EML4600 lec 5 clg loads 2007

EML4600 lec 5 clg loads 2007 - EML 4600 Heating Loadswhen...

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1 EML 4600 Heating Loads…when do we need to worry about heating capacity? When the building is residential in nature. When the building is light commercial with significant exposed walls and windows and low internal heat gains. When we are at the perimeter of a building. When we need to reheat air for temperature control. H. A. . . Ingley PhD,PE
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2 EML 4600 LECTURE 5 Heating Loads Typical components of a heating load: Envelope heat losses (fenestrations, walls, floors above grade and roof) Slab heat losses Infiltration Ventilation Usually neglect internal heat gains when sizing (Why?) H. A. . . Ingley PhD,PE
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3 EML 4600 LECTURE 5 Heating Loads Typical components of a heating load: Envelope heat losses Q’= U*A*(T r – T o ) Note: for walls below grade T is modified. Tr = indoor design temp and To = outdoor design temp Slab heat losses for slab-on-grade Q’ = F * P * (T r – T o ) Infiltration Q’ = CFM * 1.08 * (T r - T o ) Note: this is for sensible only. In some climates you may need to add humidity. Ventilation (same equation as infiltration) Usually neglect internal heat gains when sizing H. A. . . Ingley PhD,PE
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4 EML 4600 LECTURE 5 Heating Loads Typical components of a heating load: Perimeter loss factors (btuh/deg F ft perimeter) 2950 DD 8 in. block wall Un-insulated 0.72 with brick facing Slab Metal Stud wall Un-insulated 1.34 with stucco finish Slab Note: Jacksonville has 1239 DD, Athens,Ga is about 2950 DD. H. A. . . Ingley PhD,PE
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5 EML 4600 LECTURE 5 Heating Loads Typical components of a heating load: Infiltration Rates Measure: tracer gas method, blower door method Residential data: 0.2 to 2.0 ACPH Crack method Component analysis Remember: what goes in equals what goes out! H. A. . . Ingley PhD,PE
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6 EML 4600 LECTURE 5 Cooling Loads Instantaneous heat gains: rate at which energy is transferred to or generated within a space Heat extraction rate: the rate at which energy is removed from the space by the equipment. .equal to cooling load when equipment is operating and conditions in space are constant. Rare. Temperature varies due to the controls. Cooling load: rate at which energy must be removed from a space to maintain temperature and humidity at the design values Remember this? A test topic…. .
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7 EML 4600 LECTURE 5 Cooling Loads Sensible Heat Gains Latent Heat Gains Internal Ventilation Internal Ventilation Lights Outside air People Outside air People Equipment Equipment Infiltration Walls Roof Floor Windows: cond/conv Windows: Solar Infiltration
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8 EML 4600 LECTURE 5 Cooling Loads Qsi = internal sensible heat gains Qli = internal latent heat gains Qti = total internal heat gains = Qsi + Qli Qsv = ventilation sensible heat gains Qlv = ventilation latent heat gains Qtv = ventilation total heat gains = Qsv + Qlv Qst = total sensible heat gain = Qsi + Qsv Qtt = total heat gain = Qtv + Qti SHRi = internal sensible heat ratio = Qsi/Qti SHRt = total sensible heat ratio = Qst/Qtt
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This note was uploaded on 10/22/2011 for the course EML 4930 taught by Professor Staff during the Fall '08 term at University of Florida.

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EML4600 lec 5 clg loads 2007 - EML 4600 Heating Loadswhen...

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