The heat transfer characteristics of experimental scale bundles, composed of both smooth and enhanced tubes, were investigated in search of methods to improve the performance of flooded-type evaporators. The saturated nucleate boiling of Freon 113 was employed. It was found that (i) in the smooth tube bundles heat transfer is enhanced in the upper tubes due to forced convective flow induced by bubbles rising from the lower tubes but not in the high heat flux region of the lower tubes where the bubbles are generated, (ii) the enhancement in heat transfer is not observed for the enhanced tube with a thin layer of sintered particles in the whole range of heat flux tested, and (iii) the tube bundle effect becomes weak as the system presssure is increased. A heat transfer model is tentatively proposed to explain the observed tube bundle effect, which differs in magnitude depending on such variables as bundle geometry, pressure, heat flux, location in a bundle and nucleation characteristics of tubes.
|ジャーナル||Memoirs of the Kyushu University, Faculty of Engineering|
|出版ステータス||出版済み - 12月 1 1984|
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