HVAC Equations, Concepts, and Definitions Presented By: David Sellers Senior Engineer; Facility Dynamics Engineering

A Few Acronyms and Definitions Acronyms • • •

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

• • • • • • • • •

AFD – Adjustable Frequency Drive AHU – Air Handling Unit ASHRAE – American Society of Heating Ventilating and Air Conditioning Engineers CV - Constant Volume HVAC – Heating Ventilating and Air Conditioning MOA – Minimum Outdoor Air Psych Chart – Psychrometric Chart VAV – Variable Air Volume VFD – Variable Frequency Drive VFD – (Adjustable Frequency Drive) VSD – Variable Speed Drive VFD – (Adjustable Frequency Drive)

AFD Acronym Definition AFD A Few Days AFD Abbreviated Functional Description AFD Accelerated Freeze-Drying (food processing) AFD Accident Free Discount (insurance) AFD Acid Fractionator Distillate AFD Acoustic Flat Diaphragm (electronics) AFD Acrofacial Dysostosis AFD Acrofacial Dysostosis, Catania Type AFD Active Format Descriptor AFD Adaptive Flexible Defense AFD Adaptive Flight Display AFD Adjustable Frequency Drive AFD Advanced Full-screen Debugger AFD African Development Foundation AFD African Development Fund AFD Aft Flight Deck AFD Agence Française de Développement (French Development Agency) AFD Air Force Depot AFD Airfield Database AFD Airport Facilities Directory AFD Alarm Format Definition AFD Albany Fire Department AFD Alcohol Free Day AFD Alexandria Fire Department AFD All Friggin' Day AFD Alt.fan.dragons (Usenet newsgroup) AFD Alternative Forms of Delivery (Canada) AFD Amarillo Fire Department (Amarillo, TX) AFD American Funds Distributors, Inc. AFD Amsterdam Fire Department AFD Ancillary Function Driver

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

AFD Angwin Fire Department (Angwin, CA) AFD Anticipatory Failure Determination AFD Apical Fibrobullous Disease AFD Approved for Design AFD Approximately Finite Dimensional AFD April Fool's Day AFD April Fools Day AFD Arc Fault Detection AFD Arc-Fault Detection AFD Architecture Flow Diagrams AFD Area Forecast Discussion (US National Weather Service) AFD Armed Forces Division AFD Arming & Fusing Device AFD Arming-Firing Device AfD Articles for Deletion (Wikipedia) AFD Ask for Details AFD assign fixed directory (US DoD) AFD Assistant Flight Director AFD Association Franèaise des Diabétiques AFD Athletic Field Design AFD Atlanta Fire Department AFD Austin Fire Department (Texas) AFD Autómata Finito Determinista AFD Automated File Designator AFD Automated Forging Design AFD Automatic Fault Detection AFD Automatic File Distribution AFD Automatic Fire Detection AFD Average Fade Duration AFD Away from Desk AFD Axial Flux Density AFD Axial Flux Difference AFD Active Format Description AFD Adaptive Forward Differencing AFD Adjustable Frequency Drives AFD Asus Foundation Drivers

DEFINITIONS AND USEFUL EQUATIONS

2

AFA2D Acronyms • • • • • • • • • •

AFD – Adjustable Frequency Drive AHU – Air Handling Unit ASHRAE – American Society of Heating Ventilating and Air Conditioning Engineers CV - Constant Volume HVAC – Heating Ventilating and Air Conditioning MOA – Minimum Outdoor Air Psych Chart – Psychrometric Chart VAV – Variable Air Volume VFD – Variable Frequency Drive (Adjustable Frequency Drive) VSD – Variable Speed Drive (Adjustable Frequency Drive)

DEFINITIONS AND USEFUL EQUATIONS

3

AFA2D Definitions • Sensible energy, QS (Btu’s, Btu’s/lb) Energy that causes a temperature change we can feel • Dry bulb temperature, Tdb (°F) An indication of sensible energy measured by a standard thermometer exposed to air; increasing dry bulb temperature = increasing sensible energy

DEFINITIONS AND USEFUL EQUATIONS

4

AFA2D

Definitions • Latent energy, QL (Btu’s, Btu’s/lb) Energy that is used to keep water in a vapor state • Wet bulb temperature, Twb (°F) An indication of latent energy measured by a standard thermometer with its bulb covered by a wick that is saturated with water and exposed to moving air; increasing wet bulb temperature = increasing latent energy DEFINITIONS AND USEFUL EQUATIONS

