Why is there an air blower at almost every mall/ department store entry?
An air door or air curtain is a device used to prevent air or contaminants from moving from one open space to another. The most common use is a downward-facing blower fan mounted over an entrance to a building, or an opening between two spaces conditioned at different temperatures. The basic requirement is that the fan must be powerful enough to generate a jet of air that can reach the floor. Air doors are often used where doors are required to stay open for operational purposes, such as at loading docks and vehicle entrances or even malls. They can be intended to help keep flying insects out by creating forceful turbulence, or help keep out outside air, thus reducing infiltration through the opening. Also, since most malls are air conditioned air curtains help to stop the flow of cold air outside while entrance is still open. Cold drafts can be avoided by mixing in warm air heated by the air door. Heated air doors are commonly used when supplemental heat is needed for a space, and to reduce the wind chill factor across the opening in colder climates.Further applications include customer entryways, airplane hangars, cargo doors, drive through windows, restaurant doors, or shipping receiving doors. Non-heated air curtains are often used in conjunction cold storage and refrigerated rooms. Source: Wikipedia
What are the advantages of a round duct over a rectangular duct?
Air flow is calculated to provide specific amounts of airflow. This can be challenging due to space limitations. Sometimes you need to move a lot of air through a small space. Rectangular duct can be sized taking full advantage of the all space available. Think of putting a round peg in a square hole. The square duct uses all the available space for air flow. If ceilings have limited space a shallow but wide duct can be built to allow the correct amount of air in the reduced space. Rectangular duct has to be carefully designed because is is subject to collapse due to clogged filters etc in the line. The reduced pressure can implode the sides. The opposite is also true as the supplies can expand and round out the sides.Round ducts are easy to build and come in predetermined sizes and metal thicknesses. If the space is available it is the cheapest way to go because it can be mass produced and cut to size in the field. All the conceivable transitions are available off the shelf. So overall if the biggest concern is cost, and it always is, the round duct is a cheaper choice where possible. They are much stronger in high static and low pressure conditions thus reducing the fear of collapse as discussed in the previous paragraph.Often in commercial design systems the main ducts are rectangular and branch ducts are round allowing the maximum air flow to the branches. But not always. Some are rectangular throughout with 6′ flex connectors to the grilles and registers. Value engineering will often change as much as possible to round. Most large mechanical contractors will re-design a system and submit their bids accordingly.
WHAT are aqueducts?! How do they work?!?
The ancient ones DO look like bridges, don't they? Aqua- is Latin for "water." -Duct is a tunnel, or trough, or ditch that is used to convey a fluid from one place to another as the ducts in a home's heating/cooling system carry warm (or cool) air to various parts of a home or office. I'm sure we've all been stuck under an Air Conditioning duct in a restaurant that froze us! As far as the force that moves the water: in Rome it was just gravity! There were pumps for moving water up into a house's cistern (a water tank), but they were small, and not efficient. Water was moved from the Alps all the way to Rome using nothing but gravity. If you put the words "Roman aqueducts" into the Y'Search____Web Search box at the top of this page, it'll yield nearly 140,000 links.
How can you reduce blower noise?
How can you reduce blower noise?Thanks Avdesh Tyagi (अवधेश त्यागी) for asking this question.Blowers are those machines designed to move the air using a specific ratio between 1.11 to 1.20. While fans are those who work with a specific ratio is upto 1.11.Blowers operate at static pressures between 1136 to 2066 mm of wg while, fans operate with a static less than 1136 mm of wg.I think you meant fans when you asked this question. Do correct me if I am wrong. Will appreciate.Generally, the noise created by fan is dependent on its outlet velocity of air, size of the ducts entering or leaving the fan and design static pressure.Higher the outlet velocity of the air, higher the noise. So, you may select the fan suiting your needs with air velocity prescribed for your application. For example, in low pressure air conditioning for comfort application, the velocity of air at the outlet of the fan through the duct needs to be within 1200 to 1800 FPM. Select the fan with a velocity suiting this outlet velocity.Most of the times, it happens that the selected static pressure is ridiculously high or at least too high than the needed levels of total static pressure. Therefore, it is essential to calculate the correct static pressure based on your ducting drawing. If the actual static pressure is way below the actual static pressure, then the velocity of air through the duct will be beyond the required limits, generating undesirable noise and noise beyond permissible limits.If the noise is being observed in an operating equipment, which was hitherto operating with absolutely no issues satisfactorily, then the fan operation must be closely observed. It might be that there are things missed out during maintenance or the bearing might have worn out or the belt might have loosened, or a slab of acoustic insulation/ guide vane might have detached itself from within the duct surface obstructing the air flow or some other reason which can only be seen at the site of operation. In such cases, one needs to arrest the root cause to resolve the problem at hand.
What is the difference between package type air conditioner and central air conditioner?
There are two types of Packaged Machine:Roof top packaged unitPackaged Unit.Roof top packaged:Evaporator coils and fans, condenser coils and fans, expansion device and compressor are inbuilt in the unit and it often comes in capacities ranging from 11TR - 40 TR. The entire unit is weather proof and located on the roof of the building. Ducts can be used to carry the conditioned air to and from the unit. The main advantage of the unit is reduced installation efforts since everything except duct and air terminals is factory assembled.Packaged Unit:It can be separated as Indoor unit and Outdoor unit. Indoor unit contains evaporator coils and fans, expansion device and compressor. Outdoor unit contains condenser coil and fans. This unit comes in the range of 5 TR - 20 TR. The advantage of the packaged unit compared with split machines are higher capacities ducting can be done to cater multiple rooms.Advantage of packaged machine compared with roof top packaged machine is the reduced duct length since the indoor machine can be located within the building.Centralized air conditioners:It can be called as a single air conditioner catering to two or more rooms and it is controlled and monitored from a central location. It can be either direct expansion type (DX) of Chilled Water type. In most of the cases these machines are located in Air Handling Unit room (AHU room) very near to the area to be conditioned and connected either with chiller or with DX outdoor unit through pipes.Single packaged machine or multiple packaged machine combined together to act as an centralized air conditioner.
What is the difference between the ductable split units and the packaged air conditioning system in HVAC?
Split-system central air conditioner has 3 components:an outdoor metal cabinet that contains the condenser and compressoran indoor cabinet that contains the evaporator coilan air handler that sends the cool air through the duct systemPackaged central air conditioner:evaporator coil, condenser, and compressor all located in one cabinetmost of the time placed on the roof or a concrete slab next to your building’s foundationusually located outside, packaged air conditioners, have air supply & return ducts coming form inside going through the wall or roofing to connect with the unitBasically:As the name implies split air conditioners have two parts. one outside another insidePackaged: all in one machine that is outside connected to the house. Placed on the roof or somewhere outside near the base