Required information Consider a very long, slender rod. One end of the rod is attached to a base surface maintained at Tb. while the surface of the rod is exposed to an air temperature of 400°C. Thermocouples imbedded in the rod at locations 25 mm and 120 mm from the base surface register temperatures of 335°C and 375°C, respectively. NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part. 2 Air mm. To Determine the rod length (mm) for the case where the ratio of the heat transfer from a finite length fin to the heat transfer from a very long fin under the same conditions is 99 percent. The length of the rod is

Required information Consider a very long, slender rod. One end of the rod is attached to a base surface maintained at Tb. while the surface of the rod is exposed to an air temperature of 400°C. Thermocouples imbedded in the rod at locations 25 mm and 120 mm from the base surface register temperatures of 335°C and 375°C, respectively. NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part. 2 Air mm. To Determine the rod length (mm) for the case where the ratio of the heat transfer from a finite length fin to the heat transfer from a very long fin under the same conditions is 99 percent. The length of the rod is

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.13P

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A horizontal, 3-mm-thick flat-copper plate, 1-m long and 0.5-m wide, is exposed in air at 27C to radiation from the sun. If the total rate of solar radiation absorbed is 300 W and the combined radiation and convection heat transfer coefficients on the upper and lower surfaces are 20 and 15W/m2K, respectively, determine the equilibrium temperature of the plate.
A 212-mm-square, 15-mm-thick tile has the thermo-physical properties of Pyrex (ϵ = 0.83) and emerges from a curing process at an initial temperature of Ti = 145°C. The backside of the tile is insulated while the upper surface is exposed to ambient air and surroundings at 25°C. (a) Estimate the time required for the tile to cool to a final, safe-to-touch temperature of Tf = 42°C. Use an average tile surface temperature of T¯=(Ti+Tf)/2 to estimate the average free convection coefficient and the linearized radiation coefficient. How sensitive is your estimate to the assumed value for T¯? (b) Estimate the required cooling time if ambient air is blown in parallel flow over the tile with a velocity of 10 m/s
(a) If the cost of producing the hot water is $0.10 per kWh, what is the representative daily costof heat loss from an uninsulated pipe to the air per meter of pipe length? The convectionresistance associated with water flow in the pipe may be neglected.(b) Determine the savings associated with application of a 10-mm-thick coating of urethaneinsulation (k = 0.026 W/m-K) to the outer surface of the pipe.
The emissivity of galvanized steel sheet, a common roofing material, is ε = 0.13 at temperatures around 300 K, while its absorptivity for solar irradiation is αS = 0.65. Would the neighborhood cat be comfortable walking on a roof constructed of the material on a day when GS = 750 W/m2, T∞ = 16°C, and h = 7 W/m2 · K? Assume the bottom surface of the steel is insulated.
A well-insulated inside room, 6 m wide and 9 m long with a 3 m ceiling height, is to be heated by means of a ceiling panel installation. It is desired to maintain the surface of the floor at a temperature of 27 oC. Determine the necessary ceiling surface temperature to meet this requirement if the floor is to be planed oak, the ceiling is to be painted with an oil paint, and it is estimated that the portion of the heating requirement to be supplied by radiation is 2 500 W. Assume the walls to be nonconducting but reradiating.
Chips of width L _ 15 mm on a side are mounted to a substrate that is installed in an enclosure whose walls and air are maintained at a temperature of Tsur=T∞=25oC. The chips have an emissivity of ε=0.60 and a maximum allowable temperature of Ts=85oC. (a) If heat is rejected from the chips by radiation and natural convection, what is the maximum operating power of each chip? The convection coefficient may be approximated as h=11.7 W/m2K. (b) If a fan is used to maintain airflow through the enclosure and heat transfer is by only forced convection, with h=250 W/m2K, what is the maximum operating power
During hot summer weather, many people put “koozies” around their beverages to keep the drinks cold. In addition to preventing a warm hand from heating the container through conduction, what other mechanisms slow the process of warming beverages?
For the Convective Heat Transfer experiment, describe the difference in the procedures: Natural or FreeConvection and Forced convection. What makes the FORCED convection experiment as FORCED? Explain which, in your consideration should give the higher heat transfer rate? And REASON why? Did your results support your consideration?
A grandmother is concerned about reducing her winter heating bills. Her strategy isto loosely fit rigid polystyrene sheets of insulation over her double-pane windows rightafter the first freezing weather arrives. Identify the relevant heat transfer processes on acold winter night when the foamed insulation sheet is placed:(a) on the inner surface, and (13)3(b) on the outer surface of her window.
The door of a 1 m long by 27.5 cm wide oven is made up of 2 AISI 1010 carbon steel plates of identical thickness and an 8 mm thick mineral fiber board with resin binder (intermediate plate) . the composite plate considering the three plates is 5 cm. The temperature on the inner wall of the oven is 172 ° C and the surface temperature on the oven door (outer wall) is 35 ° C. The oven door is exposed in a room where the ambient air temperature is 30 ° C. Do the following: Estimate the convective heat transfer coefficient associated with ambient air.
Calculate the convection heat loss from the top and bottom of a flat 1 m squarehorizontal restaurant grill heated to 227°C in ambient air at 27°C.
A rectangular slab of butter which is 46.2 mm thick at a temperature of 277.6 K in a cooler is removed and placed in an environment at 297.1 K. The sides and bottom of the butter container can be considered to be insulated by the container sidewalls. The flat top surface of the butter is exposed to the environment. The convective coefficient is constant at 8.52 W/m2 K. Calculate the temperature in the butter at the surface, at 25.4 mm below the surface, and at 46.2 mm below the surface at the insulated bottom after 5 h exposure. k = 0.197 W/m-K, Cp = 2.30 kJ/kg-K and ρ = 998 kg/m3. Ans: T= 292.2 K , 288.3