GB1063098A - Improvements in heat exchangers - Google Patents

Abstract

A hollow heat exchanger element having two opposed parallel walls and a plurality of integrally formed tubular elements 13 extending between said walls, (see Division F4), is made by an electro-forming process. Firstly a matrix 32, e.g. as in Fig. 14, is made in the shape of the interior of the element and is produced from a low melting <PICT:1063098/C6-C7/1> <PICT:1063098/C6-C7/2> point metal alloy. The matrix may be produced by gravity or die casting. Alternatively the matrices may be produced from paraffin wax or a synthetic resin mixed with a conductive material such as graphite or coated with a conductive layer of either a metal or graphite applied as a suspension in an organic solvent. A matrix formed of a non-conductive material may also be provided with a conductive layer, e.g. a metal. The matrix is in any case coated with a layer of graphite deposited from an organic solvent dispersion as a release layer for the electro-deposits. The matrix is then subjected to an electro-forming process, an example comprising applying successive thin coatings of nickel, copper, nickel. The nickel may be deposited from a Watts bath and the copper plated from a pyrophosphate bath containing also oxalate and nitrate. When the electro-forming is complete the matrix is melted or evaporated out leaving a thin-walled box-type shell from which any residues are removed by chemical cleaning. In the element of Fig. 9 the strengthening 31 may be formed by the electro-forming or inserted afterwards.