Concept explainers
A 6-mm-thick stainless steel strip
Want to see the full answer?
Check out a sample textbook solutionChapter 4 Solutions
Heat and Mass Transfer: Fundamentals and Applications
- asaparrow_forwardIndirect Cooling With Liquid Nitrogen. You are designing a system to cool an insulated silver plate of dimensions 2.00 cm × 2.00 cm × 0.60 cm. One end of a thermally insulated copper wire (diameter D = 2.70 mm and length L = 18.0 cm) is dipped into a vat of liquid nitrogen (T = 77.2 K), and the other end is attached to the bottom of the silver plate.(a) If the silver plate starts at room temperature (65.0 °F), what is the initial rate of heat flow between the plate and the liquid nitrogen reservoir?(b) Assuming the rate of heat flow calculated in part (a), estimate the temperature of the silver plate after 30.0 seconds.arrow_forwardA slab of aluminium 10 cm thick is originally at a temperature of 500°C. It is suddenly immersed in a liquid at 100°C resulting it a heåt transfer coefficient of 1200. W/m2K. Determine the temperature at the center line and the surface 1 min after the immersion. Also the total thermal energy removal per unit area of slab during this period. The properties of aluminium for the given condition are, a = 8.4 x 10-5 m?/s, k =215 W/mK, p = 2700 kg/m3, C= 0.9.kJ/kgK.arrow_forward
- H.W. Q: An aluminum pan whose thermal conductivity is 237 W/m-°C has a flat bottom with diameter 20 cm and thickness 0.4 cm. Heat is transferred steadily to boiling water in the pan through its bottom at a rate of 800 W. If the inner surface of the bottom of the pan is at 105°C, determine the temperature of the outer surface of the bottom of the pan. 105°C 0.4 cm Answer: T= 105.43 °C 800 W 7arrow_forwardTake note that both sides of the plate are exposed to convection.arrow_forwardIndirect Cooling With Liquid Nitrogen. You are designing a system to cool an insulated silver plate of dimensions 2.00 cm × 2.00 cm x 0.40 cm. One end of a thermally insulated copper wire (diameter D = 2.70 mm and length L = 12.0 cm) is dipped into a vat of liquid nitrogen (T = 77.2 K), and the other end is attached to the bottom of the silver plate. (a) If the silver plate starts at room temperature (73.0°F), what is the initial rate of heat flow between the plate and the liquid nitrogen reservoir? (b) Assuming the rate of heat flow calculated in part (a), estimate the temperature of the silver plate after 30.0 seconds.arrow_forward
- A flat cereal has a thickness of 2L =1.2mm . The specific mass, specific heat and thermal conductivity of the cereal are, respectively, 700 Kg/m³ and 0.34 W/m*K. The product must be baked, raising its temperature from 20°C to 220°C , in a convective oven with a 3-meter-long conveyor belt. The convection heat transfer coefficient is 55 W/K*m? and its temperature is 300 °C. Determine: a) Is the global capacitance hypothesis valid? b) What speed is needed for the treadmill? c) An engineer suggests that if the grain thickness is reduced to 2L=1mm, the belt speed can be increased, resulting in higher productivity. What would the belt speed be for this new grain thickness?arrow_forwardShown below is an insulated copper block that receives energy at a rate of 100 W from anembedded resistor. If the block has a volume of 10-3 m3and an initial temperature of 20oC, howlong would it take, in minutes, for the temperature to reach 60oC? Copper has a specific heatcapacity ccu = 0:385 kJ/ kg.K and a density of cu = 8930 kg/m3.arrow_forwardA concrete slab of a basement is 11m long, 8m wide and 0.20m thick. During the winter, temperatures are nominally 17C and 10C at the top and bottom surfaces. The concrete has a thermal conductivity of 1.4W/m-K, The basement is heated by a gas furnace operating at an efficiency of 0.90 and natural gas is priced at $0.001/MJ. What is the daily cost of heat loss in dollars?arrow_forward
- A vertical furnace wall is made-up on an inner wall of firebrick 20 cm thick followed by insulating brick 15 cm thick and an outer wall of steel 1 cm thick. The surface temperature of the wall adjacent to the combustion chamber is 1200oC while that of the outer surface of steel is 50oC. The thermal conductivities of the wall material in W/m-K are firebrick, 10; insulating brick, 0.26; and steel, 45; neglecting film resistances and contact resistance of joints, determine the percent of the total maintenance due to insulating brick.arrow_forwardAn ordinary egg can be approximated as a 5.5-cm-diameter sphere whose thermal conductivity of roughly W overall density of p= 1000. mk' kg m² and heat capacity of Cp = 3000; kgk k = 0.6- : The egg is initially at a uniform temperature of T₁ = 10°C and is dropped into boiling water at T = 90°C Taking the convective heat transfer coefficient to be h = 10. - determine how long it will take for the egg to W m²K reach T = 70°C. In solving this problem, please use the One-term approximation model to compute the time needed by the center of the egg and the surface of the egg to reach the desired temperature of 70 C Please discuss the difference between the three results. In solving the problem, please follow the steps below. For the One-term approximation: 1. Compute the Biot number, use the egg radius (not the diameter) as the characteristic length T-Too 2. Compute the non-dimensional excess temperature 0 = Ti-Too 3. Look up in the table the values for A₁ and ₁ for the Biot number found…arrow_forwardA long rod of AISI 4130 steel initially at a uniform temperature of 400°C is suddenly exposed to 20°C air, where the heat transfer coefficient is 15 W/m2-K. The rod has a diameter of 4.8 cm. How long after being exposed to the 20°C air will the steel rod reach a temperature of 60°C? The properties of the rod are p = 7840 kg/m³, Cp = 460 J/kg.K and k = 43 W/m.K.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning