On site chiller monitoring system for predictive, diagnostic and optimization for HP deport road plant

Data collected from the field is systematically being filtered by a macro program for steady state operating parameters which are then being processed with a MS Solver for critical irrev

ON-SITE CHILLER MONITORING SYSTEM FOR

PREDICTION, DIAGNOSTIC AND

OPTIMIZATION

At

HP DEPOT ROAD PLANT

GARY TANG CHEE WEN B.TECH (Hons.), NUS

A THESIS SUBMITTED

FOR THE DEGREE OF MASTER OF ENGINEERING

DEPARTMENT OF MECHANICAL

ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE

DECEMBER 2007

ABSTRACT

As large commercial and plants owners become more conscious and critical

on chilled water system that not only consume a significant proportion of electric

energy in a built environment, but also contribute to the bottom line of the operations,

be it for human comfort or meeting process requirements for business continuity, an accurate, reliable and yet sufficiently comprehensive chiller monitoring system will become an integral part of today and future centralized chillers, which previously often being regarded as black-box

In view of these, Hewlett-Packard (HP) Depot Road plant chiller monitoring system is being commissioned with the ultimate aim to predict, diagnose and optimize the respective chillers in the system with non intrusive measurements consistent with the approach of Gordon and Ng Data collected from the field is systematically being filtered by a macro program for steady state operating parameters which are then being processed with a MS Solver for critical irreversibility parameters such as internal entropy generation, finite rate heat exchange and heat leaks, which are used to track the chiller performance Concomitantly, multiple linear regressions are performed to statistically determine the threshold of these parameters to minimize any false representations

Despite the large and yet complex chillers operations, equipped with built-in heat recovery such as economizer and intricate control mechanisms such as feed- forward adaptive control, the analytical model developed by Gordon and Ng from the basic principles of thermodynamics has been successfully tested and served as a basis for the analysis and evaluation of this research project

Keywords: black-box, non intrusive, on-site real time, energy center, irreversibilities and root mean square error

ACKNOWLEDMENT

The author wishes to express sincere appreciation to project supervisor, Prof

KC Ng, and Mr Jayaprakash the postgraduate PhD student in the Department of Mechanical Engineering, National University of Singapore for their invaluable guidance, support and encouragement during the planning, execution and assessment

of the project Also, thanks to Mr Sacadevan, from Heat Transfer laboratory, for the site verification of the field RTD temperature measurements Also, acknowledging the contribution from other colleagues in HP, namely Chen Fei and Khee Boon for their help and advises during the project implementation and instrumentation and control set up

iii

21 Thermodynamic and operational fundamentals of mechanical chiller

2.2 Universal Chiller Model by Gordon and Ng - 5-5-2 2-5 Chapter3 Equipment and Instrument Detail s-«555+c<xexeeeeeeeeeeeeee 3= 3.1 GillettdetlliÌBioeeereaeeniooroniissvGi01813511236036131610004052350413805360040030080p5oE58gvsvz2SL

32 Field instrument and data acquisition c c+ceccsccc-e.ce.e.- 3=

33 Measurement unCertainty . ¿- 5-5-5225 5s+xesszeexereerrrxrrrrreereevee T7 Chapter 4 Fault Scenarios and Data Processing -+ e + - đcÏ

4.2 Steady state data filtration

4.3 Determining COP prediction and irreversible parameters .- 4-3 Chapter 5 Data Analysis and Discussion .c0.cecssesseseeseeeeeseeeseeneeeeseeeereeeeneee 7d

51 Condenser tubes fouling - ¿- 55-52 52s éSzketekerkrkrrkrkerkrrree 5-1

52 High condenser coolant inlet tetaperafUre ‹-s- 5-55 ssexvzexeex 5-6

53 Condenser coolant flow deficiency

Chapter 6 Conclusion and Recommendation .sccessecesseseseeseeeeteseeeesteeeseeeeses 6-1 Appendix A HP Depot Road Chilled Water System Equipment Schedule A-1 Appendix B Manufacturer Documented Chiller Part Load Efficiency B-1 Appendix C Measurement UncertaintY .- - 5+ ++svs++xe+zxerrxexererrerxrree C-1 Appendix D Field Data s65 sxsxseseeeerrrerrrrrrrrrrrrrrrrrrrrrrrrrreee TS AppendixE.Macro PfopramimiifE:‹‹-‹ se‹s csssszsss2,s21615422121140160156 0 00 10050080156508880668066 E-1

