Heat Analysis and Thermodynamic Effects Part 11 docx

Micro Capillary Pumped Loop for Electronic Cooling 289 The test condition in Fig. 22 was the weak heat dissipation at the condenser. That is, the cooling water was not circulated at the condenser in order to investigate only the normal operating characteristic of the micro CPL by phase change of the working fluid. In the case of the heat pipe with the mechanism of vapor-liquid phase change, the heat pipe shows isothermal characteristics which transfer a lot of heat in small temperature difference between the evaporator and the condenser. Therefore, the normal operating state could be confirmed by measuring the temperature difference between the evaporator and the condenser when small power is input to the evaporator. In Fig. 22, the micro CPL with working fluid shows lower thermal resistance than the micro CPL without working fluid in both cases of total length being 50 mm and 70 mm. This means that the fabricated micro CPL in the present study operates normally through the operating mechanism of vapor- liquid phase change. In the case of the total length of 50 mm, the micro CPL with working fluid shows lower thermal resistance about half of that of the micro CPL without working fluid. In the case of the total length of 70 mm, the micro CPL with working fluid shows lower thermal resistance about a third of that of the micro CPL without working fluid. This means that although the total length is increased from 50 mm to 70 mm, the micro CPL with working fluid operates normally by vapor-liquid phase change. However, the thermal resistance of the micro CPL increased when the total length was changed from 50 mm to 70 mm. 012345 0 5 10 15 20 25 Thermal Resistance ( o C/W) Input Power (W) Micro CPL of 50mm length(without W/F) Micro CPL of 50mm length(with W/F) Micro CPL of 70mm length(without W/F) Micro CPL of 70mm length(with W/F) Fig. 22. Comparison of thermal resistance between the flat plate type micro CPL with working fluid and the one without working fluid Fig. 23 shows the comparison results for the heat transfer rate between micro CPLs with working fluid with total length of 50 mm and 70 mm. In Fig. 23, the input power was not the maximum heat transfer rate; the heat transfer rate supplied to the evaporator was within the wall temperature of 120 °C at the evaporator. In the figure, the heat at the condenser was dissipated to the environment by the circulation of the cooling water. Through this experiment test, it the amount of heat that can be transferred by the fabricated micro CPL within the limited evaporator temperature could be investigated. The heat transfer rate of 7.5 W was obtained within the thermal resistance range of 6.8–19.9 °C/W in the case of the total length of 50 mm. Meanwhile, the heat transfer rate of 6.1 W was obtained within the thermal resistance range of 11.7–19.2 °C/W in the case of the total length of 70 mm. The Heat Analysis and Thermodynamic Effects 290 thermal resistance increased and the heat transfer rate decreased when the total length was increased from 50 mm to 70 mm. The operating mechanism of the flat plate micro CPL developed in the present study was not known in detail. Furthermore, the amount of working fluid and the structural design of the micro CPL were not optimized, therefore further study is needed in the future. 012345678 4 8 12 16 20 24 Thermal Resistance ( o C/W) Input Power (W) Micro CPL of 50mm length Micro CPL of 70mm length Fig. 23. Heat transfer rate according to increasing input power 4.4 Flow visualization of the micro CPL Fig. 24 shows some images obtained by the visual inspection. They were captured on arbitrary time while the micro CPL is operating. Figs. 24(b), (c), and (d) show the fluid flow patterns in the path of the condenser. The fluid flow patterns in the micro CPL were very active during the time the results of Fig. 24 are being obtained. Although any change in the evaporator and the vapor line filled with vapor could not be seen with the naked eye, we Fig. 24. Flow patterns at the condenser: (a) top view of the condenser; (b) (c) plug flow patterns on low or middle heat flux (1–6 W), respectively; (d) annular flow pattern on high heat flux (over 7 W) Micro Capillary Pumped Loop for Electronic Cooling 291 could see the fluid flow phenomenon wherein the liquid and non-condensed vapor flow together. An undesirable phenomenon wherein the vapor transported