Mathematical model of absorption and hybrid heat pump

doi:10.1016/j.cjche.2017.06.015

Abstract

Abstract: Recovering waste heat from industrial processes is beneficial in order to reduce the primary energy demands and heat pumps can be used to this purpose. Absorption heat pumps are energy-saving and environment-friendly because use working fluids that do not cause ozone depletion and can reduce the global warming emissions. The hybrid heat pump processes combine the conventional vapor-compression and the absorption heat pump cycles. Studies about the simulations and modeling of hybrid heat pumps are few in literature. In this research a mathematical model for single effect absorption and hybrid heat pump is carried out with ChemCad^® 6.0.1. LiBr-H₂O is used as working fluid while electrolytic NRTL and electrolytes latent heat are used as thermodynamic model due to the better results. Binary parameters of activity coefficients are regressed from experimental vapor pressure data while default constants are used for the solubility expressions. A design of heat pumps is developed and a new modeling of generator is analyzed. The coefficient of performance of absorption heat pump and hybrid heat pump is equal to 0.7 and 0.83 respectively. For absorption heat pump a sensitivity analysis is carried out to evaluate the effect of temperature and pressure generator, the concentration of Li-Br solution on coefficient of performance, cooling capacity and working fluid temperature. For hybrid heat pump, the different coefficients of performance, the primary energy ratio, the generator heat, and the compressor power are analyzed for different values of compressor proportion. Results show that comparing the two systems the hybrid pump allows to save more primary energy, costs and carbon dioxide emissions with respect to absorption heat pump with the increasing of compressor proportion parameter. Future researches should focus on the construction of this heat pumps integrated in chemical processes as a biogas plant or trigeneration systems.

Key words: Absorption heat pumps, Hybrid heat pumps, LiBr-H₂O modeling, Energy efficiency, Process simulation, Mathematical model

摘要： Recovering waste heat from industrial processes is beneficial in order to reduce the primary energy demands and heat pumps can be used to this purpose. Absorption heat pumps are energy-saving and environment-friendly because use working fluids that do not cause ozone depletion and can reduce the global warming emissions. The hybrid heat pump processes combine the conventional vapor-compression and the absorption heat pump cycles. Studies about the simulations and modeling of hybrid heat pumps are few in literature. In this research a mathematical model for single effect absorption and hybrid heat pump is carried out with ChemCad^® 6.0.1. LiBr-H₂O is used as working fluid while electrolytic NRTL and electrolytes latent heat are used as thermodynamic model due to the better results. Binary parameters of activity coefficients are regressed from experimental vapor pressure data while default constants are used for the solubility expressions. A design of heat pumps is developed and a new modeling of generator is analyzed. The coefficient of performance of absorption heat pump and hybrid heat pump is equal to 0.7 and 0.83 respectively. For absorption heat pump a sensitivity analysis is carried out to evaluate the effect of temperature and pressure generator, the concentration of Li-Br solution on coefficient of performance, cooling capacity and working fluid temperature. For hybrid heat pump, the different coefficients of performance, the primary energy ratio, the generator heat, and the compressor power are analyzed for different values of compressor proportion. Results show that comparing the two systems the hybrid pump allows to save more primary energy, costs and carbon dioxide emissions with respect to absorption heat pump with the increasing of compressor proportion parameter. Future researches should focus on the construction of this heat pumps integrated in chemical processes as a biogas plant or trigeneration systems.

关键词: Absorption heat pumps, Hybrid heat pumps, LiBr-H₂O modeling, Energy efficiency, Process simulation, Mathematical model

Grazia Leonzio. Mathematical model of absorption and hybrid heat pump[J]. , 2017, 25(10): 1492-1504.

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