The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
Yi Jiang - One of the best experts on this subject based on the ideXlab platform.
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irreversible processes and performance improvement of desiccant wheel dehumidification and cooling systems using exergy
Applied Energy, 2015Co-Authors: Rang Tu, Yi JiangAbstract:Desiccant wheels are effective dehumidification devices. The performance of desiccant dehumidification and cooling systems is examined in this paper. Based on a theoretical investigation, six kinds of systems (systems A–F) were analyzed as the system changed from being reversible to being irreversible, which sharply reduced performance. The performance of system E, which is composed of an actual desiccant wheel, an actual heat recovery exchanger, and an actual single-stage heat pump, represents the relatively high standards that actual systems can achieve. Under the designed working conditions, COP and exergy efficiency of system E were 5.0 and 18.3%, respectively. Based on the analysis of a real ventilation cycle, it was found that to improve the system’s performance, over-dehumidification should be avoided, and heat sources with low exergy destruction should be utilized. To avoid over-dehumidification, the direct evaporative cooler at the Processed Air side should be replaced by a sensible heat exchanger. When the electrical heater is replaced by a heat pump system, the performance of such a system can be improved, especially when pre-cooling is adopted. The proposed heat pump-driven system had similar schematic and performance characteristics as system E, with COP and exergy efficiency being 5.01 and 18.0%, respectively, under the same working conditions.
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lowering the regeneration temperature of a rotary wheel dehumidification system using exergy analysis
Energy Conversion and Management, 2015Co-Authors: Xiaohua Liu, Yi JiangAbstract:Abstract Rotary wheel dehumidification is an effective Air drying method. This paper analyzes the factors influencing the regeneration temperature from the perspective of exergy. When the dehumidification capacity is fixed, there are two main ways to reduce the regeneration temperature. One is to decrease the exergy destruction during heat and mass transfer in the desiccant wheel, and the other is to decrease the thermal exergy obtained by the Processed Air after dehumidification. For the first way, the exergy destruction is influenced by the uniformity of the heat and mass transfer driving forces in the desiccant wheel, which can be described by the unmatched coefficient ς . The wheel should be evenly divided, and the two streams of Air should have the same flow rate to reduce the exergy destruction. The regeneration temperature can be reduced from above 130 °C to below 70 °C when the Air is dehumidified from 20 g/kg to 11 g/kg. For the second way, the thermal exergy obtained by the Processed Air is influenced by the temperature variation range during dehumidification. Multi-stage dehumidification and pre-cooling are effective mode, with required regeneration temperature lower than 40 °C.
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performance analysis of a two stage desiccant cooling system
Applied Energy, 2014Co-Authors: Rang Tu, Yi JiangAbstract:Multi-stage desiccant systems are an effective way to improve the performance of desiccant dehumidification systems, which can greatly decrease the required regeneration temperature and make possible the utilization of exhaust heat from the heat pump. The performance of a heat pump-driven two-stage desiccant wheel system is analyzed in this paper. Models of the desiccant wheel and heat pump systems are utilized to predict system performance. The effects on system performance of the compressor power input, the heat exchange area distribution between evaporators and condensers, the wheel’s rotation speed, and the inlet parameters of the Processed Air are investigated. When the supplied Air humidity ratio is 10g/kg, COPt of the desiccant system is 5.5 under Beijing summer condition. The key to improving system performance is to match the cooling capacity and exhaust heat provided by the heat pump with the requirements of dehumidification and regeneration. An improved system utilizing an indirect cooler to recover the cooling capacity from the indoor exhaust Air is then proposed, with COPt improving by 15% compared to the original system.
