Chilled Beam - Physics

Physics

Water can carry significantly more energy than air. Although 1 cubic foot (0.028 m3) of air has a capacity to hold heat of 37 joules per kelvin (JK−1), water has a heat capacity of 20,050 JK−1. A metal pipe of water just 1 inch (2.5 cm) in diameter can carry as much energy as an 18-by-18-inch (46 by 46 cm) metal duct of air. This means that chilled beam HVAC systems require much less energy to provide the same heating and cooling effect as a traditional air HVAC system.

Chilled beam cooling systems require water to be treated by heating and cooling systems. Generally, water in a passive chilled beam system is cooled to about 16 to 19 °C (61 to 66 °F). In active chilled beam heating systems, water temperature is usually 40 to 50 °C (104 to 122 °F). (Chilled beam heating systems usually cannot rely solely on convection, however, and often require a fan-driven primary air circulation system to force the warmer air to the ground where most people sit and work.) There are effectiveness and cost differences between the two systems. Passive chilled beam systems can supply about 5.6 to 6.5 watts per foot (60 to 70 watts per metre) of cooling capacity. Active chilled beam systems are about twice as effective. In both cases, convection is so efficient that the ratio of incoming air to heated/cooled air can be as high as 6:1. However, studies of the energy cost-savings of active versus passive chilled beam systems remained inconclusive as of 2007, and appear to be highly dependent on the specific building.

The active chilled beam system employs fins to help heat and cool. Active chilled beam systems are effective to the point where outdoor air can be mixed with the indoor air without any traditional air conditioning (such as heating, cooling, humidifying, or dehumidifying), thus enabling a building to meet its "minimum outdoor air" air quality requirement.