nibm - lecture - three

8/3/2019 Nibm - Lecture - Three

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BUILDING SCIENCE for INTERIOR DESIGNLecture three natural &

artificial lighting24.10.2011

Archt. RANGASOYSA. BSc[BE],MSc[Arch],AIA[SL]


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BUILDING SCIENCE for INTERIOR DESIGN

Lighting designTime duration two lectures

Out line

1. Source of light

2. Lighting metrics

3. Lighting terms

Tutorial :

1- advantages and disadvantages of natural lighting


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Sources of LightNeed for artificial lighting :

1. Absence of natural lighting

2. To compensate for low levels of natural lighting


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Types of light sources1. Incandescent

i. General service

ii. halogen

2. Low pressure discharge

i. Florescent

ii. Low pressure sodium

3. High pressure discharge

i. Mercury vapor

ii. High pressure sodium


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Incandescent lampsLight produced by filament heated to

incandescence by an electric current.

Discharge lamps

Light produced by the passage of electrical currentthrough a vapour of gas.

Ultraviolet lighting phosphorus Generate light


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General service lampsProperties :

1. Lamp construction2. Shape

3. Efficiency

4. Operating characteristics


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General service lamps1. Lamp construction

Glass enclosure soda lime / Clear or frosted

Inside filled with gas [ argon or nitrogen ]

Reduce lamp blackening caused by filament evaporation

Filament tungsten

Propertiesi. High strength

ii. high ductility

iii. High melting point

iv. Low evaporation

v. Favorable radiation qualities


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General service lampsSupport wires - copper or nickel plated

Base - made of aluminum or brass

conducts electricity to filament

holds lamp at socket

3. Lamp efficiency

Increase with wattage high luminance at high watts

[ 5W, 10W, 15W , 25W, 40W , 60W , 75W, 100W, 125W


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General service lamps4. Operation characteristics

1. voltage variation effects to life cycle, lamp out put, efficiency

[General voltage in sri lankan and other countries ]

2. burning position base up vs base down

3. usage residential, retail, theatrical , art galleries

4. average rate : 750 1000 hrs


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General service lampsTypes of incandescent lamps :

1. General service :

common residential application

Typically A and PS types

Screw type and pin type

Between 10W to 1000W

2. Reflector type lamps :

R type reflector

ER type elliptical reflector

PAR type parabolic aluminum reflector

life span 2000 hrs

Less efficient than general service lamps

Usage spot lighting , flood lighting and projection


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General service lampsDisadvantages :

1. Relativity short life span

2. Poor maintains at voltage tolerance

10-15 % tolerance reduce 75 % of life space - [ need of stabilizer ]

3. Inefficient only 10 % of wattage [ energy ] uses as light.

4. High heat effects fire hazards


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Florescent lampsMechanism :

1. Voltage is applied across the electrode

2. current runs through the cathode wire to heat tungsten and emissive

material.

3. Electrons are emitted from the cathode and accelerated towards the

anode by the electric field across the electrode [ this creates arc ]

4. Electrons collide with mercury atoms and cause them to emit UV

radiation.5. UV radiation is converted by prospers in to visible radiation.


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Florescent lampsConstruction :

1. Bulb :

shapes

Diameters

Inner surface coated with blend phosphorus

2. Electrodes

Located at each end of the lamp [ cathode and anode ]

Coiled tungsten wire coated with alkaline earth material

3. Gas

Mercury vapor

4. Ballast - choke

Electric pulse [ high voltage ]

5. Base - conducts electricity to cathode and holds lamp in socket


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Florescent lampsProperties :

Life span 12000 hrs 24000 hrs [ at 3 hours continues burn ]

Voltage variation :

Affects lamp life

Increase and decrease coloration

Lower lumen maintenance

Low operating cost

Ambient temperature : optimum lumen output at 77 F [ 25C]


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Florescent lampsTYPES

1. Pre heat

electrodes are pre heated for 5 sec before the start

Starting switch is unreliable

Lamps are interchangeable with rapid start lamp

2. Instant start

No preheating required

Arc is created with by applying high starting voltage

High starting voltage reduce lamp life


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Florescent lampsTYPES

1. Pre heat

electrodes are pre heated for 5 sec before the start

Starting switch is unreliable

Lamps are interchangeable with rapid start lamp

2. Instant start

No preheating required

Arc is created with by applying high starting voltage

High starting voltage reduce lamp life


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Lighting related termsLamp - transforms electricity to visible light

Luminaries - complete lighting unit

Efficacy lumens per watt

Efficiency - luminaries to lamp lumens

Power budget total lighting power on a project [ watts ]

Power density - watts per square density


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Lighting related termsVoltage - [ V ] electrical potential [ pressure ] measured in volts

Current [ I ] Flow of electrons measured in amps

Resistance [ R ] oppose flow of electrons / friction measured in oms

Power [ P ] energy consumed to perform work, measured in watts

Energy [ E ] power consumed to perform work measured in watts

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