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
The effect of the circulation fan installed in fresh food compartment on energy consumption of natural convective refrigerator/freezers (RFs) was experimentally studied. Five different RF models with different cycles ...The effect of the circulation fan installed in fresh food compartment on energy consumption of natural convective refrigerator/freezers (RFs) was experimentally studied. Five different RF models with different cycles were tested. The experimental results showed that the energy consumption of the single-loop cycle RF increased by 2.4%~3.8%, that of the bypass two-circuit cycle RF decreased by 1.0%, and that of the two-circuit cycle RF with its evaporators in parallel when the geometry parameters of refrigeration system and the refrigerant charge were not changed after the circulation fan was installed decreased by 3.3%. When the optimization on the refrigerant charge and the evaporator was carried out, the energy consumption of the single-loop cycle RF , the bypass two-circuit cycle RF and the two-circuit cycle RF with its evaporators in parallel, decreased by 1.0%~6.4%, 3.25% and 3.26% respectively. The present conclusions will provide a guideline to the optimum design for the RF with the circulation fan.展开更多
A two dimensional model of the transient natural convection in a freezer is studied numerically by finite volume approach.The temperatures of the freezer outside surfaces and the evaporator vary in specified manners,w...A two dimensional model of the transient natural convection in a freezer is studied numerically by finite volume approach.The temperatures of the freezer outside surfaces and the evaporator vary in specified manners,which were taken from an experimental work.The fluid in the freezer is of the Bousinnesq type and the flow is assumed laminar,The transient heat conduction in the insulating layers and the temperature and velocity fields of the fluid are solved conjugately.The radiation heat transfer between the freezer inner surfaces is taken into account by using the additional source term method.The distributions of the local Nusselt number along the upper and lower surfaces of the evaporator and their average values in the period of periodically unsteady operation are calculated.Comparisons are made between the results with and without consideration of inner surface radiative heat transfer.It is found that the radiative heat transfer between the inner surfaces has a profound effect on the evaporator heat transfer characteristics.展开更多
恶妇杀夫,竟将尸体藏匿于冰箱之中,5年之后,其劣迹方才败露！消息首句系十足的主题句(topic sentence)。此句值得学习的是其定语从句,whohad been missing for five years,它被置于状语从句的主语和谓语之间。这种“插入”形式,为初学...恶妇杀夫,竟将尸体藏匿于冰箱之中,5年之后,其劣迹方才败露！消息首句系十足的主题句(topic sentence)。此句值得学习的是其定语从句,whohad been missing for five years,它被置于状语从句的主语和谓语之间。这种“插入”形式,为初学者所不能。初学者往往将该句写成:...after the body of herhusband was found in a discarded freezer who have been missing for five years.须知:定语从句应紧挨其修饰的成以免引起误解。这在语言学上称就近原则(vicinity principle)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The effect of the circulation fan installed in fresh food compartment on energy consumption of natural convective refrigerator/freezers (RFs) was experimentally studied. Five different RF models with different cycles were tested. The experimental results showed that the energy consumption of the single-loop cycle RF increased by 2.4%~3.8%, that of the bypass two-circuit cycle RF decreased by 1.0%, and that of the two-circuit cycle RF with its evaporators in parallel when the geometry parameters of refrigeration system and the refrigerant charge were not changed after the circulation fan was installed decreased by 3.3%. When the optimization on the refrigerant charge and the evaporator was carried out, the energy consumption of the single-loop cycle RF , the bypass two-circuit cycle RF and the two-circuit cycle RF with its evaporators in parallel, decreased by 1.0%~6.4%, 3.25% and 3.26% respectively. The present conclusions will provide a guideline to the optimum design for the RF with the circulation fan.
基金the National Natural Science Foundation of China
文摘A two dimensional model of the transient natural convection in a freezer is studied numerically by finite volume approach.The temperatures of the freezer outside surfaces and the evaporator vary in specified manners,which were taken from an experimental work.The fluid in the freezer is of the Bousinnesq type and the flow is assumed laminar,The transient heat conduction in the insulating layers and the temperature and velocity fields of the fluid are solved conjugately.The radiation heat transfer between the freezer inner surfaces is taken into account by using the additional source term method.The distributions of the local Nusselt number along the upper and lower surfaces of the evaporator and their average values in the period of periodically unsteady operation are calculated.Comparisons are made between the results with and without consideration of inner surface radiative heat transfer.It is found that the radiative heat transfer between the inner surfaces has a profound effect on the evaporator heat transfer characteristics.
文摘恶妇杀夫,竟将尸体藏匿于冰箱之中,5年之后,其劣迹方才败露！消息首句系十足的主题句(topic sentence)。此句值得学习的是其定语从句,whohad been missing for five years,它被置于状语从句的主语和谓语之间。这种“插入”形式,为初学者所不能。初学者往往将该句写成:...after the body of herhusband was found in a discarded freezer who have been missing for five years.须知:定语从句应紧挨其修饰的成以免引起误解。这在语言学上称就近原则(vicinity principle)
