Double-wall heat exchanger

Abstract

An improved double-wall heat exchanger in which the safety “leak” space between heat exchange surfaces forming channels for the fluids exchanging heat is filled with a heat transfer medium with improved thermal conductivity in comparison to air. Pressure responsive rupture points allow release of the heat transfer medium and the heat exchange fluid in the event of failure of one of the containment surfaces. Metal-to-metal heat transfer points are dispersed in the gap to further enhance heat transfer between the hot and cold heat exchange fluid streams.

What is claimed is: 
     
         1 . A double-wall heat exchanger comprising:
 a first conduit for a first heat exchange fluid and having a heat transfer surface;   a second conduit for a second heat exchange fluid and having a heat transfer surface;   wherein the heat transfer surface of the first conduit and the heat transfer surface of the second conduit together define a heat transfer space bounded by a perimeter; and   wherein the heat transfer space is occupied by a thermally conductive medium.   
     
     
         2 . The double-wall heat exchanger of  claim 1  wherein the heat exchanger is a plate heat exchanger. 
     
     
         3 . The double-wall heat exchanger of  claim 1  wherein the heat exchanger is a tube-in-tube heat exchanger. 
     
     
         4 . The double-wall heat exchanger of  claim 1  wherein the perimeter of the heat transfer space includes a rupture point configured to permit release of thermally conductive medium if the internal pressure of the heat transfer space exceeds a predetermined level. 
     
     
         5 . The double-wall heat exchanger of  claim 4  wherein the heat exchanger comprises a plurality of solid heat transfer contacts providing surface-to-surface heat transfer connections between the heat transfer surface of the first conduit and the heat transfer surface of the second conduit. 
     
     
         6 . The double-wall heat exchanger of  claim 1  wherein the thermal conductivity of the thermally conductive medium exceeds 0.134 W/(m K) at 288K temperature. 
     
     
         7 . The double-wall heat exchanger of  claim 1  wherein the heat exchanger comprises a plurality of solid heat transfer contacts providing surface-to-surface heat transfer connections between the heat transfer surface of the first conduit and the heat transfer surface of the second conduit. 
     
     
         8 . The double-wall heat exchanger of  claim 7  wherein the solid heat transfer contacts are formed of wire mesh or foam filling the heat transfer space. 
     
     
         9 . The double-wall heat exchanger of  claim 1  wherein the thermally conductive medium is a single phase medium. 
     
     
         10 . The double-wall heat exchanger of  claim 1  wherein the thermally conductive medium is a phase change medium. 
     
     
         11 . The double-wall heat exchanger of  claim 1  wherein the thermally conductive medium comprises a nano-fluid. 
     
     
         12 . The double-wall heat exchanger of  claim 11  wherein the nanoparticles in the nano-fluid include metal particles having a thermal conductivity greater than 6.6 W/(m K) at 288K temperature.