Three models for finned evaporators are presented. A finite element model, analysing the coil in geometrically fixed elements, is used to study the local behaviour of heat transfer fluids and the effect of refrigerant-side pressure drop on heat transfer performance, a three-region model, neglecting refrigerant-side pressure drop effects on evaporator performance and any dehumidification in the region of superheated refrigerant, is derived for use in evaporator analysis and design, finally a parametric model is constructed in which coil performance is described by a coil characteristic and a coil effectiveness parameter. This parametric model is suitable for use in heat pump simulation programs since it requires the least computer memory and the least computing time. The models predict evaporator performance under dry, wet, and frosted surface conditions. The transient frosted evaporator performance is analysed assuming quasi-steady state where calculations at one time step can be used for analysis at the next time step. The models were verified by comparing computer-simulated results with experimental results for one six-row evaporator and one single-row evaporator.

 

KEYWORDS: finned tubes, heat flow, evaporators, calculating, models, dry, wet, frost, performance, heat transfer fluids, comparing, pressure drop, computers, experiment, superheaters.