Fundamentals of Heat Pipes

فهرست عناوین اصلی در این پاورپوینت

فهرست عناوین اصلی در این پاورپوینت

● Fundamentals of Heat Pipes
● Introduction
● Basic Components
● Advantages of Heat Pipes
● Thermodynamic Cycle
● Ideal Thermodynamic Cycle
● Heat Pipe Applications
● Types of Heat Pipes
● Main Heat Transfer Limitations
● Heat Transfer Limitations
● Capillary Limit
● Boiling Limit
● Resistance Network
● Heat Pipe Resistance
● The Wick and its Design
● Capillary Pressure
● Wick Design
● Choosing the Working Fluid
● Container Design
● Heat pipe Compatibility
● Heat Sink/Source Interface
● Heat Pipes in Electronics Cooling
● Current Research in Electronics Cooling
● References

نوع زبان: انگلیسی حجم: 1.88 مگا بایت
نوع فایل: اسلاید پاورپوینت تعداد اسلایدها: 67 صفحه
سطح مطلب: نامشخص پسوند فایل: ppt
گروه موضوعی: زمان استخراج مطلب: 2019/05/10 01:20:27

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., heat, pipe, evaporator, limit, ۱۹۹۵, flux, capillary, faghirus, condenser, cool, vapor,

توجه: این مطلب در تاریخ 2019/05/10 01:20:27 به صورت خودکار از فضای وب آشکار توسط موتور جستجوی پاورپوینت جمع آوری شده است و در صورت اعلام عدم رضایت تهیه کننده ی آن، طبق قوانین سایت از روی وب گاه حذف خواهد شد. این مطلب از وب سایت زیر استخراج شده است و مسئولیت انتشار آن با منبع اصلی است.

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عبارات پرتکرار و مهم در این اسلاید عبارتند از: ., heat, pipe, evaporator, limit, ۱۹۹۵, flux, capillary, faghirus, condenser, cool, vapor,