Appendix F Typical Solver for COPprea, ASim, R and Q\eak -. . . F>

List of Figures

Figure 1: WW BI Chiller Chilled Water System Schematic . 1-2 Figure 2: WW B1 Chiller Condenser Water System Schematic - |=2

Figure 3: Singapore LT Electricity Tariff vs Pegged Fuel Price

Figure 4: HP Depot Road Plant Energy Profile esesccesssscssseseeeseseseeeeeeseseeeneeeees 1-4 Figure 5: HPSG Carbon Footprint and Intensity .0 cseseeeeseeeeeseseeeeeerseeeseeenee LAS, Figure 6: Chiller 4 Condenser Approach Temperature after Online Tube Cleaning 1-7 Figure 7: Chiller 4 kW/RT after Online Tube Cleaning -. -. -.-« Ï=Ñ Figure 8: Schematic of Reversible Carnot Refrigerant CycÌe -. « 2-2 Figure 9: Schematic of a Real Vapor Compression Mechanical Chiller with Complete Operational System :.cccesceseeesesessessseseseseeesseneecscscecseerseensnsnsesssesseaceeeceresseseteseesee 274 Eigure 10: General CVHE and CVHG Unit Componens -. -e- 7 Figure 11: 2-stage Economizer with 3-stage ChilÌe ¿ -c<ccc+cv-c e.- 3~2)

Figure 12: Manufacture Performance Data of 850 RT Chiller, kW/RT vs Load 3-4

Figure 13: Typical SCADA Graphic for Chiller ccc cece escent 28

Figure 14: Chiller 1 and 2 Before/After Tube Cleaning (COPpreq vs COP measured &

Figure 15: Chiller 1 and 2 Thermal Resistance with 1 and 2-Mean Standard Error 5-4 Figure 16: Chiller 1 and 2 Internal Entropy Generation with 1 and 2-Mean Standard EITÔE1566669021556058010S0GBGI2i0GI3G4ISSS3SHEI0iliSvbSisGiSR1310GxStiil2388@xsysygsisgasoÐ=5

Figure 17: Chiller 1 at Various Condenser Coolant Inlet Temperature (COPprea vs COP Measure and 1/COP prea VS 1/Qevap) Charts

Figure 18: Chiller 2,at Various Condenser Coolant Inlet Temperature (COPprea VS

COP Measure and 1/COPpwa vs 1/Qevap) ChartS 55555<55ccccc 2=

vi

Figure 19: Chiller 4 at Various Condenser Coolant Inlet Temperature (COP prea vs

COP Measure and 1/COPpred VS 1/Q¿¿ap) ChaTts 5-5255 25+2c2cezzerxerxrrrr 5-9

Figure 20: Chiller 5 at Various Condenser Coolant Inlet Temperature (COP prea vs

COP Measure and 1/COPpza vs 1/Qvap) Charts -25-25-555<cc<<c<cscc 5-10

Figure 21: Chiller 1, 2, 4 and 5 Thermal Resistance with 1 and 2-Mean Standard Error

Figure 22: Chiller 1, 2, 4 and 5 Internal Entropy Generation with 1 and 2-Mean

Standard Ervot ccssssssssssssessssssssssssssssssessssessssssssssssssesssscsssseasscesssesneasssessscssesseeeeee S71 Figure 23: Chiller 4 and 5 at Normal and Low Condenser Coolant Flow Rate (COP prea

vs COP Measure and 1/COP prea VS 1/Qevap) Charts .scesscsssssessessesssesecssecessseseeneesees 5-14

