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ENGR5003 / Week 3
Week 3 Q1Exercise sheetCurrent spec2:120 min

ENGR5003 Week 3 workshop sheet Q1

1 kg of saturated water at a pressure of 75 kPa, with a dryness fraction, x=0.25x = 0.25, is placed into a rigid tank. Heat is added to the system until the water becomes a saturated vapour.

Formulas you may need
  • Wet steam: v=(1−x)vf+xvgv = (1 - x)v_f + xv_g, u=(1−x)uf+xugu = (1 - x)u_f + xu_g, h=(1−x)hf+xhgh = (1 - x)h_f + xh_g (on the formula sheet)
  • First law, closed rigid system: Q=ΔU=m(u2−u1)Q = \Delta U = m(u_2 - u_1) (on the formula sheet)
  • Linear interpolation: y−y1y2−y1=x−x1x2−x1\dfrac{y - y_1}{y_2 - y_1} = \dfrac{x - x_1}{x_2 - x_1} (learn this, Lecture 9)
  • Heat capacities: du=cv dTdu = c_v\,dT, dh=cp dTdh = c_p\,dT, γ=cp/cv\gamma = c_p/c_v (on the formula sheet)
  1. (a)
    Determine the volume of the tank.
  2. (b)
    Estimate the temperature and pressure of the saturated vapour.
  3. (c)
    Determine the heat required during this process.
  4. (d)
    Estimate cvc_v and cpc_p as well as the adiabatic index.
    First