Evaluation of Chemical and Non-Chemical Treatment

Methods for Condenser Water

Ng Wai Lun1, Yoon Li Wan1 and Satesh Narayana Namasivayam1, Chen Thiam

Leong2

1 School of Engineering, Faculty of Innovation and Technology, Taylor’s University Lakeside Campus, No. 1, Jalan

Taylor’s, 47500 Subang Jaya, Selangor, Malaysia. 2 Green Building Index Sdn Bhd, Level 4, PAM Centre, 99L, Jalan Tandok, Bangsar, 59100, Kuala Lumpur,

Malaysia

*Corresponding author: LiWan.Yoon@taylors.edu.my

Abstract. In the Heating, Ventilation and Air Conditioning (HVAC) field, condenser water is used to remove heat from

the refrigerant cycle and is cooled at cooling towers. Due to the high operating temperatures of 29°C to 38°C, the condenser

water cycle is vulnerable to operating issues such as scaling, corrosion and microbiological proliferation; which can be

mitigated through either chemical or non-chemical treatment methods. In this paper, the chemical and non-chemical

treatment methods for condenser water treatment in the Heating, Ventilation and Air Conditioning (HVAC) systems are

compared in terms of efficiency (scaling, corrosion and microbiological proliferation control) and environmental impact.

The efficiency of one chemical treatment system (descalant) and three non-chemical treatment systems (Merus Ring, Power

Pulsed and Ultra Low Frequency) are investigated by taking condenser water samples from the cooling tower basins

biweekly for three months to characterize for pH, water alkalinity, iron content, chloride content, total dissolved solids

(TDS) content, electrical conductivity and water hardness, which are compared to the Japan Refrigeration and Air

Conditioning Industry Association Standards (JRA-GL-02-1994) and applied to the Langelier Saturation Index (LSI),

Ryznar Stability Index (RSI) and Practical (Puckorious) Scaling Index (PSI) to predict the scale formation in condenser

water samples. The temperature differences between chilled waters for all systems investigated are recorded to relate the

characterized parameters to chiller efficiency. The environmental impacts for all systems investigated are assessed by

focusing on the operational stage of all system where the main source of environmental damage is due to the electrical

consumption by the HVAC systems. The results yield that all systems investigated comply to the industrial standards. LSI

and RSI proved that all condenser waters are saturated with calcium ions but PSI proved that scale formations in the systems

investigated are unlikely as the scales are likely to remain dissolved in the condenser water. Consistent temperature

differences of chilled water are observed throughout the research period which show that the performance of chillers in

each system are optimal, which proves that non-chemical treatment systems are as efficient (in terms of corrosion, scaling

and microbial activity control) as chemical treatment system. Environmental impact analysis concluded that chemical

treatment system has the highest annual equivalent CO2 emission per cooling capacity of 868.30 kg CO2 e/year RT. Thus,

non-chemical treatment systems have lesser environmental impact than chemical treatment system.

Key words: HVAC System, Condenser Water Treatment Systems, Corrosion, Scaling, Microbiological Proliferation

INTRODUCTION

The typical Heating, Ventilation and Air-conditioning (HVAC) system of a commercial building consists of key

systems such as the chilled water cycle, refrigerant cycle and the condenser water cycle. As seen in Figure 1, the

chilled water first enters the Air Handling Unit (AHU) where it exchanges heat with the air in the room or space. The

air turns cooler and the chilled water temperature increases. The chilled water then flows to an evaporator where it

exchanges het with the refrigerant to be cooled before repeating the cycle again. The warm refrigerant is then

compressed to enter the condenser where it exchanges heat with condenser water before passing through an expansion

valve to be heated up again in the evaporator. The warm condenser water first enters the cooling tower to be cooled

by using ambient air. After being cooled, the condenser water then repeats the cycle by entering the condenser again

to exchange heat with the warm refrigerant.

FIGURE 1: Illustration of a typical HVAC system of a commercial building.

As illustrated in Figure 1, all three systems are operating in closed loops. Thus, if no proper treatment was done to

the systems, impurities in the chilled water and condenser water could cause issues such as scaling, corrosion and

microbiological proliferation, which can decrease the efficiency of the cooling system [1].

