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ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

Heat Transfer Characteristics of R-134a in a Capillary Tube Heat Exchanger

Get access (open in a dialog) DOI: 10.1615/IHTC11.1430
pages 131-136

摘要

A fundamental study for a novel high efficiency heat exchanger without microfins which uses capillary tubes is conducted for refrigeration, air-conditioning and heat pump applications. This type of heat exchanger has the advantages of small size, effectiveness of heat transfer surface, unnecessari-ness of traditional microfins, low production costs, and ease to handling, etc. The present research intended to examine the effects of capillary tube diameters, qualities, heat fluxes, mass fluxes on heat transfer during evaporation inside capillary tube. Experiments were performed for mass flux ranging from 240 to 720 kg/m2s, qualities from 0.1 to 1, heat fluxes from 10 to 20 kW/ m2s. The facility consisted of a closed cycle R-134a flow circuit driven by a compressor. Test section consisted of capillary tubes. The capillary tubes were 500 mm long and had 2, 1.0, and 0.75 mm inside diameter. The heat load of the capillary tube was supplied by a heating elements.
From the data obtained we discussed the evaporative heat transfer, the type of dry-out, and the applicability of capillary tube to heal exchangers. In addition, a systematic verification of the previously proposed correlation against experimental data was made and a new experimental formula for convective heat transfer in capillary tubes of R-134a was suggested.