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Performance analysis of a new kind of heat pump-driven outdoor Air processor using solid desiccant
Renewable Energy, 2013Co-Authors: Xiaohua Liu, Yi JiangAbstract:Abstract A new type of outdoor Air dehumidification processor using solid desiccant is proposed, in which a heat pump and square desiccant plates are combined. Each desiccant plate consists of an Air channel with a honeycomb structure that is coated with desiccant material. The square desiccant plates change positions between the Processed Air duct for dehumidification and the regenerated Air duct for regeneration. The cooling capacity of the heat pump is utilized to cool the Processed Air, and the exhaust heat of the heat pump is used to provide regenerative heat to the desiccant. Several stages can be combined together to gain higher efficiency. The proposed desiccant dehumidifier can achieve a low humidity ratio of the supplied Air and provides low-temperature regeneration. A mathematical model is established to predict the performance of this desiccant processor, and the model shows good agreement with the experimental results. The factors that influence the performance of the processor are then analyzed in order to maximize performance. The simulation results show that the proposed desiccant processor provides regeneration at a low temperature (40–50 °C), and the COP can surpass 4.0 at different Processed Air inlet states.
Jorg Ehlbeck - One of the best experts on this subject based on the ideXlab platform.
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Pre-drying treatment of plant related tissues using plasma Processed Air: Impact on enzyme activity and quality attributes of cut apple and potato
Innovative Food Science and Emerging Technologies, 2017Co-Authors: Sara Bußler, Jorg Ehlbeck, Oliver SchluterAbstract:Abstract During post-harvest processing of fresh cut and dried fruits and vegetables, polyphenol oxidase (PPO) and peroxidase (POD) need to be inactivated or inhibited in order to avoid undesirable browning reactions and loss of sensorial or nutritional quality. To meet this goal, the application of plasma Processed Air (PPA) offers a promising “gentle” alternative to traditional methods, such as pasteurization or the addition of anti-browning compounds. Using ambient Air as process gas instead of an expensive noble gas, such as argon, exhibits a substantial improvement for the development of large-scale plasmas at ambient pressure and allows the indirect treatment of larger goods within a remote exposure reactor. In this study the ability of PPA to inactivate PPO and POD in complex food matrices and its impact on quality parameters, such as color, texture and cell integrity directly after freshly cutting and during storage of warm Air dried and freeze dried produce was evaluated. The study evidently shows that PPA processing is capable of reducing the activity of PPO and POD in the freshly cut tissue from both apple and potato. Following exposure to PPA for 10 min the PPO activity was reduced by about 62% and 77% in fresh cut apple and potato tissue, respectively. POD, as the more temperature-stable enzyme, was even less stable upon PPA treatment for 10 min and was reduced by about 65% and 89% in fresh cut apple and potato tissue, respectively. Blackening of the potato tissue could be completely prevented by plasma treatment while a browning different from the habitual nature of enzymatic browning occurred upon exposure of the apple tissue to PPA. In both cases, the pH value on the tissue surface dropped to 1.5 while cell integrity and dry matter content were not significantly affected. Industrial relevance The quality and shelf life of freshly cut and dried fruits and vegetables greatly depend on the activity of naturally occurring enzymes which catalyze browning reactions at cut surfaces. This study shows that the application of PPA, as a promising nonthermal “pasteurization” technology, enables the inactivation of PPO and POD in complex food matrices. It further describes the impact of the PPA treatment on quality parameters of the freshly cut tissue from apple and potato and goes beyond on evaluating color, texture and enzyme activity in warm Air dried and freeze dried tissue over a storage time of three weeks. The results contribute to the understanding and product-specificity of PPA-induced effects on quality and shelf life of fresh cut and dried fruit and vegetable produce and could be a basis for a possible industrial implementation.
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inactivation of microorganisms in tyvek packaging by microwave plasma Processed Air
Global Journal of Biology Agriculture & Health Sciences, 2015Co-Authors: Uta Schnabel, Mathias Andrasch, Klaus-dieter Weltmann, Jorg EhlbeckAbstract:Plasma is well-known for its antimicrobial capacity and moreover, it is successfully used in manifold industrial fields such as packaging industry. Microwave plasma Processed gas with shares of reactive nitrogen species (RNS) was investigated for its decontamination efficiency against vegetative bacteria, conidia and bacterial endospores packed in Tyvek ® . For all tested microorganisms, increased inactivation was found at prolonged treatment times. Furthermore, a treatment with moistened gas resulted in shorter treatment times and a dependency of humidity was observed. The inactivation rates increased up to 6 log10 steps. The microwave plasma Processed gas showed very high microbial effects to vegetative bacteria, spores of Bacillus atrophaeus and Aspergillus brasiliensis in treatment times comparable to currently common methods like EO, FORM and hydrogen peroxide. Moreover, this new methode is charaterized by advantages like no thermal influences, no toxicity for human and environment and low costs.
