Cooling Efficiency of Laminar Cooling System for Plate Mill

Heat transfer was researched from a perspective of the industry application. On the basis of the first law of thermodynamics, the cooling efficiency was deduced from the change of enthalpy inside hot plate. The relationship between the cooling efficiency and its influencing parameters was regressed from plenty of data collected from the worksite and discussed in detail. The temperature profiles resulting from the online model and the model modified by regressed formulas were presented and compared. The results indicated that the control accuracy of the modified model was increased obviously.

Laser Cooling Using Anti-Stokes Fluorescence in Yb^(3+)-Doped Fluorozirconate Glasses

The fluorozirconate glasses ZBLANP( ZrF\-4-BaF\-2-LaF\-3-AlF\-3-NaF-PbF\-2) doped with different Yb\+ 3+ concentration were prepared. The Raman spectra and absorption spectra are measured to substantiate the existence of phonon-assisted emission. After analyzing the normalized absorption spectra of samples with different Yb\+ 3+-doped concentration, we calculated the maximum cooling effect in the 3 wt% Yb\+ 3+-doped sample pumped at 1 012.5 nm. The corresponding cooling capability is about -4.09 ℃/W and the cooling efficiency reaches 1.76%.

Numerical Simulation Study on Cooling Characteristics of a New Type of Film Hole

A new type of film cooling hole with micro groove structure is presented in this paper.Based on the finite volume method and the Realizable k-εmodel,the film cooling process of the hole in a flat plate structure is simulated.The surface temperature distribution and film cooling effect of different film cooling holes were analyzed.The effects of micro-groove structure on wall attachment and cooling efficiency of jet were discussed.The results show that under the same conditions,the transverse coverage width and overall protective area of the new micro-groove holes are larger than those of the ordinary cylindrical holes and special-shaped holes.Compared with ordinary holes,the new micro-groove holes can better form the film covering on the surface and enhance the overall film cooling efficiency of the wall.For example,when the blowing ratio M=1.5,the effective coverage ratio of micro-groove holes is 1.5 times the dustpan holes and is 8 times the traditional cylindrical holes.It provides reference data and experience rules for the optimization and selection of advanced cooling structure of high performance aero-gas engine hot-end components.

Two-dimensional film cooling over a flat plate in hypersonic flow

Film cooling,as one efficient active cooling method,will hopefully be used in‘hypersonic vehicles’in the future.The hypersonic vehicle's surface is more likely a flat plate than a blunt body,so the cooling characteristics of two-dimensional(2-D)film cooling over a flat plate in hypersonic flow are studied using both theoretical analysis and numerical methods.A cooling efficiency calculation formula under a hypersonic condition is obtained and the numerical results show that it has great predicting ability.Compared with the low-speed main-flow condition,several differences exist in the hypersonic main-flow condition.A parameter called the‘generalized turbulent mixing coefficient’is introduced and its approximate value range is given based on numerical results.

Bending performance analysis on YBCO cable with high flexibility

In order to utilize high‐temperature superconducting Yttrium Barium Copper Oxide(YBCO)tapes to develop superconducting cables for high magnet field applications,it is critical to ensure the stable operation of the YBCO cable under challenging mechanical and thermal conditions.A new type of cable featuring the winding of YBCO and copper tapes around a spiral stainless steel tube has been proposed to increase flexibility and cooling.Experiments are performed to confirm that its critical current varies with the bending diameter.The cables wound with nine YBCO tapes in three layers show a critical current degradation of less than 5%for a bending diameter of 30 mm.The performance of the cable degrades as the number of wound layers increases.The critical current degradation of cable specimens wound from 15 tapes in five layers reached approximately 12%for a bending diameter of 30 mm.In addition,when compared to traditional CORC cable specimens,the developed cable specimens show better‐bending flexibility and achieve a lower critical bending diameter.The finite element models show that the higher elasticity coefficient and lower plasticity of the stainless steel spiral tube results in a lower strain on the YBCO tapes of the HFRC cable than that of the CORC cable,and the maximum strain on the YBCO tapes of the HFRC cable was only about 10%of that of the CORC cable.Therefore,it is less likely that the YBCO tape in this type of cable will reach the irreversible strain limit during bending,resulting in a degradation in current carrying performance.Furthermore,the cooling efficiency can be improved by flowing the cooling medium inside the central core,which can significantly improve its thermal stability.These advantages indicate the possibility of using it in future high‐field magnets with high current carrying capacity at fields greater than 15 T.

Thermal Management of Electrified Propulsion System for Low-Carbon Vehicles

An overview of current thermal challenges in transport electrification is introduced in order to underpin the research developments and trends of recent thermal management techniques.Currently,explorations of intelligent thermal management and control strategies prevail among car manufacturers in the context of climate change and global warming impacts.Therefore,major cutting-edge systematic approaches in electrified powertrain are summarized in the first place.In particular,the important role of heating,ventilation and air-condition system(HVAC)is emphasised.The trends in developing efficient HVAC system for future electrified powertrain are analysed.Then electric machine efficiency is under spotlight which could be improved by introducing new thermal management techniques and strengthening the efforts of driveline integrations.The demanded integration efforts are expected to provide better value per volume,or more power output/torque per unit with smaller form factor.Driven by demands,major thermal issues of high-power density machines are raised including the comprehensive understanding of thermal path,and multiphysics challenges are addressed whilst embedding power electronic semiconductors,non-isotropic electromagnetic materials and thermal insulation materials.Last but not least,the present review has listed several typical cooling techniques such as liquid cooling jacket,impingement/spray cooling and immersion cooling that could be applied to facilitate the development of integrated electric machine,and a mechanic-electric-thermal holistic approach is suggested at early design phase.Conclusively,a brief summary of the emerging new cooling techniques is presented and the keys to a successful integration are concluded.