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Displacement ventilation is best suited for taller spaces (higher than 3 meters [10 feet]). [2] Standard mixing ventilation may be better suited for smaller spaces where air quality is not as great a concern, such as single-occupant offices, and where the room height is not tall (e.g., lower than 2.3 meters [7.5 feet]).
During winter months, for example, an air conditioning register can be closed to prevent cold air from being pulled from the room. This allows the hot air to mix more completely with the cold air in the room, improving the efficiency of the HVAC system. [7] (The return should be efficient enough to draw off the cooler air.) [10] [11]
Supply diffusers in the ceiling are fed by fan coil units in the ceiling void or by air handling units in a remote plant room. The fan coil or handling unit takes in return air from the ceiling void and mix this with fresh air and cool, or heat it, as required to achieve the room design conditions. This arrangement is known as 'conventional ...
A duct with less than 0.75 mg/100m 2 is considered to be clean, per the NADCA standard. [7] A Hong Kong standard lists surface deposit limits of 1g/m 2 for supply and return ducts and 6g/m 2 for exhaust ducts, or a maximum deposit thickness of 60 μm in supply and return ducts, and 180 μm for exhaust ducts. [8]
Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality .
When tubes are used for these purposes they may be 10'-6" to 12 foot diameter, and up to 250 foot long, using up to 1/2" plate and ovaling ring stiffeners at 8 foot (to 20 foot centers). On one such project My firm added L8x8x3/4 at the top 45 degree location to stiffen the plate near the point of maximum stress for tubes (as per Timoshenko ...
Air returns from the room at ceiling level or the maximum allowable height above the occupied zone. [1] The UFAD system takes advantage of the thermal plume and stratification phenomenon: the conditioned air is supplied directly to the occupied zone (OZ). The thermal plumes generated by the occupants and other heat sources introduce the ...
[15] [16] For example, to maintain a 15 °C temperature in a certain dwelling about 3.0 kW of heating are required at 0 ACH (no heat loss due to warmed air leaving the dwelling, instead heat is lost due to conduction or radiation), 3.8 kW at 1 ACH and 4.5 kW are required at 2 ACH. [15]