The effect of the heat loads on the partial-vacuum thermosyphon performance

In the present research, the effect of the heat flux and the cooling water flow rate of the condenser on overall performance of partially vacuumed thermosyphon were studied. A rig was made from a 1 m copper tube with an inside and an outside diameter of 17.5 and 19 mm. The heights of the evaporator, the adiabatic section and the condenser are 40, 20 and 40 cm respectively. The temperatures at different places on the thermosyphon and on the inlet/outlet of the cooling water were measured. It was observed that with increasing of heat flux to the evaporator the thermosyphon performance increased. On the other hand, with decreasing of the cooling water flow rate, the performance of the thermosyphon was increased as the trapped air moved toward the end of the condenser. In order to illustrate the effect of existence of air to deactivating the thermosyphon, the pipe was cool down by disconnecting of power input to the evaporator. It was seen that the thermosyphon loss its performance as the trapped gas occupies the whole condenser. The whole study shows due to existence of air, the heat loads can have significant effects on the performance of the thermosyphon.