Concept explainers
Fiberglass is a popular, economical, and fairly effective building insulation. It consists of fine glass fibers—often including recycled glass—formed loosely into rectangular slabs or rolled into blankets (Fig. 16.18). One side is often faced with heavy paper or aluminum foil. Fiberglass insulation comes in thicknesses compatible with common building materials—for example, 3.5 inch and 6 inch for wood-framed walls. Standard 6-inch fiberglass has an R-factor of 19.
One purpose of foil facing on fiberglass insulation is to reduce heat loss by
- a.
conduction . - b.
convection . - c.
radiation .
Want to see the full answer?
Check out a sample textbook solutionChapter 16 Solutions
Essential University Physics: Volume 1 (3rd Edition)
Additional Science Textbook Solutions
Physics: Principles with Applications
College Physics (10th Edition)
Conceptual Physical Science (6th Edition)
Glencoe Physical Science 2012 Student Edition (Glencoe Science) (McGraw-Hill Education)
Conceptual Physics (12th Edition)
Introduction to Electrodynamics
- An electric stove burner has surface area 325 cm² and emissivity e = 1. The burner consumes 1500 W and is at 900 K. If room temperature is 300 K, what fraction of the burner's heat loss is from radiation?arrow_forwardA thermal window, with an area of 6.0m ^ 2, is constructed of two layers of glass, each 4.0mm thick, separated from each other by a 5.0mm air gap. If the inner surface is at 20.0 ° C and the outer surface is at -5.0 ° C, what is the rate of energy transfer by conduction through the window? The thermal conductivity of glass is 0.8 W⁄ (m. ° C) and that of air is 0.023 W⁄ (m. ° C)arrow_forwardA classroom has dimensions 8.00 m x 10.00 m x 3.00 m. A 1000 W electric space heater is being used to warm the room from 5.00°C to 20.00°C on a cold morning. If the density of air is 1.29 kg/m°, and the specific heat capacity of air is 1004 J/(kg-K), how long will it take to heat the room? Assume no loss of thermal energy to the surroundings. A) 1.30 minutes B) 241 minutes C) 45.3 minutes O D) 77.7 minutesarrow_forward
- A small electric immersion heater is used to heat 94 g of water for a cup of instant coffee. The heater is labeled "81 watts" (it converts electrical energy to thermal energy at this rate). Calculate the time required to bring all this water from 21°C to 100°C, ignoring any heat losses. (The specific heat of water is 4186 J/kg.K.) Number Unitsarrow_forwardApproximately how long should it take 9.5 kg of ice at 0 °C to melt when it is placed in a carefully sealed Styrofoam ice chest of dimensions 25 cm × 35 cm x 55 cm whose walls are 1.1 cm thick? Assume that the conductivity of Styrofoam is double that of air and that the outside temperature is 35 °C. Express your answer using two significant figures. VE ΑΣΦ ? Sarrow_forwardYou have a mystery substance, length 2.0 m, cross section 0.40 m2 , and apply atemperature difference of 69°C across its length. If the substance conducts 1000.0 J ofheat in 0.50 sec, what is its thermal conductivity?arrow_forward
- Thermography is a technique for measuring radiant heat and detecting variations in surface temperatures that may be medically, environmentally, or militarily meaningful.(a) What is the percent increase in the rate of heat transfer by radiation from a given area at a temperature of 34.0C compared with that at 33.0C, such as on a person’s skin? (b) What is the percent increase in the rate of heat transfer by radiation from a given area at a temperature of 34.0C compared with that at 20.0C, such as for warm and cool automobile hoods?arrow_forwardWhat is the rate of heat transfer by radiation, with an unclothed person standing in a dark room whose ambient temperature is 22.0ºC . The person has a normal skin temperature of 33.0ºC and a surface area of 1.50 m2 . The emissivity of skin is 0.97 in the infrared, where the radiation takes place.arrow_forwardDuring a plant visit, it was noticed that a 12-m-long section of a 10-cm-diameter steam pipe is completely exposed to the ambient air. The temperature measurements indicate that the average temperature of the outer surface of the steam pipe is 75°C when the ambient temperature is 5°C. There are also light winds in the area at 10 km/h. The emissivity of the outer surface of the pipe is 0.8, and the average temperature of the surfaces surrounding the pipe, including the sky, is estimated to be 0°C. Determine the amount of heat lost from the steam during a 10-h-long work day. Steam is supplied by a gas-fired steam generator that has an efficiency of 80 percent, and the plant pays $1.05/therm of natural gas. If the pipe is insulated and 90 percent of the heat loss is saved, determine the amount of money this facility will save a year as a result of insulating the steam pipes. Assume the plant operates every day of the year for 10 h. State your assumptions.arrow_forward
- While swimming, conduction can play a big role in heat loss from the body. The body of one swimmer has a total surface area of 1.80 m2 and an average thickness of 1.60 mm. The skin's thermal conductivity is 0.370 W/m-K. If the water's temperature is 20.0°C, and the blood reaching the inner surface of the skin is at 37.0°C, what is the rate of energy loss for that person through conduction?arrow_forwardIce of mass 10.0 kg at 0.00° C is placed in an ice chest. The ice chest has 2.00 cm thick walls of thermal coductivity 1.00 x 10^-5 kcal/s-m-C° and a surface area of 1.30m^2. (a) How much heat must be absorbed by the ice before it melts? (b) If the outer surface of the ice chest is at 30.0° C, how long will it take for the ice to melt?arrow_forwardA ceramic mug is at a temperature of 343 K (about 160°F). The mug has a surface area of about 0.03 m² and ceramic has an emissivity of about 0.9. If the ambient temperature of the room is 293 K (about 70°F), what is the net rate at which energy is lost from the mug by radiation?arrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning