BS2 Hvac ventilation 1
-
Upload
est -
Category
Art & Photos
-
view
320 -
download
9
Transcript of BS2 Hvac ventilation 1
BUILDING SERVICES TWO (BLD60503)
HVAC Systems & Building
BUILDING | SERVICES | TWO (BLD60503)
Ventilation
Prepared by Tan Hee Chai
BUILDING | SERVICES | TWO (BLD60503)
Ventilation RequirementsThe effect of air on health and comfort depends upon:Movements;Humidity andTemperature
BUILDING | SERVICES | TWO (BLD60503)
BUILDING | SERVICES | TWO (BLD60503)
BUILDING | SERVICES | TWO (BLD60503)
Ventilation systemRatio Main Elements in Dry atmospheric
Oxygen 21%
Carbon dioxide 0.03%
Nitrogen NeonHelium HydrogenWater Vapour79%
BUILDING | SERVICES | TWO (BLD60503)
Ventilation Requirements
Air change important for two reasons:
1.Maintain a satisfactory level of oxygen content – essential for life2.To remove impurities
BUILDING | SERVICES | TWO (BLD60503)
Ventilation Requirements
BUILDING | SERVICES | TWO (BLD60503)Ventilation System
Rate of air change = ratio of fresh air supplied each hour to volume of the enclosed space
BUILDING | SERVICES | TWO (BLD60503)
Ventilation System Example: A private office of 30 m3 volume designed for 2 persons:Recommended m3/hour per person is 43
43/30 x 2 = 2.86 air change per hour
BUILDING | SERVICES | TWO (BLD60503)
Ventilation System
Ordinary conditions
Fresh air supply of 30 -35m3 per person per hour
• 1.5 air changes per hour for family of 4
Normal living room 45 m3:
BUILDING | SERVICES | TWO (BLD60503)
Ventilation System
BUILDING | SERVICES | TWO (BLD60503)
Ventilation SystemVentilation rates requirements:Normally based on recommendations by authorities or code of practice e.g:•Department of Occupational Safety & Health (DOSH)•Malaysian Standard Code of Practice
BUILDING | SERVICES | TWO (BLD60503)
Ventilation System
Apart from fresh air, movement of air over surface of body necessary to remove surplus •heat, •water vapour, •carbon dioxide and •organic vapours from body
BUILDING | SERVICES | TWO (BLD60503)Ventilation System
Desirable characteristics of atmosphere:•Cool •Dry •Diverse in temperature in different parts and at different times •Moving
Undesirable characteristics of atmosphere:•Hot•Damp•Uniform and Monotonous•Still
BUILDING | SERVICES | TWO (BLD60503)
Ventilation System
Desirable characteristics of atmosphere:•Air change•Proper means of ventilation
Undesirable characteristics of atmosphere:•Cubic space•Excessive cubic space
BUILDING | SERVICES | TWO (BLD60503)
Ventilation SystemVentilation principles:
To prevent undue concentrations of odours,
Bacteria carrying particles andNoxious gases
BUILDING | SERVICES | TWO (BLD60503)
Ventilation SystemVentilation principles:
To remove heat from products of combustionBody heat and heat from electrical equipment, motors, heat from solar radiation etc
BUILDING | SERVICES | TWO (BLD60503)
Ventilation SystemVentilation principles:
To remove fumes, dust etc produced by industrial process
BUILDING | SERVICES | TWO (BLD60503)Ventilation System
Ventilation principles:To maintain the relative humidity within reasonable limits
BUILDING | SERVICES | TWO (BLD60503)
Ventilation SystemVentilation principles:Percentage saturation = Weight of moisture in the air/weight of moisture if air were saturated at the same temperature x 100%Relative humidity (RH) = Vapour pressure of moisture present/ Vapour pressure if air were saturated at the same temperature x 100%
BUILDING | SERVICES | TWO (BLD60503)
Ventilation SystemVentilation principles: Relative Humidity
BUILDING | SERVICES | TWO (BLD60503)
Ventilation principles:
To create air movement
BUILDING | SERVICES | TWO (BLD60503)
Natural Ventilation
• Natural ventilation systems rely on pressure differences to move fresh air through buildings.
• Pressure differences can be caused by wind or the buoyancy effect created by temperature differences or differences in humidity.
BUILDING | SERVICES | TWO (BLD60503)
Natural Ventilation
BUILDING | SERVICES | TWO (BLD60503)
Pressure Patterns caused by wind
BUILDING | SERVICES | TWO (BLD60503)
Passive stack ventilation (PSV)
PSV Consist of Extract grilles at ceiling height Ducts to terminal at roof
BUILDING | SERVICES | TWO (BLD60503)
Passive stack ventilation (PSV) Types of vent
BUILDING | SERVICES | TWO (BLD60503)
Natural Ventilation System
BUILDING | SERVICES | TWO (BLD60503)
Building Regulation
Habitable or occupiable rooms located on an external wall
Requirements require a window
opening with permanent background ventilation
Natural Ventilation System
Non-habitable rooms in domestic buildings
Maybe ventilated mechanically or by passive stack ventilation system
BUILDING | SERVICES | TWO (BLD60503)
Building Regulation
Rooms with no openable windows in non-domestic buildings
Requirements Mechnical ventilated
or air-conditioning
Natural Ventilation System
Kitchen,bathrooms,utility rooms etc
Open window and mechanical extract ventilation or by passive stack ventilation system
BUILDING | SERVICES | TWO (BLD60503)
Mechanical Ventilation System
Artificial methods of preserving the purity and controlling the temperature of the atmosphere.
