Consider a person standing in a roomn at 20°C with an exposed surface area of 1.5 m2. The deep body temperature of the human body is 37°C, and the thermal conductivity of the human tissue near the skin is about 0.3 W/m-°C. The body is losing heat at a rate of 150 W by natural convection and radiation to the surroundings. Taking the body temperature 0.5 cm beneath the skin to be 37°C, determine the skin temperature of the person. °C

Consider a person standing in a roomn at 20°C with an exposed surface area of 1.5 m2. The deep body temperature of the human body is 37°C, and the thermal conductivity of the human tissue near the skin is about 0.3 W/m-°C. The body is losing heat at a rate of 150 W by natural convection and radiation to the surroundings. Taking the body temperature 0.5 cm beneath the skin to be 37°C, determine the skin temperature of the person. °C

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 1.19P: 1.19 A cryogenic fluid is stored in a 0.3-m-diameter spherical container is still air. If the...

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1.19 A cryogenic fluid is stored in a 0.3-m-diameter spherical container is still air. If the convection heat transfer coefficient between the outer surface of the container and the air is 6.8 , the temperature of the air is 27°C, and the temperature of the surface of the sphere is –183°C, determine the rate of heat transfer by convection.
A glass window inside storefront has an are of 12m2 and a thickness of 1 cm. The thermal conductivity of the glass is 0.8 W/m-oC. On the cold day, outside surface temperature of the glass is -1oC and the inside surface temperature is 3 oC. Determine the temperature at a plane midway between the inside and outside glass surfaces.
A glass window in a storefront has an are of 12m2 and a thickness of 1 cm. The thermal conductivity of the glass is 0.8 W/m-oC. On the cold day, outside surface temperature of the glass is -1oC and the inside surface temperature is 3 oC. Determine the temperature at a plane midway between the inside and outside glass surfaces.
The outside temperature on a particular winter's day is 0°C. Consider two identical houses, each of external surface area 200 m² and internal temperature 20°C. The walls of the first are constructed of a single layer of brick, of thermal conductivity 1 W m-1 °C-1 and thickness 20 cm. What is the heat flux Q out of this house? What is its rate of heat loss in Watts? The walls of the second house are constructed of two layers of brick, each 10 cm thick, and a layer of insulation, also 10 cm thick. The insulation is made mostly out of air, thermal conductivity 0.01 W m of heat loss from this house? How different would your answer be if you neglected the layers of brick in this calculation? -1 °C-1. what are the heat flux and the rate
A person stands in a breezy room whose temperature is 20 °C. The emissivity of the person is 0.35. Determine the total rate of heat transfer from this person if the exposed surface area and the average surface temperature of the person are 1.6 m2 and 29 °C respectively. Take the convection heat transfer coefficient to be 6.5 W/m2/K and that the surrounding wall of the room is at a temperature of 20 oC. Select one: A 123.7 W B. 86.4 W C. 151.7 W D. 100.5 W E 43.0 W
The wall of a house is 4-meter-high and 15 -meter- wide. The wall is constructed with a 9-cm thick outer layer of brick and a 5-cm inner layer of insulating material. On a cold day, the outer surface temperature of the wall is -5°C while the inner surface temperature is 24°C. The thermal conductivity of the brick is 0.80 W/m-K, while the thermal conductivity of the insulation is 0.03 W/m-K . both inner and outer and outer has transfeer coefficeint of 20 W/m2- K a. What is the total thermal resistance of the wal? b. What is the rate of heat loss through the wal
Q2/ A 4-m-internal-diameter spherical tank made of 1.75-cm-thick stainless steel (k 15 W/m °C) is used to store iced water at 0°C. The tank is located in a room whose temperature is 35°C. The walls of the room are also at 35°C. The outer surface of the tank is black, and heat transfer between the outer surface of the tank and the surroundings is by natural convection and radiation. The convection heat transfer coefficients at the inner and the outer surfaces of the tank are 80 W/m2 °C and 10 W/m2· °C, respectively. Determine (a) the rate of heat transfer to the iced water in the tank and (b) the amount of ice at 0°C that melts during a l-h period. The heat of fusion of water at atmospheric pressure is hif 334 kJ/kg.
Consider a furnace (as a plane wall) which has a thickness of 15 cm and a surface area of 1 m?. The inside surface of the furnace wall (the hot left side of the wall) is at temperature T1. The furnace wall is made of brick with thermal conductivity of 1.198 W/m.K. The outside surface of the furnace wall (the right side of the wall) has a surface emissivity of 0.8 and is maintained at T2=101 °C and subject to air at 25 °C with convection heat transfer coefficient of 20 W/m?.K. The surroundings temperature at the outside of the furnace wall is at 25 °C. Required: Draw a clear and consistent schematic of the problem and label the operating conditions on the schematic. Perform systematic analysis, state your assumptions and justify the equation used and determine the following (circle your final answers): (i) The rate of heat transfer by convection (in W); (ii) The rate of heat radiation (in W); (iii) The surface temperature of the furnace wall T1 (in °C); (iv) The rate of conduction heat…
Air at 20°C with a convection heat transfer coefficient of 25 W/m2-K blows over a horizontal steel hot plate (k = 43 W/m-K). The surface area of the plate is 0.38 m2 with a thickness of 2 cm. The plate surface is maintained at a constant temperature of Ts = 250°C and the plate loses 300 W from its surface by radiation. Calculate the inside plate temperature (Ti). FIGURE P1-96 Air, 20°C T, = 250°C Steel Plate T; = ?
1-72 A 5-cm-external-diameter, 10-m-long hot-water pipe at 80°C is losing heat to the surrounding air at 5°C by natu- ral convection with a heat transfer coefficient of 25 W/m²-K. Determine the rate of heat loss from the pipe by natural con- vection. Answer: 2945 W
Consider a person standing in a room at 18°C. Determine the total rate of heat transfer from this person if the exposed surface area and the skin temperature of the person are 1.7 m2 and 32°C. respectively, and the convection heat transfer coefficient is 5 W/m2-K. Take the emissivity of the skin and the clothes to be 0.9, and assume the temperature of the inner surfaces of the room to be the same as the air temperature.
To warm up some milk in a thin-walled glass cylindrical container whose diameter is 6 cm. The height of the milk in the glass is 7 cm. The milk container is placed into a large pan filled with hot water at 60°C. The milk is stirred constantly, so that its temperature is uniform at all times. If the heat transfer coefficient between the water and the glass is 120 W/m2.°C, determine how long it will take for the milk to warm up from 3°C to 38°C. Take the properties of the milk to be the same as those of water. Can the milk in this case be treated as a lumped system? Use the lumped system analysis to solve the problem. The properties of water and milk at 20°C are, k = 0.607 W/m.°C,p=998 kg/m', and C, = 4.182 kJ/kg.°C. Answer: 5.8 min. ملاحظه: تكون هنا قيمة (0.1 < Bi( ويفترض لايطبق التحليل الكتلي , ولكن استخدم نفس التحليل والمعادلات في المحاضرة وكذلك في المثال لان الحليب يخلط باستمرار ولذلك تكون درجة حرارته منتظمه و متغيره مع الزمن لانه يكتسب حراره من الماء ويسخن وترتفع درجة حرارته مع…