Effects of high fractional noncondensable gas on condensation in the dewvaporation desalination process

A shell and tube condenser column was designed and constructed to evaluate the performances of the steam condensation process with high fractional noncondesable gas. The process is related to steam-air mixed gas condensation in an annulus around a vertical copper tube with 10 mm outside diameter. In order to investigate the effect of condensing column length on overall heat transfer coefficient, the columns with various length of 2.5 m, 2.0 m, 1.6 m, 1.3 m and 1.0 m were tested with steam-air mixed gas, respectively. The test variables were as follows: mixed gas inlet temperatures range from 92 to 68°C; inlet air mass fraction from 34 to 81%; inlet mixed gas velocity from 1.08 to 10.80 m/s and mixture inlet Reynolds number from 500 to 5000. The results show that the overall heat transfer coefficient decreases as the condensing column length increases under the same mixed gas inlet Reynolds number. The overall heat transfer coefficient varied from 350 to 3000 W/m2°C, which is high enough for steam condensation in the presence of a high fractional noncondensable gas. It has promising application in dewvaporation desalination process at pilot scale. The correlation of steam condensing heat transfer coefficient in the presence of a high fractional noncondensable gas was developed along condensing column height.