Boiling heat transfer characteristics of nanofluids in a flat heat pipe evaporator with micro-grooved heating surface

An experimental study was performed to understand the nucleate boiling heat transfer of water–CuO nanoparticles suspension (nanofluids) at different operating pressures and different nanoparticle mass concentrations. The experimental apparatus is a miniature flat heat pipe (MFHP) with micro-grooved heat transfer surface of its evaporator. The experimental results indicate that the operating pressure has great influence on the nucleate boiling characteristics in the MFHP evaporator. The heat transfer coefficient and the critical heat flux (CHF) of nanofluids increase greatly with decreasing pressure as compared with those of water. The heat transfer coefficient and the CHF of nanofluids can increase about 25% and 50%, respectively, at atmospheric pressure whereas about 100% and 150%, respectively, at the pressure of 7.4 kPa. Nanoparticle mass concentration also has significant influence on the boiling heat transfer and the CHF of nanofluids. The heat transfer coefficient and the CHF increase slowly with the increase of the nanoparticle mass concentration at low concentration conditions. However, when the nanoparticle mass concentration is over 1.0 wt%, the CHF enhancement is close to a constant number and the heat transfer coefficient deteriorates. There exists an optimum mass concentration for nanofluids which corresponds to the maximum heat transfer enhancement and this optimum mass concentration is 1.0 wt% at all test pressures. The experiment confirmed that the boiling heat transfer characteristics of the MFHP evaporator can evidently be strengthened by using water/CuO nanofluids.     

Laser produced plasma: A pumping source for cadmium photo-ionization laser

We report laser oscillations in Cd II on 4d ⁹5s ^{2 2} D _5/2 − 4d ¹⁰5p ² P _3/2 transition at 441.6 nm using laser produced tungsten plasma as a pumping source. Mach Zehnder interferometer is used to measure electron density. Design and working of the crossed heat pipe used in the studies is discussed.     

热管式吸附床制冷性能的实验研究

利用高效热管作为吸附床的传热部件,有效地提高了船用柴油机废气的热量回收。本文将热管式吸附床与传统的壳管式吸附床进行了性能对比。同时,选择氯化钙-氨作为吸附工质对,通过实验测定解吸、吸附过程的变化情况。本文的研究结果表明,采用热管式吸附床使得初始解吸和吸附速率有明显提高,从而有效缩短解吸和吸附周期,并能有效提高系统的SCP和COP。     

Effective thermal conductivity of granulated two-phase systems at interstitial air pressures

Considering the htermal conduction through molecular collisions an expression for the effective thermal conductivityλ _e of loose and granular two-phase materials at different interstitial air pressure has been derived. The dependence ofλ _e on pore and particle sizes, characteristic pressure and radiative heat transfer is also discussed. Calculated values ofλ _e of glass beads and loose building materials are compared with reported results.     

4度循环图的不交路及k-宽直径

研究了4度循环图,构造出其任意两点之间的四条内部点不交路,并且给出其宽直径的一个较好的上界。     

关于3连通图的容错直径和宽直径

容错直径和宽直径是度量网络可靠性和有效性的重要参数．对任意k连通图，它的容错直径Dk不超过宽直径dk,本证明：当D2=2时，d3≤max{D， l，2D3-2}；当D2≥3时，d3≤(D2-1)[2(D2-1)(D3-1)-D2-2] 1．     

Internal Flow Patterns on Heat Transfer Performance of a Closed-Loop Oscillating Heat Pipe with Check Valves

This article presents the experimental results of an evaluation of the influence of internal flow patterns on the heat transfer performance of a closed-loop oscillating heat pipe with check valves. It was found that the internal flow patterns could be classified according to four flow patterns: dispersed bubble flow, bubble flow, slug flow, and annular flow, respectively. The main regime of each flow pattern can be determined from a flow pattern map. The map can be used to predict the trend of the heat transfer rate in the closed-loop oscillating heat pipe with check valves.     

To breathe or not to breathe—That is the question: An investigation of speech breathing kinematics in world class Shakespearean actors

Anteroposterior diameter changes of the rib cage and abdomen were recorded during respiratory and speaking activities in four adult subjects, three men and one woman, all of whom had extensive dramatic training and experience and were earning their livelihood as professional actors. Data were charted to solve for lung volume, and volume displacements of the rib cage and abdomen. The more vigorous and louder monologue performances by the professional actor subjects differed from other speaking and reading activities in the following parameters of lung volume, separate volumes, relative volume contributions, and the frequent use of respiratory phase transitions. Novice actor subjects' monologue performances are compared to the monologue performances of the professional actor subjects.     

Submicroscopic analysis of tracks in mica

Tracks of 49 MeV ³⁵Cl ions in muscovite mica were analyzed by transmission electron microscopy up to 10 Å resolution applying the track replica method. The enlargement of the track diameter is measured as a function of etching time. The track shape evolution shows circular tracks for very short etching times. By increasing the etching time the tracks gradually become ovals. For longer etching times, tracks show the characteristic rhombic shape of the bulk region. A non monotonous decrease of the track velocity vs. radius is reported. Formation of a low velocity shell in the intermediate region between the central amorphous zone and the non-perturbed crystalline lattice is suggested.     

高温及超高温热管的启动特性和传热极限

根据局部高温、高热流加热等特殊场合的需求,设计、加工了钠高温热管及锂超高温热管,并对热管的启动和极限特性进行了研究。高温及超高温热管能够顺利启动,但启动时应注意可能到来的声速传热极限。端部加热启动时,端部附近管体部分会形成一段等效的加热段,可以将工质从启动时的固体状态到全部熔化形成相变传热及流动循环的时间确定为启动时间。热管的传热极限特性表明,超高温热管应工作在更高的温度和更大的热流密度。热管的结构和工艺优化有利于启动和运行。