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Impact of plasma Processed Air (PPA) on quality parameters of fresh produce
Postharvest Biology and Technology, 2015Co-Authors: Matthias Baier, Jorg Ehlbeck, Dietrich Knorr, Werner B. Herppich, Oliver SchluterAbstract:Abstract The ubiquitous presence of spoilage microorganisms and sporadic occurrences of human pathogens on heat-sensitive fresh produce are serious economic and health issues. A potential solution for the gentle sanitation of fresh fruit and vegetables is the application of atmospheric pressure plasmas. In this study, a microwave-driven Air plasma torch was used for indirect treatment of whole pieces of fruits and vegetables within a remote exposure chamber for up to 10 min. The impact of this technique on the external quality of apples, cucumbers, tomatoes and carrots, and its antimicrobial efficacy on indigenous and inoculated microorganisms were examined. After 5 min of plasma application, total mesophilic counts were reduced by 3.4 ± 0.4, 1.2 ± 0.5, 5.2 ± 0.5, and 3.3 ± 0.5 log cycles on apples, cucumbers, carrots and tomatoes, respectively. After 10 min, counts of artificially inoculated Escherichia coli were reduced by 4.6 ± 2.0 and 6.0 ± 0.8 log cycles on apples and carrots, respectively. Significant effects of plasma treatment were found on color of tomatoes and carrots, and on chlorophyll fluorescence parameters of cucumbers, whereas elasticity remained almost unaffected in all produce. The plasma Processed Air treatment proved to be suitable for apples as the most stable product. For more susceptible produces such as carrots, however, plasma induced effects on the surface. Hence, in such cases, the application of indirect plasma needs to be specifically adapted to ensure product quality and safety.
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Decontamination and Sensory Properties of Microbiologically Contaminated Fresh Fruits and Vegetables by Microwave Plasma Processed Air (PPA)
Journal of Food Processing and Preservation, 2014Co-Authors: Uta Schnabel, Oliver Schluter, Rijana Niquet, Holger Gniffke, Jorg EhlbeckAbstract:Currently used disinfection or sanitation methods for fresh fruits and vegetables lack antimicrobial effectiveness, but are high in costs, water consumption or chemicals. One alternative could be to apply nonthermal plasma at atmospheric pressure to the described issue. The experimental set-up implements microwave plasma, which generates plasma Processed Air (PPA) containing manifold reactive nitrogen species-based chemical and antimicrobial compounds. Five different fresh produces were first contaminated with seven different microorganisms e.g., bacteria, yeasts and endospores followed by a treatment with PPA. The plasma was ignited for 7 s only. After a post-plasma treatment time of maximum 15 min with PPA, reduction factors of microbiological load greater than 6 log were detected. Furthermore, sensory examinations showed only little influences in texture, appearance and odor. The characteristics of plasma and its generated cocktail of chemical compounds leads to a high microbial inactivation on various specimens and offers a wide range of possible applications. Practical Applications Nonthermal atmospheric pressure plasma is a nonthermal, nontoxic and low-cost possibility to inactivate microorganisms on fresh produce surfaces. It could be used in dry and wet environments and allows a treatment of fresh food and virtually every conceivable surface in batch or inline processes along the whole value chain of food production, and could be implemented as an alternative to ozone or chlorine dioxide treatment.
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inactivation of vegetative microorganisms and bacillus atrophaeus endospores by reactive nitrogen species rns
Plasma Processes and Polymers, 2014Co-Authors: Uta Schnabel, Mathias Andrasch, Klaus-dieter Weltmann, Jorg EhlbeckAbstract:Plasma is used as a common technology for the treatment and modification of surfaces in a variety of industrial branches. Decontamination of inorganic materials by plasma is possible with deterioration of the materials properties of a few nanometres. The inactivation efficacy of microwave plasma Processed Air against vegetative bacteria and bacterial endospores was investigated. The gained results provide inactivation rates up to 6 log in total treatment times (15–30 min) comparable to sterilization treatment times of thermo-sensitive medical devices with ethylene oxide, formaldehyde or H2O2. Additions like O2 or O3 did not promote the antimicrobial efficacy. Moreover, this new method is characterized by advantages like no thermal influence, no toxicity for human and environment and low costs.
