Theoretical Model of Buoyancy-Induced Flow in Rotating Cavities

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
J. Michael Owen ◽  
Hui Tang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Average Mass ◽  
The Core ◽  
Nusselt Numbers ◽  
Ekman Layers ◽  
Induced Flow ◽  
Source Sink ◽  
Buoyancy Induced Flow

The Ekman-layer equations, which have previously been solved for isothermal source–sink flow in a rotating cavity, are derived for buoyancy-induced flow. Although the flow in the inviscid core is three-dimensional and unsteady, it is assumed that the flow in the Ekman layers is axisymmetric and steady; and, as for source–sink flow, the average mass flow rate in the Ekman layers is assumed to be invariant with radius. In addition, it is assumed that the flow in the core is adiabatic, and consequently the core temperature increases with radius and with rotational speed. Approximate solutions are obtained for laminar flow, and it is shown that the Nusselt numbers for the rotating disks and the mass flow rate in the Ekman layers are proportional to Grc1/4, where Grc is a Grashof number based on the rotational Reynolds number and the temperature difference between the disk and the core. The equation for the Nusselt numbers, which includes two empirical constants, depends strongly on the radial distribution of the temperature of the disks.

Micropump With Six Vibrating Membranes: Design Analysis

2008 ◽  
Author(s):  
Kittisak Koombua ◽  
Ramana M. Pidaparti ◽  
P. Worth Longest ◽  
Gary M. Atkinson
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Head ◽  
Maximum Pressure ◽  
Operating Cycle ◽  
Average Mass ◽  
Volume Method ◽  
Novel Design ◽  
Membrane Displacement

In this study, a novel design of multiple vibrating membrane micropump has been investigated. The micropump is composed of six membranes and three nozzle/diffuser elements. The membranes were vibrated out-of-phase simultaneously to create pressure difference in the pump chamber. The characteristics of this micropump were analyzed using the finite volume method. The commercial computational fluid dynamics software, FLUENT, with the dynamic mesh algorithm was employed to study velocity field and flow rate during the operating cycle. The simulation results showed that the movement of these membranes combined with the rectification behavior of three nozzle/diffuser elements can minimize back flow and improve net flow in one direction. The average mass flow rate from the micropump increased when the maximum membrane displacement and membrane frequency increased. However, the average mass flow rate from the micropump decreased when pressure head increased. Increases in maximum pressure head were associated with increases in membrane frequency.

Numerical Simulation of the Nuclear Main Pump in the Sbloca

2012 ◽  
Vol 455-456 ◽  
pp. 314-319 ◽  
Author(s):  
Jian Yu ◽  
Fu Tian ◽  
Ming Ma ◽  
Xiao Fang Wang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Power Supply ◽  
Half Time ◽  
Blade Surface ◽  
Pump Unit ◽  
Operation Condition ◽  
The Core ◽  
Time Required

In this paper, the transient of the flow field of the nuclear main pump has been analyzed in the SBLOCA and the half mass flow rate time is obtained through the simulation. The results of the simulation show that, as nuclear main pump runs down, the mass flow rate and head of the pump drops as well. The blade surface pressure is not evenly distributed. The blade bears the force of the flow. So Pump unit should have sufficient moment of inertia, so that when the reactor in an emergency shuts down caused by the failure of power supply, nucleate burning down can be avoided by cooling the core. On the braking operation condition, the half mass flow rate time required should be guaranteed. Through simulation, we find when the half time is equal to 10s, the half mass flow rate time is about 4.6s Though it is a little shorter than 5s required, the AP1000 model selected basically meet the idle requirement.

scholarly journals Modeling And Fouling Detection Of The Aircraft Environmental Control System Heat Exchanger

2021 ◽  
Author(s):  
Shoaib A. Shah
Keyword(s):  
Control System ◽  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Environmental Control ◽  
Cross Flow ◽  
The State ◽  
The Core ◽  
On Line

A Diagnostics, Prognostics and Health Management (DPHM) solution is proposed for the operation of the aircraft environmental control system (ECS) cross flow heat exchanger. In particular, a dynamic model is derived and applied to on-line detection of fouling in the aircraft ECS cross flow plate-and-fin heat exchanger. Predictive maintenance actions can be scheduled as per the on-line detected fouling status of the specific component, supporting condition based maintenance. The heat exchanger model is of the lumped state space form, where the state consists of the core and fin temperatures. The ratios of the thermal capacities of the masses of the two air streams to the thermal capacity of the core itself are neglected, and the model parameters' functional dependency on mass flow rate and influence of secondary surfaces (fins) are taken into account in order to accurately describe the dynamic behavior of the heat exchanger. Since the parameters are functions of mass flow rate, as are the core and fin temperatures, and the model is nonlinear in the state variables, an extended Kalman filtering (EKF) algorithm is applied to estimate the state dependent parameters. The effectiveness of the model's formulation is supported by the quality of the corresponding predicted results, which in turn are validated via experimental tests.

