Q1: At a constant velocity of 20 m/s, air passes across a flat plate with ambient pressureand temperature of 20 kPa and 20°C. At a distance of 7.5 cm from the leading edge, theplate is heated to a constant temperature of 75°C. How much heat is transferred overallfrom the leading edge to a location 35 cm from the leading edge?TwQ2: The critical Reynolds number for flow over a flat plate in a particular application is10°. This critical Reynolds number and an isothermal plate temperature of 400 K areencountered by air flowing across it at 1 atm, 300 K, and 10 m/s. At the end of the plate,the Reynolds number is 5 x 106. What will average heat transfer coefficient be for thissystem? What is the length of the plate? What is the plate's loss of heat?Re21WatQ3: At 50 kPa and 300 K, air moves at an average velocity of 6 m/s across a 20-cm-ThooPsquare plate. To provide a steady flow of heat, an electrical heater is mounted within theplate. If the plate temperature is limited to 600 K, how much heat can be dissipated2overall?Tw

Step 1:Solution(1):Given:Velocity, V = 20 m/sAmbient pressure, P∞ = 20 kPaAmbient temperature, T∞ =…

Answered: Q1: At a constant velocity of 20 m/s,…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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A 4.5 in (inside diameter), 4.9 in (outside diameter) tube carries dry saturated steam at 10 bar. Assume that the interior temperature of the tube is the same as that of the steam. The outside air temperature is 25°C. For ksteel = 51.9 W/(m K) and hair = 13.0 W/(m2K). a) How much energy is lost, in kWh, in a 20 m long section of pipe during an 8-hours
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An oil preheater consists of a single tube of 10 mm diameter and 30 m length. The first half of the tube is heated by a heat rate per unit length of q' = ax2 [W/m], where a = 5 W/m³, and the second half is well insulated. Before entering the tube, the oil has a uniform temperature of 25 °C and a flow rate of 0.0125 kg/s. The hydrodynamic boundary layer has been fully developed. (a) Determine the type of flow (laminar or turbulent) inside the tube. (b) Determine the location where the thermal boundary layer is fully developed. (c) Calculate the mean fluid temperature at the tube exit, Tmo. Properties of the oil: p = 865.8 kg/m³ = 2035 J/kg K, u = 8.36×102 N⚫s/m², k = 0.141 W/mK, a=0.8×107 m²/s, and Pr-1206.6.
A circuit board is cooled by passing cool helium gaş "C,= 5193 J/kg.C, v =1.233×10 m /s, p= 0.1635 kg/m Pr = 0.669, k = 0.1565 W/m.°C " through a channel [0.46 cm x14 cm×20 cm ] drilled into the board. Helium enters at 15°C and 6.8 m/s and leaves at 63.7 °C. The heat flux at the top surface of the channel can be considered to be uniform, and heat transfer through other surfaces is negligible. Assume fully developed flow for the whole channel length and (if flow is NOT Laminar use Dittus-Boelter equation:Nu=0.023 Re Pr) What is the maximum surface temperature on the circuit board (°C)? Electronic components, T, °C Не 15°C L=20 cm Channel
An oil preheater consists of a single tube of 10 mm diameter and 25 m length. The tube is heated by a heat rate per unit length of q' = ax2 [W/m], where a = 1.2 W/m³. Before entering the tube, the oil has a uniform temperature of 25 °C and a flow rate of 0.025 kg/s. The hydrodynamic boundary layer has been fully developed. (a) Determine the type of flow (laminar) or turbulent) inside the tube. Is it fully developed? (b) Calculate the mean fluid temperature and the surface temperature at the tube exit. Note: When determining the convection coefficient, use the correlation equation for constant heat flux. Properties of the oil: p = 865.8 kg/m³, cp=2035 J/kg K, μ= 8.36×102 N⚫s/m², k = 0.141 W/m K, and a = 0.8×107 m²/s. knowns: q' = ax² L: 25m D= 0.01m m = 0.025 kg/s Tm,i=25 C 0 x (Tm.o assumptions qwns! Steady flow
Over what range of temperature (in Kelvin) do you think it is reasonable to assume that the specific heat of air at constant pressure is constant for purposes of calculations in fluid mechanics? Justify your answer
Q1: Air enters a 7m long section of a rectangular duct of cross section 15 cm x 20 cm at 50°C at an average velocity of 7 m/s. If the walls of the duct are maintained at 10 C, determine (a) the outlet temperature of the air, (b) the rate of heat transfer from the air. Air properties from tables: p=1.127 kg/m' C,-1007 J/kg. C k 0.02662 W/m.°C Pr 0.7255 D=1.702x10 m'/s Answer: (a): Te 34.2 °C, (b): Q' 3776 W Hint: 1- Use the Logarithmic mean temperature difference relations. If Reer 2300, in pipes and ducts, the flow is turbulent. T-10°C Air duet 15 em x 20 em Air 50°C 7 m/s L-7m
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31. A uniformly heated square plate of 2 ft × 2 ft is exposed to cold air at 80 F. The heater output remains at a constant value of 1 kW. Air, at atmospheric pres- sure, flows over the plate at a velocity of 16.5 ft/s. Find the average temperature of this plate. [Ans.: - 513 F].
Forced air at T∞ = 25°C and V = 12 m/s is used to cool electronic elements on a circuit board. One such element is a chip, 4 mm × 4 mm, located 153 mm from the leading edge of the board. Experiments have revealed that flow over the board is disturbed by the elements and that convection heat transfer is correlated by an expression of the form Nu_x=0.04Re_x^{0.85}\Pr^{\frac{1}{3}}Nux=0.04Rex0.85Pr31 Estimate the surface temperature of the chip if it is dissipating 32 mW.

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