Modeling and Design of Net ZEBs as Integrated Energy Systems - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 66

Fig. 2.17 Schematic of a vacuum tube collector (with a heat-pipe)
In a direct flow vacuum collector ( Figure 2.18 ), the working fluid circulates
through a tube welded to the absorber and can have one of the three
following configurations:
1. Two coaxial tubes; the fluid is supplied through the inner tube then
heats up and exits through the outer tube.