Saturation temperature effects on heat transfer performance of a falling film evaporator using enhanced tubes

Abstract

In this work, the existing LTCM falling lm facility was utilized to perform falling lm evaporation measurements on a vertical row of horizontal tubes. The enhanced boiling tube, Wolverine Turbo-B5, was tested using R-134a and R-236fa. The tests were carried out at di erent saturation temperatures of: 7.5 C, 10 C, 12.5 C, 15 C, 17.5 C, 20 C, 22.5 C, 25 C, 27.5 C and 30 C adding them to the existing 5 C saturation temperature in the database from previous work. All the tests were carried out with liquid lm Reynolds numbers ranging from 0 to 3000, and nominal heat uxes of 20, 40 and 60 kW/m2. The experimental results for all temperatures are compared with the current prediction method of Christians (2010). The e ects of the di erent saturation temperatures on the heat transfer coe cient were analyzed and compared for R-134a and R-236fa. Pool boiling heat transfer coe cients were measured in the LTCM pool boiling facility to obtain the falling lm multiplier Kff (Falling lm heat transfer coe cient relative to pool boiling coe cient at the same heat ux). These tests were carried out at 20 C and 30 C for both R-134a and R-236fa. Finally an uncertainty analysis of the refrigerant lm Reynolds number was carried out in order to quantify the error in its calculation and a new lter for the experimental data was proposed.