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An improved solid heat transfer element composed of an elongate member having a generally cylindrical surface with male vortex generating protrusions is provided. The vortex generating protrusions, which may be referred to as “turbulators,” provide improved heat transfer by convection to a flow of a

An improved solid heat transfer element composed of an elongate member having a generally cylindrical surface with male vortex generating protrusions is provided. The vortex generating protrusions, which may be referred to as “turbulators,” provide improved heat transfer by convection to a flow of air transverse to the elongate members without substantially increasing the pressure drop in the flow of air passing over the members. Advantageously, a plurality of the heat transfer elements, or of straight portions of a single serpentine heat transfer element, may be arranged in an aligned or staggered array of elements or straight portions. Many advantageous profile shapes of the element and vortex generators are provided, including aerodynamic profile shapes that are symmetrical with respect to a fluid flow to provide low drag and pressure drop. Heat in the element may be generated by means of electrical resistance or absorption of radiation.

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1. A solid heat transfer element for generating heat from an electric current passing through its electrically resistant material and transferring the heat to an air flow in communication with the solid heat transfer element, comprising: an elongate member composed of an electrically resistive, heat

1. A solid heat transfer element for generating heat from an electric current passing through its electrically resistant material and transferring the heat to an air flow in communication with the solid heat transfer element, comprising: an elongate member composed of an electrically resistive, heat generating material, placed transversely to the air flow with an aerodynamic profile, symmetrical in respect to the air flow, the elongate member having a cylindrical surface including a surface area in contact with the air flow; andmale protrusions extending from the cylindrical surface of the elongate member into the fluid flow, the male protrusions configured to provide additional surface area in contact with the air flow and to generate vortices to mix heated air layers to increase the rate of heat transfer from the elongate member to the air flow, and the male protrusions being of a shape selected from the group consisting of an a tear drop shape and an egg shape, the male protrusion shape generally tapering to a narrower dimension in the direction of air flow. 2. The solid heat transfer element of claim 1, wherein said electrically resistive material is selected from the group consisting of FeCrAl, NiFe, NiCrFe, CuNi, CaCu, MoSi, Silicon Carbide, PTC ceramics and resistance wire encased in ceramics. 3. The solid heat transfer element of claim 1 wherein said solid elongate member is oriented transversely at an angle between 45 and 90 degrees with respect to the air flow. 4. An array of solid heat transfer elements according to claim 1 comprising an array of the solid elongate members. 5. The array of claim 4, wherein the array comprises a plurality of offset rows of the elongate members, each row comprising a plurality of the elongate members spaced apart in a direction transverse to the air flow and parallel to one another. 6. The array of claim 5, wherein each elongate member in a row is spaced in the direction of air flow from a corresponding elongate member in an adjacent row. 7. The array of claim 5, wherein the rows are staggered in relation to one another so that no elongate member in a row is spaced in the direction of air flow from a corresponding elongate member in an adjacent row. 8. The solid heat transfer element of claim 1, wherein the elongate member is formed in a serpentine bent pattern, the bent pattern including an array of straight portions of the elongate member, the array comprising a plurality of rows of the straight portions, each row comprising a plurality of the straight portions spaced apart in a direction transverse to the air flow and parallel to one another. 9. The solid heat transfer element of claim 8, wherein each straight portion in a row is spaced in the direction of air flow from a corresponding straight portion in an adjacent row. 10. The solid heat transfer element of claim 8, wherein the rows are staggered in relation to one another so that no straight portion in a row is spaced in the direction of air flow from a corresponding straight portion in an adjacent row. 11. The solid heat transfer element of claim 1 wherein said elongate member is helical. 12. The solid heat transfer element of claim 1 wherein at least a part of said solid elongate member is spiral shaped. 13. The solid heat transfer element of claim 1 wherein said elongate member has a symmetrical profile shape selected from the group consisting of aerofoils, tear drops, egg shapes, wedges, ellipses, circles, and ovals. 