Enhanced Pool Boiling System and Method

Abstract

A boiling heat exchange system includes a heat exchanger including a chamber configured to hold a heat exchange fluid including a heat exchange vapor and a pool of heat exchange liquid and an evaporator tube having an outer surface and a thermally conductive open-cell porous material disposed on the outer surface and comprising a plurality of pores. The evaporator tube can be immersed in the heat exchange liquid held in the chamber and the heat exchange liquid will enter the pores. The open-cells of the open-cell porous material will heat the heat exchange liquid to cause the heat exchange liquid to boil to a heat exchange vapor and exchange heat with a source fluid flowing through the evaporator tube or with a component in thermal contact with the evaporator. A method of performing heat exchange is also disclosed.

We claim: 
     
         1 . A boiling heat exchange system, comprising:
 a heat exchanger comprising:
 i) a chamber configured to hold a heat exchange fluid including a heat exchange vapor and a pool of heat exchange liquid; and, 
 ii) an evaporator tube having a wall with an inner surface and an outer surface, wherein the evaporator tube has an input end and an opposite, output end and a thermally conductive open-cell porous material disposed on the outer surface and comprising a plurality of pores, wherein at least a portion of the evaporator tube can be immersed in the heat exchange liquid held in the chamber and heat exchange liquid will enter the pores and open-cells of the open-cell porous material, and wherein the evaporator tube is configured to receive, at the input end, a source fluid to be cooled from a first temperature to a second temperature each higher than a boiling temperature of the heat exchange liquid, guide the source fluid from the input end through the evaporator tube to the output end, wherein when the evaporator tube is immersed in the pool of heat exchange liquid and source fluid is moved through the evaporator tube, heat from the source fluid will pass through the wall and the thermally conductive open-cell porous material to cause the heat exchange liquid within the open-cells to boil to a heat exchange vapor, and the heat exchange vapor will move through the open cells of the thermally conductive porous material and will be replaced in the open-cells by more heat exchange liquid. 
   
     
     
         2 . The system of  claim 1 , further comprising a condensing system for condensing the heat exchange vapor to a heat exchange liquid and returning the heat exchange liquid to the pool of refrigerant liquid. 
     
     
         3 . The system of  claim 2 , wherein the chamber comprises a heat exchange vapor outlet to release heat exchange vapor and a heat exchange liquid inlet to receive heat exchange liquid; and the condensing system comprises a condensing heat exchanger to receive the heat exchange vapor from the chamber, condense the heat exchange vapor to the heat exchange liquid, and return the heat exchange liquid to the pool of heat exchange liquid in the chamber. 
     
     
         4 . The system of  claim 1 , wherein the thermally conductive open-cell porous material comprises a foam of a conductive material. 
     
     
         5 . The system of  claim 4 , wherein the thermally conductive open-cell porous material comprises at least one selected from the group consisting of metal, graphite, or carbon foams. 
     
     
         6 . The system of  claim 5 , wherein the metal foam comprises at least one selected from the group consisting of Cu, Al, or Fe, and alloys thereof. 
     
     
         7 . The system of  claim 4 , wherein the open cells have pore openings between cells, the pore size of the pore openings being from 0.1 μm to 100 mm. 
     
     
         8 . The system of  claim 7 , wherein the cell diameter of the open cells increases from a first size proximate to the evaporator tube to a second size greater than the first size distal to the evaporator. 
     
     
         9 . The system of  claim 5 , wherein the foam has a porosity in a range of 40%-99%. 
     
     
         10 . The system of  claim 5 , wherein the foam has a pore density in a range of 5-100 pores per inch (PPI). 
     
     
         11 . The system of  claim 4 , wherein the open cells of the thermally conductive open-cell porous material have a cell diameter of from 1 μm to 10 mm. 
     
     
         12 . The system of  claim 1 , wherein the thermally conductive open cell porous material is provided as a layer surrounding the evaporator tube. 
     
     
         13 . The system of  claim 12 , wherein the layer of thermally conductive porous material has a thickness in a range of 10%-100% of an outer radius of the evaporator tube. 
     
     
         14 . The system of  claim 1 , further comprising a plurality of evaporator tubes embedded in a matrix of the thermally conductive open-cell porous material. 
     
     
         15 . The system of  claim 1 , further comprising a coating to change the surface morphology on the layer of thermally conductive porous material. 
     
     
         16 . The system of  claim 1 , wherein the heat exchange fluid comprises water. 
     
