split flow
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2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Justin M. Curtiss ◽  
Darren K. Emge

AbstractGeneration and control of humidity in a testing environment is crucial when evaluating a chemical vapor sensor as water vapor in the air can not only interfere with the sensor itself, but also react with a chemical analyte changing its composition. Upon constructing a split-flow humidity generator for chemical vapor sensor development, numerous issues were observed due to instability of the generated relative humidity level and drift of the humidity over time. By first fixing the initial relative humidity output of the system at 50%, we studied the effects of flowrate on stabilization time along with long term stability for extended testing events. It was found that the stabilization time can be upwards of 7 h, but can be maintained for greater than 90 h allowing for extended experiments. Once the stabilization time was known for 50% relative humidity output, additional studies at differing humidity levels and flowrates were performed to better characterize the system. At a relative humidity of 20% there was no time required to stabilize, but when increased to 80% this time increased to over 4 h. With this information we were better able to understand the generation process and characterize the humidity generation system, output stabilization and possible modifications to limit future testing issues.


2021 ◽  
Author(s):  
Deogratius Kisitu ◽  
Alfonso Ortega

Abstract Impingement split flow liquid-cooled microchannel cold plates are one of several flow configurations used for single-phase liquid cooling. Split flow or top-in/side-exit (TISE) cold plates divide the flow into two branches thus resulting in halved or reduced flow rates and flow lengths, compared to traditional side-in /side-exit (SISE) or parallel flow cold plates. This has the effect of reducing the pressure drop because of the shorter flow length and lower flow rate and increasing the heat transfer coefficient due to thermally developing as opposed to fully developed flow. It is also claimed that the impinging flow increases the heat transfer coefficient on the base plate in the region of impingement. Because of the downward impinging and turning flow, there are no exact analytical models for this flow configuration. Computational and experimental studies have been performed, but there are no useful compact analytical models in the literature that can be used to predict the performance of these impingement cold plates. Results are presented for novel physics-based laminar flow models for a TISE microchannel cold plate based on an equivalent parallel channel flow approach. We show that the new models accurately predict the thermal-hydraulic performance over a wide range of parameters.


2021 ◽  
pp. 462634
Author(s):  
Kevin Petersen ◽  
Farhad Shiri ◽  
Tonguc Onur Tasci ◽  
Himanshu Sant ◽  
Joshua Hood ◽  
...  

Author(s):  
Cynthia Nagy ◽  
Robert Huszank ◽  
Attila Gaspar

AbstractThis paper aims at studying open channel geometries in a layer-bed-type immobilized enzyme reactor with computer-aided simulations. The main properties of these reactors are their simple channel pattern, simple immobilization procedure, regenerability, and disposability; all these features make these devices one of the simplest yet efficient enzymatic microreactors. The high surface-to-volume ratio of the reactor was achieved using narrow (25–75 μm wide) channels. The simulation demonstrated that curves support the mixing of solutions in the channel even in strong laminar flow conditions; thus, it is worth including several curves in the channel system. In the three different designs of microreactor proposed, the lengths of the channels were identical, but in two reactors, the liquid flow was split to 8 or 32 parallel streams at the inlet of the reactor. Despite their overall higher volumetric flow rate, the split-flow structures are advantageous due to the increased contact time. Saliva samples were used to test the efficiencies of the digestions in the microreactors. Graphical abstract


2021 ◽  
pp. 1-59
Author(s):  
Piyush Jain ◽  
Mike Flannigan

AbstractNorthern hemisphere mid-latitudeweather is strongly influenced by the polar jet stream (PJS), which dictates the position of storm tracks; this influence also extends to weather patterns conducive to the ignition and growth of large wildfires. We examined the role of the PJS on extreme wildfire events in North America (NA) between 40° and 70°N latitude, using fire spread events (FSEs) for 2002—2016. Climatologies of the 300-hPa wind components and derived quantities show that the PJS weakens and moves northward in the Boreal summer coincident with the fire season. We use spatio-temporal compositing of 300-hPa winds and 500-hPa geopotential height anomalies to show that FSEs are associated with an upper-level ridge and high centered over events, except eastern Canada where patterns are displaced westward. Ridge patterns persist longer for FSEs in western NA compared with Eastern NA, as well as for May to August compared with April, September and October. These tropospheric patterns also occur concomitantly with surface weather drivers of fire spread including positive daily mean temperature and vapor pressure deficit anomalies and negative precipitation anomalies. Distributions of maximum and minimum latitudinal jet stream peak, ridge and trough positions, relative to FSEs, confirm that events occur predominantly southward of the jet stream core and near a ridge for low split flow configurations but not necessarily for high split flow configurations. These findings have wide-reaching implications for better understanding NA fire regimes and potential fire management strategies (eg. resource pre-positioning and tactical suppression) through improved forecasting of fire weather.


2021 ◽  
Vol 6 (2) ◽  
pp. 43
Author(s):  
Yufinda Rahmatika Pratama ◽  
Beauty Anggraheny Ikawanty ◽  
Andriani Parastiwi
Keyword(s):  

Di industry, penggunaan Heat Exchanger sangat luas fungsinya. Heat Exchanger adalah alat pentransfer energi panas antara dua fluida yang berbeda temperature dan terjadi kontak panas. Semakin lama terjadi kontak panas, maka efisiensi perpindahan panas semakin besar. Untuk itu, diperlukan desain yang baik agar perpindahan panas terjadi secara efisien. diharapkan, udara input bertekanan yang masuk Heat Exchanger dapat menghasilkan suhu 200ºC. Permasalahan selanjutnya adalah tidak adanya otomasi pengatur besar kecilnya api kompor gas pada heat exchanger.Kontrol yang digunakan otomasi adalah kontrol fuzzy yang berfungsi untuk menstabilkan suhu output heat exchanger 200ºC dengan mengatur putaran motor servo yang terpasang valve kompor gas. Dengan kontrol tersebut, putaran motor servo akan berubah seiring dengan perubahan suhu yang terbaca dari sensor suhu PT100 pada output heat exchanger. Suhu output heat exchanger mencapai 200ºC selama kurang lebih 10 menit dengan tekanan input 3 bar dan flow 11 l/m serta tekanan input 4 bar dan flow 13 l/m.


2021 ◽  
Vol 93 (5) ◽  
pp. 2888-2897
Author(s):  
Farhad Shiri ◽  
Bruce K. Gale ◽  
Himanshu Sant ◽  
Brody King ◽  
Gina T. Bardi ◽  
...  

Author(s):  
Ankit Bhagat ◽  
Gautam Ghaisas ◽  
John Mathew ◽  
Shankar Krishnan

Abstract The mitigation of boiling instabilities by employing water-alcohol mixtures as coolants in a two-phase pumpless loop is experimentally investigated. Water-miscible alcohol, namely 2-propanol, is added to water in quantities of 0.05, 0.1, and 0.2 mole fractions to reduce the bubble departure diameters. Boiling experiments are carried out in the pumpless loop involving a copper-based split-flow microchannel evaporator. Two-phase flow stability and heat transfer performance are compared between pure water and 2-propanol-water mixtures. Temperature measurements at the evaporator inlet, evaporator outlet, and condenser inlet show a considerable reduction in fluctuations when the binary mixtures are used as coolants. Therefore, the addition of a small amount of alcohol to water is proposed as a simple technique to control two-phase flow instabilities as against complex geometry modification to the evaporator, often studied in the literature. The pumpless loop with water-alcohol mixtures is a viable thermal management solution for power electronic devices that involve time-varying workloads.


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