The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
R Z Wang - One of the best experts on this subject based on the ideXlab platform.
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Recent progress on desiccant materials for solid desiccant Cooling Systems
Energy, 2014Co-Authors: Xin Qian Zheng, T.s. Ge, R Z WangAbstract:SDC (Solid desiccant Cooling) Systems have gained increasing interest as an alternative air conditioning technology. Performance of desiccant plays a crucial role in overall performance of the whole system, especially in terms of dehumidification and regeneration capacity. It is desirable to explore desiccant possessing high adsorption capacity and good regeneration ability. Thus, this review summarizes recent researches and developments on novel solid desiccant materials that can be adopted in SDC Systems. The materials include composite desiccants, nanoporous inorganic materials and polymeric desiccants. Adsorption isotherms are concluded and compared. Regeneration ability is also considered for full use of low grade thermal energy. Results show that by proper selection of host matrix and immersed salts, composite desiccants have improved capacity of dehumidification and regeneration. Besides, a good balance can be reached between regeneration and adsorption capacity by tailoring textural properties of nanoporous inorganic materials. For polymeric desiccants, especially MIL type (materials of Institute Lavoisier Frameworks), further progress in adsorptive dehumidification will be anticipated. Though some novel materials approach requirements for SDC Systems, no material currently available can perfectly satisfy all the required demands. In this case, more intensive researches in the field of development and evaluation of advanced materials are still required.
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a review for research and new design options of solar absorption Cooling Systems
Renewable & Sustainable Energy Reviews, 2011Co-Authors: X Q Zhai, Ming Qu, Yue Li, R Z WangAbstract:Solar Cooling technology is environmentally friendly and contributes to a significant decrease of the CO2 emissions which cause the green house effect. Currently, most of the solar Cooling Systems commonly used are the hot water driven lithium bromide absorption chillers. According to the operating temperature range of driving thermal source, single-effect LiBr/H2O absorption chillers have the advantage of being powered by ordinary flat-plate or evacuated tubular solar collectors available in the market. In this paper, besides the review of the existing theoretical and experimental investigations of solar single-effect absorption Cooling Systems, some new design options with regard to solar collectors, auxiliary energy Systems and Cooling modes were introduced. And then, other main types of solar absorption Cooling Systems based on double-effect, half-effect and two-stage absorption chillers were summarized. For buildings with high amounts of Cooling load and limited installation area, solar-powered double-effect absorption Cooling Systems may be considered on condition that the direct irradiation is high enough. Half-effect absorption chillers and two-stage absorption chillers seem to be more suitable for air-cooled solar absorption Cooling Systems in hot and dry regions which are short of water. It is highly recommended to study the standardised design guidelines according to different areas for the purpose of widespread applications of solar Cooling Systems.
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a review for absorbtion and adsorbtion solar Cooling Systems in china
Renewable & Sustainable Energy Reviews, 2009Co-Authors: X Q Zhai, R Z WangAbstract:In the past decades, solar water collectors were installed for the main purpose of preheating domestic hot water or to cover a fraction of the space heating demand in China. However, solar Cooling Systems were constructed just for demonstration purposes. Since the building of the first solar-powered absorption Cooling system in Shenzhen in 1987, there have been over 10 additional solar Cooling demonstration projects constructed. In this paper, the most representative five projects including both absorption and adsorption Cooling Systems are introduced and summarized. From the demonstrations, solar absorption Cooling Systems have been shown to be more suitable for large building air-conditioning Systems. Comparatively, solar adsorption Cooling Systems are more promising for small size air-conditioning Systems. In order to attain high utilization ratio, it is highly recommended to design solar-powered integrated energy Systems in public buildings. In addition, highly efficient heat pumps are considered as the most appropriate auxiliary heat sources for solar Cooling Systems, for the purpose of all-weather operation. In the 11th Five year research project (duration 2006-2010), solar Cooling technologies will be further investigated to achieve a breaking through in the integration of solar Cooling Systems with buildings.
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solar sorption Cooling Systems for residential applications options and guidelines
International Journal of Refrigeration-revue Internationale Du Froid, 2009Co-Authors: R Z Wang, T.s. Ge, Congying Chen, Z Q XiongAbstract:Solar powered sorption Cooling Systems have been researched and demonstrated in recent years, which contain adsorption Cooling, absorption Cooling and desiccant Cooling. The various typical Systems with small scale for potential residential applications are discussed and analyzed, in which the working principals, system suitability for solar Cooling, performance, maintenance and economic viability have been discussed in this paper. With such analyses and the available real operation Systems, the detailed options and guidelines of solar Cooling for residential applications are shown.
