Like in other sectors of activity, the sustainability in refrigeration systems is a mandatory goal to achieve, namely at house holdings, bars and restaurants, where small-scale refrigerators and freezers are widely us...Like in other sectors of activity, the sustainability in refrigeration systems is a mandatory goal to achieve, namely at house holdings, bars and restaurants, where small-scale refrigerators and freezers are widely used. The aim of this work is to demonstrate experimentally, trough measurements carried out in these equipments, the improvement that can be achieved if several modifications are implemented in traditional household refrigeration systems. In addition, it was also simulated and analysed experimentally a slightly different equipment, a refrigeration system used for draught beverages. Both systems work on a single vapour compression refrigeration with R-134a as working fluid. In the end, by implemented the modifications tested in the virtual model, it was possible to improve their thermal behaviour, a decrease in electrical energy consumption, as well as, the associated CO2 emissions reduction can be attained. In this project, the CFD （Computational Fluid Dynamics） soffware--ANSYS Fluent was used to simulate the ambient temperature and velocity fields inside the refrigerator and in that way to validate the measured results.展开更多
Recovering waste heat from industrial processes is bene ficial 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 ...Recovering waste heat from industrial processes is bene ficial 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 Chem Cad? 6.0.1.LiBr–H_2O 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 coef ficients 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 coef ficient 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 coef ficient of performance,cooling capacity and working fluid temperature.For hybrid heat pump,the different coef ficients 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.展开更多
文摘Like in other sectors of activity, the sustainability in refrigeration systems is a mandatory goal to achieve, namely at house holdings, bars and restaurants, where small-scale refrigerators and freezers are widely used. The aim of this work is to demonstrate experimentally, trough measurements carried out in these equipments, the improvement that can be achieved if several modifications are implemented in traditional household refrigeration systems. In addition, it was also simulated and analysed experimentally a slightly different equipment, a refrigeration system used for draught beverages. Both systems work on a single vapour compression refrigeration with R-134a as working fluid. In the end, by implemented the modifications tested in the virtual model, it was possible to improve their thermal behaviour, a decrease in electrical energy consumption, as well as, the associated CO2 emissions reduction can be attained. In this project, the CFD （Computational Fluid Dynamics） soffware--ANSYS Fluent was used to simulate the ambient temperature and velocity fields inside the refrigerator and in that way to validate the measured results.
文摘Recovering waste heat from industrial processes is bene ficial 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 Chem Cad? 6.0.1.LiBr–H_2O 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 coef ficients 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 coef ficient 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 coef ficient of performance,cooling capacity and working fluid temperature.For hybrid heat pump,the different coef ficients 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.
