1 1 Air Conditioning Design - Psychrometrics & Coil Load Calculation Air Conditioning Design Psychrometrics & Coil Load Calculations Air Conditioning Design Keith E. Elder, P.E. Coils • Coils are the main devices for transferring energy to/from the airstream in an air-handling system. • Heat Transfer Media – Hydronic Fluid (Water) – Steam – Direct Expansion • Important Coil Load Concepts – Apparatus Dew Point – Bypass Factor
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The ratio of space sensible cooling to totalcooling is useful for plotting the slope of thepath that supply air travels after introductioninto the space.
Sensible Heat Ratio (SHR)
Apparatus Dew Point
Apparatus dew point (ADP) is the coil surfacedew point temperature required to accomplisha cooling/dehumidifying process.
Determine the minimum cooling coil load and requiredchilled water flow for a system serving an office space with asensible cooling load of 30,800 Btu/h and a latent load of8,500 Btu/h?
Indoor design conditions are 75oF/50% RH, and Outdoordesign conditions are 85oF DB/70oF WB.
The minimum ventilation air is 33% of the total supply airwhich is delivered at 55oF. The fan selected is a 70% efficient"draw-through" arrangement, and delivers air at 4.0 inchestotal pressure.
No manufacturer’s coil data is available. Assume 10°Fchilled water temperature rise through the coil.