Heating systems – Heat radiators
Reexamination Certificate
2003-02-28
2004-09-07
Boles, Derek S. (Department: 3749)
Heating systems
Heat radiators
C237S01230C, C431S012000
Reexamination Certificate
active
06786422
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to heating assemblies and, more particularly, to an infrared vacuum type heating assembly.
2. Description of the Prior Art
It is known to heat a specific location in a building or home with “forced air” systems. The forced air systems typically refer to hot air “box” heaters that force the heated air by blowing warm air over a heat exchanger and “forcing” it downward to heat an area.
It is also known to utilize radiant or infrared heating assemblies or systems to provide beat to a specific location in a building such as a warehouse, factories, aircraft hangars and the like. Radiant and infrared heating assemblies of the prior art range from hot-water pipes embedded in the floor or ceiling of a structure, to warm-air ducts embedded in the floor, to some form of electrical resistance panels applied to ceilings or walls, to other radiant and infrared heating assemblies, such as that described in U.S. Reissue Pat. No. 37,636. Panel heating is a form of radiant heating characterized by very large radiant surfaces maintained at modestly warm temperatures. With many such assemblies there is no visible heating equipment within the structure, which is an advantage in decorating. A disadvantage is the extent to which a ceiling or floor might be ruined in case of corroded or faulty hot-water piping where this method is employed.
Infrared heating assemblies have considerable benefits over conventional heating assemblies because they are more efficient and “cleaner” than other heating assemblies, thereby reducing fuel consumption and atmospheric pollution. A gas-fired infrared heating assembly emulates the efficiency of the sun. Like the sun, infrared heating assemblies generate radiant energy that is converted into heat when absorbed by objects in its path. Once the infrared energy is absorbed by floors, machinery, stock and people, it is then re-radiated to warm the surrounding air. In contrast, forced air systems simply move hot air around and waste warmth at the ceiling levels and through frequently opened doors. By directing the warning rays to the lower levels, an infrared heating assembly will provide precise control of the environment in the facility while creating pleasant working conditions for employees.
As originally conceived, such infrared heating assemblies employed a porous ceramic mat as the heating element. Fuel gas was passed through the pores of the mat and burned at the outer surface, causing the mat to heat up and emit infrared radiation. Infrared heating assemblies were further developed in which a fuel is burned in a combustion chamber and the products of combustion are conducted through an elongated conduit to cause the conduit to be heated and emit infrared radiation. The conduit is typically not heated to the point of emitting visible light.
In one example of these infrared heating assemblies, a closed loop circuit is employed in which the combustion products are re-circulated through the heating conduit to eliminate the need to heat air from ambient temperatures up to combustion temperatures, and thus improve the heat efficiency of the assembly. However, infrared heating assemblies of this type are complex and expensive to install. Further, the heat capacity of the air is small such that there is little practical value to such infrared heating assemblies.
Other infrared heating assemblies employ a single-pass concept in which the combustion gases arc not recycled, but are exhausted from the heating conduit to the atmosphere either directly or through a stack. One type of single-pass heating assembly includes a single atmospheric burner which utilizes the natural buoyancy of hot combustion gases to draw combustion air into a burner. Other types of the single-pass heating assemblies utilize some means to induce the flow of combustion gas through the heating conduit. In particular, a “push assembly” incorporates a blower mounted at an inlet of the heating conduit and positive pressure is used to force a flame down a conduit. The infrared heating assembly disclosed in U.S. Reissue Pat. No. 37,636 incorporates such a pushing blower. Alternatively, an exhaust fan can be mounted at an outlet of the heating conduit that draws the combustion gases through the conduit. This type of infrared heating assembly is known as a vacuum type heating assembly or “pull assembly”. Vacuum type heating assemblies, or “pull assemblies”, are gas-fired infrared heaters that use negative pressure to draw a flame down the heating conduit. Vacuum type heating assemblies are desirable in the industry because of the perceived safety factors associated with negative pressure assemblies, increased venting options and potentially improved thermal efficiencies. In addition, the use of vacuum type heating assemblies provide a simplified centralized control assembly, and the number of vent penetrations may be reduced.
The vacuum type heating assemblies can have single or multiple burners within the same heating conduit, and generally provide the longest heat exchanger lengths. Heating assemblies of this type are typically of a pre-mix configuration, mixing air and gas as completely as possible before ignition. This is particularly critical when using multiple burners, as better mixing is required to avoid difficulties of combustion contamination at downstream burner locations.
Conventional vacuum type heating assemblies include four to six burners in line for smaller firing rates or two to three burners in line for larger firing rates. The burners operate in series relative to one another along a length of the heating conduit.
In designing these assemblies, consideration is given to the overall flow volume relationships and the capacity of a vacuum fan or pump that provides negative pressure on the entire network of heating conduits. Conduit lengths vary according to selected heating requirements and desired thermal efficiency, with longer lengths of conduits providing higher thermal efficiency and a wider heating distribution area. Each burner is equipped with fuel and air orifices in a proportion required for acceptable combustion. The vacuum fan or pump at an end of the heating assembly establishes a negative pressure at each burner that determines the fuel and airflow rate through each burner. The vacuum fan further draws combusted gases to an outlet for proper emission of combusted gases.
The laws of physics for fluid flow dictate that for a given vacuum setting, each burner in a multiple burner experiences a different vacuum level. More particularly, the negative pressure differential or vacuum experienced by a burner closer to the vacuum fan is greater than the burner further from the vacuum fan. Therefore, and contrary to forced air assemblies, burners in a vacuum system must be balanced to equal pressures. Accordingly, burner size is limited due to unacceptable combustion conditions caused by increasing vacuum or negative pressure differential along the length of the heating conduit toward the vacuum fan.
Furthermore, conventional vacuum type heating assemblies have not provided multiple temperature settings, also known as demand heating. In other words, the conventional vacuum type heating assemblies do not have the capability of two-stage heating or temperature settings such that the fuel regulator and burner or burners are operating at different fuel pressures. Two-stage heating is particularly advantageous in that it reduces the number of on/off cycles for the heating assembly. Further, the heating assembly is operating the majority of the time in a low heating mode which provides significant fuel savings and improved comfort levels.
Accordingly, it would be desirable to develop a heating assembly which utilizes the advantages attendant to a vacuum heating system and a two-stage heating assembly while avoiding the deficiencies.
SUMMARY OF THE INVENTION AND ADVANTAGES
A heating assembly for variably heating ambient air. The heating assembly comprises an elongated heating conduit having an inlet
Fleet Donald Scott
Wortman Joseph B.
Boles Derek S.
Detroit Radiant Products Co.
Howard & Howard
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