Consider an electrically heated brick house (k=0.40 Btu/h-ft-°F) whose walls are 9 ft high and 1 ft thick. Two of the walls of the house are 50 ft long and the others are 35 ft long. The house is maintained at 70°F at all times while the temperature of the outdoors varles. On a certain day, the temperature of the Inner surface of the walls is measured to be at 64°F while the average temperature of the outer surface is observed to remain at 45°F during the day for 10 h and at 35°F at night for 14 h.

Consider an electrically heated brick house (k=0.40 Btu/h-ft-°F) whose walls are 9 ft high and 1 ft thick. Two of the walls of the house are 50 ft long and the others are 35 ft long. The house is maintained at 70°F at all times while the temperature of the outdoors varles. On a certain day, the temperature of the Inner surface of the walls is measured to be at 64°F while the average temperature of the outer surface is observed to remain at 45°F during the day for 10 h and at 35°F at night for 14 h.

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...

See similar textbooks

Similar questions

An electrical transmission line of 1.2-cm diameter carries a current of 200 amps and has a resistance of 310-4 ohm per meter of length. If the air around this line is at v, determine the surface temperature on a windy day, assuming a wind blows across the line at 33 km/h.
1.29 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.
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.
1.79 Consider the cooling of (a) a personal computer with a separate CPU and (b) a laptop computer. The reliable functioning of these machines depends on their effective cooling. Identify and briefly explain all modes of heat transfer involved in the cooling process.
Hi, can you help me to answer this question using the first law of thermodynamics formula to explain this event? On a hot summer day, a student turns his fan on when he leaves his room in themorning. When he returns in the evening will the room be warmer or cooler than theneighborouing rooms ? Explain your answer using the first law of thermodynamics.Assume ALL doors and windows are kept closed.
In a new residential project, you strongly believethat double-paned windows are ‘better’ than singlepaned windows. Compare the rate of heat loss betweensingle and double-paned windows (1.5 m x 1 m) if thethickness of each pane is (th = 0.4 cm) and (k = 0.9W/m.K). The indoor and outdoor temperatures are 18°C and 2 °C, respectively. Thickness of the air gapbetween the double-paned windows is (th = 1 cm), and(k = 0.022 W/m.K). Image credit: Windowwhirl
Question 1:A glass window of width W = 1 m and height H = 2 m is 5 mm thick and has a thermal conductivity of kg=1.4 W/m.K. If the inner and outer surface temperatures of the glass are 15oC and -20oC, respectively, ona cold winter day, what is the rate of heat loss throughthe glass? To reduce heat loss through windows, it iscustomary to use a double pane construction in whichadjoining panes are separated by an air space. If thespacing is 10 mm and the glass surfaces in contact withthe air have temperatures of (last two digit of your Registration number) oC and -15oC, what isthe rate of heat loss from a 1 m x 2 m window? Thethermal conductivity of air is ka=0.024 W/m.K.
The boiling temperature of oxygen at atmospheric pressure at sea level (1 atm) is -183ºC. Therefore, oxygen is used in low temperature scientific studies since the temperature of liquid oxygen in a tank open to the atmosphere remains constant at -183ºC until the liquid oxygen in the tank is depleted. Any heat transfer to the tank results in the evaporation of some liquid oxygen, which has a heat of vaporization of 213 kJ/kg and a density of 1140 kg/m3at 1 atm. Consider a 4 m diameter spherical tank initially filled with liquid oxygen at 1 atm and -183ºC. The tank is exosed to 20ºC ambient ait with a heat transfer coefficient of 25 W/m2. ºC. The temperature of the thin-shelled spherical tank is observed to be almost the same as the temperature of the oxygen inside. Disregarding any radiation heat exchange, determine the rate of evaporation of the liquid oxygen in the tank as a result of the heat transfer from the ambient air
Hi, can you help me to answer this question using the first law of thermodynamics? On a hot summer day a student turns his fan on when he leaves his room in themorning. When he returns in the evening will the room be warmer or cooler than theneighborouing rooms ? Explain your answer using the first law of thermodynamics.Assume ALL doors and windows are kept closed.
1. (a) Consider a room with a 1.8-m-high and 2.0-m-wide double-pane window consisting of two 4-mm-thick layers of glass separated by a 10-mm-wide stagnant air space. The convection heat transfer coefficients on the inner and outer surfaces of the window are 12 W/m2 K and 25 W/m2 K, respectively, while the average thermal conductivity of glass is 0.78 W/m K; and the air, 0.026 W/m K. If the room is maintained at 22 oC, the outside temperature is -4 oC and heat transfer due to radiation can be neglected, determine: (i) Draw the sketch and thermal resistance network; (ii) the total thermal resistance; (iii) the steady rate of heat transfer through this double-pane window; (iv) the temperature of the inner surface of the window.…
To ensure that the balls bounce consistently, tennis balls in Wimbledon are stored at exactly 68oF. A ballboy keeps a ball in his pocket to ensure that the ball can be given to the player quickly. If the ball is observed to warm up to 70oF after one minute, how long will it take for the ball to be within 20oF of the ballboy's body temperature (98.6oF) after he puts it in his pocket? It can be assumed that the temperature in the pocket is also the normal body temperature.
Under conditions for which the same room temperature is maintained by a heating or cooling system, it is not uncommon for a person to feel chilled in the winter but comfortable in the summer.Consider a room whose air temperature is maintained at 18ºC throughout the year, while the walls of the room are nominally at 24°C and 14°C in the summer and winter, respectively. The exposed surface of a person in the room may be assumed to be at a temperature of 32°C throughout the year and to have an emissivity of 0.90. The coefficient associated with heat transfer by natural convection between the person and the room air is approximately 2 W/m2·K. Calculate the following. a. heat flux due to convection in W / m^2 b. Heat flux due to radiation in the summer in W / m^2 c. Heat flux due to radiation in the winter in W / m^2