Chicago water econ. - file · Web viewCENTRAL CHILLED. WATER SYSTEMS (SEE) MODEL ANALYSIS. Waterside Economizers. Kirby Nelson. PE. ... Chapter 2 deals with increasing supply air

CHICAGOCENTRAL CHILLEDWATER SYSTEMS

(SEE) MODEL ANALYSIS

Waterside Economizers

Kirby Nelson PE5/5/2023

Kirby Nelson PE Page 1

Contents:Executive Summary (a) ASHRAE JOURNAL Articles of June 2014 & August 2014 (b) System Energy Equilibrium (SEE) Modeling (c) BASE BUILDING-Large office of (PNNL) studyCHAPTER 1: Peak Day Performance & Performance at 50F DB & 45F WBCHAPTER 2: Increase supply air temperature from 55F to 60F NOMENCLATURE:

EXECUTIVE SUMMARY(a) ASHRAE JOURNAL Articles of June 2014 & August 2014In the June 2014 ASHRAE Journal Taylor presents an article titled, How to Design & Control Waterside Economizers, and in the August 2014 issue Nall presents a more detail discussion titled, Waterside Economizers & 90.1. Both articles advocate waterside economizers but neither provides justification; analysis of the concept with detail energy models is, I suggest, required before inclusion into 90.1-2013. To my knowledge none of the models advocated by ASHRAE or Pacific Northwest National Laboratory (PNNL) can adequately address this problem. I have put the problem to a System Energy Equilibrium (SEE) model that is consistent with the laws of thermodynamics. The model is of a Chicago half million square foot 13 story large office as defined by (PNNL) in its study of 90.1-2010, (see link below). Chapter 1 shows that a water economizer can have little effect on the kW demand of the system. Chapter 1 does not deal with increasing air supply temperature, increasing water supply temperature, and the effect of solar. These issues and others will be addressed in upcoming chapters. Chapter 2 deals with increasing supply air temperature from 55F to 60F. The result is not good; the system kW demand increases. Kirby Nelson P.E.Life Member ASHRAE


(b) System Energy Equilibrium (SEE) ModelingFollowing is a brief summary of the characteristics of system energy equilibrium (SEE) models and the (SEE) model experience of the author.(SEE) ModelSystem energy equilibrium (SEE) models and schematics can be developed for any condition of weather and operational conditions that may occur in a real system. The requirement for the (SEE) model/schematic is always the same; it must duplicate the performance of the equipment that make up the system and it must obey the laws of thermodynamics and physics and include the nonlinear characteristics of the components of the system. The (SEE) model/schematics defined here assume all chillers are of the same size and model and the air handlers are the same size and model and equally loaded.Math models that duplicate the real time performance of systems are standard practice in the space program and in the development of military products such as missiles, cannons, and other complex systems. The System Energy Equilibrium (SEE) Model presented here duplicates the thermodynamic and nonlinear performance of real systems and therefore can define the best possible performance of a system consistent with the design and control concepts incorporated in the design i.e. the theoretical performance of the system.The author has found that the design and control concepts advocated by ASHRAE and Pacific Northwest National Laboratory (PNNL) yields a design that requires more demand kW and therefore energy than does a more conventional design and control strategy. These differences in design and control are detailed in other papers on this site.

Kirby Nelson experienceSystem Energy Equilibrium (SEE) modeling is not a new concept. The author was involved in this approach to modeling in the 1970’s designing military products and then as corporate energy manager for Texas Instruments Inc. modeling building systems.The concept is to simply write the basic physics and thermodynamic equations of the system and simultaneously solve the set of equations with a computer. The results will duplicate the performance of the real system if the equations are correct; nonlinear characteristics input and equipment efficiencies input. The equations can be, and should be, corrected by iterating between the real performance data verses the model and updating the model equations.

The first HVAC paper published by Kirby using this approach was in the ASHRAE Journal of December 2006. "7 Upgrades to Reduce Building Electrical Demand"In March 2010 he had an article in Engineered Systems "Central Chilled Water System Modeling" & July 2010 an HPAC article on chiller selection "Central-Chiller Plant Modeling"In 2011 a 5 article series in HPAC dealing with Primary/Secondary vs. Primary-Only Pumping. The second article dealt with the efficient control of a P/S plant and the third article with efficient control of a P-only plant. The fourth article was "Anatomy of Load delta-T" and the fifth added the building and air side equipment to the analysis.In 2012 Kirby presented two advance technical papers at ASHRAE Chicago 2012. (CH-12-002) title “Simulation Modeling of a Central Chiller Plant” and (CH-12-003) "Simulation Modeling of Central Chilled Water Systems".Since Chicago he has continued to develop the concept of (SEE) modeling and has entered into discussions on ASHRAExCHANGE on the ASHRAE web site. Kirby’s analysis of these issues and others to follow can be viewed at http://kirbynelsonpe.com/


Personal note:I first became involved in this approach to system analysis/design in the late 1960's and early 1970's in the design of military products, Shrike Missile, Lacer Guided Bombs, Anti-Tank Projectiles, a helicopter mounted cannon to shoot electronic sensors, and other systems including dynamics of impact with soil, as an engineer with Texas Instruments Inc. (TI). An analog/digital computer was the key to the success of the models. I became Corporate Energy Manager for (TI) in 1974 and continued to use this approach to define energy saving projects for over 30 million square feet of (TI) facilities. I also used the Control Data program ECUBE and DOE. I lost access to the analog/digital computer in 1982 when I left (TI) and only recently returned to an effort to model central chilled water systems using Excel; the only tool I have that can solve a set of simultaneous equations. My objective was and is to demonstrate the concept of (SEE) Modeling & (SEE) Schematics to the HVAC community believing the approach is a powerful and needed tool in the quest to improve the energy efficiency of buildings.Critical review is solicited.Best Regards, Kirby Nelson PE [email protected] Member ASHRAE

(c) Base BuildingThe Chicago Large Office as defined by Pacific Northwest National Laboratory (PNNL) in their study of ASHRAE STD 90.1-2010 is chosen as the benchmark building for the (SEE) modeling analysis.The study by Pacific Northwest National Laboratory (PNNL) of ASHRAE Standard 90.1-2010 defines a large office building that is used as the base building for this study. The (PNNL) study defines the building characteristics, schedules, control, and HVAC equipment of the large office building defined here as the “ASHRAE Design”. Further the ASHRAE Journal of July 2011 defines “Optimizing Design & Control of Chilled Water Plants” by Taylor, which is used to define the plant of the “ASHRAE Design”. This (SEE) modeling analysis has found that the “ASHRAE Design” calls for design and control concepts that significantly increase the energy consumption of the system compared to a “(min kW) Design”. The “(min kW) Design” is, I believe, less first cost. The (PNNL) study can be viewed at;http://www.energycodes.gov/sites/default/files/documents/BECP_Energy_Cost_Savings_STD2010_May2011_v00.pdf orhttp://www.energycodes.gov/achieving-30-goal-energy-and-cost-savings-analysis-ashrae-standard-901-2010

The (PNNL) study defines the building as given by Figure, a 13 story office with 498,600 square feet of air conditioned space.

FIGURE: Building description


http://www.energycodes.gov/achieving-30-goal-energy-and-cost-savings-analysis-ashrae-standard-901-2010



mailto:[email protected]

CHAPTER 1: Performance at peak day weather & 50F DB-45F WB

45 45 45 45 45 45 45 45 45 45 45 45

50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0

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FIGURE 1-1: Weather conditions

732 754 754658

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(50F DB-45F WB) (kW) Design day (kW)

FIGURE 1-2: Total system kW

Figure 1-1 illustrates the two weather profiles to be evaluated in this chapter 1.

The total system kW is very different for the two conditions as illustrated by Figure 1-2. Perimeter heat is required at night resulting in greater kW demand for the winter conditions.


Figure 1-3 gives the (SEE) schematic at 4PM at peak design hour. The peak system kW is also shown on Figure 1-2 above. This (SEE) schematic is

consistent with the laws of thermodynamics and the manufactures performance data. Nomenclature is given at the end of this paper.BLD ft2 = 498600 %clear sky = 100.0% InfilLat-ton = 47.55

Condenser # floors = 13 Tdry-bulb = 91.7 Infil-CFM = 6811 <(cond)ton= 543 Pipesize-in =6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 81.8 Infilsen-ton = 11.5

TCR= 104.8 > gpmT= 1800 > (ewt)T= 103 tfan-kW= 8.3 N/S wall ft2 = 40,560 WallNtrans ton= 3.76TCR-app= 1.32 (H)T-total= 74.7 (H)T-static = 9.9 Tfan-kW= 16.6 E/W wall ft2 = 27,008 WallStrans ton= 4.19

(COND)ton= 1086 PT-heat = -1.47 Trange= 14.5 tfan-%= 100% Wall % glass= 37.5% WallEtrans ton= 3.32(H)cond= 51.3 < pT-kW= 30.5 < (lwt)T = 89.0 tton-ex= -545 Glass U = 0.55 WallWtranston= 2.50 WallTot trans ton = 13.8

(cond)ft/sec= 10.8 EfTpump= 0.83 Tapproach = 7.2 T#= 2 Wall U = 0.09 GlassN trans ton = 13.04Ptower # = 2 T-Ton-ex= -1091 Glass SHGC = 0.40 GlassS trans ton = 13.04

Trg+app = 21.7 Wall emitt = 0.55 GlassE-trans ton = 8.68Compressor ASHRAE Design RoofTrans ton = 31.8 GlassW-trans ton = 8.68 GlassTot-trans-ton= 43.4

(chiller)kW= 279 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 7.1(chiller)lift= 62.0 Large Office Peopleton = 60 kW GlassS-solar-ton = 22.3(chiller)%= 100% Peak day Design 4PM plugton = 93 328 GlassE-solar ton = 4.7(chiller)#= 2 Weather %clear sky = 1.00 Lightton= 115 404 GlassW-solar ton = 33.1 GlassTot-solar-ton = 67.2

