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Study On Principle And Experiment Of Micro-evaporation Throttling Cooling Heat Sink Of High Power Laser Diode Array

Posted on:2016-01-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:S Q FanFull Text:PDF
GTID:1222330503452347Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
MMR heat sink is a miniature refrigeration device which is made based on the theory of steam compression, throttle evaporation and phase change heat absorption. It contains miniature compressor, air cooled condense, throttling element, micro evaporation chamber as well as other parts. It is applied to the heat dissipation of electronic components of small heating area and high heat flux density, especially the high power Laser Diode. Compared with the traditional Microchannel liquid-cooled heat sink, it utilizes the latent heat of phase change for coolant, and high heat exchange amount can be achieved with little coolant and low flow of the coolant as well as high heat density. Coolant temperature remains the same during the process of phase change decalescence, whichovercomes the adverse factors such as change of light power and wavelength drift due to the refrigeration effect difference of LD arrays in different luminous points which are caused by the difference temperature at the entrance and exit for the traditional liquid-cooled microchannel heat sink.Meanwhile it enjoys the following advantages such as lower cooling temperature, simpler cooling system structure, and smaller volume of cooling system as well as lower total energy dissipation. With the development of high power laser technology, LD with higher power and higher heat flux density is developed. Therefore, the traditional single-phase heat transfer microchannel cooling system cannot meet the requirements.Therefore, in recent years, the research of miniature refrigerationwhich usesphase change heat transferleads to the extensive concern of foreign related research institutions and companies andlots of significant research results have been reported.International study of MMR can be divided into theoretical simulation study, miniature throttling element form, refrigerant working medium, miniature refrigeration evaporation cavity structure study, micro refrigeration systems research for miniature compressor parts, as well as different thermal load experiment technology research of the high-power LD high heat flow.At present, the domestic research is in the initial stage, which focused on theoretical simulation, phase change cooling ways, micro evaporation cavity structure, etc.Theory research mainly focus on the mechanism of vapor compression refrigeration, phase change characteristics of cooling agent in the microchannel, single and double phases flow characteristics in the microchannel, and numerical simulation of heat sink temperature distribution, etc.;Throttling element form includes a variety of forms such as throttle valve, capillary throttling and porous jet throttling. Researches have been conducted on the following aspects, a single cavity simple structure, multi microchannel evaporation cavity, evaporation cavity processing craft and micro evaporation cavity material; etc as far as the structure of micro evaporation cavity is concerned. A small amount of researches have been conducted for dc micro compressor and condenser cooling system.Due to difference between micro cavity refrigerant and the cooling water, the current research is not perfect because of the complex phase change and many factors that affect its heat transfer.In addition, sealing and refrigerant filling process need to be considered during its process of working. Therefore, different from the widely used heat sink products of high power laser diode, no heat sink products for microchannel evaporation cavity have been sold or used in both home and abroad.Effective heat dissipation of high power laser diode is the premise and fundamental for widely use of LD in military, industrial, scientific research, medical and other important areas of mass popularization and application.Since 1962, researchers like R.N.Hall applied the diffusion technology and developed the first GaAs LD with homojunction, the research of its heat dissipation has been a classic in the field of academic research.As the mature development of LD technology and the improvement of the optical power, the heat-dissipating methods undergo the following process, conventional conduction cooling, refrigeration cooling of TEC, regular channel water, silicon microchannel and copper microchannel cooling way. It leads to the endless research achievements.In domestic research institutions, in 1998 Professor Dai from the key laboratory of optical engineering in Chongqing Normal University, successfully developed silicon microchannel water cold heat sink for the first time, which made our country become one of five countries to master the technology.In 2010, the author in the same laboratory realized the deficiency of the microchannel liquid coolant and the limit of heat, innovatively put forward evaporation cooling method and the research planin view of the high-power LD heat dissipation based on the limited documents and reports abroad. The author applied for 2011 national natural science fund project named Principle and experimental research forMicrochannel refrigeration packaging components with high power semiconductor laser arrayand got the fund support(No: 61008059). In 2014,after the apply for the fund of national project, the author applied for the further research on the project of forefront of technology project of Chongqing Science and Technology Commission named The design of high power laser diode micro evaporation chamber refrigeration components manufacture and research on characteristic parameters and received the fund as well(No: cstc2014jcyjA70005).Based on the basis of the above two projects, the article mainly adopts the combination of theoretical analysis, numerical simulation and experimental method to study the phase change cooling principle of the high power LD miniature refrigeration system. Numerical simulation is conducted for the temperature distribution of evaporation chamber heat sink cooling. The micro evaporation cavity structure with microchannel is designed. Researches have been done on the evaporation cavity production processing technology, packaging technology, welding technology between laser diode and the heat sink. The design and experiment for refrigeration system of microchannel has completed with the following aspects:①According to the second law of thermodynamics, based on principle of the basic theory of single-stage vapor compression refrigeration, this paper analyzes the single stage refrigeration system composition, system pressure –specific enthalpy, temperature- the entropy diagram. Calculation model and system performance parameterscalculation model has been set up based on thermodynamic performance of the miniaturized expansion valve, compressor, evaporator, different parts of condensers.②According to the heating characteristics of high-power LD, heat flux, the author designs a microchannel evaporation module with five layers including capillary throttling components and micro evaporation cavity. The numerical simulation of finite element method(fem) cooling dissipation is conducted. The temperature distribution and heat flow density is got with the LD thermal load is 60 watt. The design shows that cooling for the LD with the heat load of 6o watt can be achieved.③the experiment studies the production technology, micro evaporation chamber adopts 5 floors oxygen-free copper as a basic material evaporation cavity, the study of micro evaporation chamber of the cutting process, anaerobic copper multilayer welding process, smooth surface corrosion process, LD welding process as well as the refrigeration system components assembly process.④Lots of researches and experimentswere carried out by using steam resistance as LD heat source.Experiments have been conducted on the following microchannels : The single bent capillary micro evaporation cavity with the mechanical carving of three layers, the micro evaporation cavity of three layer with multi channels, the micro evaporation cavity of five layers with multi channels.With the observation of the boiling and evaporation in microchannel, experimental process, phenomena and data are recorded in detail. The difficulties and deficiencies appearing in the test have been discussed carefully, and the result was relatively satisfied with the structure and samples of micro evaporation cavity.⑤Evaporation experiments have been conducted with the use of R22,R134 a and mixed working medium and experimental data has been gained. The experiment of luminous characteristics of LD under different rotational speed has been conducted and the relationship between different rotate speed and output parameters, wavelength and refrigeration efficiency.
Keywords/Search Tags:high power laser diode, Micro evaporationcooler, Heat sink.throttle evaporation, phase change cooling
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