from the evaporator was condensed on the top and bottom walls in the vapor line was observed with the naked eye. The activity of two-phase flow patterns increases as the input power supplied to the evaporator is increased. The fluid flow pattern was plug flow, wherein the vapor and liquid bridge move in order, in low power (1–3 W) and middle power (4–6 W). The fluid flow pattern changed from being plug flow to annular flow in high power (7–7.5 W). The plug flow in the middle power range has larger velocity than that in the low power range. The micro CPL shows the continuous circulating flow pattern over the entire power range. The liquid drops created on the bottom and top walls at the vapor line should be removed since they may increase the pressure drop in the vapor flow. 5. Commercialization of the MHP and micro CPL The tubular type MHP, which was considered in chapter 3, can be used in any applications and may also be packaged for high heat flux applications. The FPMHP, which was fabricated by Al extrusion, was designed with consideration of capillary force. However, for the purpose of the commercialization of the FPMHP, not only should the capillary force be considered, but also the securing of the inner space. Furthermore, the fabrication cost and fabrication process limit should also be considered. Fig. 24 shows a commercialized model of the FPMHP, which is designed with consideration of the commercial viewpoint. It may be applied to various fields like display, electronic package, automobile, and optic industry. Flat plate micro CPL, which was considered in chapter 5, may be applied to slim mobile electronic devices. The fabrication of a structure similar to design can be obtained. However, for wider application, the fabrication of micro CPL using metal, instead of silicon and glass, is needed. The cost and process of fabrication should be considered for commercialization as well. Fig. 25 shows a micro CPL model fabricated by metal for commercialization. It is composed of only two layers, compared to that considered in chapter 5 which has three layers. The most important factor is reserving the inner space for fluid flow in the case of the commercialized model shown in Fig. 25, which has thickness of less than 1 mm and is composed of only two layers. Fig. 25. FPMHP considering commercialization Heat Analysis and Thermodynamic Effects 292 Fig. 26. Micro CPL considering commercialization 6. Conclusions The characteristics, design, fabrication and thermal performance of MHPs and micro CPLs were investigated. Firstly, MHPs with polygonal cross section applicable to electronic units with thin structure were manufactured and tested. The high productivity and simple manufacturing process were also considered for future applications. The manufactured MHP showed good isothermal property over the total length, and the temperature difference between the evaporator and the condenser was about 4–6 °C. The inclination angle had a slight effect on the thermal performance, and the thermal characteristic was stable from the top heating mode to the bottom heating mode. The effect of the total pipe length on the thermal performance of the triangular MHP was dominant. In the case of the triangular MHP, the overall heat transfer coefficient was enhanced by about 92% when the total length was decreased from 100 mm to 50 mm for 3 W of thermal load. The heat transfer limit of the triangular MHP was 7 W, which is 1.6 times larger than the 4.5 W heat transfer limit of the rectangular MHP. The heat transfer limit, which was the function of the operating temperature, increased when the operating temperature was increased. The maximum heat transfer limit of the triangular MHP was 10 W for the operating temperature of 90 °C. In the present study, the heat transfer limit was 1.7–2.1 times larger than that of Moon (Moon et al., 1999) for the operating temperature of 60–80 °C. The manufactured MHP in the present study exhibited superior heat dissipation capacity and thus can be widely used in integrated electronic units as a cooling module. Secondly, the flat plate type micro CPL with thickness of 1.5 mm was designed, and its fabrication technology was developed through the present study. The micro CPL was designed to have an evaporator, a vapor line, two liquid lines, and a condenser in flat plate shape, ensuring a large space for the vapor flow. In particular, the evaporator was designed to