Winter 1982 (Final)

Water at 20C is to be pumped through 30 metres of nominal 8 cm pipe (internal diameter 7.793cm) into an overhead reservoir. The volumetric flow rate of the liquid is 4 L / min.

  (a) Is the flow laminar or turbulent? (Provide calculations to confirm your answer.)

  (b) Calculate the pressure (kPa) required at the outlet to the pump in order to supply water to the overhead reservoir at a rate of 4 litres/minute.

  (c) Calculate the power (kW) rating for the pump.

Additional Data: At 20C, the density and viscosity of water may be taken as 998.2 kg/ and 1.002 mPa s respectively.

 

3. Explain why, for a gas, the specific heat at constant volume has a different value 
from the specific heat at constant pressure.
An ideal gas is contained in a cylinder fitted with a piston. Initially the temperature of the 
gas is 15℃. If the mass of the gas is 0.035 kg, calculate the quantity of heat energy 
required to raise the temperature of the gas to 150 ℃ when:
(a) The piston is fixed;
(b) The piston moves and the pressure is constant.
For the gas, 𝑐𝑣 = 676 J/kg-K and 𝑐𝑝 = 925 J/kg-K.

Explain gas turbines? 

1. A piston–cylinder device contains 5 kg of water at 800kPa and 70°C. The water is now cool at constant pressure until it exists as a liquid at 15°C. Determine the amount of heat loss and show the process on a T-v diagram with respect to saturation lines.

How do I determine the heat loss?