Effect of Flow Arrangement On Energy Efficiency Index

Abstract

An energy efficiency index (EEI=k/∇pn) was proposed by Zhang et al to rate the energy saving performance of plate heat exchanger, it was also considered to be independent on the heat transfer area and weakly correlated or not correlated with the flow velocity. However, whether EEI as an ideal index is correlated with the structure such as the flow arrangement or not was important and remained to be confirmed by the theoretical or experimental result. The present work was to analyze EEI for 5 heat exchangers with different flow arrangement: parallel flow, counter flow and combined flow by theoretical method. They all were composed of the same 37 pieces of BP type plate with Nu=0.091Re0.73Ptn, Eu=42400Re−0.545. Their inlet velocities between plates and the inlet temperatures for hot and cold fluid were the same and 5 mathematical models were developed. The EEI took into consideration and weighted quantitatively the heat transferred as well as the pressure drop. The comparison verified that the proposed EEI for 5 heat exchangers were different with each other, but 5 heat exchangers with similar flow arrangement were close to each other, less than 5%.