(CHILLER)kW= 558 conditions Tdry bulb = 91.7 (int-cfm)to-per-ret= 176135 BLD kW= 731.4 (int cfm)per-ton = 31.70 >(chiller)kW/ton= 0.607 Twet bulb = 81.8 Total Bldint-ton = 299.3 AHU kW= 499.7 Tot Bldper-sen-ton = 167.6 vPlant kW = 660.1 Tstat-int= 75.0 SITE kW = 1231.2 Tstat-per = 73.0 return

(Bld)int.air-ton= -299.3 ^ Design 4PM ^ (Bld)per.air-ton= -167.6 airTair supply int= 56.12 ASHRAE Design Tair supply per= 56.72

^ ABS Bld Ton = 466.89 ^ > Evaporator Ton kW Ton kW V

(evap)ton= 459.9 (fan)int-ter= 17.7 62.4 (fan)per-ter= 17.7 62.4TER= 42.8 Theat-air= 55.0

TER-app= 1.29 (D)heat = 0.0 0.0 ^ EVAPton= 920 Treheat air = 55.0

(H)evap= 51.9 (D)reheat = 0.0 0.0(evap)ft/sec= 10.44 62.4

(evap)des-ft/sec= 10.44 (D)int-air-ton= -317.0 Interior (D)per-air-ton= -205.9 Peri ^ V Tair coils = 55.00 duct Tair coils= 55.00 duct

gpmevap= 1200 Psec-heat-ton = -2.4 (D)int-CFM= 176,135 ^ (D)per-CFM= 114,401 ^(lwt)evap = 44.06 > Psec-kW= 37.5 > (ewt)coil= 44.1 >>>(Coil)sen-ton= 644 ^ (coil)gpm= 42.5 ^

(H)pri-total= 61.4 v Efdes-sec-p = 0.80 (coil)cap-ton= 34.3 UAdesign= 2.66 ^ (H)pri-pipe= 2.5 Tbp= 44.06 Efsec-pump = 0.78 (coil)H2O-ft/sec= 1.17 COIL UA= 2.61

(H)pri-fitings= 7.0 gpmbp= -96 (H)sec= 140 PLANTton = 908 (coil)des-ft/sec= 1.20 (one coil)ton= 34.91(Ef)c-pump= 0.81 (H)pri-bp= 0.02 (H)sec-pipe= 78 LMTD= 13.12 (H)coil= 2.0 VPc-heat-ton= -0.93 v (H)sec-bp= 0.00 Pipesize-in = 8.0 (COIL)L+s-ton= 908 ^ ^ ^ (H)coil-des= 2.1

^ < pc-kW= 17.1 (ewt)evap = 62.45 < (gpm)sec= 1104 < (lwt)coil= 64.1 <<<< Tair VAV= 79.61 TBLD-AR = 73.00Pchiller-# = 2 (FAN)VAV-CFM= 290,536 (Air)ret-CFM = 297,347 Return

Chicago 4PM All ElectricFuel Heat (FAN)ton-VAV= 82.0 (FAN)ret-kW= 87 FanPerformance 4PM Design kW THERM (FAN)kW-VAV= 288 (FAN)ret-ton= 24.6 V

chillerkW/evapton= 0.607 BLD.kW= 731.4 ^ (Air)ret-ton = 506.3(plant)kW/site ton= 0.727 (Fan)kW = 499.7 26 F.A.Inlet ^ Tar-to-VAV = 73.92CCWSkW/bld ton= 2.48 Ductheat= 0.0 0.00 statFA= 42 26 VAV FANS VAVret-ton = 423.5WeatherEin-ton = 648.0 (FA)heat= 0.0 0 TFA to VAV = 91.7 > Tret+FA = 76.48 InfilVAV-Lat-ton = 39.77(Site)kW-Ein-ton = 350.2 Heat total = 0.0 0.00 Tdry bulb = 91.7 >(FA)sen-ton = > 138.1 (dh) = 5.546 < VAVret-CFM = 248,719 <PlantkW-Ein-ton = 187.7 PlantkW= 660.1 Fresh air > >>> > (FA)CFM= 41,817 > Efan-VSD= 0.657 InfilCFM-ton = 11.6 V

Total Ein-ton = 1186 SystkW = 1891.3 1891.3 Twet bulb = 81.8 > (FA)Lat-ton= 224.2Pumptot-heat-ton = -4.8 (FA)kW= 0.0 ExLat-ton = -7.8

AHU ExLat-ton = -7.8 BLD.kW= 731.4 SEE SCHEMATIC ExCFM = -48,628AHU Exsen-ton = -82.8 CCWSkW = 1159.9 ton blue water temp pink TEx = 73.92Tower Tton-Ex = -1091 SystkW = 1891.3 air cfm purplewater gpm orange Exsen-ton = -82.8 V Total Eout-ton = -1186 air temp green kW red

FIGURE 1-3: (SEE) Schematic at peak design hour


Figure 1-4 gives the (SEE) schematic for the condition of 50F DB & 45F WB. A careful review of the two schematics provides understanding of

why the system kW reduced about 750 kW.

BLD ft2 = 498600 %clear sky = 100.0% InfilLat-ton = 0.00Condenser # floors = 13 Tdry-bulb = 50.0 exfil-CFM = 6811 >>

(cond)ton= 303 Pipesize-in =6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 45.0 Infilsen-ton = -14.1TCR= 66.5 > gpmT= 900 > (ewt)T= 65.4 tfan-kW= 8 N/S wall ft2 = 40,560 WallNtrans ton= -4.17

TCR-app= 1.17 (H)T-total= 74.7 (H)T-static = 9.9 Tfan-kW= 8 E/W wall ft2 = 27,008 WallStrans ton= -3.73(COND)ton= 303 PT-heat = -0.74 Trange= 8.08 tfan-%= 100% Wall % glass= 37.5% WallEtrans ton= -1.96

(H)cond= 51.3 < pT-kW= 15.2 < (lwt)T = 57.3 tton-ex= -305 Glass U = 0.55 WallWtranston= -2.78 WallTot trans ton = -12.6(cond)ft/sec= 10.8 EfTpump= 0.83 Tapproach = 12.3 T#= 1 Wall U = 0.09 GlassN trans ton = -16.03

Ptower # = 1 T-Ton-ex= -305 Glass SHGC = 0.40 GlassS trans ton = -16.03Trg+app = 20.4 Wall emitt = 0.55 GlassE-trans ton = -10.68

Compressor ASHRAE Design RoofTrans ton = 25.4 GlassW-trans ton = -10.68 GlassTot-trans-ton= -53.4(chiller)kW= 84 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 7.1(chiller)lift= 23.2 Large Office Peopleton = 60 kW GlassS-solar-ton = 22.3(chiller)%= 30% Peak day Design 4PM plugton = 93 328 GlassE-solar ton = 4.7(chiller)#= 1 Weather %clear sky = 100% Lightton= 115 404 GlassW-solar ton = 33.1 GlassTot-solar-ton = 67.2

(CHILLER)kW= 84 conditions Tdry bulb = 50.0 (int-cfm)to-per-ret= 172581 BLD kW= 731 (int cfm)per-ton = 31.06 >(chiller)kW/ton= 0.304 Twet bulb = 45.0 Tot Bldint-ton = 292.9 AHU kW= 286 Tot Bldper-sen-ton = 18.1 vPlant kW = 126.1 Tstat-int= 75.0 SITE kW = 1017.9 Tstat-per = 73.0 return

(Bld)int.air-ton= -292.9 ^ Design 4PM ^ (Bld)per.air-ton= -18.1 airTair supply int= 56.14 ASHRAE Design Tair supply per= 63.91








(H)pri-fitings= 7.0 gpmbp= -269 (H)sec= 70.0 PLANTton = 272 (coil)des-ft/sec= 1.20 (one coil)ton= 10.47(Ef)c-pump= 0.81 (H)pri-bp= 0.50 (H)sec-pipe= 7 LMTD= 8.05 (H)coil= 0.2 VPc-heat-ton= -0.47 v (H)sec-bp= 0.00 Pipesize-in = 8.0 (COIL)L+s-ton= 272 ^ ^ ^ (H)coil-des= 2.1


Chicago 4PM All ElectricFuel Heat (FAN)ton-VAV= 35.4 (FAN)ret-kW= 37 FanPerformance 4PM Design kW THERM (FAN)kW-VAV= 124 (FAN)ret-ton= 10.6 V

chillerkW/evapton= 0.304 BLD.kW= 731.4 ^ (Air)ret-ton = 337.1plantkW/site ton= 0.463 (Fan)kW = 286.5 26 F.A.Inlet ^ Tar-to-VAV = 73.58

CCWSkW/bld ton= 1.33 Ductheat= 0.0 0.00 statFA= 42 26 VAV FANS VAVret-ton = 255.7WeatherEin-ton = 64.1 (FA)heat= 0.0 0 TFA to VAV = 50.0 > Tret+FA = 68.52 InfilVAV-Lat-ton = 0.00(Site)kW-Ein-ton = 289.5 Heat total = 0.0 0.00 Tdry bulb = 50.0 >(FA)sen-ton = > -18.8 (dh) = 3.303 < VAVret-CFM = 152,900 <PlantkW-Ein-ton = 35.9 PlantkW= 126.1 Fresh air > >>> > (FA)CFM= 41,817 > Efan-VSD= 0.608 InfilCFM-ton = 11.4 V

Total Ein-ton = 389 SystkW = 1144.0 1144.0 Twet bulb = 45.0 > (FA)Lat-ton= 0.0Pumptot-heat-ton = -2.8 (FA)kW= 0.0 ExLat-ton = 0.0

AHU ExLat-ton = 0.0 BLD.kW= 731.4 SEE SCHEMATIC ExCFM = -48,628

AHU Exsen-ton = -81.3 CCWSkW = 412.5 ton blue water temp pink TEx = 73.58Tower Tton-Ex = -305 SystkW = 1144.0 air cfm purplewater gpm orange Exsen-ton = -81.3 V Total Eout-ton = -389 air temp green kW red

FIGURE 1-4: (SEE) Schematic at 50F DB-45F WB


414500

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(AHU)Fan kW (plant)kW (Bld)kW (System)kW Duct heat kW FA Heat kW

FIGURE 1-5: System kW at peak dayFigure 1-5 gives the components that make up the system kW at peak day conditions and Figure 1-6 for the 50F/45F conditions.

