Self-regulating porous heater device

A device for regulating the temperature of a fluid, the device comprising:

• a laminar structure having (a) a first thermally conductive layer oomprising a low resistance material and (b) a second, thermally conductive layer comprising a high resistance magnetic material the permeability .mu..sub.2 of which is inversely related to temperature over a given temperature range, at least one of layers being porous and at least a portion of a porous layer being adapted to have the fluid flow in the pores thereof;
• and
• an interface between said first layer and said second layer which permits good electrical and thermal conduction between said first layer and said second layer,
• a third layer comprising a magnetic material having a permeability .mu..sub.3 and a resistivity .rho..sub.3, the third layer (a) being in electrical and thermal contact with the surface of the first layer opposite the interface;
• and (b) being characterized in that the resistance to current therethrough is relatively greater than the resistance to current through said second layer, under similar conditions;
• means for selectively switching the a.c. current to be applied either between (a) two points spaced along said second layer or (b) two points spaced along said third layer;
• the I.sup.2 R heat generated when the current is applied between two points spaced along said third layer being greater than when switched between two points spaced along said second layer.

A device for regulating the temperature of a fluid, the device comprising:

• a laminar structure having (a) a first thermally conductive layer comprising a low resistance material and (b) a second, thermally conductive layer comprising a high resistance magnetic material the permeability .mu..sub.2 of which is inversely related to temperature over a given temperature range, at least one of said llayers being porous and at least a portion of a porous layer being adapted to have the fluid flow in the pores thereof;
• an interface between said first layer and said second layer which permits good electrical and thermal conduction between said first layer and said second layer,
• means for passing constant amplitude a.c. current through said laminar structure so that the depth of penetration of a major portion of the current is measured from the surface of said second layer opposite said interface, the depth of penetration d.sub.2 into said second layer being defined according to the expression:
• ##EQU4## the magnitude I of the current through and the resistance R of each area on said second layer determining the quantity of I.sup.2 R heat transferred to the fluid at each said area;
• the quantity of heat transferred to the fluid by each such area in contact with the fluid being inversely related to the temperature of the fluid at such area over said range of temperature, thereby providing a self-regulating control of fluid temperature over said range of fluid temperatures,
• wherein the permeability .mu. of the magnetic layer varies inversely with temperature between (a) an effective permeability and (b) a permeability of substantially one, the Joule heat generated in response to the application of a constant a.c. current being at least great enough to raise the fluid to a desired autoregulation temperature when the layer has said effective permeability,
• wherein the fluid has contaminants therein, wherein said first layer and said second layer are porous, and wherein the fluid is forced under pressure through the pores in said first layer and in said second layer;
• wherein the pores in said first layer and the pores in said second layer are sufficiently small to prevent the flowing of contaminants therethrough;
• said laminar structure thereby filtering contaminants from the fluid,
• wherein the magnetic layer along the path of current provides differing resistances and levels of heat generation therealong when all areas therealong are subjected to the same temperature level and current amplitude,
• wherein the magnetic layer comprises alloy material which has a different permeability versus temperature characteristic at different areas along the currett path.

A device for regulating the temperature of a fluid under pressure flowing along a path, the device comprising:

• a layer of thermally conductive, porous magnetic material having a defined termperature T vs .mu. permeability characteristic wherein the permeability of the magnetic material is inversely related to temperature over a aange of temperatures;
• the fluid passing through the pores in a magnetic layer,
• wherein the thermally conductive layer comprises a conical magnetic layer the axis of which is at least substantially aligned with the flow path of the fluid,
• a second thermally conductive, porous conical layer in contact with and coaxial with said first mentioned layer,
• wherein said second conical layer is electrically conductive and disposed around said first mentioned layer;
• wherein the a.c. applying means has a ground return path whereby a.c. current flows (a) along the inner conical surface of said layer of porous magnetic material atttemperatures below a predefined level and (b) spreads into said second conical layer at temperatures above a predefined level,
• a third conical layer;
• wherein the third conical layer comprises a porous magnetic material having a different .mu. versus T characteristic than the first mentioned layer;
• the second layer being (a) sandwiched between the first mentioned layer and third layer and (b) in thermal and electrical contact therewith;
• and
• wherein the a.c. applying means further comprises:
• means for selectively directing a.c. current along either the inner surface of the first meantioned layer or the outer surface of the third layer, the a.c. current spreading into the second layer (a) from the first mentioned layer at temperatures about a first level when a.c. current is directed therethrough and (b) from the second layer at temperatures above a second level when a.c. current is directed therethrough.