Minimization of total cost, including technoeconomic weight and lifetime considerations, while maximizing heat transfer rates of heat exchangers is a key objective in many thermal applications. Among the different heat exchanger types, shell and tube heat exchangers (STHEs) are particularly popular due to their versatility in operation over wide temperature and pressure ranges of common working fluids, their ease of maintenance, and high flow capacity. Commonly used design approaches for such heat exchangers tend to employ empirical design rules that do not guarantee optimal solutions. In this work, we utilize the Volume Averaging Theory (VAT) framework for characterizing a unit cell based on a set of important heat exchanger geometric parameters such as tube diameter, longitudinal pitch, transverse pitch and shell diameter. The design is a multi-pass shell and tube heat exchanger with cold, higher pressure supercritical CO~2~ flowing inside the tubes and hot, lower pressure supercritical CO~2~ flowing on the shell side. Good chemical stability and high density at high temperatures, and the low critical point (7 MPa and 300 K) of CO~2~ makes supercritical CO~2~ a more attractive candidate fluid for operation in energy systems than other supercritical fluids. We divide the STHE into a series of individual segments and consider each one as a unit cell. VAT is a hierarchical modeling method in which the lower scale governing equations are the Navier-Stokes and thermal energy equations in the fluid and solid phases while the upper scale governing equations are the volume-averaged mass, momentum, and thermal energy transport equations. VAT abstracts the geometry into a porous medium representation that helps to reduce computation time and simplifies governing equations without compromising solution accuracy. Using experimental data from existing literature for external flow over a staggered bank of tubes, a multivariate regression analysis is conducted to develop correlations for the friction factor, *f*, and Nusselt number, *Nu*, for flow on the shell side of the heat exchanger. The temperature and flow fields in each unit cell of the heat exchanger are iteratively solved with the help of a custom computer code. Thermophysical properties of the working fluids such as density, viscosity, thermal conductivity, and enthalpy are updated during each iteration to obtain a more accurate solution for the temperature and flow field in the heat exchanger. A cost-based objective function is developed that predicts the effectiveness of the STHE and includes a wide range of technoeconomic factors. The code is executed through different ranges of the geometric parameters to obtain a technoeconomically optimal STHE design. 


Design Optimization of a Shell and Tube Heat Exchanger Using Volume Averaging Theory

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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