Natural gas infrared heating
Certain indoor and outdoor spaces require heat, and convective heat solutions are not ideal, or perhaps don’t work at all. The best solution is often natural gas-powered infrared heaters, either of the heated tube type, or high intensity panels. These systems put the heat on the surfaces and the people that occupy the spaces, without attempting to heat room air directly.
A good fit
Whether it’s an athletic fieldhouse or an industrial warehouse, a hospital lobby or a manufacturing area, some building locations are just plain difficult to make comfortable for their occupants. Or at least they are difficult if the design is limited to convective heat. But infrared is a different answer, and one that is often the best choice.
For many decades, building comfort experts have understood that gas-fired infrared had this great potential. Today’s infrared designs are more efficient and effective than ever. Current designs can convert up to 80% of the input energy into infrared heat that is directed at the space occupants.
Tube and reflector
One of the types of infrared heat that is used most often is a heated tube system. These have specialized burners that fire into long horizontal tubes. The tubes absorb energy from the long flame and reflect a large amount of it as infrared heat. The tube is typically made in a dark color to maximize heat absorption and re-radiation. The system uses a polished metal reflector behind the tube to direct the infrared energy toward the heated area. Design of the reflector is such as to minimize reflection back onto the tube and maximize the outward pattern.
Jim McLellan is Vice President, Sales for Schwank USA, Inc., a major provider of a range of gas infrared heating devices. He emphasizes that infrared is the best solution for areas that are otherwise difficult to heat — high ceilings, open to the outside, or lots of outside air movement. He notes, "These are applications where gas-fired infrared technology really shines. Infrared heat requires no mechanical means or distribution ductwork to move the heat to the floor areas where it is required. Apply the correct infrared heaters in a high ceiling or open air area and you can provide comfort from heaters mounted as high as 180 feet above the surface."
Widely used in school and government facilities
He notes that in educational facilities, Schwank infrared heaters are widely used to improve comfort in school gymnasiums and similar open spaces. In technical schools, they are used in areas for hands-on training in plumbing, air conditioning and auto mechanics. "Military and government facilities are using infrared to meet mandated energy reduction targets and this has proven very successful. Examples include aircraft hangars, large warehouse and distribution facilities, transportation maintenance buildings, airport baggage handling areas, and many more."
McLellan explains that gas-fired infrared heaters sold in the U.S. and Canada are required to produce a minimum of 35% of their input energy as radiant energy — the portion that will heat surfaces and floor space. He says, "Although 35% does not sound like a very good energy conversion, it is more effective than other technologies such as warm air." This efficiency might be typical of an "entry level" infrared system, and Schwank also offers the ultraSchwank tube heaters that are 60+% radiant efficient with fully insulated reflectors and a very efficient combustion technology.
Popular for athletic facilities
McLellan notes that Schwank heaters are widely used in stadiums and practice facilities at the college and professional level for soccer, football and hockey, and for outdoor venues for concerts, bars, restaurants and beer gardens. Infrared heat can extend the usable season for many of these facilities in cold climate areas. The U.S. Army Corps of Engineers recently approved the use of ultraSchwank technology for a large heating upgrade project for the Defense Logistics Agency at Tinker Air Force Base in Oklahoma.
Pamela Davis from Schwank USA was recently a presenter at a Technology Market Assessment Forum sponsored by the Energy Solutions Center. She pointed out that other advantages of infrared as compared with convective systems is that there are no dust swirls or drafts, such as may happen with blown hot air. She also explained that with infrared, the recovery times after doors are opened is very short, and the system helps maintain warm floors, which is a great advantage for workers such as mechanics and for spectators in sports facilities.
Recent improvements in efficiency
Tim Seel is the North American Sales Manager for Superior Radiant Products, another major provider of a range of gas-fired infrared heating products. He remarks on the progress that has been made in recent decades in infrared heating design. He points out that early infrared tube heaters used burners that were simply adapted from boiler burners. "Flame shapes were not ideal for small diameter tubes. In more modern times, manufacturers have applied technology in burner designs to create more ideal flame shapes for tubing." Flame shape is important to achieve maximum radiance for the entire length of the tube.
Seel notes that a European test method, EN419, is commonly used to measure direct infrared outputs. However, he also mentions that IR efficiency by itself does not make an installation successful. "Consideration of IR efficiency, thermal efficiency, distribution, and the application itself contribute to successful installations and large fuel savings." He emphasizes that the maintenance of infrared systems is moderate, but should include periodically removing dust in blowers, monitoring tube condition, and maintaining design installation conditions.
In the industrial world
In industrial applications, infrared tube heaters are widely used in warehouses, distribution centers, loading docks, and in open industrial areas that require high levels of ventilation. Often they are installed in zoned systems so they can be operated only when spaces are occupied, thus conserving energy.
The gas-fired tube infrared heaters are the most widely used type, but there are also high-intensity infrared panels which provide a concentrated source of infrared heat for certain locations. According to Seel, high intensity units must be vented per NFPA 54. He says, "Because they have a concentrated pattern of energy output (think of them as ‘spotlights’), they are most effective when high energy density is needed. Most high intensity units do not do well in outdoors where wind and rain can affect flame stability, hence they are usually shielded by overhangs, etc. However, some models have provisions built in to provide stability in an outdoor environment."
Consulting services from manufacturers
Schwank USA, Superior Radiant, and other manufacturers offer consulting services to assist in sizing, selection and placement of infrared tubes and panels to maximize comfort and efficiency. If your facility has problems areas for convective heating, gas-fired infrared may be the ideal solution.
This article originally appeared in the Gas Technology Summer 2016 issue.