风冷无油涡旋空气压缩机换热计算研究

Calculation of Heat Transfer in Wind-Cooling Oil-Free Scroll Air Compressor

为了对风冷无油涡旋空气压缩机换热过程进行研究,首先测量了静盘换热区域多个位置的温度,温度沿展角和高度方向总体上呈线性变化,受冷却风的影响,线性分布有所波动,分别用全部温度数据线性拟合和用过内端温度点的线性拟合两种方式进行处理,计算结果表明,后者的排气温度计算值及变化趋势与测量结果更加吻合。把应用范围更广、精度更高的Gnielinski公式用于空气压缩过程换热计算,其中特征长度为涡旋齿内壁长度,计算结果与以往研究中常用的Dittus-Boelter公式基本完全一致,仅换热系数变化过程略有不同,对压缩过程气体温度和压力的变化过程进行了分析。

Here, we analytically addressed the heat transfer of wind-cooling, oil-free scroll air compressor. First, the temperatures at sampling points in the heat-exchange zone of the fixed scroll were measured with Pt100 sensors, and the linear dependence of temperature on the scroll height and involute spiral angle was evaluated, with cooling wind as a per- turbation along involute angle. Next, the temperature distributions along the scroll height and involute angle were derived by least square data fitting, emphasizing the temperature at scroll＇ s inner-end. Finally, the heat transfer of compressed air was approximated and simulated with Gnielinski and Dittus-Boeher formulae, respectively. When it comes to better agree- ment of the simulated and measured temperatures of discharged-air, the temperature at scroll＇s end has a major impact. Moreover, the two formulae gave almost the same results, except a small difference in heat-transfer coefficient. The time- evolution of temperature and pressure in air-compression was also tentatively discussed.