scholarly journals Numerical Study on Effects of Pipeline Geometric Parameters on Release Characteristics of Gas Extinguishing Agent

Symmetry ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1766
Author(s):  
Quanwei Li ◽  
Zongyu Li ◽  
Ruiyu Chen ◽  
Zhaojun Zhang ◽  
Hui Ge ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Release Time ◽  
Pipeline System ◽  
Average Pressure ◽  
Fire Extinguishing ◽  
Drop Rate ◽  
Peak Value

In order to guide the optimization design of the pipeline network of the aircraft-fixed gas fire extinguishing system and improve its fire extinguishing performance, FLUENT software was used to simulate the influence of pipeline parameters such as diameter, length, and roughness on the release characteristics of the fire extinguishing agent. It can be found that the extinguishing agent can be divided into liquid and vapor extinguishing agents in the fire extinguishing pipeline system during the release. The spatial distribution and proportion of the liquid and vapor extinguishing agents are asymmetric. Results show that the peak value of the pressure drop rate (dPmax) has a good quadratic function relationship with the pipeline diameter (D) and the functional relationship is dPmax=−22.224+2.782D+0.089D2, which means that the peak value increased significantly with the increase in the pipeline diameter. Moreover, when the pipeline diameter is 25 mm, the average pressure drop rate of the vessel is about 35.02 MPa/s, which is 5.97 times the value of the average pressure drop rate when the pipeline diameter is 10 mm. With the increase in the pipeline diameter, the release time decreases significantly, the mass flow rate increases obviously, while the gasification ratio decreases rapidly at first and then increases slightly. The pipeline length also has a significant influence on the release characteristics of the extinguishing agent. With the increase in the pipeline length, the release time and the gasification ratio increase linearly, while the mass flow rate decreases linearly. Compared with the pipeline diameter and pipeline length, the influence of the pipeline roughness on the release characteristics of the extinguishing agent is weak. With the increase in the pipeline roughness, the release time and the gasification ratio of the extinguishing agent increases slowly, while the mass flow rate decreases slowly.

scholarly journals Numerical Study on Flow and Release Characteristics of Gas Extinguishing Agent under Different Filling Pressure and Amount Conditions

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1683
Author(s):  
Quanwei Li ◽  
Hui Ge ◽  
Renming Pan ◽  
Zhaojun Zhang ◽  
Ruiyu Chen
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Study ◽  
Filling Pressure ◽  
Release Time ◽  
Second Phase ◽  
Release Process ◽  
Fire Extinguishing ◽  
Fire Extinguishing System

The fire-extinguishing system is an indispensable fire-protection facility on the aircraft. In order to guide weight reduction of the aircraft’s fixed gas fire-extinguishing system by improving its release efficiency, so as to improve fuel economy and reduce carbon emissions, the influence of filling pressures and filling amounts on the release efficiency of gas extinguishing agent along pipelines were studied based on numerical simulations. The release process of the fire-extinguishing system was analyzed. The effects of the filling pressure and filling amount of Halon 1301 agent on the release characteristics, such as release time, mass flow rate, and gasification ratio, were studied. Results show that the release process can be divided into three major phases, which are firstly the initial rapid filling of the pipeline, secondly the concentrated release of the liquid extinguishing agent, and thirdly the gas ejection along the pipeline. The second phase can also be subdivided into two stages: the outflow of the liquid extinguishing agent from the bottle, and the release of the residual liquid extinguishing agent along the pipeline. The release characteristics of the fire-extinguishing agent were obviously affected by the filling pressures and filling amounts. When the filling pressure was relatively low (2.832 MPa), increasing the filling pressure can significantly increase the mass flow rate, shorten the release time, and reduce the gasification ratio of the extinguishing agent during the release processes. Under the same filling pressure, with the increase of the filling amount of the extinguishing agent, the release times and the gasification ratio showed a linear increase trend, while the average mass flow rates showed a linear decrease trend.