Oliver Schluter - One of the best experts on this subject based on the ideXlab platform.
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Pre-drying treatment of plant related tissues using plasma Processed Air: Impact on enzyme activity and quality attributes of cut apple and potato
Innovative Food Science and Emerging Technologies, 2017Co-Authors: Sara Bußler, Jorg Ehlbeck, Oliver SchluterAbstract:Abstract During post-harvest processing of fresh cut and dried fruits and vegetables, polyphenol oxidase (PPO) and peroxidase (POD) need to be inactivated or inhibited in order to avoid undesirable browning reactions and loss of sensorial or nutritional quality. To meet this goal, the application of plasma Processed Air (PPA) offers a promising “gentle” alternative to traditional methods, such as pasteurization or the addition of anti-browning compounds. Using ambient Air as process gas instead of an expensive noble gas, such as argon, exhibits a substantial improvement for the development of large-scale plasmas at ambient pressure and allows the indirect treatment of larger goods within a remote exposure reactor. In this study the ability of PPA to inactivate PPO and POD in complex food matrices and its impact on quality parameters, such as color, texture and cell integrity directly after freshly cutting and during storage of warm Air dried and freeze dried produce was evaluated. The study evidently shows that PPA processing is capable of reducing the activity of PPO and POD in the freshly cut tissue from both apple and potato. Following exposure to PPA for 10 min the PPO activity was reduced by about 62% and 77% in fresh cut apple and potato tissue, respectively. POD, as the more temperature-stable enzyme, was even less stable upon PPA treatment for 10 min and was reduced by about 65% and 89% in fresh cut apple and potato tissue, respectively. Blackening of the potato tissue could be completely prevented by plasma treatment while a browning different from the habitual nature of enzymatic browning occurred upon exposure of the apple tissue to PPA. In both cases, the pH value on the tissue surface dropped to 1.5 while cell integrity and dry matter content were not significantly affected. Industrial relevance The quality and shelf life of freshly cut and dried fruits and vegetables greatly depend on the activity of naturally occurring enzymes which catalyze browning reactions at cut surfaces. This study shows that the application of PPA, as a promising nonthermal “pasteurization” technology, enables the inactivation of PPO and POD in complex food matrices. It further describes the impact of the PPA treatment on quality parameters of the freshly cut tissue from apple and potato and goes beyond on evaluating color, texture and enzyme activity in warm Air dried and freeze dried tissue over a storage time of three weeks. The results contribute to the understanding and product-specificity of PPA-induced effects on quality and shelf life of fresh cut and dried fruit and vegetable produce and could be a basis for a possible industrial implementation.
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Impact of plasma Processed Air (PPA) on quality parameters of fresh produce
Postharvest Biology and Technology, 2015Co-Authors: Matthias Baier, Jorg Ehlbeck, Dietrich Knorr, Werner B. Herppich, Oliver SchluterAbstract:Abstract The ubiquitous presence of spoilage microorganisms and sporadic occurrences of human pathogens on heat-sensitive fresh produce are serious economic and health issues. A potential solution for the gentle sanitation of fresh fruit and vegetables is the application of atmospheric pressure plasmas. In this study, a microwave-driven Air plasma torch was used for indirect treatment of whole pieces of fruits and vegetables within a remote exposure chamber for up to 10 min. The impact of this technique on the external quality of apples, cucumbers, tomatoes and carrots, and its antimicrobial efficacy on indigenous and inoculated microorganisms were examined. After 5 min of plasma application, total mesophilic counts were reduced by 3.4 ± 0.4, 1.2 ± 0.5, 5.2 ± 0.5, and 3.3 ± 0.5 log cycles on apples, cucumbers, carrots and tomatoes, respectively. After 10 min, counts of artificially inoculated Escherichia coli were reduced by 4.6 ± 2.0 and 6.0 ± 0.8 log cycles on apples and carrots, respectively. Significant effects of plasma treatment were found on color of tomatoes and carrots, and on chlorophyll fluorescence parameters of cucumbers, whereas elasticity remained almost unaffected in all produce. The plasma Processed Air treatment proved to be suitable for apples as the most stable product. For more susceptible produces such as carrots, however, plasma induced effects on the surface. Hence, in such cases, the application of indirect plasma needs to be specifically adapted to ensure product quality and safety.
