Optimization of fluid-based heat-recovery systems

Abstract: This report aims to investigate how fluid-based heat-recovery systems for ventilation can be optimized. A high proportion of existing systems operate at lower efficiency than possible, and thus do not reach their full potential in terms of energy savings. The aim of this report has been to find out why, to identify which parameters affect the efficiency of such systems, and to develop a general methodology for optimization. As a method for execution, a literature study and field experiments were chosen. The results from the literature study showed that dimensioned efficiency, fluid flow in the circuit and degree of contamination of the system were important parameters that greatly affected performance. The field experiments largely confirmed this, but also showed that an implementation of the theoretically optimal fluid flow is not always beneficial to the performance, but higher flow should always be considered. The results also indicated a correlation between the fluid flow and the convective heat-transfer coefficient (U-value) in the heat exchangers. A methodology for optimization is presented in the discussion section. As a suggestion for further research, two possible directions are proposed - the potential of cleaning and the effect of the fluid flow.