Lecture 22: Primary System Loops in EnergyPlus Material prepared by GARD Analytics, Inc. and...

Lecture 22: Primary System Loops in EnergyPlus

Material prepared by GARD Analytics, Inc. and University of Illinoisat Urbana-Champaign under contract to the National Renewable Energy

Laboratory. All material Copyright 2002-2003 U.S.D.O.E. - All rights reserved

2

Purpose of this Lecture

Gain an understanding of: Water (fluid) side loop structures in

EnergyPlus How to control fluid flow rates using

the EnergyPlus pump strategies

3

Defining Loops

Loops define the movement of mass and energy within an HVAC system Plant loop Condenser loop Heat recovery loop

Systems defined by the order of branches/components on the HVAC loop

4

Defining Loops (cont’d)

Main loops divided into “sub-loops” or “semi-loops” for organizational clarity & simulation logistics

Sub-loops are matched pairs that consist of half of the main loop.

For example, plant and condenser loops are broken into supply and demand sides.

5

Demand- & Supply-SideSub-Loops

Plant demand-side sub-loop contains equipment that creates a load on the plant.

Plant supply-side sub-loop contains equipment that meets these loads.

Each supply-side sub-loop must be connected to a demand-side loop.

6

Demand- & Supply-Side Loops (cont’d)

Boiler

Boiler Inlet Node

Boiler Outlet Node

Supply-Side LoopDemand-Side Loop

±HW Pump

Heating Coil

HW Supply inlet Node

HW Supply Outlet NodeHW Demand Inlet Node

HW DemandOutlet Node

Heating CoilInlet Node

HW Pump Outlet Node

Inlet PipeHeating Coil Outlet Node

Exit Pipe

HW Supply Outlet Pipe

7

Branches for Water-Side Loops

Maximum Branch Flow Rate (Ignored)

Comp1 TypeComp1 NameComp1 Inlet Node NameComp1 Outlet Node NameComp1 Branch Control Type

8

Branches for Water-Side Loops - Example

BRANCH,

Heating Supply Inlet Branch, !- Branch Name

, !- Maximum Branch Flow Rate {m3/s}

PUMP:VARIABLE SPEED, !- Comp1 Type

HW Circ Pump, !- Comp1 Name

HW Supply Inlet Node, !- Comp1 Inlet Node Name

HW Pump Outlet Node, !- Comp1 Outlet Node Name

ACTIVE; !- Comp1 Branch Control Type

9

Layout for Individual HVAC Supply or Demand Sub-

Loops Elements can be defined

in series, in parallel, or both with some restrictions

Branches are defined as individual legs within the loop structure

Segment between point A & B is defined as a branch, as is the section between points E and F

1 to mComponents

n Splitter

A

B

1 to iComponents

C1

... 1 to jComponents

Cn

D1 Dn

n Mixer

1 to kComponents

E

F

1 to mComponents

n Splitter

A

B

1 to i

1 to mComponents

n Splitter

A

B

1 to iComponents

C1


Cn

D1 Dn

n Mixer

1 to kComponents

E

F

10


Loops The first supply side component between A & B must be the loop pump, which controls the loop flow.

There may be multiple branches between the splitter and mixer (between points C1 & D1 to Cn & Dn).

Each sub-loop may only have one splitter and one mixer.

1 to mComponents

n Splitter

A

B

1 to iComponents

C1


Cn

D1 Dn

n Mixer

1 to kComponents

E

F

1 to mComponents

n Splitter

A

B

1 to i

1 to mComponents

n Splitter

A

B

1 to iComponents

C1


Cn

D1 Dn

n Mixer

1 to kComponents

E

F

11


Loops Equipment may be in

parallel between the mixer and splitter,

Within any branch, there can only be elements in series.

Sub-loops do not require a splitter or mixer, if all equipment on the sub-loop is in series—a single branch defines the entire sub-loop.

1 to mComponents

n Splitter

A

B

1 to iComponents

C1


Cn

D1 Dn

n Mixer

1 to kComponents

E

F

1 to mComponents

n Splitter

A

B

1 to i

1 to mComponents

n Splitter

A

B

1 to iComponents

C1


Cn

D1 Dn

n Mixer

1 to kComponents

E

F

12

Pumping Rules

Pumps must be on the supply side

Pumps can operate as constant or variable flow

Pumps can run continuously or intermittently

Splitter

Mixer

Components

Loop Pump

From Demand-Side Sub-Loop

To Demand-Side Sub-Loop

Supply-Side Sub-Loop

13

Pumping Rules (cont’d)

Single boiler/chiller with NO bypass, PUMP:CONSTANT SPEED Boiler/chiller should be constant flow Pump should be intermittent

Single boiler/chiller with NO bypass, PUMP:VARIABLE SPEED Boiler/chiller should be variable flow, regardless of

whether pump is intermittent or continuous (runs at the minimum if demand is less than minimum, this includes zero.)

