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An irreversible Braysson heat engine cycle model, in which the heat transfer obeys a linear heat transfer law between the working fluid and the external heat reservoirs, with heat resistance, heat leak and internal irreversibility is established in this paper. The analytical expressions of power output, efficiency and ecological objective function are derived. These performance parameters are maximized...
There are geothermal anomalies in Pingdingshan mining area, the average geothermal gradient of up to 4.6°C /100m, which forms geothermal mine disasters. The formation of geothermal anomalies is more closely related to geological structure and groundwater. Using groundwater heat pump technology and air heat exchange system, exploiting the geothermal resources of these mines, which helps to reduce heat...
Heat release analysis in diesel engines is a powerful method to investigate the combustion process and engine performance. The aim of this study is to simulate the heat release rate during combustion using the measured in-cylinder pressure based on thermodynamic principles. After determining the submodels such as mass and composition, gas and fuel properties, heat of combustion, heat loss to the walls,...
This paper designed and described a Helmholtz-type valveless self-excited pulse combustor with continuous fuel and air supply. Its structure is similar to the conventional Helmholtz type's, but valves are not used. The operational characteristics of the Helmholtz-type valveless self-excited pulse combustor was investigated by the experiment. The effects of the excess air ratio, tailpipe length and...
The technology of horizontal-tube falling film evaporation is widely used in low temperature multi-effect distillation evaporators. The heat transfer coefficient of it depends on many factors, such as steam velocity, sprinkle density, evaporation temperature, etc. In the engineering design of evaporator, much smaller sprinkle density may led to "dry points on tube", while much bigger sprinkle...
Laminar natural convection arising from horizontal rectangle cylinder to its concentric cylindrical enclosure is numerically studied. The Rayleigh number is varied in the range of 103≤Ra≤106. According to the form of isotherms and the streamline patterns, the basic features of flow and heat transfer for four rectangle cylinders with different aspect ratios are reported. And the local and average Nusselt...
Abstract-Simultaneous transport of heat and moisture by conjugate natural convection in an enclosure with a solid wall and two free ports is investigated numerically. Moist air motions are driven by the external temperature and concentration differences imposed across enclosures with different ambient moisture conditions. The Prandtl number and Schmidt number used are 0.7 and 0.6 respectively. The...
Liquefied Natural Gas (LNG) is being developed as a transportation fuel for transit buses, to lessen the dependency on oil and to reduce greenhouse gas emissions. But LNG is hazardous because of its temperature, the possibility of asphyxiation and of course the fire risk. This paper describes the use of Fluent, a widely-used commercial CFD code, to simulate the dynamics of spills from LNG bus fuel...
Groundwater source heat pump system has great impact on the temperature of groundwater for a long-term. According to the continuity equations, motion equations and energy equations of fluid cylindrical coordinate system and the boundary conditions of pumping production and injection well, the forced convection in turbulent flows model of smooth cylinder has been established. Consider three ways of...
According to the basic law of energy conservation and conversion, the energy consumption evaluation indexes of two basic research objects in oil-gas gathering and transferring system, i.e. stations and pipelines, are established. On the basis of that, the energy consumption evaluation indexes for the whole system are obtained through mean weighted method. Then heat loss rate and pressure loss rate...
Surface source heat pump system with freezing latent heat collection plays a significant role in energy-saving and environmental protection in districting heating of the cold areas. In the system, the surface water freezing latent heat exchanger is one of the key devices and its operating parameters are directly related to the heating performance. Based on the entropy generation theorem, the entropy...
Lots of experimental researches have been done to a plain tubes segmental baffles lubricating-oil cooler and integral pin-fin tube cooler and the new lubricating-oil cooler made from integral pin-fin tubes and plain tubes mixing in bundles and with double-flow. It is introduced that oil mass flow rate has great influence on coolers performance. Heat transfer coefficient, pressure drop, the heat of...
The integral pin-fin tube is a new type of non-continuous finned tubes, increasing the effective heat transfer area, while its non-continuous fin structure can strongly stimulate the fluid boundary layer separation, to achieve enhanced heat transfer effect. Using fluent software three-dimensional numerical simulation on integral pin-fin tube is got. The results is accord to the actual situation, verifies...
In order to improve the utilization of solar energy, we use the new flat-plate heat pipe in the solar photovoltaic/thermal (PV/T) system to meanwhile gain electricity and heat. In this way, the temperature of solar cell could be effectively reduced to improve power generation efficiency, and the heat dissipation of solar panel could also be stored up through the forced circulation of the aqueous solution...
Four types of double-stage Water-Lithium Bromide absorption heat pump systems were introduced to recover waste heat of about 40°C. Thermodynamic and heat transfer numerical simulation was carried out to predict the performance of these absorption heat pumps. The effects of the driving heat source (steam) input pressure, the waste heat outlet temperature, and the hot water inlet temperature on the...
The back-pressure of the direct air-cooled unit directly affects the system running economy. Based on the thermodynamic model of the air-cooled system, according to the basic method of seeking the optimal back-pressure in theory, this article has established the back-pressure optimization mathematical model of the air-cooled unit to obtain the optimal back-pressure under the actual operating conditions,...
In this paper, changes of thermal conductivity of paraffin mixtures joined different percentages of aluminum, copper, silicon powder were stuPdied. Feasibility of adding these three kinds of powders into paraffin to enhance paraffin's thermal properties was studied, as well as the influence of different addictives on paraffin's phase-change temperature and latent heat. The results showed that adding...
An experimental study on the two-phase injector has been carried out in this paper. The main project was expected that the discharged water pressure could exceed the motive steam pressure, which made such an injector feasible to recalculate the coolant to the generator and replace the mechanical pump in an injector refrigeration system. Compared with previous studies, this paper's biggest difference...
To resolve the problem of reclaiming residual heat of the flue gas for thermal organic media furnace with coal as fuel, a technique project of reclaiming residual heat of the flue gas using heat pipe technology is put forward, and the technology of heat exchanger network is optimized. 1.25MPa steam produced by the heat pipe steam generator reclaiming residual heat of the flue gas can supply supplement...
Contact resistance of Gas insulated switchgear (GIS) bus conductor would increase and overheat itself in long-term operation. This paper established mathematical model to figure out temperature distribution of 4kA single-phase GIS bus. Power loss in electromagnetic field was calculated and indirectly coupled to temperature and flow field. Calculation result showed that the temperature distribution...
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