Engineering Answers

Tom Jackson is buying a new car. Alternative A is an American-built compact. It has an initial cost of

$8900 and operating costs of 9cents /km, excluding depreciation. From resale statistics, Tom estimates

the American car can be resold at the end of 3 years for $1700.Alternative B is a foreign-built Fiasco.

Its initial cost is $8000, the operating cost, also excluding depreciation, is 8 cents /km. How low could

the resale value of the Fiasco be to provide equally economical transportation? Assume Tom will drive

12,000 km/year and considers 8% as an appropriate interest rate.

A road between Fairbanks and Nome, Alaska, will have a most likely construction cost of $4 million per

mile. Doubling this cost is considered to have a probability of 30%, and cutting it by 25% is considered

to have a probability of 10%. The state’s interest rate is 8%, and the road should last 40 years. What is

the probability distribution of the equivalent annual construction cost per mile?

A factory building is located in an area subject to occasional flooding by a nearby river. You have been

brought in as a consultant to determine whether flood proofing of the building is economically justified.

The alternatives are as follows:

A. Do nothing. Damage in a moderate flood is $10,000 and in a severe flood, $25,000.

B. Alter the factory building at a cost of $15,000 to withstand moderate flooding without damage

and to withstand severe flooding with $10,000 damages.

C. Alter the factory building at a cost of $20,000 to withstand a severe flood without damage.

In any year the probability of flooding is as follows: 0.70, no flooding of the river; 0.20, moderate flooding;

and 0.10, severe flooding. If interest is 15% and a 15-year analysis period is used, what do you

recommend?

A furnace wall consists of 250mm fire brick, 125mm thick insulating brick and 250mm thick building brick. The inside wall is at a temperature 600 degrees Celcius and atmospheric temperature is 20 degrees Celsius. The heat transfer coefficient for outside surface is 10 w/m^2k and thermal conductivity of fire brick, insulating brick and building brick are 1.4, 0.2 and 0.7 w/mk respectively. Neglecting radiation calculate the rate of heat loss per unit surface area, the temperature at each interface through the wall and temperature at the outside surface of the wall.

A steam main of 150mm outside diameter containing wet steam at 28bar is insulted with an inner layer of diatomaceous earth, 40mm thick and an outer layer of 85% magnesium 25mm thick. The inside surface of the pipe is at the steam temperature and heat transfer coefficient for the outside surface of the lagging is 17w/m^2k. The thermal conductivities of diatomaceous earth and 85% magnesium are 0.09 and 0.06 w/mk respectively.

Neglecting radiation and thermal resistance of the pipped wall calculate : the rate of heat loss per unit length of the pipe and temperature of the outside surface of the lagging when room temperature is 20 degrees celcius

1. convert milli-meters to multi range volt, current and resistance instruments

2. explain the construction and principle of operation of the oscilloscope

3. Describe the procedure to follow as regard new and /or addition to an electrical installation system

(a) Explain various process of Carnot cycle with the help of P-V and T-S diagrams and mention various assumptions made in the analysis of Carnot cycle.

(b) The following details refers to a four stroke engine:

Cylinder diameter = 220 mm

Length of stroke = 330 mm

Speed = 5 rev/second

Effective brake load = 500 N

Mean circumstances of the brake drum = 4·5 m

IMEP = 5·6 bar

Calculate

(a) Indicated power, (b) Brake power and (c) Mechanical efficiency.

What are different methods adopted in cooling of an I.C engine. Explain in details.

(a) A Diesel engine has a bore of 200 mm and stroke of 320 mm. Cut – off takes place at 9% of stroke. Find the air – standard efficiency if clearance volume is 0.000593 m³.

(b) An engine working on Otto cycle has a compression ratio of 6. Find the air – standard efficiency of the cycle.

A water manometer shows a pressure, in a vessel of 400mm below atmospheric pressure. If the atmospheric pressure is measured as 763 mm Hg. Determine absolute pressure in the vessel in kN/m²