Abstract This paper presents an experimental setup for the study of the natural convective heat loss characteristics of a cylindrical cavity with/without a quartz window. The thermal performance such as wall temperature and heat loss of two types of cavity receivers are studied by changing the tilt angles and heated states of the walls, then the effect of quartz window on the heat loss of the cavity is highlighted. The average temperature of cavity with a quartz window is respectively 68.61 °C, 79.36 °C, 48.22 °C higher than same cases without a quartz window (corresponding tilt angle is −90°, −30° and 45°). The temperature difference is within 10 °C for quartz window cavity and 40 °C for no quartz window cavity when q = 700 W/m2 and all surfaces are heated. More than 70% cases occur that the natural convective heat loss of no quartz window cavity is greater than that of the quartz window cavity. The experimental results show that the quartz window can significantly increase the operating temperature of the cavity and weaken the influence of tilt angle. The quartz window plays an important role in the balance of cavity temperature and reduction of natural convective heat loss. The empirical correlations of predicting the radiant and natural convective Nusselt numbers of quartz window cavity considering tilt angle and heat flux have also been obtained.

中文翻译：

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带/不带石英窗圆柱腔自然对流热损失的实验研究

摘要 本文提出了一种实验装置，用于研究带/不带石英窗的圆柱形空腔的自然对流热损失特性。通过改变壁的倾斜角度和受热状态，研究了两种腔体接收器的壁温和热损失等热性能，突出了石英窗对腔体热损失的影响。带石英窗的腔体平均温度分别比不带石英窗的情况（对应的倾斜角为-90°、-30°和45°）高68.61°C、79.36°C、48.22°C。当 q = 700 W/m2 且所有表面都被加热时，石英窗腔的温差在 10 °C 以内，无石英窗腔的温差在 40 °C 以内。70%以上的情况是无石英窗腔的自然对流热损失大于有石英窗腔的自然对流热损失。实验结果表明，石英窗可以显着提高腔体的工作温度，减弱倾斜角的影响。石英窗在平衡腔体温度和减少自然对流热损失方面起着重要作用。还得到了考虑倾斜角和热通量预测石英窗腔辐射和自然对流努塞尔数的经验关系式。石英窗在平衡腔体温度和减少自然对流热损失方面起着重要作用。还得到了考虑倾斜角和热通量预测石英窗腔辐射和自然对流努塞尔数的经验关系式。石英窗在平衡腔体温度和减少自然对流热损失方面起着重要作用。还得到了考虑倾斜角和热通量预测石英窗腔辐射和自然对流努塞尔数的经验关系式。