Consider the conditions of Problem 5.27. In addition to treating heat transfer by convection directly from the chip to the coolant, a more realistic analysis would account for indirect transfer from the chip to the substrate and then from the substrate to the coolant. The total thermal resistance associated with this indirect route includes contributions due to the chip-substrate interface (a contact resistance), multidimensional conduction in the substrate, and convection from the surface of the substrate to the coolant. If this total thermal resistance is
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Fundamentals of Heat and Mass Transfer
- 1-Y Cpt 1 = (1+y)(1+ a + 5) (16+06+ €2²) f= fp+afe 2Lparrow_forwardWe wish to use the analytical model developed by Joshi and Webb to predict the heat transfer and friction characteristics (j and f) of the Offset Strip-Fin (OSF) array. 1. Compare the predictions of the friction factor using equation 5.6 of the book to the measurements of Webb and Joshi (taken from "Prediction of the Friction Factor for the Offset Strip-Fin Matrix" and given in the last column of the table below) for surfaces 1 and 8 (see Table below) at Reph = 529 and 623, respectively. As shown in the table below, the experimental friction factors for surfaces, 1 and 8 are 0.0551 and 0.0434 respectively. Use CD = 0.8. Surface 1 8 α 0.123 0.224 t/l 0.016 0.064 h (mm) 38.1 38.1 t (mm) Dh (mm) 7.518 0.406 1.626 10.897 0.0551 0.0434 2. Use the Webb and Joshi model given in the notes to make a plot of Nu versus the fin length (1) for 1 mm < 1<5 mm. You should use 0.5 mm increments of 1 or smaller. Use α= 0.184, t = 0.102 mm, h = 4.98 mm, and Reph = 500. Explain why the Nu behaves as it…arrow_forwardAs part of your work-study program at HTU, you successfully got a student job at your local ‘BEST-BURGER-IN-TOWN’ to help pay your own tuition and expenses. Since cylindrical frozen burger patties are cooked when placed on a hot stainless-steel cooking top, you like to think of the case as a conduction problem:a. Write down the appropriate general heat conduction equation that describes the cooking of those beef patties.b. Clearly state all assumptions.c. After cancelling the proper terms, write down the final energy equation for the patties.Do not solve for temperature distribution or heat transfer.arrow_forward
- 5.8 The heat transfer coefficient for air flowing over a sphere is to be determined by observing the temperature-time history of a sphere fabricated from pure copper. The sphere, which is 12.7 mm in diameter, is at 66°C before it is inserted into an airstream having a temperature of 27°C. A thermocouple on the outer surface of the sphere indicates 55°C 69 s after the sphere is inserted into the airstream. Assume and then justify that the sphere behaves as a spacewise isothermal object and calculate the heat transfer coefficient.arrow_forward16.7 with an inner layer of diatomaceous earth, 40 mm thick, and an outer layer of 85% magnesia, 25 mm thick. The inside surface of the pipe is at the steam temperature, and the heat transfer coefficient for the outside surface of the lagging is 17 W/m² K. The thermal conductivities of diatomaceous earth and 85% magnesia are 0.09, and 0.06 W/m K respectively. Neglecting radiation, and the thermal resistance of the pipe A steam main of 150 mm outside diameter containing wet steam at 28 bar is insulated Problems wall, calculate the rate of heat loss per unit length of the pipe and the temperature of the outside surface of the lagging, when the room temperature is 20°C.arrow_forwardCalculate the overall heat loss and the temperature profile for each interface if the length of the cylinder is 50 m.Please write your answers legibly.arrow_forward
- 2. Heat transfer coefficients can be difficult to measure, particularly for situations involving fast-moving fluids. In some cases however, the magnitude of the heat transfer coefficients can be estimated to a sufficient degree to enable further analysis of the larger problem. In a situation such as that described in the preceding paragraph, heat transfer occurs through the planar wall shown in the figure below. Two thermal situations are to be considered. In case I, the temperature of the fluid to the left of the wall is 130.5 °F and the fluid on the right is at 71.3 °F. Both sides of the planar wall are washed by fast- moving water. The exact values of the convective heat transfer coefficients are unknown. The heat flux through the wall is measured to be 42.6 Btu/hr-ft². 2 inches Tfl h₁ T₁ T₂ T₁² 11₂arrow_forwardLet's say a 3.0 gram copper wafer is dropped from a height of 50.0 meters. If 60% of the potential energy lost in the drop could be converted to thermal energy used to heat the copper from an initial temperature of 25 degrees celsius, what would the final temperature of the copper wafer? Would the answer be different if the wafer has a mass greater than 3 grams? Note: the specific heat of copper is 387 J/(kg*K). The temperature is between 25.8 and 26.0 degrees celsius, yes the bigger the mass the greater the energy. O The temperature is between 25.6 and 25.8 celsius, answer does not depend on mass. O The temperature is between 25.0 and 25.2 celsius, answer does not depend on mass. O The temperature is 25.5 and of course the more mass something has the greater energy will be needed to raise the temperature. The temperature is 26.2 and if the mass is doubled so will be the change in temperature. O The temperature is 25.9 degrees celsius and the answer does not depend on mass. O The…arrow_forwardplease include assumptionsarrow_forward
- 1. A composite furnace wall is made up of a 12-in. lining of magnesite refractory brick, a 5-in.thickness of 85% magnesia, and a steel casing 0.10-in. thick. Flue gas temperature is 2200 F andthe boiler room is at 80 F. Gas side film coefficient is 15 Btu/hr-sq.ft-F and air side is 4.0.Determine:a. The thermal current Q/Ab. Interface temperaturesc. Effect on thermal current and inside refractory wall temperature if the magnesia insulation weredoubled.arrow_forwardParts A & B SOLVE CAREFULLY!! Please Write Clearly and Box the final Answer(s) and label themarrow_forwardCan someone please help me with creating an excel spreadsheet to calculate heat transfer phenomenon from a cylindrical fuel rod to the coolant? The excel sheet needs to be able to calculate these 3 things: Heat generated in a fuel rod at a distance ‘r’ from the center; Total Heat generated in the Reactor; the maximum temperature in the fuel and the cladding surface temperature, for a fuel rod at a distance ‘r’ from the center. The fuel used in this will be UO2 and there is a thin layer of helium that will separate the fuel from the cladding material. The user input parameters will be: the thermal neutron flux at the core, thermal conductivity of fuel, thermal conductivity of helium, thermal conductivity of the cladding, thickness of the helium layer, thickness of the cladding, diameter of the fuel pellet, fuel rod location (r), Cylindrical Reactor Size, and the fuel enrichment. For the fluid the user input will be coolant temperature and the heat transfer coefficient.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning