A typical home may require a total of 2.00 * 103kWhof energy per month. Suppose you would like to obtain thisenergy from sunlight, which has an average daylight intensity of1.00 * 103W>m2. Assuming that sunlight is available 8.0 h perday, 25 d per month (accounting for cloudy days), and that youhave a way to store energy from your collector when the Sun isn’tshining, determine the smallest collector size that will providethe needed energy, given a conversion efficiency of 25%.

A typical home may require a total of 2.00 * 103kWhof energy per month. Suppose you would like to obtain thisenergy from sunlight, which has an average daylight intensity of1.00 * 103W>m2. Assuming that sunlight is available 8.0 h perday, 25 d per month (accounting for cloudy days), and that youhave a way to store energy from your collector when the Sun isn’tshining, determine the smallest collector size that will providethe needed energy, given a conversion efficiency of 25%.

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter1: Temperature And Heat

Section: Chapter Questions

Problem 119AP: For the human body, what is the rate of heat transfer by conduction through the body's tissue with...

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For the human body, what is the rate of heat transfer by conduction through the body's tissue with the following conditions: the tissue thickness is 3.00 cm, the difference in temperature is 2.00 , and the skin area is 1.50 m2. How does this compare with the average heat transfer rate to the body resulting from an energy intake of about 2400 kcal per day? (No exercise is included.)
One easy way to reduce heating (and cooling) costs is to add extra insulation in the attic of a house. Suppose a single-story cubical 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, by what percentage would the heating cost of the house drop? Take the house to have dimensions 10 m by 15 m by 3.0 m. Ignore air infiltration and heat loss through windows and doors, and assume that the interior is uniformly at one temperature and the exterior is uniformly at another.
Many decisions are made on the basis of the payback period: the time it will take through savings to equal the capital cost of an investment. Acceptable payback times depend upon the business or philosophy one has. For some industries, a payback period is as small as 2 yeas) Suppose you wish to install the extra insulation in the preceding problem. If energy cost $1.00 per million joules and the insulation was $4.00 per square meter, then calculate the simple payback time. Take the average T for the 120-day heating season to be 15.0 .
An astronaut performing an extra-vehicular activity (space walk) shaded from the Sun is wearing a spacesuit that can be approximated as perfectly white ( e=0 ) except for a 5 cm × 8 cm patch in the form of the astronaut's national flag. The patch has emissivity 0.300. The spacesuit under the patch is 0.500 cm thick, with a thermal conductivity k 0.0600 W/m , and its inner surface is at a temperature of 20.0 . What is the temperature of the patch, and what is the rate of heat loss through it? Assume the patch is so thin that its outer surface is at the same temperature as the outer surface of the spacesuit under it. Also assume the temperature of outer space is 0 K. You will get an equation that is very hand to solve in closed form, so can solve it numerically with a graphing calculator, with software, or even by trial and error with a calculator.
A certain steel railroad rails 13 yd in length and weighs 70.0 lb/yd How much thermal energy is required to increase the length of such a rail by 3.0 mm? .Note: Assume the steel has the same specific heal as iron.
A water heater is operated by solar power. If solar collector has an area of 6.00m2 , and the Intensity delivered by sunlight is 550W/m2 , how long does it take to increase the temperature of 1m3 of water from 20°Cto 60°C?
The Greenland ice sheet is thought to affect (or be affected by) climate in the North Atlantic and Europe, and is currently more than 100,000 years old. The sheet is of the order of 2400x1100 km in surface area and 2.5 km deep. If the energy imbalance to the sheet is such that it is getting a net of 250 watts/m2 energy coming in, how long will it take for it to melt? The heat of fusion of water is 334 J/g. A millennium, 1000 years The time scale between the beginning of ice ages, or the order of 100,000 years The duration of civilization as we know it, 10,000 years About 1 century, 100 years
Lake Erie contains roughly 4.50E+11 m3 of water. How much heat is required to raise the temperature of that volume of water from 11.5°C to 12.1°C? How many years would it take to supply this amount of heat by using the full output of a 1150 MW electric power plant?
Solar radiation is incident on a 5 m2 solar absorberplate surface at a rate of 800 W/m2. Ninety-three percent ofthe solar radiation is absorbed by the absorber plate, whilethe remaining 7 percent is reflected away. The solar absorberplate has a surface temperature of 40°C with an emissivityof 0.9 that experiences radiation exchange with the surroundingtemperature of -5°C. In addition, convective heat transferoccurs between the absorber plate surface and the ambientair of 20°C with a convection heat transfer coefficient of7 W/m2∙K. Determine the efficiency of the solar absorber,which is defined as the ratio of the usable heat collected bythe absorber to the incident solar radiation on the absorber.
What is the average energy contained in a 1.00 m3volume near the Earth’s surface due to radiant energyfrom the Sun?
During heavy exercise, the body pumps 2.00 L of blood per minute to the surface, where it is cooled by 2.00ºC . What is the rate of heat transfer from this forced convection alone, assuming blood has the same specific heat as water and its density is 1050 kg/m? (answer in W)
(a) Cherry-red embers in a fireplace are at 850ºC and have an exposed area of 0.200m2 and an emissivity of 0.980. The surrounding room has a temperature of 18.0ºC. If 50% of the radiant energy enters the room, what is the net rate of radiant heat transfer in kilowatts? (b) Does your answer support the contention that most of the heat transfer into a room by a fireplace comes from infrared radiation?