U.S. patent application number 14/955320 was filed with the patent office on 2016-07-28 for radiant tube assembly.
The applicant listed for this patent is Superior Radiant Products Limited. Invention is credited to Samer Hassan, Kevin Merritt.
Application Number | 20160215973 14/955320 |
Document ID | / |
Family ID | 56432462 |
Filed Date | 2016-07-28 |
United States Patent
Application |
20160215973 |
Kind Code |
A1 |
Hassan; Samer ; et
al. |
July 28, 2016 |
RADIANT TUBE ASSEMBLY
Abstract
The present concept is a radiant tube assembly that includes a
burner assembly firing combustion gases into a combustion tube
which emits radiant heat energy from its outer surface. A black
ceramic coating is applied the outer surface of the combustion tube
to increase the emissivity of the combustion tube and lower the
temperature of the outer surface of the combustion tube.
Semi-circular top and semi-circular bottom inserts extending
longitudinally along the length of a first section of the
combustion tube lower the combustion tube outer temperature.
Inventors: |
Hassan; Samer; (Mississauga,
CA) ; Merritt; Kevin; (Burlington, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Superior Radiant Products Limited |
Hamilton |
|
CA |
|
|
Family ID: |
56432462 |
Appl. No.: |
14/955320 |
Filed: |
December 1, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62106928 |
Jan 23, 2015 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23C 3/002 20130101;
F23D 14/125 20130101 |
International
Class: |
F23C 3/00 20060101
F23C003/00; F23D 14/12 20060101 F23D014/12 |
Claims
1. A radiant tube assembly comprising: a) a burner assembly firing
combustion gases into a combustion tube wherein, the combustion
gases travelling down the interior of the combustion tube; b) the
combustion tube emits radiant heat energy from an outer surface of
the combustion tube; c) a black ceramic coating applied to an outer
surface extending from a start point and along the combustion tube
for increasing the emissivity of the combustion tube thereby
lowering the temperature of the outer surface of the combustion
tube.
2. The radiant tube assembly claimed in claim 1 wherein the black
ceramic coating is applied to the outer surface of the first 4 to
12 feet of the combustion tube
3. The radiant tube assembly claimed in claim 2 wherein the black
ceramic coating is applied to the outer surface providing an
emissivity greater than 0.88.
4. The radiant tube assembly claimed in claim 2 wherein the black
ceramic coating is applied to the outer surface providing an
emissivity greater than 0.90.
5. The radiant tube assembly claimed in claim 3 wherein the
combustion tube includes a single top insert extending from a start
point and into the combustion tube, and wherein the top insert lies
adjacent to the inner surface of the combustion tube and is
semi-circular in cross section wherein the insert lowers the tube
outer surface temperature.
6. The radiant tube assembly claimed in claim 3 wherein at least
the first 4 feet of the combustion tube includes a single top
insert which lies adjacent to the inner surface of the combustion
tube wherein the top insert is semi-circular in cross section
wherein the insert lowers the tube outer surface temperature.
7. The radiant tube assembly claimed in claim 3 wherein at least
the first 4 feet of the combustion tube includes a single top
insert which lies adjacent to the inner surface of the combustion
tube wherein the single top insert is over semi-circular in cross
section such that it is self-supporting within the combustion tube
wherein the insert lowers the tube outer surface temperature.
8. The radiant tube assembly claimed in claim 3 wherein the
combustion tube includes a single top insert extending from a start
point and into the combustion tube, which lies adjacent to the
inner surface of the combustion tube and a single bottom insert
extending from a start point and into the combustion tube, which
lies adjacent to the inner surface of the combustion tube, wherein
the top and bottom inserts are semi-circular in cross section and
abut along a longitudinal joint wherein the inserts lower the tube
outer surface temperature.
9. The radiant tube assembly claimed in claim 8 wherein at least
the first 4 feet of the combustion tube includes a single top
insert and a single bottom insert.
10. The radiant tube assembly claimed in claim 3 wherein the
combustion tube includes a top insert extending from a start point
and into the combustion tube, which lies adjacent to the inner
surface of the combustion tube and a bottom insert extending from a
start point and into the combustion tube, which lies adjacent to
the inner surface of the combustion tube, wherein the top and
bottom inserts are semi-circular in cross section and abut along a
longitudinal joint and further includes an additional single top
insert which abuts the other inserts at a transverse joint wherein
the inserts lower the tube outer surface temperature.
