Aerodynamic and acoustical effects caused by placing two prefabricated duct silencers in series

2021 ◽  
Vol 263 (1) ◽  
pp. 5664-5670
Author(s):  
Karl Peterman
Keyword(s):  
Pressure Drop ◽  
Insertion Loss ◽  
Air Conditioning ◽  
Common Duct ◽  
Test Facility ◽  
Present Information ◽  
In Series ◽  
Control Designs ◽  
High Sound ◽  
Attenuation Values

It once was not uncommon to find ductborne noise control designs and recommendations that would attempt to provide high sound attenuation values, especially for problematic lower frequencies, by using a pair of prefabricated duct silencers in series with one another, sometimes immediately adjacent but typically separated by some distance. Similarly, heating, ventilating, and air-conditioning (HVAC) duct silencers are occasionally required to accommodate fire dampers or access sections that effectively break up the silencer along its length, creating an empty gap between the noise-attenuating internal elements. Typical published performance characteristics of prefabricated duct silencers do not include effects from the use of additional silencers nearby and little information is available in common duct design and application literature. This paper will present information from a series of tests of various silencers in different configurations and spacings in an aero-acoustic test facility that will help describe the effects on insertion loss, generated noise, and pressure drop.

Scaling analysis of core pressure drop in reduced height integral test facility

Kerntechnik ◽  
2018 ◽  
Vol 83 (3) ◽  
pp. 178-180
Author(s):  
P. Ju ◽  
B. Long ◽  
L. Li ◽  
Q. Su ◽  
X. Wu ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Test Facility ◽  
Scaling Analysis ◽  
Integral Test ◽  
Reduced Height

A 3D Unsteady Flow Analysis in a Doubly Constricted Tube

2000 ◽  
Author(s):  
B. V. Rathish Kumar ◽  
T. Yamaguchi ◽  
H. Liu ◽  
R. Himeno
Keyword(s):  
Pressure Drop ◽  
Unsteady Flow ◽  
Stokes Equations ◽  
Vortex Formation ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
In Series ◽  
3D Unsteady Flow

Abstract Unsteady flow dynamics in a doubly constricted vessel is analyzed by using a time accurate Finite Volume solution of three dimensional incompressible Navier-Stokes equations. Computational experiments are carried out for various values of Reynolds number in order to assess the criticality of multiple mild constrictions in series and also to bring out the subtle 3D features like vortex formation. Studies reveal that pressure drop across a series of mild constrictions can get physiologically critical. Further this pressure drop is found to be sensitive to the spacing between the constrictions and also to the oscillatory nature of the inflow profile.

scholarly journals Design Evaluation for a Finned-Tube CO2 Gas Cooler in Residential Applications

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2428 ◽  
Author(s):  
Charalampos Alexopoulos ◽  
Osama Aljolani ◽  
Florian Heberle ◽  
Tryfon C. Roumpedakis ◽  
Dieter Brüggemann ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Air Conditioning ◽  
Design Procedure ◽  
Finned Tube ◽  
Co2 Gas ◽  
Ambient Temperatures ◽  
Overall Heat Transfer Coefficient

Towards the introduction of environmentally friendlier refrigerants, CO2 cycles have gained significant attention in cooling and air conditioning systems in recent years. In this context, a design procedure for an air finned-tube CO2 gas cooler is developed. The analysis aims to evaluate the gas cooler design incorporated into a CO2 air conditioning system for residential applications. Therefore, a simulation model of the gas cooler is developed and validated experimentally by comparing its overall heat transfer coefficient. Based on the model, the evaluation of different numbers of rows, lengths, and diameters of tubes, as well as different ambient temperatures, are conducted, identifying the most suitable design in terms of pressure losses and required heat exchange area for selected operational conditions. The comparison between the model and the experimental results showed a satisfactory convergence for fan frequencies from 50 to 80 Hz. The absolute average deviations of the overall heat transfer coefficient for fan frequencies from 60 to 80 Hz were approximately 10%. With respect to the gas cooler design, a compromise between the bundle area and the refrigerant pressure drop was necessary, resulting in a 2.11 m2 bundle area and 0.23 bar refrigerant pressure drop. In addition, the analysis of the gas cooler’s performance in different ambient temperatures showed that the defined heat exchanger operates properly, compared to other potential gas cooler designs.

