Gas fired water heater

A gas fired water heater system for supplying water on demand at a substantially constant, controlled temperature, comprising:

• combustion means for igniting a combustible mixture of air and gas to provide a fluid for heating said water;
• heat exchanger means for providing heat transfer between the fluid and the water, said exchanger means including a hollow cylindrical combustion chamber open at its bottom to receive the fluid from said combustion means, a water chamber enclosing the combustion chamber and having an outer shell defining a water channel between the shell and said combustion chamber, said water chamber having an inlet for admitting incoming relatively cool water into the channel and an outlet for withdrawing outgoing relatively hot water from the channel after heat transfer, a plurality of exchange tubes formed through, extending from and surrounding said combustion chamber forming a conduit for the fluid to pass in physical isolation from and in heat exchange relation with the water passing through the water channel such that the fluid travels upwards through the combustion chamber and downwards through the tubes in counterflow to the water travelling upwards through the water channel, said water and fluid being at different temperatures such that a temperature gradient is established in the water in the direction of its flow and that the fluid is cooled in traversing, downwards through the tubes, the water below the dew point of the fluid causing the vapor in the fluid to condense;
• temperature control means for controlling the temperature of the water, including thermal measuring means having a sensor for sensing the temperature of a mixture of a sample portion of said incoming water and a sample portion of said outgoing water, said thermal measuring means including flow means for creating a pressure differential between the incoming and outgoing sample portions that depends on the rate of flow of the water in such a way that the relative ratio of the sample portions depends generally linearly on the flow rate of the water, and including controlling means responsive to the sensed temperature for modulating the flow of air and gas to said combustion means.

A direct fired water heater system having combustion means for igniting a combustible mixture of air and gas to provide a first fluid for heating a second fluid, heat exchanger means for providing heat transfer between said first and second fluids, said heat exchanger including a combustion chamber for receiving the first fluid and a water chamber enclosing the combustion chamber, and temperature control means for controlling the temperature of the fluids including thermal measuring means having a sensor for sensing the temperature of a mixture of incoming and outgoing portions of said second fluid and controlling means responsive to the sensed temperature for controlling the rate of heat transfer between the fluids, wherein

• said heat exchanger means further includes a plurality of substantially equally spaced apart exchange tubes formed through, extending from and surrounding said combustion chamber creating a conduit such that the first fluid travels upwards through the combustion chamber, downwards through the tubes in counterflow to the second fluid travelling upwards through the water chamber, wherein
• said fluids are at different temperatures such that a temperature gradient is established in the second fluid in the direction of its flow and that the first fluid is cooled in traversing, downwards through the tubes, the second fluid below the dew point of first fluid causing the vapor in the first fluid to condense, and wherein
• said controlling means controls the rate of heat transfer between the fluids by modulating the flow of air and gas to said combustion means.

A direct fired water heater system having combustion means for igniting a combustible mixture of air and gas to provide a first fluid for heating a second fluid, heat exchanger means for providing heat transfer between said first and second fluids, said heat exchanger including a combustion chamber for receiving the first fluid and a water chamber enclosing the combustion chamber, and temperature control means for controlling the temperature of the fluids including thermal measuring means having a sensor for sensing the temperature of a mixture of incoming and outgoing portions of said second fluid and controlling means responsive to the sensed temperature for controlling the rate of heat transfer between the fluids, wherein

• said thermal measuring means includes flow means for establishing a pressure differential between the incoming and outgoing portions depending on the flow rate of the second fluid such that a relative ratio of the portions depends linearly on the flow rate of the second fluid for flow rates, and wherein
• said flow means includes a plurality of orifice means to restrict the flow of said second fluid, hydraulic zero adjuster means for hydraulically pulling a first portion of said incoming second fluid so that said first portion bypasses one of the orifice means and said sensor, and pump means for pumping at a fixed rate a second portion of said second fluid, said second portion including said first portion.

A direct fired water heater system having combustion means for igniting a combustible mixture of air and gas to provide a first fluid for heating a second fluid, heat exchanger means for providing heat transfer between said first and second fluids, said heat exchanger including a combustion chamber for receiving the first fluid and a water chamber enclosing the combustion chamber, and temperature control means for controlling the temperature of the fluids including thermal measuring means having a sensor for sensing the temperature of a mixture of incoming and outgoing portions of said second fluid and controlling means responsive to the sensed temperature for controlling the rate of heat transfer between the fluids, wherein

• said controlling means includes signal means for generating a signal based upon the sensed temperature, and air/fuel means responsive to said signal for modulating the flow of air and gas to said combustion means, wherein said signal means includes feed forward means for subtracting the sensed temperature from the temperature of the outgoing portion of said second fluid, derivative means for calculating the rate of temperature change of said second fluid, feedback means for subtracting the temperature of the outgoing portion of said second fluid from a set point predetermined temperature, and summation means for generating said signal based upon the summation of the values generated by said feed forward means, derivative means and feedback means.

A direct fired water heater system having combustion means for igniting a combustible mixture of air and gas to provide a first fluid for heating a second fluid, heat exchanger means for providing heat transfer between said first and second fluids, said heat exchanger including a combustion chamber for receiving the first fluid and a water chamber enclosing the combustion chamber, and temperature control means for controlling the temperature of the fluids including thermal measuring means having a sensor for sensing the temperature of a mixture of incoming and outgoing portions of said second fluid and controlling means responsive to the sensed temperature for controlling the rate of heat transfer between the fluids, wherein

• said combustion means comprises a nozzle mix burner including a cylindrical air chamber enclosing an elongated gas pipe, said air chamber having an outer shell defining an air channel between said shell and gas pipe, through which air travels and exits at ports formed at the upper end of the chamber and at the periphery thereof, said gas pipe open at its bottom to receive gas from said controlling means and having a gas cap at its upper end with at least one gas port for the exit of gas, and wherein
• said air exit means includes air ports positioned at the shell of the air chamber, and wherein said gas pipe means has at least one gas tube extending radially outwards from the pipe means towards the outer shell, said tubes providing a conduit for the introduction of gas into an area just above the air ports positioned at the outer shell, and wherein
• said nozzle mix burner further comprises spinner vanes formed above said air ports positioned at the shell of the chamber in asymmetric relation with the radial gas tubes, said spinner vanes adapted to spin the mixture of air and gas at a very high velocity at the upper end of the chamber.