Example using the long-pipe approximation

The example calculated in Section 6.7 will be recalculated using the explicit, long-pipe approximation. All the same physical data will be used. 

and so we may turn to Table A2.6 to find the appropriate polynomial coefficients. We have already calculated (Section 6.7) that Kt = 6.1%, and so we select Table A2.6(b). Applying the polynomial equations (6.66), (6.67) and (6.68) using the coefficients from Table A2.6(b) gives the following results  

7266 is greater than the critical pressure ratio, 0.2466, and so no choking will occur, and py/p = Pa/P - 

0917 is less than the critical pressure ratio. Choking will occur, and pa/p, = pj /pi = 0.2466. 

Since the supply pressure is 1 101 000 Pa, it follows that the pressure at the pipe outlet is predicted to be 271510 Pa. 

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