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Tuo H.,University of Illinois at Urbana - Champaign | Hrnjak P.,University of Illinois at Urbana - Champaign | Hrnjak P.,Cts Inc.
International Journal of Heat and Mass Transfer

This paper proposes a novel solution to reduce the impacts of periodic reverse flow and induced boiling fluctuations on the performance of a microchannel evaporator used in an air-conditioning or other similar refrigeration system. Reverse vapor trapped within the inlet header is continuously vented bypassing microchannels. Simultaneous flow visualizations and measurements quantified the effects of venting the reverse vapor on the evaporator performance. The vapor-liquid interface in the inlet header is elevated above all the microchannel inlets, resulting in more uniform liquid distribution among channels. Evaporator surface temperatures measured by an infrared camera oscillate with reduced amplitude (less than 1 C) compared to the situation without venting, indicating more stable boiling heat transfer and two-phase flow within the microchannels. The evaporator pressure drop is reduced up to about 15% due to removal of the reversed vapor flow. In addition, the reverse vapor flow is characterized for the first time through this method. Both its average flow rate and oscillation amplitude increase with average heat flux, while the oscillation period is reduced. Compared to the total refrigerant flow rate supplied to the evaporator, the average reverse vapor flow is in the range of 2-8% at the conditions explored. © 2013 Published by Elsevier Ltd. Source

Grilo A.,New University of Lisbon | Jardim-Goncalves R.,Cts Inc.
Advanced Engineering Informatics

The development of web-based collaborative platforms, BIM, and transactional e-marketplaces has been changing the way companies in the AEC sector work. However, due to interoperability issues, the main problems of distributed data and information management across AEC companies and projects are yet to be overcome. This paper presents the Cloud-Marketplace concept, which expands on earlier developments combining BIM, SOA, Cloud Computing, and e-marketplaces in order to create interoperable communities of e-platforms. The Vortaway case study is described to demonstrate the validation of the concept in simple AEC e-procurement processes.© 2012 Elsevier Ltd. All rights reserved. Source

Tuo H.,University of Illinois at Urbana - Champaign | Hrnjak P.,University of Illinois at Urbana - Champaign | Hrnjak P.,Cts Inc.
International Journal of Refrigeration

This paper presents a proposal for a venting reverse vapor in flash gas removal A/C system in order to improve refrigerant distribution and reduce pressure drop in microchannel evaporator and thus increase system efficiency. Introduction to the reverse vapor flow observed in parallel flow microchannel evaporator was presented in earlier IJR paper by the authors. An experimental comparison of the A/C system with new approach to an FGB system revealed that vapor venting provided a 5% increase of cooling capacity and 3% of COP when operated at identical test conditions, while the maximum COP improvement was approximately 10%-12% when capacity is matched by reduction of compressor speed. The improvement compared to direct expansion system was significantly higher. © 2013 Elsevier Ltd and IIR. All rights reserved. Source

Tuo H.,University of Illinois at Urbana - Champaign | Hrnjak P.,University of Illinois at Urbana - Champaign | Hrnjak P.,Cts Inc.
International Journal of Refrigeration

This paper presents an experimental and numerical investigation of the flow maldistribution caused by the pressure drop in headers and its impact on the performance of a microchannel evaporator with horizontal headers and vertically oriented tubes. Experimental results show that the flash gas bypass method almost eliminates the quality induced maldistribution. However, refrigerant flow maldistribution caused by the header pressure drop still exists. This is mainly because the pressure drop along the headers results in uneven pressure difference and therefore non-uniform liquid refrigerant mass flow rate across each microchannel tube. A microchannel evaporator model validated by experimental results is employed to quantify header pressure drop induced flow maldistribution. Parametric analysis reveals that such maldistribution impact is significantly reduced by enlarging the outlet header size, increasing heat exchanger aspect ratio, or reducing the microchannel size while other parameters are kept constant. When ratio of outlet header to the total evaporator pressure drop is less than 30%, the cooling capacity reduction is limited below 3%. © 2013 Elsevier Ltd and IIR. All rights reserved. Source

Piovano S.,University of Turin | Clo S.,Cts Inc. | Giacoma C.,University of Turin
Biological Conservation

Chondrichthyan populations in the Mediterranean Sea have been heavily affected by the impact of fishing activities. In the last two decades, even fishing gears that were traditionally considered highly selective, such as pelagic longlines, have been revealed to be responsible for the capture of many unwanted species. The pelagic stingray (Pteroplatytrygon violacea) is not an endangered nor a charismatic species, but it largely dominates longlines bycatch fractions. The aim of our study was to investigate the importance of three main variables, bait size, presence and type of light attractors, and hook size and shape, in the capture rate of pelagic stingrays. Ninety-seven longline experimental sets were run. Trials took place on nine vessels in the Strait of Sicily, central Mediterranean Sea, over a period of 3 years from 2005 to 2007. Results showed that the larger the J hook, the lower the stingray capture rate. Moreover, 16/0 circle hooks had a significantly lower number of stingrays captured per 1000 hooks than J hooks, up to ∼80%. Bait size, within the range of sizes assessed, and use of light attractors did not have significant effects on stingray catch rate. These results suggest that the adoption of large circle hooks by commercial and artisanal swordfish longlining may be a measure to reduce their environmental footprint. © 2009 Elsevier Ltd. Source

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