Investigation effects of roughness in wet steam flow with Buckingham Pi-theorem

Abstract

Since turbine blades and supersonic nozzles expand under unique conditions, vapor may become super-cooled and afterward wet steam. Wetness fraction (WF) and Droplet radius (r) are two remarkably significant variables in designing and operating wet steam devices. A factor affecting the efficiency of the devices is the growth of roughness of surfaces. The friction factor is increased by the collision of droplets over surfaces. So far, many costly and complicated methods have been applied to design wet steam devices considering roughness. In this article, an innovatory method that is founded on Buckingham Pi-theorem is suggested to predict r and WF regarding roughness merely with the help of dry vapor data. A dimensionless droplet radius (DDR) can be defined as a function of friction factor Wet Steam (FWS), which is a dimensionless parameter. First, FWS, DDR, and WF are achieved based on the analytical modeling results. After that, two regression equations are suggested to calculate WF and DDR versus FWS. Eventually, a considerably good agreement is achieved through analytical modeling. One concludes that the present study can be considered an appropriate and useful technique for modeling the real operation condition in wet steam devices.