A vertical slab of Wood’s metal is joined to a substrate onone surface and is incited as it is uniformly irradiated by alaser source on the opposite surface. The metal is initiallyat its fusion temperature of
(a) Neglecting heat transfer from the irradiated surfaceby convection or radiation exchange with thesurroundings, determine the instantaneous rate ofmelting in
(b) Allowing for convection to ambient air, with
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Fundamentals of Heat and Mass Transfer
- 1.26 Repeat Problem 1.25 but assume that the surface of the storage vessel has an absorbance (equal to the emittance) of 0.1. Then determine the rate of evaporation of the liquid oxygen in kilograms per second and pounds per hour, assuming that convection can be neglected. The heat of vaporization of oxygen at –183°C is .arrow_forwardDetermine the rate of radiant heat emission in watts per square meter from a blackbody at (a) 15C, (b) 600C, and (c) 5700C.arrow_forwardA long, horizontal, cylindrical steel reactor, 1 m in diameter, has a surface temperature of 300ºC. The emissivity of the steel is 0.6, and the heat transfer coefficient for natural convection is 5 W m−2 K−1 . Heat is lost by convection to the air at 15ºC, and also by radiation to the surroundings, which can be considered to be a black body at 15ºC. a) Calculate the total heat loss per metre length of the reactor, and the proportions lost by convection and radiation b) The reactor is then insulated with a thin layer of insulation material to reduce the total heat loss to one-tenth of its original value. This causes the surface temperature of the steel to rise to 400ºC. The thermal conductivity of the insulation is 0.01 W m−1 K−1 , and its surface emissivity is 0.2. Show that the resulting surface temperature of the insulation is about 89ºC, and calculate the thickness of insulation required, stating any assumptions made. Specifically need help with part barrow_forward
- A long, horizontal, cylindrical steel reactor, 1 m in diameter, has a surface temperature of 300ºC. The emissivity of the steel is 0.6, and the heat transfer coefficient for natural convection is 5 W m−2 K−1 . Heat is lost by convection to the air at 15ºC, and also by radiation to the surroundings, which can be considered to be a black body at 15ºC. a) Calculate the total heat loss per metre length of the reactor, and the proportions lost by convection and radiation. b) The reactor is then insulated with a thin layer of insulation material to reduce the total heat loss to one-tenth of its original value. This causes the surface temperature of the steel to rise to 400ºC. The thermal conductivity of the insulation is 0.01 W m−1 K−1 , and its surface emissivity is 0.2. Show that the resulting surface temperature of the insulation is about 89ºC, and calculate the thickness of insulation required, stating any assumptions made. can you solve part b please?arrow_forwardWhat would you expect the linear coefficient of absorption values of Aluminium, Cop- per and Lead to compare to one another. Would you expect the same relation between the mass absorption coefficients?arrow_forwardExplain and derive the rate equation for heat radiation given by Stefan Boltzmann.arrow_forward
- •A thin disk-shaped wafer (diameter-=30cm) is maintained at T=100oC. The wafer loses heat to the room by convection and radiation from its upper surface while heat is supplied constantly from below. Assuming the surrounding air at 20oC and all surrounding surfaces (isothermal/blackbodies) at T=15oC. How much heat (in W) must be supplied to the wafer? h wafer-air= 30W/m2K Emissivity of wafer’s surface(gray body)=0.85arrow_forwardAn infrared camera is used to measure a temperature at a tissue location. The infrared camera uses the same equation as that in the lecture notes. When the total hemispherical emissivity is selected as &=1.0, the temperature reading on the camera is 45°C. (a) Based on the equation given in the notes, please calculate the radiation heat flux received by the camera qck. The Stefan-Boltzmann's constant ois 5.67*108 W/(m²K¹). (b) However, you notice that the actual emissivity of the tissue surface should be 0.95. The room temperature is 20°C. Use the equation again to calculate the temperature of the tissue location, note that qck should be the same as in (a). What is the absolute error of the measurement if both the room temperature and deviation from a perfect blackbody surface are not considered?arrow_forwardQuestion No.13: a) What is a gray body? Derive the expression for radiation heat exchange between two gray surfaces connected by single refractory surface. b) A 60mm thick plate with a circular hole of 30mm diameter along the thickness is maintained at uniform temperature of 277°C. Find the loss of energy to the surroundings at 20°C, assuming that the two ends of the hole to be as parallel discs and the metallic surfaces and surroundings have black body characteristics.arrow_forward
- Hi, this is an design and essay problem. From thermodynamics You need to assume the temperature of the black surface to find the working potential. The Sun supplies electromagnetic energy to Earth. It appears to have an effective temperature of approximately 5,800 K. On a clear summer day in North America, the incident energy on a surface facing the Sun is approximately 0.95 kW / m2. Electromagnetic solar energy can be converted into thermal energy by being absorbed by a darkened surface. How could you characterize the work potential of solar energy when it is to be used to produce work?arrow_forwardHeat transfer problem.The internal surface area is an enclosure is 50 meter square. The surface is black and maintained at constant temperature. A small opening in the enclosure has area 0.05 meter square. The radiant power emitted from the opening is 52W. (A) what’s the temperature of the interior enclosure wall. (B)if the interior surface is maintained in this temperature, but polished so that emissivity is 0.15, what will be the radiant power emitted in the opening.arrow_forwardA pipe still uses 7110 lb per hour of a cracked gas (Net Heating Value (NHV) 20560 Btu per lb). The radiant section contains 1500 sq ft of projected area, and the tube (5 in. outside diameter) are spaced at a center-to-center distance of 10 in. there is only one row of radiant tubes, and they are 40 ft long. The ratio of air to fuel is (21 (30 percent excess air). a) What percentage of the heat liberation is absorbed in the radiant section? b) How many Btu are absorbed per hour through each square foot of projected area?arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning