Thermophysical Properties of Biporous Heat Pipe Evaporators

Thirty biporous slugs with 3 different cluster diameters and 5 different particle diameters (15 combinations with 2 repetitions) and 12 monoporous slugs with 6 different particle diameters were sintered from spherical copper powder, and thermophysical properties were measured. The neck size ratio for all the particles was approximately 0.4. The porosity of monoporous samples was found to be independent of particle diameter and was equal to 0.28, and the porosity of biporous samples was found to be independent of cluster and particle diameters, and was equal to 0.64. The liquid permeability and maximum capillary pressure of small pores were found to be a linear function of the particle diameter. Similarly, vapor permeability was found to be a linear function of the cluster diameter. The thermal conductivity of monoporous samples was measured to be $142±3W∕mK$ at $42±2°C$⁠, and it was independent of particle diameter. The thermal conductivity of biporous samples was found to be a function of cluster to particle diameter ratio.