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fundamentals of heat pipes with applications to electronics cooling widah saied introduction things to be discussed basic components advantages ideal thermodynamic cycle applications types heat transfer limitations resistance network wick design choosing the working fluid container design heat pipes in electronics cooling current research in electronics cooling basic components condenser evaporator wick http images tech orangecontainer small.png adiabatic section advantages of heat pipes very high thermal conductivity. less temperature difference needed to transport heat than traditional materials thermal conductivity up to ۹ times greater than copper for the same size faghiri ۱۹۹۵ resulting in low thermal resistance. peterson ۱۹۹۴ power flattening. a constant condenser heat flux can be maintained while the evaporator experiences variable heat fluxes. faghiri ۱۹۹۵ efficient transport of concentrated heat. faghiri ۱۹۹۵ advantages of heat pipes temperature control. the evaporator and condenser temperature can remain nearly constant at tsat while heat flux into the evaporator may vary faghiri ۱۹۹۵ . geometry control. the condenser and evaporator can have different areas to fit variable area spaces faghiri ۱۹۹۵ . high heat flux inputs can be dissipated with low heat flux outputs only using natural or forced convection peterson ۱۹۹۴ . thermodynamic cycle ۱ ۲ heat applied to evaporator through external sources vaporizes working fluid to a saturated ۲’ or superheated ۲ vapor. ۲ ۳ vapor pressure drives vapor through adiabatic section to condenser. ۳ ۴ vapor condenses releasing heat to a heat sink. ۴ ۱ capillary pressure created by menisci in wick pumps condensed fluid into evaporator section. process starts over. faghiri ۱۹۹۵ ideal thermodynamic cycle faghiri ۱۹۹۵ heat pipe applications electronics cooling small high performance components cause high heat fluxes and high heat dissipation demands. used to cool transistors and high density semiconductors. aerospace cool satellite solar array as well as shuttle leading edge during reentry. heat exchangers power industries use heat pipe heat exchangers as air heaters on boilers. other applications production tools medicine and human body temperature control engines and automotive industry. faghiri ۱۹۹۵ types of heat pipes thermosyphon gravity assisted wickless heat pipe. gravity is used to force the condensate back into the evaporator. therefore condenser must be above the evaporator in a gravity field. leading edge placed in the leading edge of hypersonic vehicles to cool high heat fluxes near the wing leading edge. faghiri ۱۹۹۵ rotating and revolving condensate returned to the evaporator through centrifugal force. no capillary wicks required. used to cool turbine components and armatures for electric motors. cryogenic low temperature heat pipe. used to cool optical instruments in space. peterson ۱۹۹۴ types of heat pipes flat plate much like traditional cylindrical heat pipes but are rectangular. used to cool and flatten temperatures of semiconductor or transistor packages assembled in arrays on the top of the heat pipe. faghiri ۱۹۹۵ types of heat pipes micro heat pipes small heat pipes that are noncircular and use angled corners as liquid arteries. characterized by the equation rc rh۱ where rc is the capillary radius and rh is the hydraulic radius of the flow channel. employed in cooling semiconductors improve thermal control laser diodes photovoltaic cells medical devices. peterson ۱۹۹۴ types of heat pipes variable conductance allows variable heat fluxes into the evaporator while evaporator temperature remains constant by pushing a non condensable gas into the condenser when heat fluxes are low and moving the gas out of the condenser when heat fluxes are high thereby increasing condenser surface area. they come in various forms like excess liquid or gas loaded form. the gas loaded form is shown below. used in electronics cooling. faghiri ۱۹۹۵ types of heat pipes capillary pumped loop heat pipe for systems where the heat fluxes are very high or where the heat from the heat source needs to be moved far away. in the loop heat pipe the vapor travels around in a loop where it condenses and returns to the evaporator. used in electronics cooling. faghiri ۱۹۹۵ main heat transfer limitations capillary limit occurs when the capillary pressure is too low to provide enough liquid to the evaporator from the condenser. leads to dryout in the evaporator. dryout prevents the thermodynamic cycle from continuing and the heat pipe no longer functions properly. boiling limit occurs when the radial heat flux into the heat pipe causes the liquid in the wick to boil and evaporate causing dryout. faghiri ۱۹۹۵ heat transfer limitations entrainment limit at high vapor velocities droplets of liquid in the wick are torn from the wick and sent into the vapor. results in dryout. sonic limit occurs when the vapor velocity reaches sonic speed at the evaporator and any increase in pressure difference will not speed up the flow like choked flow in converging diverging nozzle. usually occurs during startup of heat pipe. viscous limit at low temperatures the vapor pressure difference between the condenser and the evaporator may not be enough to overcome viscous forces. the vapor from the evaporator doesn’t move to the condenser and the thermodynamic cycle doesn’t occur. faghiri ۱۹۹۵ heat transfer limitations each limit has its own particular range in which it is important. however in practical operation the capillary and boiling limits are the most important. the figure below is an example of these ranges. peterson ۱۹۹۴ heat transfer limitations actual performance curves capillary limit and boiling limit are the limiting factors. http www.electronics resources ec articles sep۹۶ sep۹۶ ۲.htm capillary limit for a heat pipe to function properly the capillary pressure must be greater or equal to the sum of the pressure drops due to inertial viscous and hydrostatic forces as well as pressure gradients. if it is not then the working fluid is not supplied rapidly enough to the evaporator to compensate for the liquid loss through vaporization. if this occurs there is dryout in the evaporator. peterson ۱۹۹۴ capillary limit equation for minimum capillary pressure peterson ۱۹۹۴ boiling limit the boiling limit is due to excessive radial heat flux all the other limits …

کلمات کلیدی پرکاربرد در این اسلاید پاورپوینت: ., heat, pipe, evaporator, limit, ۱۹۹۵, flux, capillary, faghirus, condenser, cool, vapor,

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