Patent GB-1145858-A (GB)
Title: Thermoelectric assembly
IPC: F25B21/02
Filed: 1966-06-01
Abstract: 1,145,858. Thermoelectric devices. T. M. ELFVING. 1 June, 1966 [1 June, 1965; 14 June, 1965], No. 24486/66. Heading H1K. In a thermoelectric heat pump a heat exchanger to a gaseous medium comprises a bimetallic member serving as a junction bridge and consisting of a first part of a metal of good conductivity, e.g. copper, in contact with the semi-conductor body, and a second part of or containing aluminium in contact with the gaseous medium, the semi-conductor body being prestressed by compression means acting along a centre line parallel to the direction of the current path. As shown, Fig. 1, two blocks 11, 12 of semiconductor material of opposite types are soldered between copper strips 13 and end plates 16 using a bismuth-tin solder. Strips 13 are shaped to fit the cylindrical surface of a tube 14 which may be of copper or of aluminium with a copper sheath. Soft solder is provided at the joints between strips 13 and tube 14, the assembly is compressed, and insulating material 22 such as an epoxy resin is applied to encapsulate the device. While the resin is curing the assembly is heated to solder the strips 13 to the tube 14. When it has hardened, the encapsulation maintains the elements in compression. Heat exchangers comprising copper tubes 17 provided with aluminium fins 19, may be soldered to the end plates 16. The copper end plates may be nickel plated. In a modification, Figs. 3 and 4 (not shown), the thermoelectric elements are maintained in compression by means of a pair of bolts engaging ears provided on the end plates. In a second embodiment, a single thermoelectric element is mounted between a pair of end plates to which are soldered finned heat exchangers. The thermoelectric elements can be maintained under compression by an encapsulation of a foamed P.V.C. or poxy resin, Figs. 5 and 6 (not shown), by a central bolt, the element being annular or comprising a plurality of bodies arranged in an annulus, Figs. 7 and 8 (not shown), by a plurality of bolts symmetrically arranged round the element, Fig. 11 (not shown) or by a clamp encircling the edges of the end plates, Figs. 12 and 13 (not shown). In a further embodiment, Figs. 9 and 10 (not shown) a pair of annular thermoelectric elements are provided, each being soldered between an end plate and a washer, the washers being bridged by a finned heat exchanger. The assembly is held in compression by a spring bolt or by a bolt with a compression spring under its head or nut. The space inside the assembly is filled with foamed insulator and sleeves of insulating material cover the outsides of the thermoelectric elements. Each of the thermoelectric elements may comprise a plurality of bodies arranged in an annulus. Various assemblies of the device are described, Figs. 14 to 19 (not shown), and include ones in which the junctions between pairs of annular elements are alternately washers or blocks connected to centrally disposed fluid tubes and circumferentially arranged finned tubes, Figs. 20 and 23 (not shown). It is stated that the compressive force may be such as to obviate the need for soldering the parts together. The contacts may be improved by applying silicone grease or metallic compounds, and the parts may have locating grooves, flanges or depressions.