731 731

263 286

115 126

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FIGURE 1-6: System kW at 50F DB-45F WB

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(Bld) kW Bld sen.ton (Bld)Infil lat ton

FIGURE 1-7: Building loads-peak dayFigure 1-7 gives the building loads at peak design day and Figure 1-8 at 50F/45F conditions. The building kW demand is the same for both figures but the load (ton) is significantly less at 50F/45F as expected.

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FIGURE 1-8: Building loads-50F DB 45F WB


44.71 44.44 44.31 44.06 44.36 44.76 44.49 44.56 44.06 44.65 44.52 44.52

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Coil entering water (F) Evaporator leaving water (F) Bypass water(F)

Coil leaving water (F) Evap. Entering water (F)

FIGURE 1-9: P/S pumping Temperatures (F)Figure 1-9 gives the water temperatures at peak day conditions and Figure 1-10 for the 50F/45F conditions. The supply water into the coils is about 44.5F for both figures and the coil leaving water is about 64.5F. The water into the evaporator varies because of bypass water; however an economizer would be placed before the bypass pipe.

44.94 44.90 44.90 44.43 44.46 44.68 44.64 44.34 44.52 44.52 44.58 44.65

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FIGURE 1-10: P/S pumping Temperatures (F)

84.382.3

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(ewt)tower (F) (lwt)tower (F) Tower approach (F)

FIGURE 1-11: Tower performanceFigure 1-11 provides the tower performance for peak day and Figure 1-12 for 50F/45F conditions. Figure 1-12 illustrates that the tower leaving water temperature (lwt) of about 52F to 57F offers an opportunity to cool the 64.5F water leaving the coils.

55.3 55.2 55.2 54.855.9

63.4 63.4 64.3 65.4

57.656.0

57.7

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56.2 56.2 56.7 57.3

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p. (F

)

Wet bulb (F)TOWER PERFORMANCE 50F DB-45F WB


FIGURE 1-12: Tower performance


52.0 52.0 52.0 51.7 52.3

56.2 56.2 56.7 57.3

53.2 52.453.3

64.9 64.9 64.9 64.4 64.5 64.7 64.6 64.3 64.5 64.5 64.6 64.7

40

45

50

55

60

65

70

40

45

50

55

60

65

70

Dry bulb (F)

Tow

er w

ater

tem

p. (F

)

Tow

er w

ater

tem

p. (F

)

Wet bulb (F)TOWER & COIL PERFORMANCE 50F DB-45F WB

(lwt)tower (F) (lwt)coil (F)

FIGURE 1-13: Temperatures of Coil & Tower water (F)Figure 1-13 gives the coil leaving water temperature verses the tower leaving water; clearly if we consider only these temperatures then opportunity exists for a water economizer.

1 1 1 1 1 1 1 1 1 1 1 1

39 39 39 39 42

73 73 78 84

47 42

47

77 77 77 77 80

115 115 120 126

8880

88

0

20

40

60

80

100

120

140

160

180

200

0

1

TOTAL EVAPORATOR TON

kW

# Nu

mbe

r Chi

llers

On

Total System Demand (kW)

CHILLER & PLANT PERFORMANCE-(50F DB & 45F WB)

# number chillers on Total Chiller-kW Plant (kW)

FIGURE 1-14: Chiller & Plant kWFigure 1-14 gives the chiller kW and we see that the maximum possible reduction in kW is from 39 to 84kW to eliminate the chiller operation at these 50F/45F conditions.

Figure 1-14 also gives the total system kW and we see that the maximum possible reduction is about 5% to 7% of the total system kW. However Figure 1-13 illustrates that the tower could only provide about a 50% reduction in evaporator load if supply water is 44F.Figure 1-15 illustrates that the chiller kW/ton is very good, about .30 to .36kW/ton.

0.36

4

0.36

6

0.36

6

0.39

5

0.35

6

0.29

8

0.29

9

0.30

4

0.30

4

0.32

3

0.35

1

0.31

9

0.73

4

0.73

8

0.73

8

0.79

5

0.69

9

0.47

8

0.47

9

0.47

4

0.46

3 0.60

6

0.69

0

0.60

0

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00


kW/T

ON

kW/t

on

PLANT TONCHILLER & PLANT kW/ton at 50F DB & 45F WB

Chiller kW/evaporator ton Plant kW/plant ton

FIGURE 1-15: Chiller & Plant kW/ton

Figure 1-16 gives the chiller lift and chiller kW for peak day and the 50F/45F conditions, a value that varies from about 12.4F to 23.2F for the 50F/45F conditions. A further drop in lift due to a water economizer could cause the chiller to surge and/or a significant increase in chiller kW/ton.


12.4 12.4 12.4 12.5 13.5

21.0 21.0 22.2 23.2

15.3 13.5 15.2

41.8 40.0 38.243.1

49.9

56.2 58.0 59.862.0

53.556.1

47.4

39 39 39 39 4273 73 78 84

47 42 47106 99 95 112

324

458486

519558

380

226

140

0

100

200

300

400

500

600

700

800

0

10

20

30

40

50

60

70

Time of Day

kW

Chill

er Li

ft (F

)

Time of Day

Chiller performance at peak day & 50F DB-45F WB

Chiller Lift (50F DB-45F WB) Chiller Lift (Peak day)Total Chiller-kW(50F DB-45F WB) Total Chiller (kW)(Peak day)

FIGURE 1-16: Chiller Performance

CONCLUSIONConsidering that a water economizer only offers a maximum opportunity of 5% to 7% if all chiller kW is eliminated by an economizer and for this case only about 2.5% to 3.5% as illustrated by Figure 1-13; the author arrives at the conclusion; the cost, complexity, and control of a water economizer for the Chicago large office as defined by the Pacific Northwest National Laboratory (PNNL) study of 90.1-2010 is not a good idea. However other control concepts are suggested by Taylor and Nall that will change the system response. Increasing supply air temperature, increasing supply water temperature, effects of solar load and also a decrease in outside temperature below 50F/45F will change the system response.Chapter 2 will address increasing supply air temperature.Kirby Nelson P.E.Life Member ASHRAE


CHAPTER 2: Performance at 50F DB-45F WB & supply air temperature of 55F & 60F

45 45 45 45 45 45 45 45 45 45 45 45

50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0

3035404550556065707580859095100

3035404550556065707580859095

100

% Clear Sky

AIR

TEM

Pera

ture

(F)

Air T

empe

ratu

re (F

)

TIME OF DAY

WEATHER

(Temp)wet bulb (Temp)dry bulb (Temp) dry bulb F (Temp) wet bulb F

FIGURE 2-1: Weather conditions

732 754 754658

788

1,110 1,109 1,125 1,144

705

549

858656 678 678598

811

1,244 1,243 1,274 1,315

740

567

786

0

200

400

600

800

1000

1200

1400

1600

0

200

400

600

800

1000

1200

1400

1600

% Clear Sky

Syst

em (k

W)

Syst

em (k

W)

TIME of DAY

SYSTEM TOTAL (kW)

(50F DB-45F WB)55F supply air (kW) (50F DB-45F WB) 60F supply air (kW)

FIGURE 2-2: Total system kW

Figure 2-1 illustrates the weather profiles are the same to be evaluated in this chapter 2.

Figure 2-2 illustrates that the system kW increased with 60F supply air during the day and decreased during night time operation.


Figure 2-3 gives the (SEE) schematic at 4PM with 55F supply air. The system kW is also shown on Figure 2-2 above.


(cond)ton= 303 Pipesize-in =6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 45.0 Infilsen-ton = -14.1TCR= 66.5 > gpmT= 900 > (ewt)T= 65.4 tfan-kW= 8 N/S wall ft2 = 40,560 WallNtrans ton= -4.17

TCR-app= 1.17 (H)T-total= 74.7 (H)T-static = 9.9 Tfan-kW= 8 E/W wall ft2 = 27,008 WallStrans ton= -3.73(COND)ton= 303 PT-heat = -0.74 Trange= 8.08 tfan-%= 100% Wall % glass= 37.5% WallEtrans ton= -1.96



Compressor ASHRAE Design RoofTrans ton = 25.4 GlassW-trans ton = -10.68 GlassTot-trans-ton= -53.4(chiller)kW= 84 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 7.1(chiller)lift= 23.2 Large Office Peopleton = 60 kW GlassS-solar-ton = 22.3(chiller)%= 30% 50F/45F 55F supply 4PM plugton = 93 328 GlassE-solar ton = 4.7(chiller)#= 1 Weather %clear sky = 100% Lightton= 115 404 GlassW-solar ton = 33.1 GlassTot-solar-ton = 67.2

(CHILLER)kW= 84 conditions Tdry bulb = 50.0 (int-cfm)to-per-ret= 172581 BLD kW= 731 (int cfm)per-ton = 31.06 >(chiller)kW/ton= 0.304 Twet bulb = 45.0 Tot Bldint-ton = 292.9 AHU kW= 286 Tot Bldper-sen-ton = 18.1 vPlant kW = 126.1 Tstat-int= 75.0 SITE kW = 1017.9 Tstat-per = 73.0 return

(Bld)int.air-ton= -292.9 ^ 55F supply 4PM ^ (Bld)per.air-ton= -18.1 airTair supply int= 56.14 ASHRAE Design Tair supply per= 63.91










Chicago 4PM All ElectricFuel Heat (FAN)ton-VAV= 35.4 (FAN)ret-kW= 37 FanPerformance 4PM 55F supply kW THERM (FAN)kW-VAV= 124 (FAN)ret-ton= 10.6 V


