CO2/acetone mixture desorption process in a plate heat exchanger for compression/resorption heat pumps

Abstract

Industrial processes represent one of the activities that consume the most energy, which is related to the use of fossil fuels and growing environmental problems. In this way, the recovery of residual heat energy has been presented as an efficient solution to take advantage of low-quality residual heat, where the compressor-resorption heat pump technology has proven to reach high temperature levels with a considerable Coefficient of Performance. The importance of this work lies in the validation of the ecofriendly CO2/Acetone mixture as a useful working fluid for a compressor-resorption heat pump, initiating the experimental study in the desorption process as a novel application. Even more, the cycle of the bomb has been simulated on previous research regarding a literature comparative and the present work validates it by experimental means. The process of desorption of the CO2/acetone mixture was studied in a heat exchanger of plates with operating conditions for conducts formed by 4 plates/3 channels, for compression/resorption heat pumps. Result ranges have been obtained for solution heat transfer coefficient between 0.10 and 0.50 kW × m−2 × K−1, average vapor flow rate between 0.02 and 0.16, heat flow rate between 1.50 and 5.20 kW × m−2 × K−1 and desorption mass flow rate between 2 and 5 kg × m−2 s−1 × 10−3 in the central channel of the plate heat exchanger. Finally, an empirical correlation is proposed to extend the results of the heat transfer coefficient of the CO2/acetone solution in applications outside the experimentally determined range, from the comparison between experimental data and determined by correlation of enthalpy of the solution, an average minimum, mean and maximum deviation of 0.2, 13.5 and 22.3 %, respectively, was determined. In this way, the results shows that the most influential variables are the test pressure and heating water temperature at the inlet of the desorber, where, with a concentration of CO2 (XCO2) between 22 and 25 %, the heat transfer coefficients obtained have an order of 0.50 kW × m−2 × K−1. On the other hand, viscosity favours heat transfer, thermal conductivity is a determining factor for the desorption process. This contributes to lower heat transfer coefficient and heat flow in the heat exchanger for the CO2/acetone mixture compared to the other mixtures.