A manufacturing process calls for heating long copper rods, which are coated with a thin film having
(a) What is the initial rate of change of the rod temperature!
(b) How long must the rods remain in the oven to achieve a temperature of 1000 K?
(c) The heating process may be accelerated by routing combustion gases, also at 1650 K, through the oven. For convection coefficients of 10, 100, and
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Fundamentals of Heat and Mass Transfer
- 9.3 A 5 cm? thin film solar cell has a reverse saturation or dark current 1, = 5.9 x 10-15 mA. Under the insolation Ia of 900 W/m?, the short-circuit current Ie is 124 mA. At the cell temperature of 25°C, V,= kT/q = 0.026 V. Determine: (i) open-circuit voltage Voc, (ii) MPP voltage Vm and current Im, (iii) maximum power output Pm, (iv) fill factor FF of cell I–V characteris- tics, and (v) cell efficiency n..arrow_forward7: horizontal steel pipe having a diameter of 5 cm is maintained at a temperature of 50◦C in a large room where the air and wall temperature are at 20◦C. The surface emissivity of the steel may be taken as 0.8. Using the data of Table 1-3, calculate the total heat lost by the pipe per unit length.arrow_forwardThe Diamond Ring Solution. The processing chip on the computer that controls the navigation equipment on your spacecraft is overheating. Unless you fix the problem, the chip will be damaged and the navigation system will shut down. You open the panel and find that the small copper disk that was supposed to bridge the gap between the smooth top of the chip and the cooling plate is missing, leaving a 2.0 mm gap between them. In this configuration, the heat cannot escape the chip at the required rate. You notice by the thin smudge of thermal grease (a highly thermally conductive material used to promote good thermal contact between surfaces) that the missing copper disk was 2.0 mm thick and had a diameter of 1.0 cm. You know that the chip is designed to run below 70 °C, and the copper cooling plate is held at a constant 5.0 °C. (a) What was the rate of heat flow from the chip to the copper plate when the original copper disk was in place and the chip was at its maximum operating…arrow_forward
- Spacecraft must be cooled via radiative mechanisms, and one means of doing this is by using radiation fins. In many instances, these fins are heated rods that protrude from the spacecraft. Assume that the rod is of length, L; cross-sectional are, Ac; and perimeter, Pā. Its base temperature is T, and the rod has thermal conductivity and emissivity, λ and ɛ, respectively. Set up the differential equation describing the temperature profile within the rod assuming that space is a blackbody at Ts.arrow_forwardPlease solve the question on the sheet and get a clear picture and submit the picture. thankyou.arrow_forward2 inch OD during a visit to a plastic sheet factory 60 m long section of a horizontal steam pipe passes from one end to the other without insulation is observed. While the temperature of the ambient air and its surfaces is 20 °C, the temperature measurements at several points are the average of the exposed surfaces of the steam pipe. indicates that the temperature is 160 °C. It is seen that the outer surface of the pipe is oxidized and The emissivity can be taken as 0.59. According to this; a) Calculate the heat loss in the steam pipe. b) The steam used is produced in a gas furnace operating with an efficiency of 59%. Factory 105500 It pays $1.10 per kJ of natural gas. If it is assumed that the factory works all year (365 days), for this facility Calculate the annual cost of heat losses in the steam pipe.arrow_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. Specifically need help with part barrow_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. can you solve part b please?arrow_forward3. An electric immersion heater, 10 mm in diameter and 300 mm long, is rated at 550 W. The emissivity of the heater is ε = 0.85. a) If the heater is horizontally positioned in a large tank of water at 20°C, estimate its surface temperature. b) If the heater is accidentally operated in air at 20°C, estimate the surface temperature. Hint: Radiation heat transfer can be neglected in liquids, but not in gases like air.arrow_forward
- Explain in your own words: (a) In what way is the heat transfer through a large steel plate that has its surfaces at specific temperatures? (B) What are the patterns in which the temperature at one surface of the steel plate is not specified, but the surface is exposed to a fluid at a specified temperature?arrow_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_forwardPROBLEM 4: A black thermocouple is inside a chamber with black walls. If the air around the thermocouple is at 20°C, the walls are at 100-C, and the heat transfer coefficient between the thermocouple and the air is 75 W/m²K, what temperature will the thermocouple read?arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning