International Congress of Refrigeration 2007, Beijing LONGITUDINAL HEAT CONDUCTION IN FINNED-TUBE EVAPORATORS

The paper evaluates performance of finned-tube evaporators at different refrigerant exit superheats to assess the impact of longitudinal heat conduction on capacity. A combination of capacity measurements obtained from laboratory testing, the pattern of measured return bend temperatures, and the theoretical analysis suggests the occurrence of tube-to-tube transfer via fins and rejects the tube longitudinal heat transfer as the possible causes of capacity degradation. The impact of tube-to-tube heat transfer was negligible in tests with a uniform 5.6 °C superheat, but it was significant in tests involving 16.7 °C superheat. The measured difference in capacity between two evaporators – in one of which tube-to-tube heat transfer was prevented by cuts in common fins – was as much as 23 %. The level of capacity degradation was affected by air volumetric flow rate