5

AFA2D

Definitions • Dew point temperature, Tdp (°F) The temperature at which water will begin to condense out of a given sample of air. Also an indication of moisture content; increasing dew point = increasing latent energy. At saturation Tdp = Twb = Tdb

DEFINITIONS AND USEFUL EQUATIONS

6

AFA2D Definitions • Enthalpy, h (Btu/lbdry air) A measure of the total energy content of air including both sensible and latent energy; increasing enthalpy = increasing energy content

DEFINITIONS AND USEFUL EQUATIONS

7

AFA2D

Definitions • Relative humidity, RH (%) The amount of water vapor in the air at a given temperature relative to what it could hold at that temperature; 100% = saturation; increasing specific humidity = increasing moisture content, increasing dew point, and increasing wet bulb temperature. In Antarctica, the relative humidity approaches 100% much of the time, just like in Florida after a thunderstorm DEFINITIONS AND USEFUL EQUATIONS

8

AFA2D

Definitions • Specific humidity, w (lbwater/lbdryair, grainswater/lbdryair) The ratio of the mass of water to the mass of dry air in a given sample of air; increasing specific humidity = increasing moisture content, increasing dew point, and increasing wet bulb temperature. In Antarctica, the specific humidity at a relative humidity of 100% is very low. In Florida, the specific humidity at a relative humidity of 100% is quite high relative to Antarctica. DEFINITIONS AND USEFUL EQUATIONS

9

AFA2D

Definitions • Psychrometrics The field of engineering concerned with the determination of physical and thermodynamic properties of gas-vapor mixtures.

DEFINITIONS AND USEFUL EQUATIONS

10

50

ALTITUDE: SEA LEVEL BAROMETRIC PRESSURE: 29.921 in. HG ATMOSPHERIC PRESSURE: 14.696 psia 1.0 1.0 

55

.025

45

-

0.8

SENSIBLE HEAT TOTAL HEAT

0 300

0.4

.024

2.0

Qs Qt

-2000 -100 0

4.0 -8.0 -8  .0

20 0

.0 -4 .0 -2 -1.0 .5 -0 -0.4 -0.3 -0.2 -0.1

0.5 0.3

5000

0.6

0.2 0.1

AFA2D

0

.023 55

80

40

0

85

.022

0

h W

.020

35

75

.019 80

30

90

65

15

60 45

30 25

0

5

Chart by: AKTON PSYCHROMETRICS, www.aktonassoc.com

20

10

DEFINITIONS AND USEFUL EQUATIONS

15

90

85

80

75

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65

60

55

50

45

40

10

35

30

15

25

10

35

30

25

20

20

5

15 15

10 10

0

5

0 0

-5

-5

5

30

40

20

0

% 15

VE ATI REL 8% 6% 4% 2%

105

35

0 550 40

100

40

55

95

45

DRY BULB TEMPERATURE - °F

60

10

Y IDIT HUM

110

50

25 %

80

55 70

EN TH AL PY

-B

TU

60

.016 .015 .014 45 .013 .012 .011 .010

40

.009 .008 .007 .006 .005 35 .004 .003 .002

115

UN D

PE R

PO

70

20

HUMIDITY RATIO - POUNDS MOISTURE PER POUND DRY AIR

DR Y

AI R

75

25

65

5

50

.017 70

O F

• Psychrometric Chart Scary, complicated looking graph.

.018

.001 120

Definitions

.021

500

1000

150 0

ENTHALPY HUMIDITY RATIO

30

20 25 ENTHALPY - BTU PER POUND OF DRY AIR

11

AFA2D Definitions • Psychrometric Equations The alternative to using the psych chart.

