Abstract
Some technical methods were studied for the purpose of reducing the non-epuilibrium temperature difference in the flash evaporation process, and a device reducing the pressure by varying the orifice area was designed therefor. This device was installed in a test plant of five-stage flash distillation, and non-equilibrium temperature defferences in the flash evaporation process were measured by using city water.
The results of the study indicated that the rate of evaporation could be increased and the nonequilibrium temperature difference (NTD) could be reduced by making the orifice area larger than the one calculated from the characteristic formula of pressure loss for single phase flow on the same coditions. The following was the emprical equation obtained from the study:
In case the evaporating conditions of a commercial plant were applied to the above equation, the non-equilibrium temperature difference droved to be greater than the calculated values from the AMF's equation for NTD. Therefore, a further study would be necessary on the possibility of scale up by use of the above equation, but the new pressure reducing device was designed in this study.
