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Objectives

Objectives. Learn about 1) Control for HVAC systems - Economizers (Psychrometrics) and control - Heat recovery systems (Psychrometrics) 2) Some advance HVAC systems desiccant, enthalpy, sensible wheel . Economizer. Economizer (fresh air volume flow rate control).

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Objectives

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  1. Objectives Learn about 1) Control for HVAC systems - Economizers (Psychrometrics) and control - Heat recovery systems (Psychrometrics) 2) Some advance HVAC systems desiccant, enthalpy, sensible wheel

  2. Economizer Economizer (fresh air volume flow rate control) Controlled device is damper - Damper for the air - Valve for the CC fresh air damper mixing recirc. air T & RH sensors

  3. 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

  4. 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

  5. Sequence of operation for the humidity control system design Adiabatic humidifier CC HC SA OA • mixing RA Define the sequence of operation for: WINTER operation and: - case when humidity is not controlled - case when humidity is precisely controlled

  6. Sensible and Enthalpy and Desiccantwheels

  7. Sensible and Enthalpy Wheels

  8. Heat recovery system in NSM building at UT

  9. Figure 3 – A desiccant-based cooling system combined with regenerative heat exchanger, vapor compression cooling, and evaporative humidifier (hybrid system). Desiccant wheel

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