Ducts Classification - By size (a)Main duct system 1.Each branch is connected to the main duct 2. Most widely used (b)Seperate ducting system
- More ducting material required - More ducting space necessary + Economical solutions if : Mass produced (b)
Round ducts are used
Duct Classification- By purpose
Duct Classification- By purpose Fresh air intake duct
- The fresh air intake duct is connected to the suction side of the machine - Location of the fresh air intake port should prevent sucking in bad smell or dust - insulation might be necessary - Separate pressure system ID recommended Air exhaust duct - Pollution air is released to the outside through the air exhaust duct - The material and paint of the air exhaust duct should be selected in function of the composition of the polluted air.
Duct Classification- By purpose Fresh air intake duct - The fresh air intake duct is connected to the suction side of the machine - location of the pressure intake port should prevent sucking in bad smell of dust
ADVANTAGES ● ● ● ● ● ●
Improves the quality of air Cost savings Improve health Reduces the cost of energy Increases comfort Space saving
DISADVANTAGES ● ● ● ● ●
Skin dryness Aggravation of respiratory problems Respiratory tract infections and allergies Its high cost It requires work and complicated installations.
Pressure losses in ducts INTODUCTION . Ducts system losses are the irreversible transformation of mechanical energy into heat
. Theses losses can be divided into friction losses And dynamic losses
Pressure losses in ducts • Fluid resistance caused by friction in round ducts can be determined by use of the friction chart (based on an absolute roughness of 0.09 mm)
Dynamic losses • Dynamic losses are the results of flow disturbance caused by duct mounted equipment and fitting . These fitting include entires, exits, elbows, transitions and junctins
Air diffusers and resisters - Types
Air diffusers and resisters - Types
Air diffusers and resisters . Needs to be determined with care . To avoid drafts for the people, the diffuser should be positioned high enough . Care to avoid dew generation on the ceiling surface . Position of the lights , structuralbeams, etc, needs to be considerded
• Design procedure for supply/ return grilles . Divide the room into squares or rectangles . Each sq./rectangle to be served by one grille . Rules of thumb
W or L < 3 *H L< 1.5* W H=height of room W and L = dimensions of sq/rectangle
• Outlet velocity The permissible sound level, and as a consequence the maximum air velocity, is determined by the application db(A) 25 35 40 46 50 70
Application studio-recording room cinema-hospital-library office-school-hotel bank-public hall store-post office factory
Max. velocity(m/s) 2 3 4 5 6 10
Specialised H.V.A.C Used in Clean Room Server Hubs Operation Theatres
Why are they Specialised? • They are specialised because they require extensive care and maintenance • The HVAC system must be capable of conditioning more than double the air. However, classification alone isn’t sufficient for calculating the airflow. • The hot air from the servers is carried upward by the flow and convection effects, and thereby does not increase the temperature of other servers.
• Where as in case of operation theatres the air in the room is constantly sterilised in aorder to avoid bacteria to contaminate
Clean Room • The number of people working in the room • The airborne contamination level of a cleanroom depends largely upon the activities in the room and the personnel. • People are responsible for most of the particles generated in a cleanroom. Airborne particles, such as skin flakes, cosmetics, perfume, spittle, clothing debris (lint, fibres) and hair, are the usual suspects • Similar to people, equipment generates heat and dust. The heat gain produced by the equipment inside the cleanroom is used to determine the cooling required. • The equipment in the room, along with the product manufacturing, generate dust that must be removed with the correct amount of air.
Server Room Cooling
•
Hot air is streaming from the cooling outlets of the server racks into the room. The image below shows the SimScale pre-processing viewer
•
The hot air from the servers is carried upward by the flow and convection effects, and thereby does not increase the temperature of other servers. One can now run several “what if” scenarios to increase the efficiency of the cooling process, or to adjust the detailed layout of the servers within the room.
•
The results show that the cooling concept is working efficiently. The outgoing flow of the inlet is blocked by the server racks, and the air circulates through the gaps and in between the walls and the racks.
Operating Theatre Ventilation System Design
•
There are many types of operating theatres within hospitals and healthcare facilities – all of which require a suitable “final stage of air filtration” that is dependent on facility purpose and healthcare requirements. Air filtration options for operating theatres include individual HEPA modules, laminar flow and UCV (ultra clean ventilation) systems. This article will focus on some important design considerations relating to these air filtration options within operating theatres.
•
The fundamental function of air filtration within an operating theatre is to remove contaminants from the air, to reduce the possibility of particulate entering a wound, and ideally to provide a protective sterile zone around the wound. The ultimate aim is to reduce the risk of infection from airborne particulates.
•
the air supplied into the theatre is clean/and sterile (HEPA filters),
•
the air is provided in a quantity deemed sufficient to dilute particulates in the room to a suitably low level, based on the number of particle per cubic meter (ACH),
•
the air entering the theatre does so in a controlled way, and only from the HEPA filtered supply terminals (positive air pressure)
•
What it does not ensure is that the air introduced is done in such a way that particulate are kept away from the operating zone. This is where theatre system design is critical, as there is a possible risk of contamination by airborne contaminants which may cause SI( secondary infections)