US2452946A - Direct fuel fired unit air heater - Google Patents

Description

Nov. 2, 1948-- 1.. F. M CO NNELL 2,452,946

A I DIRECT FUEL FIRED UNIT AIR HEATER Filed June 14, 1945 2 Sheets-Sheetl z I F/ z INVENTOR.

2 Sheets-Sheet 2 an m Nov. 2, 1948. L. F. M CONNELL DIRECT FUEL FIRED UNIT AIR HEATER Filed Jun 14, 1945 1N VEN TOR.

BY gum WZCM Patented Nov. 2, 1948 2,452,946 DIRECT FUEL FIRED UNIT AIR HEATER Leslie F. McConnell, Birmingham, Ala., assignor to McConnell Sales and Engineering Corporation, a corporation of Alabama Application June 14, 1945, Serial No. 599,443

6 Claims.

My invention relates to a direct oil fired unit air heater for furnishing comparatively low temperature heated air for drying, baking and similar purposes where clean, smoke free, odor free and poisonous gas free, accurately controlled, warm or hot air is required.

In the drying of raw cotton. textiles food stuiis and similar commodities emciently, it is necessary to remove the moisture content in the material with heated air. In the drying of these materials in the past, it has been necessary to use indirect fuel fired type heaters or steam heaters for heating the air. These types of heaters are ineflicient and the maintenance costs are high. There are direct oil fired unit heaters used on crude drying and baking ovens where smoke and gases are not detrimental to the processes, however, these have not been satisfactory for the purposes listed above.

My invention is based on the principle of proper combustion of fuel oil in which complete combustion of the oil to CO2 and H20 occur only at high temperatures and with proper fuel-air ratio. It is also based on the principle that aldehydes or pungent gases can be formed in the combustion of fuel oil if low temperature air cools the flame prior to complete combustion and my apparatus is designed to prevent the cool air from coming in contact with the flame before complete combustion takes place.

The average unit air heater being used today requires a large space as due to the principle of firing the combustion space necessary is based on B. t. u. heat release per cubic foot of combustion space and 25,000 to 50,000 E. t. u. is considered maximum. My invention utilizes the principle of combustion chamber flame capacity rather than thermal release of heat units and I am able to obtain at least 125,000 B. t. u. of fuel combustion per cubic foot of combustion space without affecting the efficiency of the unit heater or the purity of the heated air with the result that my invention requires a very small space.

My invention is illustrated more or less diagrammatically in the accompanying drawings, wherein- Fig. 1 is a view in elevation showing my improved heater;

Fig, 2 is a vertical cross section through the heater; and

Fig. 3 is a sectional plan view of the heater through the burner block.

Referring-to the drawings in which like reference numerals indicate the same parts,

A is the outer hood.

2 B is the outer shell of the air heater.

C is the outlet air duct.

D are cast or pipe supports for the angleE which partially supports the cast grating H which in turn support the combustion chamber.

E is a circular shaped angle welded to the supports D for partially supporting the cast grating.

G is a circular shaped angle welded to the outer shell for supporting the cast grating.

H are cast grating areas for supporting the refractories. This could be a solid plate, however, I have foundcast grating to be superior.

J is a, rammed plastic refractory used to save installation costs. It is understood that refractory shapes could be used if desired.

K is a refractory or alloy cylinder either solid or sectional the height of which is variable depending on the flame capacity required.

L is a refractory brick or plastic lining.

M is an outer lining of insulating or soft refractory material to allow provision for expansion of the refractory lining.

N is a superrefractory material used to withstand the fiame impingement adjacent to the burner.

0 is the refractory burner block that can be adjusted as to location either vertically or horizontally in order to obtain proper combustion to meet variable conditions and to give a centrifugal movement of the combustion flame.

It is understood that any number of burners and burner blocks can be used if desired. It is also understood that the burner block is part of the fuel burner used with this unit heater and although the burner or burners are not shown in the drawing the burner block diagrammatically represents the burners used. These burners may be either manually or automatically ignited.

P is a cast or fabricated inner hood having ribs or vanes to both impart additional heating to the incoming air by providing greater contact surface and to also direct the incoming air in a centrifugal flow counter current to that of the centrifugal flow of the combustion flame,

Q is the counterbalanced damper in the vent stack.

