The thermal conductivity of a sheet of rigid, extrudedinsulationis reported to be
(a) What is the heat flux through a
(b) What is the rate of heat transfer through the sheet of insulation?
(a)
Heat Flux through a Sheet of insulation of dimension
Answer to Problem 1.1P
Heat Flux through a Sheet of insulation of dimension
Explanation of Solution
Given:
Thermal conductivity of insulation is
Thickness of Sheet is
Temperature difference through sheet is
Dimension of sheet is
Concept used:
Write the expression for heat flux passing through the sheet of insulation.
Here,
Calculation:
Substitute
Conclusion:
Thus, heat Flux through a Sheet of insulation of dimension
(b)
Rate of heat transfer through sheet of insulation.
Answer to Problem 1.1P
Rate of heat transfer through sheet of insulation is
Explanation of Solution
Concept used:
Calculate the area of rectangular sheet as follows:
Write the expression for rate of heat transfer.
Calculation:
Substitute
Conclusion:
Thus, rate of heat transfer through sheet of insulation is
Want to see more full solutions like this?
Chapter 1 Solutions
Fundamentals of Heat and Mass Transfer
- 2.38 The addition of aluminum fins has been suggested to increase the rate of heat dissipation from one side of an electronic device 1 m wide and 1 m tall. The fins are to be rectangular in cross section, 2.5 cm long and 0.25 cm thick, as shown in the figure. There are to be 100 fins per meter. The convection heat transfer coefficient, both for the wall and the fins, is estimated to be K. With this information determine the percent increase in the rate of heat transfer of the finned wall compared to the bare wall.arrow_forward1.37 Mild steel nails were driven through a solid wood wall consisting of two layers, each 2.5-cm thick, for reinforcement. If the total cross-sectional area of the nails is 0.5% of the wall area, determine the unit thermal conductance of the composite wall and the percent of the total heat flow that passes through the nails when the temperature difference across the wall is 25°C. Neglect contact resistance between the wood layers.arrow_forward1.10 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.arrow_forward
- A 10-cm diameter pipe is covered by 2 layers of lagging. The insidelayer is 4 cm thick and has a coefficient of thermal conductivity of 0.08W/m-K. The outside layer is 3cm thick and has a coefficient of thermalconductivity of 0.15 W/m-K. The steam main conveys steam apressure of 1.7 MPa with 25 C superheat. The outside temperature ofthe lagging is 27 C. If the steam main is 30 m long, determine theinterface temperature of the lagging and overall coefficient of heattransfer based on outside area.arrow_forwardA 50-cm-diameter pipeline in the Arctic carries hot oil at 30°C and is exposed to a surrounding temperature of −12°C. A special powder insulation 5 cm thick surrounds the pipe and has a thermal conductivity of 7 mW/m°C. The convection heat transfer coefficient on the outside of the pipe is 9 W/m2°C. Estimate the energy loss from the pipe per meter of length.arrow_forwardA 2 cm thick steel pipe (thermal conductivity 43 W/[m °C]) with 6 cm inside diameter is being used to convey steam from a boiler to process equipment for a distance of 40 m. The inside pipe surface temperature is 115°C, and the outside pipe surface temperature is 90°C. If there is 600kW of heat loss, what is the thickness of the pipe?arrow_forward
- Find the minimum amount of diameter for the insulation of a spherical water tank? Radius of the tank is 10 m, thermal conductivity is 25 W/(m^2*K) and convective coefficient is 5 W/(m*K) 8 m not sufficient information 10 m 20 m 15 marrow_forwardIn a thermal power plant, a horizontal copper pipe of "D" diameter, "L" length and thickness 1.7 cm enters into the boiler that has the thermal conductivity as 0.3 W/mK. The boiler is maintained at 107degreeC and temperature of the water that flows inside the pipe is at 31degreeC. If the energy transfer (Q) is 124925 kJ in 7 hours. Determine the Heat transfer rate, Surface area of the pipe and Diameter & Length of the pipe, if D = 0.012 L.Change in Temperature (in K) Heat Transfer Rate (in W) Surface Area of the Pipe (m2) Pipe Length (in m) Pipe Diameter (in mm)arrow_forwardPin fins are provided to increase the heat transfer from a hot surface. The perimeter of each fin is 4cm and its cross section area is 2 cm². The thermal conductivity of fin material is 200 W / mK. The fin base temperature is 230 ° C, the ambient air temperature is 30 ° C and the heat transfer coefficient is 20 W / (m²K). The fins are assumed of negligible end loss Which of the following arrangements will give higher heat transfer rate? (1) 6 fins of 10 cm length. (2) 12 fins of 5 cm lengtharrow_forward
- 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.arrow_forwardThe inner diameter of a pipe made of %1 C steel used in the drying machine of a textile factory is D1 = 160 mm and the thread diameter is D₂= 170 mm. The pipe is insulated with 25 mm thick glass wool. The heat transfer coefficient between the air and the pipe surface at 90 °C temperature inside the pipe is 80 W/m²K. The temperature of the ambient air outside the insulation is 20 °C and the air comes perpendicular to the cat wool surface at a speed of 10 m/s. Find the total heat transfer coefficient according to the inside diameter of the pipe. Calculate the heat transfer per unit length of pipe per unit time ?arrow_forwardConsider a closed cylindrical reactor vessel of diameter D= 1 ft, and length L= 1.5 ft. The surface temperature of the vessel, T1, and the surrounding temperature, T2, are 390 deg. F and 50 deg. F, respectively. The convective heat transfer coefficient, h, between the vessel wall and surrounding fluid is 4.0 Btu/h . ft . ⁰F. Calculate the thermal resistance in ⁰F .h/Btu.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning