Mechanical Engineering Answers

One stage of a cascade impactor designed to operate at 1.0 ft/min at standard conditions has a cutoff diameter of 5 um. What will be the cutoff diameter for this stage if it is operated at 300°F, but flow is measured at 1.0 ft/min after the gas has cooled to standard conditions? 

A total of 10 rectangular aluminum fins (k = 203 W/m·K) are placed on the outside flat surface of an electronic device. Each fin is 100 mm wide, 20 mm high and 4 mm thick. The fins are located parallel to each other at a center-to-center distance of 8 mm. The temperature at the outside surface of the electronic device is 60°C. The air is at 20°C, and the heat transfer coefficient is 100 W/m2 ·K. Determine (a) the rate of heat loss from the electronic device to the surrounding air and (b) the fin effectiveness.

Can a full detailed description be given on how a aluminium frying pan is made through casting?

QUESTION 3 [ 17 Marks]

(a) Give the different types of loading and supports on a beam.

[7]

(b) State the assumptions made in the theory of pure bending.

[3]

(c) In a civil engineering construction site, a rectangular support beam 100 mm wide and

250 mm deep is exposed to a maximum shear force of 50kN. You are required to

calculate:

(i)

Average shear stress,

(ii)

Maximum shear stress,

(iii)

Shear stress at 25 mm above the neutral axis

QUESTION 2 [14 Marks]

In a metal workshop a technician is tasked with making calculations on metal strength

properties. The technician is given two rectangular plates, one of steel and the other of brass

each 40 mm wide and 10 mm deep and these are placed together to form a beam 40 mm wide

and 20 mm deep, on two supports 1 m apart, the brass plate being on top of the steel plate. You

are required to calculate the maximum load which can be applied at the centre of the beam

given that the plates are either

(a) Separate and bend independently,

[6]

(b) Firmly secured throughout their length.

[8]

Given: The maximum allowable stress in steel= 112.5 N/mm2

and in brass = 75 N/mm2

.

Take Es = 2 X 105 N/mm2

and Eb = 8 X 104 N/mm2.

Compute the drying power Ea and the relative evaporation Er of an area covered with grass of Z. = 2 cm, and that of an adjacent area covered with trees of Z, = 70cm. Given that wind velocity U = 2.5 m/sec, Tair = 8°C, relative humidity = 0.3, Pair = 1.3 kg/m”, pw = 1000 kg/m”, Patm = 1013mb, Z = 2m, and net radiation Q = 90 W/m². Why the Ed of trees is higher than that of grass?

Complex poles and zeros. Sketch the root locus with respect to K for the equation 1 + KL(s) = 0 and the listed choices for L(s). Be sure to give the asymptotes and the arrival and departure angles at any complex zero or pole. After completing each hand sketch, verify your results using Matlab. Turn in your hand sketches and the Matlab results on the same scales

A slightly compressible oil is flowing in a volumetric, homogeneous reservoir. The oil has a viscosity of 2 cp, compressibility of 5 x 10-5psi -1 and formation volume factor of 1 RB/STB. The reservoir is represented by a three-gridblock system as shown: T The dimensions and the properties of all gridblocks are Ax=200 ft, Ay=100 ft, Az=20 ft, kx= 100 mD, and p=0.20. The initial reservoir pressure is 3,000 psia. The well in gridblock 3 is produced so that the well block pressure is maintained at 1,500 psia for all time >0. All the boundaries are closed. Find the pressure of gridblocks 1 and 2 at t=10 days with the implicit finite difference formulation and the time step At=10 days.