Heat Transfer Radiation Lab Report

Module :Heat Transfer †Free Convection and Radiation Laboratory Date :22nd March 2012 CONTENTS INTRODUCTION3 AIMS and Objectives3 To research Free Convection and Radiation3 Theory3 EXPERIMENT3 Apparatus Used3 Procedure4 RESULTS, CALCULATIONS, OBSERVATIONS and CONCLUSIONS5 Observations During Tests5 Table 15 Table 25 Calculations6 Calculating Power (Watts)6 Calculating Heat Transfer Emissivity (? )6 Emisssivity of a dark body6 Calculating Q rad6 Calculating Q rad6 Calculating Q conv7 Equation for Free Convection7 Percentage esteems calculation7 Absolute Pressure calculation7Graph of Pressure Against Temp Difference8 Conclusions8 Conclusion11 Typical Examples of Heat Transfer12 References13 List of Figures, Tables and Graphs14 Heat Transfer Laboratory Sheet I14 Heat Transfer †Free Convection and Radiation Laboratory INTRODUCTION The motivation behind this lab is to get characteristic and constrained convection on a chamber by estimating surface and surrounding temperatures an d relating the information to convection heat move conditions. Points and Objectives To research Free Convection and Radiation 1. Decide the emissivity (? ) of a component tentatively. . Decide the Heat move coefficients by free convection Theory Natural Convection: Heat move through course of liquid due exclusively to gravity Forced Convection: Heat move through flow of liquid because of constrained smooth motion (fan, siphon, and so on ) Radiation: Heat moved by surface photon discharge, commonly just huge at T>>Room Temp. Analysis Apparatus Used Figures 1 beneath shows the vacuum siphon vessel and estimating gear utilized The contraption comprised of a warmed component which was suspended inside a [pressure vessel.The pneumatic force in the vessel was differed by the utilization of either a drain valve or a 240v vacuum siphon. The warmth contribution to the e component was differed by up to 10W, the maximum working temp was not to surpass 200 °C and kept up at that temper ature or less all through the investigation. The warmth, power Input, the component, vessel temperatures and the pneumatic force inside the vessel was controlled by the instruments accommodated the examination Procedure 1) Using the divider mounted indicator the climatic weight was 1018 mB The measure gives a perusing of check pressure (diff between the weight inside the vessel and weight outside the vessel)Absolute pressure (P) = pressure measure perusing + barometrical weight (mB) 2) Pressure decreased to 2mB and enter voltage set to 8. 21 volts. 3) Observations and readings taken after 15 mins to permit framework to balance out and readings organized. 4) Item 3 rehashed with Vacuum pressure diminished by 12, 60, 200, 500 and afterward at long last with the drain valve completely open organized as in the past. 5) Bleed valve was then completely opened to permit the weight inside the vessel to meet environmental weight and readings arranged. RESULTS, CALCULATIONS, OBSERVATIONS and CONCLUSIONSObservations During Tests The underlying perceptions were of the temperature, vacuum weight and vessel pressures corresponding to within width of the vessel and component get together. The Temp Diff sections Abs pressure chart beneath (Graph 1) shows the temp distinction at zero free convection given by the condition for a straight line Y=MX+C Surface territory of the vessel was given as 3070mm? , Element Length was given as 152mm and 6. 35mm separately. The accompanying Tables detail what is really happening to temperature and warmth move inside the vessel.The table beneath shows the outcomes from the tests completed, utilizing pressure measure readings - 1015 (mB), - 1002(mB), - 957 (mB), - 815(mB), - 515(mB) and 0. |Pressure Gauge |Abs Press |Voltage |Current |Power |Element | |(vacuum) | |TEL â€TV (K) |(Mb)^1/4 |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 misfortunes in the associating drives 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 dark body ( copper ) = 1 If ? = >1 Use ? = 0. 7 to ascertain Q rad ? = Q rad Joules or Watts A x ? x (T^4 EL †T^4 v) ? = 6. 01(W) = 1. 2 proportion (3070ãâ€"10^-6 ) x (5. 67ãâ€"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 (3070ãâ€"10^-6 ) x (5. 67ãâ€"10^-6 ) x (436^4 â€292 ^4) Q rad = 4. 87 Watt s Calculating Q rad for Pressure - 1002 Mb Q rad = ? x A x ? x (T^4 EL †T^4 v) Q rad = 0. 97 x (3070ãâ€"10^-6 ) x (5. 67ãâ€"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 misfortune 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 heat move ) 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) (3070ãâ€"10^-6 ) x (436^4 †292) Percentage esteems estimation Qrad + Qconv = Qtotal 4. 