2. A person steps out of the shower and dries off. The person's skin with an emissivity of0.75 has a total area of 1.4m2 and a temperature of 35 Degrees C. What is the powerlost to the room through radiation by the person if the room is 20 Celcius?

Mathematically, the Stefan-Boltzmann Law can be given as, E = σe(T4 - To4) where E is the energy…

Answered: 2. A person steps out of the shower and…

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter14: Heat And Heat Transfer Methods

Section: Chapter Questions

Problem 55PE: At what net rate does heat radiate from a 275m2 black roof on a night when the roof’s temperature is...

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At what net rate does heat radiate from a 275m2 black roof on a night when the roof’s temperature is 30.0C and the surrounding temperature is 15.0C ? The emissivity of the roof is 0.900.
One easy way to reduce heating (and cooling) costs is to add extra insulation in the attic of a house. Suppose the house already had 15 cm of fiberglass insulation in the attic and in all the exterior surfaces. If you added an extra 8.0 cm of fiberglass to the attic, then by what percentage would the heating cost of the house drop? Take the single story house to be of dimensions 10 m by 15 m by 3.0 m. Ignore air infiltration and heat loss through windows and doors.
The surface area of an adult human is about 1.8 m?. Suppose a person with a skin temperature of 34.0 °C is standing with bare skin in a room where the air is 25.0 °C but the walls are 17.0 °C. A. There is a "dead-air" layer next to your skin that acts as insulation. If the dead-air layer is 5.00 mm thick, what is the person's rate of heat loss by conduction? B. What is the person's net radiation loss to the walls? The emissivity of skin is 0.98. C. What is the net total loss rate due to conduction and radiation combined? D. If the person is metabolizing food to heat at a rate of 155 W, what is their net rate of gain or loss?
The surface area of an adult human is about 1.8 m2. Suppose a person with a skin temperature of 34°C is standing with bare skin in a room where the air is 25°C but the walls are 17°C.a. There is a “dead-air” layer next to your skin that acts as insulation. If the dead-air layer is 5.0 mm thick, what is the person’s rate of heat loss by conduction?b. What is the person’s net radiation loss to the walls? The emissivity of skin is 0.97.c. Does conduction or radiation contribute more to the total rate of energy loss?d. If the person is metabolizing food at a rate of 155 W, does the person feel comfortable, chilly, or too warm?
4. A shower is 11.0 m from the hot water heater. The copper pipe has a radius of 1.11 cm and a thickness of 2.3 mm. A) If the hot water is at a temperature of 50°C and the room temperature is 18°C, what is the rate of heat loss through the pipe? B) How much energy is lost for a 10 minute shower?
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(b) A spherical surface of area 0.7m2, emissivity 0.88 and temperature 120°C is placed in a large, evacuated chamber whose walls are maintained at a fixed temperature. Find the rate at which radiation is emitted by the surface?( Stefan's constant o = 5.67 x 10-8 W/m²Tª ) Energy radiated per second in watts =
1. How much heat is conducted in one hour through an iron plate 2.0 cm thick and 100 cm2 in area, the temperature of the two sides being kept at 0 and 20°C? 2. A nickel plate 0.8 cm thick has a temperature difference of 64°C between its faces. It transmits 200kcal/hr through an area of 10cm2. Calculate the thermal conductivity of nickel in cgs units. 3. A container used to store ice is made of wood 5.0 cm thick and has an effective area of 12,000 cm2 and thermal conductivity of 0.00027 cal/cm2-sec-°C/cm. How much ice inside the box would be melted each 24-hour day if the outside temperature is 25°C and the temperature inside the box is 5°C.
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2. A person steps out of the shower and dries off. The person's skin with an emissivity of 0.75 has a total area of 1.4m2 and a temperature of 35 Degrees C. What is the power lost to the room through radiation by the person if the room is 20 Celcius?