Plastic heat exchange apparatus

Abstract

Hollow plastic filaments, useful in heat exchange systems, which are made from plastic compositions containing 5 to 45 percent by weight of filler particles having substantially higher thermal conductivity than the plastic and a diameter greater than 2.0 microns, will have high thermal conductivity and appreciable mechanical strength if the particles are chosen such that the ratio of the particle diameter to the wall thickness of the filament is between 0.001 and 0.5 and if the particles are dispersed within the plastic homogeneously enough to produce the desired mechanical stability and heterogeneously enough to take advantage of the high thermal conductivity of such a dispersion.

What is claimed is: 
     
       1. An improved heat exchanger of the type comprising: a casing member; a plurality of hollow, flexible fluid-tight plastic filaments; means for securing the end of said filaments in fixed relationship with said casing member, means for passing a first fluid through the interior of said filaments and means for passing a second fluid through said casing member into intimate contact with the outer surface of said filaments; the improvement wherein said filaments comprise a plastic composition containing 5 to 45 percent by weight of .Iadd.graphite .Iaddend.filler particles having a thermal conductivity substantially greater than the thermal conductivity of the plastic, substantially all of said filler particles having a diameter greater than 2.0 microns and the ratio of the diameter of said filler particles to the wall thickness of said filaments being 0.001 to 0.5, said filler particles having a distribution in said plastic composition which is homogeneous enough so that said filaments have a tensile strength greater than 1,000 psi and an elongation to failure of greater than 25 percent at room temperature and heterogeneous enough so that said filaments have a thermal conductivity greater than twice the thermal conductivity of said plastic. 
     
     
       2. The heat exchanger of claim 1 wherein said plastic is a polyfluorinated plastic .[.and said filler particles are filler particles which are substantially impervious to corrosive fluids..]. 
     
     
       3. The heat exchanger of claim 1 wherein the ratio of said diameter to the wall thickness of said filament is 0.001 to 0.1. .[.4. The heat exchanger of claim 1 wherein said plastic is a polyfluorinated plastic and said 
     
     
        filler particles are carbon filler particles..]. 5. The heat exchanger of claim .[.4.]. .Iadd.2 .Iaddend.wherein said polyfluorinated plastic is polyfluorinated plastic selected fom the group consisting of polymers of tetrafluoroethylene and copolymers of tetrafluoroethylene and hexafluoropropylene .[.and said carbon filler particles are graphite filler particles.].. .[.6. The heat exchanger of claim 1 wherein said filaments comprise a plastic composition containing 5 to 25 percent by weight of said filler particles, and wherein said filaments have a thermal conductivity greater than one and a half times the thermal conductivity of the plastic..]. .[.7. The heat exchanger of claim 6 wherein said plastic is a polyfluorinated plastic and said filler particles are graphite filler particles..]. .[.8. The heat exchanger of claim 7 wherein said filler particles have a diameter of 2.0 to 50 microns..]. .[.9. The heat exchanger of claim 1 wherein said filaments comprise a plastic composition containing 10 to 20 percent by weight of said filler particles, and wherein said filaments have a thermal conductivity of greater than one and a half times the thermal conductivity of the plastic..]. .[.10. The heat exchanger of claim 9 wherein said plastic is a polyfluorinated plastic and said filler particles are graphite filler particles having a diameter of 2.0 to 50 microns..]. .[.11. The heat exchanger of claim 10 wherein said polyfluorinated plastic is a polyfluorinated plastic selected from the group consisting of polymers of tetrafluoroethylene and copolymers of 
     
     
        tetrafluoroethylene and hexafuoropropylene..]. .Iadd.12.  An improved heat exchanger of the type comprising: a casing member, a plurality of hollow, flexible fluid-tight plastic filaments; means for securing the end of said filaments in fixed relationship with said casing member, means for passing a first fluid through the interior of said filaments and means for passing a second fluid through said casing member into intimate contact with the outer surface of said filaments; the improvement wherein said filaments comprise a plastic composition containing 5 to 45 percent by weight of graphite filler particles having a thermal conductivity substantially greater than the thermal conductivity of the plastic, substantially all of said filler particles having a diameter greater than 2.0 microns and the ratio of the diameter of said filler particles to the wall thickness of said filaments being 0.001 to 0.5, said filler particles having a distribution in said plastic composition which is homogeneous enough so that said filaments have a tensile strength greater than 1,000 psi and an elongation to failure of greater than 25 percent at room temperature and heterogeneous enough so that said filaments have a thermal conductivity greater than one and one-half times the thermal conductivity of the plastic. .Iaddend. .Iadd.13. An improved heat exchanger of the type comprising: a casing member, a plurality of hollow, flexible fluid-tight plastic filaments, means for securing the end of said filaments in fixed relationship with said casing member, means for passing a first fluid through the interior of said filaments and means for passing a second fluid through said casing member into intimate contact with the outer surface of said filaments; the improvement wherein said filaments comprise a plastic composition containing 10 to 20 percent by weight of graphite filler particles having a thermal conductivity substantially greater than the thermal conductivity of the plastic, substantially all of said filler particles having a diameter greater than 2.0 microns and the ratio of the diameter of said filler particles to the wall thickness of said filaments being 0.001 to 0.5, said filler particles having a distribution in said plastic composition which is homogeneous enough so that said filaments have a tensile strength greater than 1,000 psi and an elongation to failure of greater than 25 percent at room temperature and heterogeneous enough so that said filaments have a thermal conductivity greater than one and one-half times the thermal conductivity of the plastic. .Iaddend. 
     
     
        .Iadd.14.  The heat exchanger of claim 12 or 13 wherein said plastic is a polyfluorinated plastic. .Iaddend. .Iadd.15. The heat exchanger of claim 14 wherein said filler particles have a diameter of 2.0 to 50 microns. .Iaddend.