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Decontamination and Sensory Properties of Microbiologically Contaminated Fresh Fruits and Vegetables by Microwave Plasma Processed Air (PPA)
Journal of Food Processing and Preservation, 2014Co-Authors: Uta Schnabel, Oliver Schluter, Rijana Niquet, Holger Gniffke, Jorg EhlbeckAbstract:Currently used disinfection or sanitation methods for fresh fruits and vegetables lack antimicrobial effectiveness, but are high in costs, water consumption or chemicals. One alternative could be to apply nonthermal plasma at atmospheric pressure to the described issue. The experimental set-up implements microwave plasma, which generates plasma Processed Air (PPA) containing manifold reactive nitrogen species-based chemical and antimicrobial compounds. Five different fresh produces were first contaminated with seven different microorganisms e.g., bacteria, yeasts and endospores followed by a treatment with PPA. The plasma was ignited for 7 s only. After a post-plasma treatment time of maximum 15 min with PPA, reduction factors of microbiological load greater than 6 log were detected. Furthermore, sensory examinations showed only little influences in texture, appearance and odor. The characteristics of plasma and its generated cocktail of chemical compounds leads to a high microbial inactivation on various specimens and offers a wide range of possible applications. Practical Applications Nonthermal atmospheric pressure plasma is a nonthermal, nontoxic and low-cost possibility to inactivate microorganisms on fresh produce surfaces. It could be used in dry and wet environments and allows a treatment of fresh food and virtually every conceivable surface in batch or inline processes along the whole value chain of food production, and could be implemented as an alternative to ozone or chlorine dioxide treatment.
Uta Schnabel - One of the best experts on this subject based on the ideXlab platform.
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plasma treated Air and water assessment of synergistic antimicrobial effects for sanitation of food processing surfaces and environment
Foods, 2019Co-Authors: Uta Schnabel, Mathias Andrasch, Oliver Handorf, Kateryna Yarova, Bjorn Zessin, Susann Zechlin, Diana Sydow, Elke Zellmer, Jorg Stachowiak, Harald BelowAbstract:The synergistic antimicrobial effects of plasma-Processed Air (PPA) and plasma-treated water (PTW), which are indirectly generated by a microwave-induced non-atmospheric pressure plasma, were investigated with the aid of proliferation assays. For this purpose, microorganisms (Listeria monocytogenes, Escherichia coli, Pectobacterium carotovorum, sporulated Bacillus atrophaeus) were cultivated as monocultures on specimens with polymeric surface structures. Both the distinct and synergistic antimicrobial potential of PPA and PTW were governed by the plasma-on time (5⁻50 s) and the treatment time of the specimens with PPA/PTW (1⁻5 min). In single PTW treatment of the bacteria, an elevation of the reduction factor with increasing treatment time could be observed (e.g., reduction factor of 2.4 to 3.0 for P. carotovorum). In comparison, the combination of PTW and subsequent PPA treatment leads to synergistic effects that are clearly not induced by longer treatment times. These findings have been valid for all bacteria (L. monocytogenes > P. carotovorum = E. coli). Controversially, the effect is reversed for endospores of B. atrophaeus. With pure PPA treatment, a strong inactivation at 50 s plasma-on time is detectable, whereas single PTW treatment shows no effect even with increasing treatment parameters. The use of synergistic effects of PTW for cleaning and PPA for drying shows a clear alternative for currently used sanitation methods in production plants. Highlights: Non-thermal atmospheric pressure microwave plasma source used indirect in two different modes-gaseous and liquid; Measurement of short and long-living nitrite and nitrate in corrosive gas PPA (plasma-Processed Air) and complex liquid PTW (plasma-treated water); Application of PTW and PPA in single and combined use for biological decontamination of different microorganisms.
