Revisica
Sign in
ENGR5003 / Week 2
Lecture 6 worked example 2 - isothermal discharge of a heated tankTutorialCurrent spec2:28 min

ENGR5003 Lecture 6 worked example 2 (slides 13-15)

Air is discharged from a tank of volume 2 m32\ \mathrm{m^3} until the pressure drops from 5 bar to 2 bar. The air in the tank is maintained at a constant temperature of 52 ∘C52\ ^\circ\mathrm{C} by an electrical heating element in the tank. Determine the electrical heat input during this process. Take Rg=0.287 kJ/(kg K)R_g = 0.287\ \mathrm{kJ/(kg\,K)}.

Formulas you may need
  • Ideal gas: pV=mRgTpV = mR_gT (on the formula sheet)
  • Unsteady flow energy equation: ΔU=hinΔmin−houtΔmout+ΔQ−ΔW\Delta U = h_{in}\Delta m_{in} - h_{out}\Delta m_{out} + \Delta Q - \Delta W (KE, PE neglected) (on the formula sheet)
  • Ideal gas: u=cvTu = c_vT, h=cpTh = c_pT, cp−cv=Rgc_p - c_v = R_g (on the formula sheet)
  1. (a)
    Find the initial and final mass of air in the tank and the mass discharged.
  2. (b)
    Determine the electrical heat input.