小热流测量技术研究

在武器装备型号、航天飞行器的研制、试验以及飞行中,均会使用大量热流传感器进行热流的测量.通过研究热流测量原理及国内外发展现状,论文介绍了一种利用导热形成温差进行小热流测量的方法.

Effects of rotor structure on performance of small size axial flow fans

Small size axial flow fans are used as a cooling component for computers,electronic equipment and other electronic components.With the increasing power of electrical equipment,the demand for lower noise and higher ventilation of cooling fan is also increasing.Traditional methods of improving ventilation by raising the fan's rotation speed causes a decrease in efficiency and an increase in noise.In this paper,different structures of fans were simulated,and as a result,the counter-rotating fan can achieve higher pressure,efficiency and facilitate ventilation in a smaller space.Furthermore,some other conclusions are as follows:(1) Higher pressure rise can be obtained by a counter-rotating fan than by the two-stage rotor fan in the same axial length.Meanwhile,the counter-rotating fan has a broader work scope.(2) The main noise type of the counter-rotating fan is rotating noise;the small peak pulse caused by vortex noise mainly due to the eddy current produced by small eddies.(3) When the distance of counter-rotating fans is smaller than 2 times the chord,the greater distance the greater total pressure of the circum-averages and along the axial direction,the total pressure begin to decline until the distance is three times the chord,so there is an optimal distance between rotors.The simulation results are of important significance to the quantitative analysis and optimization design of the counter-rotating fan.

Experimental investigation of nitrogen flow boiling heat transfer in a single mini-channel

Flow boiling heat transfer of nitrogen at high subcritical pressure conditions in a single vertical mini-channel with the diameter of 2.0 mm was experimentally investigated.The tested mass flux varied from 530 to 830 kg/(m^2·s),the inlet pressure ranged from 630 to 1080 kPa,and the heat flux ranged from 0 to 223.2 kW/m^2.Effects of the mass flux and the inlet pressure on the nitrogen boiling curve were examined.Results showed that within the limited test conditions,the merging of three boiling curves indicates the dominance of nucleate boiling and the inlet pressure has a positive enhancement on heat transfer performance.Three heat transfer trends were identified with increasing heat flux.At low heat fluxes,the heat transfer coefficient increases first and then decreases with vapour quality.At intermediate heat fluxes,the heat transfer coefficient versus the vapour quality presents an inverted"U"shape.At high heat fluxes,a double valley shape was observed and the partial dry-out in intermittent flow and annular flow helps to interpret the phenomenon.The increasing inlet pressure increases the heat transfer coefficient over a wide range of vapour quality until the partial dry-out inception.The lower surface tension and lower latent heat of evaporation enhance the nucleate boiling for higher inlet pressure.A modified experimental correlation(mean absolute error(MAE)=19.3%)was proposed on the basis of the Tran correlation considering both the nucleate boiling and the partial dry-out heat transfer mechanism.

Combination of ribavirin and reduning protects mice against severe pneumonia induced by H1N1 influenza a virus

OBJECTIVE:To investigate the effects of ribavirin administration combined with Reduning in a mouse model of influenza A(H1N1)-induced severe pneumonia.METHODS:Influenza A/Beijing/501/2009(H1N1)-infected C57BL/6 mice were randomly divided into four experimental groups treated with either a mock injection of phosphate-buffered saline(PBS),ribavirin(66.6 mg/kg daily)or Reduning(86.6 mg/kg daily),or a combination of both,for 7 days.Mice were monitored for clinical signs and survival,and body weight was measured daily for 14 days.Virus titer,lung wet-to-dry ratios,pathology and cytokines including interleukin(IL)-6,IL-10,and interferon(IFN)-γwere assayed on different days.RESULTS:In the untreated group injected with phosphate buffer saline,all the mice died of the infection.The survival rate of mice treated with Reduning was only 10%,whereas 100%of the ribavirin-and the combination-treated mice survived.Low lung viral loads indicated that ribavirin significantly inhibited virus replication,whereas Reduning did not.Lung wet-to-dry ratios demonstrated that both ribavirin and Reduning,administered together or separately,reduced acute lung edema compared with results in the untreated group.Pathology analyses also showed that treatment with a combination of both drugs relieved pathological lesions,whereas the single drug treatment did not.Levels of IL-6,IL-10 and IFN-γin mice treated with ribavirin or the combination of both ribavirin and Reduning were all significantly lower than in the untreated group,especially in the combination-treated group.In addition,Reduning administration significantly decreased both IL-6 and IL-10production but had no effect on IFN-γ.CONCLUSION:Due to the synergistic effect of antiviral and antiinflammation,the combination of ribavirin and Reduning could be an effective treatment for severe H1N1 which was considered to be significant to delayed antiviral and drug resistant.

MHD EYRING-PRANDTL FLUID FLOW WITH CONVECTIVE BOUNDARY CONDITIONS IN SMALL INTESTINES

In this paper, we have discussed the food movement in stomach with thermal bound- ary conditions. Eyring-Prandtl fluid model is considered. Formulation of the considered phenomena have been developed for both fixed and moving frame of references. Regular perturbation is used to find the solution of stream function, temperature profile and pressure gradient. Analysis has been carried out for velocity, ＂stream function, temper- ature, pressure gradient and heat transfer＂. Appearance of pressure gradient is quite complicated so to get the expression for pressure rise we have used numerical integra- tion. It is perceived that the velocity close to the channel walls is not same in outlook of the Eyrin^Prandtl fluid parameter taken as fl and Hartman number M. The velocity decreases by increasing β and M.

The synthesis of micro-sized silicon carbide whiskers and the application for heat transfer enhancement

This paper presents a simple and cost-effective method for the production of micro-sized silicon carbide whiskers at high yield and the effect on heat transfer enhancement for the whisker laden fluids. For SiC whisker synthesis, the starting powder mix- ture is obtained by milling short carbon fibers with the white ashes of rice hulls. Calcina：ion in argon, together with the subse- quent purification process, results in a high yield of SiC whiskers, which possess a diameter of 200-400 nm and a length of several tens of microns. The formation of the whiskers is discussed according to VS growth mechanism. Convective heat transfer performance in small channel tubes is then studied for fluid systems mixed with those micro-sized SiC whiskers at different concentrations. The heat transfer coefficient of SiC containing fluid can be significantly improved in comparison to the base fluid.