The condenser water system is highly vulnerable to these operational issues due to the high operating conditions

of 29°C to 38°C [2], as compared to chilled water with the operating temperatures of 5°C to 7°C.As temperature

increases, the possibility of corrosion and scaling increases as soluble solids at low temperatures starts forming at high

temperatures [1]. In addition to that, microbiological activities typically take place at ambient temperatures.

Condenser water treatment methods can be separated into chemical methods that include the use of chemicals such

as biocides, corrosion and scaling inhibitors as well as the non-chemical treatment methods that include the use of

devices that use physical principles such as interfering and resonance oscillations [3], power-pulsed device [4] and

ultra-low frequency in the control of scaling, corrosion and microbial activity.

To catalyze the application of non-chemical treatment methods for condenser water loops in HVAC systems,

Malaysia’s first green rating tool, Green Building Index (GBI) pledges to award one (1) innovation point for buildings

that use non-chemical methods for the treatment of condenser water [5].

Although numerous studies have proven the effectiveness of the non-chemical treatment methods in controlling

scaling, corrosion and microbiological proliferation [3, 4], these studies are conducted without benchmarking with

chemical treatment methods. This shows that the efficiency comparison (in terms of scaling, corrosion and microbial

activity control) between chemical treatment systems and non-chemical treatment systems is yet to be investigated.

In the cradle to grave lifecycle of both chemical and non-chemical treatment methods for condenser water in the

HVAC systems, there will certainly be environmental impact such as the production of greenhouse gases (GHG) due

to various activities ranging from the manufacture stage to the transportation, construction, maintenance and operation

as well as the demolition stage [6].

Quantification of environmental impact requires lifecycle assessments and that there are no known studies

conducted to compare the environmental impacts between the chemical and non-chemical treatment methods for

condenser water in HVAC systems.

In this study, the first objective is to identify the suitable system with effective corrosion and scaling control for

condenser water treatment among the chemical and non-chemical treatment systems investigated. The second

objective is to evaluate the environmental impact during the operational stage of the chemical and non-chemical

treatment systems for condenser water treatment.

RESEARCH METHODOLOGY

In this study, three non-chemical treatment methods for condenser water are investigated. The first system uses

Merus ring magnetic device, denoted as system A, the second system uses ultra-low frequency technology, denoted

as system B that and the third system uses power pulsed device, denoted as system C. The chemical treatment method

that is investigated that uses descalant and biocide, denoted by system D.

Efficiency Analysis

The efficiency analysis is conducted in two aspects, treatment efficiency and chiller efficiency. Treatment

efficiency includes the sampling and characterization of condenser water as well as the prediction of scaling and

corrosion. The chiller efficiency is analyzed by taking the temperature differences of chilled water in the chillers of

the systems investigated.

Sampling and Characterization of Condenser Water

The sampling of the condenser water from systems A to D are conducted biweekly for nine (9) weeks with the

assistance from engineers responsible for the cooling tower operations of the systems investigated. During each

sampling trial, three (3) samples are taken at random for all running cooling towers during the time of sampling. The

condenser water samples are stored at 4°C before further testing and analysis.

The characterization of condenser water samples is conducted by analyzing for the pH, water alkalinity, water

hardness, electrical conductivity, total dissolved solids (TDS) content, chloride and iron content. The pH, TDS and

electrical conductivity can be measured by using the pH meter (Eutech, pH700, Fisher).

Test kits such as the iron test kit, alkalinity test kit and chloride test kit are purchased from Merck and are used to

test for the iron content, water alkalinity and chloride content respectively. Spectrophotometer (Prove 300, Merck,

VSA) is used to measure the absorbance at respective wavelength for different tests.

The water hardness is evaluated through the colorimetric titration method that uses ethylene diamine tetra acetic

acid (EDTA) and Solochrome black-T (EBT). In this method, EBT and ammonium buffer solution are added to the

condenser water samples. EDTA is then used to titrate the water samples until it turns from wine red to steel blue.

