Lecture Objectives:

# Lecture Objectives:

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## Lecture Objectives:

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##### Presentation Transcript

1. Lecture Objectives: • Finish heat pump example • Review Psychrometrics • Swimming pool example

2. Heat pump example A recreation center Heat Pump Ice Rink Swimming pool Condenser Evaporator 30oF 85-89oF Rejects heat energy Consumes heat energy Electric power for a compressor

3. Challenges for this problem • Circulating fluid • Adjustment of evaporation and condensation temperatures • Adjustment of capacity for design condition • Control of capacity for non design conditions • Need to study load profiles • Design sophisticated control • Provide backup system

4. Psychrometrics (Swimming pool example)

5. 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) • Or electronic version at: http://www.handsdownsoftware.com/

6. 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

7. Swimming pool energy and mass balance

8. 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

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

10. Swimming pool heating

11. Dehumidification using outside air in Winter and Summer

12. More advance control MENERGA ThermoCond 29

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