Performance explorations of a novel high temperature heat pump with multi-adjusted compositions of zeotropic mixture

Abstract

High temperature heat pump has received its invigorated interests in recovering industrial waste heat due to its abilities of improving energy efficiency and reducing carbon emissions. But it is subjected to performance degradation at the varied operating conditions. To tackle this challenge, a novel vapor injected heat pump that ingeniously integrates with a liquid-separation condenser as the separating device and an ejector as the combining device (LEHP) is proposed, and it is featured by actively adjusting of the composition of zeotropic mixture. The mathematical model is established and verified. Six environmentally friendly zeotropic mixtures with different temperature glides are selected as working fluids. Comparison results show that the coefficient of performance of the proposed system is 21.86% higher than that of the conventional heat pumps. Parametrical studies indicate that a decrease in the vapor quality for liquid separation or an increase in the flash tank pressure is beneficial to the system performance and temperature matching in heat transfer processes. Its potentials under various operating conditions are further explored and mapped by using Genetic Algorithm. Propane/Cyclobutene is suitable at the heat source inlet temperature lower than 30 °C, and Cyclopropane/Pentane or Cyclopropane/Hexane is favored as ranging from 40 °C to 50 °C, when it is higher than 50 °C, Butene/Cyclohexane should be selected. Under unique scenarios of equivalent inlet temperatures for heat sink and heat source, Butene/Cyclohexane and Cyclopropane/Hexane demonstrate broad applicability across various operating conditions. The maximum coefficient of performance of 4.72 and exergy efficiency of 68.29% are found when Butene/Cyclohexane is employed.