Cooling Characteristics of Hot Surface by Air-Water Mixture

气水混合物热表面冷却特性

基本信息

批准号：
61460107
负责人：
ITO Takehiro
金额：
$ 4.42万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-61460107/
关键词：
mist cooling fog cooling evaporation of liquid droplet boiling air-water mixture controlled cooling 強制対流ラミナーフロー冷却

项目摘要

Measurement of the flow characteristics of nozzles and the heat transfer experiment have been performed on fog cooling in the region of low mass velocity of water. Distance between the nozzle and the heat transfer surface was fixed at 520 [mm] throughout the experiments. The mass velocity of water lies in the range of W=0.02-0.14 [kg/m^2s], the droplet diameter d=15-36 [<micrn>m], the impinging velocity V=4-7.2 [m/s], and temperature of the surface 100-600 [゜C]. Theoretical analysis has been also carried out on the heat transfer in the region equivalent to film boiling with the aid of experimental data. Total heat flux by fog cooling is assumed to be expressed by the sum of radiation Q., forced convection by air qa and evaporation of the droplets q_w which are estimated independently. Heat flux by radiation can be calculated by q_e=<epsilon><alpha> (T_w^4-T ^4). The emissivity <epsilon> was determined by the experiment by air convection. Assuming that the air flow can be considered to be an axsymetric laminar stagnation flow, the expression of the heat flux q_a=5.4Pr^<0.4><lambda> a(D8vi<nu>D8(T_w-T_a) was obtained. For the heat flux by the evaporation of droplets, the model which the droplet is dragged by the air flow and moves in the radial direction was employed and the expression of q_w=2.15X10^3<lambda>_vW(T_w-T _<sat>) was obtained. In the analysis, it is assumed that each droplet floats on the vapor film without contact with the surface and the heat is transfered to the droplet only by conduction through the vapor film. It was made clear by the analysis that the heat flux by the droplet evaporation is proportional to the mass velocity of water, and inversely to d^<0.5> and V^<0.5>. The total heat flux calculated by this analysis agrees well with that by the experiment in the range of the surface temperature of 250-600 [゜C].

在低质量水速度的水域中，对喷嘴的流量特征和热传递实验的测量进行了测量。在整个实验中，喷嘴和传热表面之间的距离固定为520 [mm]。水的质量速度位于w = 0.02-0.14 [kg/m^2s]的范围内，液滴直径D = 15-36 [<micrn> m]，撞击速度v = 4-7.2 [m/s]，表面100-600 [゜c]的温度。理论分析也已经在相当于借助实验数据的区域的热传递上进行。假定通过雾气冷却的总热通量通过辐射Q的总和表示，通过QA强迫运输和蒸发液滴Q_W，这些Q_W是独立估计的。辐射的热通量可以通过q_e = <epsilon> <Alpha>计算（t_w ^4-t ^4）。发射率<epsilon>是通过空气建设实验确定的。假设空气流可以被认为是轴对称层状滞留流，则热通量q_a = 5.4pr^<0.4> <0.4> <lambda> a（d8vi <nu> d8（t_w-w-t_a）的表达是通过液滴的蒸发而驱动的。 q_w = 2.15x10^3 <lambda> _vw（t_w-t _ <SAT>）在分析中获得。成型为d^<0.5>和V^<0.5>。