Mechanical Engineering Answers

A spherical tank for storing liquid oxygen on the space shuttle is to be made from stainless steel of 0.8m outer diameter and 5mm wall thickness. The boiling point and latent heat of vaporization of liquid oxygen are 90K and 213kJ/kg respectively. The tank is to be installed in a large compartment whose temperature is to be maintained at 240K. A coating of insulation will cover the tank. Thermal conductivity of the tank and insulation are 9.2W/m-K and 0.000017W/m-K. Assuming the inside surface of the tank to be at 90K and the outside surface temperature of the insulation to be at 240K, determine the thickness of the insulation required to maintain oxygen loss due to boiling below 1kg/day.

A bakelite coating is to be used with a 10mm diameter conducting rod whose surface is maintained at 200C by passage of an electrical current. The rod is in a fluid at 25C and the convection coefficient is 140W/m2-K. Considering a coating used with thickness corresponding to the critical radius, determine the rate of heat transfer per meter of the rod (watts) 

A bakelite coating is to be used with a 10mm diameter conducting rod whose surface is maintained at 200C by passage of an electrical current. The rod is in a fluid at 25C and the convection coefficient is 140W/m2-K. What is the critical radius associated with the coating? (millimeters) *

A 2mm diameter electrical wire is insulated by a 2mm thick rubberized sheath (k=0.13W/m-K). The convection heat transfer coefficient at the outer surface of the sheath is 10W/m2-K and the temperature of the ambient air is 20C. What is the critical diameter of the insulation? (meters)

A 2mm diameter electrical wire is insulated by a 2mm thick rubberized sheath (k=0.13W/m-K). The convection heat transfer coefficient at the outer surface of the sheath is 10W/m2-K and the temperature of the ambient air is 20C. If the temperature of the insulation may not exceed 50C, what is the maximum allowable power that may be dissipated per meter length of the conductor (watts) 

While a Vessel was at anchor an accident occurred when an Engine Rating was working alone in

the engine room on a single ladder. The top rung of a ladder had been placed against a vertical

corner of some trunking. The ladder was fitted with a rubber feet. The ladder slipped or the

Engine rating lost his balance. The Engine rating fell about two meters into the deck plates. After

the accident, the rubber feet were found to have oil on them.

Guide Questions?

1. What is/are the problem/s?

2. What are the facts bearing on the problems/s?

3. Why did the situation happen?

4. How can the problem/s be addressed?

5. What are your recommendations?

A tank of cross-sectional area A is filled with a liquid of specific weight γ1 as shown in Image (A). Show

that when a cylinder of specific weight γ2 and volume V is floated in the liquid as shown in Image (B), the

liquid level rises by an amount Δh = (

γ2

γ1

)( V

A

)

a vessel of volume 0,03m³ contains dry saturated steam at 17 bar. Calculate the mass of steam in the vessel and the enthalpy of this mass

Design a rigid coupling is used to connect a 45 kW,1440 rpm electric motor to a 

centrifugalpump. The starting torque of the motor is225% of the rated torque

Design a bushed pin type flexible coupling is usedto connect two shafts and transmit 5 

kWpower at 720 rpm Shafts, keys and pins aremade of commercial steel (Syt = Syc = 240 

N/mm2

) and the factor of safety is 3. The flanges are made of grey cast iron FG 200(Sut= 

200 N/mm2

) and the factor of safety is6. Assume,Sys = 0.5Syt and Sus = 0.5Sut.