An Experimental Study of Pressure Gradients for Flow of Boiling Water in Vertical Round Ducts (Part 4)

The present report contains the experimental results from the fourth and last phase of an investigation concerning frictional pressure gradients for flow of boiling water in vertical channels. The test section for this phase consisted of an electric heated stainless steel tube of 3120 mm length and 12.99 mm inner diameter. Data were obtained for pressures between 6 and 10 ata, steam qualities between 0 and 0.70, mass flow rates between 0.04 and 0.164 kg/sec. Only one value of 65 W/cm2 were used for the surface heat flux. The results are in excellent agreement with our earlier data for flow in 9. 93, 7. 76 and 3. 94 mm inner diameter ducts previously presented, and our conclusions given in those reports have been verified. On the basis of the measured pressure gradients, the following empirical equation has been established for engineering use. χ2 = 1 + 2600*(x/p)0.96 This equation correlates our data within an accuracy of ± 15 per cent. Considering the data from all four ducts investigated, we have found that the following equation correlates the data with a discrepancy less than ± 20 per cent: χ2 = 1 + 2500*(x/p)0.96 and we conclude that for engineering purposes, the effect of diameter is of no significance