Experimental analysis of heat transfer coefficients in phosphoric acid concentration process

Abstract

In typical heat exchanger design methods it is generally assumed that the overall heat transfer coefficient is constant and uniform; however, the heat transfer coefficients on the hot and cold sides of the heat exchanger may vary with times. In this work, a large number of operating parameters were collected for three types of heat exchangers, namely stainless-steel tubular and two graphite blocks from different suppliers (A and B), in an industrial phosphoric acid concentration unit over a period of two years. An experimental study performed to determine both the overall heat transfer coefficients in the clean state and the overall heat transfer coefficients at time t. A statistical approach was proposed to determine the overall heat transfer coefficients in the clean state as well as the retain cycles. The overall heat transfer coefficients were evaluated at different times. Our results show that the overall heat transfer coefficients decreased exponentially with the time and reach a minimum value ranging between 1419 to 2406 W m−2 K−1 according to the type of heat exchanger.