The Effect of Transient Characteristics on Optimization of Fixed-Bed Regenerators

Abstract

Fixed-bed regenerators (FBRs) have high sensible effectiveness, making them an energy-efficient Air-to-Air Energy Recovery Exchanger (AAEE) to reduce the energy consumption for ventilation in buildings. FBRs operate by alternately storing and releasing heat in fixed bed exchangers, which results in outlet temperatures that vary with time during both heating and cooling periods. This variation in FBR's outlet temperature adds a new optimization variable that needs to be considered when designing FBRs. For example, in HVAC systems, Careful design is required to prevent large variations in FBR's outlet temperature (Temperature Swing (TS)), which might deteriorate occupant thermal comfort and introduce a variable load on the HVAC system. In this paper, a correlation for TS is developed as a function of FBR design parameters. FBRs optimization is performed considering TS as an additional objective to the traditional parameters of exchanger effectiveness, pressure drop, payback period, and mass. A selection procedure (decision making) is also integrated into the optimization process to select optimized FBRs from Pareto fronts. The results show that when TS is included as an additional objective to the optimization and selection process, the selected optimized FBRs have higher mass and effectiveness.