Regenerator matrix with mixed screen configuration

Abstract

A regenerator matrix 215 disposed in a fluid conduit 152 for exchanging thermal energy with a fluid passing through the fluid conduit. The regenerator matrix 215 has a variable fluid flow resistance and a variable capacity for convective heat transfer with the fluid along it longitudinal length. Preferably, the flow resistance and the capacity for convective heat transfer between the fluid and the regenerator matrix each increase as the fluid flows from a hot end to a cold end of the fluid conduit 152 . The regenerator matrix 215 is formed from individual screen elements 50 or from stacks of screen elements sintered together as composite regenerator elements 110 . A first portion 235 of the regenerator matrix made from first individual screen elements is disposed at the hot end of the regulator matrix 215 . A second portion 210 of the regenerator matrix made from second individual screen elements is disposed at the cold end of the regulator matrix. A third portion 230 of the regenerator matrix made from third individual screen elements is disposed between the first portion 235 and the second portion 210 . The first portion 235 has the lowest flow resistance and convective thermal energy transfer capacity, the second portion has the highest flow resistance and convective thermal energy transfer capacity, and the third portion has an intermediate flow resistance and convective thermal energy transfer capacity.

1 . A thermal energy exchange apparatus for exchanging thermal energy with a fluid comprising:
 a hollow coldwell tube disposed along a longitudinal axis between an open hot end and a sealed cold end;   a regenerator piston installed within the hollow coldwell tube and reciprocally movable with respect thereto comprising a hollow tube forming a fluid conduit extending along the longitudinal axis from an open hot end thereof to an open cold end thereof and wherein reciprocal movement of the regenerator piston along the longitudinal axis cyclically varies a volume of an expansion space formed between the coldwell tube sealed cold end and the fluid conduit open cold end and further causes the fluid to flow through the fluid conduit;   a regenerator matrix disposed to substantially fill the fluid conduit wherein the regenerator matrix comprises;   one more first composite regenerator elements loaded into the fluid conduit to form a first portion of the regenerator matrix proximate to the hot end wherein the first composite regenerator elements are formed from first individual wire screen elements sintered together in a stack with each first individual wire screen element having a substantially identical first wire surface area and first void volume;   one or more second composite regenerator elements loaded into the fluid conduit to form a second portion of the regenerator matrix proximate to the cold end wherein the second composite regenerator elements are formed from second individual wire screen elements sintered together in a stack with each second individual wire screen element having a substantially identical second wire surface area and second void volume;   wherein the second wire surface area is greater than the first wire surface area and the second void volume is less than the first void volume.   
   
   
       2 . The thermal energy exchange apparatus of  claim 1  further comprising:
 one or more third composite regenerator elements loaded into the fluid conduit to form a third portion of the regenerator matrix disposed between the first portion and the second portion wherein the third composite regenerator elements are formed from third individual wire screen elements sintered together in a stack with each third individual wire screen element having a substantially identical third wire surface area and third void volume wherein the third wire surface area is less than the second wire surface area and greater than the first wire surface area and further wherein the third void volume is greater than the second void volume and less than the first void volume.   
   
   
       3 . The thermal energy exchange apparatus of  claim 2  wherein:
 the first individual screen elements comprise wires having a diameter of 0.0021 inches and a screen pitch of 200 wires per inch;   the second individual screen elements comprise wires having a diameter of 0.0012 inches and a screen pitch of 400 wires per inch; and,   the third individual screen elements comprise wires having a diameter of 0.0014 inches and a screen pitch of 325 wires per inch.   
   
   
       4 . The thermal energy exchange apparatus of  claim 1  wherein each of the first and second composite regenerator elements comprises a stack of 2 to 25 individual screen elements. 
   
   
       5 . The thermal energy exchange apparatus of  claim 3  wherein each of the first, second and third composite regenerator elements comprises a stack of 2 to 25 individual screen elements. 
   
   
       6 . The thermal energy exchange apparatus of  claim 3  wherein each of the first, second and third individual screen elements is formed with a weave pattern axis and further wherein each of the first second and third composite regenerator elements is assembled in the stack with alternating adjacent individual screen elements rotated to align the weave pattern axes thereof with one of two different alignment axes. 
   
   
       7 . The thermal energy exchange apparatus of  claim 6  wherein the two different alignment axes are separated by an angle of 45 degrees. 
   
   
       8 . A thermal energy exchange apparatus for exchanging thermal energy with a fluid comprising:
 a hollow coldwell tube disposed along a longitudinal axis between an open hot end and a sealed cold end;   a regenerator piston installed within the hollow coldwell tube and reciprocally movable with respect thereto comprising a hollow tube forming a fluid conduit extending along the longitudinal axis from an open hot end thereof to an open cold end thereof and wherein reciprocal movement of the regenerator piston along the longitudinal axis cyclically varies a volume of an expansion space formed between the coldwell tube sealed cold end and the fluid conduit open cold end and further causes the fluid to flow through the fluid conduit; and,   a regenerator matrix disposed along the longitudinal axis to substantially fill the fluid conduit for exchanging thermal energy with the fluid as the fluid passes through the fluid conduit from the hot end to the cold end and from the cold end to the hot end, wherein the regenerator matrix is configured with a fluid flow resistance and with a capacity for convective heat transfer with the fluid that each vary along the longitudinal axis.   
   
