Effect of compressed thickness on hydraulic and thermal characteristics of metal felt wick

The influence of compressed thicknesses on hydraulic and thermal characteristics of metal felt used in high temperature heat pipe solar receiver was investigated by hydraulic characteristic experiment with water and thermal numerical simulation in annular porous media with liquid metal sodium. The experimental results showed that the capillary pumping amount first increased and then decreased, and capillary force increased as compressed thickness decreased. The effective capillary radiuses were 69 μm at 1 mm, 176 μm at 2 mm, 218 μm at 3 mm and 274 μm at 4 mm, in good agreement with calculated values. The simulation results showed that the drag coefficient and Nusselt number were increased by decreasing compressed thickness. To obtain the large capillary force, high liquid storage capacity, small flow resistance and good thermal performance, the optimum compressed thicknesses of metal felt were 2-3 mm, which were 33-50% of initial thicknesses, and could well adapt to heat pipe solar receivers in high heat flux working condition.