This paper focuses on the development of three types of activated carbon （AC） adsorbents, i.e. granular AC, consolidated AC with chemical binder, and consolidated AC with expanded natural graphite （ENG）. Their the...This paper focuses on the development of three types of activated carbon （AC） adsorbents, i.e. granular AC, consolidated AC with chemical binder, and consolidated AC with expanded natural graphite （ENG）. Their thermal conductivity was investigated with the steady-state heat source method and the permeability was tested with nitrogen as the gas source. Results show that the thermal conductivity of granular AC with different sizes al-most maintains a constant at 0.36 W-（m.K）-＇, while the value modestly increases to 0.40 W.（m.K）-＇ for the con- solidated AC with chemical binder. The consolidated AC with ENG at the density of 600 kg. m-3 shows the best heat transfer performance and their thermal conductivity vary from 2.08 W-（m.K）- to 2.61 W. （m.K）-1 according toits fraction of AC. However, the granular AC and consolidated AC with chemical binder show the better permeabil- ity performance than consolidated AC with ENG binder whose permeability changes from 6.98x10-13 m2 to 5.16x10TM m2 and the maximum occurs when the content of AC reaches 71.4% （by mass）. According to the differ- ent thermal properties, the refrigeration application of three types of adsorbents is analyzed.展开更多
This paper is focused on the cascade refrigeration cycle using natural refrigerant CO 2-NH 3. The properties of refrigerants CO 2 and NH 3 are introduced and analyzed.CO 2 has the advantage in low stage of cascade ref...This paper is focused on the cascade refrigeration cycle using natural refrigerant CO 2-NH 3. The properties of refrigerants CO 2 and NH 3 are introduced and analyzed.CO 2 has the advantage in low stage of cascade refrigeration cycle due to its good characteristics and properties. The thermodynamic analysis results of the CO 2-NH 3 cascade refrigeration cycle demonstrates that the cycle has an optimum condensation temperature of low stage and also has an optimum flow rate ratio.By comparing with the R13-R22 and NH 3-NH 3 cascade refrigeration cycles, the mass flow rate ratio of CO 2-NH 3 is larger than those of R13-R22 and NH 3-NH 3, the theoretical COP of CO 2-NH 3 cascade refrigeration cycle is larger than that of the R13-R22 cascade cycle and smaller than that of the NH 3-NH 3 cascade cycle. But the real COP of CO 2-NH 3 cascade cycle will be higher than those of R13-R22 and NH 3-NH 3 because the specific volume of CO 2 at low temperature does not change much and its dynamic viscosity is also small.展开更多
The paper presents an investigation of energy and exergy analysis of an existing ORC （organic rankine cycle） unit powered by hot geothermal water. The validated model of this unit was used to examine 25 refrigerants...The paper presents an investigation of energy and exergy analysis of an existing ORC （organic rankine cycle） unit powered by hot geothermal water. The validated model of this unit was used to examine 25 refrigerants belonging to different chemical compositions. The study revealed that R141b and R123 produced the best net power, energy efficiency, and exergy efficiency, whereas R125 was the lowest. Hydrofluorocarbons （except R143a）, hydrocarbons, and inorganic reflected attractive energy and exergy efficiencies. All investigated mixtures gained low performance compared with other studied candidates. The R245ca was the best among the hydrofluorocarbons studied refrigerants, and R501 was the best among the mixture refrigerants. Furthermore, within the ORC system, the evaporator was found to have the highest exergy destruction and the refrigerant pump was the lowest.展开更多
基金Supported by the National Science Foundation for Excellent Young Scholars （51222601）, the International Collaborating Project Funded by the Foundation of Science and Technology Commission of Shanghai Municipality （11160706000）, the Program for New Century Excellent Talents in University by the Ministry of Education of China and the Shanghai Pujiang Program of China.
文摘This paper focuses on the development of three types of activated carbon （AC） adsorbents, i.e. granular AC, consolidated AC with chemical binder, and consolidated AC with expanded natural graphite （ENG）. Their thermal conductivity was investigated with the steady-state heat source method and the permeability was tested with nitrogen as the gas source. Results show that the thermal conductivity of granular AC with different sizes al-most maintains a constant at 0.36 W-（m.K）-＇, while the value modestly increases to 0.40 W.（m.K）-＇ for the con- solidated AC with chemical binder. The consolidated AC with ENG at the density of 600 kg. m-3 shows the best heat transfer performance and their thermal conductivity vary from 2.08 W-（m.K）- to 2.61 W. （m.K）-1 according toits fraction of AC. However, the granular AC and consolidated AC with chemical binder show the better permeabil- ity performance than consolidated AC with ENG binder whose permeability changes from 6.98x10-13 m2 to 5.16x10TM m2 and the maximum occurs when the content of AC reaches 71.4% （by mass）. According to the differ- ent thermal properties, the refrigeration application of three types of adsorbents is analyzed.
文摘This paper is focused on the cascade refrigeration cycle using natural refrigerant CO 2-NH 3. The properties of refrigerants CO 2 and NH 3 are introduced and analyzed.CO 2 has the advantage in low stage of cascade refrigeration cycle due to its good characteristics and properties. The thermodynamic analysis results of the CO 2-NH 3 cascade refrigeration cycle demonstrates that the cycle has an optimum condensation temperature of low stage and also has an optimum flow rate ratio.By comparing with the R13-R22 and NH 3-NH 3 cascade refrigeration cycles, the mass flow rate ratio of CO 2-NH 3 is larger than those of R13-R22 and NH 3-NH 3, the theoretical COP of CO 2-NH 3 cascade refrigeration cycle is larger than that of the R13-R22 cascade cycle and smaller than that of the NH 3-NH 3 cascade cycle. But the real COP of CO 2-NH 3 cascade cycle will be higher than those of R13-R22 and NH 3-NH 3 because the specific volume of CO 2 at low temperature does not change much and its dynamic viscosity is also small.
文摘The paper presents an investigation of energy and exergy analysis of an existing ORC （organic rankine cycle） unit powered by hot geothermal water. The validated model of this unit was used to examine 25 refrigerants belonging to different chemical compositions. The study revealed that R141b and R123 produced the best net power, energy efficiency, and exergy efficiency, whereas R125 was the lowest. Hydrofluorocarbons （except R143a）, hydrocarbons, and inorganic reflected attractive energy and exergy efficiencies. All investigated mixtures gained low performance compared with other studied candidates. The R245ca was the best among the hydrofluorocarbons studied refrigerants, and R501 was the best among the mixture refrigerants. Furthermore, within the ORC system, the evaporator was found to have the highest exergy destruction and the refrigerant pump was the lowest.