DEFINITIONS AND USEFUL EQUATIONS

12

50

ALTITUDE: SEA LEVEL BAROMETRIC PRESSURE: 29.921 in. HG ATMOSPHERIC PRESSURE: 14.696 psia 1.0 1.0 

55

.025

45

-

0.8

SENSIBLE HEAT TOTAL HEAT

0 300

0.4

.024

2.0

Qs Qt

-2000 -100 0

4.0 -8.0 -8  .0

20 0

.0 -4 .0 -2 -1.0 .5 -0 -0.4 -0.3 -0.2 -0.1

0.5 0.3

5000

0.6

0.2 0.1

AFA2D

0

.023 55

80

40

0

85

.022

0

Definitions

.021

500

1000

150 0

ENTHALPY HUMIDITY RATIO

h W

.020

35

75

.019 80

.018

• Psychrometric Chart Graphical tool that allows the informed user to determine multiple parameters like enthalpy, dew point, relative humidity, specific humidity, dry bulb temperature and wet bulb temperature for a sample of air if any two of them are know. 30

70

90

65

15

60

45

30 25

0

5

Chart by: AKTON PSYCHROMETRICS, www.aktonassoc.com

20

10

DEFINITIONS AND USEFUL EQUATIONS

15

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65

60

55

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40

10

35

30

15

25

10

35

30

25

20

20

5

15 15

10 10

0

5

0 0

-5

-5

5

30

40

20

0

% 15

VE ATI REL 8% 6% 4% 2%

105

35

0 550 40

100

40

55

95

45

DRY BULB TEMPERATURE - °F

60

10

Y IDIT HUM

110

50

25 %

80

55

70

EN TH AL PY

-B

TU

60

.015 .014 45 .013 .012 .011 .010

40

.009 .008 .007 .006 .005 35 .004 .003 .002

115

20

PE R

PO

UN D

O F

65

.016

.001 120

DR Y

AI R

75

25

HUMIDITY RATIO - POUNDS MOISTURE PER POUND DRY AIR

.017

70

5

50

30

20 25 ENTHALPY - BTU PER POUND OF DRY AIR

13

50

ALTITUDE: SEA LEVEL BAROMETRIC PRESSURE: 29.921 in. HG ATMOSPHERIC PRESSURE: 14.696 psia 1.0 1.0 

55

.025

45

-

0.8

0 300

20 00

0.2 0.1

5000

0.4

-2000 -100 0

0 -4. .0 -2 -1.0 .5 -0 -0.4 -0.3 -0.2 -0.1

0 .5

.024

2.0 4. -8.0 0 -8  .0

Qs Qt

0

0

.023 55

80

40

85

.022 .021

500

1000

150 0

ENTHALPY HUMIDITY RATIO

h W

.020

35

75

.019 80

.018

30

70

PE R

20

65

90

55

35

45

30 25

0 Chart by: AKTON PSYCHROMETRICS, www.aktonassoc.com

20

90

85

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45

10

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15

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10

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25

20

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15 20

5

10

0

5

0 0

-5

-5

5

10

15

0

% 15

30

40

20

0 550 40

Dry Bulb Temperature Axis and Lines 5 1 1 2 0

5

DEFINITIONS AND USEFUL EQUATIONS

8% 6% 4% 2%

REL

H VE ATI

105

40

55

100

45

DRY BULB TEMPERATURE - °F

60

10

Y IDIT UM

110

70

50

25 %

80

Increasing temperature 60 and energy content

95

15

EN TH

AL PY

-B

TU

60

.016 .015 .014 45 .013 .012 .011 .010

40

.009 .008 .007 .006 .005 35 .004 .003 .002

115

PO UN D

O F

65

HUMIDITY RATIO - POUNDS MOISTURE PER POUND DRY AIR

75

25

DR Y

AI R

70

5

50

.017

.001 120

SENSIBLE HEAT TOTAL HEAT

0.3

0.6

30

25 0 ENTHALPY - BTU PER POUND OF DRY AIR

14

50

ALTITUDE: SEA LEVEL BAROMETRIC PRESSURE: 29.921 in. HG ATMOSPHERIC PRESSURE: 14.696 psia 1.0 1.0 

55

.025

45

-

0.8 -100 0

0

0

.023 55

80

40

85

.022 .021

500

1000

150 0

ENTHALPY HUMIDITY RATIO

h W

.020

35

75

.019 80

.018

30

PE R

20

65

90

15

45

25

0 Chart by: AKTON PSYCHROMETRICS, www.aktonassoc.com

5

20

10

15

DEFINITIONS AND USEFUL EQUATIONS

90

85

80

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10

