Coiled heat exchanger with beam spreader especially for use with solar-powered gas processors

Abstract

An apparatus and method for solar energy powered gas processing. There is disclosed a processor assembly for use in heating a process or feed gas by means of a convective heat exchanger which receives solar energy from a focused solar energy collector. A specialized heat exchanger is described, which includes a conical envelope into which a metal tube is spirally wound, such that the tube is coiled into a conical spiral corresponding generally to the envelope. A reflective beam spreader is situated near the vertex of the envelope cone to re-direct incident solar radiation toward the exchanger tube. The apparatus thus has a cavity into which solar energy is focused to be incident upon the exchanger tube to superheat a gas or gas mixture flowing through the tube. The heated gas can be used in various gas reaction processes, such as steam methane reformation, a reverse water-gas shift reaction, or to drive a heat engine. Various auxiliary features are disclosed for increasing the efficiency of the solar heat transfer into the flowing process gas.

1 . An apparatus for solar heating a feed gas comprising:
 a heat exchanger comprising:
 an envelope substantially in the shape of a hollow cone having a vertex and a base, the base being open to a substantially circular aperture, the envelope comprising a reflective interior surface; 
 at least one tube wound in a conical spiral within the envelope and proximate to the interior surface; and 
   a collector for reflectively directing solar energy toward the heat exchanger and through the aperture to heat the at least one tube;   
     wherein a feed gas flows through the tube to be heated thereby. 
   
   
       2 . An apparatus according to  claim 1  wherein the at least one tube comprises an outer port at a first tube end and an inner port at a second tube end, via which ports the feed gas enters and exits the tube. 
   
   
       3 . An apparatus according to  claim 2  wherein the outer port is disposed proximately to the aperture and the inner port is disposed between the aperture and the envelope vertex. 
   
   
       4 . An apparatus according to  claim 3  further comprising a pump which moves gas in the tube from the outer port toward the inner port. 
   
   
       5 . An apparatus according to  claim 3  further comprising a pump which moves gas in the tube from the inner port toward the outer port. 
   
   
       6 . An apparatus according to  claim 2  wherein the tube comprises a nickel superalloy. 
   
   
       7 . An apparatus according to  claim 2  further comprising a convective insert disposed within the tube. 
   
   
       8 . An apparatus according to  claim 2  wherein the at least one tube comprises a plurality of tubes, and further comprising a manifold for providing parallel gas flow into the plurality of tubes. 
   
   
       9 . An apparatus according to  claim 1  further comprising a beam spreader, disposed proximately to the envelope vertex, for reflectively directing solar energy toward the at least one tube. 
   
   
       10 . An apparatus according to  claim 9  wherein the beam spreader is substantially in the shape of a cone disposed coaxially with the envelope and having its base in confronting relation to the envelope vertex. 
   
   
       11 . An apparatus according to  claim 9  wherein the beam spreader comprises a nickel superalloy. 
   
   
       12 . An apparatus according to  claim 9  further comprising means for cooling the beam spreader. 
   
   
       13 . An apparatus according to  claim 1  further comprising a shroud disposed around the envelope aperture the shroud comprising a reflective interior surface for reflecting solar energy toward the at least one tube.