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Buildings—Reaching the boiling point

Researchers at Oak Ridge National Laboratory demonstrated that metal foam enhances the evaporation process in thermal conversion systems and enables the development of compact heating, ventilation and refrigeration, or HVAC&R, units. Compact and efficient HVAC&R equipment is needed to support the global industry transition to using alternative, environmentally friendly refrigerants. The small-scale evaporator proved metal foam is well-suited for compact systems. “We found that the presence of a porous open cell or sponge-like metal foam layer in an evaporator’s tubes increases the liquid refrigerant’s boiling rate, creating essentially an enhanced pool-boiling process that can accommodate much higher heat fluxes compared to conventional technology,” ORNL’s Kashif Nawaz said. “Enhancement materials like metal foams increase equipment efficiency by improving the phase change or vaporization process.”