Figure 24: Chiller 4 and 5 Thermal Resistance with 1 and 2-Mean Standard Error 5-16 Figure 25: Chiller 4 and 5 Internal Entropy Generation with 1 and 2-Mean Standard

Figure 26: Typical Plot with Experimental and OEM as Designed Data for 1/COP prea

vii

List of Tables

Table 1: 2005 Crude Oil and Natural Gas Reserves, Production and Consumption 1-4

Table 2: Chiller 1 and 2 Critical Irreversibility Parameters Before/After Tubes

Cleaning

Table 3: Chiller 1, 2, 4 and 5 Irreversibility Parameters for Various Condenser

Coolant Inlet Tem perature’s:sscisscsescceosecasnevnsinensasveonnaveuvanvnecusminssceccansuasearseanussnancsnensse 5-6 Table 4: Chiller 4 and 5 Irreversibility Parameters at Normal/Low Condenser Coolant ElbW RR[E:::zssgg 806 tEEL0001G3196018058G0001GG818804tA3853 12L GNEGRGIRSoSSngultsseremiiD-15

viii

Hewlett-Packard Singapore

resistance temperature detector

kilowatt per refrigeration ton kilowatt-hour

kilovolt auto tube cleaning simple thermodynamic model work input

heat transfer heat removal to cold reservoir heat removal to hot reservoir American Refrigeration Institute Coefficient of Performance rate of internal entropy generation effective thermal resistance of heat exchangers equivalent heat leak parameters of a chiller chilled water supply/return

condenser water supply/return root mean square

ix

Chapter 1 Introduction

In a typical plant operation, chilled water system is often regarded to as energy center, and their “uptime” or fully operational period also plays an important role in ensuring interruption free business operation It is therefore imperative to ensure that these equipments are constantly being monitored with a reliable and accurate monitoring system

HP Depot Road building is served by two chiller systems, one at West Wing Basement 1 (WW BI); the other one at Central Utilities Building Level 2 (CUB L2) The former serves the entire Depot Road building load for thermal comfort and process cooling purposes Whilst the latter serves only the Jetmos and Tij 4 wafer fab clean rooms and their other related cooling processes This project will focus on the non intrusive measurement and analysis of the WW B1 chillers

The WW BI chiller system consists of 2 x 500 RT and 3 x 850 RT Trane R123 centrifugal chillers with primary and secondary chilled water loop The chillers are supported by 4 cooling towers located at the West Wing Roof Top (WW LS) The cooling towers are of counter flow type with cooling capacity of

1500 RT each Both the chiller and cooling tower capacity is based on N+1 During normal operation, 2 x 500 RT and 2 x 850 RT chillers are in operation with 1 x 850 RT chiller as standby Figure 1 and 2 depict the HP Depot Road WW

BI chiller chilled and condenser water system schematic The detailed equipment schedule is outlined in Appendix A

1-1

war ciw Sytem ine Jane 8 Sg

1.2 Motivation for the research project

1.2.1 Energy costs

With escalation crude oil prices which reached a record high of US$100/-

a barrel in the later half of 2007 LH, Singapore’s economy which hinges on the fossil fuel would not be spared The Singapore’s households energy cost has reached a high of S$0.2138/kWh for the period of October to December 2007 The common industrial high tension large (22 kV) rate has also recorded a new high of S$0.1888/kWh for peak period (7 am to 11 pm) for the same period Figure 3 shows the recent changes in the fuel and electricity tariffs of Singapore

Figure 3: Singapore LT Electricity Tariff vs Pegged Fuel Price

The quest for economic growth will inadvertently increase the energy requirements and costs as the majority of the energy is produced by fossil fuels, which are of finite natural resources The proven recoverable reserves and total consumption as reported by the World Energy Council’s Survey of Energy

