Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates generally to gas/oil fired
commercial and residential water heaters and specifically to a
gas/oil fired water heater having a replaceable submerged combus-
tion chamber assembly with curved fire tubes which is submergible
in the water heater tank.
In conventional gas/oil fired water heaters, hot gas
flows through a series of vertically mounted tubes which are
mounted in vertical fashion between top and bottom support plates
within the water heater tank. Water flows into and out of a
chamber located between the support plates and contacts and cir-
culates about the exterior of the vertical tubes to effect heat
transfer to heat the water.
Typical prior art gas/oil fired water heaters featured
non-pressurized external combustion chambers. The location of
the combustion chamber on the exterior of the water heater results
in lost heat and lower combustion efficiency. The tubes and sup-
port plates were not easily accessible and required disassembly
oE the entire tank for maintenance and replacement.
There has existed a need Eor a gas/oil fired water
heater design with a replaceable submerged combustion chamber
assembly which could be easily replaced if maintenance was required
without disassembly of the entire device.
There has also existed a need for a water heater design
which minimizes the internal stress on the submerged combustion
chamber fire tubes to provide longer operating life and reduced
maintenance requirements.
A need has also existed for a water heater with a sub-
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mergible, pressuxized combustion chamber so that all combustiontakes place in the water heater tank interior in a chamber sur-
rounded by water for virtually zero heat loss and increased
efficiency.
According to the present invention, there is provided
a gas or oil fired water heater, which comprises: a closed tank
normally containing water under pressure and having a top, a bottom,
a sidewall extending between said top and bottom, a water inlet,
a water outlet and an op~ning in said sidewall; a combustion
chamber assembly having a submergible, pressurized combustion
chamber portion with multiple external heating surfaces, said
combustion chamber portion normally extending through said side-
wall opening of said closed tank so that all of said heating sur-
faces are submerged in said water under pressure; said combustion
chamber assembly including means for readily removing same from
and installing same in said opening, said means comprising a
mounting portion for detachably but sealingly engaging said tank
opening; said combustion chamber portion comprising a substan
tially cylindrical body portion havin~ an open end located adjacent
said mounting portion which communicates with the exterior of
said water tank and a closed end at the opposite end of said body
portion; said multiple external heating surfaces including a
multiplicity of substantially U-shaped fire tubes of subs-tantially
smaller diameter than and spaced equidistantly about the en-tire
periphery of said body portion, each of said fire tubes having a
long leg and a short leg; said short leg of each of said fire
tubes extending through said closed end of said body portion to
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communicate with the interior of said combustion chamber portion
at said closed end; said long leg of each of said fire tubes
extending adjacent said body portion through said mounting por-
tion to the exterior of said water tank; a flue collector mounted
on the exterior of said water tank and having a flue opening there-
in which communicates with said open end of said body portion,
said flue collector having an annular chamber surrounding sai
flue opening and separated therefrom, said annular chamber com-
municating with said long leg of each of said fire -tubes, said
annular chamber having a flue outlet therein; and a :Eorced draft
burner mounted on the exterior of said water tank and communi-
cating with said combustion chamber opening for causing combus-
tion to take place within said body portion of said swbmergible,
pressurized combustion chamber portion so that substantially all
combustion -takes place within said water tank to minimize heat
loss.
The moun-ting portion may comprise a first mounting
flange connected to and extending about the periphery of the
open end of the combustion chamber body portion.
The invention will now be described in greater detail
wi.th reference
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to the accompanying drawings in which:
Figure 1 is a partial perspective view of the water heater of the
invention showing the parts in exploded fashion; and
Figure 2 is a side cross-sectional view to a reduced scale showing the
operation of the water heater of Figure 1.
Turning to Figure 1, there is shown a water heater of the present in-
vention designated generally as 11. The water heater 11 includes a water tank
13 of the type having a water inlet 15, a water outlet 17, and an opening 19 in
a sidewall 21 of the tank 13. Tank 13 can be of the conventional flanged and
dish design and have a top 25 ~shown broken away), and a bottom 23 which is
adapted to stand or be supported in vertical fashion on a support area 27. The
interior 29 of tank 13 is empty in the disassembled state sho~ in Figure 1 and
forms a water chamber for circulation of water passing into water inlet 15 and
out of water outlet 17.
