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ACRC Technical Report 198PDF


Title:Refrigerant-Side Tradeoffs in Microchannel Evaporators
Author(s):Kulkarni, T.; Bullard, C.W.; Cho, K.
Subject(s):microchannel heat exchangers
Abstract:The present study examined design issues of microchannel evaporators associated with the flow maldistribution caused due to header pressure gradient. The effects of mass flow maldistribution on microchannel heat exchanger were quantified by using a single port simulation model. Longitudinal headers as currently used with microchannel condensers may not be suitable for the applications with microchannel evaporators. Mass flow maldistribution was investigated by using well-known pressure drop and heat transfer correlations for two-phase flow, selected after comparing with the results obtained by using different correlations. It was found that mass flow maldistribution cannot be controlled by changing either port/header diameter or the refrigerant state at the inlet to the port, but only by minimizing pressure gradients along header. At the same time the need to avoid phase separation in the header places a lower bound on mass flux. The dependence of heat exchanger capacity on the diameter and the length of the longitudinal and radial headers and was investigated in detail. Results demonstrated that the requirement for inertially dominated flow in the inlet header severely limits the set of feasible evaporator geometries. Accordingly, alternative concepts for header design were suggested.
Issue Date:2002-06
Publisher:Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Air Conditioning and Refrigeration Center TR-198
Genre:Technical Report
Sponsor:Air Conditioning and Refrigeration Project 124
Date Available in IDEALS:2009-06-04

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