'Heat Transfer Radiation Lab Report\r'

'Module : kindle exchange †giving Convection and ir radianiation research laboratoryoratory Date :22nd March 2012 limit INTRODUCTION3 AIMS & OBJECTIVES3 Objectives3 To canvass stark Convection and Radiation3 Theory3 EXPERIMENT3 Apparatus apply3 Procedure4 RESULTS, CALCULATIONS, OBSERVATIONS & CONCLUSIONS5 Observations During Tests5 Table 15 Table 25 Calculations6 astute king (Watts)6 dictate modify wobble Emissivity (? )6 Emisssivity of a black body6 cypher Q rad6 Calculating Q rad6 Calculating Q conv7 Equation for Free Convection7 constituent value calculation7 Absolute extort calculation7graphical record of insistency Against temporary worker Difference8 Conclusions8 Conclusion11 Typical Examples of cacoethes Transfer12 References13 List of Figures, Tables & Graphs14 high temperature Transfer Laboratory Sheet I14 lovingness Transfer †Free Convection and Radiation Laboratory INTRODUCTION The purpose of this research lab is to understand rude(a) and oblige convection on a cylinder by measuring come in and ambient temperatures and relating the data to convection agitate transplant equations. AIMS & OBJECTIVES Objectives To investigate Free Convection and Radiation 1. Determine the emissivity (? ) of an element essayally. . Determine the Heat wobble coefficients by vacate convection Theory inherent Convection: Heat stir by dint of circulation of liquified out-of-pocket solely to gravity strained Convection: Heat remove by dint of and through circulation of smooth-spoken due to obligate facile impetus (fan, pump, etc. ) Radiation: Heat budgered by surface p hoton emission, ordinaryly only signifi chamberpott at T>>Room Temp. EXPERIMENT Apparatus Used Figures 1 at a lower place shows the senselessness pump vas and measuring equipment apply The apparatus consisted of a change element which was suspended privileged a [ impel piddlecraft.The ae regulate off force per unit ara i n the vas was varied by the use of either a bleed valve or a 240v vacuum pump. The conflagrate input to the e element was varied by up to 10W, the soap working temp was non to exceed two hundred°C and maintained at that temperature or little passim the experiment. The warmness, forefinger Input, the element, vas temperatures and the stress pressure inside the vessel was determined by the instruments provided for the experiment Procedure 1) Using the wall mounted barometer the atmospherical pressure was 1018 mB The gauge gives a denotation of gauge pressure (diff between the pressure inside the vessel and pressure outside the vessel)Absolute pressure (P) = pressure gauge reading + atmospheric pressure (mB) 2) squash reduced to 2mB and input voltage set to 8. 21 volts. 3) Observations and readings taken after 15 mins to discontinue g all overnance to stabilise and readings tabulated. 4) Item 3 repeated with nullity pressure reduced by 12, 60, 200, 500 and thus fin ally with the bleed valve fully open tabulated as before. 5) Bleed valve was then fully opened to allow the pressure inside the vessel to meet atmospheric pressure and readings tabulated. RESULTS, CALCULATIONS, OBSERVATIONS & CONCLUSIONSObservations During Tests The initial observations were of the temperature, vacuum pressure and vessel pressures in relation to the inside diameter of the vessel and element assembly. The Temp Diff verses Abs pressure graph below (Graph 1) shows the temp difference at zero bleak convection given by the equation for a squ atomic number 18 line Y=MX+C get on ara of the vessel was given as 3070mm? , divisor Length was given as 152mm and 6. 35mm respectively. The following Tables full point what is actually occurring to temperature and erupt tilt inside the vessel.The tabula wax below shows the results from the tests carried out, using pressure gauge readings -1015 (mB), - cytosine2(mB), -957 (mB), -815(mB), -515(mB) and 0. | instancy imag ine |Abs Press |Voltage |Current |Power |Element |Element | |(vacuum) | | | | | | | |TEL â€TV (K) |(Mb)^1/4 |W |W |% |% | WM^-2K^-1 | |144 |2^1/4 = 1. 19 |4. 7 |1. 14 |81 |19 |2. 57 WM^-2K^-1 | |133 |16^1/4 = 2 |4. 31 |1. 66 |72 |28 |4. 06 WM^-2K^-1 | |123 |61^1/4 = 2. 79 |3. 81 |2. 13 |64 |36 |5. 64 WM^-2K^-1 | |111 |203^1/4 = 3. 77 |3. 25 |2. 71 |55 |45 |7. 95 WM^-2K^-1 | |97 |503^1/4 = 4. 73 |2. 68 |3. 24 |45 |55 |10. 8 WM^-2K^-1 | |87 |1018^1/4 = 3. 22 |2. 27 |3. 65 |38 |62 |13. 66 WM^-2K^-1 | Table 2 Calculations Heat losses in the connecting leads Q = (0. 94 x Volts x Amperes) in watts Calculating Power (Watts) Power = Volts x Amperes (Watts) Power= 8. 21volts x 0. 779 amps = 6. 39 (W) x Heat loses Power = 6. 39 (W) x 0. 94 = 6. 01 Watts Heat Transfer = 0. 94 x 8. 21 x 0. 779 = 6. 01 watts Calculating Heat Transfer Emissivity (? ) Emisssivity of a black body ( slovenly person ) = 1 If ? = >1 Use ? = 0. 7 to calculate Q rad ? = Q rad Joules or Watts A x ? x (T^4 EL †T^4 v) ? = 6. 01(W) = 1. 2 ratio (3070×10^-6 ) x (5. 67×10^-6 ) x (436^4 â€292 ^4) Calculating Q rad for Pressure -1015 Mb Q rad = ? x A x ? x (T^4 EL †T^4 v) Q rad = 0. 97 x (3070×10^-6 ) x (5. 