Concept explainers
A more realistic approach to the solar greenhouse of Example 16.7 considers the time dependence of the solar input. A function that approximates the solar input is (40 Btu/h/ft2) sin2(πt/24), where t is the time in hours, with t = 0 at midnight. Then the greenhouse is no longer in energy balance, but is described instead by the differential form of Equation 16.3 with Q the time-varying energy input. Use computer software or a calculator with differential-equation-solving capability to find the time-dependent temperature of the greenhouse, and determine the maximum and minimum temperatures. Assume the same numbers as in Example 16.7, along with a heat capacity C = 1500 Btu/°F for the greenhouse. You can assume any reasonable value for the initial temperature, and after a few days your greenhouse temperature should settle into a steady oscillation independent of the initial value.
Want to see the full answer?
Check out a sample textbook solutionChapter 16 Solutions
Essential University Physics Plus Mastering Physics with eText -- Access Card Package (3rd Edition)
Additional Science Textbook Solutions
Physics for Scientists and Engineers with Modern Physics
An Introduction to Thermal Physics
The Cosmic Perspective (8th Edition)
Essential University Physics: Volume 1 (3rd Edition)
Cosmic Perspective Fundamentals
University Physics with Modern Physics (14th Edition)
- What is the surface temperature of a star that has a radius of 7.00 x 108 m and emits power at a rate of 5.00 x 1026 watts? Assume that the star is an ideal blackbody and that the temperature of the surrounding region of outer space is 0.000 K. (Hint: σ = 5.67 x 10-8 watts/m2K4 ,and the surface area of a sphere is A = 4πR2.) a. 5,200 K b. 5430 K c. 5,050 K d. 5820 K e. 6,150 Karrow_forwardA sphere of radius 0.500 m, temperature 25.7o C, and emissivity 0.915 is isolated in an environment of temperature 77.0o C. At what rate does the sphere emit thermal radiation? At what rate does the sphere absorb thermal radiation? What is the sphere's net rate of energy exchange?arrow_forwardCan we define the convection resistance for a unit surface area as the inverse of the convection heat transfer coefficient?arrow_forward
- Consider a flat-plate solar collector placed on the roof of a house. The temperatures at the inner and outer surfaces of the glass cover are measured to be 33°C and 31°C, respectively. The glass cover has a surface area of 2.5 m2, a thickness of 0.6 cm, and a thermal conductivity of 0.7 W/m·K. Heat is lost from the outer surface of the cover by convection and radiation with a convection heat transfer coefficient of 10 W/m2·K and an ambient temperature of 15°C. Determine the fraction of heat lost from the glass cover by radiation.arrow_forwardWhat is the average kinetic energy of helium atoms in a region of the solar corona where the temperature is 6.00 × 105 K?arrow_forwardIn 2000, a gargantuan iceberg broke away from the Ross Ice Sheet in Antarctica. It was approximately a rectangle with dimensions 295 km295 km long, 37.0 km37.0 km wide, and 250.0 m250.0 m thick. What is the mass of this iceberg, given that the density of ice is 917 kg/m3917 kg/m3? How much heat transfer ?Q in joules is needed to melt the iceberg? Assume that the temperature of the iceberg is uniform at 0∘C.0∘C. The latent heat of fusion for water is 334 kJ/kg. How many years would it take sunlight alone to melt ice this thick if the ice absorbs an average of 113 W/m2,113 W/m2, 12.0 h12.0 h per day?arrow_forward
- (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 =arrow_forwardCan a medium involve (a) conduction and convection,(b) conduction and radiation, or (c) convection and radiationsimultaneously? Give examples for the “yes” answers.arrow_forwardConsider an opaque plate that is well insulated on the edges and it is heated at the bottom with an electric heater. The plate has an emissivity of 0.67, and is situated in an ambient surrounding temperature of 7°C where the natural convection heat transfer coefficient is 7 W/m2?K. To maintain a surface temperature of 80°C, the electric heater supplies 1000 W/m2 of uniform heat flux to the plate. Determine the radiosity of the plate under these conditions.arrow_forward
- In what way does the glass act like a one-way valve for a conventional greenhouse? Does the atmosphere play the same role?arrow_forwardIn the heating seasons the heat loss from a building (and thus the heating cost) is strongly dependent on the difference between the indoor and outdoor temperature. If the average outdoor temperature in a particular city during the heating season is 45 F (7 C), what is the effect on heating cost percentage-wise if the thermostat setting is fixed at 74 F (23.3 F) instead of 68 F (20 C)?arrow_forwardAn aluminum rod 0.500 m in length and with a cross sectional area of 2.50 cm2 is inserted into a thermally insulated vessel containing liquid helium at 4.20 K. The rod is initially at 3(H) K. (a) If one-halt of the rod is inserted into the helium, how many liters of helium boil off by the time the inserted half cools to 4.20 K? Assume the upper half does not yet cool, (b) If the circular surface of the upper end of the rod is maintained at 300 K. what is the approximate boil-off rate of liquid helium in liters per second after the lower half has reached 4.20 K? (Aluminum has thermal conductivity of 3 100 YV/m K at 4.20 K; ignore its temperature variation. The density of liquid helium is 125 kg/m3.)arrow_forward
- Physics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning