The invention arises from research on the diagnostic testing of a device, the subject of pending U.S. patent application Ser. No. 07/439,829 now U.S. Pat. No. 5,288,336, in respect of which the Applicant is a co-inventor. Prototypes of that device were found to have what seemed to be inexplicably-high operational efficiency, freezing water virtually instantaneously when powered by electricity. They comprised what may be termed a `series capacitor stack` formed by layers of a substrate dielectric metal, each coated using different metals (a layer of nickel and a layer of aluminium) and assembled between two metal plates which formed heat sinks.
The flow of heat through the bimetallic aluminium:nickel metallized layers from a hot heat sink to a cold heat sink caused the internal circulation of a thermoelectric current within each layer. The device operated with an astonishing efficiency by virtue of an electrical oscillation set up in the stack in a direction transverse to the heat flow direction and, indeed, transverse to what, in a conventional thermopile, would be the main Peltier EMF powered current path, but which in this prototype device was merely the local current circulation due to the secondary action of the Thomson effect. Research investigation indicated that this oscillating current activated the device in a most unusual way, primarily in interrupting the thermocouple junction currents at the oscillation frequency, an action which was found to enhance the thermoelectric EMF enormously. Compared with the normal thermo-electric EMF of 17 .mu.V/K for an aluminium:nickel thermocouple, an EMF of the order of 300 .mu.V/K resulted with the A.C. dynamic excitation at kilocycle frequency.
This led in the prototype research to the construction of extremely efficient thermopiles in the form of a capacitor stack with its heat throughput axis in one direction and the A.C. electric power throughput axis in the transverse direction. The device operated with high efficiency as a solid state heat pump powered directly by electricity or, when subjected to a temperature differential, as an electric power generator. Indeed, the device at room temperature demonstrably operated an electric motor when powered by melting ice and similarly would freeze water when powered by electrical input from a small battery.
The background of this subject invention is, therefore, the above prototype research using transverse oscillating A.C. field excitation in conjunction with the thermoelectric D.C. circulation in thin bimetallic layers forming capacitor plates in a series-connected stack.
The advance which is of primary importance and which is introduced by this invention to distinguish it from the disclosure in the above-referenced patent specification comes from a research investigation into the mysterious feedback process which must be present to give account of the extremely high efficiency observed.
The feedback feature has two aspects which relate respectively to a catalytic heat transfer role played by electric field priming and/or magnetic field priming and, it would seem an aspect common to both, as an action whereby an electric field mutually orthogonal in direction to both a heat flow axis and a magnetic field can regulate the heat transfer role of the magnetic field.
The physical basis of such feedback will be explained as the invention is described in detail but to distinguish its novelty and meritorious features from the published art it is noted that all prior art thermoelectric devices operate in D.C. mode. The current flow through the thermopile of such devices is direct current because the heating and cooling functions interchange at each junction if alternating current is used.
It has been suggested that a thermocouple can operate at high frequency but the action was still basically a direct current action, though one operating at a pulsation frequency. This is the proposal in U.S. Pat. No. 1,809,475 (Inventor R. B. Dowler), where the series circuit through a conventional thermopile arrangement was shown to be assembled in what appears to be a grid-controlled vacuum tube in which the grid is powered by a signal from a resonant circuit. The current through the thermopile passes through the anode-cathode path and so would be subject to the radio-frequency oscillations regulated by the grid control.
Another prior art disclosure of interest is that of inventor Hines in U.S. Pat. No. 3,460,015 which shows two metallic layers having a contiguous interface and sandwiched by insulation between two metal bodies which are to be moved slightly relative to one another in a position control system. The metals mentioned were iron and copper. The displacement was caused by thermal expansion which is a function of the heating or cooling of the bimetallic layers. Here, by passing a direct current one way or the other through the bimetallic layer, the junction formed between the layer is heated or cooled and so the system adjusts. However, though this is an arrangement in which a sandwich structure of insulation and two metals is used, the function is that of a single excited D.C. powered junction. The thermocouple, as such, involves complementary junctions which lie outside the part of the system which is to be moved by thermal expansion or contraction, so that a control that involves heating in the operational part of the system is matched by an external dissipatory function that involves the counterpart cooling.
One of the embodiments of the invention to be described involves metal fins which protrude from the capacitor stack alternately on opposite sides to provide a heating and cooling interface with air or other gas used to facilitate heat transfer. This may resemble a proposal in Japanese Patent Application No. 63-257564 (Applicants: Matsuchita Electric Ind. Co. Ltd. ), but an important distinguishing feature is present in the subject invention.
Reference is also made to the disclosure in U.S. Pat. No. 5,065,085 of which this Applicant is a co-inventor. That disclosure concerns the enhancement of thermoelectric action in an energy converter involving A.C. oscillations in bulk metal structures subjected to a magnetic field. The research and development effort arising from that project has, however, concentrated more on the techniques of fabrication of what is specifically described in the copending U.S. patent application already referenced, which, together with the invention to be described below, offers certain advantages.