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heat transfer انتقال الحرارة !! موضوع جديد عسى ان يكون مفيد

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    الصورة الرمزية حسن هادي
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    heat transfer انتقال الحرارة !! موضوع جديد عسى ان يكون مفيد

    الى جميع الاخوة هذا الموضوع في مجال علم انتقال اتلحرارة لعله يكون مفيدا لاخواننا الطلبة والباحثين


    Heat Transfer

    The transfer of heat is normally from a high temperature object to a lower temperature object. Heat transfer changes the internal energy of both systems involved according to the First Law of Thermodynamics.

    Heat transfer from a cold to a hotter regionRadiation cooling timeIndex HyperPhysics***** Thermodynamics R NaveGo Back




    Heat Conduction

    Conduction is heat transfer by means of molecular agitation within a material without any motion of the material as a whole. If one end of a metal rod is at a higher temperature, then energy will be transferred down the rod toward the colder end because the higher speed particles will collide with the slower ones with a net transfer of energy to the slower ones. For heat transfer between two plane surfaces, such as heat loss through the wall of a house, the rate of conduction heat transfer is:
    Calculation


    = heat transferred in time == thermal conductivity of the barrier= area= temperature= thickness of barrierThermal conductivity tableDiscussion of thermal conductivityHome heat loss by conduction.Index

    Heat transfer concepts

    Heat transfer examples HyperPhysics***** Thermodynamics R NaveGo Back




    Heat Convection

    Convection is heat transfer by mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it. Convection above a hot surface occurs because hot air expands, becomes less dense, and rises (see Ideal Gas Law). Hot water is likewise less dense than cold water and rises, causing convection currents which transport energy.
    Convection can also lead to circulation in a liquid, as in the heating of a pot of water over a flame. Heated water expands and becomes more buoyant. Cooler, more dense water near the surface descends and patterns of circulation can be formed, though they will not be as regular as suggested in the drawing.
    Convection cells are visible in the heated cooking oil in the pot at left. Heating the oil produces changes in the index of refraction of the oil, making the cell boundaries visible. Circulation patterns form, and presumably the wall-like structures visible are the boundaries between the circulation patterns.
    Convection is thought to play a major role in transporting energy from the center of the Sun to the surface, and in movements of the hot magma beneath the surface of the earth. The visible surface of the Sun (the photosphere) has a granular appearance with a typical dimension of a granule being 1000 kilometers. The image at right is from the NASA Solar Physics website and is credited to G. Scharmer and the Swedish Vacuum Solar Telescope. The granules are described as convection cells which transport heat from the interior of the Sun to the surface.
    In ordinary heat transfer on the Earth, it is difficult to quantify the effects of convection since it inherently depends upon small nonuniformities in an otherwise fairly homogeneous medium. In modeling things like the cooling of the human body, we usually just lump it in with conduction.
    Index

    Heat transfer concepts

    Heat transfer examples HyperPhysics***** Thermodynamics R NaveGo Back

  2. [2]
    حسن هادي
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    حسن هادي
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    Heat transfer

    For your exams you need to know the three kinds of energy transfer called heat transfer.
    Thermal energy (heat energy) moves from one place to another because of the difference in temperature between them. The energy transfer is always from hot to cold and it can happen in three ways:
    Conduction

    In conduction energy is passed from atom to atom. It is the most important type of heat transfer in solids.
    On Error Resume Next flash2Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.2"))) flash3Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.3"))) flash4Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.4"))) flash5Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.5"))) flash6Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.6"))) flash7Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.7"))) flash8Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.8"))) To view this piece of media, you will need an up-to-date version of the Macromedia Flash Plug-in. You can quickly download it from hereConvection

    In convection, energy is carried around by atoms or molecules - so it only happens in liquids and gases.
    On Error Resume Next flash2Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.2"))) flash3Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.3"))) flash4Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.4"))) flash5Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.5"))) flash6Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.6"))) flash7Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.7"))) flash8Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.8"))) To view this piece of media, you will need an up-to-date version of the Macromedia Flash Plug-in. You can quickly download it from hereRadiation

    In radiation, radiant energy (infra-red) is given off by a hot object and absorbed by another object.
    On Error Resume Next flash2Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.2"))) flash3Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.3"))) flash4Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.4"))) flash5Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.5"))) flash6Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.6"))) flash7Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.7"))) flash8Installed = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFl ash.8"))) To view this piece of media, you will need an up-to-date version of the Macromedia Flash Plug-in. You can quickly download it from herePrevious | Next http://www.bbc.co.uk/gcsebitesizeIntro 1 2 3 4 5 6 7 8 Print

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    طرق انتقال الحرارة

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    حسن هادي
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    http://www.physchem.co.za/Heat/Transfer.htm
    موقع في هذا المجال

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    حسن هادي
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    Conduction:Regions with greater molecular kinetic energy will pass their thermal energy to regions with less molecular energy through direct molecular collisions, a process known as conduction. In metals, a significant portion of the transported thermal energy is also carried by conduction-band electrons. Convection:When heat conducts into a static fluid it leads to a local volumetric expansion. As a result of gravity-induced pressure gradients, the expanded fluid parcel becomes buoyant and displaces, thereby transporting heat by fluid motion (i.e. convection) in addition to conduction. Such heat-induced fluid motion in initially static fluids is known as free convection. For cases where the fluid is already in motion, heat conducted into the fluid will be transported away chiefly by fluid convection. These cases, known as forced convection, require a pressure gradient to drive the fluid motion, as opposed to a gravity gradient to induce motion through buoyancy. Radiation:All materials radiate thermal energy in amounts determined by their temperature, where the energy is carried by photons of light in the infrared and visible portions of the electromagnetic spectrum. When temperatures are uniform, the radiative flux between objects is in equilibrium and no net thermal energy is exchanged. The balance is upset when temperatures are not uniform, and thermal energy is transported from surfaces of higher to surfaces of lower temperature.

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    رشاد حمود
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    عزيزي حسن حياك الله
    لو تكرمت ممكن ترسل لي جداول السعه الحرارية cpلغازات نواتج الاحتراق وسأكون شاكرا لك هذا

    اخوك رشاد حمود

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  7. [7]
    حسن هادي
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    الصورة الرمزية حسن هادي


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    اقتباس المشاركة الأصلية كتبت بواسطة رشاد حمود مشاهدة المشاركة
    عزيزي حسن حياك الله
    لو تكرمت ممكن ترسل لي جداول السعه الحرارية cpلغازات نواتج الاحتراق وسأكون شاكرا لك هذا

    اخوك رشاد حمود
    الاخ العزيز سابحث عن الجداول والجارتات وان وجدتها سارسلها اليك وان لم اتمكن فارجو ان تعذرني
    مع فائق الاحترام

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  8. [8]
    zroogaa
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    السلام عليكم
    مشكورين احواني الافاضل علي ما تقدمونه من مجهود

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    البوراصي
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    مشكور على الموضوع القيم ولكن وللأسف انا ضعيف في اللغه الإنجليزيه وانا طالب وابحث عما يقويني في مجال التبريد والتكيف واتمنا ان اجد لديكم مثل هذه المواضيع باللغه العربيه
    ومره اخرة وليست الأخيره شكراً لك على المجهود الطيب وافادك الله وزادك من علمه

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    ميس نمير
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    السلام عليكم ممكن جداول الكثافة والسعة الحرارية عند درجة الحرارة 25c

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