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15 20

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0

5

0 0

-5

-5

5

10

15

0

30

40

20

% 15

8% 6% 4% 2%

95

35

0 550 40

REL

H VE ATI

105

40

55

100

45

DRY BULB TEMPERATURE - °F

60

10

Y IDIT UM

110

60

70

50

25 %

80

55

EN TH

AL PY

-B

TU

60

HUMIDITY RATIO - POUNDS MOISTURE PER POUND DRY AIR

PO UN D

O F

65 Increasing moisture and 70 energy content

.016 .015

.014 45 .013 .012 .011 .010

40

.009 .008 .007 .006

.005 35 .004 .003 .002

115

DR Y

AI R

75

25

30

50

.017 70

5

Specific Humidity Axis and Lines

0 300

20 00

0.2 0.1

5000

0.4

-2000

0 -4. .0 -2 -1.0 .5 -0 -0.4 -0.3 -0.2 -0.1

0 .5

.024

2.0 4. -8.0 0 -8  .0

Qs Qt

.001 120

SENSIBLE HEAT TOTAL HEAT

0.3

0.6

30

20 25 ENTHALPY - BTU PER POUND OF DRY AIR

15

50

ALTITUDE: SEA LEVEL BAROMETRIC PRESSURE: 29.921 in. HG ATMOSPHERIC PRESSURE: 14.696 psia 1.0 1.0 

55

.025

45

-

0.8

SENSIBLE HEAT TOTAL HEAT

0 300

20 00

0.2 0.1

5000

0.4

.024

2.0 4. -8.0 0 -8  .0

Qs Qt

0 -4. .0 -2 -1.0 .5 -0 -0.4 -0.3 -0.2 -0.1

0 .5 0.3

0.6

-2000 -100 0

0

0

.023 55

80

40

85

.022 .021

500

1000

150 0

ENTHALPY HUMIDITY RATIO

h W

.020

35

Increasing.019 relative 50 .018 energy humidity and .017 content

75

PO UN D

O F

65 70

20

PE R

Relative Humidity Lines and Saturation Curve 15 (100% RH)

65

AL PY

90

-B

TU

60

45

30 25

0 Chart by: AKTON PSYCHROMETRICS, www.aktonassoc.com

5

20

10

15

DEFINITIONS AND USEFUL EQUATIONS

90

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10

0

5

0 0

-5

-5

5

10

15

0

30

40

20

% 15

8% 6% 4% 2%

95

35

60

5

0 550 40

REL

H VE ATI

105

40

55

100

45

DRY BULB TEMPERATURE - °F

60

10

Y IDIT UM

110

60

70

50

25 %

EN TH

80

55

.016 .015 .014 45 .013 .012 .011 .010

40

.009 .008 .007 .006 .005 35 .004 .003 .002 .001 120

75

25

DR Y

AI R

70

115

30

HUMIDITY RATIO - POUNDS MOISTURE PER POUND DRY AIR

80

30

20 25 ENTHALPY - BTU PER POUND OF DRY AIR

16

50

ALTITUDE: SEA LEVEL BAROMETRIC PRESSURE: 29.921 in. HG ATMOSPHERIC PRESSURE: 14.696 psia 1.0 1.0 

55

.025

45

-

0.8

0.2 0.1

5000

0.4

0 300

20 00

0 -4. .0 -2 -1.0 .5 -0 -0.4 -0.3 -0.2 -0.1

0 .5

.024

2.0 4. -8.0 0 -8  .0

Qs Qt

-2000 -100 0

0

0

.023 55

80

40

85

.022 .021

500

1000

150 0

ENTHALPY HUMIDITY RATIO

h W

.020

35

75

.019 80

.018

30

PO UN D

70

PE R

20

60 65

AL PY

90

-B

TU

Wet Bulb temperature Axis15 and Lines

45

30 25 20

0 Chart by: AKTON PSYCHROMETRICS, www.aktonassoc.com

5

20

10

15

DEFINITIONS AND USEFUL EQUATIONS

90

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30

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10

30

25

20

35

40

15 20

5

10

0

5

0 0

-5

-5

5

10

15

0

E TIV ELA R %

30

40

8 6% 4% 2%

105

35

.016 .015 .014 45 .013 .012 .011 .010

40

.009 .008 .007

.006 Increasing temperature % .005 35 15 and energy content ITY

0 550 40

100

40

55

95

45

ID HUM

110

60

10

DRY BULB TEMPERATURE - °F

60

70

50

25 %

EN TH

80

55

.004 .003 .002

115

O F

65

HUMIDITY RATIO - POUNDS MOISTURE PER POUND DRY AIR

75

25

DR Y

AI R

70

5

50

.017

.001 120

SENSIBLE HEAT TOTAL HEAT

0.3

0.6

30

20 25 ENTHALPY - BTU PER POUND OF DRY AIR

17

50

Note that constant enthalpy and constant wet bulb temperature lines are almost but not quite parallel