A combustion chamber assembly designated generally as 31 in Figure 1
has a submergible portion which is adapted to be received within opening 19 in
tank 13. The submergible portion of the assembly includes a submergible com-
bustion chamber portion 33 adapted to be received within the tank opening 19.
Submergible combustion chamber portion 33 comprises a cylindrioal elongated
mcmber having an open end 35 and having an opposite closed end 37. The combus-
tion chamber assembly 31 also includes a mounting portion for detachably engag-
ing the tank opening 19 for mounting the assembly 31 within the tank. The mount-
ing portion can conveniently comprise a tube mounting flange 39 located adjace~t
and connected to ~he combustion chamber open end 35 as shown in Figure 1. The
tube mounting flange 39 is a ring like body having an opening in the central
part thereof which opening coincides with the opening in open end 35 of combus-
tion chamber 33. Flange 39 is securely affixed to chamber 33 as by welding or
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the like.
As seen in Figure 1, the combustion chamber assembly 31 also includes a
plurality of curved fire tubes 41 each of which has an end 43 which communicates
with combustion chamber 33 through closed end 37 ~see Figure 2) and which has an
opposite end 45 which extends through the opening 19 when in place on tank 13 to
the tank exterior. Each of curved tubes 41 is characterized in that at least a
a portion 47 o~ the length thereof is generally U-shaped. The configuration
shown in Figure 1 has a combustion chamber 33 which extends substantially the
length of the curved Eire tubes 41 creating a long leg 49 running along the ex-
terior of the combustion chamber 33 and separated by ~-shaped portion 47 from a
short leg 51 ~see Figure 2) which joins and extends through closed end 37. It
will be understood that the length of combustion chamber 33 can be varied such
as by shortening the length of the chamber, in which case the length of leg 51
of tubes 41 would be increased.
The ends 45 of curved tubes 41, as shown in Figure 1, preferably ex-
tend to the tube mounting flange 39 and communicate through ~lange 39 by means
of openings 53 with the tank exterior when the assembly 31 is received within
the opening 19. The tube ends 45 are fixedly secured to flange 39 as by brazing
the tube ends on the front and back sides of flange 3g. Although a small number
of curved tubes 41 are shown in Figure 1 for simplicity, a greater number of
tubes and openings can be used iJI practice. Although steel can be used in con-
structing the curved tubes 41, other acceptable materials include copper, 90 - 10
copper-nickel allcy, titanium, and stainless steel.
The combustion chamber assembly 31 can be mounted on the tank 13 by
providing a tank mounting flange 55 comprising a cylindrical ring which is
flxedly connected to the tank exterior so as ~o circumscribe the opening 19 in
tank 13 and to extend outwardly therefrom generally no~nal to the vertical side-
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walls 21 of tank 13. The end area 57 of tank moun~ing flange 55 can be provided
with a plurality of threaded bores 59 which are suitably spaced and alignable
with matching bores 61 in tube flange 39 whereby the fire tube assembly 31 can be
bolted to the tank mowlting flange 55. In this way, the combustion chamber as-
sembly 31 is removable from the water tank 13 by detaching the tube mounting
flange 31 and sli.ding the assembly out of the opening 19. Because of the ar-
rangement of opening 19 in the vertical sidewall 21 of the tank 13, the combus-
tion chamber assembly 31 is mounted in a horizontal fashion with the longitudi-
nal axis of the assembly 31 parallel to the plane of the support area 27.
As shown in Figure 1, a flue collector 63 is mounted on the tube
mounting flange 39 and has an opening 65 which communi.cates with the combustion
chamber portion 33 and an annular chamber 67 ~Figure 2~ which communicates with
the fire tubes ~1 by means of openings 53 in flange 39. A circumferential lip
69 joins the base 71 of annular chamber 67 and is provided with a plurality of
holes 73 which are alignable with bores 61 in flange 39 and threaded bores 59
in tank mounting flange 55 whereby flue collector 63 can be mounted on the ex-
terior of the tank 13. Flue collector 63 has a flue outlet 75 which communi-
cates with the interior of annular chamber 67 and which can be connected to a
flue pipe for carrying away waste gas as will be presently described.