11. The radiant tube assembly claimed in claim 10 wherein the
single top insert is semi-circular in cross section.
12. The radiant tube assembly claimed in claim 10 wherein the
single top insert is over semi-circular in cross section such that
it is self-supporting within the combustion tube.
13. The radiant tube assembly claimed in claim 10 wherein at least
the first 4 feet of the combustion tube includes the top and bottom
inserts.
14. The radiant tube assembly claimed in claim 10 wherein at least
the first 4 feet of the combustion tube includes the top and bottom
inserts and the single top insert is also at least 4 feet in
length.
15. A radiant tube assembly comprising: a) a burner assembly firing
combustion gases into a combustion tube wherein, the combustion
gases travelling down the interior of the combustion tube; b) the
combustion tube emits radiant heat energy from an outer surface of
the combustion tube; c) a black ceramic coating applied to an outer
surface extending from a start point and along the combustion tube
for increasing the emissivity of the combustion tube thereby
lowering the temperature of the outer surface of the combustion
tube; d) a semi-circular top insert and a semi-circular bottom
insert extending longitudinally along the length of a first section
of the combustion tube, the inserts for lowering the combustion
tube outer temperature.
16. The radiant tube assembly claimed in claim 15 wherein inserts
extend along the length of the first two sections of the combustion
tube.
17. The radiant tube assembly claimed in claim 15 wherein the first
section extends from a start point to 3 to 6 feet along the length
of the combustion tube.
18. The radiant tube assembly claimed in claim 16 wherein the
second section extends from 6 to 12 feet along the length of the
combustion tube.
Description
[0001] This application claims priority from U.S. provisional
application 62/106,928 filed on Jan. 23, 2015 by Samer Hassan and
Kevin Merritt.
FIELD OF THE INVENTION
[0002] The present invention relates to gas fired radiant heaters
and more particularly relates to radiant tube assemblies for gas
fired radiant heaters.
BACKGROUND OF THE INVENTION
[0003] Traditionally gas fired radiant tube heaters that are fueled
with natural gas typically run at a combustion tube temperature
above 750 degrees Fahrenheit and more typically closer to 900 to
1,000 degrees Fahrenheit in the hottest areas of the combustion
tube normally nearest the gas burner. There are applications where
these very high combustion tube temperatures cannot be tolerated
for safety reasons. One such application is in repair facilities
for compressed natural gas vehicles and other natural gas
processing equipment. Due to the inherent danger of the presence of
natural gas in repair facilities, traditionally fired natural gas
fueled radiant tube assembly heaters have been unsuitable due to
the very high combustion tube temperatures. Safety standards for
compressed natural gas repair facilities for example dictate that
the combustion tube temperature not exceed 750 degrees Fahrenheit.
This is due in part to the fact that the spontaneous combustion
temperature of natural gas ranges somewhere between 950 and 1,100
degrees Fahrenheit depending upon the chemical composition of the
natural gas.
[0004] In order to safely utilize gas fired radiant tube heaters
within compressed natural gas repair facilities it is necessary to
reduce the maximum combustion tube temperature to below 750 degrees
Fahrenheit in order to meet the safety standards required in these
facilities.
[0005] Current gas fired radiant tube heater assemblies do not meet
the requirements for use within compressed natural gas repair
facilities due to the high combustion tube temperatures typically
experienced with traditional gas fired radiant tube heaters.
[0006] Radiant heating however would be preferred to for example
forced air heating which is currently used in many of these
compressed natural gas repair facilities since there is a very high
rate of air exchange due to the large doors which typically open
and close numerous times per day in order to facilitate movement of
vehicles in and out of buildings. Heating compressed natural gas
repair facilities with conventional forced air heating is a very
expensive way to maintain temperature within these buildings.
[0007] Therefore there is a need for a radiant tube heater which
would meet safety standards of compressed natural gas repair
facilities and other natural gas facilities which require a
combustion tube temperature of no more than 750 degrees Fahrenheit
in order to safely operate radiant tube heaters.
