Objectives
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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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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

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


Economizer cooling regime

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


Economizer cooling regime1

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


Sequence of operation for the humidity control system design

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


Sensible and enthalpy and desiccant wheels

Sensible and Enthalpy and Desiccantwheels


Sensible and enthalpy wheels

Sensible and Enthalpy Wheels


Heat recovery system in nsm building at ut

Heat recovery system in NSM building at UT


Desiccant wheel

  • 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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