Building Services Engineering Flashcards
Indoor Comfort Dependencies
Thermal - Thermal Environment
Acoustic - Sound Level
Visual - Luminance / glare / daylight
Indoor Air Quality - Indoor Pollution / Air Quality
Thermal Comfort Definition
That condition of mind which expresses satisfaction with the Thermal Environment
Issues caused by over/underheating
37 Overheating 34 Undercooling Heat stroke Heat Exhaustion Frostbite Hypothermia
Fangers 7 Point Thermal Scale
3 - Hot 2 - Warm 1 - Slightly Warm 0 - Neutral -1 - Slightly Cold -2 - Cool -3 - Cold
Fangers Considerations
Environmental - Air temp, Mean radiant temp, Air velocity, Relative humidity
Personal - Metabolic rate, Clothing insulation
Mean Radiant Temperature
Average effect of temp from surrounding surfaces
Operative Temperature
Meausred by combining air temperature, mean radiant temperature and air speed
Three modes of Adaption
Behavioural Adjustment Adaption - Adaptive actions when uncomfortable
Physiological adaption - Heritage / acclimatising
Psychological adaption - alter perception expectation
Adaptive Thermal Comfort Model
Linking people comfort temperature indoors with temperature outdoors in naturally ventilated buildings
Radiant Asymmetry
Ration heat gain/loss from different sides of the body
Solid / Liquid / Gaseous Pollution
Solid - Dusts / fumes / smokes
Liquid - Mists / fogs / smokes by tars in cigarette smoke
Gaseous - SO2 / CO
Indoor Pollutant Sources
Paints / Adhesives / Smoking / Moulds
Co2 respiration / skin particles / Odours
Filters
Efficiency 20-90%
Type depend on application
Check / clean / replace periodically
Illuminance
Total luminous flux incident on a surface per unit area (Lux)
Measure for brightness
Daylight
Combination of all direct and indirect sunlight during the daytime
Sick Building Syndrome
A range of symptoms attributed to spending time in a certain building
SDS Factors
Poor maintenance / management
Lack of control over environment
Poor design
Poor indoor air quality
Types of Ventilation
Natural - Least improving Comfort Ventilation
Mechanical Ventilation
Comfort Cooling
Air Conditioning
Close Control Air Conditioning - Most cost
Wind Driven
Wind entering through windows on all floors
Buoyancy / Stack Driven
Enters and heat gains from the inside makes it rise through the building
Low pressure sucks in air
Scoop Ventilation
Using the direction of the wind to channel through stack to other parts
Ducted Ventilation
Wind directed by ducts to other parts of the building rising / falling
Disadvantages of Natural Ventilation
Air Pollution Noise Overheating Poor Security Lack of control
Advantages of Ventilation
Cheap, Simple and Renewable
No / Little maintenance
Occupant controlled
Occupant Behaviour Definition
If a change occurs such as to produce discomfort, people react in ways that tend to restore their comfort
Adaptive Behaviour Examples
Fans
Shading devices
Clothing
Activity levels
Retrofit Measures
Improve air tightness
Upgrade external wall insulation
Upgrade roof insulation
Increasing window layers
Heat Losses / Gain
Ventilation
Infiltration
Conduction through building fabric
Solar / People / Equipment / 3 abve
What makes up a conventional heating system
Fuel Heat Source Heat transfer medium water/air etc + pipework Power Heat Emitters Control devices
Pump in Series vs Parallel
Series - Same flow rate
Parallel - Same pressure
Expansion tank configuration
Open Tank - Open to atmosphere
Closed Tank - Captured air
Diaphragm Tank - Membrane inserted between air / water
Single Pipe System
Two / Dual Pipe
One pipe to everything
Hot Feed + Cold Return
Heat Emitters
Radiators Convectors Underfloor Heating Radiant Heating Air Handling Units
Radiator Pro’s / Con’s
Temp Control / low maintenance
Slow thermal response / Impact floor layout
Natural Convector
Room air pulled in
Finned heating tube
Warm air out
Air Handling Unit
Air Noise attenuator Frost coil Filters Cooling coil Re-heat coil Fan Humidifier Noise attenuator Duct
Fan Coil Unit
Air Filter Cooling Coil Heating Coil Fan Conditioned air
Metals with low resistance
Copper Aluminium Platinum Gold Silver
Electric Current Effects
Heating - Heat
Magnetic - Magnetic field
Chemical - Electrolysis
Ohm’s Law
V=IR
Volts
Amps
Ohm’s
Energy Equations
Energy = Power x Time
Inductance vs Capacitance
Inductance - induction of voltages in conductors self induced by the magnetic fields of currents
Capacitance - Electrostatic storage of charge induced by voltages between conductors
Inductance Examples
Motors
Heating Coils
Lighting chokes
CHP
Combined Heat and Power
Heat engine to generate electricity and useful heat
Transformer Equation
Vprimary / Vsecondary
Isecondary / Iprimary
Used to change voltage and current
Medium Voltage Switchgear
Switch / protect cables against faults
MV distribution network or intake
Air / vacuum circuit breakers