Consider a person standing in a room at 25°C. Determine the total rate of heat transfer and the heat transfer coefficient from this person if the exposed surface area and the skin temperature of the person are1.7 m and 33°C, respectively, and the convection heat transfer coefficient is 5 W/m? · °C. 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.

Consider a person standing in a room at 25°C. Determine the total rate of heat transfer and the heat transfer coefficient from this person if the exposed surface area and the skin temperature of the person are1.7 m and 33°C, respectively, and the convection heat transfer coefficient is 5 W/m? · °C. 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.

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.
The heat transfer coefficient between a surface and a liquid is 57 W/(m2K). How many watts per square meter will be transferred in this system if the temperature difference is 10C?
Q2/ The inner and outer surfaces of a 0.5-cm- thick 2-m x2-m window glass in winter are 10°C and 3°C, respectively. If the thermal conductivity of the glass is 0.78 W/m - °C, determine the amount of heat loss, in kJ, through the glass over a period of 5 hours. What would your answer be if the glass were I cm thick? Answers: 78,624 kJ, 39,312 kJ.
A fan forces air over a computer circuit board with an area of 0.01 m2 to keep the circuit board cool. If the temperature of the surface is at 350 K and the incoming air is at 298 K, determine the rate of heat transfer in W. Assume the heat transfer coefficient is 20 W/(m2K). Report your answer to one decimal place.
1-88 Consider a 20-cm-thick granite wall with a thermal con- ductivity of 2.79 W/m-K. The temperature of the left surface is held constant at 50°C, whereas the right face is exposed to a flow of 22°C air with a convection heat transfer coefficient of 15 W/m?-K. Neglecting heat transfer by radiation, find the right wall surface temperature and the heat flux through the wall. Granite :k= 2.8 W/m-K T = 22°C T = 50°C h = 15 W/m²-K 20 cm
A wall with a thermal conductivity of 0.4 W/m-°C is maintained at 45°C. The heat transfer through the wall is 220 W. The wall surface area is 2.0m² and its thickness is 1.5 cm. Determine the temperature at the other surface.
A mother takes the milk to be given to her baby from the refrigerator and pours it into a cylindrical bottle for heating. The height of the milk in the bottle is 10 cm. Then he places the bottle into a large container with hot water at a temperature of 62 ° C. The heat transfer coefficient between hot water and bottle is 130 W / m2.oC. The process of heating the milk from 4 0C to 40 0C is required to be completed within 6 minutes. What should be the diameter of the bottle used? The properties of milk can be equal to the properties of water at the same temperature.
Water with a temperature of 15 ° C approaches vertically to a cylinder with a surface temperature of 120 ° C and a diameter of 25 mm. The velocity of the water has been given as 1 m / s. What is the heat transfer rate in kW / square meter?
Q2/ Consider a 1.2-m-high and 2-m-wide glass window whose thickness is 6 mm and thermal conductivity is k = 0.78 W/m. °C. Determine the steady rate of heat transfer through this glass window and the temperature of its inner surface for a day during which the room is maintained at 24°C while the temperature of the outdoors is 5°C. Take the convection heat transfer coefficients on the inner and outer surfaces of the window to be h1 = 10 W/m2 °C and h2= 25 W/m2 °C, and disregard any heat transfer by radiation.
For heat transfer purposes, a standing man can be modeled as a 30-cm-diameter, 170-cm-long vertical cylinder with both top and bottom surfaces insulated and with the side surface at an average temperature of 34 °C. For a convection heat transfer coefficient of 15 W/m2∙°C, determine the rate of heat loss from this man by convection in an environment at 20 °C. Round your answer to 2 decimal places.
A cool box made of a material, having Thermal Conductivity of 0.22 W/m.°C has a total area of 3.9 m² and its walls have an average thickness of 7cm. The box contains ice and glass-bottled beverages at the freezing point of water. The inside part of the box is kept cold by melting ice. How much ice (in kg) melts in 2hours if the icebox is kept in a room at 120°F?
A cat has a body temperature of 48 ºC. She stays inside a closed air conditioned room that has an inside wall temperature and inside air temperature of 40 and 35 ºC, respectively. The temperature of the room’s outside wall and the air outside the room are measured to be 45 and 50 ºC, respectively. The convection heat transfer coefficient between the cat and the inside air is 5 W/m2 ºC and the convection heat transfer coefficient between the outside air and outside wall is 35 W/m2 ºC. Use 0 ºC = 273.15 K to calculate the heat losses per unit area (W/m2 ) from the cat if the emissivity of the cat is 0.85.