Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
8th Edition
ISBN: 9781305387102
Author: Kreith, Frank; Manglik, Raj M.
Publisher: Cengage Learning
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Chapter 1, Problem 1.52P
A flat roof of a house absorbs a solar radiation flux of
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A flat plate has one surface insulated and the other exposed to the sun. The exposed surface absorbs solar radiation at a rate of 700 W/m2 and dissipates heat to the surrounding air at 350K. If the emissivity of the surface is 0.9 and the surface heat transfer coefficient is 10 W/m2.K, determine the surface temperature of the plate.
1. A 1000-W iron is left on the iron board with its base exposed to the air at 20°C. The convection heat transfer coefficient between the base surface and the surrounding air is 35 W/m². °C. If the base has an emissivity of 0.6 and a surface area of 0.02 m², determine the temperature of the base of the iron.
2. The inner and outer surfaces of a 5-m x 6-m brick wall of thickness 30 cm and thermal conductivity 0.69 W/m °C are maintained at temperatures of 20°C and 5°C, respectively. Determine the rate of heat transfer through the wall, in W.
Consider a person standing in a room kept at 22°C at all times. Your house It has been observed that the inner surfaces of the walls, floor and ceiling are at an average temperature of 15°C. If this person's exposed surface area is 1.4 m2 and if the average external surface temperature is 30°C, this person and the surrounding surfaces Determine the radiation and heat transfer rate between One's emissivity, the Stefan-Boltzmann constant a=5,67x10 -8 W/m 2 K 4
Chapter 1 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
Ch. 1 - 1.1 On a cold winter day, the outer surface of a...Ch. 1 - 1.2 The weight of the insulation in a spacecraft...Ch. 1 - 1.3 A furnace wall is to be constructed of brick...Ch. 1 - 1.4 To measure thermal conductivity, two similar...Ch. 1 - To determine the thermal conductivity of a...Ch. 1 - A square silicon chip 7mm7mm in size and 0.5-mm...Ch. 1 - A cooling system is to be designed for a food...Ch. 1 - 1.80 Describe and compare the modes of heat loss...Ch. 1 - Heat is transferred at a rate of 0.1 kW through...Ch. 1 - 1.10 A heat flux meter at the outer (cold) wall of...
Ch. 1 - 1.11 Calculate the heat loss through a glass...Ch. 1 - 1.12 A wall with a thickness is made of a...Ch. 1 - 1.13 If the outer air temperature in Problem is...Ch. 1 - Using Table 1.4 as a guide, prepare a similar...Ch. 1 - 1.15 A thermocouple (0.8-mm-diameter wire) used to...Ch. 1 - Water at a temperature of 77C is to be evaporated...Ch. 1 - The heat transfer rate from hot air by convection...Ch. 1 - The heat transfer coefficient for a gas flowing...Ch. 1 - 1.19 A cryogenic fluid is stored in a...Ch. 1 - A high-speed computer is located in a...Ch. 1 - 1.21 In an experimental set up in a laboratory, a...Ch. 1 - 1.22 In order to prevent frostbite to skiers on...Ch. 1 - Using the information in Problem 1.22, estimate...Ch. 1 - Two large parallel plates with surface conditions...Ch. 1 - 1.25 A spherical vessel, 0.3 m in diameter, is...Ch. 1 - 1.26 Repeat Problem 1.25 but assume that the...Ch. 1 - Determine the rate of radiant heat emission in...Ch. 1 - 1.28 The sun has a radius of and approximates a...Ch. 1 - 1.29 A spherical interplanetary probe with a 30-cm...Ch. 1 - A spherical communications satellite, 2 m in...Ch. 1 - A long wire 0.7 mm in diameter with an emissivity...Ch. 1 - Wearing layers of clothing in cold weather is...Ch. 1 - A section of a composite wall with the dimensions...Ch. 1 - A section of a composite wall with the dimensions...Ch. 1 - Repeat Problem 1.35 but assume that instead of...Ch. 1 - 1.37 Mild steel nails were driven through a solid...Ch. 1 - Prob. 1.38PCh. 1 - 1.39 On a cold winter day, the outside wall of a...Ch. 1 - As a designer working for a major electric...Ch. 1 - 1.41 A heat exchanger wall consists of a copper...Ch. 1 - 1.43 A simple solar heater consists of a flat...Ch. 1 - A composite refrigerator wall is composed of 5 cm...Ch. 1 - An electronic device that internally generates 600...Ch. 1 - 1.47 A flat roof is modeled as a flat plate...Ch. 1 - A horizontal, 3-mm-thick flat-copper plate, 1-m...Ch. 1 - 1.49 A small oven with a surface area of is...Ch. 1 - A steam pipe 200 mm in diameter passes through a...Ch. 1 - 1.51 The inner wall of a rocket motor combustion...Ch. 1 - 1.52 A flat roof of a house absorbs a solar...Ch. 1 - Determine the power requirement of a soldering...Ch. 1 - 1.54 The soldering iron tip in Problem 1.53...Ch. 1 - Prob. 1.55PCh. 1 - A pipe carrying superheated steam in a basement at...Ch. 1 - Draw the thermal circuit for heat transfer through...Ch. 1 - 1.60 Two electric resistance heaters with a 20 cm...Ch. 1 - 1.63 Liquid oxygen (LOX) for the space shuttle is...Ch. 1 - The interior wall of a large, commercial walk-in...Ch. 1 - 1.67 In beauty salons and in homes, a ubiquitous...Ch. 1 - The heat transfer coefficient between a surface...Ch. 1 - The thermal conductivity of fibreglass insulation...Ch. 1 - 1.71 The thermal conductivity of silver at 212°F...Ch. 1 - 1.72 An ice chest (see sketch) is to constructed...Ch. 1 - Estimate the R-values for a 5-cm-thick fiberglass...Ch. 1 - A manufacturer in the United States wants to sell...Ch. 1 - Referring to Problem 1.74, how many kilograms of...Ch. 1 - 1.76 Explain a fundamental characteristic that...Ch. 1 - 1.77 Explain each in your own words. (a) What is...Ch. 1 - What are the important modes of heat transfer for...Ch. 1 - 1.79 Consider the cooling of (a) a personal...Ch. 1 - Describe and compare the modes of heat loss...Ch. 1 - A person wearing a heavy parka is standing in a...Ch. 1 - Discuss the modes of heat transfer that determine...