Resources 2007 ”! is shown in Table 1 Based on these data, the crude oil and

natural gas is projected to diminish in about 43 and 63 years, respectively

Tariff

(g/kWh}

Table 1: 2005 Crude Oil and Natural Gas Reserves, Production and Consumption

Total proved Total production 'Total consumption recoverable reserves

gas liquid (million

Source: World Energy Council’s Survey of Energy Resources 2007

The increase in fuel costs has had a significant impact to HP Depot Road plant operation, even with contestable rate since November 2006 The energy cost

has increased 37% from November 2005 to November 2007, whereas the total

energy consumption only increases about 18% despite an increase in production activities for the same period of time, as shown in Figure 4

HP Depot Road Energy Tracking

This has prompted the management to seriously consider the implementation of energy efficiency and optimization projects Besides the chiller monitoring project, many other projects have been implemented

1.2.2 Environmental impact

Global warming and climate change poses similar pressing issues to

energy studies Thus, the chiller plant performance improvement could

significantly help to reduce the carbon emission footprint Even tough, the carbon intensity of HP Singapore has declined as compared to the year 2002, owing to business expansion, good business growth and energy conservation program, the carbon footprint has been steadily increased as shown in Figure 5

HPSG Cabon Footprint and Intensity

—®—HPSG CO2 eq _‹- LJMS CO2eq ~#-HPSG Cabon Inlensiy compare lo FY02 level

Figure 5: HPSG Carbon Footprint and Intensity

100%

80% 70%

10% 0%

The HP management has recognized the need to reduce the contribution to carbon emission so as to be aligned with the environmental management system, ISO14k, a tool that has been put in place and for good corporate citizenship of the

company

1.2.3 System efficiency

HP Depot Road chiller plant has been audited by a third party energy consultant for its facilities energy usage The energy indices for the chiller, cooling tower, chilled water and condenser water pumps are 0.554, 0.057, 0.065 and 0.106 kW/RT, respectively By the industry standards, this is considered to be

a good performance status but there are rooms for improvement

1.2.4 System reliability

There is direct relationship between chiller efficiency and its uptime It is a known fact that cleaner condenser water tubes would not only increase the chiller efficiency but also ensure the chiller would not surge and trip due to lower heat rejection rates This can be easily proven with effectiveness of the heat exchanger where, e=l—e *“”, and e"⁄ =1! with T, =T.-T,

ch

Ta, Tc and Tạ are condenser approach, saturated refrigerant and coolant

outlet temperatures, respectively The lower the approach temperature, the lower

is the eN™Y, and hence increases in the heat exchanger effectiveness From the 1# Law of Thermodynamic for a vapor compression cycle, a higher condenser heat rejection will have a positive impact to chiller operation when there is an increase

in cooling load demand and compressor work rate; hence increases the overall chiller efficiency and effectiveness and reliability This is depicted in Figure 6,

where a reduction of 1°C in condenser approach temperature when the particular

chiller condenser tubes being cleaned online and on-load with brush and basket

type of auto tube cleaning system, and Figure 7 depicts that the chiller kW/RT has

reduced by more than 10% This is a classic example of the capability of the

online monitoring and ATC system

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Figure 6: Chiller 4 Condenser Approach Temperature after Online Tube Cleaning

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SP HVEBSVR ODCOREOEER AMROAGHTE 90 10% t—=—(Decinal WWppisevwMb 327280 207670 Gyete 1920081106 XTET-IBI-MU-S ĐỊT HEREĐSR CH CONDENSER APPROACH TE 00 40° 1 Dong Wipgtnanrar 227680 327670 Cycke 3920061105

Figure 7: Chiller 4 kW/RT after Online Tube Cleaning

1.3 Objectives

There is a saying “you cannot manage what you do not measure” This is

absolutely true There are 3 main objectives for this project:

1 To set up a reliable and accurate chiller monitoring system,

2 To analyze field data for the prediction, diagnostic and optimization of the

chillers as well as the chilled and condenser water pumping systems,

3 To serve as a learning curve for an on-site real-time chiller prediction,

diagnostic and optimization

1-8

1.4 Scope of research and organization report

The scope of this research project can be categorized into 2 main categories:

1 Installation of the appropriate chiller monitoring system and verify the

measurement accuracy and systematic uncertainties of the measurement

2 Investigate of the chiller performance under various predetermined fault scenarios based on proven theoretical methodology