have two-step grooves in order to secure the space for the vapor flow and prevent the backflow of bubbles. The individual fabrication processes technologies for each plate of Micro Capillary Pumped Loop for Electronic Cooling 293 silicon and glass were developed. Particularly, the bonding technology of the fill tube on the glass top plate was completed by the fragment silicon on which the circular type metal bands were deposited. The filling technology of the working fluid into the micro CPL under vacuum condition was completed by the conventional method of filling after vacuuming. Through the performance tests for the fabricated micro CPLs with total length of 50 mm and 70 mm, it was confirmed that micro CPLs operate normally through the phase-change heat transfer of the vapor and liquid. The thermal resistance of the micro CPL increased and the heat transfer rate decreased within the wall temperature of 120 °C at the evaporator when the total length increased from 50 mm to 70 mm. Through the visual study, it was observed that the fluid flow pattern of the micro CPL was plug flow in the low (1–3 W) and middle (4–6 W) power, and annular flow in the high power (over 7 W). The velocity of the fluid flow increased according to the input power. Further study on determining the operating mechanism of the flat plate type micro CPL and optimizing the structural design is needed in the future. 7. References A. Faghri, "Heat Pipe Science and Technology," Talor & Francis, 1995 A. Hoelke, et al., “Analysis of the Heat Transfer Capacity of a Micromachined Loop Heat Pipe,” ASME 1999, Vol. 3, 1999, pp.53-60 B. R. Babin, et al., "Steady-State Modeling and Testing of a Micro Heat Pipe," ASME J. of Heat Transfer , Vol. 112, No. 3, August, pp. 595~601, 1990 D. Wu, et al., "Investigation of the Transient Characteristics of a Micro Heat Pipe," AIAA J. Thermophysics Heat Transfer, 5(2), April, pp. 129~134, 1991 F. M. Gerner, "Flow Limitation in Micro Heat Pipes," AFSOR Final Report, No. F49620-88-6- 0053, Wright-Patterson, AFB, Dayton, OH, 1989 G. P. Peterson, “An Introduction to Heat Pipes: Modeling, Testing and Applications,” Wiley: New York, NY, 1994 H. Xie, et al., “The Use of Heat Pipes in the Cooling of Portables with High Power Packages,” Thermacore Co., Technical Note J. Kirshberg, et al., “Cooling Effect of a MEMS Based Micro Capillary Pumped Loop for Chip-Level Temperature Control,” ASME 2000, MEMS Vol.2, 2000, pp.143-150 J. S. Suh, et al., “Friction in Micro-Channel Flows of a Liquid and Vapor in Trapezoidal and Sinusoidal Grooves,” Int. J. of Heat & Mass Transfer, Vol. 44, 2001, pp.3103-3109 K. S. Kim, S. H. Moon, C. G. Choi, “Cooling Characteristics of Miniature Heat Pipes with Woven-Wired Wick,” 11th Int. Heat Pipe Conf., Japan, Sep. 1999 L. Meyer, et al., “A Silicon-Carbide Micro-Capillary Pumped Loop for Cooling High Power Devices, ” 19th IEEE Semi-Therm Symp., 2003, pp.364-368 M. C. Zaghdoudi, et al., “Theoretical Investigation of Micro Heat Pipes Performance,” 10th Int. Heat Pipe Conf. , Germany, Sep. 21-25, F-9, 1997 R. Hopkins, et al., “Flat Miniature Heat Pipe with Micro Capillary Grooves,” Transaction of the ASME , Vol. 121, pp. 102-109, 1999 S. H. Moon, G. Hwang, H. G. Yun, T. G. Choy, “Operation Performance of Miniature Heat Pipe with Composite Wire Wick,” IMAPS 2001, pp. 207-211, 2001 S. H. Moon, G. Hwang, H. G. Yun, “Improving Thermal Performance of Miniature Heat Pipe for Notebook PC Cooling,” Microelectronic Reliability, Vol.42, No.1, 2002 Heat Analysis and Thermodynamic Effects 294 S. H. Moon, et al., “An Experimental Study on The Performance Limitation of a Micro Heat Pipe with Triangular cross-section,” 11th Int. Heat Pipe Conf., Japan, Sep. 1999 S. H. Moon, et al., “Heat Transport Performance of Micro Heat Pipe with Cross Section of Polygon, ” IMAPAS 2002, Int. Symposium on Microelectronics, Session WP4, 2002 S. H. Moon, et al., “Manufacturing and Thermal Performance of the Flat Plate Micro Heat Pipe,” IMAPS ATW on Thermal Management for High Performance Computing Telcom/Wireless , 2002 T.P. Cotter, "Principles and Prospects for Micro Heat Pipes", Proceedings of the 5th Int. Heat Pipe Conference , 1984. 