Molecular Physics | Thermodynamics Answers

Two steel rings of radial thickness 30 mm, common radius 70 mm and length 40 mm are 

shrunk together to form a compound ring. It is found that the axial force required to separate 

the rings, i.e. to push the inside ring out, is 150 kN. Determine the shrinkage pressure at the 

mating surfaces and the shrinkage allowance. E = 208 GN/mZ. The coefficient of friction 

between the junction surfaces of the two rings is 0.15. 

Dry saturated steam at 100 bar expands isothermally and reversibly to a

pressure of 10 bar. Calculate per kg of steam :

(i) The heat supplied ;

(ii) The work done

. Air at a temperature of 20°C passes through a heat exchanger at a

velocity of 40 m/s where its temperature is raised to 820°C. It then enters a turbine with same

velocity of 40 m/s and expands till the temperature falls to 620°C. On leaving the turbine, the air

is taken at a velocity of 55 m/s to a nozzle where it expands until the temperature has fallen to

510°C. If the air flow rate is 2.5 kg/s, calculate :

(i) Rate of heat transfer to the air in the heat exchanger ;

(ii) The power output from the turbine assuming no heat loss ;

(iii) The velocity at exit from the nozzle, assuming no heat loss.

Take the enthalpy of air as h = cpt, where cp is the specific heat equal to 1.005 kJ/kg°C and

t th

9. During flight, the air speed of a turbojet engine is 250 m/s. Ambient air

temperature is – 14°C. Gas temperature at outlet of nozzle is 610°C. Corresponding enthalpy

values for air and gas are respectively 250 and 900 kJ/kg. Fuel air ratio is 0.0180. Chemical

energy of fuel is 45 MJ/kg. Owing to incomplete combustion 6% of chemical energy is not released

in the reaction. Heat loss from the engine is 21 kJ/kg of air.

Calculate the velocity of the exhaust jet.

 In an air compressor air flows steadily at the rate of 0.5 kg/s through an

air compressor. It enters the compressor at 6 m/s with a pressure of 1 bar and a specific volume

of 0.85 m3/kg and leaves at 5 m/s with a pressure of 7 bar and a specific volume of 0.16 m3/kg. The

internal energy of the air leaving is 90 kJ/kg greater than that of the air entering. Cooling water

in a jacket surrounding the cylinder absorbs heat from the air at the rate of 60 kJ/s. Calculate :

(i) The power required to drive the compressor ;

(ii) The inlet and output pipe cross-sectional areas

A 2.2-cm-outer-diameter pipe is to span across a river at a 30-m-wide sec￾tion while being completely immersed in water (). The average

flow velocity of water is 4 m/s and the water temperature is 158C. Determine

the drag force exerted on the pipe by the river.

7. In an air compressor air flows steadily at the rate of 0.5 kg/s through an

air compressor. It enters the compressor at 6 m/s with a pressure of 1 bar and a specific volume

of 0.85 m3/kg and leaves at 5 m/s with a pressure of 7 bar and a specific volume of 0.16 m3/kg. The

internal energy of the air leaving is 90 kJ/kg greater than that of the air entering. Cooling water

in a jacket surrounding the cylinder absorbs heat from the air at the rate of 60 kJ/s. Calculate :

(i) The power required to drive the compressor ;

(ii) The inlet and output pipe cross-sectional areas

The specific heat capacity of ethanol is 2440J/kg °C. How many joules of energy will be required to heat 150g ethanol to 35°C if the starting temperature is 22°C?

Solve the density of a 2-liter coke. Use local g=31.9 fps². Explain your solution

Solve for your own mass. Assume local g=9.8 mps² . Explain your solution.