In a Rankine cycle system wherein a vapor generator receives heat from exhaust gases, provision is made to avoid overheating of the refrigerant during ORC system shut down while at the same time preventing condensation of those gases within the vapor generator when its temperature drops below a threshold temperature by diverting the flow of hot gases to ambient and to thereby draw ambient air through the vapor generator in the process. In one embodiment, a bistable ejector is adjustable between one position, in which the hot gases flow through the vapor generator, to another position wherein the gases are diverted away from the vapor generator. Another embodiment provides for a fixed valve ejector with a bias towards discharging to ambient, but with a fan on the downstream side of said vapor generator for overcoming this bias.
FEDERALLY SPONSORED RESEARCH
The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the term of Contract Nos.: FC02-00CH11060 and FC36-00CH11060 awarded by the Department of Energy.