Local Bundle Boiling Heat Transfer Coefficients on a Plain Tube Bundle (RP-1089)

摘要

Experiments have been performed for evaporation of refrigerant R-134a on the outside of a bundle of plain tubes. The test setup is of a novel design-one that uses water flowing through the tubes as the heat source with temperature measurements of this water taken at numerous axial locations within the tubes, allowing for an accurate measurement of the water profile as it traverses the tube bundle and the measurement of twelve local heat transfer coefficients in the bundle. For characterizing the heat transfer coefficient on the waterside, a modified Wilson plot technique was used with the Gnielinski heat transfer coefficient correlation. Pool boiling tests to measure the corresponding nucleate boiling curves were performed. Tests were conducted with a 20-tube bundle over ranges of heat flux (2-35 kW/m{sup}2), mass flux (5-41 kg/m{sup}2s), and vapor quality (10%-87%). The bundle test results showed a significant contribution of convection to the heat transfer process with local heat transfer coefficients as large as 1.4 times those of nucleate pool boiling.