SUMMARY OF THE INVENTION
[0008] The present concept is a radiant tube assembly comprising:
[0009] a) a burner assembly firing combustion gases into a
combustion tube wherein, the combustion gases travelling down the
interior of the combustion tube; [0010] b) the combustion tube
emits radiant heat energy from an outer surface of the combustion
tube; [0011] c) a black ceramic coating applied to an outer surface
extending from a start point and along the combustion tube for
increasing the emissivity of the combustion tube thereby lowering
the temperature of the outer surface of the combustion tube.
[0012] Preferably wherein the black ceramic coating is applied to
the outer surface of the first 4 to 12 feet the combustion
tube.
[0013] Preferably wherein the black ceramic coating is applied to
the outer surface providing an emissivity greater than 0.88.
[0014] Preferably wherein the black ceramic coating is applied to
the outer surface providing an emissivity greater than 0.90.
[0015] Preferably wherein the combustion tube includes a single top
insert extending from a start point and into the combustion tube,
and wherein the top insert lies adjacent to the inner surface of
the combustion tube and is semi-circular in cross section wherein
the insert lowers the tube outer surface temperature.
[0016] Preferably wherein at least the first 4 feet of the
combustion tube includes a single top insert which lies adjacent to
the inner surface of the combustion tube wherein the top insert is
semi-circular in cross section wherein the insert lowers the tube
outer surface temperature.
[0017] Preferably wherein at least the first 4 feet of the
combustion tube includes a single top insert which lies adjacent to
the inner surface of the combustion tube wherein the single top
insert is over semi-circular in cross section such that it is
self-supporting within the combustion tube wherein the insert
lowers the tube outer surface temperature.
[0018] Preferably wherein the combustion tube includes a single top
insert extending from a start point and into the combustion tube,
which lies adjacent to the inner surface of the combustion tube and
a single bottom insert extending from a start point and into the
combustion tube, which lies adjacent to the inner surface of the
combustion tube, wherein the top and bottom inserts are
semi-circular in cross section and abut along a longitudinal joint
wherein the inserts lower the tube outer surface temperature.
[0019] Preferably wherein at least the first 4 feet of the
combustion tube includes a single top insert and a single bottom
insert.
[0020] Preferably wherein the combustion tube includes a top insert
extending from a start point and into the combustion tube, which
lies adjacent to the inner surface of the combustion tube and a
bottom insert extending from a start point and into the combustion
tube, which lies adjacent to the inner surface of the combustion
tube, wherein the top and bottom inserts are semi-circular in cross
section and abut along a longitudinal joint and further includes an
additional single top insert which abuts the other inserts at a
transverse joint wherein the inserts lower the tube outer surface
temperature.
[0021] Preferably wherein the single top insert is semi-circular in
cross section.
[0022] Preferably wherein the single top insert is over
semi-circular in cross section such that it is self-supporting
within the combustion tube.
[0023] Preferably wherein at least the first 4 feet of the
combustion tube includes the top and bottom inserts.
[0024] Preferably wherein at least the first 4 feet of the
combustion tube includes the top and bottom inserts and the single
top insert is also at least 4 feet in length.
[0025] The present concept is a radiant tube assembly comprising:
[0026] a) a burner assembly firing combustion gases into a
combustion tube wherein, the combustion gases travelling down the
interior of the combustion tube; [0027] b) the combustion tube
emits radiant heat energy from an outer surface of the combustion
tube; [0028] c) a black ceramic coating applied to an outer surface
extending from a start point and along the combustion tube for
increasing the emissivity of the combustion tube thereby lowering
the temperature of the outer surface of the combustion tube; [0029]
semi-circular top insert and a semi-circular bottom insert
extending longitudinally along the length of a first section of the
combustion tube, the inserts for lowering the combustion tube outer
temperature.
[0030] Preferably wherein inserts extend along the length of the
first two sections of the combustion tube.
[0031] Preferably wherein the first section extends from a start
point to 3 to 6 feet along the length of the combustion tube.
[0032] Preferably wherein the second section extends from 6 to 12
feet along the length of the combustion tube.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The present concept will be described by way of example only
with reference to the following drawings in which:
[0034] FIG. 1 is a schematic side cross sectional view of a radiant
tube assembly with a burner assembly and a combustion tube.
[0035] FIG. 2 is a schematic cross sectional view taken along lines
2-2 of FIG. 1 showing the cross section through the combustion tube
with the top and bottom inserts in place.