67×10^-6 ) x (436^4 â€292 ^4) Q rad = 4. 87 Watts Calculating Q rad for Pressure -1002 Mb Q rad = ? x A x ? x (T^4 EL †T^4 v) Q rad = 0. 97 x (3070×10^-6 ) x (5. 67×10^-6 ) x (426^4 â€293 ^4)Q rad = 4. 31 Watts Calculating Q conv for Free Convection at Heat input 4. 87(W) Q conv = Heat loss x Volts x Amperes †Q rad Q conv = 0. 94 x 8. 21 x0. 779 †4. 87 Q conv = 1. 14 Watts Equation for Free Convection Q conv = h ( Convected light up carry-over ) x A x (T^4 EL †T^4 v) Transpose for h (Convected Heat Transfer) h = Qconv h = 1. 14 = 2. 58Wm^-2K^-1 A x (T^4 EL †T^4 v) (3070×10^-6 ) x (436^4 †292) Percentage values calculation Qrad + Qconv = Qtotal 4. 87 + 1. 14 = 6. 01 Watts Qrad% = 4. 87/ 6. 0 x 100% = 81% QRad th is is because it was not a perfect vacuum Qconv % =1. 14/ 6. 01 x 100% = 19% QConv this is because it was not a perfect vacuum Absolute Pressure calculation Abs Press = Gauge pressure †Atmos Pressure =1015Mb †1018Mb = 3^1/4 Graph of Pressure Against Temp Difference [pic] Graph 1 Conclusions Temp difference for free convection crosses Y axis is at 160(K) for zero gas pressure, the power by the fume element has transferred completely to the vessel by shaft of light at his point. Natural convection is to a greater extent prevalent at lower temperatures whereas light beam is to a greater extent prevalent at higher temperaturesPossible Sources of error: • conduction from the het up(p) cylinder to its housing tube • accomplishable changes in ambient temperature • Variations in surface temperature Heat Transfer by Convection and uses Heat typically does not flow through liquids and gases by intend of conduction. Liquids and gases argon legatos; their pa rticles ar not fixed in place; they move roughly the flock of the sample of outlet. The representative use for explaining hot up transfer through the mass of liquids and gases involves convection. Convection is the process of modify transfer from one arrangement to the next by the movement of fluids.The moving fluid carries free postal code with it. The fluid flows from a high temperature positioning to a low temperature location. [pic] (Images courtesy Peter Lewis and Chris western of Standfords SLAC. ) To understand convection in fluids, Consider the heat transfer through the water system that is macrocosm change in a pot on a stove. The spring of the heat is the stove burner. The alloy pot that holds the water is heat up up by the stove burner. As the metal leads hot, it begins to conduct heat to the water. The water at the frontier with the metal pan becomes hot. Fluids expand when alter and become less dense.So as the water at the foundation of the pot bec omes hot, its parsimony decreases. The differences in water density between the puke of the pot, and the top of the pot results in the gradual formation of circulation currents. Hot water begins to rise to the top of the pot displacing the arcticer water that was originally there. And the colder water that was present at the top of the pot moves towards the skunk of the pot where it is heated and begins to rise. These circulation currents slowly develop over time, providing the pathway for heated water to transfer vigour from the bottom of the pot to the surface.Convection also explains how an electric heater lay on the floor of a cold room warms up the pushover in the room. bearing present dependable the coils of the heater warm up. As the institutionalise warms up, it expands, becomes less dense and begins to rise. As the hot publicize rises, it pushes fewwhat of the cold phone line nest the top of the room out of the way. The cold air moves towards the bottom of th e room to replace the hot air that has risen. As the colder air approaches the heater at the bottom of the room, it becomes warmed by the heater and begins to rise. Once more, convection currents are slowly formed.Air travels along these pathways, carrying energy with it from the heater throughout the room. Convection is the main system of heat transfer in fluids much(prenominal) as water and air. It is practically verbalize that heat rises in these situations. The more appropriate write up is to say that heated fluid rises. For instance, as the heated air rises from the heater on a floor, it carries more energetic particles with it. As the more energetic particles of the heated air mix with the cooler air high-priced the ceiling, the number ki lucreic energy of the air near the top of the room increases.This increase in the just kinetic energy corresponds to an increase in temperature. The net result of the rising hot fluid is the transfer of heat from one location to other(prenominal) location. The convection method of heat transfer always involves the transfer of heat by the movement of matter. The two examples of convection discussed here †change water in a pot and heat system air in a room †are examples of cancel convection. The driving force of the circulation of fluid is natural †differences in density between two locations as the result of fluid being heated at some source. Some sources introduce the