Open porous evaporator structures made from aluminium and expanded glass – production, structure and thermal performanceDonnerstag (06.07.2017) 16:00 - 16:20 Uhr Bestandteil von:
Evaporation plays an important role in various technical thermodynamic systems like e.g. heat pumps. The power density and overheating temperature are essential parameters determining the heat transfer coefficient and the performance of the overall system. Various designs of evaporators have been developed, many of them based on porous metal structures which offer high specific surfaces and improved nucleation sites. In the presented work new composite evaporation structures were developed and analyzed. The structures are based on open cell aluminium sponges in which foamed clay granules are integrated into the surface of every strut. The main idea is that the embedded clay granules act as boiling enhancer. To produce test specimens preforms made from polymer lattices and foamed clay granules were infiltrated with aluminium melt by means of squeeze-casting. Subsequent decomposing of the polymer resulted in open porous aluminium sponges with embedded clay granules. Structural analysis was done using metallographic methods. For the thermal analysis pool boiling tests were done with water at low atmospheric pressures. The experiments showed that nucleate boiling started already at 4K overheating. Especially at low overheating temperatures an improved boiling performance was observed in comparison to reference structures (flat copper and open porous copper evaporator designs).