14


Single boiler/chiller with bypass, PUMP:CONSTANT SPEED Boiler/chiller can be constant or variable

flow Pump may be intermittent or continuous as

long as the bypass can handle the entire pump volume when the boiler is not operating

15


Multiple branches add more complexity, but it is nothing more than continuity.

If the pump is putting out flow then it has to have a branch to flow down whether it is a chiller or a bypass.

16


You are always safer adding the bypass for a simulation. If the active machines require the flow the bypass will be dry

Thermodynamically it does not make any difference if the flow goes through a machine that is OFF or it flows down the bypass.

There is no pressure simulation and flow losses are not accounted for.

17

Summary of Loop Limitations

Each sub-loop allowed one splitter and one mixer

One bypass on each sub-loop optionalNo other components may be in series

with a bypassEquipment may be in parallel only

between the splitter and mixerEquipment may be in series in each

branch

18

3-Zone VAV SystemWe are going to look at this system input Loop by Loop

North

Zone

East

Zone

Resistive

Zone

Plant Supply SideCooling Loop

CW Pump

CoolingTower

Cond . Pump

Cond . Supply Side Loop

ChillerBypass

Supply Fan

Retu

rn A

ir M

ixe

r

Zon

e A

ir Sp

litter

Plant Demand SideCooling Loop

Pla

nt D

em

an

d S

ide

Hea

ting

Loo

p

CC

Byp

ass

CondenserBypass

VAV Box: ReHeat

VAV Box: ReHeat

Retu

rn H

ot

Wa

ter M

ixer

Bypass

Cond . DemandSide Loop

CondenserBypass

Hot W

ate

r

Sp

litter

Mixed OutsideAir Box

Relief Air

Outside Air

VAV Box: ReHeatBoiler

Plant Supply SideHeating Loop

HW Pump

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Retu

rn A

ir M

ixe

r

Zon

e A

ir Sp

litter


Pla

nt D

em

an

d S

ide

Hea

ting

Loo

p

CC

Byp

ass

CondenserBypass

VAV Box: ReHeat

VAV Box: ReHeat

Retu

rn H

ot

Wa

ter M

ixer

Bypass


CondenserBypass

Hot W

ate

r

Sp

litter


Relief Air

Outside Air



HW Pump

Boiler


HW Pump

19

Cooling Coil & Chilled Water Demand Side

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Retu

rn A

ir M

ixe

r

Zone A

ir Splitte

r


Pla

nt D

em

and S

ide

Heatin

g L

oop

CC

Byp

ass

CondenserBypass

VAV Box: ReHeat

VAV Box: ReHeat

Retu

rn H

ot

Wate

r Mixe

r

Bypass


CondenserBypass

Hot W

ate

r

Splitte

r


Relief Air

Outside Air



HW Pump

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Retu

rn A

ir M

ixe

r

Zone A

ir Splitte

r


Pla

nt D

em

and S

ide

Heatin

g L

oop

CC

Byp

ass

CondenserBypass

VAV Box: ReHeat

VAV Box: ReHeat

Retu

rn H

ot

Wate

r Mixe

r

Bypass


CondenserBypass

Hot W

ate

r

Splitte

r


Relief Air

Outside Air



HW Pump

Boiler


HW Pump

20


Objects required: BRANCH LIST CONNECTOR LIST SPLITTER MIXER BRANCH, VAV Sys 1 ChW-Branch

COIL:Water:DetailedFlatCooling, VAV SYS 1 Cooling Coil

BypassChilled Water Demand -Side Outlet Node

Chilled Water Demand -Side Inlet Note

CC Cooling Coil



CC Cooling Coil

21


(cont’d)