Influence of Electric Fields on Flow of Liquid Crystal Mixture in a Circular Tube With Electrode Surface

2003 ◽  
Author(s):  
Tetsuhiro Tsukiji ◽  
Tsuyoshi Mitani
Keyword(s):  
Liquid Crystal ◽  
Pressure Drop ◽  
Electric Fields ◽  
Pulse Width Modulation ◽  
Circular Tube ◽  
Pulse Frequency ◽  
Open Loop ◽  
Test Facility ◽  
Pulse Frequency Modulation ◽  
Crystal Mixture

Liquid crystal is one of functional fluids to control an apparent viscosity using an electric field intensity. It is also called ER (Electro-rheological) fluids. In the present experiment a liquid crystal mixture made of some kinds of the nematic liquid crystal is used. The responses of the pressure drop are examined when the liquid crystal mixture flows in a circular tube with the electrode walls on some parts of the inner surface of the tube for the constant flow rates. The four pair of the electrode is used and the voltages are added in the peripheral direction. When the voltages are applied on the liquid crystal mixture and removed, the pressure responses of the inlet of the circular tube are measured with the pressure transducer. On the other hand, the pulse-wave voltages are added to the electrodes to control the pressure drop using the pulse width modulation or the pulse frequency modulation. The diameter of the circular tube is 1.0mm. The isotropic-nematic transition is 90.0°C and smectic-nematic transition is −44.0°C for the liquid crystal mixture. The open-loop test facility with the liquid crystal mixture is set in a pyrostat to keep the temperature constant.

Overall Optimization and Exergy Analysis of an Air Conditioning System Using a Series-Series Counterflow Arrangement of Water Chillers

2019 ◽  
Vol 27 (04) ◽  
pp. 1950034 ◽  
Author(s):  
Nguyen Minh Phu
Keyword(s):  
Air Conditioning ◽  
Exergy Analysis ◽  
Cooling Tower ◽  
Exergy Efficiency ◽  
Air Conditioning System ◽  
In Series ◽  
Main Components ◽  
Compressor Power ◽  
Cooling Coil ◽  
Optimal Set

When water chillers are arranged in series-series counterflow (SSCF), the compressor lift of each chiller is decreased in comparison with that of water chillers in parallel. This means that the compressor power of SSCF chillers is lower than that of parallel chillers. In this paper, models of the main components in an air conditioning system were developed and verified to predict the behaviors of the whole system with respect to SSCF chillers. The results showed that performance was maximized with three SSCF chillers when the system was operated with normal set points. The performance was further improved to 26% and decreased with the number of SSCF chillers when the system was operated with optimal set points. The SSCF chiller system also demonstrated higher exergy efficiency regardless of the number of SSCF chillers. The irreversibility of components in SSCF chillers was rather low. However, the irreversibility of the cooling tower and cooling coil was slightly higher and lower, respectively, than those in the parallel chiller system.

Experimental Apparatus for Measuring in Tube Condensation Heat Transfer Coefficient and Pressure Drop Using Smooth and Micro-Fin Tubes for HFC Refrigerants

2008 ◽  
Author(s):  
Pradeep A. Patil ◽  
S. N. Sapali
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Condensation Heat Transfer ◽  
Test Facility ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Fin Tube ◽  
Condensation Heat Transfer Coefficient

