Solar heat collector using replaceable glass tube - which is evacuated, and contains heat absorber through which heat transfer fluid is circulated

摘要

The glass tube is closed at both ends by a cap with a seal. Each cap has an axial channel through which a heat transfer medium is circulated, so it travels through an absorber located inside the tube. A channel is also provided for evacuating the tube, so the caps are held on the tube by atmos. pressure. The channel used to evacuate the tube is pref. provided with a non-return valve; and in one pref. design, one end cap forms both an inlet and an outlet for the heat transfer medium, so compensation can be provided for differential thermal expansion. The absorber pref. consists of several tubes brazed to a plate; or two plates forming a cavity for the circulating medium. The collector is simple and inexpensive. The relatively fragile glass tube can be replaced without renewing the other components.