CCWSkW/bld ton= 1.33 Ductheat= 0.0 0.00 statFA= 42 26 VAV FANS VAVret-ton = 255.7WeatherEin-ton = 64.1 (FA)heat= 0.0 0 TFA to VAV = 50.0 > Tret+FA = 68.52 InfilVAV-Lat-ton = 0.00(Site)kW-Ein-ton = 289.5 Heat total = 0.0 0.00 Tdry bulb = 50.0 >(FA)sen-ton = > -18.8 (dh) = 3.303 < VAVret-CFM = 152,900 <PlantkW-Ein-ton = 35.9 PlantkW= 126.1 Fresh air > >>> > (FA)CFM= 41,817 > Efan-VSD= 0.608 InfilCFM-ton = 11.4 V


AHU ExLat-ton = 0.0 BLD.kW= 731.4 SEE SCHEMATIC ExCFM = -48,628

AHU Exsen-ton = -81.3 CCWSkW = 412.5 ton blue water temp pink TEx = 73.58Tower Tton-Ex = -305 SystkW = 1144.0 air cfm purplewater gpm orange Exsen-ton = -81.3 V Total Eout-ton = -389 air temp green kW red

FIGURE 2-3: 4PM (SEE) Schematic at 50F DB 45F WB with 55F supply air


Figure 2-4 gives the (SEE) schematic for the condition of 50F DB & 45F WB & 60F supply air. A careful review of the two schematics provides understanding of why the system kW

increased about 170 kW with 60F supply air. The following discussion and charts will help understand why.

BLD ft2 = 498600 %clear sky = 100.0% InfilLat-ton = 0.00Condenser # floors = 13 Tdry-bulb = 50.0 Infil-CFM = 6811 <

(cond)ton= 351 Pipesize-in =6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 45.0 Infilsen-ton = -14.1TCR= 69.2 > gpmT= 900 > (ewt)T= 68 tfan-kW= 8.3 N/S wall ft2 = 40,560 WallNtrans ton= -4.17

TCR-app= 1.19 (H)T-total= 74.7 (H)T-static = 9.9 Tfan-kW= 8.3 E/W wall ft2 = 27,008 WallStrans ton= -3.73(COND)ton= 351 PT-heat = -0.74 Trange= 9.3 tfan-%= 100% Wall % glass= 37.5% WallEtrans ton= -1.96



Compressor ASHRAE Design RoofTrans ton = 25.4 GlassW-trans ton = -10.68 GlassTot-trans-ton= -53.4(chiller)kW= 101 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 7.1(chiller)lift= 26.2 Large Office Peopleton = 60 kW GlassS-solar-ton = 22.3(chiller)%= 36% 50F/45F 60F supply 4PM plugton = 93 328 GlassE-solar ton = 4.7(chiller)#= 1 Weather %clear sky = 1.00 Lightton= 115 404 GlassW-solar ton = 33.1 GlassTot-solar-ton = 67.2

(CHILLER)kW= 101 conditions Tdry bulb = 50.0 (int-cfm)to-per-ret= 230108 BLD kW= 731.4 (int cfm)per-ton = 41.42 >(chiller)kW/ton= 0.316 Twet bulb = 45.0 Total Bldint-ton = 292.9 AHU kW= 440.2 Tot Bldper-sen-ton = 28.5 vPlant kW = 143.1 Tstat-int= 75.0 SITE kW = 1171.7 Tstat-per = 73.0 return

(Bld)int.air-ton= -292.9 ^ 60F supply 4PM ^ (Bld)per.air-ton= -28.5 airTair supply int= 60.86 ASHRAE Design Tair supply per= 64.99








(H)pri-fitings= 7.0 gpmbp= -218 (H)sec= 70 PLANTton = 315 (coil)des-ft/sec= 1.20 (one coil)ton= 12.11(Ef)c-pump= 0.81 (H)pri-bp= 0.33 (H)sec-pipe= 9 LMTD= 11.92 (H)coil= 0.2 VPc-heat-ton= -0.47 v (H)sec-bp= 0.00 Pipesize-in = 8.0 (COIL)L+s-ton= 315 ^ ^ ^ (H)coil-des= 2.1


Chicago 4PM All ElectricFuel Heat (FAN)ton-VAV= 69.0 (FAN)ret-kW= 73 FanPerformance 4PM 60F supply kW THERM (FAN)kW-VAV= 243 (FAN)ret-ton= 20.7 V

chillerkW/evapton= 0.316 BLD.kW= 731.4 ^ (Air)ret-ton = 344.1(plant)kW/site ton= 0.454 (Fan)kW = 440.2 26 F.A.Inlet ^ Tar-to-VAV = 73.83CCWSkW/bld ton= 1.82 Ductheat= 0.0 0.00 statFA= 42 26 VAV FANS VAVret-ton = 283.6WeatherEin-ton = 42.2 (FA)heat= 0.0 0 TFA to VAV = 50.0 > Tret+FA = 70.14 InfilVAV-Lat-ton = 0.00(Site)kW-Ein-ton = 333.2 Heat total = 0.0 0.00 Tdry bulb = 50.0 >(FA)sen-ton = > -37.6 (dh) = 4.961 < VAVret-CFM = 227,791 <PlantkW-Ein-ton = 40.7 PlantkW= 143.1 Fresh air > >>> > (FA)CFM= 41,817 > Efan-VSD= 0.648 InfilCFM-ton = 8.5 V


AHU ExLat-ton = 0.0 BLD.kW= 731.4 SEE SCHEMATIC ExCFM = -48,628AHU Exsen-ton = -60.5 CCWSkW = 583.4 ton blue water temp pink TEx = 73.83Tower Tton-Ex = -353 SystkW = 1314.8 air cfm purplewater gpm orange Exsen-ton = -60.5 V Total Eout-ton = -416 air temp green kW red

FIGURE 2-4: 4PM (SEE) Schematic at 50F DB-45F WB-(60F supply air)


386 440

126 143

731 731656 678 678

598

811

1,244 1,243 1,274 1,315

740

567

786

0.00 0.00 0

200

400

600

800

1000

1200

1400

1600

0

200

400

600

800

1000

1200

1400

1600

DRY BULB (F)

(kW

)

kW

TIME OF DAYSYSTEM kW-60F supply air

(AHU)Fan kW (plant)kW (Bld)kW (System)kW Duct heat kW FA Heat kW

FIGURE 2-5: System kW with 60F supply airFigure 2-5 gives the components that make up the system kW with 60F supply air and Figure 2-6 for 55F supply air.The charts illustrate that during the day the air handler kW increase with 60F supply air drives the system kW increase. At night the perimeter reheat is reduced with 60F supply air resulting in a decrease in system kW.

731 731

263 286

115 126

732 754 754658

788

1,110 1,109 1,1251,144

705549

858

0 0 0

200

400

600

800

1000

1200

1400

1600

0

200

400

600

800

1000

1200

1400

1600

Dry bulb (F)

(kW

)

TIME OF DAY

SYSTEM kW-55F supply air

(Bld)kW (AHU)Fan kW (plant)kW (System)kW Duct heat kW FA Heat kW

FIGURE 2-6: System kW with 55F supply air

731

110

305 321

050100150200250300350400450500550600

0

100

200

300

400

500

600

700

800

DRY BULB (F)

BUIL

DIN

G (t

on)

BUIL

DIN

G (k

W)

TIME OF DAYBUILDING (KW) & (TON) (50F DB-45F WB)(60F supply air)

(Bld) kW Bld sen.ton (Bld)Infil lat ton

FIGURE 2-7: Building loads-60F supplyFigure 2-7 gives the building loads with 60F supply air and Figure 2-8 with 55F supply air. The building kW demand and load (ton) is the same for both figures.

168

731

295 311

050100150200250300350400450500550600

0

100

200

300

400

500

600

700

800

DRY BULB (F)

BUIL

DIN

G (t

on)

BUIL

DIN

G (k

W)

TIME OF DAYBUILDING (KW) & (TON)(50F DB-45F WB)(55F supply air)

(Bld)kW Bld.sen.ton (Bld) Infil Lat ton

FIGURE 2-8: Building loads-55F supply


286

440272

314.9

0

50

100

150

200

250

300

350

400

0

100

200

300

400

500

600

700

800

Dry bulb (F)

TON

(kW

)

TIME OF DAY

(AHU) kW & Plant Load (Ton) (55F & 60F supply air)

(AHU)Total kW (55F supply air) (AHU)Total kW(60F supply air)

Plant load Ton (55F supply air) Plant load Ton (60F supply air)

FIGURE 2-9: (AHU) kW & plant (ton) for 55F & 60F supply air

37

286

0

125

124

0

50

100

150

200

250

300

350

400

450

500

550

0

50

100

150

200

250

300

350

400

450

500

550

(AHU) Total kW

(kW

)

(kW

)

TIME OF DAY

(AHU) total kW-55F supply air

Return fanl kW (AHU)Total kW Duct reheat (kW) Terminal fans (kW)

Duct heat (kW) VAV Fans (kW) Fresh Air (kW)

FIGURE 2-10: (AHU) total kW 55F supply air

Figure 2-9 illustrates that 60F supply air gives a reduction in load and total (AHU) kW during night operation and an increase during the day when solar load is occurring. Figures 2-10 & 2-11 further illustrate. Raising supply air to 60F reduces duct reheat kW more than the increase in VAV fans kW during night hours when perimeter heat is required. Perimeter heat is not required during the day, due to solar, stat set points and return air path, and therefore the increase in VAV fans kW drives total kW to a greater value than for 55F supply air.

73

440

0

125

243

0

50

100

150

200

250

300

350

400

450

500

550

0

50

100

150

200

250

300

350

400

450

500

550

(AHU) Total kW

(kW

)

(kW

)

TIME OF DAY(AHU) total kW-60F supply air

Return fanl kW (AHU)Total kW Duct reheat (kW) Terminal fans (kW)

Duct heat (kW) VAV Fans (kW) Fresh Air (kW)

FIGURE 2-11: (AHU) total kW 60F supply airIn later Chapters we will investigate the effect of low solar load and also the effect of stat set points and return air path.