Objects required (cont’d): BRANCH, Chilled Water Loop 1 CHW Inlet Branch

PIPE

BRANCH, Chilled Water Loop 1 CHW Outlet Branch PIPE

BRANCH, Chilled Water Loop 1 CHW Bypass Branch PIPE



CC Cooling Coil



CC Cooling Coil

22

Hot Water Demand Side

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Re

turn

Air

Mix

er

Zo

ne A

ir Sp

litter


Pla

nt D

em

an

d S

ide

Hea

ting

Loo

p

CC

Byp

ass

CondenserBypass

VAV Box: ReHeat

VAV Box: ReHeat

Retu

rn H

ot

Wa

ter M

ixer

Bypass


CondenserBypass

Hot W

ate

r

Sp

litter


Relief Air

Outside Air



HW Pump

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Re

turn

Air

Mix

er

Zo

ne A

ir Sp

litter


Pla

nt D

em

an

d S

ide

Hea

ting

Loo

p

CC

Byp

ass

CondenserBypass

VAV Box: ReHeat

VAV Box: ReHeat

Retu

rn H

ot

Wa

ter M

ixer

Bypass


CondenserBypass

Hot W

ate

r

Sp

litter


Relief Air

Outside Air



HW Pump

Boiler


HW Pump

23

Hot Water Coils & Demand Side

Objects required: BRANCH LIST CONNECTOR LIST SPLITTER MIXER BRANCH,Zone X Reheat

Branch (3) COIL:Water:SimpleHeating(

3) BRANCH, HW Outlet Branch

PIPE BRANCH, HW Inlet Branch

PIPE BRANCH, HW Bypass Branch

PIPE

Zo

ne

Air S

plitte

r

Pla

nt D

em

an

d S

ide

Hea

ting

Lo

op

Retu

rn H

W M

ixer

Byp

ass

HW

Sp

litter

VAV Box:Reheat

VAV Box:Reheat

VAV Box:Reheat

Zo

ne

Air S

plitte

r

Pla

nt D

em

an

d S

ide

Hea

ting

Lo

op

Retu

rn H

W M

ixer

Byp

ass

HW

Sp

litter

VAV Box:Reheat

VAV Box:Reheat

VAV Box:Reheat

24

Hot Water Loop Supply Side

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Retu

rn A

ir M

ixe

r

Zone A

ir Splitte

r


Pla

nt D

em

and S

ide

Heatin

g L

oop

CC

Byp

ass

CondenserBypass

VAV Box:ReHeat

VAV Box:ReHeat

Retu

rn H

ot

Wate

r Mixe

r

Bypass


CondenserBypass

Hot W

ate

r

Splitte

r


Relief Air

Outside Air

VAV Box:ReHeatBoiler


HW Pump

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Retu

rn A

ir M

ixe

r

Zone A

ir Splitte

r


Pla

nt D

em

and S

ide

Heatin

g L

oop

CC

Byp

ass

CondenserBypass

VAV Box:ReHeat

VAV Box:ReHeat

Retu

rn H

ot

Wate

r Mixe

r

Bypass


CondenserBypass

Hot W

ate

r

Splitte

r


Relief Air

Outside Air



HW Pump

Boiler


HW Pump

25



Objects required: PLANT LOOP BRANCH LIST CONNECTOR LIST SPLITTER MIXER BRANCH, Supply Inlet

Branch PUMP:VARIABLE SPEED

Boiler

Pla

nt

De

ma

nd

Sid

eH

ea

ting

Lo

op

Boiler Outlet Node

HW Pump

HW PumpOutlet Node

Byp

ass

BoilerInlet Node

HW SupplyInlet Node

HW SupplyOutlet Node

26

Objects required: BRANCH, Boiler Branch

BOILER:SIMPLE BRANCH, Supply Bypass Branch

PIPE BRANCH, Supply Outlet Branch

PIPE PLANT OPERATION SCHEME

HEATING LOAD RANGE BASED OPERATION

HEATING LOAD RANGE EQUIPMENT LIST


Hot Water Loop Supply Side (cont’d)

Boiler

Pla

nt

De

ma

nd

Sid

eH

ea

ting

Lo

op

Boiler Outlet Node

HW Pump

HW PumpOutlet Node

Byp

ass

BoilerInlet Node

HW SupplyInlet Node

HW SupplyOutlet Node

27

Chilled Water Supply Side

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Re

turn

Air

Mix

er

Zon

e A

ir Sp

litter


Pla

nt D

em

an

d S

ide

He

atin

g L

oop

CC

Byp

ass

CondenserBypass

VAV Box: ReHeat

VAV Box: ReHeat

Re

turn

Ho

t

Wate

r Mixe

rBypass


CondenserBypass

Ho

t Wate

r

Sp

litter


Relief Air

Outside Air



HW Pump

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Re

turn

Air

Mix

er

Zon

e A

ir Sp

litter


Pla

nt D

em

an

d S

ide

He

atin

g L

oop

CC

Byp

ass

CondenserBypass

VAV Box: ReHeat

VAV Box: ReHeat

Re

turn

Ho

t

Wate

r Mixe

rBypass


CondenserBypass

Ho

t Wate

r

Sp

litter


Relief Air

Outside Air



HW Pump

Boiler


HW Pump

28

Plant Supply SideCooling LoopCW Pump

Chiller

Byp

ass


Objects required: PLANT LOOP, Chiller Plant Chilled Water Loop BRANCH LIST CONNECTOR LIST SPLITTER MIXER

