Abstract: An evacuated tube solar thermal collector uses a set of evacuated solar thermal collector tubes in heat exchanging contact with a fluid flowing through a header tube. Two heat pipes are provided in each evacuated thermal collector tube, and the condenser ends of the heat pipes are positioned in the header tube with a spacing that provides improved heat transfer from the heat pipes to the header tube. When 14 mm heat pipes contained in 58 mm collector tubes are used in a header tube having a capacity of about 0.5 gallons with a heat transfer liquid that is flowing at a rate of about 0.3 gpm, the spacing between heat pipes in each collector tube is about 24 mm, center to center, and the spacing between corresponding heat pipes of immediately-adjacent collector tubes is about 80 mm.

Abstract: An evacuated tube solar thermal collector uses a set of evacuated solar thermal collector tubes in heat exchanging contact with a fluid flowing through a header tube. Two heat pipes are provided in each evacuated thermal collector tube, and the condenser ends of the heat pipes are positioned in the header tube with a spacing that provides improved heat transfer from the heat pipes to the header tube. When 14 mm heat pipes contained in 58 mm collector tubes are used in a header tube having a capacity of about 0.5 gallons with a heat transfer liquid that is flowing at a rate of about 0.3 gpm, the spacing between heat pipes in each collector tube is about 24 mm, center to center, and the spacing between corresponding heat pipes of immediately-adjacent collector tubes is about 80 mm.