44.43 44.40 44.40 44.28 44.33 44.72 44.67 44.51 44.22 44.21 44.35 44.18

64.4

3

64.4

0

64.4

0

64.2

8

64.3

3

64.7

2

64.6

7

64.5

1

64.2

2

64.2

1

64.3

5

64.1

8

47.8

9

47.8

3

47.8

3

47.5

8

49.2

8

55.8

2

55.7

4

56.3

1

56.9

6

50.4

6

49.3

1

49.3

4

40

45

50

55

60

65

70

40

45

50

55

60

65

70


Wat

er Te

mp.

(F)

Wat

er Te

mp.

(F)

Plant (ton)= 26-(Coil)Lat+sen-ton(60F supply air) PRIMARY/SECONDARY PUMPING-Water temperatures (F)



FIGURE 2-12: P/S pumping Temperatures (F)Figure 2-12 & 2-13 gives the water temperatures for 55F & 60F supply air. The supply water into the coils is about 44.5F for both figures and the coil leaving water is about 64.5F. The water into the evaporator is about the same for both supply air conditions & varies because of bypass water; however an economizer would be placed before the bypass pipe.

44.94 44.90 44.90 44.43 44.46 44.68 44.64 44.34 44.52 44.52 44.58 44.65

64.9

4

64.9

0

64.9

0

64.4

3

64.4

6

64.6

8

64.6

4

64.3

4

64.5

2

64.5

2

64.5

8

64.6

5

49.2

4

49.1

8

49.1

8

48.3

8

49.1

7

54.4

1

54.3

5

54.6

3

55.5

4

50.4

1

49.3

5

50.5

9

40

45

50

55

60

65

70

40

45

50

55

60

65

70


Wat

er Te

mp.

(F)

Wat

er Te

mp.

(F)

Plant (ton)= 26-(Coil)Lat+sen-ton(55F supply air) P/S PUMPING-Water temperatures (F)



FIGURE 2-13: P/S pumping Temp. (F) with 55F supply air

54.1 54.0 54.0 53.8

56.2

65.5 65.466.6 68.0

58.256.2

56.6

51.4 51.3 51.3 51.252.5

57.3 57.3 57.9 58.7

53.552.5 52.7

6.37 6.34 6.34 6.247.50

12.35 12.3312.92

13.68

8.517.51 7.67

0

5

10

15

50

60

70

80


Tow

er a

ppro

ach

(F)

Tow

er w

ater

tem

p. (F

)

Wet bulb (F)TOWER PERFORMANCE 60F supply air


FIGURE 2-14: Tower performanceFigure 2-14 & 2-15 provides the tower performance for 60F & 55F supply air. The tower leaving water is about the same for both supply air conditions; increasing supply air temperature has little effect on tower performance.

55.3 55.2 55.2 54.855.9

63.4 63.4 64.3 65.4

57.656.0

57.7

52.0 52.0 52.0 51.7 52.3

56.2 56.2 56.7 57.3

53.2 52.453.3

7.0 7.0 7.0 6.77.3

11.2 11.2 11.712.3

8.27.4

8.3

0

5

10

15

50

60

70

80


Tow

er a

ppro

ach

(F)

Tow

er w

ater

tem

p. (F

)

Wet bulb (F)TOWER PERFORMANCE 55F supply air


FIGURE 2-15: Tower performance


51.99 51.97 51.97 51.74 52.31

56.25 56.24 56.71 57.29

53.22 52.3653.27

64.94 64.90 64.90 64.43 64.46 64.68 64.64 64.34 64.52 64.52 64.58 64.65

40

45

50

55

60

65

70

40

45

50

55

60

65

70

Coil (lwt)F for 60F supply air

Tow

er w

ater

tem

p. (F

)

Tow

er w

ater

tem

p. (F

)

Tower (lwt)F-60F supply airTOWER & COIL PERFORMANCE 55F & 60F supply air

(lwt)tower (F)-55F supply air (lwt)coil (F)-55F supply air

FIGURE 2-16: Temperatures of Coil & Tower water (F)Figure 2-16 gives the coil leaving water temperature verses the tower leaving water for both 55F & 60F supply air; clearly if we consider only these temperatures then opportunity exists for a water economizer.

1 1 1 1 1 1 1 1 1 1 1 1

39 39 39 39 42

73 73 78 84

47 42

47

77 77 77 77 80

115 115 120 126

8880

88

0

20

40

60

80

100

120

140

160

180

200

0

1


kW

# Nu

mbe

r Chi

llers

On

Total System Demand (kW)

CHILLER & PLANT PERFORMANCE-(55F supply air))


FIGURE 2-17: Chiller & Plant kW-55F supply airFigures 2-17 & 2-18 give the chiller kW and we see that the maximum possible reduction in kW is from 39 to 84kW for the 55F supply air operation

and 38 to 143 kW for the 60F supply air operation i.e. eliminate the chiller operation. Figure 2-17 &2-18 also gives the total system kW and we see that the maximum possible reduction is about 5% to 8% of the total system kW. However Figure 2-16 illustrates that the tower could only provide about a 50% reduction in evaporator load if supply water is 44F.

1 1 1 1 1 1 1 1 1 1 1 1

38 38 38 38 43

84 8491

101

5043

45

75 75 75 7482

126 126133

143

9182 84

0

20

40

60

80

100

120

140

160

180

200

0

0

0

0

0

1

1

1

1

1

1


kW

# N

umbe

r Chi

llers

On

Total System Demand kW

CHILLER & PLANT PERFORMANCE (60F supply air)


FIGURE 2-18: Chiller & plant kW-60F supply air

The following four tables illustrate that raising the supply air temperature from 55F to 60F has a slight negative 24 hour effect.The increase in system kW at 4PM is significant but the 24 hour effect is only about a 3% increase in kWh by increasing supply air to 60F.


Chicago 4PM All ElectricPerformance 4PM 55F supply kW

chillerkW/evapton= 0.304 BLD.kW= 731.4plantkW/site ton= 0.463 (Fan)kW = 286.5

CCWSkW/bld ton= 1.33 Ductheat= 0.0WeatherEin-ton = 64.1 (FA)heat= 0.0(Site)kW-Ein-ton = 289.5 Heat total = 0.0PlantkW-Ein-ton = 35.9 PlantkW= 126.1

Total Ein-ton = 389 SystkW = 1144.0Pumptot-heat-ton = -2.8

AHU ExLat-ton = 0.0 BLD.kW= 731.4AHU Exsen-ton = -81.3 CCWSkW = 412.5Tower Tton-Ex = -305 SystkW = 1144.0Total Eout-ton = -389

Table 2-1: 4PM-55F supply air

BLD sq-ft = 498,600ALL ELECTRIC 50F/45F

55F supply 24hr BLD.24hr-kW= 10,096

(Fan)24hr-kW = 3,921(Duct)24hr-heat kW= 4,313

(FA)24hr-heat kW= 0Heat24hr-total kW= 4,313

Plant24hr-kW= 2,240SYST 24hr-kW = 20,570

(CCWS)24hr-kW= 10,473BLD.24hr-kW= 10,096

Total24hr-kW = 20,570Weather24h-Ein-ton= -217SITE24h-kW-Ein-ton = 5213Plant24h-kW-Ein-ton = 637Total24h-Ein-ton = 5633Pump24hr-heat-ton = -63

AHU Ex24hr-Lat-ton = 0AHU Ex24hr-sen-ton = -1119

Tower24hr-ton-Ex = -4451Total E24hr-out-ton = -5633

Table 2-2: 24 hr-55F supply

Chicago 4PM All ElectricPerformance 4PM 60F supply kW

chillerkW/evapton= 0.316 BLD.kW= 731.4(plant)kW/site ton= 0.454 (Fan)kW = 440.2CCWSkW/bld ton= 1.82 Ductheat= 0.0WeatherEin-ton = 42.2 (FA)heat= 0.0(Site)kW-Ein-ton = 333.2 Heat total = 0.0PlantkW-Ein-ton = 40.7 PlantkW= 143.1

Total Ein-ton = 416 SystkW = 1314.8Pumptot-heat-ton = -2.7

AHU ExLat-ton = 0.0 BLD.kW= 731.4AHU Exsen-ton = -60.5 CCWSkW = 583.4Tower Tton-Ex = -353 SystkW = 1314.8Total Eout-ton = -416

Table2-3: 4PM-60F supply

BLD sq-ft = 498,600ALL ELECTRIC 50F/45F

60F supply 24hr BLD.24hr-kW= 10,096

(Fan)24hr-kW = 5,165(Duct)24hr-heat kW= 3,584

(FA)24hr-heat kW= 0Heat24hr-total kW= 3,584

Plant24hr-kW= 2,331SYST 24hr-kW = 21,176

(CCWS)24hr-kW= 11,079BLD.24hr-kW= 10,096

Total24hr-kW = 21,176Weather24h-Ein-ton= -519SITE24h-kW-Ein-ton = 5360Plant24h-kW-Ein-ton = 663Total24h-Ein-ton = 5504Pump24hr-heat-ton = -60

AHU Ex24hr-Lat-ton = 0AHU Ex24hr-sen-ton = -825

Tower24hr-ton-Ex = -4619Total E24hr-out-ton = -5504

Table 2-4: 24 hr-60F supply

Following are schematics at 4AM.


Figure 2-19 gives the system schematic at 4AM with 55F supply air. Note the required perimeter heat kW is 457.2 & the perimeter stat is set at 73F & interior at 75F. The terminal

fans are assumed as controlled off which may be a bad assumption, however not much would change if we turn the terminal fans on.