14 The Investigation of Influence Polyisobutilene Additions to Kerosene at the Efficiency of Combustion V.D. Gaponov 1 , V.K. Chvanov 1 , I.Y. Fatuev 1 , I.N. Borovik 2 , A.G. Vorobiev 2 , A.A. Kozlov 2 , I.A. Lepeshinsky 2 , Istomin E.A. 2 and Reshetnikov V.A. 2 1 OAO “NPO Energomash” 2 Moscow Aviation institute (State Technical University) Russia 1. Introduction Liquid rocket engines reached high efficiency at presence. Next improvement of they energetic, mass and reliabilities characteristics is labor-intensive and high expensive process. It is famous, that addition of polymers to carbonhydogen fuels decrease substantially hydraulic losses at the friction in pipelines and aggregates of engines. Fulfilled in “NPO Energomash” the programme investigation influence of additions polyisobutilene to kerosene at the hydraulic tests exploitated engines was showed, that the decrease of the hydraulic losses may be more 20% [7]. The use of this effect lets or increase pressure in the combustion chamber at constant heat intensivity of the turbine or to increase the resource of the engine at the base decrease heat intensivity of turbine. The question regarding influence addition at the combustion efficiency stated not clear. This investigation for full-sized engines though doesn’t required fabrication new material part, but is completed and expensive process analogically fire tests of the engine. Most likely mechanism influence of addition at combustion efficiency may be pulverization of liquid fuel. The program investigation of this mechanism was developed at department 202 of MAI [3]. This program included two steps. The first step was directed at obtaining characteristics of pulverization one from mixed head liquid rocket engine of small thrust MAI-202K, working at kerosene and gaseous oxygen. Characteristics of pulverization of the mixing head at clean kerosene and kerosene with additions were diagnosed by dispersal of drops, obtained at automatically measurement system. Method dispersal measurement was based at change intensify projecting at the screen reflected from drops laser ray. The second step consist fire tests of engine MAI-202 with seven swirl injectors mixing head and oxygen curtain. Tests were fulfilled at the fire stand of department 202 MAI, at the same regime of work, but at different fuels: clean kerosene and kerosene with additions 0.05- 0.01% polyisobutilen. In the article detail materials are introduced about results as hydraulic, so and fire tests, measured equipment, design of mixing head, characteristics of pipeline. Combustion efficiency was obtained as ratio of experimental value mass flow complex β exp to thermodynamic value mass flow complex β t . Heat Analysis and Thermodynamic Effects 296 2. Composition and structure of test stand Experimental investigation of influence 0.05% polyisobutilene additions to kerosene was fulfilled at the test-bad № 72-2 department 202 MAI for fire tests liquid rocket engines of small thrust (LRE STh) at ecological clean propellants [2]. Hydraulically pipe line of kerosene is selection pipes from stainless steel of variable diameter (4-16mm) total length 8.12m. Pipe line connects kerosene tank with investigated mixing head and consists control valve, filters (net 7 and 70 micro meters), sensors of mass flow, pressure and temperature (Fig. 1). Fig. 1. Kerosene feeding system. Take into account fire danger of mixture drops of kerosene with oxygen, for the obtaining characteristics of pulverization the special drops-trap was designed and fabricated. Scheme of this drops-trap is showed at Fig. 2. The Investigation of Influence Polyisobutilene Additions to Kerosene at the Efficiency of Combustion 297 Fig. 2. Scheme of drops-trap. Drops-trap consists from tube diameter 400mm, upper top with mounted kerosene pipe with injector (or mixing head), two diameterally opposite orifices for registration quality of pulverization, low lid with branch pipe drain of kerosene and system of forced extraction mixture with fan in explosive-protected fulfillment. Vertical position of drops-trap corresponds vertical position of tested engine and guarantees the same influence of gravitation forces at the torch of pulverization. Photos of drops-trap are presented at Fig. 3. Photos of working laser system during test presented at Fig. 4. Heat Analysis and Thermodynamic Effects 298 Fig. 3. Photo of drops-trap. Fig. 4. Laser ray goes through the spray. [...]