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 number Nu_D associated with fully developed laminar flow with constant surface heat flux versus tube diameter for 1 μm ≤ D ≤ 1 mm and 

(i) α_t = 1, α_p = 1,

(ii) α_t = 0.1, α_p = 0.1, 

(iii) α_t = 1, α_p = 0.1, and .

(iv) α_t = 0.1, α_p = 1. 

For tubes of what diameter do the accommodation coefficients begin to influence convection heat transfer? For which combination of α_t and α_p does the Nusselt number exhibit the least sensitivity to changes in the diameter of the tube? Which combination results in Nusselt numbers greater than the conventional fully developed laminar value for constant heat flux conditions, Nu_D = 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 material  from which the device is fabricated? Use properties of air at atmospheric pressure and T = 300 K.