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JAYAPRAKASH SATHTHASIVAM,GARY TANG,KIM CHOON NG 대한설비공학회 2010 International Journal Of Air-Conditioning and Refr Vol.18 No.1
The application of Fault Detection and Diagnosis (FDD) could play a key role in operating chillers at optimum e±ciency. As air-conditioning consumes a significant proportion (approximately 30% to 50%) of the total power consumption of a commercial building, an e®ective FDD tool is very much required for a reliable and economic chiller operation. In this paper, the renowned Simple Thermodynamic Model, STM (also known as Gordon and Ng Universal Chiller Model) was utilized to detect and diagnose some of the common faults in centrifugal chillers. Based on the readily available, nonintrusive, steady state measurements extracted from the on-site chillers, the STM model was regressed to obtain two physically meaningful coe±cients, namely, Thermal Resistance and Internal Entropy Generation. These information-rich coe±- cients were then analyzed to evaluate the performances and the conditions of the chillers. Despite the large and yet complex on-site chiller operations, equipped with built-in heat recovery, such as economizer and intricate control mechanisms, the predictive and diagnostic capabilities of STM in detecting chiller faults has been successfully tested and evaluated based on the data collected from on-site centrifugal chillers. Faults like condenser fouling and reduction in condenser cooling water flow rate were succinctly captured by the STM model.
Saththasivam, Jayaprakash,Tang, Gaty,Ng, Kim Choog The Society of Air-Conditioning and Refrigerating 2010 International Journal Of Air-Conditioning and Refr Vol.18 No.1
The application of Fault Detection and Diagnosis (FDD) could play a key role in operating chillers at optimum efficiency. As air-conditioning consumes a significant proportion (approximately 30% to 50%) of the total power consumption of a commercial building, an effective FDD tool is very much required for a reliable and economic chiller operation. In this paper, the renowned Simple Thermodynamic Model, STM (also known as Gordon and Ng Universal Chiller Model) was utilized to detect and diagnose some of the common faults in centrifugal chillers. Based on the readily available, nonintrusive, steady state measurements extracted from the on-site chillers, the STM model was regressed to obtain two physically meaningful coefficients, namely, Thermal Resistance and Internal Entropy Generation. These information-rich coefficients were then analyzed to evaluate the performances and the conditions of the chillers. Despite the large and yet complex on-site chiller operations, equipped with built-in heat recovery, such as economizer and intricate control mechanisms, the predictive and diagnostic capabilities of STM in detecting chiller faults has been successfully tested and evaluated based on the data collected from on-site centrifugal chillers. Faults like condenser fouling and reduction in condenser cooling water flow rate were succinctly captured by the STM model.
Al-Bloushi Mohammed,Saththasivam Jayaprakash,Jeong Sanghyun,Al-Refaie Abdullah,Raju S. Arun Kumar,Kim Choon NG,Amy L. Gary,Leiknes TorOve 대한환경공학회 2021 Environmental Engineering Research Vol.26 No.6
Biofouling in the open recirculating cooling water systems may cause biological corrosion, which can reduce the performance, increase the energy consumption and lower heat exchange resulting in reduced efficiency of the cooling tower (CT). Seawater CTs are prone to bio-fouled due to the presences of organic and inorganic compounds which act as nourishment for various microorganisms like (algae, fungi, and bacteria) for their growth under certain environmental conditions. The most commonly being used method to control the biofouling in CT is by addition of biocides such as chlorination. In this study, diatom and green algae were added to the CT basin and its viability was monitored in the recirculating cooling seawater loop as well as in the CT basin. Three different types of oxidizing biocides, namely chlorine, chlorine dioxide (Chlorine dioxide) and ozone, were tested by continuous addition in pilot-scale seawater CTs and it was operated continuously for 60 d. The results showed that all biocides were effective in keeping the biological growth to the minimum regardless of algal addition. Amongst the biocides, ozone could reduce 99% of total live cells of bacteria and algae, followed by Chlorine dioxide at 97%, while the conventional chlorine showed only 89% reduction in the bioactivities.
Al-Bloushi Mohammed,Saththasivam Jayaprakash,Jeong Sanghyun,Al-Refaie Abdullah,Raju S. Arun Kumar1,Choon NG Kim,Amy L. Gary,Leiknes TorOve 대한환경공학회 2021 Environmental Engineering Research Vol.26 No.6
Biofouling in the open recirculating cooling water systems may cause biological corrosion, which can reduce the performance, increase the energy consumption and lower heat exchange resulting in reduced efficiency of the cooling tower (CT). Seawater CTs are prone to bio-fouled due to the presences of organic and inorganic compounds which act as nourishment for various microorganisms like (algae, fungi, and bacteria) for their growth under certain environmental conditions. The most commonly being used method to control the biofouling in CT is by addition of biocides such as chlorination. In this study, diatom and green algae were added to the CT basin and its viability was monitored in the recirculating cooling seawater loop as well as in the CT basin. Three different types of oxidizing biocides, namely chlorine, chlorine dioxide (Chlorine dioxide) and ozone, were tested by continuous addition in pilot-scale seawater CTs and it was operated continuously for 60 d. The results showed that all biocides were effective in keeping the biological growth to the minimum regardless of algal addition. Amongst the biocides, ozone could reduce 99% of total live cells of bacteria and algae, followed by Chlorine dioxide at 97%, while the conventional chlorine showed only 89% reduction in the bioactivities.
Mohammed Al-Bloushi,Jayaprakash Saththasivam,Sari Al-Sayeghc,정상현,Kim Choon Ng,Gary L. Amy,TorOve Leiknes 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.59 No.-
Biofouling can significantly hamper the efficiency of seawater cooling towers. The aim of this study was to investigate the effectiveness of alternative oxidants (i.e. ozone (O3) and chlorine dioxide (ClO2)) comparing with commonly being used chlorine in biofouling control. Effects of cycle of concentration, temperature and oxidant dosage along with residual decay and kinetics were studied. Even at lower oxidant dosage (total residual oxidant equivalent = 0.1 mg/l Cl2), ClO2 showed a better disinfection effect compared to chlorine and O3. Results of bench-scale studies will be helpful in the selection of appropriate oxidant for seawater cooling tower operation.