The report is structured in 6 chapters The subsequent Chapter 2 describes

the basic theory of thermodynamic for a vapor compression cycle and introduces

the generally acceptable simple thermodynamic model (STM) The model is developed by JM Gordon and KC Ng for the predictive, diagnostic and optimization for real centrifugal chillers Chapter 3 provides the insight on the detail of the chillers to be investigated and field instrumentation set up The data acquisition system and measurement uncertainties are presented in this chapter This is followed by Chapter 4 which aims at providing the predetermined faults scenarios and details on the data processing methodology towards establishing the chiller’s irreversibility parameters and performance prediction Detailed discussion on the findings from the operational scenarios is presented in Chapter

5, with tables and charts Finally, Chapter 6 summarizes the results, reveals the

challenges on STM and suggests future improvements to on-site energy monitoring and control programs

1-9

1 Work W is input, adiabatically compressing the refrigerant and raising its

temperature

2 The refrigerant rejects heat Qhot, isothermally to a hot reservoir at temperature Tho, which is typically at 35.0°C, in accordance to ARI

Standard 550

3 The refrigerant is expanded adiabatically and isentropic

4 Heat Qcoia is removed from cold reservoir at temperature Teoig by

isothermal transfer to the refrigerant T.oig is usually designed at 6.7°C, according to ARI Standard 550

For ideal cycle, W + Ó „„ = Ở,„„

2-1

Heat Rejection

\ Werk Input, Ww Refrigeration Cycle

(Chiller)

Figure 8: Schematic of Reversible Carnot Refrigerant Cycle

In comparison, the real COP of a chiller is usually much lower than the Carnot cycle’s COP In a real chiller, many dissipative losses are incurred For the purpose of determining the efficiency of a real chiller system, the Coefficient of Performance COP is introduced It is defined as ratio of useful effect or cooling capacity to the power input to achieve that useful effect as shown in following expression:

2-2

external components of the chiller which mainly split into 2 systems: condenser water and chilled water systems The former consists of cooling tower and condenser water pump whilst the latter comprises of air handling unit and chilled water pump The entire system could also be designed to serve a multitude of air handling units, hence also referred to as central chiller plant.

Cooling Tower

Air Handling Unit

Figure 9: Schematic of a Real Vapor Compression Mechanical Chiller with Complete

Operational System

2-4

Non intrusive measurements such as flow and temperature sensors are

installed in the coolant circuits together with the power monitoring to determine the work input to the compressor

As opposed to the ideal cycle, a real cycle is effected by the following irreversibilities processes and conditions:

1 finite size heat exchangers and hence the finite rate heat transfer losses

2 non isentropic compression

3 no isentropic expansion via throttling valve

4 pressure and mechanical friction losses

5 heat leak

6 and, other operational faults which will be discussed in Chapter 4 and 5

Hence, actual COP is far below the Carnot limit

2.2 Universal Chiller Model by Gordon and Ng

Cooling capacity and COP are important deterministic performance parameters for chiller manufacturer; ACMV system designers and integrators; users and plant owners in designing and selection of chillers and centralized chilled water system

In a simplified model and assuming steady state operation, there are 3 critical irreversible parameters which govern the performance of a typical mechanical chiller, namely rate of internal dissipation or entropy production, AS,,, (kW/K); effective thermal resistance of heat exchangers, R (K/kW) and equivalent heat leak parameter of a chiller, O° dạy (kW) These parameters can be derived from the 1“ and 2™ Law of Thermodynamic as shown in Equation 5.5 of Cool Thermodynamic by Jeffrey Gordon and KC Ng BỊ,

2-5

Equation (1) Where,

T:"_, is evaporator heat exchanger coolant inlet temperature evap

T7; 1S condenser heat exchanger coolant inlet temperature «

AS int is rate of internal entropy generation

Q is equivalent heat leak parameter of a chiller

R is effective thermal resistance of heat exchangers

Q.,ay is evaporator heat removal rate

Rearranging,

Te |- 1 |e in, Eat ns Teg), RO E 1

Su cond COP] Quy = Ting T5 GÓP

And, | 1 | | uy Toon ‘evap

G71”

