Design Tradeoffs in Microchannel Heat Exchangers

Kulkarni, T.; Bullard, C.W.

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https://hdl.handle.net/2142/12159 Copy

Description

Title

Design Tradeoffs in Microchannel Heat Exchangers

Author(s)

• Kulkarni, T.
• Bullard, C.W.

Issue Date

2003-02

Keyword(s)

• microchannel heat exchangers
• heat exchangers

Abstract

The present work is based on theoretical and computational investigations into microchannel heat exchangers. Microchannel heat exchangers have long been used as condensers but concerns regarding refrigerant maldistribution have so far prevented their use as evaporators. The first part of the document is devoted to identifying causes of maldistribution and suggesting ways to reduce and eventually eliminate maldistribution. To reduce maldistribution caused due to header pressure gradient, short and fat radial headers were demonstrated to be better than longitudinal headers currently used in microchannel condensers. The second part describes a way to avoid the problem associated with distributing two-phase refrigerant: passive vapor bypass. Immediately downstream of the expansion device, two-phase refrigerant is separated into vapor which is bypassed directly to the suction line through an adiabatic tube and liquid which is distributed into the evaporator. Computer simulation models were developed to explore the feasibility of this concept for a residential air-conditioning application using both sub- and transcritical cycles. The last part of the document identified tradeoffs among the first cost, operating cost and compactness of microchannel heat exchangers. Variation of air-side parameters such as fin height, thickness and pitch were considered to identify a set of designs that have the lowest first cost and another having the highest energy efficiency. The report is divided into the above sections which can be read independently, in any order at the reader’s convenience.

Publisher

Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.

Series/Report Name or Number

Air Conditioning and Refrigeration Center TR-208

Type of Resource

text

Language

en

Permalink

http://hdl.handle.net/2142/12159

Sponsor(s)/Grant Number(s)

Air Conditioning and Refrigeration Project 124

Owning Collections