scholarly journals Modeling And Fouling Detection Of The Aircraft Environmental Control System Heat Exchanger

2021 ◽  
Author(s):  
Shoaib A. Shah
Keyword(s):  
Control System ◽  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Environmental Control ◽  
Cross Flow ◽  
The State ◽  
The Core ◽  
On Line

A Diagnostics, Prognostics and Health Management (DPHM) solution is proposed for the operation of the aircraft environmental control system (ECS) cross flow heat exchanger. In particular, a dynamic model is derived and applied to on-line detection of fouling in the aircraft ECS cross flow plate-and-fin heat exchanger. Predictive maintenance actions can be scheduled as per the on-line detected fouling status of the specific component, supporting condition based maintenance. The heat exchanger model is of the lumped state space form, where the state consists of the core and fin temperatures. The ratios of the thermal capacities of the masses of the two air streams to the thermal capacity of the core itself are neglected, and the model parameters' functional dependency on mass flow rate and influence of secondary surfaces (fins) are taken into account in order to accurately describe the dynamic behavior of the heat exchanger. Since the parameters are functions of mass flow rate, as are the core and fin temperatures, and the model is nonlinear in the state variables, an extended Kalman filtering (EKF) algorithm is applied to estimate the state dependent parameters. The effectiveness of the model's formulation is supported by the quality of the corresponding predicted results, which in turn are validated via experimental tests.

Circumferential Combustor Cavity Flow Fields With Decreasing Core Flow

2020 ◽  
Author(s):  
Brian T. Bohan ◽  
Marc D. Polanka ◽  
Larry P. Goss
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Axial Length ◽  
Flow Behavior ◽  
Cavity Flow ◽  
Core Flow ◽  
Cold Flow ◽  
The Core ◽  
Core Flows

Abstract Prior research into Ultra Compact Combustors (UCC) showed an axial length savings compared to traditional gas-turbine combustors. This savings is achieved by swirling the reactants circumferentially in a recessed cavity around the outside diameter of the engine. A similar circumferential combustor is envisioned for a new engine configuration that positions the combustor outboard of a radial compressor and an inflow turbine. This configuration will offer an axial length savings for the entire engine, not just the combustor. The new engine configuration will not utilize a core flow path and thus requires all engine air from the compressor to pass through, or around, the combustor cavity. This report characterizes the cavity flow behavior as the core flow quantity was reduced from 80% of the total engine mass flow rate down to zero, representing the new engine configuration, while maintaining constant cavity mass flow rates. Velocity profiles were obtained with particle-shadow image velocimetry (PSV) in cold flow and with particle streak emission velocimetry (PSEV) in reacting flow experiments. The cold flow results showed that the core flow produced a suction and removed fluid from the circumferential cavity resulting in a lower cavity mass flow rate. This behavior resulted in lower circumferential velocities at higher core flow percentages and the fastest cavity velocity with zero core flow. Reacting flows produced a similar result with the fastest cavity velocities achieved at reduced, but non-zero core flows, and the slowest velocities at the highest and zero core flows. Overall, it was found that there was no negative impact on performance from the removal of the core flow that would prohibit development of the new engine.

Conceptual Design and Evaluation of Residual Heat Removal System for Small Lead-Bismuth Fast Reactor

2021 ◽  
Author(s):  
Shijia Xu ◽  
Qinglong Wen ◽  
Shenhui Ruan ◽  
Ningning Zhao ◽  
Yukang Liu
Keyword(s):  
Mass Flow Rate ◽  
Conceptual Design ◽  
Mass Flow ◽  
Flow Rate ◽  
Fast Reactor ◽  
Heat Removal ◽  
The Core ◽  
Heat Removal System ◽  
Removal System ◽  
Residual Heat

Abstract A high efficient and reliable residual heat removal system (RHRS), which is of great importance in the development of Lead-Bismuth Cooled Fast Reactor (LBFR), was conceptually designed in present study. Based on the design of the RHRS and LBFR, the RELAP5 4.0 code is used to model the system, and then the numerical calculation of steady and transient state was carried out to obtain the important thermal-hydraulic characteristic parameters. Meanwhile, the variations of the parameters were obtained during the transient process, such as the fuel cladding temperature and the natural circulation mass flow rate. The results show that the mass flow rate of the core finally stabilizes at 3.9 kg/s, which is about 1.35% of the rated flow. The peak cladding temperature is less than 750.3 K within 72 h during the whole process, which is far below the temperature safety limit. Therefore, it can be considered that the RHRS can successfully remove the core decay heat of LBFR. This research lays a solid technical foundation for the conceptual design of the RHRS.