Research on Two-Phase Flow Instability in Evaporator of Refrigeration System

2010 ◽  
Author(s):  
Nan Liang ◽  
Changqing Tian ◽  
Shuangquan Shao
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Density Wave ◽  
Phase Flow ◽  
Constant Mass ◽  
Refrigeration System ◽  
Two Phase

As one kind of fluid machinery related to the two-phase flow, the refrigeration system encounters more problems of instability. It is essential to ensure the stability of the refrigeration systems for the operation and efficiency. This paper presents the experimental investigation on the static and dynamic instability in an evaporator of refrigeration system. The static instability experiments showed that the oscillatory period and swing of the mixture-vapor transition point by observation with a camera through the transparent quartz glass tube at the outlet of the evaporator. The pressure drop versus mass flow rate curves of refrigerant two phase flow in the evaporator were obtained with a negative slope region in addition to two positive slope regions, thus making the flow rate a multi-valued function of the pressure drop. For dynamic instabilities in the evaporation process, three types of oscillations (density wave type, pressure drop type and thermal type) were observed at different mass flow rates and heat fluxes, which can be represented in the pressure drop versus mass flow rate curves. For the dynamic instabilities, density wave oscillations happen when the heat flux is high with the constant mass flow rate. Thermal oscillations happen when the heat flux is correspondingly low with constant mass flow rate. Though the refrigeration system do not have special tank, the accumulator and receiver provide enough compressible volume to induce the pressure drop oscillations. The representation and characteristic of each oscillation type were also analyzed in the paper.

scholarly journals Analytical and Experimental Investigation of a Plate Fin Heat Exchanger at Cryogenics Temperature

2021 ◽  
Vol 39 (4) ◽  
pp. 1225-1235
Author(s):  
Ajay K. Gupta ◽  
Manoj Kumar ◽  
Ranjit K. Sahoo ◽  
Sunil K. Sarangi
Keyword(s):  
Heat Exchanger ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cryogenic Temperature ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Compact Size

Plate-fin heat exchangers provide a broad range of applications in many cryogenic industries for liquefaction and separation of gasses because of their excellent technical advantages such as high effectiveness, compact size, etc. Correlations are available for the design of a plate-fin heat exchanger, but experimental investigations are few at cryogenic temperature. In the present study, a cryogenic heat exchanger test setup has been designed and fabricated to investigate the performance of plate-fin heat exchanger at cryogenic temperature. Major parameters (Colburn factor, Friction factor, etc.) that affect the performance of plate-fin heat exchangers are provided concisely. The effect of mass flow rate and inlet temperature on the effectiveness and pressure drop of the heat exchanger are investigated. It is observed that with an increase in mass flow rate effectiveness and pressure drop increases. The present setup emphasis the systematic procedure to perform the experiment based on cryogenic operating conditions and represent its uncertainties level.

Effect of Mass Flow Rate on Dryer Room Radiator Pressure Drop and Heat Transfer

2016 ◽  
Vol 836 ◽  
pp. 102-108
Author(s):  
Mirmanto ◽  
Emmy Dyah Sulistyowati ◽  
I Ketut Okariawan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Electrical Power ◽  
Maximum Temperature ◽  
Inlet Temperature ◽  
Mass Flow Rates ◽  
Room Model

In the rainy season, in tropical countries, to dry stuffs is difficult. Using electrical power or fossil energy is an expensive way. Therefore, it is wise to utilize heat waste. A device that can be used for this purpose is called radiator. The effect of mass flow rate on pressure drop and heat transfer for a dryer room radiator have been experimentally investigated. The room model size was 1000 mm x 1000 mm x 1000 mm made of plywood and the overall radiator dimension was 360 mm x 220 mm x 50 mm made of copper pipes with aluminium fins. Three mass flow rates were investigated namely 12.5 g/s, 14 g/s and 16.5 g/s. The water temperature at the entrance was increased gradually and then kept at 80°C. The maximum temperature reached in the dryer room was 50°C which was at the point just above the radiator. The effect of the mass flow rate on the room temperature was insignificant, while the effect on the pressure drop was significant. Moreover, the pressure drop decreased as the inlet temperature increased. In general, the radiator is recommended to be used as the heat source in a dryer room.