This method requires a calibration curve constructed by using standard hard water in replacement of the condenser

water in the titration to relate the water hardness to the volume of EDTA required to reach the end point of titration

where the color change occurs.

For microbiological proliferation, the heterotrophic plate count (HPC) method is used to characterized the colonies

of heterotrophic bacteria present in the condenser water samples. In addition, the test for Legionella sp. is conducted.

The test for microbiological proliferation will be conducted twice throughout the study period.

The raw data obtained from the characterization is initially compared with Japan Refrigeration and Air

Conditioning Industry Association Standards (JRA-GL-02-1994) to check if the operating parameters of the condenser

water are met. Appendix 1 shows a copy of the JRA-GL-02-1994 extracted from the Japan Refrigeration and Air

Conditioning Industry Association [7].

The analysis of variance (ANOVA) single factor is used to assess the significance of batch to batch variations in

readings. The significance is evaluated at p<0.05.

Prediction of Scaling and Corrosion

The scaling and corrosion potential for the condenser water samples are predicted by using LSI, RSI and PSI as it

is widely applicable in the study of potentially corrosion and circulating water [8, 9, 10],. The formulae for the

calculations of LSI, RSI and PSI are tabulated in Table 1. Table 2 shows the interpretation of the indices calculated.

TABLE 1: Tabulation of formulae for LSI, RSI and PSI.

Index Equations

Langelier Saturation Index

(LSI)

𝐿𝑆𝐼 = 𝑝𝐻 − 𝑝𝐻𝑠 Eq. (1)

𝑝𝐻𝑠 =

𝐴 + 𝐵 − 𝑙𝑜𝑔10(𝐶𝑎2+) − 𝑙𝑜𝑔10(𝐴𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦)

For pH ≤ 9.3

Eq. (2)

𝑝𝐻𝑠 = (9.3 + 𝐴 + 𝐵) − (𝐶 + 𝐷) For pH > 9.3 Eq. (3)

𝐿𝑆𝐼 = 𝑝𝐻 − 𝑝𝐻𝑠 Eq. (4)

Ryznar Stability Index (RSI) 𝑅𝑆𝐼 = 2𝑝𝐻𝑠 − 𝑝𝐻 Eq. (5)

Practical (Puckorious) Scaling

Index (PSI)

𝑃𝑆𝐼 = 2𝑝𝐻𝑠 − 𝑝𝐻𝑒𝑞 Eq. (6)

𝐴 = 𝑙𝑜𝑔10[𝑇𝐷𝑆] − 1

10 Eq. (7)

𝐵 = −13.2 × 𝑙𝑜𝑔10(°𝐶 + 273) + 34.55 Eq. (8)

𝐶 = 𝑙𝑜𝑔10[𝐶𝑎2+𝑎𝑠 𝐶𝑎𝐶𝑂3] − 0.4 Eq. (9)

𝐷 = 𝑙𝑜𝑔10[𝐴𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦] Eq. (10)

𝑝𝐻𝑒𝑞 = 1.465 × 𝑙𝑜𝑔10[𝐴𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦] + 4.54 Eq. (11)

[𝐴𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦] = [𝐻𝐶𝑂3−] + 2[𝐶𝑂3

2−] + [𝑂𝐻−] Eq. (12)

TABLE 2: Tabulation of index values and the corresponding water condition.

Index Index Values Water Conditions

LSI LSI > 0 Super saturated, tend to precipitate calcium carbonate

LSI = 0 Saturated, calcium carbonate is in equilibrium

LSI < 0 Under saturated, tend to dissolve solid calcium carbonate

RSI RSI < 6 Super saturated, tend to precipitate calcium carbonate

6 < RSI < 7 Saturated, calcium carbonate is in equilibrium

RSI > 7 Under saturated, tend to dissolve solid calcium carbonate

PSI PSI < 6 Scaling is unlikely to occur

6 <PSI <7 Water is stable

PSI > 7 Likely to dissolve scale

Where:

𝑝𝐻𝑠 : Saturation pH

𝑝𝐻𝑒𝑞 : Equilibrium pH

[𝑇𝐷𝑆] : Concentration of Total Dissolved Solids, mg/L

°𝐶 : Temperature of condenser water, °𝐶

[𝐶𝑎2+] : Concentration of calcium ions, mg/L

[𝐴𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦] : Alkalinity of condenser water, mg/L

[𝐻𝐶𝑂3−

] : Concentration of bicarbonate ions, mg/L

[𝐶𝑂32−] : Concentration of carbonate ions, mg/L

[𝑂𝐻−] : Concentration of bicarbonate ions, mg/L

[𝐶𝑙−] : Concentration of chloride ions, mg/L

[𝑆𝑂42−] : Concentration of sulphate ions, mg/L

LSI takes the difference between the pH and the saturation pH of the condenser water to determine the potential

of scaling but does not giving insights on how much scale is expected to form [11], which is why this index is

commonly used in combination of other indices such as the RSI to accurately describe the scaling potential of the

given condenser water.

In the RSI, the saturation term is doubled to increase the sensitivity of the index to the saturation pH of calcium

carbonate in the water sample, which can approximate the tendency of precipitation of calcium carbonate. RSI is

proven to be more accurate and sensitive than LSI as proven by Hoseinzadeh et al. [12] where RSI yielded a smaller

percentage error of corrosion potential of 5.5% when compared to LSI with 18.1%.

PSI considers the equilibrium pH instead of the actual pH, which minimizes the effect of buffering agents such as

caustic and ammonia that can result in inaccurate conclusion of scaling tendency calculated by LSI and RSI [13]. All

indices are calculated and the interpretations of the condenser water are based on Table 2.

Chiller Temperature Difference Analysis

The chiller efficiency can be measured from the temperature difference of the chilled water that enters and leaves

the chiller. The operational load of the chiller changes with respect to the demand for cold air by the occupants of the

buildings, which is also dependent on the duration of the day.

Operational load refers to the demand of cooling required by the building. For instance, in the morning with lesser

occupants in a building, the cooling demand is lesser than when in the afternoon with more occupants.

Due to these changes, the temperature difference readings are taken consistently biweekly on site with the sampling

schedule at the specified time as shown below:

System A: 11.00 A.M. – 11.30 A.M.

System B: 12.00 P.M. – 12.30 P.M.

System C: 10.00 A.M. – 10.30 A.M.

System D: 2.30 P.M. – 3.00 P.M.

The readings obtained are plotted in a line graph to monitor the trends of the temperature differences of the systems

investigated over the study period to investigate the impact of the operational parameters of condenser water

characterized with the chiller efficiency.

Environmental Impact Analysis

Quantification of environmental impact by the HVAC systems can be done through lifecycle assessment (LCA)

from cradle to grave [6]. This research only focuses on the environmental impact of HVAC systems during the

operational stage. According to the inventory analysis by Chen et al. [14], the most significant environmental impact

during the operational stage of the HVAC systems is due to the electricity consumption.

According to the local energy provider, Tenaga Nasional Berhad (TNB), the emission factor per kWh of power

produced is 0.55 kg CO2 e/kWh [15]. From this information, the environmental impact analysis for all systems of

condenser water treatments is carried out by evaluating the annual equivalent carbon dioxide (CO2) released per

cooling capacity which can be calculated by multiplying the emission factor with the annual power consumption by

each system investigated.

The assumptions made for the calculation of environmental impact analysis include:

1. Chiller as the major power consumer in the HVAC system.

2. 80% average motor operating load.

3. Chiller is operational for 12 hours per day.

4. Chiller is operational for 260 days per year.

The chiller power consumption is calculated by considering of the rated power input and the total number of

chillers present at the HVAC systems.

For comparison of the environmental impact between the systems to be possible, the annual CO2 emission

calculated must be divided by the respective system capacities.

During the operational stage, the biocide and descalant used by system D in the control of scaling, corrosion and

microbial activity control may have environmental impacts which are not considered while calculating for the annual

emission of carbon dioxide equivalent.

However, the SDS for the chemicals used by system D will be analyzed to check for any environmental impacts

that the chemicals may have.