concept of cheering forces to explain why the heated fluids rise. We will not pursue such explanations here. ) Natural convection is common in nature. The earths oceans and atmosphere are heated by natural convection. In contrast to natural convection, forced convection involves fluid being forced from one location to another by fans, pumps and other devices. Many home heating systems involve force air heating. Air is heated at a furnace and blown by fans through ductwork and released into rooms at vent locations. This is an example of forced convection.The movement of the fluid from the hot location (near the furnace) to the cool location (the rooms throughout the house) is driven or forced by a fan. Some ovens are forced convection ovens; they experience fans that blow heated air from a heat source into the oven. Some fireplaces deepen the heating ability of the fire by blowing heated air from the fireplace unit into the adjacent room. This is another example of forced convection. Heat Transfer by Radiation A final method of heat transfer involves radiation. Radiation is the transfer of heat by fashion of electromagnetic waves.To radiate means to send out or spread from a primal location. Whether it is light, sound, waves, rays, flower petals, wheel spokes or pain, if something radiates then it protrudes or spreads outward from an origin. The transfer of heat by radiation involves the carrying of energy from an origin to the space adjoin it. The energy is carried by electromagnetic waves and d oes not involve the movement or the interaction of matter. Thermal radiation can occur through matter or through a region of space that is void of matter (i. e. , a vacuum).In fact, the heat genuine on humanity from the lieshine is the result of electromagnetic waves traveling through the void of space between the Earth and the sun. all in all objects radiate energy in the form of electromagnetic waves. The rate at which this energy is released is proportional to the kB temperature (T) raised to the fourth power. Radiation rate = k•T4 (Images courtesy Peter Lewis and Chris West of Standfords SLAC. ) The hotter the object, the more it radiates. The sun obviously radiates off more energy than a hot mug of coffee. The temperature also affects the wavelength and frequency of the radiated waves.Objects at typical room temperatures radiate energy as infrared waves. Being invisible to the human eye, we do not see this form of radiation. An infrared television camera is capable of detecting such radiation. Perhaps you have seen thermal photographs or videos of the radiation surrounding a person or animal or a hot mug of coffee or the Earth. The energy radiated from an object is usually a collection or range of wavelengths. This is usually referred to as an emission spectrum. As the temperature of an object increases, the wavelengths within the spectra of the emitted radiation also decrease.Hotter objects be given to emit shorter wavelength, higher frequency radiation. The coils of an electric wassailer are considerably hotter than room temperature and emit electromagnetic radiation in the visible spectrum. Fortunately, this provides a well-to-do warning to its users that the coils are hot. The tungsten filament of an incandescent light bulb emits electromagnetic radiation in the visible (and beyond) range. This radiation not only allows us to see, it also warms the glass bulb that contains the filament. Put your sight near the bulb (without touching it ) and you will obtain the radiation from the bulb as well.Thermal radiation is a form of heat transfer because the electromagnetic radiation emitted from the source carries energy away from the source to surrounding (or distant) objects. This energy is absorbed by those objects, causing the average kinetic energy of their particles to increase and causing the temperatures to rise. In this sense, energy is transferred from one location to another by means of electromagnetic radiation. The image at the ripe(p) was taken by a thermal image camera. The camera detects the radiation emitted by objects and represents it by means of a color photograph.The hotter colors represent areas of objects that are emitting thermal radiation at a more intense rate. Conclusion The experiment described higher up provides a convenient method whereby You may investigate the different processes that contribute to cooling in a standard laboratory experiment. In particular, the measurements obtained to e nable you to enlighten the relative contributions from convection and radiation. Examples of Free †Natural Convection Heat transfer by natural convection occurs when a fluid is in contact with a surface hotter or colder than itself. As the fluid is heated or cooled it changes its density.This difference in density causes movement in the fluid that has been heated or cooled and causes the heat transfer to continue. There are many examples of natural convection in the food industry. Convection is real when hot surfaces, such as retorts which may be vertical or horizontal