$($a$,5$ points$)$ What is the overall heat transfer coefficient? How is it defined?

$($b$,$ points$)$ What is the fin effectiveness? Under what conditions are fins most effective?

$($c$,5$ points$)$ What is the fin efficiency? Under what conditions will the efficiency be large?

$($ d$,5$ points$)$ What is the thermal diffusivity?

$($ e$,5$ points$)$ Heat is transferred from hot water flowing through a tube lo ambient air. To effectively enhance the rate of heal transfer, should fins be installed on the tube interior or exterior surface? and why?

$($ f$,5$ points$)$ explain micro$/$nano scale effects of very fin films on k $($please specify the thermal conductivity in each coordinate$)$

$($ g$,5$ points$)$ What is radiation? What is irradiation?