US3435816A

US3435816A - Vent arrangement for sealed combustion systems

Info

Publication number: US3435816A
Application number: US681749A
Authority: US
Inventors: Douglas W De Werth
Original assignee: American Gas Association Inc
Current assignee: Energy International Inc
Priority date: 1967-11-09
Filing date: 1967-11-09
Publication date: 1969-04-01
Anticipated expiration: 1986-04-01

Description

April 1, 1969 D. w. DE WERTH 3,435,816

VENT ARRANGEMENT FOR SEALED COMBUSTION SYSTEMS Filed Nov. 9, Sheet of 2 INVENTORI DOUGLAS W. DE WERTH ATTYS/ April 1, 1969 D. W. DE WERTH 3,435,816

VENT ARRANGEMENT FOR SEALED COMBUSTION SYSTEMS Filed Nov. 9, 1967 Sheet 2 of 2 PISA. 5 5

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United States Patent 3,435,816 VENT ARRANGEMENT FOR SEALED COMBUS- TION SYSTEMS Douglas W. De Werth, Cleveland, Ohio, assignor to American Gas Association, Inc., New York, N.Y., a corporation of New York Filed Nov. 9, 1967, Ser. No. 681,749 Int. Cl. F24c 3/12 US. Cl. 126-85 8 Claims ABSTRACT OF THE DISCLOSURE The improvement in a vent terminal for sealed combustion systems of the type including a flue gas pipe mounted coaxially within a larger combustion air pipe, comprising a combustion air by-pass opening in the combustion air pipe, and a baflie arrangement in the combustion air pipe adjacent the by-pass opening for diverting excess combustion air from the pipe.

The present invention relates generally to vent terminals for sealed combustion chamber appliances such as gasflred heaters. The invention is directed more particularly to a protective device for minimizing the effect of Wind currents on vent terminals of the type having coaxially arranged flue gas and combustion air pipes.

In the installation of gas heaters or furnaces and similar appliances which require a continuous flow of combustion air, the installation of a sealed vent system is desirable to avoid drawing the combustion air from the building within which the appliance is housed. By utilizing a sealed system, a gas heater for example may be located in a small sealed room and will not create objectionable drafts by drawing air into the building through windows, doors and cracks as does the conventional heating unit.

A common type of vent terminal used for sealed combustion systems involves coaxially arranged inlet and exhaust pipes, the exhaust gases conventionally passing outwardly through the inner pipe and the combustion air entering bet-ween the inner pipe and the larger overlying pipe. The coaxial pipes may pass horizontally through a side wall of a building or may pass vertically through the building roof. The present vent arrangement has been developed particularly for the type of vent terminal which extends horizontally through a building wall although it may also have application to the vertical type of vent installation.

For eflicient'operation of combustion appliances, it is essential that a relatively uniform pressure of the cornbustion air be maintained at the input side of the appliance to insure a uniform air flow at the optimum rate for efiicient combustion. In an appliance which draws the air from the room atmosphere, the room air pressure remains relatively constant. However, in a sealed combustion system in which the combustion air is drawn from outside the building, difficulties in maintaining a uniform combustion air pressure develop due to the Wind forces act ing on the vent terminal. In the conventional coaxial pipe vent terminal commonly used for sealed combustion systems, there is no specific provision for minimizing pressure increases due to wind currents and, as a result, the efiiciency of a combustion system with such vent terminals decreases markedly under high wind conditions as fluctuations in the combustion air flow into the system occur.

In the present invention, a protective device is provided to minimize the effects of wind blasts against the vent terminal and maintain a relatively constant combustion air input pressure to the appliance. The invention is characterized in brief by a by-pass opening in the combustion "ice air pipe outside the building wall and a bafiie arrangement in the air pipe adjacent the by-pass opening for diverting excess combustion air from the pipe. Passageways in the baffle of relatively small area permit a direct passage of combustion air through the bafile and means are provided in addition at the by-pass opening for an air flow into the combustion air pipe downstream of the baffle.

