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ENGR5003 / Week 1
Week 1 Q2Exercise sheetCurrent specThird6 min

ENGR5003 Week 1 workshop sheet Q2

Consider an ideal gas undergoing an isothermal process from V1=1 m3V_1 = 1\ \mathrm{m^3} to V2=5 m3V_2 = 5\ \mathrm{m^3} and T=400 KT = 400\ \mathrm{K}. Assume that Rg=0.287 kJ/kg/KR_g = 0.287\ \mathrm{kJ/kg/K}.

Formulas you may need
  • Isothermal ideal gas work: w=RgTln⁡V2V1w = R_gT\ln\dfrac{V_2}{V_1} (on the formula sheet, written as W=−mRgTln⁡(V2/V1)W = -mR_gT\ln(V_2/V_1) for work done on the gas)
  • Ideal gas entropy change: s2−s1=cvln⁡T2T1+Rgln⁡v2v1s_2 - s_1 = c_v\ln\dfrac{T_2}{T_1} + R_g\ln\dfrac{v_2}{v_1} (on the formula sheet)
  • Isothermal ideal gas: ΔU=0\Delta U = 0 so Q=WQ = W (on the formula sheet)
  1. (a)
    Determine the specific work output during this process.
  2. (b)
    What is the change of specific entropy of this process?