RESULTS AND DISCUSSIONS

Efficiency Analysis

The efficiency analysis includes the characterization of condenser water samples, the scaling and corrosion

prediction analysis and the chiller performance analysis.

Characterization of Condenser Water Samples

(a) (b)

(c) (d)

(e) (f)

FIGURE 2: Results from characterization of condenser water samples for (a) pH (b) alkalinity (c) chloride content (d) water

hardness (e) water conductivity and (f) TDS.

The red lines in Figure 2(a), (b), (e) and (f) show the limit of the respective operating parameters in accordance to

JRA-GL-02-1994. Figure 2(c) and (d) does not have red lines because the operating limits are out of range from the

chart. The limits for chloride content and water hardness are 200 mg/L Cl- and 600 mg/L CaCO3 respectively.

pH and Alkalinity

From Figure 2(a) and (b), all systems are by complying the standards except for sampling trial 1 system C and

sampling trial 4 system A. The exception of these two cases can be explained.

Firstly, for sampling trial 1 system C, it is reported that there is maintenance conducted not long before the

sampling of condenser water at system C. This causes residual impurities to be within the condenser water line that

contributes to the high readings.

On the other hand, for sampling trial 4 system A, it is reported that the sand filter used on site was offline for

maintenance for the week where sampling of condenser water is conducted. During this week, only one sand filter

was online and it is insufficient to maintain condenser water quality. This immediately resulted in the spike of reading

for all operating parameters except chloride content.

Chloride Content and Water Hardness

From Figure 2(c) and (d), it is seen that all systems are operating well below the standards. However, the most

significant reading found is on sampling trial 4 system A. The reason of the high readings is explained previously due

to the maintenance of the sand filter on site.

It is also worth noticing that the readings taken in system D are generally lower and more consistent when

compared to the non-chemical treatment systems for chloride content, water hardness, conductivity and TDS. At the

same time, the non-chemical treatment systems can be said that it has lesser consistency and that the readings are

generally higher than the chemical treatment system.

Water Conductivity and TDS

From Figure 2(e) and (f), it is seen that all systems generally operate below the standards. The spike of reading for

sampling trial 4 system A is explained earlier as the maintenance of sand filter on site. However, it is also worth

mentioning that system B operates near the standards for water conductivity after the first sampling trial.

This is due to the faulty TDS sensor on site that resulted in insufficient bleeding of condenser water which leads

to the high readings of both conductivity and TDS content from sampling trail 2 to sampling trial 5. It is known that

the faulty TDS sensor was not replaced.

Similar to the chloride content and water hardness, system D generally has readings that are lower and more

consistent when compared to systems A, B and C.

System A, B and C showed <0.03 mg/L Fe for the iron test but system D has readings shown as tabulated in Table

3. The standards set by JRA-GL-02-1994 for iron content is up to 1.0 mg/L Fe.

TABLE 3: Tabulation of results for iron content for system D.

Sampling

Trials

Iron Content for System D (mg/L Fe)

1 2 3 Average

1 0.20 0.19 0.18 0.19

2 0.16 0.16 0.20 0.17

3 0.16 0.16 0.16 0.16

4 0.08 0.08 0.09 0.08

5 0.09 0.06 0.07 0.07

The iron content in condenser water samples for systems A, B and C are consistently below 0.03 mg/L whilst

system D shows average readings of iron content ranging from 0.07 mg/L to 0.19 mg/L. Since that the industrial

standard is set at 1.0 mg/L, it can be concluded that all systems operate below the standards for iron test.

Although that the chemical treatment system is capable of controlling the iron content below the industrial

standards, the non-chemical treatment systems are more effective than the chemical treatment system in controlling

iron content as these systems successfully control the iron content to be consistently below 0.03 mg/L.

Table 4 shows the results obtained for the microbiological proliferation test.

TABLE 4: Tabulation of results for microbiological proliferation.

Factors System A System B System C System D

HPC (CFU/mL) 4.9×103 4.0×102 29.0 7.7×103

Legionella sp. (CFU/mL) <10 <10 <10 <10

The industrial standards for the control of microbial activity is set at 10,000 CFU/mL for HPC and <100 CFU/mL

for Legionella sp. concentration. According to Table 4, it is seen that all systems operate below the industrial standards.