Radisav D. Vidic - One of the best experts on this subject based on the ideXlab platform.
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Impact of Tertiary Treatment Processes on the Effectiveness of Chloramination for Biological Growth Control in Recirculating Cooling Systems Using Treated Municipal Wastewater
Journal of Environmental Engineering, 2014Co-Authors: Shih-hsiang Chien, Wenshi Liu, David A Dzombak, Radisav D. VidicAbstract:AbstractAdequate biocide addition is the key to control biological growth-related problems in recirculating Cooling Systems of thermoelectric power plants. The use of monochloramine (MCA) as the primary biocide is as effective as the use of free-chlorine in Cooling Systems using secondary-treated municipal wastewater (MWW) as the sole makeup water source. However, severe scaling caused by the secondary effluent necessitates incorporation of an additional treatment of secondary effluent (i.e., tertiary treatment) prior to use as makeup water for recirculating Cooling Systems. In the research reported in this paper, the effectiveness of MCA as a Cooling-system biocide was evaluated for three types of tertiary-treated MWW, as follows: (1) acidification, (2) nitrification and sand filtration, and (3) nitrification, sand filtration, and granular activated-carbon adsorption. The impact of these tertiary treatment processes on chloramination was studied in both laboratory and pilot-scale experiments. For the thi...
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Scaling Control for Heat Exchangers in Recirculating Cooling Systems Using Treated Municipal Wastewater
2014Co-Authors: Wenshi Liu, Shih-hsiang Chien, David A Dzombak, Radisav D. VidicAbstract:Treated municipal wastewater (MWW) is recognized as a viable alternative Cooling water source for power generation. One of the key challenges for the successful use of the effluent from wastewater treatment facilities for Cooling is the potential for significant condenser fouling when this water is concentrated as much as 4–6 times in recirculating Cooling Systems. In this study, two types of treated municipal wastewaters, namely secondary-treated MWW with pH adjustment (MWW_pH) and secondary-treated MWW subjected to nitrification and sand filtration (MWW_NF), were evaluated as the sole source of makeup water for recirculating Cooling Systems in both laboratory and pilot-scale studies. The tests revealed that synthetic MWW_pH had significant crystalline fouling potential on the condenser surfaces when the pH was adjusted at 7.8 and that hydroxyapatite was the main component of the mineral scales formed on condenser surfaces. Addition of antiscalants, e.g., polymaleic acid (PMA), was shown to be effective in fouling mitigation by inhibiting the transformation of amorphous calcium phosphate to hydroxyapatite. In the case of synthetic MWW_NF, significant crystalline fouling was observed at pH 7.2 while bulk precipitation reduced the driving force for crystalline fouling when pH was adjusted to 7.8. Pilot-scale studies with actual MWW revealed that the addition of PMA alone is not sufficient to control scale buildup and that controlling pH at 7.8 is needed to ensure proper operation of the Cooling tower, as predicted by laboratory studies with synthetic wastewater. Alternatively, nitrification and sand filtration would accomplish the same goal without any chemical addition. Overall, this study demonstrated that it is possible to manage crystalline fouling on hot condenser tube surfaces associated with the use of treated municipal wastewater just by pH control and antiscalant addition and that significant additional treatment of municipal wastewater prior to use in recirculating Cooling Systems may not be necessary
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corrosion management in power plant Cooling Systems using tertiary treated municipal wastewater as makeup water
Corrosion Science, 2012Co-Authors: Mahbuboor Rahman Choudhury, Radisav D. Vidic, Mingkai Hsieh, David A DzombakAbstract:Abstract Additional tertiary treatment of secondary-treated municipal wastewater (MWW) is necessary to reduce its scaling potential for use in power plant Cooling Systems. In this study corrosiveness of three tertiary-treated municipal wastewaters (acidified MWW, MWW treated by nitrification–filtration, and MWW treated by nitrification–filtration and granular activated carbon adsorption) towards mild steel, copper, and cupronickel alloys was assessed. pH, ammonia, and organic matter were identified as important corrosion influencing parameter in tertiary-treated municipal wastewater. Corrosiveness of wastewater towards metal alloys increased after tertiary treatments. However, corrosion of mild steel and copper alloys was controlled within acceptable limits using the corrosion inhibitor tolyltriazole.
