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Review on Modeling of Vapor Compression Chillers: District Cooling Perspective
Kadam Sambhaji T.,Hassan Ibrahim,Rahman Mohammad Azizur,Papadopoulos Athanasios I.,Seferlis Panos 대한설비공학회 2020 International Journal Of Air-Conditioning and Refr Vol.28 No.2
Energy consumption and its associated consequences can be reduced by implementing district cooling strategies that supply low temperature water to a wide range of end users through chillers and distribution networks. Adequate understanding, performance prediction and further optimization of vapor compression chillers used widely in district cooling plants have been a subject of intense research through model-based approaches. In this context, we perform an extensive review of different modeling techniques used for predicting steady-state or dynamic performance of vapor compression liquid chillers. The explored modeling techniques include physical and empirical models. Different physical models used for vapor compression chillers, based on physics laws, are discussed in detail. Furthermore, empirical models (based on artificial neural networks, regression analysis) are elaborated along with their advantages and drawbacks. The physical models can depict both steady- and unsteady-state performance of the vapor compression chiller; however, their accuracy and physical realism can be enhanced by considering the geometrical arrangement of the condenser and evaporator and validating them for various ecofriendly refrigerants and large system size (i.e., cooling capacity). Apparently, empirical models are easy to develop but do not provide the necessary physical realism of the process of vapor compression chiller. It is further observed that DC plants/networks have been modeled from the point of view of optimization or integration but no efforts have been made to model the chillers with multiple VCR cycles. The development of such models will facilitate to optimize the DC plant and provide improved control strategies for effective and efficient operation.
The analysis of groundwater table variations in Sylhet region, Bangladesh
Abu Zafor,Jahir Bin Alam,Azizur Rahman,Mohammad Nurul Amin 대한환경공학회 2017 Environmental Engineering Research Vol.22 No.4
The trend analysis of the study was acquired by selecting multiyear monthly groundwater table data and monitors the wells in each sub-district under the study area. The intention of this research was to analyze the outcome of the non-parametric Mann-Kendall test at greater than the significance level which is 95% of groundwater level in Sylhet. The aptitude is effective at two conjunctures where the confidence bounds are 95% and it meets the estimate line of Sen’s. To calculate and assess the spatial differences in the inanition of groundwater table, geostatistical methods was applied based on data from 27 groundwater wells during the period from January 1975 to December 2011 which were obtained from a secondary source, Bangladesh Water Development Board. The geographic information system was used to assess the spatial change in order to find the level of groundwater. Cross-validation errors were found within an advisable level in estimating the groundwater depth with different interpolation models of ordinary kriging methods. Finally, surface maps were generated with the best-fitted model. The southeast region was found highly vulnerable from groundwater level point of view. Northern region was detected highest hazard prone area for diverge groundwater using kriging method.
Shoaib Shadab Iqbal,Md. Mujahid,Sayed Mohammad Kashif,Mohammad Khalid,Badruddeen,Muhammad Arif,Paramdeep Bagga,Juber Akhtar,Md. Azizur Rahman 한국한의학연구원 2016 Integrative Medicine Research Vol.5 No.4
Background Traditional systems of medicine use herbal drugs for hepatoprotection. Thus, the study was designed to evaluate the hepatoprotective and antioxidant effects of Spondias pinnata bark extracts against ethanol-induced liver injury in Wistar rats. Methods Group I animals were treated with 1 mL/kg 0.3% carboxymethyl cellulose and Group II with 12 mL/kg 50% ethanol for 8 consecutive days. Groups III–VII animals were first treated with 400 mg/kg petroleum ether extract, chloroform extract, acetone extract (AE), ethanol extract (EE), and 100 mg/kg silymarin, and then 12 mL/kg 50% ethanol orally after 2 hours pretreatment each day for 8 consecutive days. Six hours after the last dose, blood was withdrawn. The hepatoprotective activity was assessed by several biochemical and antioxidant parameters. It was accomplished by the histopathology and DNA fragmentation study of liver tissues. Results Treatment with S. pinnata extracts, mainly AE and EE significantly (p < 0.05–0.01) and dose-dependently prevented the ethanol-induced increase in serum levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, lactate dehydrogenase, cholesterol, bilirubin, and malondialdehyde, and decrease in reduced glutathione, catalase, superoxide dismutase, and albumin. They also attenuated the ethanol-induced DNA damage. Hepatoprotective potential of the extract was less than that of standard drug silymarin. Results of the study were well supported by the histopathological observations. Conclusion S. pinnata extracts AE and EE possess a potent hepatoprotective effect against ethanol-induced liver injury in Wistar rats, and protect them from hepatotoxicity by prevention of ethanol-induced oxidative stress, DNA-damage and altered biochemical markers.