Combination gas combuster and heat pipe evaporator device

Abstract

A combination gas combustor and heat pipe evaporator comprised of elongated cylindrical tubes which overfit one another to create a number of longitudinal gas flow passages. A burner disposed at one end of the device creates hot flue gases which travel initially through an annular passage where heat is conducted to the working fluid of a heat pipe evaporator chamber. The flue gas flow is then reversed in direction to heat the radially outer surface of the tubes making up the heat pipe evaporator, and thereafter flow through passages to warm inlet air to increase combustion efficiency. For both described embodiments, a bellows is provided to accommodate differences in thermal expansion between the tubes making up the heat pipe evaporator. In accordance with a first embodiment, the primary flue gas transport channel has a decreasing annular width with distance from the combuster which results in a lowering Reynolds number for flow which provides a more uniform heat flux along the length of the device. In a second embodiment, the central post is hollow and forms a portion of the heat pipe evaporator. The tubes making up the evaporator chamber may be eccentrically located to provide a narrow bottom gap for longitudinal distribution of liquid phase working fluid and a larger upper gap for escape of vapor phase working fluid.