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control of mineral scale deposition in Cooling Systems using secondary treated municipal wastewater
Water Research, 2011Co-Authors: Mingkai Hsieh, David A Dzombak, Shih-hsiang Chien, Jason D Monnell, Radisav D. VidicAbstract:Secondary-treated municipal wastewater (MWW) is a promising alternative to freshwater as power plant Cooling system makeup water, especially in arid regions. A prominent challenge for the successful use of MWW for Cooling is potentially severe mineral deposition (scaling) on pipe surfaces. In this study, theoretical, laboratory, and field work was conducted to evaluate the mineral deposition potential of MWW and its deposition control strategies under conditions relevant to power plant Cooling Systems. Polymaleic acid (PMA) was found to effectively reduce scale formation when the makeup water was concentrated four times in a recirculating Cooling system. It was the most effective deposition inhibitor of those studied when applied at 10 mg/L dosing level in a synthetic MWW. However, the deposition inhibition by PMA was compromised by free chlorine added for biogrowth control. Ammonia present in the wastewater suppressed the reaction of the free chlorine with PMA through the formation of chloramines. Monochloramine, an alternative to free chlorine, was found to be less reactive with PMA than free chlorine. In pilot tests, scaling control was more challenging due to the occurrence of biofouling even with effective control of suspended bacteria. Phosphorous-based corrosion inhibitors are not appropriate due to their significant loss through precipitation reactions with calcium. Chemical equilibrium modeling helped with interpretation of mineral precipitation behavior but must be used with caution for recirculating Cooling Systems, especially with use of MWW, where kinetic limitations and complex water chemistries often prevail.
David A Dzombak - One of the best experts on this subject based on the ideXlab platform.
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Impact of Tertiary Treatment Processes on the Effectiveness of Chloramination for Biological Growth Control in Recirculating Cooling Systems Using Treated Municipal Wastewater
Journal of Environmental Engineering, 2014Co-Authors: Shih-hsiang Chien, Wenshi Liu, David A Dzombak, Radisav D. VidicAbstract:AbstractAdequate biocide addition is the key to control biological growth-related problems in recirculating Cooling Systems of thermoelectric power plants. The use of monochloramine (MCA) as the primary biocide is as effective as the use of free-chlorine in Cooling Systems using secondary-treated municipal wastewater (MWW) as the sole makeup water source. However, severe scaling caused by the secondary effluent necessitates incorporation of an additional treatment of secondary effluent (i.e., tertiary treatment) prior to use as makeup water for recirculating Cooling Systems. In the research reported in this paper, the effectiveness of MCA as a Cooling-system biocide was evaluated for three types of tertiary-treated MWW, as follows: (1) acidification, (2) nitrification and sand filtration, and (3) nitrification, sand filtration, and granular activated-carbon adsorption. The impact of these tertiary treatment processes on chloramination was studied in both laboratory and pilot-scale experiments. For the thi...