[0036] FIG. 3 is a cross sectional schematic view of the combustion
tube taken along lines 3-3 showing a single top insert in
place.
[0037] FIG. 4 is a schematic perspective view of the radiant tube
assembly together with a burner assembly and a combustion tube.
[0038] FIG. 5 is a plot of temperature vs. length along the
combustion tube for a 100,000 BTU burner showing top
temperatures.
[0039] FIG. 6 is a plot of temperature vs. length along the
combustion tube for a 100,000 BTU burner showing top
temperatures.
[0040] FIG. 7 is a plot of temperature vs. length along the
combustion tube for an 80,000 BTU burner showing top
temperatures.
[0041] FIG. 8 is a plot of temperature vs. length along the
combustion tube for an 80,000 BTU burner showing bottom
temperatures.
[0042] FIG. 9 is a plot of temperature vs. length along the
combustion tube for a 60,000 BTU burner showing top and bottom
temperatures.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0043] The present concept a radiant tube assembly shown generally
as 100 includes a combustion tube 102 and a burner assembly 104.
Burner assembly 104 mixes air and fuel together to produce
combustion gases 107 which travel down combustion tube 102 thereby
heating combustion tube 102 which emits heat energy in the form of
radiant energy from outer surface 125.
[0044] Combustion tube 102 includes a first section 106 and a
second section 108. First section 106 includes a top insert 110 and
a bottom insert 112 which join at a longitudinal joint 114 along
the length of each of the inserts. Top insert 110 abuts with bottom
insert 112 along the longitudinal joint line 114. Second section
108 includes a single top insert 116 which abuts and joins at
transverse joint line 118 with top and bottom insert 110 and 112.
The balance of the combustion tube 102 normally would not include
any further inserts.
[0045] First section 106 may be three to six feet in length and
second section 108 may also be typically three to six feet in
length. It was found that the two top inserts depicted could be
combined into one of between 4 to 12 feet in length, rather than
two shorter top inserts. In some cases 4 feet of top insert was
sufficient depending upon the burner firing rate. In practice
however it was more convenient and installation was easier by
dividing the top inserts into two lengths as depicted of about
three to six feet each.
[0046] The outer surface 125 of combustion tube 102 is coated with
a ceramic exterior coating 120 to improve the emissivity of the
outer surface 125 of combustion tube 102 thereby lowering the
temperature of the outer surface 125 of the combustion tube 102.
Increasing emissivity results in more energy being released by the
combustion tube 102 thereby lowering its outer surface temperature
at a given firing rate. This is contrary to conventional thinking
which attempts to maximize outer surface 125 tube temperatures.
Preferably a black ceramic coating is applied to the outer surface
having an emissivity>0.88 and preferably>0.90. In practice
black ceramic coatings yield emissivity values typically from 0.90
to 0.93.
[0047] At minimum the first four feet of the combustion tube is
coated however as much as 12 feet may be coasted. On average it was
found that the first six to ten feet need to be coated to obtain
optimum results. For reference purposes combustion tube 102
includes a top 122 and a bottom 124 and a start point 128.
[0048] Referring now to FIGS. 2 and 3 the reader will note that the
inserts namely top insert 110 and bottom insert 112 and single top
insert 116 are inserted into the inner diameter of combustion tube
102 and lay adjacent to the inner surface 127 of combustion tube
102. Similarly single top insert 116 normally extends partially
around the inner surface 127 of combustion tube 102 and past the
center line 129 as depicted in FIG. 3 in order to maintain the
positioning of single top insert 116. This is termed over
semi-cylindrical in shape.
[0049] Top insert 110 is preferably semicircular in cross section
namely a semi-cylinder such that the top half of the inner surface
127 of the combustion tube is lined. Top insert 110 which is a
semi-cylindrical is depicted in FIGS. 1 and 2. In the event there
is only a top insert and no bottom insert the single top insert 116
may have a cross section which is over semi-circular such that more
than the top half of the inner surface 127 of the combustion tube
is lined with a top insert which is an over semi-cylinder as
depicted in FIGS. 1 and 3. In this manner the single top insert 116
is self-supporting within the combustion tube 102. In theory a
semi-cylindrical shaped insert should be self-supporting however in
practice an over semi-cylindrical shaped insert is required to
obtain consistent self support. The bottom insert 112 is normally
semi-cylindrical since it is normally used in conjunction with a
top inset 110. FIG. 4 shows in schematic fashion radiant tube
assembly 100 with a combustion tube 102 and the burner assembly
104.