Experimental and Numerical Heat Transfer on a Cylinder Cooled by Two Rectangular Jets of Different Heights

2012 ◽  
Author(s):  
Fabio Gori ◽  
Ivano Petracci ◽  
Matteo Angelino
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Maximum Heat ◽  
Optimal Position ◽  
Nusselt Numbers ◽  
Cylinder Diameter ◽  
Maximum Heat Transfer

The present paper presents experimental measurements of heat transfer on a cylinder, cooled by two rectangular jets of the same width but different height, H, in order to investigate the influence of the jet height on the local and the average cooling rates, because one of the problems in the heat transfer with jet flow is the convenience to choose the height of the jet in comparison to the height of the impinged object. The cylinder, heated by electric current, is set at several distances from the jet exit, x, on the symmetrical plane of symmetry, i.e. in a two-dimensional geometry, in order to find the optimal position which realizes the maximum heat transfer. The experimental heat transfer on the impingement shows that the local Nusselt number, defined with the cylinder diameter, D, is greater for the smaller slot because velocity is slightly higher but the average Nusselt numbers, defined with the cylinder diameter, D, are quite similar because the higher slot has a greater surface of impingement. Local and average Nusselt numbers are in qualitative agreement only if are compared with the same dimensionless distance, x/H, which can be interpreted as the ratio Rex/ReH, which is per unit of mass flow rate or is independent of the mass flow rate. Numerical simulations are carried out with a two-equations turbulent model using the RNG k-ε approach, on a cylinder with the same thickness of the experiments or without thickness. The numerical simulations of the cylinder without thickness are in acceptable agreement for what concern the average Nusselt numbers. The local Nusselt numbers are in fair agreement only if the cylinder has the thickness of the experiments, independently of the heat flow conditions, i.e. uniformly throughout the thickness or from the inner surface.

Quasi-Three Dimensional Verification of the Modular Axial Compressor Design Approach

2009 ◽  
Author(s):  
Magdy S. Attia ◽  
Christopher Hemerly
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Turbine Engine ◽  
The Core ◽  
Multi Stage ◽  
Core Module

In an article published some time ago [1], the authors investigated the idea of breaking down the [multi-stage] compressor component of the typical turbofan engine into modules. The motivation for this work stems from a “Lean Engineering” approach to gas turbine engine design. Five (5) modules were created; they are the inlet, front, core, rear, and exit modules. The intent is to maximize the size of the core module, as represented by the number of stages. Thus, many different compressors can share the core module, which will greatly reduce the Lifecycle costs for the fleet. The next stage of this work focuses on the Meanline and Throughflow design and analysis of two different compressors that share an 8-stage core. The first compressor, HPC-1, is a 10-stage compressor operating at 9,000 rpm, having 100 Kg/sec inlet mass flow rate, and a 13.5:1 overall pressure ratio. HPC-2 is a 13-stage modular upgrade of HPC-1, operating at 9,700 rpm, having an inlet mass flow rate of 140 Kg/sec, and a 27:1 overall pressure ratio. Applying the modular concept, the first and last stages (of HPC-1) have been removed and replaced by 2 and 3 stages, respectively. Additionally the inlet and exit modules have been redesigned as well. Preliminary Meanline analysis showed that this concept could present challenging boundary conditions for the design of the interface stage; the name assigned to the first stage of the core module. The conditions entering that stage represent a critical hurdle to the viability of this method. Slight variations in corrected speed and pressure ratios for stages 1 and 2 of the modular upgrade, HPC-2, provided the necessary realignment of the core module. The pressure ratio of the core module differs by less than 1% for both compressors. And in both instances, the corrected speed is virtually identical. Throughflow analysis, conducted using T-AXI [2], confirms the redesign and the viability of the method.

The standard unit mass flow rate of gas-liquid mixtures

2020 ◽  
pp. 13-16
Author(s):  
V.N. Petrov ◽  
◽  
V.F. Sopin ◽  
L.A. Akhmetzyanova ◽  
Ya.S. Petrova ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Liquid Mixtures ◽  
Unit Mass ◽  
Standard Unit

Prediction of Leakage Mass Flow Rate Through Gas Springs

1987 ◽  
Author(s):  
Roberto Bruno Bossio ◽  
Vincenzo Naso ◽  
Marian Cichy ◽  
Boleslaw Pleszewski
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate
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