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Scaling Control for Heat Exchangers in Recirculating Cooling Systems Using Treated Municipal Wastewater
2014Co-Authors: Wenshi Liu, Shih-hsiang Chien, David A Dzombak, Radisav D. VidicAbstract:Treated municipal wastewater (MWW) is recognized as a viable alternative Cooling water source for power generation. One of the key challenges for the successful use of the effluent from wastewater treatment facilities for Cooling is the potential for significant condenser fouling when this water is concentrated as much as 4–6 times in recirculating Cooling Systems. In this study, two types of treated municipal wastewaters, namely secondary-treated MWW with pH adjustment (MWW_pH) and secondary-treated MWW subjected to nitrification and sand filtration (MWW_NF), were evaluated as the sole source of makeup water for recirculating Cooling Systems in both laboratory and pilot-scale studies. The tests revealed that synthetic MWW_pH had significant crystalline fouling potential on the condenser surfaces when the pH was adjusted at 7.8 and that hydroxyapatite was the main component of the mineral scales formed on condenser surfaces. Addition of antiscalants, e.g., polymaleic acid (PMA), was shown to be effective in fouling mitigation by inhibiting the transformation of amorphous calcium phosphate to hydroxyapatite. In the case of synthetic MWW_NF, significant crystalline fouling was observed at pH 7.2 while bulk precipitation reduced the driving force for crystalline fouling when pH was adjusted to 7.8. Pilot-scale studies with actual MWW revealed that the addition of PMA alone is not sufficient to control scale buildup and that controlling pH at 7.8 is needed to ensure proper operation of the Cooling tower, as predicted by laboratory studies with synthetic wastewater. Alternatively, nitrification and sand filtration would accomplish the same goal without any chemical addition. Overall, this study demonstrated that it is possible to manage crystalline fouling on hot condenser tube surfaces associated with the use of treated municipal wastewater just by pH control and antiscalant addition and that significant additional treatment of municipal wastewater prior to use in recirculating Cooling Systems may not be necessary
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corrosion management in power plant Cooling Systems using tertiary treated municipal wastewater as makeup water
Corrosion Science, 2012Co-Authors: Mahbuboor Rahman Choudhury, Radisav D. Vidic, Mingkai Hsieh, David A DzombakAbstract:Abstract Additional tertiary treatment of secondary-treated municipal wastewater (MWW) is necessary to reduce its scaling potential for use in power plant Cooling Systems. In this study corrosiveness of three tertiary-treated municipal wastewaters (acidified MWW, MWW treated by nitrification–filtration, and MWW treated by nitrification–filtration and granular activated carbon adsorption) towards mild steel, copper, and cupronickel alloys was assessed. pH, ammonia, and organic matter were identified as important corrosion influencing parameter in tertiary-treated municipal wastewater. Corrosiveness of wastewater towards metal alloys increased after tertiary treatments. However, corrosion of mild steel and copper alloys was controlled within acceptable limits using the corrosion inhibitor tolyltriazole.
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control of mineral scale deposition in Cooling Systems using secondary treated municipal wastewater
Water Research, 2011Co-Authors: Mingkai Hsieh, David A Dzombak, Shih-hsiang Chien, Jason D Monnell, Radisav D. VidicAbstract:Secondary-treated municipal wastewater (MWW) is a promising alternative to freshwater as power plant Cooling system makeup water, especially in arid regions. A prominent challenge for the successful use of MWW for Cooling is potentially severe mineral deposition (scaling) on pipe surfaces. In this study, theoretical, laboratory, and field work was conducted to evaluate the mineral deposition potential of MWW and its deposition control strategies under conditions relevant to power plant Cooling Systems. Polymaleic acid (PMA) was found to effectively reduce scale formation when the makeup water was concentrated four times in a recirculating Cooling system. It was the most effective deposition inhibitor of those studied when applied at 10 mg/L dosing level in a synthetic MWW. However, the deposition inhibition by PMA was compromised by free chlorine added for biogrowth control. Ammonia present in the wastewater suppressed the reaction of the free chlorine with PMA through the formation of chloramines. Monochloramine, an alternative to free chlorine, was found to be less reactive with PMA than free chlorine. In pilot tests, scaling control was more challenging due to the occurrence of biofouling even with effective control of suspended bacteria. Phosphorous-based corrosion inhibitors are not appropriate due to their significant loss through precipitation reactions with calcium. Chemical equilibrium modeling helped with interpretation of mineral precipitation behavior but must be used with caution for recirculating Cooling Systems, especially with use of MWW, where kinetic limitations and complex water chemistries often prevail.
X Q Zhai - One of the best experts on this subject based on the ideXlab platform.
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a review for research and new design options of solar absorption Cooling Systems
Renewable & Sustainable Energy Reviews, 2011Co-Authors: X Q Zhai, Ming Qu, Yue Li, R Z WangAbstract:Solar Cooling technology is environmentally friendly and contributes to a significant decrease of the CO2 emissions which cause the green house effect. Currently, most of the solar Cooling Systems commonly used are the hot water driven lithium bromide absorption chillers. According to the operating temperature range of driving thermal source, single-effect LiBr/H2O absorption chillers have the advantage of being powered by ordinary flat-plate or evacuated tubular solar collectors available in the market. In this paper, besides the review of the existing theoretical and experimental investigations of solar single-effect absorption Cooling Systems, some new design options with regard to solar collectors, auxiliary energy Systems and Cooling modes were introduced. And then, other main types of solar absorption Cooling Systems based on double-effect, half-effect and two-stage absorption chillers were summarized. For buildings with high amounts of Cooling load and limited installation area, solar-powered double-effect absorption Cooling Systems may be considered on condition that the direct irradiation is high enough. Half-effect absorption chillers and two-stage absorption chillers seem to be more suitable for air-cooled solar absorption Cooling Systems in hot and dry regions which are short of water. It is highly recommended to study the standardised design guidelines according to different areas for the purpose of widespread applications of solar Cooling Systems.