(cond)ton= 122 Pipesize-in = 6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 45.0 Infilsen-ton = -14.1TCR= 56.3 > gpmT= 900 > (ewt)T= 55.2 tfan-kW= 8.3 N/S wall ft2 = 40,560 WallNtrans ton= -4.37




Compressor ASHRAE Design RoofTrans ton = -4.6 GlassW-trans ton = -10.68 GlassTot-trans-ton= -53.4(chiller)kW= 39 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 0.0(chiller)lift= 12.4 Large Office Peopleton = 0 kW GlassS-solar-ton = 0.0(chiller)%= 14% 50F/45F 55F supply 4AM plugton = 41 146 GlassE-solar ton = 0.0(chiller)#= 1 Weather %clear sky = 100% Lightton= 6 22 GlassW-solar ton = 0.0 GlassTot-solar-ton = 0.0

(CHILLER)kW= 39 conditions Tdry bulb = 50.0 (int-cfm)to-per-ret= 19194 BLD kW= 168.0 (int cfm)per-ton = 12.09 >(chiller)kW/ton= 0.366 Twet bulb = 45.0 Total Bldint-ton = 43.2 AHU kW= 508.8 Tot Bldper-sen-ton = -70.0 vPlant kW = 77.0 Tstat-int= 80.0 SITE kW = 676.9 Tstat-per = 73.0 return

(Bld)int.air-ton= -43.2 ^ 55F supply 4AM ^ (Bld)per.air-ton= 70.0 airTair supply int= 55.00 ASHRAE Design Tair supply per= 94.00






(bEQ)day gpmevap= 600 Psec-heat-ton = -1.12 (D)int-CFM= 19,194 ^ (D)per-CFM= 37,035 ^(lwt)evap = 44.90 > Psec-kW= 5.6 > (ewt)coil= 44.9 >>>(Coil)sen-ton= 104 ^ (coil)gpm= 4.9 ^




Chicago 4AM All Electric Fuel Heat (FAN)ton-VAV= 11.3 (FAN)ret-kW= 12 FanPerformance 4AM 55F supply kW THERM (FAN)kW-VAV= 40 (FAN)ret-ton= 3.4 V


CCWSkW/bld ton= 5.18 Ductheat= 457.2 19.50 statFA= 42 26 VAV FANS VAVret-ton = 93.3WeatherEin-ton = -75.9 (FA)heat= 0.0 0.00 TFA to VAV = 50.0 > Tret+FA = 73.39 InfilVAV-Lat-ton = 0.00(Site)kW-Ein-ton = 192.5 Heat total = 457.2 19.50 Tdry bulb = 50.0 >(FA)sen-ton = > -0.2 (dh) = 2.600 < VAVret-CFM = 55,731 <PlantkW-Ein-ton = 21.9 PlantkW= 77.0 Fresh air > >>> > (FA)CFM= 499 > Efan-VSD= 0.432 InfilCFM-ton = 11.4 V



FIGURE 2-19: 4AM (SEE) Schematic at 50F DB 45F WB with 55F supply air


Figure 2-20 is for 60F supply air and perimeter heat kW reduces to 381.4 verses 457.2 of Figure 2-19 above. Raising the supply air temperature

typically increases fan kW and reduces perimeter heat kW; however other variables are involved as discussed in conclusions below.


(cond)ton= 100 Pipesize-in = 6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 45.0 Infilsen-ton = -14.1TCR= 55.1 > gpmT= 900 > (ewt)T= 54.0 tfan-kW= 8.3 N/S wall ft2 = 40,560 WallNtrans ton= -4.37




Compressor ASHRAE Design RoofTrans ton = -4.6 GlassW-trans ton = -10.68 GlassTot-trans-ton= -53.4(chiller)kW= 38 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 0.0(chiller)lift= 11.7 Large Office Peopleton = 0 kW GlassS-solar-ton = 0.0(chiller)%= 14% 50F/45F 60F supply 4AM plugton = 41 146 GlassE-solar ton = 0.0(chiller)#= 1 Weather %clear sky = 100% Lightton= 6 22 GlassW-solar ton = 0.0 GlassTot-solar-ton = 0.0

(CHILLER)kW= 38 conditions Tdry bulb = 50.0 (int-cfm)to-per-ret= 23993 BLD kW= 168.0 (int cfm)per-ton = 15.12 >(chiller)kW/ton= 0.440 Twet bulb = 45.0 Total Bldint-ton = 43.2 AHU kW= 434.9 Tot Bldper-sen-ton = -67.0 vPlant kW = 74.6 Tstat-int= 80.0 SITE kW = 602.9 Tstat-per = 73.0 return

(Bld)int.air-ton= -43.2 ^ 60F supply 4AM ^ (Bld)per.air-ton= 67.0 airTair supply int= 60.00 ASHRAE Design Tair supply per= 94.00






(bEQ)day gpmevap= 600 Psec-heat-ton = -0.90 (D)int-CFM= 23,993 ^ (D)per-CFM= 35,435 ^(lwt)evap = 44.40 > Psec-kW= 4.5 > (ewt)coil= 44.4 >>>(Coil)sen-ton= 83 ^ (coil)gpm= 4.0 ^




Chicago 4AM All Electric Fuel Heat (FAN)ton-VAV= 11.7 (FAN)ret-kW= 12 FanPerformance 4AM 60F supply kW THERM (FAN)kW-VAV= 41 (FAN)ret-ton= 3.5 V


CCWSkW/bld ton= 4.62 Ductheat= 381.4 16.27 statFA= 42 26 VAV FANS VAVret-ton = 72.1WeatherEin-ton = -79.2 (FA)heat= 0.0 0.00 TFA to VAV = 50.0 > Tret+FA = 73.39 InfilVAV-Lat-ton = 0.00(Site)kW-Ein-ton = 171.5 Heat total = 381.4 16.27 Tdry bulb = 50.0 >(FA)sen-ton = > -0.4 (dh) = 2.600 < VAVret-CFM = 58,930 <PlantkW-Ein-ton = 21.2 PlantkW= 74.6 Fresh air > >>> > (FA)CFM= 499 > Efan-VSD= 0.441 InfilCFM-ton = 8.3 V



FIGURE 2-20: 4AM (SEE) Schematic at 50F DB-45F WB-(60F supply air)


CONCLUSION FOR CONDITIONS DEFINEDConsidering that a water economizer only offers a maximum opportunity of 5% to 8% if all chiller kW is eliminated by an economizer and for this case only about 2.5% to 4% as illustrated by Figure 2-16; the author arrives at the conclusion; the cost, complexity, and control of a water economizer for the Chicago large office as defined by the Pacific Northwest National Laboratory (PNNL) study of 90.1-2010 is not a good idea; and raising air supply temperature to 60F from 55F is a bad ideal for the conditions studied here. Other changes that will make a difference for this building as defined include;(1) Solar load(2) Interior and perimeter stat set points.(3) Return air path(4) Outside temperatures below 50F DB & 45F WB.We plan to address these issues in coming chapters.

One final note; the above analysis is for the building system as designed according to “ASHRAE” concepts. These (http://kirbynelsonpe.com) studies include a (minimum kW design) that would likely result in different results and conclusions for the issues raised here. Kirby Nelson P.E.Life Member ASHRAE


http://kirbynelsonpe.com/

System Nomenclature Each of the more than 100 components of the system will be defined.The (PNNL) study defines the large office building as given by Figure N-1, a 13 story office with 498,600 square feet of air conditioned space.

FIGURE N-1: Building description The (PNNL) study can be viewed at;http://www.energycodes.gov/sites/default/files/documents/BECP_Energy_Cost_Savings_STD2010_May2011_v00.pdf orhttp://www.energycodes.gov/achieving-30-goal-energy-and-cost-savings-analysis-ashrae-standard-901-2010

BLD ft2 = %clear sky = InfilLat-ton =

# floors = Tdry-bulb = Infil-CFM = <Roof ft2 = Twet-bulb= Infilsen-ton =

N/S wall ft2 = WallNtrans ton=E/W wall ft2 = WallStrans ton=

Wall % glass= WallEtrans ton=Glass U = WallWtranston= WallTot trans ton =

Wall U = GlassN trans ton =Glass SHGC = GlassS trans ton =

Wall emitt = GlassE-trans ton =RoofTrans ton = GlassW-trans ton = GlassTot-trans-ton=Roofsky lite ton = GlassN-solar-ton =

Peopleton = kW GlassS-solar-ton =plugton = GlassE-solar ton =Lightton= GlassW-solar ton = GlassTot-solar-ton =

(int-cfm)to-per-ret= BLD kW= (int cfm)per-ton = >Total Bldint-ton = AHU kW= Tot Bldper-sen-ton = v

Tstat-int= SITE kW = Tstat-per = return(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= air

BUILDING NOMENCLATURE:Building structure;

BLD ft2 = air conditioned space# Floors = number of building floorsRoof ft2 = roof square feetN/S wall ft2 =north/south wall square feetE/W wall ft2 =east/west wall square feetWall % glass = percent of each wall that is glassGlass U = glass heat transfer coefficientWall U = wall heat transfer coefficientGlass SHGC = glass solar heat gain coefficientWall emit = wall solar indexBuilding interior space;Rooftrans-ton =transmission through roof (ton)Roofsky-lite-ton =sky lite load (ton)Peopleton = cooling load due to people (ton)Plugton = cooling load due to plug kWPlugtkW = kW demand due to plug loadsLightton = cooling load due to lights (ton)LightkW = kW demand due to lights(int-cfm)to-per-return = CFM of interior supply air that returns to perimeter of buildingTotal Bldint-ton = total building interior load (ton)Tstat-int = interior stat set temperature (F)Bldint-air-ton = supply air ton to offset interior loadBuilding perimeter space;%clear sky = percent solar that hits buildingTdry bulb = outside dry bulb temperature (F)Twet bulb = outside wet bulb temperature (F)Infillat-ton = latent load due to air infiltration (ton)InfilCFM = air infiltration CFMInfilsen-ton = sensible load due to air infiltration (ton)Walln trans ton = north wall transmission (ton)Walls trans ton = south wall transmission (ton)WallE trans ton = east wall transmission (ton)Wallw trans ton = west wall transmission (ton)Walltot-trans-ton = total wall transmission (ton)GlassN-trans-ton = north wall glass transmission (ton)GlassS-trans-ton = south wall glass transmission (ton)GlassE-trans-ton = east wall glass transmission (ton)GlassW trans-ton = west wall glass transmission (ton)Glasstot-trans-ton = total transmission thru glass (ton) GlassN-solar-ton = north glass solar load (ton)GlassS-solar-ton = south glass solar load (ton)GlassE-solar-ton = east glass solar load (ton)GlassW-solar-ton = west glass solar load (ton)Glasstot-solar-ton = total glass solar load (ton)(int cfm)per-ton = effect of interior CFM to wall (ton)





