Indirect Water Heater

Abstract

An example indirect water heater is disclosed having a water storage tank with a primary heat exchanger. A heating fluid inlet of the primary heat exchanger receives a heating fluid from an external heat source into the primary heat exchanger. A heating fluid outlet of the primary heat exchanger returns the heating fluid to the external heat source after traveling through the primary heat exchanger. A secondary heat exchanger has a water source inlet and a water source outlet. The secondary heat exchanger is provided in thermal connection with the primary heater exchanger to preheat a source water before discharging the source water from the water source outlet into the water storage tank.

1 . An indirect water heater, comprising:
 a water storage tank;   a primary heat exchanger in the water storage tank;   a heating fluid inlet of the primary heat exchanger for receiving a heating fluid from an external heat source into the primary heat exchanger;   a heating fluid outlet of the primary heat exchanger for returning the heating fluid to the external heat source after traveling through the primary heat exchanger;   a secondary heat exchanger having a water source inlet and a water source outlet, the secondary heat exchanger provided in thermal connection with the primary heater exchanger to preheat a source water before discharging the source water from the water source outlet into the water storage tank; and   an insulated tank bladder forming the secondary heat exchanger.   
     
     
         2 . The indirect water heater of  claim 1 , further comprising channels formed within the insulated tank bladder. 
     
     
         3 . The indirect water heater of  claim 1 , wherein the secondary heat exchanger is a single coiled tube in the insulated tank bladder. 
     
     
         4 . The indirect water heater of  claim 1 , wherein the insulated tank bladder forms a chamber at the bottom of the water storage tank. 
     
     
         5 . The indirect water heater of  claim 1 , wherein the insulated tank bladder forms a thermal break between two chambers of the water storage tank. 
     
     
         6 . The indirect water heater of  claim 5 , wherein a portion of the primary heat exchanger passes into a lower chamber and coils form from the center outward in increasing concentric loops toward an outer wall of the water storage tank. 
     
     
         7 . The indirect water heater of  claim 6 , wherein the secondary heat exchanger discharges preheated source water through a port at the outer wall of the water storage tank in the lower chamber. 
     
     
         8 . The indirect water heater of  claim 7 , further comprising a vertical strip of channel material between loops of the secondary heat exchanger in the lower chamber form a channel for the source water to flow along a length of the secondary heat exchanger. 
     
     
         9 . The indirect water heater of  claim 8 , wherein the channel concludes near an opening at a center of the insulated tank bladder where the preheated source water enters an upper chamber through the opening. 
     
     
         10 . An indirect water heater, comprising:
 a water storage tank;   a primary heat exchanger in the water storage tank;   a heating fluid inlet of the primary heat exchanger for receiving a heating fluid from an external heat source into the primary heat exchanger;   a heating fluid outlet of the primary heat exchanger for returning the heating fluid to the external heat source after traveling through the primary heat exchanger; and   a secondary heat exchanger having a water source inlet and a water source outlet, the secondary heat exchanger provided in thermal connection with the primary heater exchanger to preheat a source water before discharging the source water from the water source outlet into the water storage tank;   wherein the secondary heat exchanger is a single coiled tube in the insulated tank bladder.   
     
     
         11 . The indirect water heater of  claim 10 , further comprising:
 an insulated tank bladder forming the secondary heat exchanger; and   channels formed within the insulated tank bladder.   
     
     
         12 . The indirect water heater of  claim 10 , wherein the secondary heat exchanger is a single coiled tube in the insulated tank bladder. 
     
     
         13 . The indirect water heater of  claim 10 , wherein the insulated tank bladder forms a chamber at the bottom of the water storage tank. 
     
     
         14 . The indirect water heater of  claim 10 , wherein the insulated tank bladder forms a thermal break between two chambers of the water storage tank. 
     
     
         15 . The indirect water heater of  claim 14 , wherein a portion of the primary heat exchanger passes into a lower chamber and coils form from the center outward in increasing concentric loops toward an outer wall of the water storage tank. 
     
     
         16 . The indirect water heater of  claim 15 , wherein the secondary heat exchanger discharges preheated source water through a port at the outer wall of the water storage tank in the lower chamber. 
     
     
         17 . The indirect water heater of  claim 16 , further comprising a vertical strip of channel material between loops of the secondary heat exchanger in the lower chamber form a channel for the source water to flow along a length of the secondary heat exchanger. 
     
     
         18 . The indirect water heater of  claim 17 , wherein the channel concludes near an opening at a center of the insulated tank bladder where the preheated source water enters an upper chamber through the opening.