It is accordingly a principal object of the present invention to provide a vent arrangement for sealed combustion systems utilizing conventional coaxial flue gas and combustion air pipes which includes the improvement of a protective device for minimizing the effect of wind currents on the combustion air flow into the system to thereby provide an increased thermal efliciency of the system under wind conditions.

A further object of the invention is to provide a vent arrangement for sealed combustion systems as described which is adapted for employment with existing vent terminals as well as with new installations.

Still another object of the invention is to provide a vent arrangement as described of a simple construction which may be inexpensively fabricated and which requires little space.

Additional objects and advantages of the invention will be more readily apparent from the following detailed description of embodiments thereof when taken together with the accompanying drawings in which:

FIG. 1 is a sectional side elevational view taken through a vent terminal incorporating a preferred embodiment of the present invention;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken along line 3--3 of FIG. 1;

FIG. 4 is a sectional side elevational view of a vent terminal incorporating a modified form of the invention;

FIG. 5 is a sectional view taken along line 55 of FIG. 4;

FIG. 6 is a sectional side elevational view showing a protective device embodying the present invention of a design similar to that shown in FIGS. 4 and 5 and which is adapted for mounting within an existing vent terminal; and

FIG. 7 is a sectional view taken along line 77 of FIG. 6.

Referring to the drawings, FIG. 1 shows a vent terminal generally designated 10 extending horizontally through an outer wall 12 of a building to provide an inlet for combustion air and an outlet for flue gases for an appliance 14 which may be for example a gas heater. The vent terminal comprises coaxial inner and

outer pipes

16 and 18, the outer pipe 18 fitting tightly within aperture 20 in the wall 12. The inner pipe 16 defines a flue gas passageway 22 and is connected at its interior end 24 to the flue gas outlet of the appliance 14. The outer pipe 18, which is of a substantially larger diameter than the inner pipe 16, is disposed coaxially with the inner pipe to form an annular combustion air inlet passage 26 therebetween. An end plate 28 closes the interior end of the outer pipe 18 and is apertured at 30 to permit passage of the inner pipe 16 therethrough. A combustion air inlet duct 32 is connected with the outer pipe 18 at 34 adjacent the end plate 28 to connect the inlet passage 26 with the combustion air inlet 36 of the appliance 14. The exterior end of the outer pipe 18 terminates in a radially outwardly directed flange 38 to which the support ring 40 coaxial with the pipe is attached. The support ring 40 is substantially spaced from the .outer pipe 18 and abuts the exterior face of the wall 12 to provide the desired rigidity of the vent terminal.

The exterior end 42 of the inner pipe 16 extends beyond the flange 38 of outer pipe 18 and slidably receives a flange 44 of a cylindrical combustion air inlet screen 46 which is coaxially spaced from the inner pipe 16. The screen 46 is aligned with and is of the same diameter as the outer pipe 18, A radially outwardly directed flange 48 of the screen 46 of a ribbed construction is abutted against the flange 38 of the outer pipe 18 and secured thereto by screws 50. Combustion air passes from outside the building wall through the screen 46 into the combustion air passage 26 and thence through duct 32 into the appliance inlet.

A vent cap 54 is removably mounted over the open end 42 of inner pipe 16, being secured by screws 52 to the flange 44 of the screen 46. The illustrated vent cap 52 comprises a pair of

annular baffles

56 and 58 and a cap element 60, the baffles and cap element being held in spaced relation by the spacers 62. The combustion products passing from the appliance through the inner pipe 16 as indicated by the arrows pass through the vent cap 52 into the atmosphere.

The functional components of the vent arrangement described thus far are essentially conventional and the present invention resides primarily in the provision of a baflle arrangement and by-pass opening in the combustion air inlet passage 26 as described below. The invention has been developed to prevent winds acting on the combustion air screen 46 from causing an excessive flow of combustion air into the passage 26 and the appliance 14.