Total Bldper-sen-ton total perimeter sensible load (ton)Tstat-per = perimeter stat set temperature (F)Bldper-air-ton = supply air ton to offset perimeter load

Tair supply int= ASHRAE Design Tair supply per=

^ ABS Bld Ton = ^Ton kW Ton kW V

(fan)int-ter= (fan)per-ter=Theat-air= (D)heat =

Treheat air =(D)reheat =

(D)int-air-ton= Interior (D)per-air-ton= PeriTair coils = duct Tair coils= duct

(D)int-CFM= ^ (D)per-CFM= ^>>>(Coil)sen-ton= ^ (coil)gpm= ^

(coil)cap-ton= UAdesign=(coil)H2O-ft/sec= COIL UA=(coil)des-ft/sec= (one coil)ton=

LMTD= (H)coil= V(COIL)L+s-ton= ^ ^ ^ (H)coil-des=

<<<< Tair VAV= TBLD-AR =(FAN)VAV-CFM= (Air)ret-CFM = Return(FAN)ton-VAV= (FAN)ret-kW= Fan(FAN)kW-VAV= (FAN)ret-ton= V

^ (Air)ret-ton =26 F.A.Inlet ^ Tar-to-VAV =

statFA= 26 VAV FANS VAVret-ton = TFA to VAV = > Tret+FA = InfilVAV-Lat-ton =

>(FA)sen-ton = > (dh) = < VAVret-CFM = <> (FA)CFM= > Efan-VSD= InfilCFM-ton = V

> (FA)Lat-ton=(FA)kW= ExLat-ton =

ExCFM =temp pink TEx =gpm orange Exsen-ton = V

FIGURE 2A Air handler system AIR HANDLER DUCT SYSTEM NOMENCLATURE

(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= airTair supply int= ASHRAE Design Tair supply per=





(D)int-CFM= ^ (D)per-CFM= ^

Duct system nomenclatureTair supply int = temperature air supply to interior (F)(fan)int-ter-kW = kW demand of interior terminal fans(fan)int-ter-ton = load due to interior terminal fans kW (D)int-air-ton = cooling (ton) to interior ductTair coils = supply air temperature off coils to duct(D)int-CFM = supply air CFM to interior duct

(ABS Bld Ton) = absolute building load on (CCWS)Tair supply per = temperature air supply perimeter (F)(fan)per-ter-kW = kW demand perimeter terminal fans(fan)per-ter-ton = load due to perimeter terminal fansTheat-air = temp supply air before terminal fan heat(D)heat-kW = kW heat to perimeter supply air(D)heat-ton = (ton) heat to perimeter supply airTreheat air = temp(F) perimeter supply air after reheat (D)reheat-kW = kW reheat to perimeter supply air(D)reheat-ton = (ton) reheat to perimeter supply air(D)per-air-ton = cooling (ton) to perimeter duct Tair coils = supply air temperature off coils to duct(D)per-CFM = supply air CFM to perimeter ductCOIL NOMENCLATURE(coil)sen-ton = sensible load on all coils (ton)(coil)cap-ton = LMTD * UA = capacity (ton) one coil(coil)H2O-ft/sec = water velocity thru coil (ft/sec)(coil)design-ft/sec = coil design water velocity (ft/sec)LMTD = coil log mean temperature difference (F)(coil)L+s-ton = latent + sensible load on all coils (ton)(coil)gpm = water flow (gpm) thru one coilUAdesign = coil UA design valueUA = coil heat transfer coefficient * coil area. UA varies as a function water velocity (coil)gpm thru the coil, therefore as the (coil)gpm decreases the coil capacity decreases.




<<<< Tair VAV= TBLD-AR = Coils(one coil)ton = load (ton) on one coil(H)coil = air pressure drop thru coil (ft)(H)coil-design = design air pressure drop (ft)

(COIL)L+s-ton= ^ ^ ^ (H)coil-des=<<<< Tair VAV= TBLD-AR =

(FAN)VAV-CFM= (Air)ret-CFM = Return(FAN)ton-VAV= (FAN)ret-kW= Fan(FAN)kW-VAV= (FAN)ret-ton= V







VAV FAN SYSTEM NOMENCLATUREFresh air nomenclature:statFA = fresh air freeze stat set temperature (F)TFA to VAV = temperature of fresh air to VAV fan(FA)sen-ton = fresh air sensible load (ton)(FA)CFM = CFM fresh air to VAV fan inlet(FA)Lat-ton = fresh air latent load (ton)(FA)kW = heat kW to statFA set temperatureAir return nomenclature: TBLD-AR = return air temp (F) before return fan(Air)ret-CFM = CFM air return from building(FAN)ret-kW = return fans total kW(FAN)ret-ton = cooling load (ton) due to (FAN)ret-kW

(Air)ret-ton = return air (ton) before return fansTAR to VAV = TBLD-AR + delta T due to return fans kWVAVret-ton = return (ton) to VAV fans inletInfilVAV-Lat-ton = infiltration latent (ton) to VAV fansVAVret-CFM = return CFM to VAV fans inletInfilCFM-ton = load (ton) due to infiltration CFMExhaust air nomenclatureExLat-ton = latent load (ton) exhaustedExCFM = CFM of exhaust airTEx = temperature of exhaust air Exsen-ton = sensible load (ton) exhaustedVAV Fans nomenclatureTair-VAV = temp. air to coils after VAV fan heat(FAN)VAV-CFM = CFM air thru coils(FAN)ton-VAV = load (ton) due to VAV fan kW(FAN)kW-VAV = total VAV fan kW demandTret+FA = return and fresh air mix temperature (F)(dh) = VAV air static pressure (ft)Efan-VSD = VAV fans efficiency

AIR SIDE SYSTEM PLUS BUILDING BLD ft2 = %clear sky = InfilLat-ton =

# floors = Tdry-bulb = Infil-CFM = <Roof ft2 = Twet-bulb= Infilsen-ton =

N/S wall ft2 = WallNtrans ton=E/W wall ft2 = WallStrans ton=

Wall % glass= WallEtrans ton=Glass U = WallWtranston= WallTot trans ton =

Wall U = GlassN trans ton =Glass SHGC = GlassS trans ton =

Wall emitt = GlassE-trans ton =RoofTrans ton = GlassW-trans ton = GlassTot-trans-ton=Roofsky lite ton = GlassN-solar-ton =

Peopleton = kW GlassS-solar-ton =plugton = GlassE-solar ton =Lightton= GlassW-solar ton = GlassTot-solar-ton =

(int-cfm)to-per-ret= BLD kW= (int cfm)per-ton = >Total Bldint-ton = AHU kW= Tot Bldper-sen-ton = v

Tstat-int= SITE kW = Tstat-per = return(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= air

Tair supply int= ASHRAE Design Tair supply per=








<<<< Tair VAV= TBLD-AR =(FAN)VAV-CFM= (Air)ret-CFM = Return(FAN)ton-VAV= (FAN)ret-kW= Fan(FAN)kW-VAV= (FAN)ret-ton= V







Condenser(cond)ton= Pipesize-in = (H)T-pipe= Tower

TCR= > gpmT= > (ewt)T= tfan-kW=TCR-app= (H)T-total= (H)T-static = Tfan-kW=

(COND)ton= PT-heat = Trange= tfan-%=(H)cond= < pT-kW= < (lwt)T = tton-ex=

(cond)ft/sec= EfTpump= Tapproach = T#=Ptower # = T-Ton-ex=

Trg+app =Compressor ASHRAE Design

(chiller)kW= Chicago 90.1-2010(chiller)lift= Large Office(chiller)%= Peak day Design 4PM(chiller)#= Weather %clear sky =

(CHILLER)kW= conditions Tdry bulb =(chiller)kW/ton= Twet bulb =Plant kW =

> Evaporator(evap)ton=

TER=TER-app=

^ EVAPton=(H)evap=

(evap)ft/sec=(evap)des-ft/sec=

^ Vgpmevap= Psec-heat-ton =

(lwt)evap = > Psec-kW= > (ewt)coil=(H)pri-total= v Efdes-sec-p =

^ (H)pri-pipe= Tbp= Efsec-pump =(H)pri-fitings= gpmbp= (H)sec= PLANTton =(Ef)c-pump= (H)pri-bp= (H)sec-pipe=Pc-heat-ton= v (H)sec-bp= Pipesize-in =

^ < pc-kW= (ewt)evap = < (gpm)sec= < (lwt)coil=Pchiller-# =

CENTRAL PLANT Nomenclature will be defined by addressing each component of the plant.Primary/secondary pumping nomenclaturegpmevap = total gpm flow thru evaporators(H)pri-total = total primary pump head (ft) = (H)pri-pipe + (H)pri-fittings + (H)pri-bp + (H)evap

(H)pri-pipe = primary pump head due to piping (ft)(H)pri-fittings = primary head due to pump & fitting (ft)(Ef)c-pump = efficiency of chiller pumpPc-heat-ton = chiller pump heat to atmosphere (ton)Pc-kW = one chiller pump kW demand (kW)Pchiller-# = number chiller pumps operating(lwt)evap = temperature water leaving evaporator (F)Tbp = temperature of water in bypass (F)gpmbp = gpm water flow in bypass(H)pri-bp = head if chiller pump flow in bypass (ft)(ewt)evap = temp water entering evaporator (F)

