Measurements of the Stack Metal Temperature During a Natural Gas Blowdown Event Through a Full-Bore Blowdown Valve

Experiments were used in conjunction with a compressible flow model to investigate the temperature recovery phenomenon along a blowdown stack during a high-pressure natural gas pipeline blowdown. The test rig involved instrumented 2 in. blowdown stacks mounted on a full-bore valve. Stacks with two wall thicknesses and stagnation pressures of approximately 3000 kPa-a and 5600 kPa-g were tested, giving a total of four test cases. Using the compressible flow model, which was calibrated using static pressure measurements, the stack-gas temperature was calculated to range from −38 °C to −18 °C for the four test cases. The respective stack wall temperatures were measured to range between −13 °C and 0 °C; thus, the temperature recovery ranged between 18 °C and 26 °C. Empirical correlations available in the literature, which were developed for aeronautical applications, were tested against the experimental results. Poor agreement was found between the measured temperature recovery factor and that predicted by five empirical correlations: the coefficient of determination (R²) between the measured and correlation-calculated recovery factor was found to be negative for all five correlations.