An experimental study for the boiling heat {transfer in a closed loop heat pipe was achieved by using saturated porous medium instead of pure water in the evaporator section. An experimental test loop equipped with the required measuring devices was designed and constructed to assess the effects of applied heat flux, porosity of porous medium in the evaporator section on the boiling heat transfer process. The tested porous media are balls made from iron coated with nickel. Four porous media are tested, each one consists of balls of diameter 4.73, 3.94, 3.12, and 2.47 mm respectively. The experimental measurements of temperature. pressure and volume flow rate are recorded and manipulated to calculate the boiling heat transfer coefficient and the enhancement factor for the boiling heat transfer coefficient when using porous media instead of water only in the evaporator section of heat pipe,
The obtained experimental results show that, the evaporator wall temperature was reduced by using porous media compared with water only. Accordingly, the boiling heat transfer coefficient increased for closed loop heat pipe when using porous media and increased also with increasing heat flux. The enhancement factor of the boiling heat transfer coefficient increased with decreasing porosity up to the value of 0.4 then it decreased. The optimum operating conditions for the studied closed loop heat pipe when using porous media in the evaporator section al porosity about 0.4 and heat flux about 38600 W/m2 There. the enhancement factor lakes the highest value equal to about 2.5. Comparison with the previous work gave the same trend