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متن کامل


اطلاعات دوره: 
  • سال: 

    2019
  • دوره: 

    11
  • شماره: 

    2
  • صفحات: 

    114-125
تعامل: 
  • استنادات: 

    1
  • بازدید: 

    171
  • دانلود: 

    0
چکیده: 

The measure of volumetric flow rate is utilized to calculate sampling volume and airborne concentration in integrated air sampling. Consequently, calibration of the sampling train to verify volumetric flow rate is critical. The relation between sampler PRESSURE DROP and volumetric flow rate was studied in support of using the former rather than the latter for the calibration of sampling trains. Four types of respirable cyclones, two filter brands with membrane samples of the same and different lots of production, and two personal pump types were considered as components of the sampling trains under consideration. Volumetric flow rate and PRESSURE DROP were measured under controlled conditions in a cylindrical jar designed for these determinations. For all the configurations considered, the relation between sampler PRESSURE DROP and standard volumetric flow rate was linear. Intra-sample selection of cyclones of the same type and pump type did not create significant differences in sampler PRESSURE DROP. Filter selection, regardless of brand or production lot, did create linear response functions that had statistically different slopes and intercepts. When grouped by cyclone type and filter brand, the sampler PRESSURE DROP at the flow rate recommended by the cyclone’ s manufacturers showed variability that was not normally distributed. The recommended central tendency estimate of PRESSURE DROP is the median value, with point estimates that should be specific to a cyclone type / filter brand combination.

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نویسنده: 

TAHERI REZA | EHTERAMI SANAZ

اطلاعات دوره: 
  • سال: 

    2011
  • دوره: 

    7
تعامل: 
  • بازدید: 

    198
  • دانلود: 

    0
چکیده: 

THIS STUDY COMPARES 5 WELL-KNOWN TWO-PHASE PRESSURE DROP MODELS IN HORIZONTAL CHANNELS AND PRESENTS ONE OF THEM AS AN OPTIMUM MODEL. IN ORDER TO REACH THIS AIM A SET OF DATA POINTS WHICH CONTAINS 90 POINTS IS USED. THIS SET OF DATA POINTS COVERS 6 FLUIDS (CO2, R-134A, R-22, R-236EA, R-404A, R410A) WHICH THE RANGES OF DIAMETERS, MASS FLUXES AND VAPOR QUALITIES ARE 1.4-6.1 MM, 200-400 KG/M2.S, 0.1-0.9, RESPECTIVELY. THESE MODELS ARE COMPARED WITH 3 DIFFERENT METHODS WHICH USE MEAN ABSOLUTE ERROR (MAE), RELATIVE PERFORMANCE FACTOR (RPF), AND PERCENTAGE OF DATA WHICH FALL BETWEEN ±30% ERRORS BANDS TO COMPARE THEM. ALL METHODS GIVE SIMILAR RESULTS AND PRESENT THE MULLER-STEIN HAGEN AND HECK MODEL AS THE MOST ACCURACY MODEL IN ALL.

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اطلاعات دوره: 
  • سال: 

    2017
  • دوره: 

    10
  • شماره: 

    2
  • صفحات: 

    519-527
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    263
  • دانلود: 

    0
چکیده: 

This paper presents a steady state one-dimensional two-fluid model for gas-solid two-phase flow in a vertical riser. The model is solved using conservative variable approach for the gas phase, and fourth order Runge-Kutta method is used for the solid phase. The model predictions for PRESSURE DROP are compared with available experimental data and with Eulerian-Lagrangian predictions, and a good agreement is obtained. The results indicate that the PRESSURE DROP increases as the solid mass flow rate, particle size, and particles density increase. In addition, the model predictions for minimum PRESSURE DROP velocity are compared with experimental data from literature and the mean percentage error. MPE for minimum PRESSURE DROP velocity is-9. 89%. It is found that the minimum PRESSURE DROP velocity increases as the solid mass flow, particle size and particle density increase, and decreases as the system total PRESSURE increases.

