Narrow Gap Boiling in A Spray -and-Tube Evaporator

• Main Authors: Yuh-Shyh Lee, 李育世
• Other Authors: Jenq-Shing Chiou
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/92919730039661864431

碩士 === 國立成功大學 === 機械工程學系 === 88 === R-141b is used as the coolant and sprayed on a horizontal tube bundle to simulate the spray shell-and-tube Evaporator. Pool boiling experiments were also conducted and compared with the spray cooling tests under the same test conditions. In this study, a liquid collector is installed under each heater tube to prevent the dry-out phenomena. Since the heat transfer characteristics of boiling between the confined space between liquid collector and heater tube is different from that of open space boiling, efforts were focused on the narrow space boiling experiments. The test results indicated the dry-out would be found earlier as the gap between liquid collector and heater tube became narrower. Before the occurrence of dry-out, the heat transfer coefficient is creases when gap size decreases. In pool boiling tests, the maximum heat flux before the occurrence of dry-out is decreased as the gap is closer, however, this kind of heat flux decline is not found obviously in the spray tests. The results imply the heat transfer performance will be greatly enhanced with only slightly sacrifice in heat release ability for sprayed cooling.