UV irradiation of air handlers and other apparatus

Details UV irradiation of air handlers and other apparatus UV irradiation of air handlers and other apparatus

2002-08-19

2003-09-30

Gulakowski, Randy (Department: 1746)

Cleaning and liquid contact with solids

Processes

Including application of electrical radiant or wave energy...

C422S024000, C422S121000, C062S078000, C250S454110, C065S095000

Reexamination Certificate

active

06627000

ABSTRACT:

NOTICE OF COPYRIGHTS AND TRADE DRESS
A portion of the disclosure of this patent document contains material which is subject to copyright protection. This patent document may show and/or describe matter which is or may become trade dress of the owner. The copyright and trade dress owner has no objection to the facsimile reproduction by any one of the patent disclosure as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright and trade dress rights whatsoever.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the reduction of energy usage in cooling and heating systems and more particularly to minimizing air horsepower and maximizing the operating performance of heat exchangers in cooling and heating systems.
2. Description of Related Art
One mature industry that is economically sensitive to costs is the heating, ventilation and air conditioning (HVAC) industry. Because of the competitive nature of both the construction and HVAC industries, HVAC systems must be inexpensive to install. Of a more global interest though, is the cost to operate and maintain HVAC systems. Often, a building owner will replace an aging HVAC system as the reduction in operating and maintenance costs can offset the retrofit cost, sometimes in a matter of months.
Broad social and energy policies also favor more efficient HVAC systems. In these days of electricity deregulation and conservation, it has become even more important to conserve energy consumption. Recently, entire electrical grids have shut down on very hot days in part because of the huge demand of HVAC systems running at extreme capacity. Furthermore, energy conservation translates directly into improved environmental conditions and decreased reliance upon foreign petroleum.
HVAC systems are typically comprised of fans and ductwork for moving air where needed. An HVAC system will include a cooling and heating section for, respectively, cooling and heating the air. In most HVAC systems, air is drawn in, filtered, cooled and dehumidified or heated and humidified, and then delivered to a room. The greatest portion of this air is drawn from the conditioned space for recirculation through the HVAC system. Considerable effort has been made to make these components more efficient.
One of several recently used methods of saving energy in an HVAC system includes the use of variable frequency drives on any motor used in a HVAC system. When and if the system load decreases, this can be sensed and the motors in the HVAC system will be slowed to an equilibrium value to save motor energy consumption. Another method is to reduce the design amount of outdoor air to eliminate having to condition it. Another method is an economizer cycle that utilizes 100% outdoor air when its ambient temperature is suitable for cooling the space. Another method is to replace aging equipment with newer and more efficient equipment.
One other factor impacting design and operation of HVAC systems is indoor air quality (IAQ). One major factor in IAQ today is the amount of outdoor air introduced into an otherwise sealed space serviced by an HVAC system. The HVAC industry has adapted standards for the introduction of outdoor air into spaces serviced by an otherwise closed HVAC system. These include offices, residential, commercial, industrial and institutional spaces, as well as the interior of vehicles such as cars, buses, planes and ships. In addition to controlling indoor air for occupant comfort, the goal of HVAC systems is to provide air with reduced levels of particulates, gases and bioaerosols, be it for semiconductor, pharmaceutical or food processing facilities, hospitals, schools or offices and now the home.
Most ventilation systems today include a cooling section. The cooling section includes a type of heat exchanger typically referred to as a “cooling coil,” through which air is forced and cooled. This cooling coil operates thermodynamically to remove both sensible and latent heat from the forced air. Cooling coils typically are made using aluminum fins over refrigerant tubes which have been formed into a desired shape. Essentially the same coil arrangement in used in all cooling systems, whether in HVAC systems for occupied spaces, or for refrigerators and freezers.
A similar configuration is often used in heating sections, though the thermodynamic operation is opposite to that in a cooling section. The heat exchanger of a heating section often comprises a coil, and water of an elevated temperature passes through the coil. The heating coil is fashioned in a manner to promote heat transfer from the water to the heating coil. The heating coil is further fashioned to promote heat transfer from the heating coil to air which is forced across and through the heating coil.
As a normal consequence of the process of cooling air, several things occur. One is that humidity (latent heat) is removed from the air. This moisture collects on the coil fins and/or anything else nearby which is below dew point, including the ductwork. Typically, a drain pan is positioned below a cooling coil. The collected moisture runs down the fins and into the drain pan under the force of gravity. Water which collects in the drain pan flows away through a drain pipe equipped with a trap.
Another is that organic matter deposits and collects on the cooling coil fins from the air passing over them. Though the fins of the cooling coil appear to be smooth, in fact, when viewed under a microscope, they can be seen to have an irregular and somewhat pitted surface. The organic matter can therefore adhere easily to the damp and rough surface of the cooling coil.
Another consequence is that the cooling section is dark and at off times, it will be warm. Though when operating it will be quite cold, the cooling section will have varying cycles of cooling. When not cooling, the cooling coils typically reach room temperature.
Similar effects are encountered with heating coils, though typically to a lesser degree than with cooling coils.
Altogether, these consequences produce an environment in which molds and bacteria can grow and thrive. Over time, a heat exchanger can become near fully encrusted with microorganism activity bound to an organic substrate. The drain and drain pans also become a growth environment for mold and bacteria. The spores and products of metabolism from both are easily entrained into the airstream.
As this matter encrusts a heat exchanger, its heat exchange efficiency is compromised. The efficiency reduction does not result in an energy reduction. Instead, in the case of a cooling coil, the cooling coil must be made to be cooler or run longer, both of which require more energy for the same unit of work. In the case of a heating coil, the heating coil must be made to be hotter or run longer, both of which require more energy for the same unit of work. Furthermore, more energy is required to push air across the encrusted heat exchanger, resulting in an increased pressure drop. Therefore, either the fan speed must be increased, the motor horsepower increased, or both, or an oversized fan and motor are installed. Pressure drop and heat exchange efficiency can degrade up to 30% of their original values in as little as one year, on average 22% in three years. There is an exponential increase in energy consumption to the linear degradation of HVAC system heat exchange efficiency and airflow. A 30% degradation can equate to a doubling of energy use when these other remedial measures are used.
The conventional method of controlling the accumulation and growth of substrate and microorganisms is with the use of high pressure sprayers, surfactants, acids and biocidal agents, which are applied to all growth surfaces of the HVAC system. However, the surfactants, acids and biocidal agents are dangerous chemicals and the distribution and use of biocidal agents and acids are strictly controlled by the Environmental Protection Agency (EPA). In this age of workplace safety, there is worry not only for the occupan

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