Improvement of heat transfer performance in gas-cooler for CO2 heat pump water heater

Y. Matsuo, M. Ichihara, S. Koyama, K. Machida

    研究成果: Chapter in Book/Report/Conference proceedingConference contribution

    抄録

    Recently, CO2 heat pump water heaters have already been developed and commercialized from the viewpoint of global environmental protection and energy-saving. However, there are still some problems to be solved, and one of the major problems is to improve the heat transfer performance of water flow passage in the gas-cooler. This is because the water flow is laminar. Generally, to enhance the heat transfer performance is difficult in laminar flow. However, dimpling and/or twisting heat transfer tubes etc. are considered to be effective because the water flow is disturbed. In the present study, two kinds of inner tube bundles are tested to clarify the effects of the tube forms on the heat transfer performance at the CO2 flow passage in the gas-cooler experimentally. Pressure drops of the CO 2 flow passage in gas cooler are also evaluated. Tested inner tube bundles made of copper are as follows: (1) a pair of twisted smooth tubes (TS), and (2) a pair of twisted dimple tubes (TD). These inner tube bundles are inserted into a 10.8 mm ID outer tube made of copper, then tubes-in-tube heat exchanger is assembled. The heat transfer coefficients and the pressure drop of CO2 are measured in the following ranges: pressure range is 8 to 10 MPa, mass flow rate range of 19.2 to 34.6 kg/h, and CO2 inlet temperature range of 20 to 70°C. It is found that the heat transfer performance in the CO2 flow passages of both the pair of twisted dimple tubes and the pair of twisted smooth tubes are nearly identical. However, the pressure drop in the CO2 flow passage of the pair of twisted dimple tubes is higher than that of the pair of twisted smooth tubes.

    本文言語英語
    ホスト出版物のタイトル6th Asian Conference on Refrigeration and Air Conditioning, ACRA 2012
    出版社Chinese Association of Refrigeration (CAR)
    ページ726-731
    ページ数6
    ISBN(印刷版)9781632660152
    出版ステータス出版済み - 2012
    イベント6th Asian Conference on Refrigeration and Air Conditioning, ACRA 2012 - Xi'an, 中国
    継続期間: 8 26 20128 28 2012

    出版物シリーズ

    名前6th Asian Conference on Refrigeration and Air Conditioning, ACRA 2012

    その他

    その他6th Asian Conference on Refrigeration and Air Conditioning, ACRA 2012
    Country中国
    CityXi'an
    Period8/26/128/28/12

    All Science Journal Classification (ASJC) codes

    • Electrical and Electronic Engineering

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