Chilled Water Supply Side

29

Objects required (cont’d): BRANCH, Chiller Plant Cooling Supply Inlet Branch

PUMP:VARIABLE SPEED BRANCH, Chiller Plant Chiller Branch

CHILLER:Electric BRANCH, Chiller Plant Cooling Supply Bypass Branch

PIPE

Chilled Water Supply Side (cont’d)


Chiller

Byp

ass


30

Objects required (cont’d): BRANCH, Chiller Plant Cooling Supply Outlet Branch

PIPE PLANT OPERATION SCHEMES

COOLING LOAD RANGE BASED OPERATION COOLING LOAD RANGE EQUIPMENT LIST

Chilled Water Supply Side (cont’d)


Chiller

Byp

ass


31

Condenser Loop Demand Side

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Retu

rn A

ir M

ixe

r

Zo

ne A

ir Sp

litter


Pla

nt D

em

an

d S

ide

Hea

ting

Loo

p

CC

Byp

ass

CondenserBypass

VAV Box: ReHeat

VAV Box: ReHeat

Retu

rn H

ot

Wa

ter M

ixer

Bypass


CondenserBypass

Hot W

ate

r

Sp

litter


Relief Air

Outside Air



HW Pump

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Retu

rn A

ir M

ixe

r

Zo

ne A

ir Sp

litter


Pla

nt D

em

an

d S

ide

Hea

ting

Loo

p

CC

Byp

ass

CondenserBypass

VAV Box: ReHeat

VAV Box: ReHeat

Retu

rn H

ot

Wa

ter M

ixer

Bypass


CondenserBypass

Hot W

ate

r

Sp

litter


Relief Air

Outside Air



HW Pump

Boiler


HW Pump

32


Chiller

Condenser SupplySide Loop

Condenser Bypass

Objects required: BRANCH LIST CONNECTOR LIST SPLITTER MIXER BRANCH, Condenser Demand Inlet

Branch PIPE

BRANCH, Chiller Condenser Branch CHILLER:Electric

BRANCH, Cond. Demand Bypass Branch PIPE

BRANCH, Cond. Demand Outlet Branch PIPE

Condenser Loop Demand Side

33

Condenser Supply Side

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Retu

rn A

ir M

ixe

r

Zone A

ir Splitte

r


Pla

nt D

em

and S

ide

Heatin

g L

oop

CC

Byp

ass

CondenserBypass

VAV Box:ReHeat

VAV Box:ReHeat

Retu

rn H

ot

Wate

r Mixe

rBypass


CondenserBypass

Hot W

ate

r

Splitte

r


Relief Air

Outside Air



HW Pump

North

Zone

East

Zone

Resistive

Zone


CW Pump

CoolingTower

Cond . Pump


ChillerBypass

Supply Fan

Retu

rn A

ir M

ixe

r

Zone A

ir Splitte

r


Pla

nt D

em

and S

ide

Heatin

g L

oop

CC

Byp

ass

CondenserBypass

VAV Box:ReHeat

VAV Box:ReHeat

Retu

rn H

ot

Wate

r Mixe

rBypass


CondenserBypass

Hot W

ate

r

Splitte

r


Relief Air

Outside Air



HW Pump

Boiler


HW Pump

34


Cooling Tower

CondenserPump

Condenser Bypass

Condenser DemandSide LoopObjects required:

CONDENSER LOOP BRANCH LIST CONNECTOR LIST SPLITTER MIXER BRANCH, Supply Inlet Branch

PIPE BRANCH, Condenser Branch

COOLING TOWER:Single Speed

Condenser Loop Supply Side

35


Cooling Tower

CondenserPump

Condenser Bypass

Condenser DemandSide LoopObjects required (cont’d):

BRANCH, Cond. Supply Bypass Branch

PIPE BRANCH, Supply Output Branch

PIPE CONDENSER OPERATION

SCHEMES COOLING LOAD RANGE BASED

OPERATION LOAD RANGE EQUIPMENT LIST

Condenser Loop Supply Side (cont’d)

36

Summary

Loops are backbone of HVAC simulation all equipment attached to air or fluid loops

Loop structure permits assembly of any system through input—not hardwired

Primary system may consist of four different loops: plant supply and demand, condenser supply and demand

Pumps regulate flow while attempting to meet requests on both sides of each loop pair

Individual loops may have components in series and parallel with some limitations

Lecture 22: Primary System Loops in EnergyPlus Material prepared by GARD Analytics, Inc. and...

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Transcript of Lecture 22: Primary System Loops in EnergyPlus Material prepared by GARD Analytics, Inc. and...