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بازدید 263

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اطلاعات دوره: 
  • سال: 

    2015
  • دوره: 

    4
تعامل: 
  • بازدید: 

    145
  • دانلود: 

    0
چکیده: 

A MIST ELIMINATOR OR DEMISTER IS TO BE DESIGNED AND DEVELOPED TO REMOVE EXCESSIVE MOISTURE CONTENT FROM A VAPOR STREAM IN A CERTAIN FLOW OR PROCESS. MIST ELIMINATOR CONSISTS OF A SERIES OF PROFILED BAFFLE PLATES THAT REMOVE LIQUID DROPLETS FROM A VAPOR STREAM BY THE INERTIA. SEPARATION EFFICIENCY OF THESE DEVICES IS LARGELY DEPENDENT ON THE GAS VELOCITY, VANE SPACING AND VANE TURNING ANGLES. IN THIS STUDY THE PRESSURE DROP OF SINGLE PHASE TURBULENT FLOW OF THIS TYPE OF MIST ELIMINATOR HAS BEEN INVESTIGATED, USING COMPUTATIONAL FLUID DYNAMIC (CFD) USING COMMERCIAL CFD SOFTWARE FLUENT 6.3 WHILE THE GEOMETRY IS CREATED USING GAMBIT. THE COMPUTED VELOCITY AND DISTRIBUTIONS THROUGH THE GAS STREAM WERE SHOWN IN THE RESULT. FROM THIS STUDY, REDUCTION IN PRESSURE DROP THAT CAN BE ACHIEVED WITH REDUCTION OF 20 VANE IS 38% WITH A GAS VELOCITY OF 16 M/S. PRESSURE DROP OF CURVED VANES PROFILE IS ABOUT 1/8 PRESSURE DROP OF ZIGZAG VANES PROFILE.

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بازدید 145

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نویسنده: 

Yavary M. | NAGHIZADEH A.

اطلاعات دوره: 
  • سال: 

    2014
  • دوره: 

    8
تعامل: 
  • بازدید: 

    119
  • دانلود: 

    0
چکیده: 

ONE OF THE IMPORTANT INDUSTRIAL APPLICATIONS FOR CYCLONE IS CEMENT PRODUCTION PROCESS. AT CEMENT PRODUCTION PROCESS, CYCLONES ARE USED FOR SEPARATION OF GAS AND SOLID PHASE, ALSO FOR HEAT TRANSFER BETWEEN THEM. DUE TO ITS INDUSTRIAL RELEVANCE, A LARGE NUMBER OF EXPERIMENTAL, THEORETICAL AND COMPUTATIONAL STUDIES HAVE BEEN REPORTED IN THE LITERATURE FOR UNDERSTANDING AND PREDICTING THE PERFORMANCE OF CYCLONES IN TERMS OF PRESSURE LOSS AND COLLECTION EFFICIENCY. THESE CYCLONE PERFORMANCE PARAMETERS ARE GOVERNED BY MANY OPERATIONAL PARAMETERS (E.G., THE GAS FLOW RATE AND TEMPERATURE) AND GEOMETRICAL PARAMETERS. THIS STUDY FOCUSES ONLY ON THE EFFECT OF THE PROCESS PARAMETERS ON THE PRESSURE DROP AS IMPORTANT PARAMETERS OF THE CYCLONE PERFORMANCE. COMPARISON OF PRESSURE DROPS PREDICTED BY DIFFERENT THEORETICAL MODELS AND THE EXPERIMENTAL MEASUREMENTS VERIFIED THAT SOME MATHEMATICAL MODELS GAVE PRESSURE DROP PREDICTIONS THAT WERE CLOSE TO THE EXPERIMENTAL DATA, AND THE THEORETICAL PREDICTIONS OF PRESSURE DROP OBTAINED BY THEM ARE IN FAIR AGREEMENT WITH FIELD MEASUREMENTS.

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اطلاعات دوره: 
  • سال: 

    2008
  • دوره: 

    5
تعامل: 
  • بازدید: 

    145
  • دانلود: 

    0
چکیده: 

PRESSURE DROP MEASUREMENTS FOR HORIZONTAL STRATIFIED TWO-PHASE FLOW OF AIR WATER HAVE BEEN PERFORMED IN A CHANNEL WITH 5.33M LENGTH, 0.20M WIDTH, AND 0.1M HEIGHT. THE GAS AND LIQUID REYNOLDS NUMBERS WERE VARIED IN THE 54000-87000 AND 13000-23000 RANGES, RESPECTIVELY. A CORRELATION WAS PROPOSED FOR PREDICTING PRESSURE DROP IN HORIZONTAL STRATIFIED TWO PHASE FLOW. PREDICTIONS OF THE CORRELATION PROPOSED IN THIS WORK WERE COMPARED WITH EXPERIMENTAL DATA AND SHOWED MUCH BETTER AGREEMENT COMPARED TO FRIEDEL EQUATION.

