To save fuel during the heating season it is suggested that glass windowsbe covered at night with a 1.2 cm layer of polystyrene. Estimate thepercent savings in energy and discuss the feasibility of this idea. Showthe thermal circuit with and without the insulation panel. Consider a typicalcase of 0.2 cm thick window glass with inside and outside heat transfercoefficients of 6 and 32 W/m²-ºC.Lg←←LphT₁T。gkpinsulation panel

During cold weather, heat escapes through windows. The idea here is to cover a window at night with…

Answered: To save fuel during the heating season…

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.

Chapter9: Heat Transfer With Phase Change

Section: Chapter Questions

Problem 9.12P

See similar textbooks

Similar questions

1.10 A heat flux meter at the outer (cold) wall of a concrete building indicates that the heat loss through a wall of 10-cm thickness is . If a thermocouple at the inner surface of the wall indicates a temperature of 22°C while another at the outer surface shows 6°C, calculate the thermal conductivity of the concrete and compare your result with the value in Appendix 2, Table 11.
a pipe with an outside diameter of 2.7 inches. insulate with a 2 inches. layer of asbestos (ka = 0.396 btu-in./hr-ft-F), followed by a layer of cork 1.5 inches. thick (kc = 0.30 btu-in/hrft-F). if the temperature of the outer surface of the cork is 91 F, calculate the heat lost per 100 ft of insulate pipe. The temp of the inner surface of the pipe is 275 F.
what id correct ans
Build a spreadsheet to do the step by step method for estimating the temperature of unprotected steel work exposed to the ASTM E119 Standard Fire. Assume a convective heat transfer coefficient of 25 W/m2K and an emissivity of 0.5. Assume the specific heat to remain constant at 600 J/kgK. Use a time step of 30 seconds and an ambient temperature of 20°C. Provide an Excel plot showing the curves of the fire and a steel member through a time of 60 minutes with F/V ratios of: a)25 m-1 b)100 m-1 c)200 m-1 d)300 m-1 Note your plot should contain 5 curves. One for the fire and one for each of the F/V values. Also on the spreadsheet, highlight in green, the cells identifying the temperature of the unprotected steel member with an F/V of 200m-1 at the following times: a)3 minutes b)10 minutes c)20 minutes d)50 minutes
1. A small metal building is to be constructed of corrugated steel sheet walls with a total wall surface area of about 300 m². The air conditioner consumes about 1 kW of electricity for every 4 kW of cooling supplied and two wall construction are to be compared on the basis of cooling costs. Assume that electricity costs S0.15/kWh. Determine the electrical energy savings per week of using 260 mm of fiberglass batt insulation to the steel sheet wall (U-0.17 W/m² "C) instead of 159 mm of fiberglass insulation (U-0.31 W/m² °C) assuming an overall temperature difference of 20 °C across the wall.
Q2/ An insulated steam pipe having an outside Steam pipe diameter of 30 mm is to be covered with two Better ination (4) Paer ination () layers of insulation, each haying thickness of 20 mm. The thermal conductivity of one material is 5 times that of the other. Sm L 1. Assuming that the inner and outer surface temperatures of composite insulation are fixed, how much will heat transfer be increased when better insulation material is next to the pipe than it is the outer layer?
A pipe with an outside diameter of 3.5 in. is insulated with a 3 in. layer of asbestos (ka=0.396 BTU-in/hr- ft2 - 0 F), followed by a layer of cork 1.5 in. thick (kc=0.30 BTU-in/hr-ft2 - 0 F). If the temperature of the outer surface of the cork and pipe is 1000 F and 3000 F, respectively, calculate the heat lost per 100ft or insulated pipe.
The section of a vertical wall is made up of fiberglass insulation slabs separated by wooden studs. The thermal conductivity of fiberglass and wood are 0.04 W/m∙K and 0.18 W/m∙K, respectively. The thickness of the wall is 180 mm. The temperatures of the inner and outer surfaces of the wall section are 23.5 °C and 4.7 °C, respectively. The ratio of the insulation area to the total wall area is 0.8. Calculate the total heat flow rate (in W/m2) through the wall per unit area.
A 0.083 inch diameter electrical wire at 115◦F is covered by0.02 inch thick plastic insulation with k = 0.075(Btu/h.ft.◦F). The wire is exposed to a medium at 50◦F,with a combined convection and radiation heat transfercoefficient of 2.5 Btu/(h.ft2. ◦F). Determine if the plasticinsulation on the wire will increase or decrease heat transferfrom the wire.
Energy management and Audit question A steam main 150mm outside diameter containing wet steam at 28 bar is insulated with an inner layer of diatomaceous earth, 40mm thick, and an outer layer of 85% magnesia, 25mm thick. The inside surface of the pipe is at the steam temperature, and the heat transfer coefficient for the outside surface of the lagging is 17 W/m2 K. The thermal conductivities of diatomaceous earth and 85% magnesia are 0.09, and 0.06 W/m K respectively. Neglecting radiation, and the thermal resistance of the pipe water flow rate is 1400 kg/h. Taking the specific heat capacity of water as 4.19 kj/kg K, calculate; The required pipe length for parallel-flow The required pipe length for counter-flow
Answer within 10 minutes : The temperature at the inside surface of an oven is 460 oF. The inside wall of the oven is made of brick and is 8 inch thick. The thermal conductivity of the brick is 2.2 Btu/hr.ft2.(oF/ft). The outside of the oven is covered with a 3-inch layer of asbestos as insulation, which has a thermal conductivity of 0.11 Btu/hr.ft2.(oF/ft). If the outer surface of the insulation has a temperature of 100 oF , calculate the amount of heat lost through 2 ft2 of wall area in 3 hours.
On a multi-layered square wall, the thermal resistance of the first layer is 0.005 ° C / W, the resistance of the second layer is 0.3 ° C / W, and the third layer is 0.1 ° C / W. The overall temperature gradient in the wall is multilayered from one side. to the other side is 50 ° C. a. Determine the heat flux through the walls. = Answer watts / m2. b. If the thermal resistance of the second layer is changed to 0.1 ° C / W, what is the effect in% on heat flux, assuming the temperature gradient remains the same? = AnswerAnswer %.

SEE MORE QUESTIONS

Recommended textbooks for you

Principles of Heat Transfer (Activate Learning wi…

Mechanical Engineering

ISBN:

9781305387102

Author:

Kreith, Frank; Manglik, Raj M.

Publisher:

Cengage Learning