Psec-heat-ton = secondary pump energy not into system (ton), goes to atmospherePsec-kW = kW demand of secondary pumpsEfdes-sec-p = design efficiency of secondary pumpingEfsec-pump = efficiency of secondary pumping(H)sec = secondary pump head (ft) = (H)sec-pipe + (H)sec-

bp + (H)coil + (H)valve

(H)sec-pipe = secondary pump head due to pipe (ft)(H)sec-bp = head in bypass if gpmsec > gpmevap

gpmsec = water gpm flow in secondary loop(ewt)coil = water temperature entering coil (F)Plantton = load (ton) from air side to plantPipesize-in = secondary pipe size (inches)(lwt)coil = temperature of water leaving coil (F)Condenser nomenclature:(cond)ton = load (ton) on one condenserTCR = temperature of condenser refrigerant (F)TCR-app = refrigerant approach temperature (F)(COND)ton = total load (ton) on all condensers(H)cond = tower pump head thru condenser (ft)(cond)ft/sec = tower water flow thru condenser Compressor:(chiller)kW = each chiller kW demand(chiller)lift = (TCR – TER) = chiller lift (F)(chiller)% = percent chiller motor is loaded(chiller)# = number chillers operating(CHILLER)kW = total plant chiller kW(chiller)kW/ton = chiller kW per evaporator tonEvaporator(evap)ton = load (ton) on one evaporatorTER = evaporator refrigerant temp (F)TER-app = evaporator refrigerant approach (F)EVAPton = total evaporator loads (ton)(H)evap = pump head thru evaporator (ft)(evap)ft/sec = velocity water flow thru evaporator(evap)des-ft/sec = evaporator design flow velocityTower piping nomenclaturePipesize-in = tower pipe size (inches)gpmT = each tower water flow (gpm)(H)T-total = total tower pump head (ft)PT-heat = pump heat to atmosphere (ton)PT-kW = each tower pump kW demandEfT-pump = tower pump efficiencyPtower # = number of tower pumps(H)T-pipe = total tower pump head (ft)



Tower piping nomenclature cont.(ewt)T = tower entering water temperature (F)(H)T-static = tower height static head (ft)Trange = tower range (F)= (ewt)T – (lwt)T

(lwt)T = tower leaving water temperature (F)Tapproach = (lwt)T – (Twet-bulb)Tower nomenclature

tfan-kW = kW demand of one tower fanTfan-kW = tower fan kW of fans on

tfan-% = percent tower fan speedtton-ex = ton exhaust by one tower

T# = number of towers onTton-ex = ton exhaust by all towers onTrg+app = tower range + approach (F)SYSTEM PERFORMANCE The performance indices of the following Tables are self-explanatory. A complete schematic will be shown below.

Chicago 4PM All ElectricFuel HeatPerformance 4PM Design kW THERM

chillerkW/evapton= BLD.kW=(plant)kW/site ton= (Fan)kW =CCWSkW/bld ton= Ductheat=WeatherEin-ton = (FA)heat=(Site)kW-Ein-ton = Heat total =PlantkW-Ein-ton = PlantkW=

Total Ein-ton = SystkW =Pumptot-heat-ton =

AHU ExLat-ton = BLD.kW=AHU Exsen-ton = CCWSkW =Tower Tton-Ex = SystkW =Total Eout-ton =

Performance table at given hour

BLD sq-ft =ALL ELECTRIC Peak day

Design 24hr BLD.24hr-kW=

(Fan)24hr-kW =(Duct)24hr-heat kW=

(FA)24hr-heat kW=Heat24hr-total kW=

Plant24hr-kW=SYST 24hr-kW =

(CCWS)24hr-kW=BLD.24hr-kW=

Total24hr-kW =

24 Hour performance, all-electric

ASHRAE DesignBLD sq ft =

Fuel heat Peak dayDesign 24hr ThermBLD.24hr-kW=

(Fan)24hr-kW =(Duct)24hr-heat therm=

(FA)24hr-heat therm=Heat24hr-total therm=

Plant24hr-kW=SYST 24hr-kW =

24 Hour performance, heat with fuel

Weather24h-Ein-ton= SITE24h-kW-Ein-ton = Plant24h-kW-Ein-ton =Total24h-Ein-ton =Pump24hr-heat-ton =

AHU Ex24hr-Lat-ton =AHU Ex24hr-sen-ton =

Tower24hr-ton-Ex =Total E24hr-out-ton =

ASHRAE Design

24 Hour Energy in = Energy out

ASHRAE Design kbtu/sqft-day

ALL ELECTRIC SYSTEM W/sqft (bEQ)dayBLD.24hr-W/sq ft-

=(Fan)24hr-W/sq ft- =Plant24hr-W/sq ft-=

(Heat)24hr-W/sq ft-=Syst Total24hr-W/sq ft-=

90 day (bEQ)=FUEL HEAT SYSTEM (bEQ)day

Bld,Fan,Plant24hr-W/sq ft-= 49.70Heat24hr-btu/sq ft= 0.00

Syst Total24hr-=90 day (bEQ)=

(bEQ) estimate

Next the full system energy equilibrium (SEE) schematic.


BLD ft2 = %clear sky = InfilLat-ton =

Condenser # floors = Tdry-bulb = Infil-CFM = <(cond)ton= Pipesize-in = (H)T-pipe= Tower Roof ft2 = Twet-bulb= Infilsen-ton =

TCR= > gpmT= > (ewt)T= tfan-kW= N/S wall ft2 = WallNtrans ton=TCR-app= (H)T-total= (H)T-static = Tfan-kW= E/W wall ft2 = WallStrans ton=

(COND)ton= PT-heat = Trange= tfan-%= Wall % glass= WallEtrans ton=(H)cond= < pT-kW= < (lwt)T = tton-ex= Glass U = WallWtranston= WallTot trans ton =

(cond)ft/sec= EfTpump= Tapproach = T#= Wall U = GlassN trans ton =Ptower # = T-Ton-ex= Glass SHGC = GlassS trans ton =

Trg+app = Wall emitt = GlassE-trans ton =Compressor ASHRAE Design RoofTrans ton = GlassW-trans ton = GlassTot-trans-ton=

(chiller)kW= Chicago 90.1-2010 Roofsky lite ton = GlassN-solar-ton =(chiller)lift= Large Office Peopleton = kW GlassS-solar-ton =(chiller)%= Peak day Design 4PM plugton = GlassE-solar ton =(chiller)#= Weather %clear sky = Lightton= GlassW-solar ton = GlassTot-solar-ton =

(CHILLER)kW= conditions Tdry bulb = (int-cfm)to-per-ret= BLD kW= (int cfm)per-ton = >(chiller)kW/ton= Twet bulb = Total Bldint-ton = AHU kW= Tot Bldper-sen-ton = vPlant kW = Tstat-int= SITE kW = Tstat-per = return

(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= airTair supply int= ASHRAE Design Tair supply per=

^ ABS Bld Ton = ^ > Evaporator Ton kW Ton kW V

(evap)ton= (fan)int-ter= (fan)per-ter=TER= Theat-air=

TER-app= (D)heat = ^ EVAPton= Treheat air =

(H)evap= (D)reheat =

(evap)ft/sec=(evap)des-ft/sec= (D)int-air-ton= Interior (D)per-air-ton= Peri

^ V Tair coils = duct Tair coils= ductgpmevap= Psec-heat-ton = (D)int-CFM= ^ (D)per-CFM= ^

(lwt)evap = > Psec-kW= > (ewt)coil= >>>(Coil)sen-ton= ^ (coil)gpm= ^(H)pri-total= v Efdes-sec-p = (coil)cap-ton= UAdesign=

^ (H)pri-pipe= Tbp= Efsec-pump = (coil)H2O-ft/sec= COIL UA=(H)pri-fitings= gpmbp= (H)sec= PLANTton = (coil)des-ft/sec= (one coil)ton=(Ef)c-pump= (H)pri-bp= (H)sec-pipe= LMTD= (H)coil= VPc-heat-ton= v (H)sec-bp= Pipesize-in = (COIL)L+s-ton= ^ ^ ^ (H)coil-des=

^ < pc-kW= (ewt)evap = < (gpm)sec= < (lwt)coil= <<<< Tair VAV= TBLD-AR =Pchiller-# = (FAN)VAV-CFM= (Air)ret-CFM = Return

Chicago 4PM All ElectricFuel Heat (FAN)ton-VAV= (FAN)ret-kW= FanPerformance 4PM Design kW THERM (FAN)kW-VAV= (FAN)ret-ton= V

chillerkW/evapton= BLD.kW= ^ (Air)ret-ton =(plant)kW/site ton= (Fan)kW = 26 F.A.Inlet ^ Tar-to-VAV =CCWSkW/bld ton= Ductheat= statFA= 26 VAV FANS VAVret-ton = WeatherEin-ton = (FA)heat= TFA to VAV = > Tret+FA = InfilVAV-Lat-ton =(Site)kW-Ein-ton = Heat total = Tdry bulb = >(FA)sen-ton = > (dh) = < VAVret-CFM = <PlantkW-Ein-ton = PlantkW= Fresh air > >>> > (FA)CFM= > Efan-VSD= InfilCFM-ton = V

Total Ein-ton = SystkW = Twet bulb = > (FA)Lat-ton=Pumptot-heat-ton = (FA)kW= ExLat-ton =

AHU ExLat-ton = BLD.kW= SEE SCHEMATIC ExCFM =AHU Exsen-ton = CCWSkW = ton blue water temp pink TEx =Tower Tton-Ex = SystkW = air cfm purplewater gpm orange Exsen-ton = V Total Eout-ton = air temp green kW red

System Energy Equilibrium (SEE) Schematic


Documents

Chicago water econ. - file · Web viewCENTRAL CHILLED. WATER SYSTEMS (SEE) MODEL ANALYSIS. Waterside Economizers. Kirby Nelson. PE. ... Chapter 2 deals with increasing supply air