We improve the usefulness of small (diameter < 10 mm) critical flow venturis (CFVs) as transfer standards for gas flow by measuring and explaining how their discharge coefficients depend on the temperature T of their environment. At Reynolds numbers Re < 2.5 × 10⁵ (e.g., a 2 mm diameter throat; inlet air at 1 MPa), CFVs exhibit sensitivity to the environmental temperature of approximately 0.02 % K⁻¹ due to biased measurements of the stagnation temperature T₀ (temperature “sampling” error) and from ignoring the low-density, annular, thermal boundary layer generated by heat transfer from the CFV's body to the gas flowing through the CFV. To reduce temperature sampling errors, we used a non-metallic approach pipe and a temperature sensor with a low stem-conduction error. To correct for thermal boundary layer effects on the flow, we used Geropp's functional form: $C_{\text{T}}=1+K_{\text{T}}{\mathrm{Re}}^{-1/2}\left[\Delta T/T_0\right]$ where $\Delta T$ is the difference between the CFV's inner wall temperature and the stagnation temperature. For CFVs made of stainless steel and copper with diameters of d = 0.56 mm, 1.1 mm, and 3.2 mm we measured $K_{\text{T}}$ ≈ −7 while theoretical predictions of $K_{\text{T}}$ by Geropp and Ding et al. are −1.7 and −3.845 respectively. Introducing the correction for room temperature changes ($C_{\text{T}}$) measured in this work, reduces the room temperature sensitivity of the flow measured with the 0.56 mm diameter CFVs from 0.02 % K⁻¹ to less than 0.003 % K⁻¹. Smaller, but significant, improvements are achieved with larger CFVs.

我们通过测量和解释小（直径 < 10 毫米）临界流量文丘里管 (CFV) 作为气流传输标准的有用性，通过测量和解释它们的排放系数如何取决于其环境的温度T。在雷诺数Re  < 2.5 × 10 ⁵（例如，直径为 2 mm 的喉部；入口空气压力为 1 MPa）时，由于停滞温度T _{0 的}偏差测量，CFV 对环境温度表现出大约 0.02 % K ^{-1 的}敏感性（温度“采样”错误）和忽略低密度、环形、热边界层是由从 CFV 的主体到流经 CFV 的气体的热传递产生的。为了减少温度采样误差，我们使用了非金属进样管和具有低杆传导误差的温度传感器。为了校正热边界层对流动的影响，我们使用了 Geropp 的函数形式：$C_{\text{吨}}=1+{钾}_{\text{吨}}{\mathrm{关于}}^{-1/2}\left[\Delta 吨/{吨}_0\right]$ 在哪里 $\Delta 吨$是 CFV 的内壁温度和停滞温度之间的差值。对于由不锈钢和铜制成的直径为d  = 0.56 mm、1.1 mm 和 3.2 mm 的CFV ，我们测量了${钾}_{\text{吨}}$ ≈ −7 而理论预测 ${钾}_{\text{吨}}$由 Geropp 和 Ding 等人撰写。分别为 -1.7 和 -3.845。引入对室温变化的校正（$C_{\text{吨}}$) 在这项工作中测量，将使用 0.56 毫米直径 CFV 测量的流量的室温敏感性从 0.02 % K ^{-1 降低}到小于 0.003 % K ^-1。较大的 CFV 实现了较小但显着的改进。