87 + 1. 14 = 6. 01 Watts Qrad% = 4. 87/6. 0 x 100% = 81% QRad this is on the grounds that it was anything but an ideal vacuum Qconv % =1. 14/6. 01 x 100% = 19% QConv this is on the grounds that it was anything but an ideal vacuum Absolute Pressure estimation Abs Press = Gauge pressure †Atmos Pressure =1015Mb †1018Mb = 3^1/4 Graph of Pre ssure Against Temp Difference [pic] Graph 1 Conclusions Temp distinction with the expectation of complimentary convection crosses Y hub is at 160(K) for zero gas pressure, the force by the warmer component has moved totally to the vessel by radiation at his point. Normal convection is increasingly common at lower temperatures though radiation is progressively predominant at higher temperaturesPossible Sources of blunder: †¢ conduction from the warmed chamber to its lodging tube †¢ potential changes in surrounding temperature †¢ Variations in surface temperature Heat Transfer by Convection and utilizations Heat ordinarily doesn't move through fluids and gases by methods for conduction. Fluids and gases are liquids; their particles are not fixed set up; they move about the greater part of the example of issue. The model utilized for clarifying warmth move through the main part of fluids and gases includes convection. Convection is the procedure of warmth move starting w ith one area then onto the next by the development of fluids.The moving liquid conveys vitality with it. The liquid streams from a high temperature area to a low temperature area. [pic] (Images politeness Peter Lewis and Chris West of Standford's SLAC. ) To comprehend convection in liquids, Consider the warmth move through the water that is being warmed in a pot on an oven. The wellspring of the warmth is the oven burner. The metal pot that holds the water is warmed by the oven burner. As the metal gets hot, it starts to direct warmth to the water. The water at the limit with the metal dish gets hot. Liquids extend when warmed and turn out to be less dense.So as the water at the base of the pot gets hot, its thickness diminishes. The distinctions in water thickness between the base of the pot, and the highest point of the pot brings about the continuous arrangement of dissemination flows. High temp water starts to ascend to the highest point of the pot uprooting the colder water tha t was initially there. Furthermore, the colder water that was available at the highest point of the pot moves towards the base of the pot where it is warmed and starts to rise. These course flows gradually create after some time, giving the pathway to warmed water to move vitality from the base of the pot to the surface.Convection likewise clarifies how an electric radiator put on the floor of a virus room heats up the air in the room. Air present close to the curls of the radiator warm up. As the air heats up, it grows, turns out to be less thick and starts to rise. As the sight-seeing rises, it pushes a portion of the virus air close to the highest point of the room off the beaten path. The virus air moves towards the base of the space to supplant the sight-seeing that has risen. As the colder air moves toward the warmer at the base of the room, it gets warmed by the radiator and starts to rise. Again, convection flows are gradually formed.Air goes along these pathways, conveying vitality with it from the radiator all through the room. Convection is the fundamental technique for heat move in liquids, for example, water and air. It is regularly said that warmth ascends in these circumstances. The more proper clarification is to state that warmed liquid ascents. For example, as the warmed air ascends from the warmer on a story, it conveys progressively vivacious particles with it. As the more vigorous particles of the warmed air blend in with the cooler air close to the roof, the normal dynamic vitality of the air close to the highest point of the room increases.This increment in the normal motor vitality compares to an expansion in temperature. The net consequence of the rising hot liquid is the exchange of warmth starting with one area then onto the next area. The convection strategy for heat move consistently includes the exchange of warmth by the development of issue. The two instances of convection talked about here †warming water in a pot and warmin g air in a room †are instances of common convection. The main impetus of the dissemination of liquid is common †contrasts in thickness between two areas as the consequence of liquid being warmed at some source. A few sources present the idea of light powers to clarify why the warmed liquids rise. We won't seek after such clarifications her