A new apparatus, with a segregable conical water cooling condenser, which is heated by an electric arc using the evaporation-condensation method to prepare carbon-coated nanopowder, has been developed by the authors. ...A new apparatus, with a segregable conical water cooling condenser, which is heated by an electric arc using the evaporation-condensation method to prepare carbon-coated nanopowder, has been developed by the authors. Numerical simulation of the temperature field is done by the ANSYS software, and temperature in the reaction vessel is measured with the help of an experiment, to verify the simulation result. Influence of the temperature field in the reaction vessel, on the process of preparing nanopowder is then discussed simply. It is shown that the segregable conical water cooling condenser and carbon-coated surface process can be used to prepare steady carbon-coated metal nanopowder, at a lower cost and higher yield rate than the traditional structure. Simulation of the temperature field in the apparatus shows that the arc heating method can form a temperature field in the apparatus, which is quite favorable for nanopowder formation. Experiments show that the rational parameters using this apparatus, with the arc heating method to prepare carbon-coated nanopowder are electricity 60-100 A and arc length 5-8 mm.展开更多
The thermodynamic aspect of a compression type heat pump （HP） is briefly described and special attention is given to investigation of condensing temperature influence on heat pump efficiency in heating mode, express...The thermodynamic aspect of a compression type heat pump （HP） is briefly described and special attention is given to investigation of condensing temperature influence on heat pump efficiency in heating mode, expressed by its coefficient of performance （COP）. Heat pumps are usually applied for the purposes of heating and cooling of energy efficient buildings where they have advantages in low-temperature systems, as it is well documented in the paper. The comparison of real thermodynamic processes with thermodynamically most favorable Camot＇s process is made. The results in the paper show that COP is diminishing with increasing of condensing temperature and also depends on real properties of working fluids. The impact of compressor efficiency for two real working media is also analyzed in the paper. There is significant diminishing of COP with diminishing of compressor efficiency. The intension of the paper is to help better understanding of this very effective and prosperous technology, and to encourage its development, production, and efficient application.展开更多
The plasma polymerization method and dynamic ion-beam mixed implantation method were employed to coat ultra-thin polymer films on copper plates. Experiments indicated that steady dropwise condensation of steam at atmo...The plasma polymerization method and dynamic ion-beam mixed implantation method were employed to coat ultra-thin polymer films on copper plates. Experiments indicated that steady dropwise condensation of steam at atmospheric pressure occurred. The condensation heat transfer coefficients increased by approximately 3 and 5－7 times for the polytrimethylvinylsilane film and polytetrafluoroethylene film respectively, compared with the value for film condensation under the same experimental conditions. The temperatures on the condensing surface and inside the test block were found to be rapidly and randomly fluctuated. The properties of the coated films and advantages of the methods used in this investigation were discussed briefly.展开更多
The thermodynamic(energy and exergy)analysis of a condensate heating system,its segments,and components from a marine steam propulsion plant with steam reheating is performed in this paper.It is found that energy anal...The thermodynamic(energy and exergy)analysis of a condensate heating system,its segments,and components from a marine steam propulsion plant with steam reheating is performed in this paper.It is found that energy analysis of any condensate heating system should be avoided because it is highly influenced by the measuring equipment accuracy and precision.All the components from the observed marine condensate heating system have energy destructions lower than 3 kW,while the energy efficiencies of this system are higher than 99%.The exergy efficiency of closed condensate heaters continuously increases from the lowest to the highest steam pressures(from 70.10%to 92.29%).The ambient temperature variation between 5℃and 45℃notably influences the exergy efficiency change of both low pressure heaters and the low pressure segment equal to 31.61%,12.37%,and 18.35%,respectively.展开更多
文摘A new apparatus, with a segregable conical water cooling condenser, which is heated by an electric arc using the evaporation-condensation method to prepare carbon-coated nanopowder, has been developed by the authors. Numerical simulation of the temperature field is done by the ANSYS software, and temperature in the reaction vessel is measured with the help of an experiment, to verify the simulation result. Influence of the temperature field in the reaction vessel, on the process of preparing nanopowder is then discussed simply. It is shown that the segregable conical water cooling condenser and carbon-coated surface process can be used to prepare steady carbon-coated metal nanopowder, at a lower cost and higher yield rate than the traditional structure. Simulation of the temperature field in the apparatus shows that the arc heating method can form a temperature field in the apparatus, which is quite favorable for nanopowder formation. Experiments show that the rational parameters using this apparatus, with the arc heating method to prepare carbon-coated nanopowder are electricity 60-100 A and arc length 5-8 mm.
文摘The thermodynamic aspect of a compression type heat pump （HP） is briefly described and special attention is given to investigation of condensing temperature influence on heat pump efficiency in heating mode, expressed by its coefficient of performance （COP）. Heat pumps are usually applied for the purposes of heating and cooling of energy efficient buildings where they have advantages in low-temperature systems, as it is well documented in the paper. The comparison of real thermodynamic processes with thermodynamically most favorable Camot＇s process is made. The results in the paper show that COP is diminishing with increasing of condensing temperature and also depends on real properties of working fluids. The impact of compressor efficiency for two real working media is also analyzed in the paper. There is significant diminishing of COP with diminishing of compressor efficiency. The intension of the paper is to help better understanding of this very effective and prosperous technology, and to encourage its development, production, and efficient application.
基金the National Natural Science Foundation of China (No. 59906002) and the Foundation for Young Teachers of Dalian University of Technology.
文摘The plasma polymerization method and dynamic ion-beam mixed implantation method were employed to coat ultra-thin polymer films on copper plates. Experiments indicated that steady dropwise condensation of steam at atmospheric pressure occurred. The condensation heat transfer coefficients increased by approximately 3 and 5－7 times for the polytrimethylvinylsilane film and polytetrafluoroethylene film respectively, compared with the value for film condensation under the same experimental conditions. The temperatures on the condensing surface and inside the test block were found to be rapidly and randomly fluctuated. The properties of the coated films and advantages of the methods used in this investigation were discussed briefly.
基金This research is supported by the Croatian Science Foundation under the project IP-2018-01-3739,CEEPUS network CIII-HR-0108,European Regional Development Fund under the grant KK.01.1.1.01.0009(DATACROSS)project CEKOM under the grant KK.01.2.2.03.0004,CEI project“COVIDAi”(305.6019-20)University of Rijeka Scientific Grants uniri-tehnic-18-275-1447,uniritehnic-18-18-1146 and uniri-tehnic-18-14.
文摘The thermodynamic(energy and exergy)analysis of a condensate heating system,its segments,and components from a marine steam propulsion plant with steam reheating is performed in this paper.It is found that energy analysis of any condensate heating system should be avoided because it is highly influenced by the measuring equipment accuracy and precision.All the components from the observed marine condensate heating system have energy destructions lower than 3 kW,while the energy efficiencies of this system are higher than 99%.The exergy efficiency of closed condensate heaters continuously increases from the lowest to the highest steam pressures(from 70.10%to 92.29%).The ambient temperature variation between 5℃and 45℃notably influences the exergy efficiency change of both low pressure heaters and the low pressure segment equal to 31.61%,12.37%,and 18.35%,respectively.
