Considere un colector solar de aire que tiene 1 m de ancho y 5 m de largo y un espaciamiento constante de 3 cm entre la cubierta de vidrio y la placa del propio colector. El aire entra en el colector a 30°C a razón de 0.15m3 /s por el borde de 1 m de ancho y fluye a lo largo del paso de 5 m de largo. Si las temperaturas promedio de la cubierta de vidrio y de la placa del colector son de 20°C y 60°C, respectivamente, determine a) la razón neta de la transferencia de calor hacia el aire conforme fluye por el colector y b) la elevación de temperatura del aire conforme fluye a través del colector.

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?