BUILDING | SERVICES | TWO (BLD60503)
Mechanical Ventilation System
Method: Extract Supply Combined extract and input
BUILDING | SERVICES | TWO (BLD60503)
Extractor fan system
BUILDING | SERVICES | TWO (BLD60503)
Extractor fan
BUILDING | SERVICES | TWO (BLD60503)
Extract system
• Cheap to install and operate• Definite volume of air is removed from
buildings• Air entering to replace cannot be controlled.• Draughts are created
BUILDING | SERVICES | TWO (BLD60503)
Supply system
BUILDING | SERVICES | TWO (BLD60503)
Supply system
BUILDING | SERVICES | TWO (BLD60503)
• Air delivered under pressure.
• Include air heater battery with automatic
control over temperature of air delivered
into rooms
• An air filtration device
Supply system
BUILDING | SERVICES | TWO (BLD60503)
• Easy to install in existing buildings• Can be included when designing new
building.• Eliminates draughts by building up
pressure inside the spaces
Supply system
BUILDING | SERVICES | TWO (BLD60503)
Combined supply & extract system with propeller fans
BUILDING | SERVICES | TWO (BLD60503)
Combined supply & extract system with propeller fans
BUILDING | SERVICES | TWO (BLD60503) Heat Exchanger
BUILDING | SERVICES | TWO (BLD60503) Heat Exchanger
BUILDING | SERVICES | TWO (BLD60503)
Mechanical Ventilation System
Components:FanFiltersDuctworkFire dampersDiffusers
BUILDING | SERVICES | TWO (BLD60503)
Mechanical Ventilation System
Types of Fan Cross-flow or tangential Propeller Axial flow Centrifugal
BUILDING | SERVICES | TWO (BLD60503)
Wall mounted propeller fan
BUILDING | SERVICES | TWO (BLD60503)
Axial-flow fan
BUILDING | SERVICES | TWO (BLD60503)
Bifurcated axial flow fan
BUILDING | SERVICES | TWO (BLD60503)
Centrifugal fan
BUILDING | SERVICES | TWO (BLD60503)
Centrifugal fan
BUILDING | SERVICES | TWO (BLD60503)
Centrifugal fan
BUILDING | SERVICES | TWO (BLD60503)
Cross-flow or tangential fan
BUILDING | SERVICES | TWO (BLD60503)
Filters
Dry Filter made of •Paper•Fine woven fabrics•Foamed plastics or fibreglass
BUILDING | SERVICES | TWO (BLD60503)
Dry Filters
BUILDING | SERVICES | TWO (BLD60503)
Filters
Viscous or Wet Filter made of •A bank or rows of corrugated metal sheets with surface coated in non-flammable, non-toxic odourless oil
BUILDING | SERVICES | TWO (BLD60503)
Viscous or Wet Filter
BUILDING | SERVICES | TWO (BLD60503)
Electrostatic Filterconsist of •Pre-filter•Power pack•Ioniser•Rows of opposing charged plates
BUILDING | SERVICES | TWO (BLD60503)
Electrostatic Filter
BUILDING | SERVICES | TWO (BLD60503)
Electrostatic Filter
BUILDING | SERVICES | TWO (BLD60503)
Activated carbon Filter
BUILDING | SERVICES | TWO (BLD60503)
Activated carbon Filter
made of •Disposable elements of glass fibrous matting containing charcoal granular
BUILDING | SERVICES | TWO (BLD60503)
BUILDING | SERVICES | TWO (BLD60503)
BUILDING | SERVICES | TWO (BLD60503)
Ventilation duct design
BUILDING | SERVICES | TWO (BLD60503)
Factors influencing the size of ducts for air transport are:
The volume of flow rate of the air The friction of the air against the walls of
the ducts and any turns and protrusions. The pressure available for the movement of
air.
BUILDING | SERVICES | TWO (BLD60503)
BUILDING | SERVICES | TWO (BLD60503)
Calculation of air volume flow rate:
Q = Room volume x air changes per hour/time in seconds
Where • Q is the volume of flow rate in
m3/s
Ventilation duct design
BUILDING | SERVICES | TWO (BLD60503)Ventilation duct design
BUILDING | SERVICES | TWO (BLD60503)
Ventilation duct design - Chart
BUILDING | SERVICES | TWO (BLD60503)
Ventilation duct design
BUILDING | SERVICES | TWO (BLD60503)Ventilation duct design
BUILDING | SERVICES | TWO (BLD60503)Ventilation duct design
BUILDING | SERVICES | TWO (BLD60503)
Ventilation duct design
BUILDING | SERVICES | TWO (BLD60503)
Ventilation Design – Duct conversion
BUILDING | SERVICES | TWO (BLD60503)
Ventilation Design – Duct conversion chart
BUILDING | SERVICES | TWO (BLD60503)
The End