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Plasma-Treated Air and Water—Assessment of Synergistic Antimicrobial Effects for Sanitation of Food Processing Surfaces and Environment
MDPI AG, 2019Co-Authors: Uta Schnabel, Mathias Andrasch, Oliver Handorf, Kateryna Yarova, Bjorn Zessin, Susann Zechlin, Diana Sydow, Elke Zellmer, Jorg Stachowiak, Harald BelowAbstract:The synergistic antimicrobial effects of plasma-Processed Air (PPA) and plasma-treated water (PTW), which are indirectly generated by a microwave-induced non-atmospheric pressure plasma, were investigated with the aid of proliferation assays. For this purpose, microorganisms (Listeria monocytogenes, Escherichia coli, Pectobacterium carotovorum, sporulated Bacillus atrophaeus) were cultivated as monocultures on specimens with polymeric surface structures. Both the distinct and synergistic antimicrobial potential of PPA and PTW were governed by the plasma-on time (5⁻50 s) and the treatment time of the specimens with PPA/PTW (1⁻5 min). In single PTW treatment of the bacteria, an elevation of the reduction factor with increasing treatment time could be observed (e.g., reduction factor of 2.4 to 3.0 for P. carotovorum). In comparison, the combination of PTW and subsequent PPA treatment leads to synergistic effects that are clearly not induced by longer treatment times. These findings have been valid for all bacteria (L. monocytogenes > P. carotovorum = E. coli). Controversially, the effect is reversed for endospores of B. atrophaeus. With pure PPA treatment, a strong inactivation at 50 s plasma-on time is detectable, whereas single PTW treatment shows no effect even with increasing treatment parameters. The use of synergistic effects of PTW for cleaning and PPA for drying shows a clear alternative for currently used sanitation methods in production plants. Highlights: Non-thermal atmospheric pressure microwave plasma source used indirect in two different modes—gaseous and liquid; Measurement of short and long-living nitrite and nitrate in corrosive gas PPA (plasma-Processed Air) and complex liquid PTW (plasma-treated water); Application of PTW and PPA in single and combined use for biological decontamination of different microorganisms
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inactivation of microorganisms in tyvek packaging by microwave plasma Processed Air
Global Journal of Biology Agriculture & Health Sciences, 2015Co-Authors: Uta Schnabel, Mathias Andrasch, Klaus-dieter Weltmann, Jorg EhlbeckAbstract:Plasma is well-known for its antimicrobial capacity and moreover, it is successfully used in manifold industrial fields such as packaging industry. Microwave plasma Processed gas with shares of reactive nitrogen species (RNS) was investigated for its decontamination efficiency against vegetative bacteria, conidia and bacterial endospores packed in Tyvek ® . For all tested microorganisms, increased inactivation was found at prolonged treatment times. Furthermore, a treatment with moistened gas resulted in shorter treatment times and a dependency of humidity was observed. The inactivation rates increased up to 6 log10 steps. The microwave plasma Processed gas showed very high microbial effects to vegetative bacteria, spores of Bacillus atrophaeus and Aspergillus brasiliensis in treatment times comparable to currently common methods like EO, FORM and hydrogen peroxide. Moreover, this new methode is charaterized by advantages like no thermal influences, no toxicity for human and environment and low costs.