14. The solid heat transfer element of claim 1 wherein said vortex generating male protrusions are oriented at an angle of attack between about 0 and about 45 degrees with respect to the air flow. 15. A solid heat transfer element for absorbing energy from a source of electromagnetic radiation and transferring the energy as heat to a air flow in communication with the solid heat transfer element, comprising: an elongate member adapted to absorb electromagnetic radiation, the elongate member oriented transversely to the air flow and exposed to the source of electromagnetic radiation, the elongate member having a profile that is symmetrical with respect to the air flow, the elongate member having a cylindrical surface including a surface area in contact with the air flow; andmale protrusions extending from the cylindrical surface of the elongate member into the air flow, the male protrusions configured to provide additional surface area in contact with the air flow and to generate vortices to mix heated air layers to increase the rate of heat transfer from the elongate member to the air flow, and the male protrusions being of a shape selected from the group consisting of a tear drop shape and an egg shape, the male protrusion shape generally tapering to a narrower dimension in the direction of air flow. 16. The solid heat transfer element of claim 15, wherein said elongate member is adapted to absorb infrared radiation. 17. The solid heat transfer element of claim 16, wherein said elongate member includes a coating composed of a material adapted to absorb infrared radiation and a core composed of a material adapted to absorb heat energy conductively from the coating. 18. The solid heat transfer element of claim 15, wherein said elongate member is adapted to absorb radio waves, including microwaves. 19. The solid heat transfer element of claim 18, wherein said elongate member comprises a radio wave absorbing material selected from the group consisting of carbide, molybdenum, tungsten, silicon carbide, stainless steel and aluminum. 20. The solid heat transfer element of claim 15 wherein said elongate member is placed transversely at an angle between about 45 and about 90 degrees with respect to the air flow. 21. An array of solid heat transfer elements according to claim 15 comprising an array of the solid elongate members. 22. The array of claim 21, wherein the array comprises a plurality of offset rows of the elongate members, each row comprising a plurality of the elongate members spaced apart in a direction transverse to the air flow and parallel to one another. 23. The array of claim 22, wherein each elongate member in a row is spaced in the direction of air flow from a corresponding elongate member in an adjacent row. 24. The array of claim 22, wherein the rows are staggered in relation to one another so that no elongate member in a row is spaced in the direction of air flow from a corresponding elongate member in an adjacent row. 25. The solid heat transfer element of claim 15, wherein the elongate member is formed in a serpentine bent pattern, the bent pattern including an array of straight portions of the elongate member, the array comprising a plurality of rows of the straight portions, each row comprising a plurality of the straight portions spaced apart in a direction transverse to the air flow and parallel to one another. 26. The solid heat transfer element of claim 25, wherein each straight portion in a row is spaced in the direction of air flow from a corresponding straight portion in an adjacent row. 27. The solid heat transfer element of claim 25, wherein the rows are staggered in relation to one another so that no straight portion in a row is spaced in the direction of air flow from a corresponding straight portion in an adjacent row. 28. The solid heat transfer element of claim 15 wherein said elongate member is helical. 29. The solid heat transfer element of claim 15 wherein at least a part of said elongate member is spiral shaped. 30. The solid heat transfer element of claim 15 wherein said elongate member has a symmetrical profile shape selected from the group consisting of aerofoils, tear drops, egg shapes, wedges, ellipses, circles, and ovals. 31. The solid heat transfer element of claim 15 wherein said vortex generating male protrusions are oriented at an angle of attack of from about 0 to about 45 degrees with respect to the air flow. 32. The solid heat transfer element of claim 14 wherein said vortex generating male protrusions are oriented at an angle of attack of about 15 degrees with respect to the air flow. 33. The solid heat transfer element of claim 31 wherein said vortex generating male protrusions are oriented at an angle of attack of about 15 degrees with respect to the air flow. 34. The solid heat transfer element of claim 13, wherein said elongate member has a symmetrical profile shape selected from the group consisting of aerofoils and tear drops. 35. The solid heat transfer element of claim 30, wherein said elongate member has a symmetrical profile shape selected from the group consisting of aerofoils and tear drops.