Govt Exams
u = u_f + x × u_fg, so x = (u - u_f)/u_fg = (2400 - 1317.3)/1753.7 = 1082.7/1753.7 ≈ 0.62
The second law states that entropy of an isolated system must increase or remain constant (reversible). A decrease in total entropy violates the second law and is impossible.
T_2/T_1 = (P_2/P_1)^((γ-1)/γ) = 8^(0.4/1.4) = 8^0.2857 ≈ 1.734. T_2 = 300 × 1.734 ≈ 520.2 K
A reversible adiabatic process has constant entropy (dS = 0), making it isentropic. This is a key assumption in many thermodynamic analysis for ideal processes.
The Mayer relation: C_p - C_v = R, where R is the specific gas constant. This relation holds for all ideal gases.
In an ideal Rankine cycle, turbine expansion is isentropic (reversible and adiabatic), maximizing work output. Real turbines follow this closely but with some irreversibilities.
Q = m × L_fg = 0.5 kg × 1941 kJ/kg = 970.5 kJ heat is removed during condensation
The correct form is dU = δQ - δW, where δW = PdV for expansion work. This represents energy conservation in thermodynamic systems.
Diesel cycle efficiency = 1 - (1/r^(γ-1)) × [(r_c^γ - 1)/(γ(r_c - 1))] where r_c = cutoff ratio. With r=16, r_c=1.5, γ=1.4, efficiency ≈ 63.5%
Maximum efficiency is Carnot efficiency = 1 - (T_cold/T_hot) = 1 - (300/500) = 0.4 = 40%