# Psychrometrics - -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 dry bulb temperature - f 10 20 30 40 50 60 70 80 90 100 110

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• ARCH 373: ENVIRONMENTAL SYSTEMS 2

Ball State University | Department of Architecture | Summer 2014 | Grondzik

LABORATORY ONE

Psychrometrics

WEEK 1

15 MAY

The objective of this lab exercise is to provide hands-on experience using the psychrometric chart. The psychrometric chart is a key fi xture in the design of active climate control (HVAC) systems, as it provides a roadmap for the properties of moist air and the energy implications of changing those properties. The psychrometric chart is also very useful for condensation and evaporative cooling feasibility analyses (activities directly related to passive systems).

1. Assume that two of the various properties of the air in a room have been measured using low cost portable instrumentation (such as demonstrated in class): (a) the dry bulb air temperature = _____ deg F (b) the relative humidity = _____ %

Determine the:

(c) absolute humidity = ________________ (units = _______________________)

(d) wet bulb temperature = _____________ (units = _______________________)

(e) enthalpy = _______________________ (units = _______________________)

(f) specifi c volume = _________________ (units = _______________________) (g) dew point temperature = ___________ (units = _______________________)

2. Describe one or more ways in which winter condensation potential on windows in contact with air at these conditions might be reduced via psychrometric manipulation (changing the properties of the air and/or the temperature of materials).

3. How much sensible energy will be required to heat a pound of outdoor air from the Ft. Wayne winter design condition (Table B.1 MEEB) of 2 deg F to the indoor condition described in part 1?

4. How much sensible and how much latent energy will be required to cool a pound of outdoor air from Evansville summer design conditions (Table B.1 MEEB) of 90 deg F dry bulb; 75 deg F wet bulb to the indoor conditions described in part 1?

The following equation defi nes sensible energy requirements versus airfl ow rate: Btuh = (cfm) (1.1) (delta t)The following equation defi nes latent energy requirements versus airfl ow rate: Btuh = (cfm) (4840) (delta W)

• -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130

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PSYCHROMETRIC CHARTBAROMETRIC PRESSURE 29.921 inches of Mercury

Linric Company Psychrometric Chart, www.linric.com

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