... temporary or permanent device failure due to strains induced by expansion and contraction Materials with opposite thermal properties, namely contract on heating and expand on cooling are particularly desired to facilitate the possibility to engineer materials with controllable overall negative, zero or 314 Heat Analysis and Thermodynamic Effects positive coefficient of thermal expansion by composite them... dependency 304 Heat Analysis and Thermodynamic Effects 5 Design of LRE of small thrust for fire tests Combustion efficiency of propellant in the combustion chamber depends not only from quality pulverization of injector It depends and from a lot of additional factors: mass flow ratio, number of injectors and scheme its placement at mixing head, combustion chamber pressure, system of inner cooling and others... efficiency of chamber process Main measured values were: stable combustion chamber pressure and mass flow of oxidizer and fuel Entrance O Entrance F Candle of ignition Sensor of pressure Combustion chamber with thermocouples Fig 15 Engine at the working zone of test bench 308 Heat Analysis and Thermodynamic Effects Tests of engine are fulfilled in two stage: • tuned tests (duration < 0.5 sec); • pass... where with help of special software the sizes and concentrations parts of 300 Heat Analysis and Thermodynamic Effects aerosol are calculated Control of laser radiations is realized across computer 9 (for increase of the mobility notebook is used) Transferred bloc of measurer contains half-conductor laser 1(Fig 6) (length wave 650 nm, type of laser KLM-650/20) and field diaphragm 2mm,wich decrease diameter... the canceling of the compressive stress 316 Raman Intensity /Arbitr Units Heat Analysis and Thermodynamic Effects 10000 8000 6000 b 4000 2000 a 0 200 400 600 800 1000 W a v e n u m b e r /c m 1200 -1 Raman Intensity/Arbitr.Units Fig 2 Raman spectra of ZrW2O8 synthesized with 800 W laser power and different scan speed: (a) 6 mm/s and (b) 1 mm/s 50000 40000 30000 20000 b 10000 a 0 200 400 600 800 W avenumber/cm... conductive materials using LRS Particular attention will be paid to the unique microstructures, special or controlled phase formation and related superior properties of the materials synthesized by LRS which may not be obtained by other methods The oriented crystalline growth dictated by heat transfer directions and the particular phases formed at high temperatures in the molten pool and pressures induced during... speed and cooling environments are shown to affect the laser rapid solidification rate and hence the pressures induced With the help of experimental results, the influence of these factors on the cooling rate, pressures induced and the phases of final products are revealed 2 Synthesis of negative thermal expansion materials by LRS It is well known that the vast majority of materials expand on heating and. .. contains field diaphragm and, some times, collimator forming probe-rays and sizes of measured volume Bloc of entranced optics contains Furie-linses, having focus-distance 50-100 cm and light diameter 10-20 cm Focus distance of lenses, entranced in collimator, is changed from 10mm till 20cm.Because of small sizes of parts(2-10micron )and big distances(till 2m) diameter most information part of spatial specter,... rascheta ZhRD Moskva, «Vysshaja shkola», 1975 312 Heat Analysis and Thermodynamic Effects [7] Chvanov V.K., Fatuev I Ju., Gaponov V.D., Sternin L Uluchshenie harakteristik raketnositelej pri dobavlenii k toplivu vysokomolekuljarnyh prisadok Dvigatel', № 6 (42), 2005 15 Synthesis of Novel Materials by Laser Rapid Solidification E J Liang, J Zhang and M J Chao Zhengzhou University China 1 Introduction... require expensive metal alkoxide precursors, great care in mixing the precursors to 318 Heat Analysis and Thermodynamic Effects 0.9 500W Mass Ratio (/) 0.8 600W 0.7 0.6 0.5 0.4 1 2 3 4 Scanning Velocity/ (mm/s) Fig 5 The mass ratio of the γ to α phase at different scan speeds achieve the desired stoichiometry and tedious pretreatment before the final calcinating step Due to the narrow composition . Heat Analysis and Thermodynamic Effects 294 S. H. Moon, et al., “An Experimental Study on The Performance Limitation of a Micro Heat Pipe with Triangular cross-section,” 11th Int. Heat. Meanwhile, the heat transfer rate of 6.1 W was obtained within the thermal resistance range of 11. 7–19.2 °C/W in the case of the total length of 70 mm. The Heat Analysis and Thermodynamic Effects. β exp to thermodynamic value mass flow complex β t . Heat Analysis and Thermodynamic Effects 296 2. Composition and structure of test stand Experimental investigation of influence 0.05% polyisobutilene