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次世代冷媒の流下液膜蒸発の熱伝達と流動特性に関する基礎研究

新一代制冷剂降膜蒸发传热及流动特性基础研究

基本信息

批准号：
21K04497
负责人：
地下大輔
金额：
$ 2.66万
依托单位：
Tokyo University of Marine Science and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2021
资助国家：
日本
起止时间：
2021-04-01 至 2024-03-31
项目状态：
已结题

项目摘要

満液式蒸発器に比べて冷媒使用量の削減が期待でき，低熱負荷条件でも優れた蒸発熱伝達特性が期待できる流下液膜式蒸発器において、冷媒の熱伝達および流動特性は冷媒流量，熱流束，冷媒物性等によって大きく変化する．流下液膜式蒸発器の熱設計のためには冷媒の熱伝達に及ぼす冷媒流量，熱流束，冷媒物性の影響を明らかにするとともに，熱伝達特性を高精度に予測する手法が必要となる．本研究では流下液膜の流動様相の可視化および伝熱実験により，環境負荷の小さい次世代冷媒の流下液膜蒸発の熱伝達および流動特性の実験的解明を目指す．2022年度は，地球温暖化係数の小さいHFO1234ze(E)を主とする2成分混合冷媒を対象に，水平管外を流下する液膜の蒸発流動様相の観察を行うとともに，熱伝達特性に及ぼす冷媒流量，熱流束の影響について明らかにした．混合冷媒の熱伝達率は，熱流束の増加に伴い気泡の発泡点密度が増加し，純冷媒と同様に増大した．露点と沸点の異なる混合冷媒の熱伝達率は，熱流束が高い場合には純冷媒に比べて低い値を示したが，熱流束が低い場合には純冷媒と同等あるいはわずかに高い値を示した．さらに，気液界面の表面波，気泡の生成・崩壊，液膜の消失を伴う乾き部の発生の様子を観察可能な垂直平面を流下する液膜流動様相の可視化および伝熱評価装置を製作し，HFO1234ze(E)の液膜流動様相の可視化および熱伝達特性に及ぼす冷媒流量，熱流束の影響について明らかにした．高熱流束条件では気泡サイズが増大し熱伝達率が増大するものの，冷媒流量が小さい場合には乾き部が発生し熱伝達率は低下した．

The reduction of Freon consumption in liquid evaporator is expected. The heat transfer characteristics of Freon are expected to be optimized under low heat load conditions. The heat transfer characteristics of Freon and the flow characteristics of Freon flow rate, heat flux and Freon properties are expected to be optimized. The thermal design of a downflow liquid film evaporator requires a method for predicting Freon heat transfer and Freon flux, heat flux, and Freon physical properties with high accuracy. This study aims to clarify the visualization and heat transfer behavior of the flowing liquid film, and to clarify the heat transfer behavior and flow behavior of the flowing liquid film in the next generation of Freon in the environment. In 2022, the temperature of the earth was reduced, and HFO1234ze(E) was the main component of the mixture of Freon and the observation of the flowing behavior of the flowing liquid film in the horizontal pipe. Heat transfer characteristics and Freon flux, heat flux and influence of heat flux. The heat transfer rate of mixed freon increases with the increase of heat flux, and the bubble point density increases with the increase of pure freon. The heat transfer rate of mixed freon with different boiling points of dew point is higher than that of pure freon in case of high temperature, and that of pure freon in case of low temperature. In addition, surface wave of gas-liquid interface, bubble generation and collapse, disappearance of liquid film, generation of dry part, visualization of liquid film flow phase, visualization of liquid film flow phase and thermal transfer characteristics of HFO1234ze(E), and influence of Freon flux and heat beam were observed. Under high heat flux conditions, the heat transfer rate increases and the freon flow rate decreases.