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

Abstract

Experiments were used in conjunction with a compressible flow model to investigate the temperature recovery phenomenon along a blowdown stack during a highpressure natural gas pipeline blowdown. The test rig involved instrumented 2 in. blowdown stacks mounted on a fullbore valve. Stacks with two wall thicknesses and stagnation pressures of approximately 3000 kPaa and 5600 kPag were tested, giving a total of four test cases. Using the compressible flow model, which was calibrated using static pressure measurements, the stackgas temperature was calculated to range from −38 آ°C to −18 آ°C for the four test cases. The respective stack wall temperatures were measured to range between −13 آ°C and 0 آ°C; thus, the temperature recovery ranged between 18 آ°C and 26 آ°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 correlationcalculated recovery factor was found to be negative for all five correlations.