cylinders, are overt with or without insulation to colder ambient air. It occurs when food is placed inside a chiller or deep-freeze store in which circulation is not assisted by fans. Convection is classical when material is placed in ovens without fans and by and by when the cooked material is removed to cool in air.Convective heat transfer is a mechanism of heat transfer occurring because of bulk motion ( observable movement) of fluids. Heat is the entity of interest being advected (carried), and diffused (dispersed). This can be contrasted with radiative heat transfer, the transfer of energy through electromagnetic waves. Heat is transferred by convection in numerous examples of naturally occurring fluid flow, such as: wind, oceanic currents, and movements within the Earths mantle. Convection is also used in engine room practices to provide desired temperature changes, as in heating of homes, industrial processes, cooling of equipment, etc.The rate of convective heat transfer may be better by the use of a heat sink, often in conjunction with a fan. For instance, a typical computer CPU will have a purpose-made fan to ensure its operating temperature is unploughed within tolerable limits. Typical Examples of Heat Transfer CONDUCTION: Heat conduction is an essential and customary part of our daily lives, in industry, and in nature. Whenever heat needs to be transferred through an op aque substance, the transfer must be by conduction.In a hot-water heating system, for example, heat from burning fuel is transferred by conduction through the iron or steel of the boiler to heat the water. Heat from a burner on a stove is conducted through the bottom of utensils to cook food. In nature, the surface of the earth is heated by the sun, and some of this heat is conducted to deeper layers of the state during the day and back to the surface at night-the varying ability of different kinds of soil and water to absorb and conduct heat received from the sun has a profound effect on local and worldwide weather and climate. Examples Touching a stove and being burned -Ice cooling conquer your hand -Boiling water by thrusting a red-hot piece of iron into it CONVECTION: Free, or natural, convection occurs when bulk fluid motion (steams and currents) are caused by perkiness forces that result from density variations due to variations of temperature in the fluid. Forced convectio n is a term used when the streams and currents in the fluid are induced by external meansâ€such as fans, stirrers, and pumpsâ€creating an artificially induced convection current. Examples -Hot air rising, cooling, and falling (convection currents An old-fashioned radiator (creates a convection cell in a room by emitting warm air at the top and drawing in cool air at the bottom). RADIATION: †Heat from the sun warming your face- Heat from a lightbulb †Heat from a fire †Heat from anything else which is warmer than its surroundings. †louse up chambers in Jet engines †Circulation Boiler Furnaces industrial example Radiation Heat transfer mostly occurs in Higher temperature applications within processes with furnace temperatures above about 2200°F (1200°C). They usually have furnaces which use combustors such as in the metals, minerals, and waste incineration industries.In general, the dominant heat transfer mechanism in those industries is thermal r adiation. This is in contrast to lower temperature applications where both radiation and forced convection are often important. References [1] Understanding Physics, sections 11. 5 †11. 7, rump Wiley & Sons 1998. [2] C. T. O’Sullivan, Correction for cooling techniques in heat experiments. Physics Education, 25, 176 †179 (1990). [3] The data acquisition system (data logger) used was the eProLab system developed under the Leonardo da Vinci Programme ComLab2 (project NO SI 143008); website www. e-prolab. com/comlab/. 4] In some situations differences between Ts and Ta may be important; see, for example, C. T. O’Sullivan, Newtons law of cooling †a slender assessment, Amer. J. Phys. , 58 (10), 956 †960 (1990). SHEFFIELD HALLAM UNIVERSITY FACULTY OF ACES (2009), Process engine room Lab Sheet. Multi Hole Extrusion Suranaree University of Technology, Last accessed 7th April 2009 at: http://www. sut. ac. th/Engineering/metal/pdf/metform/04_extrusion. pdf ROYMECH : Mechanical engineering and engineering materials. †Last accessed 1st April 2009 at: http://www. roymech. co. uk/Useful_Tables/Manufacturing/Extruding. tml Russ College of Engineering and Technology at Ohio University. http://www. ent. ohiou. edu/~raub/manufacturing/extrusion. htm#Types%20of%20 extrusion: line notes and hand outs. Sheffield Hallam University List of Figures, Tables & Graphs Figure 1Vacuum Pump and vas set up Table 1Pressure gauge readings -1015 (mB), -1002(mB), -957 (mB), -815(mB), -515(mB) and 0 Table 2Temp Differences of 144(K), 133(K), 123(K), 111(K), 97(K) and 87(K) Graph 1Temp Difference Vs Absolute Pressure Appendixes Heat Transfer Laboratory SheetI [pic] ———————†Figure 1 Table 1 Temp difference free convection (160K)\r\n'