The effect of wind action on the combustion air flow is effectively dealt with in the present invention by providing baflle means generally designated 64 in the annular combustion air inlet passage 26 at a point exteriorly of the building wall 12. A combustion air by-pass mean generally designated 66 is cooperatively arranged with the baflle means 64 to provide a discharge to the atmosphere of wind currents entering through screen 46 which otherwise would tend to excessively build up pressure in the combustion air passage 26 and affect the combustion air flow into the appliance 14.

Considering specifically the construction of the invention embodied in the vent terminal of FIGS. 1-3, the bypass means 66 includes a downwardly directed generally rectangular duct 68 which intersects the outer pipe 18 in an area closely spaced from the exterior face of wall 12 and opens into the annular combustion air passage 26 therewithin. The duct 68 terminates at its lower end in an inverted V-shaped deflector 70 adjacent which are an inlet slot 72 in. the back wall 74 of the duct facing the wall 12, and an outlet slot 76 in the front wall 78 of the duct facing away from the wall 12. As shown most clearly in FIG. 2, the duct 68 passes through the support ring 40 and is secured thereto such as by soldering or welding.

The baffle means 64 in the embodiment of FIGS. l-3 comprises upper and

lower baffle plates

80 and 82 which are vertically secured across the combustion air passage 26 in axially spaced relation. The upper semi-annular baffle plate 80 is approximately aligned with the back wall 74 of the by-pass duct 68 and blocks axial flow through the upper half of the annular combustion air passage 26. The generally rectangular lower baffle plate 82 is axially spaced from the upper plate 80 and extends downwardly into the by-pass duct 68, terminating in a lower edge 84 spaced above and parallel to the deflector 70. The lower baffle plate 82. is spaced from the front and

back walls

78 and 74 of the duct 68 to define respective outlet and inlet passages 86 and 88 above the outlet and

inlet slots

76 and 72.

The upper edges 90 of the lower baffle plate 82 extend above the lower edges 92 of the upper baffle plate 80 and are spaced therefrom to form a pair of vertical combustion air channels 94 as shown in FIG. 1. Spacing members 96 in the channels 94 are secured to the lower edges of the upper plate 80 and the upper ends of the lower plate 82 to maintain the proper spaced relation of the baffle plates.

The vent terminal incorporating the present invention functions as follows. Combustion air from the atmosphere passes through the screen 46 into the annular combustion air inlet passage 26 and is then confronted by the baffle means 64 which in the embodiment of FIGS. l-3 comprises the upper and lower baflle plates and 82. Some of the air passes through the channels 94 between the upper and lower plates and continues into the interior portion of the passage 26 and thence through the duct 32 into the appliance 14. Any excess air flowing in through the screen 46 is diverted by the baffle plates into the bypass duct 68 from which it passes out into the atmosphere through slot 76 in the front wall thereof. Some combus tion air also enters the inner region of the inlet passage 26 through the protected inlet slot 72 in the back wall of the by-pass duct 68. The spacing of the lower edge 84 of the lower bafile plate 82 above the deflector 70 also permits air from the passage 86 to pass beneath the plate edge and into the passage 88 to join the air flow into the appliance.

The baffle and bypass structure of the present invention serves primarily to prevent wind directed against the screen 46 from affecting the normal combustion air flow into the appliance. The wind may raise the air pressure in the region of the inlet passage 26 ahead of the baffle means to a level far higher than that desired at the intake to the appliance. However, because of the restricted openings of the channels 94, only a limited flo-w of air is permitted directly into the interior region of the air inlet passage 26. The remainder of the air flow is deflected by the lower baffle plate into the bypass duct and out through outlet slot 76. At the same time, some additional air enters through the inlet slot 72 in the by-pass duct which is protected from the force of the wind.

