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Lecture Objectives:

This lecture reviews psychrometrics, introduces air handling units, and analyzes a swimming pool dehumidification example. It also includes homework assignments on psychrometrics.

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Lecture Objectives:

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  1. Lecture Objectives: • Review Psychrometrics • Introduce Air Handling Unit • Analyze swimming pool dehumidification example

  2. HW1 Psychrometrics • Due: September 18 • Textbook (Thermal Environmental Engineering) problems: • 8.1, 8.8, 8.13, 8.20 You have posted section 8 of this book

  3. Psychrometric Chart • Need two quantities for a state point • Can get all other quantities from a state point • Can do all calculations without a chart • Often require iteration • Many “digital” psychrometric charts available • Can make your own • Best source is ASHRAE fundamentals (Chapter 6)

  4. Connection between W and Pw(W humidity ratio – Pw water partial pressure) • PV = mRT (Ideal Gas Law ) • P = Pw + Pa R = gas constant P = pressure V = volume T = absolute temperature W = humidity ratio Subscripts: w is water vapor, a is dry air

  5. Psychrometrics (Swimming pool example)

  6. Swimming pool energy and mass balance

  7. Evaporation • Heat loss by evaporation: Tpool Tair pool W s W ≈ hm Wair Tpool Ws pool Depends on the air speed and even more on the condition of the water surface (people splashing in the water) Further analysis can be conducted in the psychrometric chart

  8. Air handling units (AHUs) Major components - …..

  9. Major AHU Components Heat Exchangers Humidifiers Steam Air to air Water Water (mist) AHU Fans Air - water or air - refrigerate Many more …

  10. Positioning of AHUs AHU – Air Handling Unit Distribution systems Fresh air For ventilation AHU Primary systems Air transport Electricity Secondary systems Cooling (chiller) Heating (boilers) Building Gas (or Gas)

  11. Process in AHUs • Example AHUs for swimming pools MENERGAThermoCond 19

  12. Swimming pool heating

  13. Dehumidification using outside air in Winter and Summer

  14. More advance control MENERGA ThermoCond 29

  15. Dehumidification using outside air in winter Condenser in the air stream Evaporator Compressor of the heat pump Condenser in the swimming pool

  16. Recirculation of air with dehumidification catalog

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