Abstract Laser-induced fluorescence (LIF) thermography has emerged as a technique for measurement of two-dimensional temperature fields with minimal intrusion. This technique has been applied in the past to convective heat transfer problems involving liquids and can provide valuable local heat transfer information in spatially non-uniform convective flows. It has also been used in high-temperature gaseous flows, including combustion chambers and shock tubes. However, LIF has scarcely been used in low-temperature convective heat transfer applications involving gases, where its sensitivity is often limited. Low temperature here refers to the range from room temperature to 100–200 °C, where most other gaseous LIF studies are classified high temperature with maxima exceeding 250 °C. This study investigates the use of LIF thermography for low-temperature gaseous convective flows, with temperatures near ambient conditions. It demonstrates the utility of LIF thermography for a wider range of low-temperature engineering applications. The fluorescence was excited with a 266 nm laser sheet using a custom-built apparatus. The relationship between toluene fluorescence intensity and temperature was validated in the temperature range 20–60 °C, which is substantially lower than in previous studies to date. The same setup was used to measure the temperature field that develops during free and forced convection around a heated cylinder. The thermographic performance of anisole, which has been used in relatively few LIF studies to date, was also investigated. Graphic abstract Sample images of toluene fluorescence intensity $$I\left( {x,y} \right)$$ I x , y surrounding a heated cylinder for (a) $$\dot{Q} = 2.15$$ Q ˙ = 2.15 W ( $${\text{Ra}} = 15,200$$ Ra = 15 , 200 ) and (b) $$\dot{Q} = 0$$ Q ˙ = 0 W and $$T\left( {x,y} \right) = T_{{{\text{ref}}}} = 21$$ T x , y = T ref = 21 °C. The dashed circle marks the position of the cylinder surface. Dividing image (a) by image (b) gives the (c) the normalized fluorescence intensity $$I^{*} \left( {x,y} \right) = I\left( {x,y,T} \right)/I\left( {x,y,T_{{{\text{ref}}}} } \right)$$ I ∗ x , y = I x , y , T / I x , y , T ref , from which the (d) temperature field $$T\left( {x,y} \right)$$ T x , y can be determined.

中文翻译：

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气体激光诱导荧光在低温对流传热研究中的应用

摘要 激光诱导荧光 (LIF) 热成像技术已成为一种以最小侵入测量二维温度场的技术。该技术过去已应用于涉及液体的对流热传递问题，并且可以在空间非均匀对流中提供有价值的局部热传递信息。它还被用于高温气流，包括燃烧室和冲击管。然而，LIF 几乎没有用于涉及气体的低温对流传热应用，其灵敏度通常有限。这里的低温是指从室温到 100–200 °C 的范围，大多数其他气态 LIF 研究都归类为高温，最大值超过 250 °C。本研究调查了 LIF 热成像在温度接近环境条件的低温气体对流中的应用。它展示了 LIF 热成像在更广泛的低温工程应用中的实用性。使用定制设备用 266 nm 激光片激发荧光。甲苯荧光强度与温度之间的关系在 20-60°C 的温度范围内得到验证，这大大低于迄今为止的先前研究。相同的设置用于测量在加热圆柱体周围的自由和强制对流期间形成的温度场。迄今为止，苯甲醚的热成像性能已用于相对较少的 LIF 研究，也进行了研究。图形摘要 甲苯荧光强度的样本图像 $$I\left( {x, y} \right)$$ I x , y 围绕加热圆柱体 (a) $$\dot{Q} = 2.15$$ Q ˙ = 2.15 W ( $${\text{Ra}} = 15,200$$ Ra = 15 , 200 ) and (b) $$\dot{Q} = 0$$ Q ˙ = 0 W and $$T\left( {x,y} \right) = T_{{{\text{ref} }}} = 21$$ T x , y = T ref = 21 °C。虚线圆圈标记了圆柱表面的位置。将图像 (a) 除以图像 (b) 给出 (c) 归一化荧光强度 $$I^{*} \left( {x,y} \right) = I\left( {x,y,T} \ right)/I\left( {x,y,T_{{{\text{ref}}}} } \right)$$ I ∗ x , y = I x , y , T / I x , y , T ref ，从中可以确定 (d) 温度场 $$T\left( {x,y} \right)$$ T x , y 。y = T ref = 21 °C。虚线圆圈标记了圆柱表面的位置。将图像 (a) 除以图像 (b) 给出 (c) 归一化荧光强度 $$I^{*} \left( {x,y} \right) = I\left( {x,y,T} \ right)/I\left( {x,y,T_{{{\text{ref}}}} } \right)$$ I ∗ x , y = I x , y , T / I x , y , T ref ，从中可以确定 (d) 温度场 $$T\left( {x,y} \right)$$ T x , y 。y = T ref = 21 °C。虚线圆圈标记了圆柱表面的位置。将图像 (a) 除以图像 (b) 给出 (c) 归一化荧光强度 $$I^{*} \left( {x,y} \right) = I\left( {x,y,T} \ right)/I\left( {x,y,T_{{{\text{ref}}}} } \right)$$ I ∗ x , y = I x , y , T / I x , y , T ref ，从中可以确定 (d) 温度场 $$T\left( {x,y} \right)$$ T x , y 。