![Introduction to Heat Transfer](https://www.bartleby.com/isbn_cover_images/9780470501962/9780470501962_largeCoverImage.gif)
A dormitory at a large university, built 50 years ago, hasexterior walls constructed of
![Check Mark](/static/check-mark.png)
Want to see the full answer?
Check out a sample textbook solution![Blurred answer](/static/blurred-answer.jpg)
Chapter 3 Solutions
Introduction to Heat Transfer
- 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.arrow_forwardAs a designer working for a major electric appliance manufacturer, you are required to estimate the amount of fiberglass insulation packing (k = 0.035 W/m K) that is needed for a kitchen oven shown in the figure below. The fiberglass layer is to be sandwiched between a 2-mm-thick aluminum cladding plate on the outside and a 5-mm-thick stainless steel plate on the inside that forms the core of the oven. The insulation thickness is such that the outside cladding temperature does not exceed 40C when the temperature at the inside surface of the oven is 300C. Also, the air temperature in the kitchen varies from 15Cto33C, and the average heat transfer coefficient between the outer surface of the oven and air is estimated to be 12.0W/m2K. Determine the thickness of the fiberglass insulation that is required for these conditions. What would be the outer surface temperature when the inside surface of the oven is at 475C?arrow_forward1.2 The weight of the insulation in a spacecraft may be more important than the space required. Show analytically that the lightest insulation for a plane wall with a specified thermal resistance is the insulation that has the smallest product of density times thermal conductivity.arrow_forward
- 2.30 An electrical heater capable of generating 10,000 W is to be designed. The heating element is to be a stainless steel wire having an electrical resistivity of ohm-centimeter. The operating temperature of the stainless steel is to be no more than 1260°C. The heat transfer coefficient at the outer surface is expected to be no less than in a medium whose maximum temperature is 93°C. A transformer capable of delivering current at 9 and 12 V is available. Determine a suitable size for the wire, the current required, and discuss what effect a reduction in the heat transfer coefficient would have. (Hint: Demonstrate first that the temperature drop between the center and the surface of the wire is independent of the wire diameter, and determine its value.)arrow_forward2.2 A small dam, which is idealized by a large slab 1.2 m thick, is to be completely poured in a short Period of time. The hydration of the concrete results in the equivalent of a distributed source of constant strength of 100 W/m3. If both dam surfaces are at 16°C, determine the maximum temperature to which the concrete will be subjected, assuming steady-state conditions. The thermal conductivity of the wet concrete can be taken as 0.84 W/m K.arrow_forwardA steam pipe (inner diameter = 150 mm and outer diameter = 160 mm) havingthermal conductivity 58 W/m. °C is covered with two layers of insulation, ofthickness 30 mm and 50 mm respectively and thermal conductivities 0.18 W/m. °Cand 0.09 W/m .°C respectively. The temperature of the inner surface of steam pipeis 320°C and that of the outer surface of the insulation layers is 40°C.Determine the quantity of heat lost per meter length of steam pipe and layercontact temperature,arrow_forward
- If the rate of heat flow through a furnace wall is 0.94 kW/m². The wall consisting of 0.20 m thick inner layer of chrome brick, a center layer of kaolin brick of 10.0 cm and an outer layer of masonry brick 100 mm thick, having a thermal conductivity of 1.25 W/m°C , 0.74x10ª kW/m°C_and 0.555x10³ kW/m°C respectively. The unit surface conductance at the inner surface is 74 W/m2 °C and the outer surface temperature is 70 °C . The temperature of the gases inside the furnace is 1670 °C , assume steady heat flow, Calculate the following: 1- The temperatures of the gases inside the furnace. 2- The interior surface temperature of the inner and outer layers.arrow_forwardA 10-m-long, 5-cm-outer-radius cylindrical steam pipe is covered with 3-cm thick cylindrical insulation with a thermal conductivity of 0.05 W/m. °C. If the rate of heat loss from the pipe is 1000 W, what would be the temperature drop (in °C) across the insulation? Select one: O a. 163°C b. 48°C c. 79°C d. 150°C e. 600°Carrow_forwarda flat wall is covered with a layer of insulation 1.0 in. thick whose thermal conductivity is 0.8 Btu/hr-ft- F. the temperature of the wall on the inside of the insulation is 600F. the wall loses heat to the environment by convection on the surface of the insulation. the average value of the convection heat transfer coefficient on the inslation surface is 950 Btu/hr-ft^2-F. compute the bulk temperature of the environment if the outer surface of the insulation does not exceed 105 F.arrow_forward
- Consider a A = 11.0000 m² wall with two layers of insulation: d = 16 cm of brick wall and d = 12 cm of styrofoam. Temperature outside is Tout = 3 °C and T = 12 °C between styrofoam and brick layers. Heat flow through the wall is measured for t = 10 h d = 12 cm d = 16 cm Outside Tu = 3°C foam Inside T₂ A = 11.0 m² k=0.01 W/(mK = 12 °C k=0.8 W/(mK) $ system of coordinates What is the heat flow through the wall divided by wall area? What is the inside temperature? °C Tin What is the heat flow (power) through the wall? P = W What is the amount of heat passed through the wall? Q =arrow_forwardQuestion 6 A steel pipe (k = 48 W/m-K) of a heating system carries wet steam at 120 °C. The inner and outer diameters of the pipe are 15 cm and 16 cm respectively. The pipe is insulated on the outside with rockwool insulation (k = 0.05 W/m K) of thickness 8 cm. The ambient air temperature is 32 °C. The outside heat transfer coefficient is 20 W/m2-K. The thermal resistance between the inner pipe surface and the steam is negligible. Calculate the rate of heat flow (in W) from the steam to the ambient over a 5 m length of pipe. Round your answer to 2 decimal places. Add your answer Follow-up question to Question 6, calculate the temperature (in °C) of the outer surface of the insulation. Round your answer to 2 decimal places. Add your answer Follow-up question to Question 6, calculate the rate of condensation of steam (in kg/hr) over the 5-m lenzth of pipe if the latent heat of steam is 2200 k/kg. Rc und your answer to 2 decimal places. Add your answerarrow_forward213arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning
![Text book image](https://www.bartleby.com/isbn_cover_images/9781305387102/9781305387102_smallCoverImage.gif)