Stoves and furnaces – Hot-air furnaces – Compressed air
Reexamination Certificate
2000-05-19
2003-03-04
Price, Carl D. (Department: 3743)
Stoves and furnaces
Hot-air furnaces
Compressed air
C126S11000R, C126S11600A, C431S354000, C431S351000, C431S010000, C432S222000
Reexamination Certificate
active
06526964
ABSTRACT:
BACKGROUND OF THE INVENTION
The burner assembly of this invention is utilized in the capacity generally defined as a direct gas-fired industrial air heater or related type of make-up air heater. This type of heater is normally employed within an industrial or commercial complex which requires large volumes of tempered air to replace air that is being exhausted or to provide ventilation air to purge contaminants from the space. The invention herein is not a heat exchanger, since the combustion of the gas after its ignition takes place directly within the air stream being heated and not by any conduction thereof. It is the improvement of the invention that further adds to the efficiency of the combustion within an industrial heater of this design, so as to work most effectively and safely in producing the quantity of heated air that may be needed to warm the environs, and to effectively maintain a uniform and comfortable temperature within a predetermined volumetric space, as within a building, but at the same time, do it in such a manner that does not sacrifice safety in the heater design, during the performance of gaseous combustion in producing the source of heat. As a result, the heating equipment of this invention, in which the direct fired burner of this type is enclosed, contains no flue, and all of the by-products of combustion are released directly into the heated air stream, which is then directly discharged into the space being heated, and as a result it is desirable, and one of the primary further advantages of this current invention, to provide improved means for reducing the creation and release of deleterious exhaust of other gases, either in the form of carbon monoxide, or nitrogen dioxide, that is discharged during the gas combustion. The improved heater of this design substantially reduces to a minimum the generation of the deleterious types of combustion by-products that may be directed into the space being heated, and certainly functions to alleviate the likelihood that any persons therein may be harmed through the breathing of such noxious gases over a sustained period of time. Direct gas-fired heaters typically are constructed to a variety of configurations. In the majority of such heaters, as manufactured, the burner is arranged upstream of the fan inlet, and which functions in the manner of the draw-through type of arrangement. A lesser number of other manufacturers position their burner downstream of the fan or blower discharge, in what is defined as a blow-through configuration. An example of the latter can best be seen in the U.S. Pat. No. 3,630,499, which is owned by a common assignee of the improved burner of the current design.
Other types of burner arrangements that exists in the prior art can be readily seen in the Ehrich U.S. Pat. No. 3,485,043; Coppin et al U.S. Pat. No. 4,573,907; in the Childs U.S. Pat. No. 3,993,449; in addition to the Pillard U.S. Pat. No. 3,885,919. Also Canadian Pat. No. 560,916 to Kind shows a form of gas burner contained within a heating arrangement which incorporates a flame zone of a combustion chamber.
In addition, other burner assemblies are shown in the prior U.S. Patent to Lewis, U.S. Pat. No. 4,523,905; the patent to Coppin, U.S. Pat. No. 4,869,665; and Kikutani, et al U.S. Pat. No. 4,610,626.
As is well known in this art, the performance characteristics of the burner necessarily determines the operational range of the heating equipment, when tested to guage whether it is in compliance with various requirements of the American National Standards Institute (ANSI), governing the functioning of the direct gas-fired industrial air heater, of the type described in accordance with this invention. The burner design for which this patent protection is sought herein utilized in the industrial heating appliance, such as the identified direct gas-fired make-up air heaters and direct gas-fired industrial air heaters. This design may also be utilized in industrial process equipment, such as ovens or dryers. These appliance standards that exist for this type of equipment, when it is utilized for providing tempered replacement air as in a make-up air application or for providing space heating to overcome the heat loss in industrial buildings, are regulated by standards, and two such standards which are generally reference by building code authorities are the ANSI standard Z83.4 for the direct gas-fired make-up air heaters, and the ANSI standard Z83.18, for direct gas-fired industrial air heaters. These standards establish the criterian for the maximum increase allowed through the heater for the by-products of combustion, such as the carbon monoxide, nitrogen dioxide, carbon dioxide, and aldehydes. Obviously, such limits are imposed for the purpose of regulating the air supply of the facility where the equipment is to be installed, for the safety of the workers, and others, subject to such type of heating conditions. Generally the air flow through a heater of this type design, and the temperature rise that occurs for the air that is being heated, determines the heating capacity of the subject unit. The airflow is directly related to the fan as selected, the motor horsepower of the unit driving the fan, and the static pressure on the system during its functioning. The temperature rise is controlled by the gas flow delivered to the burner, at the given air flow rate for the capacity of the air that has been drawn through the unit, as induced by the blower.
As previously explained, the ANSI standards generally provide an industrial self regulation of the minimum requirements that must be met by units of this design. These standards generally allow for specific maximum additive levels of four particular by-products of combustion, as previously identified, that may be released from the heating unit of this type during its functioning. These products of combustion as previously explained, and their respective allowable levels are as follows:
Carbon dioxide, 4,000 parts per million (ppm);
Carbon monoxide, 5 parts per million (ppm);
Nitrogen dioxide, 0.50 parts per million (ppm); and
Aliphatic aldehydes, 1.0 parts per million (ppm).
The allowable rise concentration through the heater for carbon monoxide is this 5 ppm, and for nitrogen dioxide is 0.5 ppm. As can be understood, these are extremely small levels of elevation, and therefore, it is very important that a burner of this design be very efficiently and effectively designed, for the purpose of minimizing the derivation of these combustion by-products. These particular derived deleterious chemical compounds, which are generally recognized in the trade as undesirable by-products from the functioning of heating units of this type, and their gases of combustion, are basically recognized as unwanted derivatives, which, if they can be reduced to an absolute minimum, not only adds to the safety of all people within the heated space, but enhances the quality operations of the heating unit, as designed. The unit of this particular invention has been designed to provide for a minimization of the output of these undesirable compounds, through the unique enhanced design of particular characteristics and features constructed into the improved heater of this invention, to attain such desirable results.
In recent years, changes to the ANSI standards have been adopted as part of the standards harmonization effort between the U.S. and Canada associated with the North American Free Trade Agreement (NAFTA). The results of these changes have tended to make the requirements of the standard more stringent. The combustion levels have remained the same for the U.S. as before, however, the Canadian levels for combustion by-products for CO and NO
2
are half of the previously allowed levels. More significantly for the U.S. manufacturer's is the operating points at which combustion testing has been conducted has shifted from the ideal operating point as defined by the manufacturer to the extreme end of the possible operating range of the heater as defined by the controls provided by the manufacturers.
Jones James R.
Potter Gary J.
Cambridge Engineering, Inc.
Denk Paul M
Price Carl D.
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