A radiant-heating system is installed in the plaster ceiling of a room 36 ft long by 18 ft wide by 9 ft high. Assume direct radiation. The temperature of the concrete floor is maintained at 75°F. The temperature of the air passing through the room is held at 75°F. If the required heat supply to the floor is 8000 BTU/hr, calculate the necessary temperature at the ceiling surface. How much heat is transferred to the air, in BUT/hr? Emissivity of plaster = 0.93; absorptivity of concrete = 0.63. The convective heat-transfer coefficient between the ceiling and the air is given by the equation hc = 0.20 (AT)1/4.

A radiant-heating system is installed in the plaster ceiling of a room 36 ft long by 18 ft wide by 9 ft high. Assume direct radiation. The temperature of the concrete floor is maintained at 75°F. The temperature of the air passing through the room is held at 75°F. If the required heat supply to the floor is 8000 BTU/hr, calculate the necessary temperature at the ceiling surface. How much heat is transferred to the air, in BUT/hr? Emissivity of plaster = 0.93; absorptivity of concrete = 0.63. The convective heat-transfer coefficient between the ceiling and the air is given by the equation hc = 0.20 (AT)1/4.

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 1.67P: 1.67 In beauty salons and in homes, a ubiquitous device is the hairdryer. The front end of a typical...

See similar textbooks

Similar questions

3. A hot pie is just taken out from an oven with a set temperature of 175°F. It is placed near a window with anambient temperature of 20°C. After 3minutes, the temperature of the pie is 150°F, determine how long it willtake the pie have a temperature of 100°F. Determine also the time when the temperature of the pie is half adegree above the ambient temperature.
An asphalt playground is heated in the sun all day; by sundown it reaches a temperature of 45degC. If the asphalt has an emissivity of 0.8, what is the heat flux emitted off the asphalt at night?
Do in in short time .plz
•An astronaut is at work in the service bay of a spacecraft and is surrounded by walls at -100oC. The outer surface area of the suit is 3m2. The suit has an emissivity of 0.05. Calculate the rate of heat loss when the suit’s outer temperature is 0oC How much food the astronaut has to eat to maintain the level of heat loss?
Heat transfer
A 20-çm diameter sphere has a surface temperature of 500 K. The sphere is suspended in 300 K still air. Find the heat transfer from the sphere. Neglect radiation.
Calculate the amount of heat that is needed to keep the inside temperature at 20 0Cwhen it is at 30C outside in a flat in the middle of the development which has an outsidewindow area of 6m2 within a total external wall and window area of 28m2 with a U value of1.2 watts/m2 Co and compare to a flat on the top floor at one end where the window area isdoubled and the external wall area is three times as big. The U value of the walls is0.23watts/m2 Co
A building in the desert is made of concrete blocks(emissivity 0.91) and has an exposed surface area of 525 m2. If the buildingis maintained at 20.0°C but the temperature on a hot desertnight is 35.0°C,what is the net rate at which the building absorbs energyby radiation?
For steady state condition, determine the heat lost by inner lining through shields to the outer lining to keep the temperature of the outside surface of a hollow brick lining of a furnace at 100°C when the temperature of the inside surface of the lining is 500°C. Take the emissivity of brick lining as well as for shield as 0.87. Heat transfer to the surrounding from the outer surface takes place by radiation and convection. The heat transfer coefficient for natural convection is given by ha = 1.44 (ΔT)^0.33 W/m2-K, ta (air temperature) = 25°C. Neglect the heat transfer by conduction and convection between the brick lining.
A box made of copper plate with outside dimensions of 5 ft by 5 ft by 6-in.is suspended horizontally in a large room where the air and wall temperaturesare 80°F. The box contains a heating coil which maintains a temperature of500 °F on all external surfaces. What is the total heat loss from the box inBtu/hr.
Q2/ A small horizontal plate is in the shape of a square with a length of 5 cm. The plate is maintained at 50 C and exposed to water at 15 C. Calculate the heat loss.
A one-story house is built over a vented crawl space. The attic is alsovented. The heating system is designed for a temperature difference of 75°F.The exterior wall of a middle bedroom is shown. The room is 10 feet 3 incheswide. The window has double pane glass. The wall is wood frame withsheathing and siding. It has 1 inch of polystyrene insulation over 31⁄2 inchesof insulation (total R-16). The ceiling has 91⁄2 inches of insulation (R-30),and the floor has 6 inches of insulation (R-19). Find the heat load for thisroom.