Patent GB-847548-A (GB)
Title: Method and apparatus for heat transfer
IPC: B29B13/02
Filed: 1958-06-10
Abstract: <PICT:0847548/IV(a)/1> In a method of obtaining and maintaining the effect of conductive heat transfer between a porous solid surface and a web moving past the surface, gas is forced through the porous surface under uniform pressure so as to form a thin gas layer of substantially uniform thickness between the porous surface and the web. Preferably the gas layer is maintained between 3 and 10 mils in thickness.  The web may be stretched in one or more directions during heat transfer and the temperature imparted to it may be such that molecular orientation may be effected on a web comprising polymeric material.  The gas may be a single gas, e.g. superheated steam, nitrogen or helium, or a mixture of gases, e.g. p  air.  The web may be in the form of a film or tube.  Suitable apparatus comprises a porous solid surface, means for the supply of gas and means for feeding a web past the porous solid surface. As shown, supply line 17 feeds gas to chamber 16, the upper wall 20 of which is porous.  Wall 20 may be constructed of sintered metal, e.g. bronze, small metal balls point-welded or soldered together, a sintered wire matrix or a metallic ceramic composition.  The porous surface may also be composed of a plurality of sections each maintained at a different temperature by heating/or cooling means contained therein.  Gas (derived from any convenient source of supply) escaping from chamber 16 prevents contact between web 10 and wall 20.  Wall 20 may be provided with a tubular heater 24 supplied with steam.  In a modification (Fig. 2, not shown) the porous surface over which the web is passed is arcuate, and in a further modification (Fig. 3, not shown) the web is heated from both sides by gas streams forced through opposing porous surfaces.  U.S.A. Specifications 2,130,665 and 2,519,375 are referred to.ALSO:<PICT:0847548/IV (c)/1> In a method of obtaining and maintaining the effect of conductive heat transfer between a porous solid surface and a web moving past the surface, gas is forced through the porous surface under uniform pressure so as to form a thin gas layer of substantially uniform thickness between the porous surface and the web. Preferably the gas layer is maintained between 3 and 10 mils in thickness.  The web may be stretched in one or more directions during heat transfer and the temperature imparted to it may be such that molecular orientation may be effected on a web comprising polymeric material.  The gas may be a single gas, e.g. superheated steam, nitrogen or helium, or a mixture of gases, e.g. air.  The web may be in the form of a film or tube. Suitable apparatus comprises a porous solid surface, means for the supply of gas and means for feeding a web past the porous solid surface. As shown, supply line 17 feeds gas to chamber 16, the upper wall 20 of which is porous.  Wall 20 may be constructed of sintered metal, e.g. bronze, small metal balls point-welded or soldered together, a sintered wire matrix or a metallic ceramic composition. The porous surface may also be composed of a plurality of sections each maintained at a different temperature by heating or cooling means contained therein.  Gas (derived from any convenient source of supply) escaping from chamber 16 prevents contact between web 10 and wall 20.  Wall 20 may be provided with a tubular heater 24 supplied with steam.  In a modification (Fig. 2, not shown) the porous surface over which the web is passed is arcuate, and in a further modification (Fig. 3, not shown) the web is heated from both sides by gas streams forced through opposing porous surfaces.  U.S.A. Specifications 2,130,665 and 2,519,375 are referred to.