Fabrication and testing of phase change heat sink for high power LED

A novel phase change heat sink was fabricated for packaging cooling of high power light emitting diode （LED）. 3D structures as enhanced boiling structure in the evaporation surface were composed of a spiral micro-groove along circumferential direction and radial micro-grooves which were processed by ploughing-extrusion （P-E） and stamping, respectively. Meanwhile, the cycle power of refrigerant was supplied by wick of sintered copper powder on internal surface of phase change heat sink. Operational characteristics were tested under different heat loads and refrigerants. The experimental results show that phase change heat sink is provided with a good heat transfer capability and the temperature of phase change heat sink reaches 86.8 ℃ under input power of 10 W LED at ambient temperature of 20 ℃.

Heat transfer performance testing of a new type of phase change heat sink for high power light emitting diode

In view of the limitations of solid metal heat sink in the heat dissipation of high power light emitting diode （LED）, a kind of miniaturized phase change heat sink is developed for high power LED packaging. First, the fabrication process of miniaturized phase change heat sink is investigated, upon which all parts of the heat sink are fabricated including main-body and end-cover of the heat sink, the formation of three-dimensional boiling structures at the evaporation end, the sintering of the wick, and the encapsulation of high power LED phase change heat sink. Subsequently, with the assistance of the developed testing system, heat transfer performance of the heat sink is tested under the condition of natural convection, upon which the influence of thermal load and working medium on the heat transfer performance is investigated. Finally, the heat transfer performance of the developed miniaturized phase change heat sink is compared with that of metal solid heat sink. Results show that the developed miniaturized phase change heat sink presents much better heat transfer performance over traditional metal solid heat sink, and is suitable for the packaging of high power LED.

Exact analytical solution to three-dimensional phase change heat transfer problems in biological tissues subject to freezing

Analytically solving a three-dimensional （3-D） bioheat transfer problem with phase change during a freezing process is extremely difficult but theoretically important. The moving heat source model and the Green function method are introduced to deal with the cryopreservation process of in vitro biomaterials. Exact solutions for the 3-D temperature transients of tissues under various boundary conditions, such as totally convective cooling, totally fixed temperature cooling and a hybrid between them on tissue surfaces, are obtained. Furthermore, the cryosurgical process in living tissues subject to freezing by a single or multiple cryoprobes is also analytically solved. A closed-form analytical solution to the bioheat phase change process is derived by considering contributions from blood perfusion heat transfer, metabolic heat generation, and heat sink of a cryoprobe. The present method is expected to have significant value for analytically solving complex bioheat transfer problems with phase change.

Enhanced Phase Change Heat Storage of Layered Backfill Body under Different Boundary Conditions

In view of the high temperature problem faced by mining activities,the coordinated mining of ore deposit and geothermal energy is a solution in line with the concept of green mining.The layered backfill body with finned double-pipe heat exchanger continuously exchanges heat with the surrounding thermal environment,which plays an effective role in gathering geothermal energy.In this paper,the heat storage process of each layered backfill body under different boundary conditions is simulated by Fluent.The results show the heat storage characteristic of layered backfill body can be significantly improved by adding fins to the double-pipe heat exchanger.On the whole,the heat storage effect of bottom layer backfill body(BLBB)is the best.The total heat storage capacity of top layer backfill body(TLBB),middle layer backfill body(MLBB)and BLBB with the finned double-pipe heat exchanger is 666.3 kJ,662.2 kJ,1003.0 kJ;1639.0 kJ,1760.8 kJ,1911.2 kJ and 1731.1 kJ,1953.3 kJ,1962.8 kJ respectively at 1 h,8 h and 24 h.This study explores the law of heat storage of layered backfill body under different boundary conditions and also expands the idea for layered backfill body to efficiently accumulate geothermal energy.

Heat Transfer Performance and Structural Optimization of a Novel Micro-channel Heat Sink

With the advent of the 5G era,the design of electronic equipment is developing towards thinness,intelligence and multi-function,which requires higher cooling performance of the equipment.Micro-channel heat sink is promising for the heat dissipation of super-thin electronic equipment.In this study,thermal resistance theoretical model of the micro-channel heat sink was first established.Then,fabrication process of the micro-channel heat sink was introduced.Subsequently,heat transfer performance of the fabricated micro-channel heat sink was tested through the developed testing platform.Results show that the developed micro-channel heat sink has more superior heat dissipation performance over conventional metal solid heat sink and it is well suited for high power LEDs application.Moreover,the micro-channel structures in the heat sink were optimized by orthogonal test.Based on the orthogonal optimization,heat dissipation performance of the micro-channel radiator was further improved.

Optimization of three-dimensional boiling enhancement structure at evaporation surface for high power light emitting diode

A theoretical model of phase change heat sink was established in terms of thermal resistance network. The influence of different parameters on the thermal resistance was analyzed and the crucial impact factors were determined. Subsequently, the forming methods including ploughing-extrusion and stamping method of boiling enhancement structure at evaporation surface were investigated, upon which three-dimensional microgroove structure was fabricated to improve the efficiency of evaporation. Moreover, the crucial parameters related to the fabrication of miniaturized phase change heat sink were optimized. The heat transfer performance of the heat sink was tested. Results show that the developed phase change heat sink has excellent heat transfer performance and is suitable for high power LED applications.

Ka-Band CTDRSS Terminal Technology for Meeting the Needs of Launch Vehicle TT&C

To meet the application requirements for a Ka-band space-based TT&C terminal for a launch vehicle,this paper proposes the implementation scheme of a space-based TT&C terminal,analyzes and solves the miniaturized design of equipment and the key technology for high-efficiency heat dissipation.The phased array antenna test shows that without external heat dissipation measures,the phased array antenna can work for a long time to meet the working requirements of launch vehicle,which has been verified in the LM-8 mission,and has wide engineering application prospects.

The effect of differential temperatures on the latent heat in the nucleation of CdSe quantum dots

This work studied the effect of differential temperatures on the latent heat in the nucleation of CdSe quantum dots（QDs）.The result showed that,by the formula of phase change,with increasing the reaction temperature,the latent heat in the nucleation of QDs reduced.CdSe QDs with the size-dispersion from 2.7 to 3.6 nm were synthesized via oleic acid-paraffin liquid system by controlling the reaction temperature from 180 to 220℃.Synthesized QDs were characterized by UV-vis absorption spectra and X-ray diffraction（XRD）.The result of UV-vis absorption spectra showed that with increasing of reaction temperature,the first absorption peak was red-shifted and the size of QD increased.The result of XRD showed that the synthesized QDs were zinc-blende structure.