The wind velocity plays a crucial role in the operation characteristic of indirect cooling tower. In this paper a 2×330MW vertical arrangement indirect air-cooled system was taken as research object, and numerica...
The wind velocity plays a crucial role in the operation characteristic of indirect cooling tower. In this paper a 2×330MW vertical arrangement indirect air-cooled system was taken as research object, and numerical simulation method was used to analyze the relative influence of the wind speed, ranging from 4m/s to 18m/s, on the outlet water temperature of cooling tower, the outlet air temperature of radiator, the facing wind speed of the fan segment and on the outlet air speed of the cooling tower. The result shows that the impact of the natural wind speed on the cooling tower efficiency varies greatly and this impact increases as the wind speed increases.
In present experiment, the vapor mixture with different velocities (2m⋅s−1, 4m⋅s−1) and different ethanol mass fraction (0.5%, 1%, 2%, 5%, 10%, 20%, 50%) flew through vertical micro-tube and condensed on the outer tub...
In present experiment, the vapor mixture with different velocities (2m⋅s−1, 4m⋅s−1) and different ethanol mass fraction (0.5%, 1%, 2%, 5%, 10%, 20%, 50%) flew through vertical micro-tube and condensed on the outer tube surface at pressure 31.16kPa, 47.36kPa. The condensation modes were observed by CCD camera, and the characteristics of the heat transfer coefficients versus the vapor-to-surface temperature differences for different experimental conditions were obtained. The condensation heat transfer coefficients of vapor mixture decrease with the vapor concentration increasing. The maximum peak value of heat transfer coefficients, up to 39 kW⋅m−2⋅K1, which was about 3-4 times greater than that of steam, appeared when the ethanol mass fraction was 2%. A heat transfer coefficient correlation including the effects of all the tested parameters is proposed by using the multiple linear least squares method based on the experimental data. The calculated values agreed well with the experimental data and the deviations between them were from −20% to 20%.
Strong wind has a significant impact on the heat radiation of the air-cooling system. In this research, a numerical calculation model of 2×1000MW horizontally arranged air-cooling tower is established to simulate...
Strong wind has a significant impact on the heat radiation of the air-cooling system. In this research, a numerical calculation model of 2×1000MW horizontally arranged air-cooling tower is established to simulate the flow distribution and heat exchanging capability of three different structures-horizontally-arranged indirect air-cooling tower, tower with guide wall outside, and tower with a cross wall inside-under high-speed wind and extreme-speed wind conditions. The result reveals that the structure with the guide wall outside the tower only works under strong wind condition while the structure with cross wall inside shows the anti-wind capability under both high-speed wind and extreme-speed wind conditions.
Visualizations of a specific hydrocarbon fuel in a horizontal tube with 2.0 mm inside diameter were investigated. The experiments were conducted at mass velocity of 213.4, 426.5 and 640.2 kg/ (m2⋅s), diabatic lengths ...
Visualizations of a specific hydrocarbon fuel in a horizontal tube with 2.0 mm inside diameter were investigated. The experiments were conducted at mass velocity of 213.4, 426.5 and 640.2 kg/ (m2⋅s), diabatic lengths of 140, 240 and 420 mm under the pressure from 2.0-2.7 MPa. In the sub-pressure conditions, bubbly, intermittent, stratified-wave, churn and annular flow patterns were observed. The frictional pressure drops were also measured to distinguish the patterns. The development of flow patterns and frictional pressure drop were positively related to the mass velocity and the heat flux. However, the diabatic length of the tube takes an important part in the process. The residence time of the fluid does not only affect the transition of the patterns but influence the composition of the fuel manifested by the fuel color and carbon deposit. The special observational phenomenon was obtained for the supercritical pressure fluid. The flow in the tube became fuzzier and pressure drop changed sharply near the pseudocritical point. The flow boiling heat transfer characteristics of the hydrocarbons were also discussed respectively. The curve of critical heat flux about onset of nucleate boiling was plotted with different mass velocities and diabatic tube lengths. And heat transfer characteristics of supercritical fuel were proved to be better than that in subcritical conditions.
With increasing environmental deterioration and energy demand, studies on new alternative fuels have been attracting more attention. N-pentanol is a five carbon, straight-chain alcohol, which can be produced through n...
详细信息
ISBN:
(纸本)9781627488426
With increasing environmental deterioration and energy demand, studies on new alternative fuels have been attracting more attention. N-pentanol is a five carbon, straight-chain alcohol, which can be produced through natural microbial fermentation and/or engineered microorganisms. It has many advantages over lower carbon alcohols, including higher energy density, lower vapor pressure and better fuel compatibility. In this study, a detailed reaction mechanism of n-pentanol, on the basis of a previously proposed n-butanol mechanism, is generated using the open-source software Reaction Mechanism Generator (RMG). High temperature chemistry of the mechanism was validated against recently published laminar flame speeds and ignition delays. Encouraging results between simulations and experiments were observed under most conditions. Simulations were also conducted using a recently developed n-pentanol oxidation mechanism (NUI model) by Heufer et al. For lean mixtures, the two mechanisms show similar results, while the RMG model yields better predictions for rich mixtures and at an elevated pressure. Reaction pathways and sensitivity analysis reveal the key differences between the two mechanisms in terms of intermediates formed and fuel consumption.
In this work, experiments were conducted on a diesel engine fueled with n-pentanol/diesel blends to examine the effect of n-pentanol addition on the engine performance and emissions. Results show that, the addition of...
详细信息
In this work, experiments were conducted on a diesel engine fueled with n-pentanol/diesel blends to examine the effect of n-pentanol addition on the engine performance and emissions. Results show that, the addition of n-pentanol to diesel increases the brake specific fuel consumption and has little effect on the brake thermal efficiency. Additionally, the emissions of HC, CO and NOx are slightly increased with the increase of n-pentanol in the fuel blends, however, the particulate matter emission is significantly reduced.
Extensive investigations on the flow and heat transfer behavior in SCWR fuel assembly have been undertaken worldwide. However, stability analysis of supercritical water in the sub-channels of tight lattices is still l...
Extensive investigations on the flow and heat transfer behavior in SCWR fuel assembly have been undertaken worldwide. However, stability analysis of supercritical water in the sub-channels of tight lattices is still lacking. In this paper, the flow stability of a fuel bundle channel with square pitches has been analyzed using commercial CFD code-ANSYS Fluent. Typical dynamic instability of Density Wave Oscillation (DWO) has occurred in heated channel containing fluids at supercritical pressure. A further discussion about the impacts of various operational parameters (e.g. power input, system pressure, mass velocity, inlet temperature, etc) shows that the system becomes more stable as system pressure and/or mass flow rate increases. An increase in inlet temperature also has a stabilizing effect on the system.
Experiments were conducted to study pool boiling heat transfer on ultra-light porous metal foam surfaces, with deionized water as working fluid. The metal foams have pore densities from 30 to 60ppi (pores per inch) an...
详细信息
Considering the volumetric reactions and particle surface reactions in an entrained flow gasifier, the non-premixed combustion model based on the wet particles combustion method is adopted to simulate the multi-compon...
详细信息
The emission of trace heavy metals, such as mercury (Hg), from power plants and other industries is a severe environmental problem concerning the public health. The laser-induced plasma technique was employed to measu...
详细信息
暂无评论