Characteristics of Heat Transfer Control on Offset-type Turbulent Impinging Jet

热能应该保存到下一代。偏置冲击射流是改善和强化局部传热传质的一种典型方法。在实际应用中，喷嘴在相对狭窄的受限壁空间中的姿态是一个重要因素，包括设备的紧凑性。1992年，以空气为工质，对倾斜湍流冲击射流的传热特性进行了实验研究。喷嘴直径为30 mm，喷嘴和冲击表面之间的距离也为30 mm。限制壁设置在与喷嘴相同的高度处。倾斜角度为45 °、60 °和90 °。撞击部分由透明丙烯酸板、热敏液晶片和厚度为20 μ m的不锈钢箔组成。在CCD摄像机的透镜前依次安装三种滤光片。热敏液体的彩色图像 ...更多信息 晶体被转换成电信号。一个像素的大小为0.5- 1 mm的正方形。校正了颜色与温度的关系，确定了准确度和分辨率。在一定温度下，液晶的散射反射光被滤光片分成红、绿色、蓝三种颜色分量。在每个像素处获得每个分量的亮度作为图像数据。温度的估算采用包含相对亮度的回归方程。通过求解加热段的三维热传导方程，利用加热段的详细温度分布对局部热流进行局部补偿。结果表明，局部努塞尔数出现了峰移和平台。在低雷诺数时，局部热流的影响是显著的，约为均匀热流的6- 17%.1993年，我们用热风速仪对斜向湍流冲击射流的流动特性进行了实验研究。在不加热的条件下测量了横截面上的速度和湍流强度。将探头逆着流动设置并平行于冲击表面。结果表明，喷嘴喷出的射流沿周围静止流体滚下，冲击平板表面。冲击面附近的湍流在小流区发生滚降和放大，促进了局部换热。这些流动参数（速度和脉动强度）的梯度似乎与其绝对值一样影响局部换热强化。研究结果表明，影响换热效果的速度脉动功率谱的上级频率在80 ~ 300 Hz之间，且与雷诺数有关，为实际装置的应用提供了基础数据。少

Thermal energy should be saved to the next generation. Offset-type impinging jet is a representative method to improve and augment the local heat transfer or mass transfer. In practical applications, the attitude of the nozzle in comparatively narrow space with confined wall is an important factor including the compactness of the facility.In 1992, the heat transfer characteristics of an oblique turbulent impinging jet were performed experimetaly by using air as a working fluid. The nozzle diameter was 30 mm and also the distance between the nozzle and the impingement surface 30 mm. The confined wall was set at the same level of the nozzle. The inclined angle was 45ﾟ, 60ﾟ and 90ﾟ. The impingement section was composed of an transparent acrylic plate, the thermosensitive liquid crystal sheet and the stainless steel foil whose thickness was 20 mu m. Three kinds of optical filters were mounted one after another in front of the lens of the CCD camera. The color image of thermosensitive liqui … More d crystal was converted into an electric signal. The size of one pixel was 0.5-1mm square. The relationship between color and temperature was calibrated to determine the accuary and resolution. The scatterd reflected light from the liquid crystal at a given temperature was divided into three components (Red, Green, Blue) of color by optical filters. The brightness of each component was obtained at each pixel as the image data. The temperature was estimated by the regression equation including the relative brightness. The local heat flux was compensated locally by using the detailed temperature distribution and solving the three-dimensional thermal conduction equation in the heated section. According to the results, the local Nusselt number showed the peak shift and the plateau. The effect of the local heat flux is remarkable at low Reynolds number and amounts to 6-17% of uniform flux.In 1993, the flow characteristics of an oblique turbulent impinging jet were carried out by using a thermoanemometer. The velocity and turbulent intensity across the section were measured in unheated condition. The probe was set against the flow and parallel to the impingement surface. According to the results, the jet from the nozzle rolled down the sorrounding stationary fluid and impinged the flat surface. The rolling down of the flow and the amplification of turbulence near the impingement surface were performed at the minor flow region and promoted the local heat transfer. The gradient of these flow parameters (velocity and fluctuation intensity) seem to affect the local heat transfer enhancement as their absolute vaues do. The superior frequency in power spectrum of velocity fluctuation affecting heat transfer improvement was from 80 to 300 Hz and depended on Reynolds number.These results will be applied in the practical facility as the basic data. Less