Thermodynamic and Economic Analysis of Heat Pumps for Energy Recovery in Industrial Processes

Abstract

A computer code has been developed for analyzing the thermodynamic performance, cost and economic return for heat pump applications in industrial heat recovery. Starting with basic defining characteristics of the waste heat stream and the desired heat sink, the algorithm first evaluates the potential for conventional heat recovery with heat exchangers, and if applicable, sizes the exchanger. A heat pump system is then designed to process the residual heating and cooling requirements of the streams. In configuring the heat pump, the program searches a number of parameters, including condenser temperature, evaporator temperature, and condenser and evaporator approaches. All system components are sized for each set of parameters, and economic return is estimated and compared with system economics for conventional processing of the heated and cooled streams (i.e., with process heaters and coolers). Several thermodynamic and economic performance ratios are computed for comparative evaluation of heat pumps versus conventional systems. Two case studies are evaluated, one in a food processing application and the other in an oil refinery unit. Results of the case studies are presented to illustrate the use of the program and to show the sensitivity of heat pump system economics to the various design parameters.