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The elemental unit of an air heater consists of a long circular rod of diameter D, which is encapsulated by a finned sleeve and in which thermal energy is generated by Ohmic heating. The N fins of thickness t and length L are integrally fabricated with the square sleeve of width w. Under steady-state operating conditions the rate of thermal energy generation corresponds to the rate of heat transfer to air flow over the sleeve.
(a) Under conditions for which a uniform surface temperature T, is maintained around the circumference of the heater and the temperature Too and convection coefficient h of the air flow are known obtain an expression for the rate of heat transfer per unit length to the air. Evaluate the heat rate for T1 = 300°C, D = 20 mm, an aluminum sleeve (k = 240 W/m · K), w = 40 mm, N = 16. t = 4 mm. L = 20 mm, T8 = 50°C, and h = 500 W/m2 · K.
(b) For the foregoing heat rate and a copper heater of thermal conductivity k h = 400 W/m · K, what is the required volumetric heat generation within the heater and its corresponding centerline temperature? (c) With all other quantities unchanged, explore the effect of variations in the fin parameters (N, L, t) on the heat rate, subject to the constraint that the fin thickness and the spacing between fins cannot be less than 2 mm.
In a long cilindric wire with a radius of 2 cm, a corrent with 80A goes thorugh it. What is the magnetic energy per unit of wire lenght?
A balanced 3-phase 3-wire system has a line voltage of 500Vrms. Two balanced Y-connected sources are present. One is acapacitive load with 7-2j Ω per phase, and the other is aninductive load with 4+2j Ω per phase.
A shunt-connected a DC motor has zero rotational losses and R A = 0. Assume that R A and R adj is constant [except in part (d)] and that is directly proportion to feild current. For VT= 200 V and P out = 2 hp.
Apply Coulomb's law to obtain an expression for the electric field at any point P (r, 0) on the x-y plane. Show that your result reduces to the expression given by Eq. (4.33) as the length L is extended to infinity.
he input tothe receiver is a modulated wave of 0.3W average power and Gaussian noise of one-sided power spectral density of 10-8W/Hz. 1.if the detector is an envelope detector and the modulatedwave is A(1+0.8cos1000t)cos(6.28x1000000t),
An AISI 4140 OQT 1000 sleeve is to be secured to a 2.50-inch diameter solid rod ot the same material employing a class FN1 force fit. The outside diameter of the sleeve is 5.00 inches.
A shunt motor with an armature resistance of 0.15ohms is running 1200rpm for a load which requires an armature current of 50A from 230V source. At no load, the armature current of 5A.
The electrostatic potential in space is given by the scalar field V(r)=V(x,y,z)=e^y + (3x)^2-4cos(z) Find the potential difference between the points P(1,1,1) and Q(0,0,0).
1- Write a function that shows you how to calculate F(x) = 0.1X^2+5Y^3 2- Read and write a File that has a set of 10 numbers. Then assign those numbers to an array.
Why is power normally sent in bulk
A radio receiver has antenna noise temperature of 3000 K and equivalent noise temperature of 7000 K for its feeder and amplifier cascade. It requires Eb/No = 15 dB to provide Probability of error of 10^-15 (using BPSK).
Determine the probability that the receiver correctly receives the codeword for the first time on the k-th transmission. Also determine the average number of transmissions until the receiver correctly receives the codeword.
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