Water heater with integrated sorption reactor

Abstract

A water heater is provided having a sorption based reactor that is integrated into a water tank. The water heater is operated between an adsorption cycle and a desorption cycle. During the endothermic desorption cycle, a primary heat exchanger is used to transfer heat from a condensing primary fluid that was vaporized from the sorbate to water in the tank. A secondary heat transfer system uses a secondary fluid to supply heat for such vaporization during the endothermic desorption cycle. During the exothermic adsorption cycle, a secondary heat exchanger is used along with the secondary fluid to transfer heat generated by adsorption of the primary fluid to water in the tank. An evaporator provides for vaporization of the primary fluid during the adsorption cycle. Substantial improvements in energy efficiency can be achieved.

What is claimed is: 
     
         1 . A water heater, comprising:
 a tank having a volume for storing water, the tank also defining a cavity;   a primary fluid;   a primary heat transfer system in which the primary fluid is recirculated, the primary heat transfer system comprising
 a reactor located within the cavity; 
 a sorbate located within the reactor; 
 a primary heat exchanger positioned within the volume of the tank and in fluid communication with the reactor to receive vaporized primary fluid that is endothermically desorbed from the sorbate; 
 an evaporator in fluid communication with the primary heat exchanger to receive primary fluid condensed in the primary heat exchanger, the evaporator also in fluid communication with the reactor to provide primary fluid vaporized by the evaporator to the reactor; 
   a secondary fluid;   a secondary heat transfer system in which the secondary fluid is recirculated, the secondary heat transfer system comprising
 a heater configured for vaporizing the secondary fluid; 
 a reactor heat exchanger positioned within the reactor and in fluid communication with the heater to receive vaporized secondary fluid from the heater; 
 a secondary heat exchanger positioned within the volume of the tank for transferring heat to the water in the tank, the secondary heat exchanger in fluid communication with the reactor heat exchanger for receiving liquid secondary fluid that is heated by exothermic adsorption of primary fluid by the sorbate, the secondary heat exchanger also in fluid communication with the reactor heat exchanger to return liquid secondary fluid to the reactor heat exchanger after liquid secondary fluid has transferred heat to the water in the tank. 
   
     
     
         2 . The water heater of  claim 1 , wherein the tank defines a bottom and a top, and wherein the cavity is located in the bottom of the tank. 
     
     
         3 . The water heater of  claim 1 , wherein the secondary heat transfer system further comprises a secondary storage vessel in fluid communication with the reactor heat exchanger to receive liquid secondary fluid from the reactor heat exchanger. 
     
     
         4 . The water heater of  claim 3 , wherein the secondary heat transfer system further comprises a secondary pump having a secondary pump inlet configured for receiving secondary fluid from the secondary storage vessel, the secondary pump also having a secondary pump outlet configured for providing a flow of secondary fluid through the secondary heat exchanger. 
     
     
         5 . The water heater of  claim 4 , wherein the secondary heat transfer system further comprises a secondary valve configured for selectively controlling the flow of secondary fluid between the secondary storage vessel and the secondary heat exchanger. 
     
     
         6 . The water heater of  claim 5 , wherein the secondary valve is positioned in a flow of secondary fluid that is between the secondary heat exchanger and the secondary pump. 
     
     
         7 . The water heater of  claim 3 , wherein the reactor heat exchanger comprising a first leg having a top portion and a bottom portion, the bottom portion of the first leg in fluid communication with the heater to receive vaporized secondary fluid from the heater. 
     
     
         8 . The water heater of  claim 7 , wherein the reactor heat exchanger includes a second leg having a top portion and a bottom portion, the bottom portion of the second leg in fluid communication with the secondary storage vessel. 
     
     
         9 . The water heater of  claim 8 , wherein the first leg and the second leg are fluidly connected by a crossover extending between the first leg and the second leg, the crossover positioned along the second leg at a location that causes fluid to transfer over to the first leg once a predetermined amount of liquid has filled the secondary storage vessel. 
     
     
         10 . The water heater of  claim 9 , further comprising a fluid riser in fluid communication with the secondary heat exchanger, the fluid riser extending within the first leg and having a fluid outlet near the top portion of the first leg for the outflow of secondary fluid received from the secondary heat exchanger. 
     
     
         11 . The water heater of  claim 8 , further comprising a fluid riser in fluid communication with the secondary heat exchanger, the fluid riser extending within the first leg and having a fluid outlet near the top portion of the first leg for the outflow of secondary fluid received from the secondary heat exchanger. 
     
     
         12 . The water heater of  claim 1 , wherein the heater comprises:
 a fuel burner; and   a boiler for receiving heat from the fuel burner and vaporizing the secondary fluid.   
     
     
         13 . The water heater of  claim 12 , further comprising:
 an exhaust gas heat exchanger positioned in the volume of the tank and configured to heat the water in the tank using exhaust gas from the fuel burner; and   a vent that receives exhaust from the fuel burner and supplies the exhaust to the exhaust gas heat exchanger.   
     
     
         14 . The water heater of  claim 1 , wherein the primary heat transfer system further comprises a primary storage vessel in fluid communication with the primary heat exchanger to receive condensed primary fluid from the primary heat exchanger. 
     
     
         15 . The water heater of  claim 14 , wherein the primary storage vessel is also in fluid communication with the evaporator to receive liquid primary fluid from the evaporator. 
     
     
         16 . The water heater of  claim 14 , wherein the evaporator is positioned at a non-zero angle from horizontal and higher than the primary storage vessel so as cause condensed primary fluid to drain from the evaporator into the primary storage vessel. 
     
     
         17 . The water heater of  claim 14 , further comprising a primary pump having a primary pump inlet configured for receiving primary fluid from the primary storage vessel, the primary pump also having a primary pump outlet configured for providing a flow of primary fluid to the evaporator. 
     
     
         18 . The water heater of  claim 17 , wherein the primary heat transfer system further comprises a primary valve for selectively controlling the flow of primary fluid between the reactor and the evaporator. 
     
     
         19 . The water heater of  claim 1 , wherein the evaporator is positioned at a vertical location that is lower than the primary heat exchanger such that condensed primary fluid from the primary heat exchanger flows under force of gravity to the evaporator.