# US 5,347,957 A · Water heater with reduced NO.sub.x output

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- Number: US 5,347,957 A
- Document ID: US5347957A
- Status: Granted
- Kind: A
- Application number: 07/919,098
- Filed: 1992-07-23
- Granted: 1994-09-20
- Earliest claimed: 1991-07-26
- Assignees: Tokyo Gas Co., Ltd.
- Inventors: Tatsuya Sugahara
- Web page: https://patentgrep.com/patent/US5347957A

## CPC

- F24H 1/40: with water tube or tubes
- F23M 9/10: Baffles or deflectors formed as tubes, e.g. in water-tube boilers
- F24H: FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL (steam generation F22)
- F23M: CASINGS, LININGS, WALLS OR DOORS SPECIALLY ADAPTED FOR COMBUSTION CHAMBERS, e.g. FIREBRIDGES; DEVICES FOR DEFLECTING AIR, FLAMES OR COMBUSTION PRODUCTS IN COMBUSTION CHAMBERS; SAFETY ARRANGEMENTS SPECIALLY ADAPTED FOR COMBUSTION APPARATUS; DETAILS OF COMBUSTION CHAMBERS, NOT OTHERWISE PROVIDED FOR

## Abstract

A water heater with reduced nitrogen oxides output utilizing NO.sub.x reducing water conduits to cool a laminar flame and thereby reduce production of nitrogen oxides, The water heater has a partially aerated burner using a partially premixed combustion method to produce the laminar flame wherein a plurality of NO.sub.x reducing water conduits are disposed above the partially aerated burner in such a manner that water is supplied from a cold water conduit or a hot water conduit of the water heater into the plurality of NO.sub.x reducing water conduits through a water introducing portion by means of branching or serial connections. The water absorbs heat while flowing through the plurality of NO.sub.x reducing water conduits and is returned to the cold water conduit or the hot water conduit through a water receiving portion by means of and branching or serial connections.

## Claims

### Claim 1

A water heater with reduced nitrogen oxides output, having a partially aerated burner producing a laminar flame using partially premixed combustion constituents above a plurality of serially aligned flame ports, comprising:
a plurality of NO.sub.x reducing water conduits disposed at a downstream side of said partially aerated burner in such a manner that one of cold water or hot water is supplied from one of cold water conduit or hot water conduit of said water heater into said plurality of NO.sub.x reducing water conduits by means of a water introducing portion through one of a branching connection or a serial connection; and
said one of said hot water or said cold water being heated by absorbing heat through said plurality of NO.sub.x reducing water conduits and returned to said cold water conduit or said hot water conduit through a water receiving portion.

### Claim 2 (depends on 1)

A water heater with reduced nitrogen oxides output as claimed in claim 1 wherein said water introducing portion is formed such that a part of a water flow in said cold water conduit is introduced into said plurality of NO.sub.x reducing water conduits and then fed therefrom into said hot water conduit.

### Claim 3 (depends on 1)

A water heater with reduced nitrogen oxides output as claimed in claim 1 wherein said water introducing portion is formed such that all water flowing in said cold water conduit is introduced into said plurality of NO.sub.x reducing water conduits and then fed therefrom to return to said cold water conduit.

### Claim 4 (depends on 1)

A water heater with reduced nitrogen oxides output as claimed in claim 1 wherein said water introducing portion is formed such that a part of a water flow in said cold water conduit is introduced into said plurality of NO.sub.x reducing water conduits and then fed therefrom to return to said cold water conduit.

### Claim 5 (depends on 1)

A water heater with reduced nitrogen oxides output as claimed in claim 1 wherein said water introducing portion is formed such that all of water flowing in said hot water conduit is introduced into said plurality of NO.sub.x reducing water conduits and then fed therefrom to return to said hot water conduit.

### Claim 6 (depends on 1)

A water heater with reduced nitrogen oxides output as claimed in claim 1 wherein said water introducing portion is formed such that a part of a water flow in said hot water conduit is introduced into said plurality of NO.sub.x reducing water conduits and then fed therefrom to return to said hot water conduit.

### Claim 7 (depends on 1)

A water heater with reduced nitrogen oxides output as claimed in claim 1 wherein:
said NO.sub.x reducing water conduits are disposed in an appropriate positional range;
a distance "H" is the distance between said NO.sub.x reducing water conduits and the surface of said burner ports;
a distance "W" is the width of a burner port surface:
said appropriate positional range is defined by the formula
0<H.ltoreq.5W
such that said NO.sub.x reducing water conduits are located between burner ports and an area of the highest flame temperature in said laminar flame formed at the downstream side of said burner ports; and
heat is removed from said laminar flame by means of heat absorption by said NO.sub.x reducing water conduits, thereby lowering the temperature of said laminar flame in the said highest flame temperature area at the downstream side of said NO.sub.x reducing conduits.

### Claim 8 (depends on 7)

A water heater with reduced nitrogen oxides output as claimed in claim 7 wherein:
said NO.sub.x reducing water conduits have a diameter "d" restricted to the range represented by the formula
d.ltoreq.W,
such that an output of nitrogen oxides is thereby reduced and at the same time an output of carbon monoxide is thereby restricted.

### Claim 9 (depends on 8)

A water heater with reduced nitrogen oxides output as claimed in claim 8 wherein said partially aerated burner has burners each provided with a single NO.sub.x reducing water conduit superposed right above the burner port surfaces of said partially aerated burner.

### Claim 10 (depends on 8)

A water heater with reduced nitrogen oxides output as claimed in claim 8 wherein:
said partially aerated burner has burners each provided with a pair of NO.sub.x reducing water conduits superposed right above the surface of the ports of said burner so as to be laterally parallel to each other with a space therebetween having the distance "S"; and
said distance being in the range represented by the formula
0<S.ltoreq.W.

### Claim 11

A water heater comprising:
a burner;
a cold water conduit having a cold water inlet;
a hot water conduit having a hot water outlet;
a water distribution manifold disposed at one side above said burner and communicated with a water flow passage from said cold water inlet to said hot water outlet;
said water distribution manifold being communicated to said water flow passage by means of a water introducing portion;
a water collection manifold disposed at the other side above said burner and communicated by means of a water receiving portion to said water flow passage;
a plurality of NO.sub.x reducing water conduits connected between said water distribution manifold and said water collection manifold and disposed above said burner; and
an outer and inner diameter of each of said plurality of NO.sub.x reducing water conduits being smaller than that of said cold water conduit and of said hot water conduit.

### Claim 12 (depends on 11)

A water heater as claimed in claim 11 wherein a feeding direction in said water collection manifold is contrary to an introducing direction in said water distribution manifold.

### Claim 13 (depends on 11)

A water heater as claimed in claim 11 wherein said water introducing portion and said water receiving portion are communicated with said hot water conduit.

### Claim 14 (depends on 11)

A water heater as claimed in claim 11 wherein said water introducing portion and said water receiving portion are communicated with said cold water conduit.

### Claim 15 (depends on 11)

A water heater as claimed in claim 11 wherein said water introducing portion is communicated with said cold water conduit, while said water receiving portion is communicated with said hot water conduit.