EML4600 lec 9 air side analysis

EML4600 lec 9 air side analysis - EML 4600 LECTURE 9 Air...

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1 EML 4600 LECTURE 9 Air Side Analysis So what do we use air for in buildings? Controlling temperature Controlling humidity To control odors related to toilet rooms To control fumes from kitchens, medical or laboratory processes To enhance air quality in clean rooms or medical spaces To control building pressurization to reduce infiltration To control room pressurization to containerize room functions
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2 EML 4600 LECTURE 9 Air Side Analysis Controlling temperature: Quantity and temperature of supply air controls internal heat gains Usually control with thermostat (temperature sensor) so we tend to focus on the control of supply air quantity and temperature to respond to changes in space temperature Humidity in many cases is controlled incidentally at the cooling coil by setting the supply air dew point
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3 EML 4600 LECTURE 9 Air Side Analysis Controlling temperature: T r = 75 deg F Q sens = 60,000 btuh Supply air at 56 deg F Return air at 75 deg F AHU
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4 EML 4600 LECTURE 9 Air Side Analysis Controlling temperature: T r = 75 deg F Q sens = 60,000 btuh Supply air at 56 deg F Return air at 75 deg F AHU Sensible heat balance cfm s * 1.08 * T = 60,000 btuh or cfm s = 2924 cfm T = 75 deg F – 56 Deg F = 19 deg F 2924 cfm
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5 EML 4600 LECTURE 9 Air Side Analysis Controlling temperature: T r = 75 deg F Q sens = 100,000 btuh Supply air at 56 deg F Return air at 75 deg F AHU Sensible heat balance cfm s * 1.08 * T = 100,000 btuh or cfm s = 4873 cfm T = 75 deg F – 56 Deg F = 19 deg F 4873 cfm What if internal sensible load increases to 100,000 btuh and we keep supply temperature constant?
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6 EML 4600 LECTURE 9 Air Side Analysis Controlling temperature: T r = 75 deg F Q sens = 100,000 btuh Supply air at 43 deg F Return air at 75 deg F AHU 2924 cfm What if internal sensible load increases to 100,000 btuh and we let supply temperature change? Sensible heat balance cfm s * 1.08 * T = 100,000 btuh or cfm s = 2924 cfm T = 32 deg F or 75 – 32 = 43 deg F (This is very cold!! Condensate issues!)
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7 EML 4600 LECTURE 9 Air Side Analysis Controlling humidity: C/C Return air at 75 deg F,
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EML4600 lec 9 air side analysis - EML 4600 LECTURE 9 Air...

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