55

.025

45

-

0.8

SENSIBLE HEAT TOTAL HEAT

.024

-2000

-100 0

0

0

.023 55

80

40

85

.022 .021

500

h W

.020

35

75 Increasing enthalpy or 80 energy content

30

.019 .018

75

25

DR Y

AI R

70

PO UN D

O F

65 70

PE R

20

65

90

15

45

30 25

0 Chart by: AKTON PSYCHROMETRICS, www.aktonassoc.com

5

20

10

15

DEFINITIONS AND USEFUL EQUATIONS

90

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60

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15 20

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0

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0 0

-5

-5

5

10

15

0

30

40

20

% 15

8% 6% 4% 2%

95

35

0 550 40

REL

H VE ATI

105

40

55

100

45

DRY BULB TEMPERATURE - °F

60

10

Y IDIT UM

110

60

70

50

25 %

80

55

EN TH

AL PY

-B

TU

60

5

50

.017 HUMIDITY RATIO - POUNDS MOISTURE PER POUND DRY AIR

1000

150 0

ENTHALPY HUMIDITY RATIO

.016 .015 .014 45 .013 .012 .011 .010

40

.009 .008 .007 .006 .005 35 .004 .003 .002

115

0 300

20 00

0.2 0.1

5000

0.4

2.0 4. -8.0 0 -8  .0

Qs Qt

0 -4. .0 -2 -1.0 .5 -0 -0.4 -0.3 -0.2 -0.1

0 .5

0.3

0.6

.001 120

ALTITUDE: SEA LEVEL BAROMETRIC PRESSURE: 29.921 in. HG ATMOSPHERIC PRESSURE: 14.696 psia 1.0 1.0 

30

20 25 ENTHALPY - BTU PER POUND OF DRY AIR

18

50

ALTITUDE: SEA LEVEL BAROMETRIC PRESSURE: 29.921 in. HG ATMOSPHERIC PRESSURE: 14.696 psia 1.0 1.0 

55

.025

45

-

0.8

SENSIBLE HEAT TOTAL HEAT

0 300

0.4

.024

2.0

Qs Qt

-2000 -100 0

4.0 -8.0 -8  .0

20 0

.0 -4 .0 -2 -1.0 .5 -0 -0.4 -0.3 -0.2 -0.1

0.5 0.3

5000

0.6

0.2 0.1

AFA2D

0

.023 55

80

40

0

85

.022

0

.021

500

1000

150 0

Definitions

ENTHALPY HUMIDITY RATIO

h W

.020

35

75

.019 80

.018

• Psychrometric Chart If you know the dry bulb temperature and relative humidity entering and leaving a cooling coil, you can plot those points on the chart and determine: • The entering and leaving enthalpy (energy content) • The load (how much energy was transferred) • The amount of moisture condensed, if any • The entering and leaving dew point temperature • The entering and leaving wet bulb temperature 30

70

90

65

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60

45

30

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0

5

Chart by: AKTON PSYCHROMETRICS, www.aktonassoc.com

20

10

DEFINITIONS AND USEFUL EQUATIONS

15

90

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10

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10

35

30

25

20

20

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15 15

10 10

0

5

0

0

-5

-5

5

30

40

20

0

% 15

VE ATI REL 8% 6% 4% 2%

105

35

0 550 40

100

40

55

95

45

DRY BULB TEMPERATURE - °F

60

10

Y IDIT HUM

110

50

25 %

80

55

70

EN TH AL PY

-B

TU

60

.015 .014 45 .013 .012 .011 .010

40

.009 .008 .007 .006 .005 35 .004 .003 .002

115

20

PE R

PO

UN D

O F

65

.016

.001 120

DR Y

AI R

75

25

HUMIDITY RATIO - POUNDS MOISTURE PER POUND DRY AIR

.017

70

5

50

30

20 25 ENTHALPY - BTU PER POUND OF DRY AIR

19

Learn More about Using a Psych Chart HTML version at: http://www.buildingcontrolworkbench.com Downloadable .pdf at: http://customer.honeywell.com/techlit/pdf/770000s/77-E1100.pdf

