A thin, horizontal metal plate is maintained at a temperature of 400°C. The plate is surrounded (above and below) by still atmospheric air at 30°C. If the plate is square and measures 1.0 m on a side, calculate the total convective heat transfer from the plate.
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- A 2.5-m-tall steel cylinder has a cross-sectional area of 1.5 m2. At the bottom, with a height of 0.5 m, is liquid water, on top of which is a 1-m high layer of gasoline, relative density of 0.8. The gasoline surface is exposed to atmospheric air at 101 kPa. What is the gage pressure at the liquid interface? what is the answer? a.0.077 atm b.15.839 psi c. 1.139 mmHg d.108.848 kPaH.W. Q1: Consider a hot automotive engine, which can be approximated as 0.40m wide, and 0.8m long rectangular block. The bottom surface of the block is at a temperature of 80°C and has an emissivity of 0.95. The ambient air is at 20°C, and the road surface is at 25°C. Determine the rate of heat transfer from the bottom surface of the engine block by convection and radiation as the car travels at a velocity of 80 km/h. Assume, the flow to be turbulent over the entire surface because of the constant agitation of the engine block. k = 0.02735 W/m.°C v=1.798×10* m²/s Air properties at Tf= 50 °C: Pr = 0.7228 Answer: Qcony = 1363 W, Qrad = 132 W, Qotal = 1495 w Hint: Use the correlations (equations) of average Reynold number (ReL). L = 0.8 m Engine block Air V, = 80 km/h T. = 20°C T; = 80°C ɛ = 0.95A horizontal copper plate 10 cm thick is initially uniform in temperature at 250◦C.The bottom surface of the plate is insulated. The top surface is suddenly exposed toa fluid stream at 80◦C. After 6 min the surface temperature has dropped to 150◦C.Calculate the convection heat-transfer coefficient that causes this drop.
- Ans. 0.9 m Q2/A vertical cylinder having a length of 30 cm is maintained at 100-C and exposed to room air at 15-C. Calculate the minimum diameter the cylinder can have in order to behave as a vertical flat plate. Ans. 9.01 cmThank you for answering this question. Please you specify each step as soon as possible. Good Luck! Thank you. If you want to cool a thin plate by natural convection quickly, will you hold it as shown in position (a) with the long dimension parallel to the direction of gravity or in position (b) with the shorter dimension parallel to the direction of gravity and why? Assume Laminar flow. (b)A 25-cm circular grill has an emissivity of 0.9. The temperature of the air and surrounding surfaces is 24°C, while the surface temperature of the grill is maintained constant at 130°C. To compute for the Nusselt number of the air flow, what is the exact value of the temperature in °C on which the air properties should be based?
- A circular plate of diameter (1.36 m) is placed some how 1.5 meter above the room floor, if the Raleigh number approximated by Ra=7.653E7*D° and temperature difference between surface and room air temperature is 73 C, air properties: k = 0.0372 W/m.K, Pr = 0.686 . What is the initial rate of cooling by convection from the Upper surface ONLY (Watts)? be can Select one: A. 1004.31 B. 1387.95 C. 1134.87 D. 1263.42 E. 368.99Describe, in terms of density changes, heat convection in fluids. When a fluid is heated at the base, it will expand, become less dense and rise. The cooler fluid at the top being denser, will sink. This continuous, cyclic movement of the fluid known as convection current will eventually heat up the entire whole fluid evenlyA heated plate, 20 by 20 cm, is inclined at an angle of 60°with the horizontal and placed in water. Approximately constant-heat-flux conditions prevail with a mean plate temperature of 40°C and the heated surface facing downward. The water temperature is 20°C. Calculate the heat lost by the plate.
- Using the equations for the Barometric Law and temperature decrease from adiabatic expansion (found in the lecture, calculate the atmospheric temperature at 5 km. Assume dry air, i.e. gamma equal to 1.4, temperature at the surface is 288 K. Group of answer choices These laws cannot predict the temperature at 5 km. 288 K 148 K 243 KWhat must be the Height of a 200mm diameter vertical pipe carrying hot liquid so that the surrounding area becomes 38 °C? Note that the rate of convection is 6 KWatts and the surface of the plate is around 90°C. provide an answer in meters7. Air at 600 K, 1 atm is flowing across a flat plate kept at 300 K with a convection coefficient of 91 W/m2 K. If the Stanton number at this condition of flow is 0.039. what is the velocity of the air? Express your answer in m/s.