Reference no: EM13946088

Many of the solid surfaces for which values of the thermal and momentum accommodation coefficients have been measured are quite different from those used in micro- and nanodevices. Plot the Nusselt num- ber NuD associated with fully developed laminar flow with constant surface heat flux versus tube diameter for  1 µ,m D 1 mm  and  (i)  at  = 1,  ap  = 1,   (ii) at = 0.1, ap = 0.1, (iii)  at = 1,  ap = 0.1,  and  (iv) at = 0.1, ap = 1. For tubes of what diameter do the accommodation coefficients begin to influence con- vection heat transfer? For which combination of at and ap does the Nusselt number exhibit the least sensitivity to changes in the diameter of the tube? Which combi- nation results in Nusselt numbers greater than the con- ventional fully developed laminar value for constant heat flux conditions, NuD = 4.36? Which combination is associated with the smallest Nusselt numbers? What can you say about the ability to predict convection heat transfer coefficients in a small-scale device if the accommodation coefficients are not known for mate- rial from which the device is fabricated? Use proper- ties of air at atmospheric pressure and T = 300 K.