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International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)


Shouya Okada
Mie University, Kurimamachiya-cho 1577, Tsu-city, Mie 514-8507, Japan

Yuki Nakao
Mie University, Kurimamachiya-cho 1577, Tsu-city, Mie 514-8507, Japan

Masafumi Hirota
Department of Micro-Nano Systems Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603; Department of Mechanical Engineering, Mie University, Kurimamachiya-cho 1577, Tsu-city 514-850

DOI: 10.1615/IHTC16.her.022935
pages 4773-4780

MOTS CLÉS: Heat exchanger, Two-phase/Multiphase flow, Flow distribution


Parallel-flow type heat exchangers, which consist of dividing/combining headers and multiple branch tubes, have advantages of low thermal resistance and compactness. In applying them to evaporators, however, maldistributions of gas and liquid from the dividing header to branch tubes occur quite often and thermal performance is deteriorated. Therefore, improvement of the uniformity of gas-liquid distributions to branch tubes is a key issue to bring out the intrinsic performance of parallel-flow type evaporators. As one of the methods to improve the distribution uniformity, the refrigerant-supplying method through a pipe with multiple outlet holes installed in the dividing header has been investigated. To the authors' knowledge, however, specifications of tested pipes are limited, and flow characteristics in the channel are not fully clarified yet. In this study, we examine experimentally the effect of the multi-hole distributing pipe on refrigerant (R-134a) gas-liquid distributions in the multi-pass channel. The test channel has a horizontal header and 10 vertical upward microchannel branch tubes. We have tested four distributing pipes with different outlet-hole specifications and installation orientations. We have observed visually the flow in the header and measured amounts of gas and liquid distributed to branch tubes. By comparing these results with those measured in the standard channel, we have evaluated the performance of multi-hole distributing pipes.

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