Many engineering systems, including power plants, climate control, and engine cooling systems typically contain tubular heat exchangers. However, for most engineering problems, it is impractical to model individual fins and tubes of a heat exchanger core. In principle, heat exchanger cores introduce a pressure drop to the gas stream (also termed the primary fluid) and transfer heat to a second fluid, a coolant, referred to here as the auxiliary fluid.
In FLUENT, lumped-parameter models are used to account for the pressure loss and auxiliary fluid heat rejection. FLUENT provides two heat exchanger models: the simple-effectiveness-model and the number-of-transfer-units (NTU) model. The models can be used to compute auxiliary fluid inlet temperature for a fixed heat rejection or total heat rejection for a fixed auxiliary fluid inlet temperature. For the simple-effectiveness-model, the auxiliary fluid may be single-phase or two-phase.
The following sections contain information about the heat exchanger models: