Engineering Answers

Continuous cable ADB runs over a small frictionless pulley at D to support beam OABC which is part of an entrance canopy for a building (see figure 3). A downward distributed load with peak intensity q0 = 5 kN/m at O acts on the beam. Assume that canopy weight W = 8 kN and that cable cross-sectional area is 100 mm2 . a) Find cable force T and pin support reactions at O and D b) Find the normal stress in the cable in the cable ADB c) Determine the required diameter of pins A, B, D and O if the pins are in double shear and the allowable shear stress is 80 MPa? Note that OA = AB = BC = 1.5m. 

what is the sequence in the making of Extreme Constructions The Meraviglia Cruise Ship

. A magnetic stirrer agitated vessel is used for absorption of CO2 in water at 298 K and 2

atm pressure. Water is fed at a rate of 1 L/min and the carbonated water leaves the vessel

continuously so that a constant volume is maintained in the contactor. The outlet water

contains 2.3 g CO2/L. The interfacial area of gas-liquid contact is 80 m2

/ m3

; the volume of

gas-liquid dispersion is 8 L. The solubility of CO2 in water can be found using Henry’s law.

At 298 K, the Henry’s law constant for CO2 is 1640 atm/mole fraction and it’s diffusivity in

water is 1.92 x 10-9 m/s. The density of liquid is 997 kg/ m3

. Calculate:

(i) The thickness of the liquid film, if the Film theory is applicable.

(ii) The contact time between the liquid element with the gas if the Penetration theory is

applicable.

(iii) The surface renewal rate if the Surface-renwal theory is applicable. (

For the absorption of dilute gas mixture in a packed column, derive that

y y lm

y y

N

e

toG







1 2

In the Danckwerts model, it is assumed that elements of the surface have an age

distribution ranging from zero to infinity. Obtain the age distribution function for this model

and apply it to obtain the average mass transfer coefficient at the surface, given that from the

penetration theory the mass transfer coefficient for the surface of age θ is

/( ) DAB

. (4)

By what percentage would the rate of absorption be increased or decreased by increasing

the total pressure from 100 to 200 kN/m2

in absorption of ammonia from a mixture of

ammonia and air containing 10% ammonia by volume, using pure water as solvent. Assume

that all the resistance to mass transfer lies within the gas phase. The diffusivity can be

assumed to be inversely proportion to the absolute pressure.

Ammonia is diffusing through a non-diffusing gas mixture of methane and hydrogen in

volume ratio 2:1 under steady state condition. The total pressure is 1 atm. and the temperature

is 100C. The partial pressure of ammonia at two planes 2 mm apart is 13000 and 6500 N/m2

,

respectively. Calculate the flux of ammonia through the layer. Estimate also the quantity of

ammonia diffusing in kg/ day, if the area of cross section of stagnant gas film is 2 m2

.

NH 3 H 2

D  = 7.0 x 10-5 m

2

/ s at 303 K and 1 atm.

NH 3 CH 4

D  = 2.0 x 10-5 m

2

/ s at 288 K and 1.5 atm. (

the following data were recorded during the tensile test of a 14-mm diameter mild steel rod. the gauge length was 50-mm, at fracture the elongation between the gauge was 4-mm and the minimum diameter was 11.3-mm. plot a convectional stress strain curve for mild steel

A roof truss and the detail of the riveted connection at joint B, see Fig. 2. Using allowable stresses

of ߬ = 70 MPa and ߪ ௕ൌ 140 ܯ ,ܽܲhow many 22-mm diameter rivets are required to fasten

members BC and member BE to the gusset plate. What is the largest average tensile or compressive

stress in BC and BE?