Numerical Optimization of Double Tube GHE for Ground Source Heat Pump
Md. Hasan Ali,
Akio Miyara,
Keishi Kariya
Issue:
Volume 6, Issue 5, September 2017
Pages:
64-75
Received:
29 July 2017
Accepted:
7 August 2017
Published:
23 August 2017
Abstract: In this paper, a two-dimensional axisymmetric numerical simulation model was developed for optimization of double (coaxial) tube vertical ground heat exchangers (GHEs) in cooling mode. Details of the heat transfer rates and pressure drops for each model are presented and analyzed. The results of the numerical study of optimization of double tube vertical GHEs have been done by considering heat transfer rates and pressure drops. The effect of different inlet and outlet tube diameters, and mass flow rates were numerically investigated. Effect of the different materials on heat transfer and longtime operation also discussed. The double tube vertical GHEs are more effective in laminar flow condition considering balance between heat transfer and pressure drop. The results indicate that since in laminar flow condition, pressure drop is not significantly high, it is possible to reduce the inlet and outlet diameter of double tube GHEs if double tube GHEs operate in laminar flow condition. The heat transfer rate decreased only 17% but diameter of the inlet tube can be reduced from 130 mm to 40 mm with fixed outlet diameter 20 mm. Heat transfer rate can also be enhanced by reducing the outlet tube diameter for a fixed inlet tube diameter. Long time operation suggested the possibility of installation of multiple double tube GHE at 2.0 m apart.
Abstract: In this paper, a two-dimensional axisymmetric numerical simulation model was developed for optimization of double (coaxial) tube vertical ground heat exchangers (GHEs) in cooling mode. Details of the heat transfer rates and pressure drops for each model are presented and analyzed. The results of the numerical study of optimization of double tube ve...
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Examining Whether Smart Meters Have Been Used Smartly: A Case Study of Residential Electricity Customers in Vermont
Qingbin Wang,
Samantha Lewandowski
Issue:
Volume 6, Issue 5, September 2017
Pages:
76-83
Received:
10 July 2017
Accepted:
26 July 2017
Published:
16 October 2017
Abstract: Approximately 92% of electricity meters in Vermont, and more than 40% across the United States, have been replaced with smart meters due to their potential to improve grid efficiency and reduce electricity costs, but there is very limited information on whether smart meters are benefitting or being efficiently used by electricity customers. In this study, quantitative analysis of primary data from statewide surveys in Vermont is used to address several questions on consumer behavior and opinions towards smart meters. The empirical results indicate that less than 50% of the surveyed customers reported having a smart meter and, for those who did report having a smart meter, less than 20% of them thought that the smart meter had reduced their electricity use. Also, there were significant differences in demographic factors and concerns about the potential impacts of smart meters on health and privacy between those who reported having a smart meter and those who did not. Furthermore, the respondents did report some interest in receiving additional information on smart meters. In all, these findings suggest that there are a number of ways utility companies and other educational entities, such as Extension, can improve the efficacy of smart meter utilization.
Abstract: Approximately 92% of electricity meters in Vermont, and more than 40% across the United States, have been replaced with smart meters due to their potential to improve grid efficiency and reduce electricity costs, but there is very limited information on whether smart meters are benefitting or being efficiently used by electricity customers. In this...
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Anaerobic Digestion of Slaughterhouse Wastewater for Methane Recovery and Treatability
Zemene Worku,
Seyoum Leta
Issue:
Volume 6, Issue 5, September 2017
Pages:
84-92
Received:
9 September 2017
Accepted:
22 September 2017
Published:
30 October 2017
Abstract: The objective of this investigation was to optimize and evaluate the bioenergy production potential and COD removal efficiency of a semi-continuous anaerobic digester from slaughterhouse wastewater. The performance of the pilot scale anaerobic digester was evaluated at the OLRs of 0.32, 0.51, 1.16 and 2.31 kg m−3day−1 under mesophilic environmental condition (29.6±1.40°C). The COD removal efficiencies and methane yield in the pilot scale digester were in the range of 43.39 to 84.54% and 0.09±0.03 to 0.22±0.02 m3/kg COD removed, respectively with the maximum volumetric methane production (0.93±0.17m3/day) was achieved at the OLR of1.16 kg m−3 d−1 corresponding to an optimum methane yield of 0.20 m3 CH4 per kg COD removed. Generally, the results of this study showed that anaerobic digester is efficient on generating bioenergy while treating high strength wastewater such as slaughterhouse wastewater. Hence, a full scale anaerobic digester should be developed and used to treat the wastewater generated in the slaughterhouse industries in Ethiopia where almost all the slaughterhouses discharge their wastewater to the nearby streams without prior treatment.
Abstract: The objective of this investigation was to optimize and evaluate the bioenergy production potential and COD removal efficiency of a semi-continuous anaerobic digester from slaughterhouse wastewater. The performance of the pilot scale anaerobic digester was evaluated at the OLRs of 0.32, 0.51, 1.16 and 2.31 kg m−3day−1 under mesophilic environmental...
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