     
         17 . A method of conducting heat exchange, comprising the steps of:
 providing a heat exchanger comprising:
 i) a chamber configured to hold heat exchange fluid including heat exchange vapor and a pool of heat exchange liquid; 
 iii) An evaporator tube having a wall with an inner surface and an outer surface, wherein the evaporator tube has an input end and an opposite, output end, and a layer of thermally conductive open-cell porous material disposed on the outer surface and comprising a plurality of pores, wherein at least a portion of the evaporator tube can be immersed in the heat exchange liquid held in the chamber, and wherein the evaporator tube is configured to receive, at the input end, a source fluid to be cooled from a first temperature to a second temperature each higher than a boiling temperature of the heat exchange liquid, guide the source fluid from the input end through the evaporator tube to the output end; 
   providing a pool of heat exchange liquid in the chamber such that the evaporator tube is immersed in the heat exchange liquid, and heat exchange liquid will enter the pores and the open-cells of the thermally conductive porous material;   directing the source fluid at the first temperature through the evaporator, the source fluid exiting the evaporator tube at the second temperature, the source fluid exchanging heat with the evaporator tube, the thermally conductive open-cell porous material, and thereby with the heat exchange liquid within the pores of the thermally conductive open-cell porous material, whereby the heat exchange liquid will change state to a heat exchange vapor and the heat exchange vapor will move through the open-cells of the thermally conductive open-cell porous material and will be replaced by heat exchange liquid.   
     
     
         18 . The method of  claim 17 , wherein the heat exchange vapor contacts and releases heat to a condensing system, and is transformed from heat exchange vapor to heat exchange liquid and the heat exchange liquid is returned to the pool of heat exchange liquid. 
     
     
         19 . A method of heating a fluid, comprising the steps of:
 providing a heat exchange tube, comprising a heat exchange wall with an inner surface and an outer surface for separating a first heat exchange fluid from a second heat exchange fluid, the first heat exchange fluid moving in a flow direction relative to the inner surface of the wall, the heat exchange tube comprising a layer of thermally conductive open-cell porous metal foam having a plurality of pores, the thermally conductive porous metal foam being disposed on the outer surface of the tube; and,   flowing the first heat exchange fluid through the heat exchange tube while permitting the second heat exchange fluid to penetrate the pores of the thermally conductive open-cell porous metal foam, wherein the first heat exchange fluid exchanges heat with the second heat exchange fluid.   
     
     
         20 . The method of  claim 19 , wherein the thermally conductive open-cell porous metal foam comprises open cells having a cell diameter, and wherein the cell diameter of the open cells increases from a first size proximate to the wall to a second size greater than the first size distal to the wall. 
     
     
         21 . The method of  claim 19 , wherein the thermally conductive open-cell porous material comprises open cells having a cell diameter, and the cell diameter of the open cells increases from a first size at an upstream location relative to the flow direction to a second size less than the first size downstream relative to the flow direction. 
     
     
         22 . A component heat exchange system, comprising:
 a heat exchanger comprising a chamber and an evaporator tube, the chamber being configured to hold a heat exchange fluid including a heat exchange vapor and a pool of heat exchange liquid;   the evaporator tube having an outer surface and comprising thermally conductive open-cell porous material disposed on the outer surface and having a plurality of pores;   at least a portion of the evaporator tube being immersed in the heat exchange liquid held in the chamber such that heat exchange liquid will enter the pores and open-cells of the thermally conductive open-cell porous material;   wherein the evaporator tube is thermally connected by a thermal connection to the component such that heat is transferred from the component to the evaporator tube; the temperature of the evaporator tube being higher than a boiling temperature of the heat exchange liquid, wherein heat from the component will pass through the wall and the thermally conductive open-cell porous material to cause the heat exchange liquid within the thermally conductive open-cells to boil to a heat exchange vapor, and the heat exchange vapor will move through the open cells of the thermally conductive porous material and will be replaced in the open cells by more heat exchange liquid which will then also evaporate.   
     
     
         23 . The component heat exchange system of  claim 22 , wherein the component comprises at least one selected from the group consisting of an electrical component, a mechanical component, a chemical reactor component, and a nuclear reactor component. 
     
     
         24 . The component heat exchange system of  claim 23 , wherein the electrical component comprises a processor. 
     
     
         25 . The component heat exchange system of  claim 23 , wherein the mechanical component comprises an internal combustion engine.