AN EXPERIMENTAL STUDY ON THE EFFECTS OF TUBE POSITION AND SPACING IN A BUNDLE POOL BOILING HEAT TRANSFER

In this paper, an investigation on the effect of the tube positioning on the pool boililing heat transfer coefficient is presented. Experiments were performed for R123 at a reduced pressure of 0.022, average surface roughness of 0.12 µm, and heat fluxes from 1 to 40 kW/m 2 . Bundles containing 2 and 3 horizontal, electrically heated brass tubes were used in the experiments. The effect of tube spacing on the heat transfer coefficient were also investigated. Experimental results have shown that thermal performance of the bottom tube of the row presents similar thermal behavior as a single tube in a pool over the whole range of heat flux. However, the upper two tubes present distinct behavior depending on the heat flux range. Under partial nucleate boiling, thermal performance of the two upper tubes is better than the bottom one. However, as the heat flux increases and boiling becomes fully developed, thermal performance of the three tubes tends to be similar.