Referring to Fig. 4.12, if I throttle hydrogen gas from an initial (P_i, T_i) =

Question

Referring to Fig. 4.12, if I throttle hydrogen gas from an initial (P_i, T_i) = (50 bar, 50 K) down to a final pressure P_f = 10 bar, what is the approximate final temperature? If I instead start with T_i = 210 K, what is the final temperature? Figure 4.12. Lines of constant enthalpy (approximately horizontal, at intervals of 400 J/mol) and inversion curve (dashed) for hydrogen. In a throttling process the enthalpy is constant, so cooling occurs only to the left of the inversion curve, where the enthalpy lines have positive slopes. The heavy solid line at lower-left is the liquid- gas phase boundary. Data from Vargaftik (1975) and Woolley et al. (1948).

Explanation / Answer

Ans:- for air k=1.4,P1= 50 bar T1 = 50k P2 = 10bar T2 = ?

T2 /T1 = (P2/P1)^k-1/k

T2 = T1*(P2/P1)^k-1/k

T2 = 50*(10/50)^0.29 = 31.57k = 32k

If T1 = 210k T2 = ?

T2 = 210*(10/50)^0.29 = 132.59k =133k

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