The opening 65 in flue collector 63 which co~nunicates with chamber
33, as seen in Figure 1~ is provided in a circular partition 77 formed in the
internal diameter 79 of the exterior portion of annular chamber 71. Partition
77 can be provided with a plurality of threaded lugs 81 which are fixed about
the circumference of opening 65 and extend outwardly in normal relation thereto.
A suitab].e heat source such as a burner means is mounted on the flue collector
63 and comm~micates with the flue collector opening 65 for supplying heat to
tank 13.
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The heat source, as shown in Figure 1 and 2, can comprise a burner
nozzle 83 from a forced draft burner which has a circumferential ring 85 provid-
ed with a series of holes 87 which mate with and receive lugs 81 on partition 77
for bolting the nozzle 83 onto the flue collector 63. In this way, the noz~le
burner opening 89 can communicate with the combustion chamber 33 whereby heat
from the burner passes through the interior of the submerged combustion chamber
33 and through the fire tubes 41, into the annular chamber 67 of the flue col-
lector 63, and out the flue outlet 75 to be exhausted. Preferably, the nozzle
burner 83 is suitably constructed to work against a positive pressure.
The operation of the present water heater will now be described in
greater detail. The water heater is first assembled by moun~ing the fire tube
assembly 31 within opening 19 in tank 13. The bores 61 in fire tube flange 39
are aligned with the threaded bores S9 in tank flange 55 and the f]ue collector
63 is positioned over flange 39 with the flue outlet 75 directed upwardly with
respect to the vertical sidewalls 21. The holes 73 in circumferential lip 69
of flue collector 63 are aligned with bores 61 and the flue collector 63 and
fire tube flange 39 are bolted onto the tank flange 55. The nozzle burner 83 is
then bolted into place on partition 77 in flue collector 63 and water is intro-
duced into the tank interior 29 through water inlet 15. In the configuration
shown in Figure 1, the burner is fired to introduce hot gas into the combustion
chamber 33 to provide a positive pressure within chamber 33 with the flue gases
passing out the curved fire tubes 41 and through the flue collector annular
chamber 67 to the flue outlet 75 to be exhausted from the system. The burner 83
is switched off and on as needed to maintain the desired temperature level of
the water contained in the tank in response to a conventional temperature con-
trol circuit of the type known in the art and familiar to those in the water
heater industry.
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Water heaters as distinguished from boilers and heat exchangers are
limited by the ASME code ~o m~xi~lm internal pressure of approximately 160 psi
or approximately 210~. A water heater was constructed as in Figure 1 using
curved tubes made of copper. Gas was introduced into the system at approximate-
ly 70F and heated by the nozzle burner 83 to approximately 2800F. The water
temperature was monitored along with the stack or flue gas temperature exiting
the stack from the flue outlet 75. A~ME standards allow a flue gas temperature
as high as 480~ which correlates to a combustion efficiency of approximately
70%. The combustion efficiency is calculated by measuring the flue gas tempera-
ture subtracting the ambient air temperature and measuring the C02 content of
the flue gas. By using known charts, the combustion efficiency can be deter-
mined. With the device shown in Figures 1 and 2 a combustion efficiency of 85%
has been achieved.
An invention has been provided with significant advantages. The pre-
sent water heater has a submergible combustion chamber assembly ~hich can be
easily removed for repair or replacement. Because of the curved fire tube de--
sign and the absence of support plates, stress and corrosion are reduced. The
resulting cooler flue gas temperature ~250F) allows the flue pipe diameter to
be reduced, e.g., from approximately 6 inches for a 250,000 BTU water heater to
approximately 3 - 4 inches. Because copper material is satisfactory in the
instant application, water pipe co~per tubing of 1/~ to 2 inches in internal
diameter can be obtained off the shelf and used for the curved fire tubes there-
by reducing the cost of manufacturing specialized parts. The assembly is simple
in design and inexpensive to manufacture since the copper curved fire tubes can
be produced from commercially available stock pipe.
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