Numerical evaluation of a compact generator design for steam driven H2O/LiBr absorption chiller application

Abstract

The objectives of this study are to analyze effects of design parameters of a generator with a steam heat source on condensation heat transfer and flow characteristics inside tubes and to design optimum configuration of the generator with minimum volume that satisfies design constraints for H2O/LiBr absorption chiller application. To that end, the heat transfer and flow characteristics of a straight-pipe tube and a tube with return bends were analyzed through numerical analysis according to the tube diameter, number of tubes, and the diameter of return bends. It was found that the minimum tube volume satisfying the design constraints was obtained for Ntube=2 and Dtube=12mm in the case of the straight tube. The smaller the diameter of the return bend was, the greater the flow separation area, which caused a large local flow velocity. In the case of the return bend tubes, the smallest tube volume that satisfies both the flow and pressure drop constraints was obtained for Ntube=2 and Dturn/Dtube=1.0. In the case Dturn/Dtube=1.5, where the pressure drop was the smallest, the pressure drop was higher by 9% compared to the pressure drop constraint (1 bar), but the tube volume that satisfies the flow constraints decreased by 49%.