🔥 Chapter 7: Sizing and Off-Design Behavior of Heat Exchangers

Beyond Simple Calculations

Building on Chapter 4, this chapter dives into sizing and off-design calculations for heat exchangers.

  • NTU Method Revisited:

    • Calculate UA product (overall exchange coefficient × surface area).
    • Pressure drop for single-phase and two-phase flows.

  • Heat Transfer Modeling:

    • Extended surfaces, Reynolds/Prandtl numbers, Nusselt correlations.
    • Two-phase exchange: Condensation and evaporation correlations.

  • Special Cases:

    • Nucleate boiling in steam generators (TechnoSteamGenerator class).
    • Multi-zone exchangers: Evaporators, condensers, and combined systems.

Practical Tips: From direct geometric calculations to experimental data identification, this chapter covers it all!

Abstract

This chapter explains how to model and configure heat exchangers for sizing and off-design calculations, complementing Chapter 4’s foundation for simple heat exchanger calculations in energy systems. While the NTU method provides the UA product (overall exchange coefficient × surface area), heat exchanger sizing requires separate evaluation of both terms through geometric configuration selection and heat transfer coefficient calculation. The chapter begins with NTU method fundamentals before addressing pressure drop calculations for single-phase flows (using friction coefficients and correlations) and two-phase flows. Heat transfer modeling covers extended surfaces, Reynolds and Prandtl number calculations, and Nusselt number correlations for diverse configurations including inside tubes, perpendicular flows, finned coils, and plate heat exchangers. Two-phase exchange receives extensive treatment with correlations for condensation and evaporation. Nucleate boiling in steam generators is addressed through the TechnoSteamGenerator class, implementing ONB detection, FDB identification, and pressure drop calculations. Multi-zone exchanger equations are detailed for evaporators, condensers, and combined systems. Geometric parameter estimation methods range from direct calculation using geometric data (hydraulic diameter, flow areas, plate exchangers, shell-and-tube) to identification from experimental data.