1. Field of the Invention
This invention relates generally to electric space heaters, and more particularly, to space heaters wherein air is heated by moving the air through a heat exchanger which is heated by elongated incandescent lamps.
2. Description of the Prior Art
The concept of an electric space heater utilizing incandescent or other electric lamps as a heat source, with a fan and a heat exchanger mounted within a housing is well known. An example of such a space heater is disclosed in U.S. Pat. No. 4,307,284 issued to Leo Perron on Dec. 22, 1981. Perron discloses an electrical space heater unit in which conventional incandescent bulbs are mounted in a housing and a metal strip with metal fins is provided directly above and in contact with the incandescent bulbs to serve as a heat exchanger. The upper portion of the housing is open for passage of heated air from the housing into the space to be heated.
Another electric space heater is disclosed in U.S. Pat. No. 4,309,594 issued to John P. Jones on Jan. 5, 1982. Jones discloses a modular space heater device in which conventional infrared heat lamps are mounted in a housing and a heat exchanger plate is mounted above the bulbs. The heat exchanger plate has a number of openings with open ended pipes mounted in the openings for air to pass through. A fan blows air from an inlet in the housing across the infrared bulbs, around the heat exchanger plate, through the tubes in the heat exchanger plate and through an open outlet in the housing.
U.S. Pat. No. 4,680,448 issued to Earl Fester on July 14, 1987 discloses a space heater very similar to the heater disclosed by Jones, but with a different type of heat exchanger. Fester discloses a heat exchanger comprising a plurality of parallel copper tubes, surrounded by a plurality of parallel aluminum fins connected to and perpendicular to the tubes. A portion of the fins are coated with a black carbon paint.
The above-described space heaters fail to maximize efficiency because the heat exchangers do not surround the heat source, and thus do not absorb and transfer as much heat as possible. Considerable heat from the lamp is lost because it is directed away from the heat exchanger. Also, existing units seem to cause undue turbulence of the air flow, thus reducing efficiency. The sharp corners or convoluted air flow channels of existing heaters generate turbulence. The spherical or conical shape of the lamps which serve as a heat source also contribute to turbulence. Furthermore, the spherical or conical shape of the lamps in existing heaters creates an uneven distribution of heat in the heat exchangers. Existing portable space heaters can generally produce approximately 5200 BTU of heat at 1500 watts of power.
It is desirable to be able to enhance the efficiency of such electric space heaters by maximizing the heat transfer from the heat source to the air moving through the space heater. Efficiency can be enhanced by providing means to more evenly distribute heat over a heat exchanger, enabling the heat exchanger to absorb more heat, and laminating the air flow through the heater.