The fin efficiency is defined as the ratio of the actual heat transfer from the fin to a. The heat transfer from an equivalent fin which is infinitely long b. The heat transfer through the base area of the same fin c. The heat transfer from the same fin with an adiabatic tip d. The heat transfer from the same fin if the temperature along the entire length of the fin is the same as the base temperature

The fin efficiency is defined as the ratio of the actual heat transfer from the fin to a. The heat transfer from an equivalent fin which is infinitely long b. The heat transfer through the base area of the same fin c. The heat transfer from the same fin with an adiabatic tip d. The heat transfer from the same fin if the temperature along the entire length of the fin is the same as the base temperature

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.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.59P

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Similar questions

2.15 Suppose that a pipe carrying a hot fluid with an external temperature of and outer radius is to be insulated with an insulation material of thermal conductivity k and outer radius . Show that if the convection heat transfer coefficient on the outside of the insulation is and the environmental temperature is , the addition of insulation actually increases the rate of heat loss if , and the maximum heat loss occurs when . This radius, is often called the critical radius.
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.)
Draw the thermal circuit for heat transfer through a double-glazed or a double-paned window. Identify each of the circuit elements. Include solar radiation to the window and interior space.
2.50 Compare the rate of heat flow from the bottom to the top of the aluminum structure shown in the sketch below with the rate of heat flow through a solid slab. The top is at v, the bottom at . The holes are filled with insulation that does not conduct heat appreciably.
Using Table 1.4 as a guide, prepare a similar table showing the orders of magnitude of the thermal resistances of a unit area for convection between a surface and various fluids.
1.37 Mild steel nails were driven through a solid wood wall consisting of two layers, each 2.5-cm thick, for reinforcement. If the total cross-sectional area of the nails is 0.5% of the wall area, determine the unit thermal conductance of the composite wall and the percent of the total heat flow that passes through the nails when the temperature difference across the wall is 25°C. Neglect contact resistance between the wood layers.
A high-speed computer is located in a temperature-controlled room at 26C. When the machine is operating, its internal heat generation rate is estimated to be 800 W. The external surface temperature of the computer is to be maintained below 85C. The heat transfer coefficient for the surface of the computer is estimated to be 10W/m2K. What surface area would be necessary to assure safe operation of this machine? Comment on ways to reduce this area.
The annual fixed costs for insulating a certain steam pipe installation can be expressed as Cf = 30S + 40 dollar per year where S is thickness of insulation in inches, and the annual cost of energy lost (annual direct costs) from the installation may be expressed in terms of the insulation thickness as Cp = 100/S $ per year. Determine the optimum annual insulation thickness cost.
Answer within 10 minutes : The temperature at the inside surface of an oven is 460 oF. The inside wall of the oven is made of brick and is 8 inch thick. The thermal conductivity of the brick is 2.2 Btu/hr.ft2.(oF/ft). The outside of the oven is covered with a 3-inch layer of asbestos as insulation, which has a thermal conductivity of 0.11 Btu/hr.ft2.(oF/ft). If the outer surface of the insulation has a temperature of 100 oF , calculate the amount of heat lost through 2 ft2 of wall area in 3 hours.
Shape factor for a cylinder whose length equals its diameter is 1.5 B. 0.5 1.0 D. 2.0
The Biot number is dependent on the following except: A. thermal conductivity of cylinder B. heat transfer coefficient of water bath C. none of the given choices D. radius (characteristic length for cylinders)
A flat wall is exposed to the environment. The wall is covered with a layer of insulation 1.0 inches thick whose thermal conductivity is 0.8 Btu/h*ft²*°F. The temperature of the wall on the inside of the insulation is 600°F. The wall loses heat to the environment by convection on the surface of the insulation. The average value of the convection heat transfer coefficient on the insulation surface is 950 Btu/h*ft²*°F. Compute the bulk temperature of the environment (Tb) if the outer surface of the insulation does not exceed 105°F.