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نویسندگان: 

ASADOLLAHI M.

اطلاعات دوره: 
  • سال: 

    2019
  • دوره: 

    16
  • شماره: 

    3
  • صفحات: 

    84-92
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    265
  • دانلود: 

    0
چکیده: 

Although two-phase flow is frequently encountered in various locations of the process plants, there is no a generally accepted and verified twophase flow model that may be used to size lines for such conditions. An obvious example is condensate water return lines. The API method used in this study is based on the homogeneous equilibrium flow assumption, that is, equal velocity and equal temperature in both liquid and vapor phases. Moreover, DIERS method was used to verify and clarify the HEM approach to calculating the PRESSURE DROP in twophase regimes. The objective of this study is to introduce a solution for process lines design during different flashing scenarios. Applying API method, this study can find the two-phase line PRESSURE DROP and upstream PRESSURE, while, by using DIERS method, one could realize that for a specified length of pipe how much two-phase flow could pass through when the PRESSURE DROP is just the same as that in the API model.

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نویسندگان: 

ZIVDAR M. | RAHIMI R. | HAGHSHENAS FARD M. | NASR M.

اطلاعات دوره: 
  • سال: 

    2005
  • دوره: 

    2
  • شماره: 

    2
  • صفحات: 

    64-71
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    367
  • دانلود: 

    0
چکیده: 

KATAPAK-S is a type of structured catalytic packing, which is used in reactive distillation processes. The DRY PRESSURE DROP characteristic (the PRESSURE DROP in the absence of liquid flow) is of significant importance for the investigation of process hydrodynamics. In this paper, the DRY PRESSURE DROP within the catalyst packed channels of KATAPAK-S has been investigated using Computational Fluid Dynamics (CFD).Results of the CFD simulations were validated using experimental PRESSURE DROP data and empirical correlations. The CFD results showed an excellent agreement with theoretical and experimental data.

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بازدید 367

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اطلاعات دوره: 
  • سال: 

    1389
  • دوره: 

    6
  • شماره: 

    2 (پیاپی 20) (انتقال حرارت و پیشرانش)
  • صفحات: 

    53-60
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    1374
  • دانلود: 

    476
چکیده: 

در این مطالعه به بررسی افت فشار جریان جوششی اجباری مبرد R-134a درون لوله های افقی پهن شده پرداخته می شود. به این منظور، لوله های مسی گرد با قطر خارجی 9.52 میلی متر به چهار میزان متفاوت با ارتفاع داخلی 8.2، 8.3، 5.5 و 6.6 میلی متر پهن می شوند. دستگاه مورد استفاده در این بررسی یک سیستم تبرید تراکمی بخار مجهز به کلیه وسایل اندازه گیری مورد نیاز می باشد. این سیستم شامل سه تبخیر کننده گرم شونده با گرمگن الکتریکی می باشد که به ترتیب تبخیرکننده اولیه، تبخیرکننده آزمایش و تبخیرکننده ثانویه نامیده می شوند. رابطه ای برای محاسبه افت فشار جریان جوششی سیال در لوله های پهن شده ارایه شده که داده های آزمایشگاهی مطالعه حاضر را با دقت 20%± پیش بینی می کند. داده های آزمایشگاهی با روابط موجود برای پیش بینی افت فشار در لوله های پهن شده مقایسه شده اند. نتایج تجربی حاصله نشان می دهد که پهن کردن مقطع لوله باعث افزایش افت فشار نسبت به لوله گرد مشابه می شود. در بدترین حالت افت فشار، جریان جوششی درون لوله پهن شده افقی تا 600% نسبت به لوله گرد مشابه افزایش می یابد.

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نویسندگان: 

اطلاعات دوره: 
  • سال: 

    1388
  • دوره: 

    3
  • شماره: 

    8
  • صفحات: 

    0-0
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    462
  • دانلود: 

    179
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چکیده: 

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