BEM CLASS 5 Building Thermodynamics 3 Internal loads and heat - - PowerPoint PPT Presentation

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BEM CLASS 5 Building Thermodynamics 3 Internal loads and heat - - PowerPoint PPT Presentation

Sep 30, 2023 552 likes •673 views

BEM CLASS 5 Building Thermodynamics 3 Internal loads and heat gains Review Problems from Class 4 Heat loss calculation Pyschrometric Chart Forms of Heat Transfer Conduction Convection Radiation Internal loads and heat gains

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SLIDE 1

BEM CLASS 5

Building Thermodynamics – 3 Internal loads and heat gains

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SLIDE 2

Review Problems from Class 4

  • Heat loss calculation
  • Pyschrometric Chart
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SLIDE 3

Forms of Heat Transfer

Conduction Convection Radiation

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SLIDE 4

Internal loads and heat gains

  • Solar gain
  • Electrical devices
  • People
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SLIDE 5

Solar gain

  • Solar Constant: 433 btuh/sf
  • Actual gain on a surface varies

by orientation, season, time-of- day

  • Desirable in winter but can be

excessive

  • Major instantaneous load in

summer

  • Relation to lighting
  • Day-lighting
  • Glare
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SLIDE 6

Fenestration treatments for solar control

Architectural features

  • Adjusting glazed areas,

adjusting floor plates, atriums

  • Overhangs, light shelves,

external shading

Active facades

  • Curtain and shade systems
  • Electro -chromic
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SLIDE 7

Fenestration treatments for solar control

Reflective films and tinting, replaced by spectrally selective coatings

  • solar heat gain coefficient (SHGC) and visible transmittance
  • “low-e”
  • Optimize for heating, cooling
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SLIDE 8

Electricity

  • All electric use converted to heat
  • 3414 btu / kwh
  • Lighting, Motors, "plug-loads"
  • typically 2 - 3 watts per sf in typical office space
  • Computers
  • operate at a fraction of rated power
  • data centers 100 - 150 w/sf (data processing + cooling)
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SLIDE 9

Lighting

  • Comfort & productvity
  • illuminance levels - IEEE stds by task
  • lighting quality
  • Lighting Design, Lighting Modeling -

RADIANCE

  • Lighting Power Density – watts

per sf

  • Basis of code
  • 1 w/sf and less
  • CALCULATE
  • Usage hours
  • Lighting and lighting retrofit

SCHEDULES

How does day-light harvesting work?

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SLIDE 10

Calculate LPD

  • Room or zone is 40’ long x 25’ wide
  • There are three rows of 10 fixtures each with two 4-foot tubular

fluorescent lamps rated at 32w. Assume 10% ballast loss.

  • Area is occupied variously during 8 hour working day five days

per week, with occupancy sensors for groups of 6 fixtures.

  • What is the LPD?
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SLIDE 11

People

  • 300 btuh per person at normal office work
  • Design occupancy. Density by usage
  • Variable loads in places of assembly
  • Scheduling and modeling of where people are
  • big savings in controlling to occupancy
  • What people DO in their spaces. Relation to ZONES.
  • Lights
  • shades
  • Windows
  • Thermostats
  • Diffusers