However, it is worth noting that system D has the highest reading in terms of HPC which suggests that it is less

effective in controlling microbial activity when compared to systems A, B and C.

The gap between system C and the rest of the system can be justified that there is scheduled cleaning of cooling

tower on site not long before the sampling trial. This reduced all readings to a minimal level, as evidently seen from

Figure 2 and Table 4.

However, even without the cleaning of cooling tower, it is predicted that the readings for the microbial activity for

system C will be approximately the same as systems A and B. This prediction is based on the comparison of operating

parameters of system C with other systems as seen in Figure 2 where system C generally yields lower readings when

compared to systems A and B.

For the ANOVA single factor test, the values of F calculated for pH, water alkalinity, chloride content, water

hardness, water conductivity and TDS content are 2.0406, 1.8651, 0.3707, 0.3298, 0.3785, 0.3789 respectively. These

values are calculated for all samples and all sampling trials. For a significance level of p<0.05, the critical F value is

evaluated at 3.0556, which is higher than all F values calculated. Therefore, the conclusion can be made that the null

hypothesis is accepted, which means that the batch to batch variations are insignificant. Although that there were

significant variations during the sampling trials such as the cleaning and maintenance of cooling towers, from a

statistical point of view, these variations are insignificant.

Analysis and Prediction of Scaling and Corrosion

Calculations and implications of the LSI, RSI and PSI are tabulated in Table 5 as shown. From Table 5, the LSI

readings generally suggest that the condenser water samples collected from all samples are super saturated while the

RSI readings generally suggest that they are either saturated or unsaturated with calcium ions, which is contradictory.

TABLE 5: Tabulation of calculations and implications of LSI, RSI and PSI.

Index Implication

Samples LSI RSI PSI LSI RSI PSI

Trial 1

A 0.02 7.51 7.85 SSa USa SDa

B 0.51 6.94 7.47 SS Sa SD

C 0.70 6.65 7.13 SS S SD

D 0.18 7.28 7.61 SS US SD

Trial 2

A 0.61 6.68 7.19 SS S SD

B 0.78 6.57 7.37 SS S SD

C 0.67 6.76 7.42 SS S SD

D 0.44 7.05 7.55 SS US SD

Trial 3

A 0.48 6.94 7.67 SS S SD

B 0.52 7.03 8.17 SS US SD

C 0.50 6.98 7.63 SS S SD

D 0.65 6.89 7.95 SS S SD

Trial 4

A 1.00 5.94 6.33 SS SS Sta

B 0.72 6.59 7.26 SS S SD

C 0.33 7.31 7.99 SS US SD

D 0.33 7.32 8.15 SS US SD

Trial 5

A 0.75 6.47 7.05 SS S SD

B 0.72 6.45 6.92 SS S St

C 0.49 6.84 7.24 SS S SD

D -0.14 7.72 8.0 US US SD aSS: Super Saturated; US: Under Saturated; SD: Scale Dissolves; S: Saturated; St: Stable

Contradictory results between LSI and RSI are also published in literature by Kim et al. [16], Al-Huseini [17],

Shams et al. [18] and Shankar [19]. The contradictory results are often caused by the actual pH values of the water

samples. By using pH to compare between Table 5 and Figure 2(a), it can be seen that water samples with pH of less

than 7.8 generally yields ‘US’ result RSI while having ‘SS’ for LSI. Because of the relatively low pH, both LSI and

RSI values are at the borderlines of the descriptions of water conditions as shown in Table 2. In these cases, the water

conditions need to be verified by using PSI to check for the scaling condition.

