Helium flows through an annular flow passage. The inner and outer diameters of the annulus are 120 and 120.7 cm, respectively. At a particular location, the pressure is 20 Pa, the helium mean...

Helium flows through an annular flow passage. The inner and outer diameters of the annulus are 120 and 120.7 cm, respectively. At a particular location, the pressure is 20 Pa, the helium mean temperature and velocity are −110 ◦C and 15 cm/s, respectively, and the heat flux at the wall surface is −1247W/m². Calculate the wall surface temperature, first by neglecting the rarefaction effect, and then by including the effect of rarefaction. Compare the results and discuss the difference between them.