報告書番号

M05021

タイトル（和文）

CO2ヒートポンプ用熱交換器の高性能化に関する検討 -第二報：平滑管内平均蒸発熱伝達率に及ぼす熱流束の影響-

タイトル（英文）

Study on high performance heat exchanger for carbon dioxide heat pumps.- 2nd report : Impact of heat flux on evaporating heat transfer coefficient of carbon dioxide -

概要 （図表や脚注は「報告書全文」に掲載しております）

自然冷媒CO2ヒートポンプ給湯機（通称エコキュート）を小型化したり寒冷地対応したりするために重要な蒸発熱伝達率の計測について、住友軽金属工業と当所は継続的に取り組んできた。本研究では、高純度（99.999%）CO2を用いて、外径6mm（肉厚0.4mm）長さ3m、4m、5mの平滑銅管を対象とし、蒸発圧力、平均質量速度をパラメータとして平均熱伝達率の計測を行った。その結果、平均熱伝達率に熱流束の影響が強いことがわかった。これは、核沸騰の効果が強く出たためと推察する。

概要 （英文）

The CO2 heat pump water heater "ECO CUTE" which was commercialized in 2001 has a high potential for energy conservation and greenhouse abatement. Shipments in fiscal 2004 expanded to 120,000 units. In order to encourage the broader use of "ECO CUTE" (the target of the government is 5.2 million accumulations by fiscal year 2010), the government announced the continuation of a subsidy system and the commencement of new development projects. The main issues of the project are "measures for cold regions" and "downsizing". The most important element apparatus is always the evaporator. In this paper, an experimental study has been conducted to measure the pure CO2 flow boiling heat transfer coefficient (99.999% purity, without oil) in a horizontal smooth tube (outer diameter 6 mm, thickness 0.4 mm). In a previous report, the measured average heat transfer coefficient had a peak value at a certain mass velocity or a heat flux, but which influence strongly affected the result was not understood. In order to distinguish the influence of mass velocity and that of heat flux to the heat transfer coefficient, the tube length is varied to 3.0 m and 5.0 m (in the previous report, the length was 4.0m). The test conditions were: CO2 mass velocity from about 150 to about 700 kg / (m2s) (heat flux from about 10 to about 40 kW/m2), quality at inlet of test section is 0.17, CO2 super heat at outlet of test section is 5 K and saturation temperature of CO2 ranges from 0 to 10 oC. As a result, it has been understood that heat flux has a greater influence on the heat transfer coefficient.

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