Experimental investigation of natural convection boiling in concentric and eccentric vertical channel

An experimental program is conducted to study the heat transfer characteristics of natural convection boiling of water flowing in a vertical concentric and eccentric and eccentric annuli. The inner rod is uniformly heated and the water is allowed to reach saturation inside the annulus by increasing the heat flux and varying the water inlet temperature. The heat transfer results are represented by local and average Nusselt number. The influences of variable properties are accounted for by using empirical equations. The effect of eccentricity and inlet water temperature to the channel indicated to be of a great importance in evaluating the heat transfer coefficient. Test carried out for 5 x 10 6< Ra < 4 x 10 8 at different heat fluxes from 5 to 23 w/cm 2, yielded the following correlation: Nub = 2.6338 x 10-4. Ra 0.747. (Ti/Ts)1.436. (1+E) -0.24 which correlated the practical results with 0.97 significance value