DEFINITIONS AND USEFUL EQUATIONS

20

AFA2D

Definitions • Cooling A process that removes energy. For a space, this is often accomplished by circulating air through it at a temperature below the required set point. For an airstream, this is often accomplished by passing it over a surface that is below the required supply temperature. If the surface is below the dew point of the air stream, dehumidification (moisture removal) will also occur. DEFINITIONS AND USEFUL EQUATIONS

21

AFA2D Definitions • Heating A process that adds energy. For a space, this is often accomplished by circulating air through it at a temperature above the required set point. For an airstream, this is often accomplished by passing it over a surface that is above the required supply temperature.

DEFINITIONS AND USEFUL EQUATIONS

22

AFA2D Definitions • Freezing A condition that occurs when water is cooled to the point where it changes phase from a solid to a liquid.

DEFINITIONS AND USEFUL EQUATIONS

23

AFA2D Definitions • Water Damage A condition that occurs after frozen water contained in a HVAC coil changes back to the liquid phase.

DEFINITIONS AND USEFUL EQUATIONS

24

AFA2D Definitions • Expletive A generic reference to the field terminology used to describe and discuss water damage when it occurs.

DEFINITIONS AND USEFUL EQUATIONS

25

AFA2D

Definitions • Preheat A process that heats a fluid stream to prepare it for a subsequent HVAC process. In air handling systems, this process is used to raise subfreezing air above freezing to protect water filled elements down stream from damage due to freezing. See the Functional Testing Guide (www.peci.org/ftguide) Air Handling System Reference Guide Chapter 5 – Preheat, Table 5.1 to contrast preheat, reheat and heating applications DEFINITIONS AND USEFUL EQUATIONS

26

AFA2D Definitions • Reheat A process that uses heat to warm air being delivered to a zone to prevent over cooling. The temperature of the air was set by the need to hit a dehumidification target or by the requirements of another zone, so it can not be raised at the central system. The volume can not be reduced because it has been set to assure proper ventilation (contaminant control). In the limit, reheat will raise the supply temperature to the zone temperature but not above it.

DEFINITIONS AND USEFUL EQUATIONS

27

AFA2D Definitions • Economizer Process An HVAC process designed to minimize the energy required to cool a building

DEFINITIONS AND USEFUL EQUATIONS

28

AFA2D Definitions • Constant Volume System An air handling or pumping process that, in general terms, is always moving the same amount of water or air. Pump or fan energy is fairly steady state. Supply and return temperature differences will tend to vary with load. In water systems, the control valves will tend to be three-way valves.

DEFINITIONS AND USEFUL EQUATIONS

29

AFA2D Definitions • Variable Volume System/Variable Air Volume System (VAV) An air handling or pumping process that varies the flow of water or air to match the requirements of the load.. Supply and return temperature differences will tend to hold steady regardless of load. In water systems, the control valves will tend to be two-way valves.

DEFINITIONS AND USEFUL EQUATIONS

30

Benchmarks Contrasting Utility Consumption with Your Peers

DEFINITIONS AND USEFUL EQUATIONS

31

Average Daily Consumption Analysis Contrasting Utility Consumption with Other Metrics

Peak electrical consumption may be driven by the need to cool

DEFINITIONS AND USEFUL EQUATIONS

32

Occupancy may also be a driver for electrical consumption, but maybe not

FOCUSING OUR EFFORT

33

Gas consumption tends to be driven by the need to heat

FOCUSING OUR EFFORT

34

Gas consumption seems to be unrelated to occupancy, which is not always true for a hotel due to the domestic hot water loads

FOCUSING OUR EFFORT

35

Interval Data Consumption Analysis Looking at Variations in Hour by Hour Patterns

DEFINITIONS AND USEFUL EQUATIONS

36

Sensible Heating or Cooling Loads

DEFINITIONS AND USEFUL EQUATIONS

37

Where did the Units Conversion Constant Come From?

DEFINITIONS AND USEFUL EQUATIONS

38

Where did the Units Conversion Constant Come From?

