The concrete slab of a basement is 11 m long, 8 m wide, and 0.20 m thick. During the winter, temperatures are nominally
Want to see the full answer?
Check out a sample textbook solutionChapter 1 Solutions
Introduction to Heat Transfer
- 2.34 Show that the temperature distribution in a sphere of radius . made of a homogeneous material in which energy is released at a uniform rate per unit volume , isarrow_forwardExample 10: Consider a long resistance wire of radius r1 = 0.2 cm and thermal conductivity kwire = 15 W/m·°C in which heat is generated uniformly as a result of resistance heating at a constant rate of g = 50 W/cm3. The wire is embedded in a 0.5-cm-thick layer of ceramic whose thermal conductivity is kceramic = 1.2 W/m·°C. If the outer surface temperature of the ceramic layer is measured to be Ts = 45°C, determine the temperatures at the center of the resistance wire and the interface of the wire and the ceramic layer under steady conditions.arrow_forwardDetermine the time needed to decrease the temperature of a solid cylinder from 40 C to 35 C if the ambient temperature is equal to 31 C. The cylinder has a length equals to 0.9 m and diameter equals to 100 mm. The heat convective coefficient is equal to 9 W/m^2.K. The cylinder has a conductivity equals to 2 W/m.K, a density equals to 1200 kg/m^3 and its Cp is equal to 4.700 kJ/kgK.arrow_forward
- A 6 in thick concrete wall, having thermal conductivity k =0.50 Btu/h ft F, is exposed to air at 70°F on one side and air at 20°F on the opposite side. The heat transfer coefficients are h=2.0 Btu/h. ft² ° F on the 70°F side and =10 Btu/h .ft².0 F on the 20°F side. Determine the heat transfer ratearrow_forwardA brass wire of 0.8 mm in diameter and 12 m long is annealed in an annealing furnace at a temperature of 400°C. Find the time required for the wire to reach the temperature of 150°C if the temperature of the wire before placing it inside the furnace is 30°C. Take h = 35 W/m2 K. Density = 8500 kg/m3. Specific heat = 0.335 kJ/kg K.arrow_forwardThe wall of a house, 8.09 m wide and 6.70 m high is made from a thick bricklayer with thermal conductivity λ = 0.69 W/mK. The surface temperature on theinside & outside of the wall is 27ºC & 8 ºC respectively. Determine the heatenergy transfer rate and thickness of the wall, if energy loss is 10139 kJ in 9 hours.arrow_forward
- Determine the time needed to decrease the temperature of a solid cylinder from 40 C to 35 C if the ambient temperature is equal to 31 C. The cylinder has a length equals to 0.9 m and diameter equals to 100 mm. The heat convective coefficient is equal to 1.3 W/m^2.K. The cylinder has a conductivity equals to 2 W/m.K, a density equals to 1200 kg/m^3 and its Cp is equal to 4.700 kJ/kgK. Select one: a. 83325 s O b. 10500s O c. 45360 s O d. 30050 sarrow_forwardA wall of length "L" m and height "H" m is made from a thick bricklayer of 20 cm with thermal conductivity of 0.59 W/mK is subjected to heat transfer due to the outside temperature as 38 oC and inside temperature 24 oC. If the energy loss is 12867 kJ in 9 hours. Determine the Heat transfer rate, Surface Area and Length and Height of the wall, if L = 2 H. Solution: Heat Transfer Rate (in Joule/Sec) = Surface Area of the Wall (in m2) = Height of the Wall (H in m) = Length of the Wall (L in m) =arrow_forwardIt is desired to keep the interior of a refrigerator at 2 °C whose dimensions at the base are 0.8 x 0.8 m and the height is 1.9 m. The walls of the refrigerator are made of two sheets of steel, 0.28 cm thick with 3 cm of fiberglass insulation. The interior and exterior coefficients are, respectively, 10 W/m^2 °C and 15 W/m^2 °C. If the ambient temperature in the kitchen is 30°C, estimate the heat flux that must be extracted to maintain the specified conditions. Make a proposal to prevent heat from entering the refrigerator.arrow_forward
- 3. A 2-mm-diameter and 10-m-long electric wire is tightly wrapped with a 1-mm-thick plastic cover whose thermal conductivity is k = 0.15 W/m· °C. Electrical measurements indicate that a current of 10 A passes through the wire and there is a voltage drop of 8 V along the wire. If the insulated wire is exposed to a medium at T = 30°C with a heat transfer coefficient of h = 24 W/m2 · °C, determine the temperature at the interface of the wire and the plastic cover in steady operation. Also determine if doubling the thickness of the plastic cover will increase or decrease this interface temperature. T = 30°C Electrical wire Insulationarrow_forwardIn the context of a Spark Ignition (SI) engine, consider a moment during combustion when there is a heat flux through the wall of the combustion chamber at a specific location, measured at 219 kW/m2. The gas temperature within the cylinder at this time is 2300 K, and the convection heat transfer coefficient within the cylinder is 120 W/m2⋅K. The coolant temperature is 80 °C. The thickness of the cylinder wall is 10mm with a thermal conductivity of 200 W/m⋅K. (a) Determine the temperature of the inner surface of the cylinder wall. (b) Find the temperature on the side of the cylinder wall facing the coolant. (c) Calculate the heat transfer coefficient on the coolant side of the cylinder wallarrow_forwardA wall of length "L" m and height "H" m is made from a thick bricklayer of 31 cm with thermal conductivity of 0.5 W/mK is subjected to heat transfer due to the outside temperature as 38 °C and inside temperature 27 °C. If the energy loss is 12702 kJ in 10 hours. Determine the Heat transfer rate, Surface Area and Length and Height of the wall, if L = 4 H.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning