CO_2微细通道流动沸腾换热干涸特性

针对二氧化碳作为制冷剂在微细通道内两相流沸腾换热进行了实验与理论研究,采用红外成像观测与传热系数实验研究,定量与定性地分析了热通量2~35 k W·m-2,饱和温度-10~10℃工况时,内径为1、2、3 mm圆管内的传热系数。实验结果表明:当质量流率增加时干涸起始干度逐渐降低,当质量流率小于临界值时,干涸现象结束之后,传热系数随着质量流率增加基本维持不变,而当质量流率大于临界值时,干涸现象结束之后,随着质量流率增加传热系数相应增加;随着管径增加,干涸发生的质量流率越小,临界热通量越大,同时管径越小传热系数越高。

Characteristics of dryout for CO2 flow boiling heat transfer in mini-channels

Experimental and theoretical researches were conducted to get the two-phase flow boiling heat transfer characteristics of carbon dioxide as refrigerant in horizontal mini-channels. Based on infrared thermal imaging tests and experimental study on heat transfer coefficients, heat transfer coefficients of carbon dioxide were analyzed qualitatively and quantitatively under following experimental conditions: heat flux 2—35 kW·m^-2, saturation temperature -10—15℃, mini-channels inner diameter:1 mm, 2 mm or 3 mm. With the increase of mass flow rate, the value of vapor quality decreased gradually when dryout happened. When mass flow rate was below a critical value, heat transfer coefficient almost kept constant with the increase of mass flow rate after dryout. When mass flow rate was above the critical value, heat transfer coefficient gradually increased with the increase of mass flow rate after dryout. With the increase of tube diameter, mass flow rate decreased and the critical value of heat flux increased when dryout happened. With the decrease of tube diameter, coefficient of heat transfer increased.