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- 1.60 Two electric resistance heaters with a 20 cm length and a 2 cm diameter are inserted into a well-insulated 40-L tank of water that is initially at 300 K. If each heater dissipates 500 W, what is the time required for bringing the water temperature in the tank to 340 K? State your assumption for your analysis.arrow_forwardA cooling system is to be designed for a food storage warehouse for keeping perishable foods cool prior to transportation to grocery stores. The warehouse has an effective surface area of 1860 m2 exposed to an ambient air temperature of 32C. The warehouse wall insulation (k=0.17W/(mK)) is 7.5 cm thick. Determine the rate at which heat must be removed (W) from the warehouse to maintain the food at 4C.arrow_forward1.29 A spherical interplanetary probe with a 30-cm diameter contains electronic equipment that dissipates 100 W. If the probe surface has an emissivity of 0.8, what is its surface temperature in outer space? State your assumptions in the calculations.arrow_forward
- Consider the rate of heat conduction through a double-paned window that has a 1.6-m2 area and is made of two panes of 0.76-cm-thick glass separated by a 0.75-cm air gap. You can ignore the increased heat transfer in the air gap due to convection. a. Calculate the rate of heat conduction through this window, in watts, given that the inside surface temperature is 15.0°C, while the outside temperature is -10.0°C. Make the assumption that the temperature differences across the two glass planes are equal. First find these and then the temperature drop across the air gap. b. For comparison, calculate the rate of heat conduction, in watts, through a single 1.67-cm-thick window of the same area and with the same temperatures as in part (a).arrow_forwardThe wall of a furnace has a thickness of 5 cm and thermal conductivity of 0.7 W/m-°C. The inside surface is heated by convection with a hot gas at 402°C and a heat transfer coefficient of 37 W/m-°C. The outside surface has an emissivity of 0.8 and is exposed to air at 27°C with a heat transfer coefficient of 20 W/m-°C. Assume that the furnace is inside a large room with walls, floor and ceiling at 27°C. Show the thermal circuit and determine the heat flux through the furnace wall.arrow_forwardIn an orbiting space station, an electronic package is housed in a compartment having a surface area 1 m² which is exposed to space. The surface emissivity is 1.0. Under normal operating conditions, the electronics generate 500 W of heat which must be dissipated from the exposed surface to space. If the surface is exposed to a solar flux of 750 W/m² and its absorptivity to solar radiation is 0.25, please find the steady-state temperature of the surface.arrow_forward
- The solar radiation incident on the outside surface of an aluminum shading device is 1300 W/m2. Aluminum absorbs 10% of the incident solar energy, and dissipates it by convection from the back surface and by combined convection and radiation from the outside surface. The convection heat transfer coefficient is 10 W/m2·K for both surfaces, and the ambient/surrounding temperature can be taken 20 °C for both convection and radiation. Assuming that the aluminum shade has a uniform temperature, determine the temperature of the aluminum shading device if it is a) Polished, and b) Oxidized.arrow_forwardA 1000-W iron is left on the iron board with its base exposed to the air at 20°C. The convection heat transfer coefficient between the base surface and the surrounding air is 35 W/m2. C. If the base has an emissivity of 0.6 and a surface area of 0.02 m2, determine the temperature of the base of the iron.arrow_forwardIt is a common experience to feel 'chilly' in winter and 'warm' in summer in our homes even when the thermostat setting is kept the same. This is due to the so-called 'radiation effect' resulting from radiation heat exchange between our bodies and the surrounding surfaces of the walls and the ceiling.arrow_forward
- Consider a room whose door and windows are tightly closed, and whose walls are well-insulated so that heat loss or gain through the walls is negligible.arrow_forwardThe inside surface of an insulation layer is maintained at 350°C and the outside surface dissipates heat by convection and radiation to air and wall, respectively. The temperatures of air and wall are 15 °C. The insulation layer has a thickness of 10 cm and a thermal conductivity of 15 W/m.K. What is the value of the heat transfer coefficient at the outside surface of the layer, if the temperature at the outside surface should not exceed 225 °C? (The emissivity and the width of the surface are 0.3 and 1 m., respectively. o=5.67x10-8 W/m²K*). Tw=15°. T=225°C e=0.3 T=350°C To=15°C h,=? 10 cmarrow_forwardConsider a person whose exposed surface area is 1.7 m2, emissivity is 0.9, and surface temperature is 32°C. Determine the total rate of heat loss from that person by radiation and convection in a large room having walls at a temperature of 18oC. The convective heat transfer coefficient is 5 W/m2.K.arrow_forward
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