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Announcement No project presentations !

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Presentation on theme: "Announcement No project presentations !"— Presentation transcript:

1 Announcement No project presentations !
In last class (on Thursday) we will review HVAC systems of the New Engineering Building review course material

2 Lecture Objectives: Automatic control Heat recovery system
Sequence of operation Heat recovery system Desiccant systems

3 HVAC Control Example : Dew point control (Relative Humidity control)
fresh air damper filter cooling coil heating coil filter fan mixing T & RH sensors

4 Basic purpose of HVAC control
Daily, weekly, and seasonal swings make HVAC control challenging Highly unsteady-state environment Provide balance of reasonable comfort at minimum cost and energy Two distinct actions: 1) Switching/Enabling: Manage availability of plant according to schedule using timers. 2) Regulation: Match plant capacity to demand

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

6 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

7 Terminology Sensor Controller Controlled device
Measures quantity of interest Controller Interprets sensor data Controlled device Changes based on controller output Figure 2-13

8 Sensible and Enthalpy and Desiccant wheels

9 Sensible and Enthalpy Wheels

10 Heat recovery system in NSM building at UT

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


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