SIMULATION OF KETTLE REBOILER

Abstract

The present investigation pertains on the work of simulation of kettle reboiler. Basically it deals with the development of mathematical model for simulation of a kettle reboiler thereafter test its applicability for the simulation of kettle reboiler. Further it describe the effect of operating and geometric parameters namely, operating pressure, temperature gradient, tube length to diameter ratio and tube pitch to diameter ratio on the recirculation rate, shell side heat transfer coefficient and heat flux. Based on the concept of internal recirculation in the shell, which consists of various numbers of tube row in a rectangular bundle a mathematical model has been developed. Also in this model it was assumed that the recirculated liquid distributed with an equal amount on each tube row. This model provides the total recirculation rate as well as tube row to tube row heat transfer coefficient. Further the mathematical model has been solved by using pressure balance, mass balance equation and correlations of heat transfer coefficient given by Palen et. al. [14,15,16] and Leong & Cornwall [9]. As a result this model gives the value of recirculation rate and heat transfer coefficient for each tube row number. Then shell side heat transfer coefficient has been calculated by weighted average method and there by heat flux. The result due to the model have been found to agree well with the standard Heat ii Transfer Research Inc. (HTRI) data [9] for the boiling of n-Pentane at 690 kPa pressure with in a maximum error of +20%. The effect of operating and geometrical variable namely, operating pressure, temperature gradient, tube length to diameter ratio and tube pitch to diameter ratio have been evaluated on the recirculation rate, shell side heat transfer coefficient and heat flux calculated by the mathematical model developed. This study shows that the recirculation rate in kettle reboiler has been found to decrease with increase in temperature gradient and tube length to diameter ratio while it increases with the operating pressure and tube pitch to diameter ratio. The shell side heat transfer coefficient increases with the temperature gradient, operating pressure and tube pitch to diameter ratio but shows reverse trend for the tube length to diameter ratio. While the variation in the heat flux has not been very much to be considered. From the study of above system it was concluded that it is sensitive towards operating variable rather then geometric variable. This is due to variation of recirculation rate with these parameters.