The effectiveness of the present invention is dependent on the correct selection of the relative sizes of the passages 94 and the by-pass duct outlet slot 76 to provide a substantially smaller pressure drop through the bypass duct than through the passages 94 during operating of the appliance. If the resistance of the passages 94 through the baflie means 64 is not sufliciently high with respect to that through the by-pass duct, insufficient protection will be afforded. On the other hand, if the relative pressure drop is too high, the necessary flow of combustion air into the appliance may be curtailed resulting in poor combustion and low thermal efficiency. While it can be understood that these relative values may change depending on characteristics of a particular installation, as an example of the pressure drops measured in a satisfactory embodiment of the invention, the pressure drop across the baflle means in the inlet passage 26 Was 0.03 of water while the pressure drop through the by-pass duct slot was 0.015" of water. The resistance to flow through the baffle passages 94 was thus substantially higher than that through the hy-pass duct, and excess wind entering through the screen 46 would thus take the course of least resistance through the by-pass duct outlet slot.

The embodiment of FIGS. 4 and 5 is identical to that of FIGS 1-3 with the exception of the bafile means, and the corresponding parts are accordingly indicated by the same identifying numbers. In this embodiment, the baffle means comprises a single inclined baffle plate 100 which is apertured to permit passage therethrough of the inner pipe 16. The baflle plate 100 is inclined at an angle to the vertical with the upper edge 102 thereof being positioned above the front wall 78 of the by-pass duct 66 while the lower edge 104 of the baffle plate terminates between the front and rear walls of the rectangular duct 66 in spaced relation above the deflector 70. As shown most clearly in FIG. 5, the upper edge 102 of the baffle plate 106 terminates short of the outer pipe 18 to form a semiannular; slot 106 therebetween which constitutes the primary combustion air passage into the interior region of the annular inlet passage 26.

The embodiment of FIGS. 4 and 5 operates essentially in the same manner as that of FIGS. 1-3, the semi-annual slot 106 serving the same function as the passages 04 of the preferred embodiment. Any excess air entering through the screen 46 is channeled by the inclined baflle plate 100 into the by-pass duct 66 and passes out through the outlet slot 76. Combustion air flows as indicated by the arrows in FIG. 4 through the slot 106 into the interior region of the annular inlet passage 26 at a substantially uniform rate despite wind fluctuations. Additional combustion air may enter through the inlet slots 72 in the back wall of the bypass duct and pass behind the inclined baflle plate 100 into inlet passage 26.

In FIGS. 6 and 7, an embodiment of the invention which is essentially the same as that of FIGS. 4 and 5 is provided in an adapter unit which can be used to convert an existing vent terminal to the present invention. The adapter unit generally designated 110 comprises a length of pipe 118 having an outer diameter of a size permitting a tight fit within outer pipe 18 of a conventional installation. The adapter unit includes a bathe means comprising a battle plate 120 which cooperates with a by-pass duct 122. As shown in the drawings, the outer pipe 18 is secured to the wall 12 by the screwed attachment of an exterior flange 19. With the cap and inlet screen removed from the inner pipe 16, the adapter unit 110 is slid axially into position and secured by the spaced tangs 123 and screws 124 to the wall 12.

With the cap and air inlet screen in position to complete the converted vent terminal, the adapter unit 110 of the embodiment of FIGS. 6 and 7 functions in exactly the same manner as the previously described embodiments in controlling the excess air entering the vent terminal under wind conditions. In this respect the by-pass duct 122 is provided with an outlet slot 126 and inlet slot 128 which correspond with the outlet and

inlet slots

76 and 72 of the embodiment of FIGS. 4 and 5. Similarly, a semi-annular slot 130 is provided at the upper end of the inclined baflle plate 122 and is the equivalent of the slot 106 of the previously discussed embodiment.