Design and Optimization of the Restrictor of a Race Car

2015 ◽  
Author(s):  
Prithvi Raj Kokkula ◽  
Shashank Bhojappa ◽  
Selin Arslan ◽  
Badih A. Jawad
Keyword(s):  
Fluid Dynamics ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Air Flow ◽  
Intake Manifold ◽  
Maximum Pressure ◽  
Cross Sectional ◽  
Formula Sae

Formula SAE is a student competition organized by SAE International. The team of students design, manufacture and race a car. Restrictions are imposed by the Formula SAE rules committee to restrict the air flow into the intake manifold by putting a single restrictor of 20 mm. This rule limits the maximum engine power by reducing the mass flow rate flowing to the engine. The pull is greater at higher rpms and the pressure created inside the cylinder is low. As the diameter of the flow path is reduced, the cross sectional area for flow reduces. For cars running at low rpm when the engine requires less air, the reduction in area is compensated by accelerated flow of air through the restrictor. Since this is for racing purpose cars here are designed to run at very high rpms where the flow at the throat section reach sonic velocities. Due to these restrictions the teams are challenged to come up with improved restrictor designs that allow maximum pressure drop across the restrictor’s inlet and outlet. The design considered for optimizing a flow restrictor is a venturi type having 20 mm restriction between the inlet and the outlet complying with the rules set by Formula SAE committee. The primary objective of this work is to optimize the flow restriction device that achieves maximum mass flow and minimum pull from the engine. This implies the pressure difference created due to the cylinder pressure and the atmospheric pressure at the inlet should be minimum. An optimum flow restrictor is designed by conducting analysis on various converging and diverging angles and coming up with an optimum value. Venturi type is a tubular pipe with varying diameter along its length, through which the fluid flows. Law of governing fluid dynamics states that the “Velocity of the fluid increases as it passes through the constriction to satisfy the principle of continuity”. An equation can be derived from the combination of Bernoulli’s equation and Continuity equation for the pressure drop due to venturi effect. [1]. A Computational Fluid Dynamics (CFD) tool is used to calculate the minimum pressure drop across the restrictor by running a series of analysis on various converging and diverging angles and calculating the pressure drop. As a result, an optimum air flow restrictor is achieved that maximizes the mass flow rate and minimizes the engine pull.

The Effects of Tip Clearance on Performance of a Heavy Duty Multi Stages Axial Turbine

2012 ◽  
Author(s):  
Mohammad Reza Shirzadi ◽  
Hossein Saeidi
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Large Scale ◽  
Tip Clearance ◽  
Heavy Duty ◽  
Penetration Length ◽  
Axial Turbine ◽  
Commercial Code

In this article aerodynamic effects of tip clearance on a heavy duty axial turbine are studied. Three different tip clearances are considered for each rotor. For simplicity, a simple tip profile is assumed and cooling air is not modeled. Aerodynamic behavior of all stages is studied in terms of polytropic efficiency, leakage mass flow, secondary and total losses, penetration length, and total mass flow rate for different pressure ratios. Also three well established correlations of tip clearance loss are compared with CFD results to obtain the best model for performance calculation of such a large-scale turbine. The steady states, viscous and compressible flow governing equations representing the flow field with k-epsilon turbulence model are solved using commercial code ANSYS CFX.12. Useful data are presented to predict the variation of efficiency of each individual rotor, as well as entire turbine, as a function of relative tip gap (k/h). This information may be useable in design and troubleshooting. According to the results, even though pressure drop in rear stages across tip gap is lower than pressure drop in front stages, leakage mass flow rate is considerably high for this LP stages. Consequently, tip clearance losses of rear stages have significant effect on the entire turbine efficiency.