C=O leak * evap

em ~ Sevap pin opin

of field performance data, they could be analyzed or regressed and worked towards determining the predicted chiller COP Details of such analysis will be discussed in sections 4.2 and 4.3

2-7

Chapter 3 Equipment and Instrument Detail

3.7 Chiller details

The chiller plant at HP comprises 5 chillers They are Trane 3-stage centrifugal chillers, direct drive, water cooled with R123 refrigerant, equipped with inter-stage economizer These models are the CVHE 590 and CVHG 670 for

2 x 500 RT and 3 x 850 RT chillers, respectively Figure 10 shows the typical major components diagram These chillers are designed and tested according to ARI Standard 550 — 92

Refigerant Pump

Figure 10: General CVHE and CVHG Unit Components

Both condenser and evaporator heat exchangers are of two passes type with internally enhanced copper tubes In contrast to Yongzhong Jia and T.Agami Reddy ", these chillers are equipped with variable inlet guide vanes which throttle the refrigerant gas flow to meet the part load demand and pre-rotating the

gas before entry into the impeller However, the control of these guide vanes is not based on feed-forward chilled water return temperature

For 3-stage chiller with 2-stage economizer and refrigerant orifice system

as depicted in Figure 11, liquid refrigerant leaving the condenser at state point 6 flows through the orifice plat A and enters the high pressure side of the economizer The purpose of this orifice and economizer is to pre-flash a small amount refrigerant at an intermediate pressure, P1 P1 is between evaporator and condenser pressures Pre-flashing some liquid refrigerant cools the remaining liquid to state point 7 The cooler refrigerant gas from this high pressure side mixed with the entering gas in the third stage compressor to lower the enthalpy, near state point 4 Refrigerant leaving the first stage economizer flows through the second orifice B and enters the second stage economizer Some refrigerant is pre- flashed at intermediate pressure P2 Pre-flashing the liquid refrigerant cools the remaining liquid to state point 8 The cooler refrigerant gas from this low pressure side mixed with the entering gas in the second stage compressor to lower the enthalpy, near state point 3 To complete the operating cycle, liquid refrigerant leaving the economizer at state point 8 flows through a third orifice C where refrigerant pressure and temperature are reduced to evaporator conditions at state point 1

Another benefit of flashing refrigerant is to increase the total evaporator refrigeration effect from RE’ to RE this is believe to provide up to 7% energy saving compared to chiller without economizer

3-3

ý = 3.4526E-1ĐẺ - 1.2082E-131Ẻ + 1.7226E-10x' -1.2878E-07¢ +

Load (RT)

Figure 12: Manufacture Performance Data of 850 RT Chiller, kW/RT vs Load

Figure 12 shows the rated chiller efficiency at part load Appendix B shows the detail 850 and 500 RT chiller performance as designed by the original equipment manufacturer, embedded in MS Excel file

3.2 Field instrument and data acquisition

All the necessary data for the chiller monitoring, data acquisition and

analysis are based on non intrusive, continuous online measurement The

measured data are coolants flow rates and temperatures; and in power input to the

compressor

1 For flow measurements, the E+H electromagnetic flow sensors are installed The model of the instrument is PROline Promag 10W, consists

3-4

of various sizes to measure the CHW and CW flow for the 5 chillers The

system accuracy is +0.5%

For temperature measurements, the E+H TR10 PT100 temperature sensors

are installed, to measure CHWS/R and CWS/R temperatures for the 5

chillers The sensor accuracy is Class 1/3 DIN B

For power measurements, the Schneider Electric power transducer and PM500 Merlin Gerin power meter is used The reported uncertainty of the sensor is within +1% of the value measured

