A cold beam is a type of convection HVAC system designed to heat or cool large buildings. The water pipe is passed through a "beam" (heat exchanger) that is integrated into a standard suspended ceiling system or depends on a short distance from the ceiling. As the rays shiver the air around it, the air becomes more solid and falls to the floor. Replaced by warm air that moves up from below, causing a constant flow of convection and cooling the room. Heating works in almost the same way, similar to a steam radiator. There are two types of cold beams. Some passive species rely solely on convection, while there is a convective "convective" type of passive that cools through a combination of luminous exchange (40%) and convection (60%). The passive approach can provide a higher thermal comfort level, while the active type (also called "induction diffuser") uses air velocity at a relatively high velocity to induce air circulation through the unit (thereby increasing heating and cooling capacity).
Cold rays can be distinguished from cold ceilings. The cold ceiling uses water flowing through pipes like cold blocks; However, the pipes in the cold ceiling are behind the metal ceiling plate, and the heated or cooled plates are the cause of the convection and not the pipe unit itself. Cold beams are about 85 percent more effective on convection than cold ceilings. The cold ceiling should cover a relatively large ceiling area as it provides heating and cooling mainly by heat emitting, rather than convective, heat transfer.
Video Chilled beam
Physics
Water can carry much greater energy than air. Although 1 cubic foot (0.028 m 3 ) air has a capacity to withstand heat of 37 joules per kelvin (JK -1 ), the same water volume has a heat capacity of 20,050 JK < soup> -1 . A water pipe of metal with a diameter of only 1 inch (2.5 cm) can carry energy as much as an 18-by-18-inch (46 x 46 cm) metal duct. This means that cold beam HVAC systems require less energy to provide the same heating and cooling effects as traditional air HVAC systems.
Cooler cooling system requires water to be treated with heating and cooling systems. Generally, water in a passive cold beam system is cooled to about 16 to 19 ° C (61 to 66 ° F). In an active cold beam heating system, the water temperature is usually 40 to 50 ° C (104 ° to 122 ° F). (Cold-light heating systems typically can not rely solely on convection, however, and often require a fan-driven main air circulation system to force warmer air to the ground where most people sit and work.) There is a cost effectiveness and difference between the two. system. The passive cold block system can supply about 5.6 to 6.5 â € <â € An active cold beam system uses fins to help heat and cold. The active cold beam system is effective for the point where outside air can be mixed with indoor air without traditional air conditioning (such as heating, cooling, moisturizing, or dehumidifying), enabling buildings to meet minimum "outdoor air" quality requirements. Maps Chilled beam
Advantages and disadvantages
The main advantage of cold beam system is its lower operating cost. For example, because the cooled water temperature is higher than the cooled air temperature, but provides the same cooling capability, the cooling water system cost is lower. Because cooling and heating air are no longer associated with air shipping, the building also saves money by being able to run fewer air circulation fans and at lower speeds. One estimate puts the amount of air handled at 25 to 50 percent less using a cold beam system. By being able to target cleaner outside air delivery where needed (rather than injecting it into the entire system and heating or cooling it), there is a reduced need to treat large amounts of outdoor air (also saving money). In one case, the Genomic Science Building at the University of North Carolina at Chapel Hill lowered the HVAC cost by 20 percent with an active cold beam system. This is a typical energy cost savings. The cold beam system also has some advantages as it is almost noiseless, takes little care, and is very efficient. The traditional fan-driven HVAC system creates a higher airspeed, which some consider uncomfortable. HVAC cold beam systems also require less ceiling space than forced air HVAC systems, which can lead to lower building altitudes and higher ceilings. Because they do not require high forced airflow, cold beam systems also require less airway distribution networks (which also help lower costs).
The cold beam system is not a panacea. Additional ductwork may be required to meet minimum outdoor air requirements. Both types of cold beam systems are less effective in heating than cooling, and additional heating systems are often needed. The cold beam system can not be used alone in buildings where the ceiling is higher than 2.7 meters (8.9 feet), because the air will not circulate properly. The forced air circulation system should be used in such cases. If the water temperature is too low or high humidity, condensation in the rays can occur - leading to a problem known as "internal rain." (In some cases, the dryer outer air can be mixed with the wet interior to reduce the humidity level of the interior while maintaining system performance.) Cold beam systems are not recommended for areas with high humidity (such as theater, gymnasium, or cafeteria). Because they are less effective in cooling, passive cold block systems are generally unsuitable for tropical and tropical climates. Hospitals generally can not use cold beam systems because of restrictions using recirculated air. Cold beam systems are also known to cause visible air circulation which can make some people uncomfortable. (A passive air deflection device can help disrupt this air pattern, reducing the problem.) Some designers find that enlarging the channel around the active cold beam system to improve air circulation causes echoes in the work area and amplifies the sound of water moving through the pipe to a noticeable level.
Installation and adoption
Active cold beams are mounted on a suspended ceiling and then anchored to the top structure, because the T-bar ceiling can not support the typical operating weight of the cold beam. They are generally 1 to 2 feet (0.30-0.61 m) wide, and require less than 1 foot (0.30 m) of overhead space. A 2-foot wide (0.61 m) wide beam system generally weighs about 15 pounds (6.8 kg) per 1 foot (0.30 m) beam length. Cold beams are generally installed so that the center of each beam is not more than 3 meters (9.8 ft) from the center of the next beam. Some architects and end users dislike beams because they do not cover the entire ceiling so that channels, cables, and other infrastructure can be seen. Some designers have installed a cold beam system around the perimeter of the building (where the temperature difference could be the largest) and the other on the inside of the building, to better control the temperature across the structure. Higher system performance can be obtained by increasing the air static pressure inside the building. This system generally requires a little cleaning (vacuuming and dust from the fins every five years).
In 2007, cold beam HVAC systems were used more widely in Australia and Europe than in the United States. In Australia, the system was first used in 30 The Bonds, Sydney which is the first building in Australia to rank 5 star ABGR. The cold beam HVAC system has been used at London Heathrow Terminal 5 and Constitution Center (Washington's largest private office building, D.C.). The system has also received prominent use at Harvard Business School, Wellesley College, and the American headquarters of the AstraZeneca pharmaceutical company.
The multiservice cold rays are a relatively new form of cold beam. Developed in 1996, it combines computers and power cables, lighting, motion detection sensors, and sprinklers to cold beam units. The multiservice cold was first installed in the Barclaycard building in Northampton, England, but has since been used at Lloyd's Register (London), Airbus UK (Bristol), and the Greater London Authority headquarters; Riverside House (London); Empress State Building (London); 55 Baker Street (London) and 101 New Cavendish Street (London).
Footnote
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