An experimental test facility is designed and built to calculate condensation heat transfer coefficients and pressure drops for HFC-134a, R-404A, R-407C, R-507A in a smooth and micro-fin tube. The main objective of the experimentation is to investigate the enhancement in condensation heat transfer coefficient and increase in pressure drop using micro-fin tube for different condensing temperatures and further to develop an empirical correlation for heat transfer coefficient and pressure drop, which takes into account the micro-fin tube geometry, variation of condensing temperature and temperature difference (difference between condensing temperature and average temperature of cooling medium). The experimental setup has a facility to vary the different operating parameters such as condensing temperature, cooling water temperature, flow rate of refrigerant and cooling water etc and study their effect on heat transfer coefficients and pressure drops. The hermetically sealed reciprocating compressor is used in the system, thus the effect of lubricating oil on the heat transfer coefficient is taken in to account. This paper reports the detailed description of design and development of the test apparatus, control devices, instrumentation, and the experimental procedure. It also covers the comparative study of experimental apparatus with the existing one from the available literature survey. The condensation and pressure drop of HFC-134a in a smooth tube are measured and obtained the values of condensation heat transfer coefficients for different mass flux and condensing temperatures using modified Wilson plot technique with correlation coefficient above 0.9. The condensation heat transfer coefficient and pressure drop increases with increasing mass flux and decreases with increasing condensing temperature. The results are compared with existing available correlations for validation of test facility. The experimental data points have good association with available correlations except Cavallini-Zecchin Correlation.

Computer-assisted optimization of selectivity by tuning temperature and carrier gas pressure drop in two GC capillary columns coupled in series

1990 ◽  
Vol 102 (1-3) ◽  
pp. 1-10 ◽  
Author(s):  
Eva Benická ◽  
Ján Krupčik ◽  
Peter Kuljovský ◽  
Dušan Repka ◽  
Ján Garaj
Keyword(s):  
Pressure Drop ◽  
Capillary Columns ◽  
Gas Pressure ◽  
Computer Assisted ◽  
Carrier Gas ◽  
In Series

Steady Flow Through a Double Converging-Diverging Tube Model for Mild Coronary Stenoses

1989 ◽  
Vol 111 (3) ◽  
pp. 212-221 ◽  
Author(s):  
S. C. van Dreumel ◽  
G. D. C. Kuiken
Keyword(s):  
Pressure Drop ◽  
Reynolds Numbers ◽  
Velocity Profiles ◽  
Tube Model ◽  
Mean Flow ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
In Series ◽  
Coronary Stenoses ◽  
Converging Angle

Velocity profiles and the pressure drop across two mild (62 percent) coronary stenoses in series have been investigated numerically and experimentally in a perspex-tube model. The mean flow rate was varied to correspond to a Reynolds number range of 50–400. The pressure drop across two identical (62 percent) stenoses show that for low Reynolds numbers the total effect of two stenoses equals that of two single stenoses. A reduction of 10 percent is found for the higher Reynolds numbers investigated. Numerical and experimental results obtained for the velocity profiles agree very well. The effect of varying the converging angle of a single mild (62 percent) coronary stenosis on the fluid flow has been determined numerically using a finite element method. Pressure-flow relation, especially with respect to relative short stenoses, is discussed.

Temperature Dependent DC and RF Performance of n-GaN Schottky Diode: A Numerical Approach

2014 ◽  
Vol 895 ◽  
pp. 439-443
Author(s):  
Tarriq Munir ◽  
Azlan Abdul Aziz ◽  
Mat Johar Abdullah ◽  
Mohd Fadzil Ain
Keyword(s):  
Schottky Barrier ◽  
Schottky Diode ◽  
Insertion Loss ◽  
Ideality Factor ◽  
Series Resistance ◽  
Thermionic Emission ◽  
Numerical Approach ◽  
Temperature Dependent ◽  
In Series ◽  
Rf Performance

This paper reports the temperature dependent DC and RF characteristics of n-GaN Schottky diode simulated using Atlas/Blaze developed by Silvaco. It was found that as the temperature increases from 300K to 900K the forward current decreases due to lowering of the Schottky barrier with an increase in series-resistance and ideality factor. These observations indicates that tunneling behavior dominates the current flow rather than thermionic emission. Furthermore, the breakdown voltage decreases in reverse bias and insertion loss for RF behavior increases with respect to temperature due to the increase in capacitance near diode junction.Keywords: Atlas/Blaze, Schottky barrier, series resistance, ideality factor, insertion loss.

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