A solar collector design consists of an inner tube enclosedconcentrically in an outer tube that is transparent to solarradiation. The tubes are thin walled with inner and outer diametersof 0.08 and 0.10 m, respectively. The annular space between thetubes is completely enclosed and filled with air at atmosphericpressure. Under operating conditions for which the inner and outertube surface temperatures are 80 and 30°C, respectively, what isthe rate of convective heat loss per meter of tube length acrossthe air space?