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a review for absorbtion and adsorbtion solar Cooling Systems in china
Renewable & Sustainable Energy Reviews, 2009Co-Authors: X Q Zhai, R Z WangAbstract:In the past decades, solar water collectors were installed for the main purpose of preheating domestic hot water or to cover a fraction of the space heating demand in China. However, solar Cooling Systems were constructed just for demonstration purposes. Since the building of the first solar-powered absorption Cooling system in Shenzhen in 1987, there have been over 10 additional solar Cooling demonstration projects constructed. In this paper, the most representative five projects including both absorption and adsorption Cooling Systems are introduced and summarized. From the demonstrations, solar absorption Cooling Systems have been shown to be more suitable for large building air-conditioning Systems. Comparatively, solar adsorption Cooling Systems are more promising for small size air-conditioning Systems. In order to attain high utilization ratio, it is highly recommended to design solar-powered integrated energy Systems in public buildings. In addition, highly efficient heat pumps are considered as the most appropriate auxiliary heat sources for solar Cooling Systems, for the purpose of all-weather operation. In the 11th Five year research project (duration 2006-2010), solar Cooling technologies will be further investigated to achieve a breaking through in the integration of solar Cooling Systems with buildings.
T T Chow - One of the best experts on this subject based on the ideXlab platform.
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comparative study of solar Cooling Systems with building integrated solar collectors for use in sub tropical regions like hong kong
Applied Energy, 2012Co-Authors: K.f. Fong, T T ChowAbstract:The performance of solar Cooling Systems with building-integrated (BI) solar collectors was simulated and the results compared with those having the solar collectors installed conventionally on the roof based on the weather data in Hong Kong. Two types of solar collectors and the corresponding Cooling Systems, namely the flat-plate collectors for absorption refrigeration and the PV panels for DC-driven vapour compression refrigeration, were used in the analysis. It was found that in both cases, the adoption of BI solar collectors resulted in a lower solar fraction (SF) and consequently a higher primary energy consumption even though the zone loads were reduced. The reduction in SF was more pronounced in the peak load season when the solar radiation was nearly parallel to the solar collector surfaces during the daytimes, especially for those facing the south direction. Indeed, there were no outputs from the BI flat-plate collectors facing the south direction between May and July. The more severe deterioration in the system performance with the BI flat-plate type collectors made them technically infeasible in terms of the energy-saving potential. It was concluded that the use of BI solar collectors in solar Cooling Systems should be restricted only to situations where the availability of the roof was limited or insufficient when applied in sub-tropical regions like Hong Kong.
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comparative study of different solar Cooling Systems for buildings in subtropical city
Solar Energy, 2010Co-Authors: K.f. Fong, T T Chow, L S ChanAbstract:In recent years, more and more attention has been paid on the application potential of solar Cooling for buildings. Due to the fact that the efficiency of solar collectors is generally low at the time being, the effectiveness of solar Cooling would be closely related to the availability of solar irradiation, climatic conditions and geographical location of a place. In this paper, five types of solar Cooling Systems were involved in a comparative study for subtropical city, which is commonly featured with long hot and humid summer. The solar Cooling Systems included the solar electric compression refrigeration, solar mechanical compression refrigeration, solar absorption refrigeration, solar adsorption refrigeration and solar solid desiccant Cooling. Component-based simulation models of these Systems were developed, and their performances were evaluated throughout a year. The key performance indicators are solar fraction, coefficient of performance, solar thermal gain, and primary energy consumption. In addition, different installation strategies and types of solar collectors were compared for each kind of solar Cooling system. Through this comparative study, it was found that solar electric compression refrigeration and solar absorption refrigeration had the highest energy saving potential in the subtropical Hong Kong. The former is to make use of the solar electric gain, while the latter is to adopt the solar thermal gain. These two solar Cooling Systems would have even better performances through the continual advancement of the solar collectors. It will provide a promising application potential of solar Cooling for buildings in the subtropical region.