A furnace wall is to be constructed of brick having standard dimensions of
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Chapter 1 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
- 2.30 An electrical heater capable of generating 10,000 W is to be designed. The heating element is to be a stainless steel wire having an electrical resistivity of ohm-centimeter. The operating temperature of the stainless steel is to be no more than 1260°C. The heat transfer coefficient at the outer surface is expected to be no less than in a medium whose maximum temperature is 93°C. A transformer capable of delivering current at 9 and 12 V is available. Determine a suitable size for the wire, the current required, and discuss what effect a reduction in the heat transfer coefficient would have. (Hint: Demonstrate first that the temperature drop between the center and the surface of the wire is independent of the wire diameter, and determine its value.)arrow_forwardWhat is the rate of heat transfer through a piece of Celotex 3 ft by 8 ft by 1 in. in thickness, if the temp of one surface is 80°F and of the other side is 60°F? thermal conductivity of Celotex in AES = 0.028. Pls determine the temperature gradient and the direction of the heat transfer as well.arrow_forwardAn eyed plate & pin is assembled as illustrated and are subjected to an opposing force of 10KN. The rod diameter & plate thickness is 6mm. The width of the plate is 20mm. A hole to which the pin is inserted is 8mm in diameter is located at the center of the plate. The plate is made of annealed SAE 1025 & the pin is high-heat oil quenched SAE 1095. (a) Determine if the assembly is safe to use; otherwise (b) Determine the safe load of the assembly.arrow_forward
- Required info: There is a 2.00 cm thick stagnant air pocket. a) What thickness of cork would have the same R-factor as the stagnant air pocket? The thermal conductivity of air is 0.0230 W/m-K and of cork is 0.0460 W/m-K. b) What thickness of tin would be required for the same R-factor as a 2.00-cm-thick stagnant air pocket? The thermal conductivity of air is 0.0230 W/m:K and of tin is 66.8 W/m-K. THANK Uarrow_forward[2] An array of electronic chips is mounted within a sealed rectangular enclosure, and cooling is implemented by attaching an aluminum heat sink (k = 180 W/m K). The base of the heat sink has dimensions of w1 = W2 = 100 mm, while the 6 fins are of thickness t = 10 mm and pitch S = 18 mm. The fin length is Lr = 50 mm, and the base of the heat sink has a thickness of Lb = 10 mm. L -Chips Water u T Electronic package, P elec If cooling is implemented by water flow through the heat sink, with uo = 3 m/s and To = temperature Tb of the heat sink when power dissipation by the chips is Pelec = 1800 W? The average convection coefficient for surfaces of the fins and the exposed base may be estimated by assuming parallel flow over a flat plate. Properties of the water may be approximated as k = 0.62 W/m-K, p = 995 kg/m3, Cp = 4178 J/kg-K, v = 7.73 x 10-7 m2/s, and Pr = 5.2. 17°C, what is the base a.) Base temperature. А. 37.8°C B. 43.9°C С. 31.4°С D. 46.2°Carrow_forwardWhat is the rate of heat transfer, temperature gradient, and the direction of the heat transfer through a piece of Celotex 3 ft by 8 ft by 1 in. in thickness, if the temp of one surface is 80°F and of the other side is 60°F? - thermal conductivity of Celotex in AES = 0.028.arrow_forward
- Bebang owns a 830-mm-thick concrete brick table top that has an area of 10,000,000 mm^2 and a 0.750-cm-thick glass plate that has an area of 20,000 cm^2. Assuming the same temperature difference across each, what is the ratio of the rate of heat conduction through the plate with respect to the rate of heat conduction through the table top? Use Table 10.1(given below) for the value of Thermal Conductivity k. Table 10.1 Thermat Conductivities of Common Substances Values are given for temperatures near o °C. Substance Thermal Conductivity k (W/m-O Diamond 2000 Silver 420 Copper 390 Gold 318 Aluminum 220 Steel iron Steel (stainless) 14 Ice 2.2 Glass (average) 0.84 Concrete brick O.84 water 0.6 Fatty tissue (without blood) 0.2 Asbestos 0.16 Plasterboard 0.16 wood 0.08-0.16 Snow (dry) 0.10 Cork 0.042 Glass wool 0.042 wool 0.04 Down feathers 0.025 Air 0.023 Polystyrene foam 0.010arrow_forwardQ#01: Write a short note on What are the best possible solutions to increase the heat transfer rate of a body.Which material will transfer more heat? Either a material with thermal conductivity ? = 121 or ? = 22 . Justify your answer. Explain the Fouling phenomenon. What is the effect of fouling on heat transfer rate?arrow_forwardBuild a spreadsheet to do the step by step method for estimating the temperature of unprotected steel work exposed to the ASTM E119 Standard Fire. Assume a convective heat transfer coefficient of 25 W/m2K and an emissivity of 0.5. Assume the specific heat to remain constant at 600 J/kgK. Use a time step of 30 seconds and an ambient temperature of 20°C. Provide an Excel plot showing the curves of the fire and a steel member through a time of 60 minutes with F/V ratios of: a)25 m-1 b)100 m-1 c)200 m-1 d)300 m-1 Note your plot should contain 5 curves. One for the fire and one for each of the F/V values. Also on the spreadsheet, highlight in green, the cells identifying the temperature of the unprotected steel member with an F/V of 200m-1 at the following times: a)3 minutes b)10 minutes c)20 minutes d)50 minutesarrow_forward
- A boiler furnace wall must have a heat loss no greater than 700 Btu/hr~ft2 and is madeof a material with a thermal conductivity of 0.60 Btu/hr~ft~F. The inner wall surfacetemperature is '2000°F, and the outer surface temperature is 800°F. What wall thick~ness is required?arrow_forward4. To make a secure fit , rivets that are larger than the rivet hole are often used and the rivet is cooled (usually in dry ice) before it is placed in the hole. A steel rivet 1.871cm in diameter is to be placed in a hole 1.869cm in diameter at 20°C. To what temperature must the rivet be cooled if it is to fit in the hole?arrow_forwardQ2 a) A leading manufacturer of household appliances is proposing a self-cleaning oven design that involves use of a composite window separating the oven cavity from the room air (Figure 2a). The composite is to consist of two high-temperature plastics (A and B) of thicknesses LA = 2LB and thermal conductivities ka = 0.15 W/m·K and kB = 0.08 W/m•K. During the self-cleaning process, the oven wall and air temperatures, Tw and Ta, are 400°C, while the room air temperature To is 25°C. The inside convection and radiation heat transfer coefficients h; and h,, as well as the outside convection coefficient ho, are each approximately 25 W/m².K. What is the minimum window thickness, L = LA + LB, needed to ensure a temperature that is 50°C or less at the outer surface of the window? This temperature must not be exceeded for safety reasons.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning