medium to another. The thermal oil is used as cooling medium in the condenser. This paper analyzes the effect of different operation condition of thermal oil to thermal performance. From the collected results it is obvious that the larger mass flow and higher temperature cause better thermal performance and lower pressure drop.