   
       9 . The regenerator device of  claim 8  the regenerator matrix has minimum fluid flow resistance and minimum convective heat transfer capacity proximate to the hot end, and maximum fluid flow resistance and maximum convective heat transfer capacity proximate to the cold end. 
   
   
       10 . The regenerator device of  claim 9  wherein the regenerator matrix includes three portions disposed along the longitudinal axis with a first portion disposed proximate to open hot end, a second portion disposed proximate to the open cold end and a third portion disposed between the first portion and the second portion and wherein the first portion is formed with a first fluid flow resistance and capacity for convective heat transfer with the fluid, the second portion is formed with a second fluid flow resistance and capacity for convective heat transfer with the fluid and the third portion is formed with a third fluid flow resistance and capacity for convective heat transfer with the fluid. 
   
   
       11 . The regenerator device of  claim 10  wherein the regenerator matrix comprises individual screen elements with each individual screen element comprising wires woven together in a weave pattern wherein each wire screen element has a wire surface area, a void volume and a weave pattern axis. 
   
   
       12 . The regenerator of device of  claim 11  wherein:
 the first portion comprises a plurality of substantially identical wire screen elements formed from first individual wire screen elements having a first wire surface area and a first void volume;   the second portion comprises a plurality of substantially identical wire screen elements formed from second individual wire screen elements having a second wire surface area and a second void volume; and,   the third portion comprises a plurality of substantially identical wire screen elements formed from third individual wire screen elements having a third wire surface area and a third void volume.   
   
   
       13 . The regenerator device of  claim 11  wherein the regenerator matrix comprises stacks of two or more substantially identical wire screen elements sintered together. 
   
   
       14 . The regenerator device of  claim 13  wherein each stack is assembled with the weave pattern axis of alternating adjacent individual screen elements in the stack aligned with one of two different alignment axes. 
   
   
       15 . The thermal energy exchange apparatus of  claim 14  wherein the two different alignment axes are separated by an angle of 45 degrees. 
   
   
       16 . A method for exchanging thermal energy between a fluid and a regenerator matrix comprising the steps of:
 disposing a fluid conduit along a longitudinal axis with an open hot end for receiving hot fluid for therein and with an open cold end for delivering cold fluid out therefrom;   forming the regenerator matrix by filling the fluid conduit with individual screen elements each comprising wires woven together in a weave pattern wherein each individual screen element has a wire surface area, a void volume and a weave pattern axis; and,   varying the wire surface area and void volume of individual screen elements along the longitudinal axis to thereby vary a flow resistance of the regenerator matrix along the longitudinal axis and to further vary a capacity for convective heat transfer between the regenerator matrix and the fluid along the longitudinal axis.   
   
   
       17 . The method of  claim 16  further comprising the step of forming the regenerator matrix with minimum flow resistance and maximum capacity for convective heat transfer between the regenerator matrix and the fluid at the hot end and a maximum flow resistance and minimum capacity for convective heat transfer between the regenerator matrix and the fluid at the at the cold end. 
   
   
       18 . The method of  claim 18  further comprising the steps of:
 forming a first regenerator portion from a plurality of first individual screen elements each having a first wire surface area and a first void volume, wherein the first regenerator portion is disposed proximate to the hot end;   forming a second regenerator portion from a plurality of second individual screen elements each having a second wire surface area and a second void volume, wherein the second regenerator portion is disposed proximate to the cold end; and,   forming a third regenerator portion from a plurality of third individual screen elements each having a third wire surface area and a third void volume, wherein the third regenerator portion is disposed between the first regenerator portion and the second regenerator portion.   
   
   
       19 . The method of  claim 16  wherein each of the individual screen elements has a weave pattern axis, further comprising the step of; assembling the regenerator matrix by aligning the weave pattern axis of alternating adjacent individual screen elements with one of two different alignment axes. 
   
   
       20 . The method of  claim 19  wherein the step of aligning the weave pattern axis of alternating adjacent individual screen elements with one of two different alignment axes comprises rotating the weave pattern axis of alternating adjacent individual screen element by 45 degrees. 
   
   
       21 . The method of  claim 18  further comprising the steps of:
 forming the first regenerator portion from a plurality of stacks each comprising a plurality of the first individual screen elements sintered together in a stack with the weave pattern axis of alternating adjacent individual screen elements in the stack aligned with one of two different alignment axes;   forming the second regenerator portion from a plurality of stacks each comprising a plurality of the second individual screen elements sintered together in a stack with the weave pattern axis of alternating adjacent individual screen elements in the stack aligned with one of two different alignment axes; and,   forming the third regenerator portion from a plurality of stacks each comprising a plurality of the third individual screen elements sintered together in a stack with the weave pattern axis of alternating adjacent individual screen elements in the stack aligned with one of two different alignment axes.   
   
   
       22 . The thermal energy exchange apparatus of  claim 21  wherein the two different alignment axes are separated by an angle of 45 degrees.