A quantitative energy efficiency evaluation and grading of plate heat exchangers

Energy efficiency evaluation of heat exchangers are crucial for energy saving in industrial applications. Currently, no energy efficiency evaluation is appropriate for the grading of energy efficiency of heat exchangers. In this paper, an energy efficiency index (EEI) is proposed to evaluate the energy efficiency of single-phase flow and heat transfer of plate heat exchangers. EEI is defined by k/∇pn, where k is overall heat transfer coefficient, ∇p is flow pressure gradient and exponent n is the indicator of the relative importance between heat transfer and flow resistance. EEI indicates the overall heat transfer coefficient per unit equivalent pressure drop. The recommended n is 0.31 for plate heat exchangers based on the data of 281 heat exchangers. We conclude a normal distribution function for the evaluation of energy efficiency of plate heat exchangers. The present method can quantitative evaluate the performance of plate heat exchangers and hence can grade them in terms of energy efficiency.