Indirectly Heated, Storage Water Heater System

Abstract

A system is shown for providing domestic hot water for potable use. The energy source is a steam powered heat exchanger. Water is heated in a heat engine package including the heat exchanger, a temperature operated pump and a condensate control valve. The heat package works in conjunction with a water storage package including a water storage tank and an electronic controller which controls the operation of the pump and condensate control valve. The electronic controller is operated so that the control of steam supplied to the system and flow of water through the heat exchanger ensures that steam is only present in the heat exchanger when there is a predetermined high flow rate of water.

What is claimed is: 
     
         1 . A system for providing potable, domestic hot water using an indirectly heated, storage water heater system, the system comprising:
 a heat engine package comprising a steam operated heat exchanger, a temperature operated pump and a condensate control valve;   a storage package including a water storage tank with an internal temperature sensor, the water storage tank being located apart from but plumbed to the steam operated heat exchanger, and an electronic controller operatively associated with the temperature sensor in the water storage tank, the temperature operated pump, and the condensate control valve to control the supply of steam to the heat exchanger and the discharge of condensate therefrom, as well as the flow of hot and cold water to and from the water storage tank;   wherein the water storage tank has an interior, a cold water inlet and a cold water circulation outlet connected by a conduit to one side of the heat exchanger, a hot water circulation return inlet for communication with the heat exchanger for directing an inlet stream of hot water from the steam operated heat exchanger back into the storage tank interior, and a hot water outlet, and wherein a diffuser nozzle is located within the tank interior at both the cold water inlet and the hot water circulation return inlet to reduce velocity and directionality of the inlet stream of hot water being introduced into the tank interior from the heat exchanger;   wherein the electronic controller is operated so that the control of steam supplied to the system and flow of water through the heat exchanger ensures that steam is only present in the heat exchanger when there is a predetermined high flow rate of water.   
     
     
         2 . The system of  claim 1 , wherein the presence of the diffuser nozzles at the cold water inlet and the hot water circulation return inlet pull relatively coldest water from a bottom region of the tank interior with the water being reintroduced to the tank interior from the hot water circulation return inlet at a higher relative location, the diffuser nozzles directing the flow of water outward and downward, thereby minimizing any disturbance of heated water in a top region of the tank. 
     
     
         3 . The system of  claim 2 , wherein the heat exchanger is a shell and tube heat exchanger with a shell side and a tube side, with relatively cooler water to be heated being passed on a selected one of the shell and tube side of the heat exchanger and steam being passed on a remaining side of the heat exchanger, the steam being supplied from a suitable steam source; 
     
     
         4 . The system of  claim 3 , wherein the diffuser nozzles are mounted on an exterior surface of the water storage tank by a bolt on flange fitting which facilitates ease of maintenance and cleaning of the tank interior and diffuser nozzles. 
     
     
         5 . The system of  claim 3 , wherein the presence of the diffuser nozzles prevents disturbing a naturally occurring stratification of heat, providing a more uniform tank temperature as well as ensuring the heat exchanger is provided with the coldest inlet water, thereby increasing the efficiency of the system. 
     
     
         6 . A method for providing potable, domestic hot water to an end user, using an indirectly heated, storage water heater system, the method comprising the steps of:
 providing a heat engine package comprising a steam operated heat exchanger, a temperature operated circulating pump and a condensate control valve;   providing a storage package including a water storage tank with an internal temperature sensor, the water storage tank being located apart from but plumbed to the steam operated heat exchanger, and an electronic controller operatively associated with the temperature sensor in the water storage tank, the temperature operated pump, and the condensate control valve to control the supply of steam to the heat exchanger and the discharge of condensate therefrom, as well as the flow of hot and cold water to and from the water storage tank;   wherein the water storage tank has an interior, a cold water inlet and a cold water circulation outlet connected by a conduit to one side of the heat exchanger, a hot water circulation return inlet for communicating with the heat exchanger for directing an inlet stream of hot water from the steam operated heat exchanger back into the storage tank interior, and a hot water outlet, and wherein a diffuser nozzle is located within the tank interior at both the cold water inlet and the hot water circulation return inlet to reduce velocity and directionality of the inlet streams of water being introduced into the tank interior;   wherein the electronic controller is operated so that the control of steam supplied to the system and flow of water through the heat exchanger ensures that steam is only present in the heat exchanger when there is a predetermined high flow rate of water.   
     
     
         7 . The method of  claim 6 , wherein in an initial state, the heat exchanger, water storage tank and associated plumbing are at ambient or ground water temperatures and wherein the system is first subjected to a startup cycle in which power is applied to power the system and provide a control signal for the water heating system's operation. 
     
     
         8 . The method of  claim 7 , wherein once it has been determined that the system is full of potable water and air has been removed from the water storage tank, steam is then be supplied to the heat engine. 
     
     
         9 . The method of  claim 8 , wherein when power is supplied to the electronic controller, a temperature sensor associated with the controller senses that water in the water storage tank is below a given set point, the electronic controller then supplies power to the temperature operated circulating pump and to the condensate control valve beginning circulation flow to the heat engine and opening the condensate control valve. 
     
     
         10 . The method of  claim 9 , wherein the heat exchanger is a shell and tube heat exchanger with a shell side and a tube side, with relatively cooler water to be heated being passed on a selected one of the shell and tube side of the heat exchanger and steam being passed on a remaining side of the heat exchanger, the steam being supplied from a suitable steam source. 
     
     
         11 . The method of  claim 10 , wherein water is then circulated at a predetermined flow rate to the heat exchanger to extract latent heat from the steam being supplied to the heat exchanger, while also providing a relatively small degree of sub-cooling, thereby causing a flow of condensate on the steam side of the heat exchanger while drawing more steam through the system. 
     
     
         12 . The method of  claim 11 , wherein circulating water returns to the water storage tank interior through the hot water circulation return inlet and diffuser nozzle, causing the temperature of water in the water storage tank to rise. 
     
     
         13 . The method of  claim 12 , wherein the user of the diffuser nozzle on the hot water circulation return inlet causes stored water to fill from the top of the water storage tank until and temperature sensor located in the tank interior reaches a desired set point, and wherein once the desired set point is reached, the electronic controller immediately removes power from the condensate control valve as the circulating pump continues to run on a time delay shutoff. 
     
     
         14 . The method of  claim 13 , wherein the heat exchanger has internal heating surfaces, and wherein continued running of the circulating pump causes the heat exchanger to flood with condensate until all heating surfaces are in contact with the condensate, the condensate then being cooled below the point of scale formation, and wherein once the predetermined time delay has been reached, power is removed from the circulating pump and the system is in a standby state. 
     
     
         15 . The method of  claim 14 , wherein as supplied domestic potable water is used, cold water flows into the water storage tank interior through the cold water inlet diffuser, the relatively colder water entering the diffuser causing water to fill the tank from a bottom region toward a top region. 
     
     
         16 . The method of  claim 15 , whereby, when the level of cold water in the tank reaches a location of the electronic controller temperature sensor, the electronic controller will provide power to the circulating pump and condensate control valve, beginning the heating cycle again.