Data acquisition from field instruments is achieved via an Allen Bradley PLC, model SLC-505 All the analog signal inputs from field instruments such as RTD for temperature measurement, 4-20mA for flow and power measurement are being connected to the respective I/O cards in the PLC which will then be routed via Hub Switch by 2 pair fiber optic cables to the respective servers which is installed with Wonderware Intouch software version 8 SP 1, for data storage and retrieval The system has a sampling capability of every 10 sec interval Figure 13 depicts a typical the SCADA graphic used for the monitoring and data acquisition of the chiller facility

3-5

mnssaud -TNVH3901138

3.3 Measurement uncertainty

Based on manufacturers’ data and field verification on the measurement instrument, the root mean square (RMS) error for COP monitoring is estimated to

be 3.1% and 16.23%, respectively However, as the site flow verification is based

on pump curve which is subjected of ambiguity, and that all the new flow meters are supplied with calibration cert, hence the flow rate accuracy is to be based on

manufacturer’s data of +0.5% As a result, based on the combination of site

verification (for temperature and power) and manufacturer data (for flow), the maximum total uncertainty for determining COP experimentally based on rms error is about 6.22% Appendix C shows the calculation for the change COPs

3-7

Chapter 4 Fault Scenarios and Data Processing

Followings are the predetermined fault scenarios for the analysis:

Chiller 1 — before and after condenser tube cleaning on 1“ and 15" May

Scenarios 1 and 2 represent the condenser tubes fouling, whereas scenarios 3,

4, 5 and 6 represent high condenser coolant inlet temperature due to cooling tower under performance or ambient web bulb temperature, as a deterministic factor for cooling tower performance, exceeded the normal operating range

4-1

And finally, scenarios 7 and 8 provide the fault scenarios due to condenser coolant flow deficiency

Followings are some observations related to the operation for the scenarios:

i)

ii)

iii)

iv)

Condenser water supply temperature is very much depending on the ambient

wet bulb temperature It may fluctuate within +0.5°C of the preset temperature Cooling tower variable speed drive will regulate the speed of the fan to meet the requisite set point

Cooling load is subjected to the operational demand; hence it’s not being controlled i.e chilled water return temperature will fluctuate according to load demand

Coolant flow rates are the nominal Actual flow rates are at the most 6% deviate from these nominal flow rates

All relevant data sets captured as close as possible to the scenarios, in term

of timing, for better representation and to prevent other time lapse interferences

4.2 Steady state data filtration

Woi

this

Date analysis is aided by the ActiveFactory suite version 8.0.3 in the nderware which is set to sample each data at every 10 sec interval Base on sampling time, with the 7 chiller parameters being measured by the non- intrusive method such as power input (Pin); condenser water supply and return

tem;

T),

peratures (CWS/R T); chilled water supply and return temperature (CHWS/R

chilled and condenser water flow rate (CHW/CW FP), a total of 60,780 data

will be collected for each chiller for each day These raw data is first tabulated by

MS Excel, and averaged for every 1 minute to bring down the number of data to 10,080 data for easy handling Appendix D shows typical data extracted from the excel file

In order to distinguish the steady states from the transients, a Macro programming is being developed to determine the steady state operating parameters for power input (Pin); chilled water return temperature (CHWR T); chilled water supply temperature (CHWS 1); chilled water flow-rate (CHW F) The predetermined boundary parameters for steady state are Pj, and CHWR T

Initial boundary conditions of +0.5% for Pi, and +0.1°C for CHWR T in 15

minutes of steady state yielded minimum steady state data A more loosen parameters was agreed upon, and changed to +2% and +0.15°C for Pin and CHWR

T, respectively, and with the 5 minutes steady state, these boundary limits provide more data for assertion But this could be at the expense of data representation and accuracy in the later stage of development work Appendix E shows the macro programming details for the steady state filtering

4.3 Determining COP prediction and irreversible

parameters

From the steady state data, the COP predicted and critical irreversibility parameters namely internal entropy production, AS,,, (kW/K); effective thermal resistance of heat exchangers, R (K/kW) and equivalent heat leak parameter of a chiller, oF (kW) is being determined by Microsoft Excel Solver For such analysis, Equation 1 is rearranged into smaller terms as follows:

rin

Left term: Y=? wl -1

Te, cond COP