Thermal and Hydraulic Performances of Porous Microchannel Heat Sink using Nanofluids

2021 ◽  
pp. 1-32
Author(s):  
Zahir Uddin Ahmed ◽  
Md. Roni Raihan ◽  
Omidreza Ghaffari ◽  
Muhammad Ikhlaq
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Friction Factor ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Sink ◽  
Hydraulic Performance ◽  
Microchannel Heat Sink ◽  
Nanoparticle Concentration

Abstract Microchannel heat sink is an effective method in compact and faster heat transfer applications. This paper numerically investigates thermal and hydraulic characteristics of a porous microchannel heat sink (PMHS) using various nanofluids. The effect of porosity, inlet velocity and nanoparticle concentration on thermal-hydraulic performance is systematically examined. The result shows a significant temperature increase (40°C) of the coolant in the porous zone. The pressure drop reduces by 35% for γ = 0.32 compared to the non-porous counterpart, and this reduction of pressure significantly continues when γ further increases. The pressure drop with win is linear for PMHS with nanofluids, and the change in pressure drop is steeper for nanofluids compared to their base fluids. The average heat transfer coefficients increases about 2.5 times for PMHS, and a further increase of 6% in is predicted with the addition of nanoparticle. The average Nusselt number increases non-linearly with Re for PMHS. The friction factor reduces by 50% when γ increases from 0.32 to 0.60, and the effect of nanofluid on friction factor is insignificant beyond the mass flow rate of 0.0004 kg/s. Whilst Cu and CuO nanoparticles help to dissipate the larger amount of heat from the microchannel, Al2O3 nanoparticle appears to have a detrimental effect on heat transfer. The thermal-hydraulic performance factor strongly depends on the nanoparticles, and it slightly decreases with the mass flow rate. The increase of nanoparticle concentration, in general, enhances both h and ΔP linearly for the range considered.

Experimental Research on Pulsating Two-Phase Flow Pressure Drop Characteristics in Horizontal Rectangular Channel

2014 ◽  
Author(s):  
Siqi Zhang ◽  
Puzhen Gao
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Phase Flow ◽  
Two Phase ◽  
Mean Values ◽  
Water Mass Flow Rate

In spite of most previous studies since 1970, the theory of pulsating pipe flows supported by experimental investigations has not yet completed in comparison with the well-defined theory of steady pipe flows. Therefore, it seems that there is much to be done about experimental research in this field. In order to determine the resistance characteristics of two-phase flow under pulsatile conditions, an experimental investigation on two-phase flow with periodically fluctuating flow rates in a narrow rectangular channel is carried out. A frequency inverter is used to obtain experimental conditions with different fluctuating frequencies, amplitudes and mean values of water mass flow rate. After obtaining experimental results, comparisons between experimental frictional pressure drop values and theoretical calculations have been done. Two-phase flow on pulsating conditions is far more complicated than that on steady conditions because pulsating flow is composed of two parts: a steady component and a superimposed periodical time varying component called oscillation. In this paper, the influence of different fluctuating frequencies, amplitudes and mean values of liquid and gas mass flow rate on two-phase flow pressure drop characteristics is also discussed. The results show that the total pressure drop and water mass flow rate change with the same fluctuating period except for a phase difference. The phase lag also changes with the fluctuating frequencies and amplitude. The accelerating pressure drop changes dramatically in a fluctuating period, especially at the end of acceleration. Also, the time when the acceleration pressure drop has its maximum value lags the time when the acceleration reaches its peak, mainly because of the inertial of the fluid.

RANS-Based CFD Calculation for Pressure Drop and Mass Flow Rate Distribution in an MTR Fuel Assembly

2020 ◽  
pp. 1-18
Author(s):  
N. L. Scuro ◽  
G. Angelo ◽  
E. Angelo ◽  
P. E. Umbehaun ◽  
W. M. Torres ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Fuel Assembly ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rate Distribution
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