While the thermal efficiency of appliances equipped with vent terminals employing the present invention will decrease under wind conditions, the decrease is substantially less than that which would take place in the absence of the invention. In actual tests of an appliance which under no Wind conditions has a thermal efliciency of 71%, at a wind speed of miles an hour with a conventional vent terminal the efliciency drops to approximately 60%. Using the present by-pass system, the efliciency of the appliance at this Wind speed drops only to approximately 68%. The loss in efliciency is thus only about 27% of What it would be Without the protective device at a wind speed of 10 miles an hour. Since wind velocities in a given location might typically average over 10 miles per hour, it can be understood that substantial economies can be realized by use of the present device due to the substantially improved thermal efficiency of the appliance with which it is used under wind conditions.

Manifestly, changes in details of construction can be effected by those skilled in the art without departing from the spirit and the scope of the invention as defined in and limited solely by the appended claims.

I claim:

1. In a vent terminal for sealed combustion systems of the type including a flue gas pipe mounted coaxially within a larger combustion air pipe, the coaxial pipes extending through a wall of the structure within which the cornbustion system is located, the improvement comprising combustion air by-pass means in said combustion air pipe exteriorly of the structure wall, and bafile means 6 in said combustion air pipe for diverting excess combus tion air from said pipe into said by-pass means.

2. The improvement as claimed in claim 1 wherein said combustion air by-pass means comprises a downwardly directed duct.

3. The improvement as claimed in claim 2 wherein said baflle means comprises a baflle plate extending into said duct.

4. In a vent terminal for sealed combustion systems of the type including a flue gas pipe mounted coaxially within a larger combustion air pipe, the coaxial pipes extending horizontally through a wall of the structure within which the combustion system is located, the improvement comprising means for diverting excess combustion air from the pipe, said means comprising a downwardly directed duct extending from the opening into said combustion air pipe exteriorly of the structure wall, baflle plate means in said combustion air pipe extending into said downwardly directed duct, passage means in said baflle plate means for permitting a flow of combustion air through said baffle plate means, passage means in said duct permitting an outflow of air to the atmosphere diverted by said baflle plate means, the flow resistance of the baflle plate means passage means being substantially larger than the flow resistance through said duct passage means whereby excess combustion air in said combustion air pipe flows outwardly through said duct passage means.

5. The improvement as claimed in claim 4 wherein said baflle plate means comprises an inclined bathe plate, said baffle plate being angularly inclined with respect to the vertical to divert excess air from the combustion air pipe into the duct, said passage means in the baflie means comprising a slot adjacent the upper edge of said baflle plate.

6. The improvement as claimed in claim 4 wherein said baffle plate means comprises upper and lower axially spaced vertical baffle plates, said lower baflle plate extending into said duct for diverting excess air thereinto, said upper baffle plate blocking flow through the upper half of said combustion air pipe, said passage means through said baflle means comprising a pair of vertical passages between said upper and lower baflie plates.

7. The improvement as claimed in claim 4 wherein said duct terminates downwardly in an inverted V-shaped deflector, said batfle plate means terminating above and in spaced relation to said deflector, said duct outlet passage means comprising a first slot in the exterior wall of said duct adjacent said deflector, and a second slot opposed from said first slot in the interior wall of said duct providing a combustion air passage into said combustion air pipe to supplement said pasage means in said bafile plate means.

8. An adapter unit for adding a wind protective device to a vent terminal for sealed combustion systems of the type including a flue gas pipe mounted coaxially within a larger combustion air pipe and wherein said coaxial pipes pass horizontally through a wall of the structure within which the combustion system is located, said adapter unit comprising a pipe adapted to fit within the combustion air pipe of said terminal, combustion air bypass means in said adapter pipe, and baflle means in said adapter pipe cooperatively arranged with respect to said by-pass means for diverting excess combustion air into said by-pass means.

References Cited UNITED STATES PATENTS 3,056,400 10/1962 Hammersley 126-307 FREDERICK KETTERER, Primary Examiner,