R is the vent stack.

S is the counterbalance for the stack damper.

In the operation of my invention, an exhaust fan connected to the outlet C pulls the air to be heated through the air heater. The burner or burners are either manually controlled or automatically controlled to regulate the temperature of the heated air. The unit air heater can be completely equipped with safety devices to prevent explosions, incomplete combustion, venting of the heater before lighting. A solenoid shut off valve is located in the fuel line which in turn is wired through the combustion air fan, which delivers air through the burner block 0, so that fuel cannot be supplied to the unit unless the combustion air is supplied to the burner. An air flow switch is'l'ocated inthe exhaust duct which is also wired through the fuel line shut off valve so that no fuel can be sup lied to the air heater unless air is being pulled through the unit heater. A flame protection device canbe sup-plied to close off all fuel in the event of flame failure.

From the foregoing, it willbes'een thatIhave provided a direct fuel fired unit heater in which the outside of the central air ducti's hotter than the inside thereof, thereby resulting in longer life. In a circular refractory or alloy shape, the" outer circumference of the shape is proportionally greater than the inner circumference.- As the coefiicient of expansion of themater'ial'is a constant, if the inside wall can-be kept at a; lower temperature than the outside, as is the case with my invention, there is a decided freedom from cracking. Where the combustion chamber is in the center and'the airiso'n the outside as is the case' with'- conventional air heaters, there'- is a higher temperature on the inside and a lower temperature on the'out'side' which causes serious cracking due to the fact that the outer circumference does not-expand in proportion' tothe inner circumference.

.r claim:

1. In a furnace of thecharacter described, a circular wall forming a combustion chamber, a circular duct disposed concentrically within the combustion chamberand spaced from the walls thereof, said combustion chamber having an'inlet opening at oneend'for air to be heated' inalignmentwith the circular duct; means in the inlet opening to impart centrifugal movement to the" air, and a fuel burner disposedt'angentially of the combustion chamber at the other end thereofthrough the combustion chamber wall, and dis posedto iinparta centrifugal 'movement to the products of combustion in animation-counter to bustion chamberhaving. a cylindrical outer shell;-

chamber, open at its upper end and having an outlet at its lower end for commingled air and products of combustion, and a hood over the comb-ustion chamber and duct having a skirt extending downwardly in spaced relation around the combustion chamber to provide an air inlet into the combustion chamber. 1

4L An'air' heating furnace comprising a vertical- 13 disposed cylindrical combustion chamber, means to introduce products of combustion tangentially into the lower end of the combustion chamber at one end thereof, a cylindrical duct disposed concentrically within the combustion chamber, open at it'supper end and having an outlet at its lower" end for commingled air and products 'of'combustion, and a hood over the combustion chamber and duct having a skirt extending downwardly in spaced relation around the combustion chamber to provide an air inlet into the combustion chamber, and means to impart a whirling motion to the air entering the duct.-

5. In an air heating furnace, an outer cylin dric'al shell having an opening in its bottom, an open: ended inner cylindrical shell of less diameter and length than the outer shell fitting-at its lower end in said opening, a cover for the outer shell spaced above the open upper end of the inner shell and having an air' passage in align ment With the opening in said innershell, a burner positioned between said inner and outer hells adjacent'the bottomsthereof, and'me'ans to draw air-downwardly through-the inner shell.

6. man ai'r heating furnace, an outer'cyli-ndr'ical shell'of refractory material having a bottom and a cover} a centrally open cylindrical shell of refractory material of less diameter and length than-the"outer shell-over said bottom'opening}. a fuel burner adjacent'the bottoms'of said cylindrical shells and disposed to discharge tangentially therebetween, a" hood'over the top'ofthe outer shell having a depending skirtspaced-from the'walls-of theo'u-tershell, there being a ceii' trall'y disposed openin'g in said cover over the in ner shellgand mean's to draw air into saidhood and downwardly throughthe inriefshell.

LESLIE F. MCCONNELL.-

REFERENCES CITED" fhe following references are of" recordin the file of this patent: V

UNITED STATES PATENTS France' uri July 24 1-939

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