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Decontamination and Sensory Properties of Microbiologically Contaminated Fresh Fruits and Vegetables by Microwave Plasma Processed Air (PPA)
Journal of Food Processing and Preservation, 2014Co-Authors: Uta Schnabel, Oliver Schluter, Rijana Niquet, Holger Gniffke, Jorg EhlbeckAbstract:Currently used disinfection or sanitation methods for fresh fruits and vegetables lack antimicrobial effectiveness, but are high in costs, water consumption or chemicals. One alternative could be to apply nonthermal plasma at atmospheric pressure to the described issue. The experimental set-up implements microwave plasma, which generates plasma Processed Air (PPA) containing manifold reactive nitrogen species-based chemical and antimicrobial compounds. Five different fresh produces were first contaminated with seven different microorganisms e.g., bacteria, yeasts and endospores followed by a treatment with PPA. The plasma was ignited for 7 s only. After a post-plasma treatment time of maximum 15 min with PPA, reduction factors of microbiological load greater than 6 log were detected. Furthermore, sensory examinations showed only little influences in texture, appearance and odor. The characteristics of plasma and its generated cocktail of chemical compounds leads to a high microbial inactivation on various specimens and offers a wide range of possible applications. Practical Applications Nonthermal atmospheric pressure plasma is a nonthermal, nontoxic and low-cost possibility to inactivate microorganisms on fresh produce surfaces. It could be used in dry and wet environments and allows a treatment of fresh food and virtually every conceivable surface in batch or inline processes along the whole value chain of food production, and could be implemented as an alternative to ozone or chlorine dioxide treatment.
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inactivation of vegetative microorganisms and bacillus atrophaeus endospores by reactive nitrogen species rns
Plasma Processes and Polymers, 2014Co-Authors: Uta Schnabel, Mathias Andrasch, Klaus-dieter Weltmann, Jorg EhlbeckAbstract:Plasma is used as a common technology for the treatment and modification of surfaces in a variety of industrial branches. Decontamination of inorganic materials by plasma is possible with deterioration of the materials properties of a few nanometres. The inactivation efficacy of microwave plasma Processed Air against vegetative bacteria and bacterial endospores was investigated. The gained results provide inactivation rates up to 6 log in total treatment times (15–30 min) comparable to sterilization treatment times of thermo-sensitive medical devices with ethylene oxide, formaldehyde or H2O2. Additions like O2 or O3 did not promote the antimicrobial efficacy. Moreover, this new method is characterized by advantages like no thermal influence, no toxicity for human and environment and low costs.
Rang Tu - One of the best experts on this subject based on the ideXlab platform.
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irreversible processes and performance improvement of desiccant wheel dehumidification and cooling systems using exergy
Applied Energy, 2015Co-Authors: Rang Tu, Yi JiangAbstract:Desiccant wheels are effective dehumidification devices. The performance of desiccant dehumidification and cooling systems is examined in this paper. Based on a theoretical investigation, six kinds of systems (systems A–F) were analyzed as the system changed from being reversible to being irreversible, which sharply reduced performance. The performance of system E, which is composed of an actual desiccant wheel, an actual heat recovery exchanger, and an actual single-stage heat pump, represents the relatively high standards that actual systems can achieve. Under the designed working conditions, COP and exergy efficiency of system E were 5.0 and 18.3%, respectively. Based on the analysis of a real ventilation cycle, it was found that to improve the system’s performance, over-dehumidification should be avoided, and heat sources with low exergy destruction should be utilized. To avoid over-dehumidification, the direct evaporative cooler at the Processed Air side should be replaced by a sensible heat exchanger. When the electrical heater is replaced by a heat pump system, the performance of such a system can be improved, especially when pre-cooling is adopted. The proposed heat pump-driven system had similar schematic and performance characteristics as system E, with COP and exergy efficiency being 5.01 and 18.0%, respectively, under the same working conditions.
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performance analysis of a two stage desiccant cooling system
Applied Energy, 2014Co-Authors: Rang Tu, Yi JiangAbstract:Multi-stage desiccant systems are an effective way to improve the performance of desiccant dehumidification systems, which can greatly decrease the required regeneration temperature and make possible the utilization of exhaust heat from the heat pump. The performance of a heat pump-driven two-stage desiccant wheel system is analyzed in this paper. Models of the desiccant wheel and heat pump systems are utilized to predict system performance. The effects on system performance of the compressor power input, the heat exchange area distribution between evaporators and condensers, the wheel’s rotation speed, and the inlet parameters of the Processed Air are investigated. When the supplied Air humidity ratio is 10g/kg, COPt of the desiccant system is 5.5 under Beijing summer condition. The key to improving system performance is to match the cooling capacity and exhaust heat provided by the heat pump with the requirements of dehumidification and regeneration. An improved system utilizing an indirect cooler to recover the cooling capacity from the indoor exhaust Air is then proposed, with COPt improving by 15% compared to the original system.