Modeling and simulation of a shell-and-tube heat exchanger for Organic Rankine Cycle systems with double-segmental baffles by adapting the Bell-Delaware method

In respect of an efficient design of Organic Rankine Cycle (ORC) power plants, the heat exchange equipment plays an important role. Shell-and-tube heat exchangers are widely used in such energy conversion systems. The TEMA (Tubular Exchanger Manufacturers Association) E shell type with single-segmental baffles is a relatively simple and the most common design. For this configuration the shell-side heat transfer coefficient is in general determined by the Bell-Delaware method. However, in case of applications with low mean temperature differences like geothermal ORC systems, more advanced flow configurations are applied. In this work a TEMA NFN shell-and-tube heat exchanger with double-segmental baffles is analyzed for single-phase flow. For this design, the standard version of the Bell-Delaware method is not applicable. In this context, the Taborek version of the Bell-Delaware method is adapted to the specific heat exchanger design by adjusting the calculation methods for the main geometrical parameters like cross flow area, leakage areas and effective number of tubes in the overlapping region. The entire heat exchanger is simulated in DYMOLA 2015 FD01. Thereafter, the obtained temperature profiles are validated by real power plant data and deviate from operational data by up to −1.14 %. Subsequently, a novel correlation for an enhancement factor Jx is developed. Due to the application to other shell-and-tube heat exchangers with double-segmental baffles, high accuracy is achieved. In addition, a heat exchanger baffle section is simulated in ANSYS FLUENT 15.0 in order to validate locally the novel adaption of the Taborek version of the Bell-Delaware method (main approach) by CFD simulations. The obtained heat transfer coefficients show a sufficient agreement.