For condenser water samples that have pH values of more than 7.8, the LSI remains to have ‘SS’ and that the RSI

gives ‘S’. From the two indices, it is agreeable that calcium ions in these water samples are saturated. However, the

degree of saturation remains unknown due to the contradicting results from LSI and RSI. Hoseinzadeh et al. [12]

proved that RSI is more accurate when compared to LSI as the sensitivity to the saturation pH of calcium carbonate

is increased. This implies that RSI is a more reliable index to indicate the scaling potential due to the degree of

saturation of the water samples. Shankar [19] supported this statement by justifying that the range of water condition

for the LSI is more limited as a solid zero is needed to show that the water is saturated as shown in Table 2. On the

other hand, RSI provides a range of 6 to 7 for a saturation zone which allows more flexibility in terms of the water

condition. Therefore, in these cases where the pH values of the condenser water samples are more than 7.8, the water

condition is concluded from RSI instead of LSI.

As LSI and RSI only describe the tendencies of the scale formation in water bodies without giving insights on how

much scale is expected, PSI must be used in addition to LSI and RSI to confirm the condenser water conditions. The

PSI readings show that all condenser waters are likely to dissolve scale except for sampling trial 4 system A and

sampling trial 5 system B. This shows that the condenser water samples do not have scale formation tendencies. The

stable condition of condenser water for sampling trial 4 system A is caused by the maintenance of sand filter on site.

The stable condition of condenser water for sampling trail 5 system B is caused by the faulty TDS sensor on site that

leads to insufficient bleeding of condenser water.

In summary, although that the condenser water samples are saturated with calcium ions as proven by LSI and RSI,

the scale formations in the systems investigated are unlikely as the scales will remain dissolved in the condenser water

as proven by PSI.

Chiller Performance Analysis

Figure 3 shows the graph of temperature difference of chilled water for systems A to D across the study period.

As mentioned, the timings of the registration of readings for the chilled water temperatures from each system are

different but consistent. Therefore, instead of comparing system by system, the consistencies of each system in terms

of the temperature difference of chilled water are investigated.

From Figure 3, it is seen that the temperature differences for systems A, B and D are consistently in the range of

3.0°C to 5.0°C. For system C, the inconsistent temperature difference readings are due to the different operating loads

of the chiller on site.

For systems A, B and D, the consistent temperature differences of chilled water are the results of the operation of

condenser water that is generally below the industrial standards. Because of this, operational issues such as corrosion,

scaling and microbiological proliferation are prevented which allows optimal operation of the HVAC systems in

system A, B and D.

For system C, the fluctuations in the temperature differences between the chilled water in the chiller does not

necessarily mean that the operation of condenser water exceeds the industrial standards. This is further reinforced by

the excellent results obtained by system C in the characterization of condenser water in Figure 2.

FIGURE 3: Chilled water temperature difference in chillers.

Therefore, the fluctuations of temperature difference between the chilled water in the chiller in system C is not

caused by operational issues of condenser water such as corrosion, scaling and microbiological proliferation. The

fluctuation in the temperature difference of chilled water is however due to the different chiller operating loads.

In system C, for sampling trials of 1, 2 and 5, the chiller is running at operating loads of 103%, 100% and 98%

respectively, while for sampling trials of 3 and 4, the chiller is running at operating loads of 58% and 51%, although

that the readings are taken consistently between 10.00 A.M. to 10.30 A.M.

It is clear that the temperature difference fluctuations of system C is caused by the operational load of the chiller.

Therefore, based on the results obtained from the characterization of condenser water samples, it can be concluded

that the HVAC system in system C operates optimally without issues such as corrosion, scaling and microbiological

proliferation.

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

0 1 2 3 4 5 6

Chil

led

Wat

er T

emp

erat

ure

Dif

fere

nce

,

°C

Sampling Trials

Chilled Water Temperature Difference

System A

System B

System C

System D

Environmental Impact Analysis

Table 6 shows the tabulation of information required for the calculation. The rated power inputs for the chillers in

system C are unobtainable. Thus, the calculation of the power input to the chillers in system C is evaluated by using

the chiller efficiency information as shown in Table 6.

TABLE 5: Tabulation of system specifications for environmental impact calculations.

System Number of Chillers Power Input (kW) Chiller Efficiency

(kW/RT)

Cooling Capacity

(RT)

A 3 342 0.670 2700

B 3 310 0.670 1650

C 7 NAa 0.175 8000

D 4 253 NA 1600 aNA: Not Applicable (For information that are unobtainable)

By considering the assumptions listed out for the calculations, the annual electricity consumption of the chillers

for each system can be evaluated, followed by the annual equivalent emission of CO2 per RT. Table 7 shows the

tabulation of the results calculated for the environmental impact analysis.

