Describes research to determine the effect of varying chilled and condenser water flows on centrifugal chiller efficiency. Three method were used - 1) theoretical heat transfer equations were examined to assess the effect of variable flow on vessel heat transfer, 2) extensive packaged chiller computer modelling examined a variety of flow and load conditions and 3) a chiller was run on an ARI certified test stand under varying conditions to record data, correlate results with computer studies and determine if any unstable operating or control situations would occur. Finds no significant difference in a chiller's coefficient of performance when operating at full evaporator flow or at a flow reduced equal to the percent reduction in load. Calculated pressure drops were proportional to flow to the 1.8 power. Test stand operation correlated with the modelling results within ARI tolerances. Instability in evaporator performance occurred at a tube velocity of less than 0.61 m/s (2 ft/s). Condenser performance was normal at tube velocities as low as 0.305 m/s (1 ft/s). The testing was done on internally rifled tubes.

KEYWORDS: year 1996, Chillers, water flow, flow rate, efficiency, performance, research, testing, calculating, heat flow