[0050] Referring now to FIGS. 5 through 9 all of which are graphs
which plot distance measured in feet on the x axis against outer
surface tube temperature in degrees Fahrenheit on the Y axis.
[0051] The starting point or zero in feet is start point 128 which
normally is approximately 3 inches in from the end of burner
assembly 104. Temperatures are measured on the top 122 and the
bottom 124 of the outer surface of combustion tube 102 at one foot
intervals by thermocouples arranged on the top and bottom surfaces
of combustion tube 102 in order to measure the temperatures.
[0052] The reader will see that graph 5 for example depicts the
temperature in degrees Fahrenheit along the top of combustion tube
in one foot intervals under various conditions.
[0053] For example the thick solid black line shows a conventional
gas fired radiant tube heater with no exterior coating 120 on the
outer surface 125 and only with a top insert 110 and a single top
insert 116 in place. You will see that the maximum temperature
achieved is over 950 degrees Fahrenheit at approximately the three
foot mark along the length of the combustion tube 102.
[0054] The long dashed line shows the temperature profile with a
black ceramic exterior coating 120 on the outer surface 125 and
once again two inserts in place namely top insert 110 and single
top insert 116 in this case the maximum temperature achieved is
approximately 740 degrees Fahrenheit at approximately four feet
along the combustion tube.
[0055] The third line which is the short dashed line depicts the
result of a black ceramic exterior coating 120 on the outer surface
125 of combustion tube 102 together with three inserts in place a
top insert 110 a bottom insert 112 and a single top insert 116.
[0056] The reader will note that the outer surface combustion tube
maximum temperature achieved in this case is approximately 710
degrees Fahrenheit at about 8 feet along the combustion tube
102.
[0057] Similarly in FIG. 6 the three graphs are depicted for
temperatures which are measured along the bottom 124 of combustion
tube 102 again at one foot intervals.
[0058] FIGS. 5 and 6 are for a burner rated at a 100,000 BTU firing
rate.
[0059] FIGS. 7 and 8 are for an 80,000 BTU firing rate burner
wherein FIG. 7 depicts the temperature profile on the top 122 for
black ceramic exterior coatings 120 in place on the combustion tube
together with two inserts namely top insert 110 and single top
insert 116 and three inserts namely top and bottom inserts 110 and
112 and a single top 116.
[0060] FIG. 9 depicts the temperature profiled for a 60,000 BTU
firing rate for a combustion tube 102 which has a black ceramic
exterior coating 120 and only two inserts in place namely top
insert 110 and single top insert 116. The dark black line shows the
top temperatures taken along top 122 and the dashed line shows
bottom temperatures taken along the bottom 124.
In Use
[0061] The reader will note that the greatest temperature reduction
is achieved by the use of the black exterior ceramic coating 120
along the outer surface 125 of combustion tube 102. The use of the
coating itself however achieves the results which were marginal in
terms of reducing the overall temperature to below 750 degrees
Fahrenheit on an ongoing basis.
[0062] In addition to the exterior coating 120 inserts were added
to the interior of combustion tube 102 namely top insert 110,
bottom insert 112 and single top insert 116 along the first two
sections namely first section 106 and second section 108 as
depicted in FIG. 1 in order to further reduce the combustion to a
temperature as shown in the short dashed line.
[0063] The reader will note that in particular referring to FIG. 6
the bottom insert 112 had a dramatic effect in reducing the bottom
124 temperatures to well below 750 degrees Fahrenheit which was not
the case in for example the large dashed line showing a coated
combustion tube with only 2 inserts namely top insert 110 and
single top insert 116 in place.
[0064] The reader will note that in every case the inventors were
able to reduce the maximum temperature seen along the top of 122
and bottom 124 of the combustion tube 102 to below 750 degrees
Fahrenheit with a combination of either exterior ceramic coating
120 together with combustion tube top insert 110, bottom insert 112
and single top insert 116 as required.
[0065] It should be apparent to persons skilled in the arts that
various modifications and adaptation of this structure described
above are possible without departure from the spirit of the
invention the scope of which defined in the appended claim.
* * * * *