BK1-8 Flooded Refrigerant Evaporators

J. W. Palen and R. L. Webb
1990; rev 08/2006

This report summarizes a study of refrigerant flooded evaporators (FREs) done for HTRI by Prof. Ralph Webb of Pennsylvania State University. The work consisted of assembling a data bank of operating conditions for several industrial evaporators and developing computer models to predict these data, starting with the current version of the HTRI RKH-2 Computer Program. It was found that typical refrigerant evaporators achieve relatively high boiling heat transfer coefficients due to high velocity two-phase forced convection across shallow tube bundles. The present HTRI RKH Computer Program was developed for kettle reboilers and was found to give conservative predictions of the heat duty of refrigerant flooded evaporators. Webb developed a new calculation structure which better fitted the geometry and process conditions for FREs, using recent literature methods for heat transfer and pressure drop. The resulting Pennsylvania State model gives good prediction of the available data for R-11 evaporators, and the model is used to study a variation of design parameters.

Due to the limited applicability of the Pennsylvania State model, a more generalized model was developed by HTRI which is presented as a preliminary version of a PC computer program. Additional work was done to determine how the RKH-2 Computer Program Mod. 0.10-1.06 horizontal thermosiphon option could be used to simulate these evaporator data, and recommendations are given.