13.21 Consider coaxial, parallel, black disks separated a dis- tance of 0.20 m. The lower disk of diameter 0.40 m is maintained at 500 K and the surroundings are at 300 K. What temperature will the upper disk of diame- ter 0.20 m achieve if electrical power of 17.5 W is supplied to the heater on the back side of the disk? -Heater j0.20 m 0.20 m 500 K -0.40 m-
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- 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 .1.25 A spherical vessel, 0.3 m in diameter, is located in a large room whose walls are at 27°C (see sketch). If the vessel is used to store liquid oxygen at –183°C and both the surface of the storage vessel and the walls of the room are black, calculate the rate of heat transfer by radiation to the liquid oxygen in watts and in Btu/h.Two large parallel plates with surface conditions approximating those of a blackbody are maintained at 816C and 260C, respectively. Determine the rate of heat transfer by radiation between the plates in W/m2 and the radiative heat transfer coefficient in W/m2K.
- Determine the power requirement of a soldering iron in which the tip is maintained at 400C. The tip is a cylinder 3 mm in diameter and 10 mm long. The surrounding air temperature is 20C, and the average convection heat transfer coefficient over the tip is 20W/m2K. The tip is highly polished initially, giving it a very low emittance.4. The surface temperature of a planet is T, and the measured temperature is Tm (i.e. the temper- ature measured at the top-of-atmosphere based on the upwards flux Ft there). Assume radiative equilibrium. (a) Show that the infrared optical depth of the planet's surface 7 is related to the surface temperature T, and the measured temperature Tm by Calculate the infrared optical depth at the surfaces of (a) Earth, where T, = 300 K and Tm = 250 K. (b) Venus, where T, = 750 K and Tm = 230 K. (c) Mars, where T, = 240 K and T, = 220 K.Heat 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.
- At the start of the following situation, determine the heat transfer contributions of each heat transfer pathway, and state the direction of each heat transfer and which dominates. A 1m diameter ball of iron is immersed in stagnant liquid water; both are perfect blackbodies. The sphere is a uniform 100 degC while the water is 20 deg C. Conduction can be assumed to occur over a 1 cm length distance away from the sphere. Neglect any temperature gradients that would be established. Other key parameters for the situation are: Hconv = 100 W/(m2 K) Kcond = 0.6 WI(m K) Stefan-Boltzmann constant 5.67E-8 WI(m2 K4) %3DA 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 bA 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?
- An 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?A rectangular parallelepiped consists of gray, diffuse, and flat surfaces, radiating with each other and nothing else. The surface temperatures are maintained at the specified values. There is a vacuum in the enclosure and thus, no other heat transfer mechanism except radiation exists. Use the given data to find the radiosity and the rate of heat transfer for each surface. Data: Length = 2 m, depth, 3 m, height 1 m, T1 = 100 C, T2 = 200 C, T3 = 250 C, T4 = 400 C, T5 = 500 C, T6 = 550 C, ε1 = 0.5, ε2 = 0.65, ε3 = 0.75, ε4 = 0.8, ε5 = 0.55, ε2 = 0.65, ε3 = 0.85.A spherical vessel with inner diameter of 1m (1.1m outside diameter) contains exothermic reaction that generates heat at a volumetric rate of 57 kW/m3. Assuming that the vessel is exposed in a surrounding at a uniform temperature of 278K, that the vessel radiates uniformly. What is the outer surface temperature of the vessel (Ts)? Note: Consider radiation heat tranfer only and the usrface emmissivity is 0.78. Round your answer to 2 decimal places.