Corrugated Tube Regenerator for an Expansion Engine

Abstract

A regenerative heat exchanger for transferring heat from the exhaust gas to the intake working fluid of a prime mover. Application includes gas turbines for both motor vehicles and distributed electric generation. The heat exchanger employs a rotating matrix, which circulates through working fluid exhaust and intake channels while absorbing and rejecting heat between the two channels. Features include corrugated tubes for enhanced heat transfer, minimally welded low stress construction, quick-detach assembly of standard components, and purge flow sealing using recovered heat. Effectiveness exceeding 95% increases thermal efficiency of low-pressure ratio gas turbines.

I claim: 
     
         1 . Rotary regenerator heat recovery means of a prime mover comprising heat transfer matrix means with corrugated heat transfer tubes inserted longitudinally in working fluid flow cells of said matrix means, wherein circumferential surface ridges and grooves of said corrugated tubes provide heat transfer enhancement, while said matrix provides transfer of exhaust gas heat of said prime mover to the higher pressure intake working fluid of said prime mover during rotation of said matrix about a central shaft of said regenerator means. 
     
     
         2 . The matrix means of  claim 1  comprising a one piece array of working fluid honeycomb cells containing said corrugated tubes for providing compact heat transfer surface means. 
     
     
         3 . The matrix means of  claim 1  comprising a packed array of working fluid tubular cells containing said corrugated tubes, wherein said array is retained at the periphery by essentially circular duct means for providing compact heat transfer surface means. 
     
     
         4 . The matrix means of  claim 3  comprising essentially line contact between said tubular cells, wherein said tubular cells are held in essentially hexagonal arrangement by said duct means, 
     
     
         5 . The heat transfer cells of  claim 1  comprising strip fin means disposed longitudinally through said corrugated tubes for providing further heat transfer enhancement of said matrix means. 
     
     
         6 . The regenerator means of  claim 1  comprising working fluid containment means constructed of first conduit fitting means and second conduit fitting means, wherein each said fitting means comprises a main branch with support means for said matrix and connection means for attachment of said first fitting means to said second fitting means, a pressurized branch for channeling compressed working fluid, and an exhaust branch for channeling exhaust working fluid. 
     
     
         7 . The support means of  claim 6  comprising purge flow distribution means, wherein pressure of purge flow to said distribution means is provided by a purge system with compression work means selected from the recovered energy group consisting of solar, building amplified wind, motor vehicle momentum, motor vehicle draft loss and motor vehicle shock. 
     
     
         8 . The purge system of  claim 7  comprising purge flow heating means wherein purge flow temperature is increased by recovered heat selected from the group consisting of combustor waste heat, compressor heat, motor vehicle transmission heat and stored solar heat. 
     
     
         9 . A method for constructing a heat transfer matrix of a rotary regenerator of a prime mover comprising the steps of:
 enclosing said matrix within an essentially circular duct disposed in essentially parallel relation to working fluid flow cells of said matrix,   inserting and retaining corrugated heat transfer enhancement tubes into said cells, and   inserting a matrix rotation shaft along the area centroid of said matrix, wherein said matrix provides transfer of exhaust gas heat of said prime mover to the higher pressure intake working fluid of said prime mover during rotation of said matrix about said shaft.   
     
     
         10 . The method of  claim 9  comprising the first step of sequentially packing cell tubes in essentially line contact within an essentially hexagonal arrangement to provide an array of tubular working fluid flow passages of said matrix. 
     
     
         11 . The method of  claim 10  comprising the next step of inserting filler tubes in essentially line contact with said cell tubes and with said duct for providing an essentially circular periphery of said matrix. 
     
     
         12 . The method of  claim 11  comprising the next step of attaching the periphery of at least one perforated retainer disk to said duct for retention of said corrugated tubes in said cell tubes, wherein perforations of said disk or disks provides for essentially unrestricted flow of working fluid through said disks. 
     
     
         13 . The method of  claim 12  comprising the next step of attaching said cell tubes to said disk or disks by a process selected from the group consisting of gasketing, interference fitting, welding and brazing, for limiting leakage of working fluid between ends of said cell tubes and said disk or disks. 
     
     
         14 . The method of  claim 10  comprising working fluid leakage limiting means, wherein material of said cell tubes and of said duct means are selected to limit the difference of diametral thermal expansion between said cell tubes and said duct. 
     
     
         15 . The method of  claim 14  comprising the first step of grinding or machining the outside diameter of said cell tubes, wherein line contact between said cell tubes is maintained within a specified tolerance range for limiting leakage of working fluid between said tubular cells. 
     
     
         16 . A rotary regenerator of a prime mover comprising:
 a heat transfer matrix containment vessel,   a rotating heat transfer matrix within said vessel, p 1  corrugated working fluid tubes inserted within working fluid flow passages of said matrix,   colder matrix end support bars within said containment,   hotter matrix end support bars within said containment, and   matrix shaft bearings within said bars,   
       wherein circumferential surface ridges and grooves of said corrugated tubes provide enhanced transfer of exhaust gas heat from a combustor and a turbine of said prime mover to the higher pressure intake working fluid from a compressor of said prime mover, during rotation of said matrix about a central shaft mounted to said bearings. 
     
     
         17 . The support bars of  claim 16  comprising purge flow distribution nozzles disposed radially with respect to said shaft and in direct fluid communication with at least one end of said bars, for passage and direction of purge flow from a purge system toward pressurized working fluid of said prime mover. 
     
     
         18 . The purge system of  claim 17  comprising a purge flow evaporator in contact with said compressor and a purge flow superheater in contact with said combustor, for providing steam from said evaporator to said colder matrix end support bars and steam from said superheater to said hotter matrix end support bars. 
     
     
         19 . The corrugated tubes of  claim 16  comprising strip fins inserted in said corrugated tubes for providing further heat transfer enhancement within said matrix. 
     
     
         20 . The corrugated tubes of  claim 16  comprising corrugation geometry, wherein the width of said grooves exceeds the width of said ridges to provide meshing of said tubes disposed in adjacent relation, for reducing the diameter of said matrix.