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Final Projects

Final Projects. Grading criteria is posted on the course website Preliminary results are due Next Tuesday Final Project delivery on Monday Dec. 7 th Final Project presentation at noon. Field Trip to the central cooling and power plants. Monday, November 30: anytime in the afternoon

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Final Projects

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  1. Final Projects • Grading criteria is posted on the course website • Preliminary results are due Next Tuesday • Final Project delivery on Monday Dec. 7th • Final Project presentation at noon

  2. Field Tripto the central cooling and power plants • Monday, November 30: anytime in the afternoon • Thursday, December 3: 8-9:30 a.m. or 1-2:30 p.m. or 1:30-3 p.m.   • Friday, December 4: 10-12 p.m.

  3. Objectives • Finish with design of VAV and DOAS System • Control

  4. Other building load calculation tools

  5. Cooling and Heating Loadsfrom eQUEST Zone orientation Base size is 111.80 ft x 111.80 ft with perimeter zone depth of 15.00 ft. Floor to floor is 12 ft and floor to suspended ceiling is 9 ft.

  6. Example of Cooling and Heating Loads Cooling and heating load for each zone and whole building: Fresh air requirement based on number of occupants:

  7. Ventilation Loads http://www.ce.utexas.edu/prof/Novoselac/classes/ARE389H/Handouts/Std62-2001.pdf

  8. VAV System http://web.stanford.edu/group/narratives/classes/08-09/CEE215/ReferenceLibrary/HVAC%20Distributions%20Systems/Single-Path%20Multiple-Zone%20System%20Design.pdf

  9. VAV Example • One system • Multiple Spaces/Zones - VAV box for each space/zone http://www.trane.com/commercial/library/vol242/v24b6.asp

  10. VAV System Terms & Equations(you can find them in ASHRAE Standard 62) • Fraction of minimum outdoor air in space/zone supply air Xi = VOAi / VSAi • Critical space Space with maximumXi , Z=max(Xi) • Fraction of outdoor air in system supply air X = sum(VOA ) / sum(VSA) • Required Fraction of outdoor air: Y=X/(1+X-Z)

  11. Example Solution

  12. Other Issues Related to VAV • Fan control • Minimum supply air • Occupancy sensors

  13. VAV with fan terminal units

  14. DOAS System • http://doas.psu.edu/

  15. www.doas.psu.eduDOAS with multi-split systems Fresh air?

  16. DOAS fresh air configurations

  17. DOAS fresh air configurations

  18. Issues Related to DOAS • Split of sensible and latent load • Selection of hydronic system • Winter vs. summer operation • Winter operation with DX systems (heat pump)

  19. Economizer Fresh air volume flow rate control % fresh air 100% enthalpy Fresh (outdoor) air TOA (hOA) Minimum for ventilation damper mixing Recirc. air T & RH sensors

  20. Economizer – cooling regime How to control the fresh air volume flow rate? If TOA < Tset-point→ Supply more fresh air than the minimum required The question is how much? Open the damper for the fresh air and compare the Troom with the Tset-point . Open till you get the Troom = Tset-point If you have 100% fresh air and your still need cooling use cooling coil. What are the priorities: - Control the dampers and then the cooling coils or - Control the valves of cooling coil and then the dampers ? Defend by SEQUENCE OF OERATION the set of operation which HVAC designer provides to the automatic control engineer % fresh air 100% Minimum for ventilation

  21. Economizer – cooling regime Example of SEQUENCE OF OERATIONS: If TOA < Tset-point open the fresh air damper the maximum position Then, if Tindoor air < Tset-point start closing the cooling coil valve If cooling coil valve is closed and T indoor air < Tset-point start closing the damper till you get T indoor air = T set-point Other variations are possible

  22. HVAC Control Example 2: Dew point control (Relative Humidity control) fresh air damper filter cooling coil heating coil filter fan mixing T & RH sensors Heat gains Humidity generation We should supply air with lower humidity ratio (w) and lower temperature We either measure Dew Point directly or T & RH sensors substitute dew point sensor

  23. Relative humidity control by cooling coil Cooling Coil Mixture Room Supply TDP Heating coil

  24. Relative humidity control by cooling coil (CC) • Cooling coil is controlled by TDP set-point if TDP measured > TDP set-point → send the signal to open more the CC valve if TDP measured < TDP set-point → send the signal to close more the CC valve • Heating coil is controlled by Tair set-point if Tair < Tair set-point → send the signal to open more the heating coil valve if Tair > Tair set-point → send the signal to close more the heating coil valve Control valves Fresh air mixing cooling coil heating coil Tair & TDP sensors

  25. Mixture 3 DPTSP Set Point (SP) Mixture 2 Mixture 1 DBTSP Sequence of operation(ECJ research facility) Control logic: Mixture in zone 1: IF (( TM<TSP) & (DPTM<DPTSP) ) heating and humidifying Heater control: IF (TSP>TSA) increase heating or IF (TSP<TSA) decrease heating Humidifier: IF (DPTSP>DPTSA) increase humidifying or IF (DPTSP<DPTSA) decrease humid. Mixture in zone 2: IF ((TM>TSP) & (DPTM<DPTSP) ) cooling and humidifying Cool. coil cont.: IF (TSP<TSA) increase cooling or IF (TSP>TSA) decrease cooling Humidifier: IF (DPTSP>DPTSA) increase humidifying or IF (DPTSP<DPTSA) decrease hum. Mixture in zone 3: IF ((DPTM>DPTSP) ) cooling/dehumidifying and reheatin Cool. coil cont.: IF (DPTSP>DPTSA) increase cooling or IF (DPTSP<DPTSA) decrease cooling Heater control: IF (TSP>TSA) increase heating or IF (TSP<TSA) decrease heating

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