The main objective of Section 1.2 is to offer a fundamental, theoretical approach to formulating a mathematical framework for describing a heat exchanger’s operation. This framework will be considered in Section 1.3 and Section 1.4 in much more detail by establishing both analytical and numerical models.

Section 94 introduces mass and energy balances as basic thermodynamic tools for establishing the set of governing equations and describing the heat transfer process in a heat exchanger. In addition, some basic thermodynamics concepts will be reviewed.

Section 95 draws attention to the constitutive equations needed to formulate the relationships between the heat and mass transfer fluxes as well as the temperature gradients’ driving potentials. A number of dimensionless quantities needed for representing heat and mass transfer correlations will be introduced.

Section 96 provides primarily empirical and/or scaling information regarding the transfer coefficients, including both heat and momentum.

In Section 97, mass and energy balance equations are applied. A heat exchanger is considered as an open, adiabatic steady state system featuring little impact of kinetic and potential energy change contributions. Definitions of basic heat exchanger performance metrics are included, such as heat exchanger effectiveness as a function of the heat exchanger thermal size and heat capacity rate ratio.