4170 -- Visualization Study of Enhanced Flash Boiling or R-22 with 5 mm Steel and Glass Spheres PDF

This paper presents the qualitative results and discussion from an experimental investigation of passive enhanced flash boiling of R-22 (an HCFC) from a small vessel. A bench-top experimental apparatus was used to conduct enhanced flash boiling tests with 5.0 mm diameter steel and glass spheres placed at the base of the glass vessel. Sixty-second experiments were conducted with initial refrigerant amounts of 0.23 kg and 0.68 kg (0.5 lbm and 1.5 lbm), exiting orifices of 1.59 mm and 5.56 mm in diameter (0.063 in. and 0.219 in.), and with an initial pressure of 840 kPa (122 psia). The experiments were designed to simulate the flash boiling process that occurs within the refrigerant accumulator of air-source heat pumps during the reverse-cycle defrost. Results from the visualization study include a complete description of the flashing process with added steel and glass spheres. It was also shown that the enhancement method significantly increased the rate of total vapor production by 24% - 55% when exposed to a rapid depressurization.

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