Mechanical Engineering Answers

{a }Oil flows in a pipe 100 mm bore diameter with a Reynolds’ Number of 500 .what is the density {b}While solving a problem, a person ended up with the following equation at some stage

: E = 25 kJ + 7 kJ/kg, where E is the total energy and has the unit of kilojoules. Determine how to correct the error and discuss what may have caused it. .

A full journal bearing of 50mm diameter and 100mm long has a bearing pressure of 1.4N/mm2

. The

speed of the journal bearing is 900r.p.m and the ratio of journal diameter to the diametral clearance is

1000. The bearing is lubricated with oil whose absolute viscosity at the operating temperature of 75oC. Find: (a) The amount of artificial cooling required, and (b) The mass of the lubricating oil required, if the

difference between the outlet and inlet temperature of the oil is 10oC. Take specific heat of the oil as

1850J/kg/ oC.

There's total of 18 items shown on the supercheap auto catalogue on page 3.

a. what percentage of the 18 items are discounted at a 40% off or higher rate?(rounded off to 2 decimal places)

b. you have a budget of $100, you are interested in buying a tool bag, a staple gun and the highest possble quality toolPRO spanner set. how much money will you spend and how much will you have left over after purchasing these 3 items?

A centrifugal water pump operates at 30 m3/hr and at 1440 RPM.The pump operating efficiency is 65% and motor efficiency is 89%.The discharge pressure gauge shows 3.4 kg/cm2.The suction is 3mtr below the pump centreline.If the speed of the pump is reduced by 25%, estimate pump flow, head and motor power.Assume motor and pump efficiency remains same at the reduced speed.

A pipe contains a gradually tapering section in which its diameter decreases from 400 mm to 250 mm. The pipe contains an incompressible fluid of density 1000 kgm−3 and runs full. If the flow velocity is 2 ms−1 in the smaller diameter, determine the velocity in the larger diameter, the volume flow rate and the mass flow rate.

Mechanical implications of faraday's law include motors and generators. Briefly explain Newton's law, the basis of mechanical engineering.

A pump is delivering 50m3/hr of water with a discharge pressure of 3.5kg/cm2.The water is drawn from a sump where water level is 5 meter below the pump centre line.The power drawn by the motor is 9.5kw at 90% motor efficiency.Find out the efficiency of the pump.

A heavy cylindrical mass is supported at the end of a close-coiled helical spring and is

located concentrically in a cylinder of oil as shown, with a small annular clearance

between the cylinder wall and mass. The mass has a value of 6 kg. When released

from the spring, the mass is observed to sink to the bottom of the cylinder at a steady

speed of 1.4 m/s. When secured to the spring, the spring is observed to extend 16 mm

when the mass was being immersed in the oil. The system is now caused to vibrate.

Determine the frequency of free response and the ratio of two successive amplitudes.

The specific gravity of the oil is 0.86 and that of the mass is 7.35.

A room A/C in a house operates with R-12 between 1.2368 bar and 13.672 bar. The vapour is dry and saturated at the compressor inlet. Assuming isentropic compression, determine the theoretical C.O.P of the plant is 80% of the theoretical, calculate the power required to run the compressor to obtain a refrigerating capacity of 1 TR. If the liquid is sub-cooled through 10oC after condensation, calculate the power required. The properties of R-12 are given below: Saturation Temperature oC Enthalpy, kJ/kg Entropy, kJ/kgK Saaturation pressure (bar) Liquid Vapour Liquid Vapour 1.2368 13.672 -25 13.33 176.48 0.0552 0.7126 55 90.28 207.95 0.3197 0.6774



Temperature (oC) Pressure(bar) Enthalpy(kJ/kg) Entropy(kJ/kgK) 64.86 13.672 220.6 0.7126 Assume specific heat of liquid to be 1.055 kJ/kgK

In a 15 TR ammonia refrigeration plant for cooling a large warehouse, the condensing temperature is 25oC and evaporating temperature -10oC. The refrigerant ammonia is sub-cooled by 5oC before passing through the throttle valve. The vapour leaving the evaporator is 0.97 dry. Find: 1. Coefficient of performance 2. Power required Saturation Temperature oC Enthalpy, kJ/kg Entropy, kJ/kgK Specific Heat, kJ/kgK Liquid Vapour Liquid Vapour Liquid Vapour 25 298.9 1465.84 1.1242 5.0391 4.6 2.8 -10 135.37 1433.05 0.5443 5.4770 - -