DEFINITIONS AND USEFUL EQUATIONS

39

Specific Heat and Density of Air versus Temperature

0.260

0.24

0.250

0.20

0.240

0.16

0.230

0.12

0.220

0.08

0.210

0.04

0.200 -100

0

100

200

300

400

Density, lb/cubic foot

Specific Heat, btu/lb-°F

Physical Properties can Vary …

0.00 500

Temperature,°F Specific Heat

Density of Dry Air DEFINITIONS AND USEFUL EQUATIONS

Density of Saturated Air 40

… so Conversion Constants Only are Valid for a Range of Conditions

Versus 1.08 in the equation in common use

DEFINITIONS AND USEFUL EQUATIONS

41

… so Conversion Constants Only are Valid for a Range of Conditions

Virtually the same as for cold dry air DEFINITIONS AND USEFUL EQUATIONS

42

… so Conversion Constants Only are Valid for a Range of Conditions

Versus 1.08 in the equation in common use

DEFINITIONS AND USEFUL EQUATIONS

43

… so Conversion Constants Only are Valid for a Range of Conditions

Significantly different from hot saturated air and the value in the equation in common DEFINITIONS AND USEFUL EQUATIONS

44

Latent Load

DEFINITIONS AND USEFUL EQUATIONS

45

Total Load

DEFINITIONS AND USEFUL EQUATIONS

46

Water Side Load

DEFINITIONS AND USEFUL EQUATIONS

47

The Relationship Between Flow and Velocity

DEFINITIONS AND USEFUL EQUATIONS

48

The Relationship Between Velocity and Velocity Pressure

DEFINITIONS AND USEFUL EQUATIONS

49

Fan Power

DEFINITIONS AND USEFUL EQUATIONS

50

Unit Conversions for Working with SI Units

DEFINITIONS AND USEFUL EQUATIONS

51

Pump Power

DEFINITIONS AND USEFUL EQUATIONS

52

Unit Conversions for Working with SI Units

DEFINITIONS AND USEFUL EQUATIONS

53

Calculating Power Into the Pump Motor as kilowatts

DEFINITIONS AND USEFUL EQUATIONS

54

Calculating Power Into the Fan Motor as kW

DEFINITIONS AND USEFUL EQUATIONS

55

Calculating Energy Use

What can cause the load to vary? • Changes in ambient conditions • Changes in internal conditions • Changes in a production process Just About Everything!

DEFINITIONS AND USEFUL EQUATIONS

56

The Square Law

DEFINITIONS AND USEFUL EQUATIONS

57

Conservation of Mass and Energy The Goes Inta’s gotta equal the Goes Outa’s Dr. Al Black

The tee where the building return meets the bypass line is a node in the system ‒ Energy into and out of the node must be equal ‒ Mass flow into and out of the node must be equal

Re Bypass Flow at Bypass Temperature Chiller Flow at Chiller Entering Temperature

DEFINITIONS AND USEFUL EQUATIONS

Return Flow at Return Temperature

58

Conservation of Mass and Energy The Goes Inta’s gotta equal the Goes Outa’s Dr. Al Black

The tee where the building return meets the bypass line is a node in the system ‒ Energy into and out of the node must be equal ‒ Mass flow into and out of the node must be equal ‒ This is a steady state, steady flow process described by the continuity equation

Re Bypass Flow at Bypass Temperature Chiller Flow at Chiller Entering Temperature

DEFINITIONS AND USEFUL EQUATIONS

Return Flow at Return Temperature

59

Conservation of Mass and Energy The Goes Inta’s gotta equal the Goes Outa’s Dr. Al Black

The tee where the building return meets the bypass line is a node in the system ‒ Energy into and out of the node must be equal ‒ Mass flow into and out of the node must be equal ‒ This is a steady state, steady flow process described by the continuity equation ‒ For a tee in the pipe, the continuity equation can be simplified

Re Bypass Flow at Bypass Temperature Chiller Flow at Chiller Entering Temperature

DEFINITIONS AND USEFUL EQUATIONS

Return Flow at Return Temperature

60

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

61

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

62

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

63

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

64

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

65

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

66

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

67

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

68

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

69

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

70

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

71

Conservation of Mass and Energy Doing the Algebra

DEFINITIONS AND USEFUL EQUATIONS

72