TABLE 6: Tabulation of results for environmental impact analysis.

System

Annual

Electricity Consumption

(kW/year)

Annual Equivalent

CO2 Emission

(kg CO2 e/year)

Annual Emission per

Cooling Capacity

(kg CO2 e/year RT)

A 2,560,896 1,408,493 521.66

B 2,321,280 1,276,704 773.76

C 3,494,400 1,921,920 240.24

D 2,525,952 1,389,274 868.30

As observed in Table 7, the annual emission per cooling capacity for system D is the highest at 868.30 kg CO2

e/year RT when compared to the non-chemical treatment systems of A to C. This indicates that the non-chemical

treatment systems for condenser water in the HVAC systems causes lesser environmental impact (in terms of CO2

emission) when compared to the chemical treatment system.

From Tables 6 and 7, it is seen that the chiller in system D consumes only 253 kW, but when the comparison of

the same cooling capacity is made, system D yields the highest annual emission per cooling capacity. This shows that

the chillers in system D are not as efficient as the chillers in system A, B and C because that it requires more energy

to produce 1 RT of cooling capacity. Therefore, from the environmental impact analysis, it can be seen that the

chemical treatment system not only produces more CO2 equivalent annually per RT, it is also shown to have the least

efficient chillers when compared to the non-chemical treatment systems.

In addition, there are three (3) chemicals used in the control of scaling, corrosion and microbial activity control in

system D. The three chemicals are labelled as CL-320, CL-650 and CL-653.

CL-320 is an organo-phosphonate based corrosion and scale inhibitor that has the combination of calcium

carbonate inhibitor, dispersant, dual phosphonate and yellow metal inhibitor to control corrosion of mild steel, copper

and admiralty brass. This chemical also minimizes hardness salt formation in alkaline cooling water.

CL-650 is a non-oxidizing blend of quaternary ammonium compounds-based biocide that functions to control the

activity of bacteria, fungi and algae in open re-circulating cooling water systems. It also contains dispersing agents

that ensure good distribution throughout the system and efficient penetration of slime masses.

CL-653 is a non-oxidizing mixture of isothiazolin based biocide that is designed specifically for the control of

bacteria, fungi and algae in open re-circulating cooling water system. This product has low foaming tendency and is

compatible with most treatment chemicals.

According to the SDS of the chemicals, CL-320 has no environmental impact during the usage, but CL-650 and

CL-653 have reported to have category 3 acute aquatic hazard, which means that short term exposure (15 minutes) of

10 mg/L to 100 mg/L of the chemicals can cause damage to aquatic environment and subsequently to the aquatic

organisms. Thus, this concludes that the non-chemical treatment systems might cause lesser environmental impact

when compared to the chemical treatment system.

CONCLUSION

In conclusion, the efficiency analysis proves that the chemical and non-chemical treatment systems are capable in

maintaining operating parameters such as the pH, water alkalinity, iron content, chloride content, TDS, water electrical

conductivity and water hardness by complying the industrial standards such as the JRA-GL-02-1994. In addition to

that, the calculations of LSI, RSI and PSI concluded that all condenser water samples are saturated with calcium ions,

but scale formations are unlikely as the scales are likely to remain dissolved in the condenser water. Because of the

adherent to the industrial standards, the chillers in all systems are able to run optimally with consistent temperature

difference between the chilled water taken at consistent timings.

Secondly, the environmental impact analysis concluded that the non-chemical treatment systems have lesser

environmental impact compared to the chemical treatment system with an annual equivalent emission of CO2 of

868.30 kg CO2 e/year RT which is the most among the systems investigated. Due to the chemicals used, the chemical

treatment system might have more negative environmental impact when compared to the non-chemical treatment

systems.

ACKNOWLEDGMENT

The authors would like to express gratitude to panels from Green Building Index, EnGreen, Greneco and Taylor’s

University for the support and cooperation throughout the research project.

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