Applied Mechanics and Materials Vols. 291-294

Abstract: Plate-fin heat exchangers are playing an important role in the power and process industry in the recent past. Hence, it has become necessary to model their temperature response accurately. A new mathematical model of plate-fin heat exchanger is proposed, considering the heat conduction resistance along the fins and the separating plates. The effects of fin geometrical parameters and spacer thickness on the performances of the heat exchanger have been numerically calculated. It is found that the heat conduction resistance of fins has significant influence on the outlet fluid temperature variation. The analysis presented here suggests a better method of heat-transfer data analysis for plate heat exchangers.

Abstract: In order to determine the operating characteristics of a small-scale ORC (organic Rankine cycle) system for various low temperature heat sources, experiments were carried out. A small-scale ORC power generation system adopting R-245fa as a working fluid was designed and manufactured. Hot water was used for the heat source and the temperature was controlled by the 110 kW electric resistance heaters which provided up to 150 °C. Cooling temperature was controlled by a circulating water chiller to simulate various heat sink environments. An open-drive oil-free scroll expander directly connected to a high-speed synchronous generator was installed in the ORC unit. The efficiencies of the cycle and the expander, electric power of the developed ORC system with respect to the operating conditions were investigated by experiments. The factors which influence the performance of the oil-free scroll expander were analyzed and discussed.

Abstract: Air refrigerating systems offer a suitable alternative to vapour compression systems. Air can be used as working fluid in gas compression cycles for refrigeration, air conditioning and heat pump systems. This paper gives some results of theoretical investigation into improved air cycles for refrigeration systems and a comparison is made with their performances. The case-study relates to a dual purpose refrigerating plant. A blast freezing tunnel gives the coldest air stream and, in cascade, the air coming out from the tunnel is used in a channel network for feeding a lot of chilling cells. The case-study analysed indicates that there is a real possibility to build plants which will be equipped with air inverse cycles.

Abstract: Four turbulent models are introduced. The hypersonic aerodynamic heating calculation results by Shear Stress Transport (SST) turbulent model of different grid scale shows that near wall y+ spacing approximate to one third of the upper limit prescribed by turbulent model. Then, the comparison of the hypersonic aerodynamic heating calculation results by different turbulent model and the test data shows that SST turbulent model can give an enough accurate result.

Abstract: Open cycle absorption heat transformer (OAHT) is built and the off-design performance is discussed with simulation method. Results show the COP changes little when parameters various. The COP increases and water recovery ratio decreases as the temperature and flow rate of flue gas or of cooling water increase. With the same heat flow ejecting, the system has more stable performance as the humidity of flue gas changes.

Abstract: The engine knock has direct relation with the energy release rate. The faster combustion speed is, the higher heat release rate is. If heat release rate is too high, it will deteriorate reliability of the engine. A dual-fuel engine combustion mechanism model is established and intake pressure boundary conditions influence on the dual-fuel engine reliability is studied. Injection timing can supress engine knock and inprove engine reliability. Studies have shown that the greater the intake pressure, the smaller injection timing should be selected and the smaller the intake pressure, the larger injection timing should be selected. Appropriate injection timing can ensure reliability and power of the engine.

Abstract: As a new type of heating equipment, the heat medium heater furnace overcomes the shortage of the traditional heating methods such as the boiler, heating furnace. Through the comparison and analysis of the field application between the heat medium heater, YQWP - 4000/1.6/220/180-QT, and steam boiler in a central gathering station of Changqing oil field, results indicated: in the condition of 0.3 MPa pressure and 200 °Ctemperature above, the heat medium heater is higher thermal efficiency, more safety and security than steam boiler, and it do not pollute the environment and significantly save energy. One the heat medium heater saves by 982700 RMB than one set of steam boiler per each year. Due to the good economy, heat medium heater is suitable for the heating and heat supply of the large-scale central gathering station in the oil field. Thus, heat medium heater has a good application prospects. And the field application of the heat medium heater provides oil field energy saving and safe production with a certain reference in oil field.

Abstract: Experimental investigation of the critical heat flux (CHF) in smooth round tubes with circumferentially variable heating was carried out. The riser tubes with 0, 20, 90-degree inclinations from the horizontal were electrically heated. The measurements were carried out for pressure between 13 and 21MPa, mass flux between 600 and 900kg/m2s. The peak-to average heat flux ratio was amounted to 1.6. CHF data of uniform heating were also tested. The test results show that the initial CHF is always observed at location of peak heat flux in vertical tubes with non-uniform heating. In horizontal and inclined tubes with side-heating the transit from a top to side initial indication of CHF occurs by increasing the mass flux and the pressure to certain values. The Initial CHF of non-uniformly heated tubes is fairly agreement with the values of uniformly heated tubes.

Abstract: Polymorphs is present in many crystalline drug, different crystal type tend to produce different effects. Drug quality and curative effect of the important quality index is drug heteromorphic stability .The change of drug heteromorphic will change the nature, quality, efficacy of the drug. Generally speaking, the greater the crystal particle size, heating melting needs more energy, the more stable. The crystal type which has high melting point, the chemistry stability is good, but the solubility and digestion rate is low. HMP has different polycrystalline forms, at present reports in the literature there are two kinds of crystal type, form Ⅰ and form Ⅱ. The form Ⅰ is more stable than form Ⅱ, and has higher melting point. This article research the relationship between HMP polymorphism and melting point based with the drug melting point meter and DSC.

Abstract: As an effective energy-saving device, the heat pump is environmentally friendly and advantageous in the recovery of low-temperature and middle-temperature waste heat. So it is increasingly being used in practical applications. The circulating water which is produced by power plants has a large number of low-temperature waste heat. It will bring huge economic and environmental benefits by using heat pump technology to recover those waste heat energy. The application of the heat pump in supercritical unit is discussed as the example of central heating project using waste heat in a power plant. And the basic principle of absorption heat pump is introduced. The economy, energy conservation and environmental benefits of lithium bromide absorption heat pump are also analyzed when it is used in 600MW supercritical unit.