scholarly journals Partial Redesign of an Accelerator Driven System Target for Optimizing the Heat Removal and Minimizing the Pressure Drops

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2090 ◽  
Author(s):  
Guglielmo Lomonaco ◽  
Giacomo Alessandroni ◽  
Walter Borreani
Keyword(s):  
Cooling System ◽  
Fluid Dynamic ◽  
Heat Removal ◽  
Dynamic Features ◽  
Pressure Drops ◽  
Driven System ◽  
Reference Design ◽  
Accelerator Driven Systems ◽  
Definition Of ◽  
Target Design

Accelerator Driven Systems (ADS) seem to be a good solution for safe nuclear waste transmutation. One of the most important challenges for this kind of machine is the target design, particularly for what concerning the target cooling system. In order to optimize this component a CFD-based approach has been chosen. After the definition of a reference design (Be target cooled by He), some parameters have been varied in order to optimize the thermal-fluid-dynamic features. The final optimized target design has an increased security margin for what regarding Be melting and reduces the maximum coolant velocity (and consequently even more the pressure drops).

Experimental Investigation on Effusion Liner Geometries for Aero-Engine Combustors: Evaluation of Global Acoustic Parameters

2012 ◽  
Author(s):  
A. Andreini ◽  
B. Facchini ◽  
L. Ferrari ◽  
G. Lenzi ◽  
F. Simonetti ◽  
...  
Keyword(s):  
Cooling System ◽  
Fluid Dynamic ◽  
Pressure Fluctuations ◽  
Main Concern ◽  
Dynamic Features ◽  
Ambient Conditions ◽  
Test Rig ◽  
Acoustic Parameters ◽  
Field Range ◽  
Aero Engines

In new generation aero-engines based on the innovative lean combustion technology, thermoacoustic instabilities are one of the most important issues and their prevention and reduction are challenging goals. To achieve these targets, the use of multi-perforated liners, that have to primarily provide an efficient liner cooling, is very attractive because they are efficient passive dampers of pressure fluctuations, especially with bias flow. The design of multi-perforated liners for both thermal and acoustic purposes can be accomplished by selecting liner parameters, such as hole diameter, pattern and inclination, main and bias Mach numbers, fulfilling both requirements; this procedure requires to assess the effect of both geometrical and fluid-dynamic features. Thus, a specific research project is ongoing on the acoustic and thermal experimental characterization of selected multi-perforated liner geometries. In this paper, the complete experimental campaign on the acoustic behavior of the aforementioned liners has been carried out in the planar wave field range, that is of main concern in aero-engines. For this purpose, an innovative modular test rig has been designed to characterize test cases at ambient conditions, changing bias and main flows up to operating engine conditions. Liner geometries account for 3 different hole diameters, 5 different patterns and 2 hole inclinations, ranging within typical cooling system values; tests were performed with the two-source multi-microphone technique to evaluate global acoustic parameters independently from test rig boundary conditions. The acoustic performances of liners are discussed in terms of the energy dissipation coefficient.

Manifold Design for Micro-Channel Cooling With Uniform Flow Distribution

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Stephen A. Solovitz ◽  
Jeffrey Mainka
Keyword(s):  
Power Law ◽  
Cooling System ◽  
Heat Removal ◽  
Flow Distribution ◽  
Reynolds Numbers ◽  
Electronic Systems ◽  
Pressure Drops ◽  
Developing Flow ◽  
Micro Channels ◽  
Uniform Flow Distribution

High-power electronic systems often require temperature uniformity for optimal performance. While many advanced cooling systems, such as micro-channels, result in significant heat removal, they are also susceptible to flow mal-distribution that can impact the local temperature variation on a device. By examining the pressure drops through each flow path in a multi-channel cooling system, an analytical model is predicted for the optimal manifold shape to produce uniform velocities. This is a simple power law, whose exponent depends on the flow regime in the manifold passages. The model is validated for laminar fully developed conditions using a series of computational simulations. With the power law design, the speeds in a parallel channel design are uniformly distributed at low Reynolds numbers, with a standard deviation of less than 3% of the overall mean channel speed. At higher Reynolds numbers, some mal-distribution is observed due to developing flow conditions, but it is not as significant as with typical untapered designs.

Experimental and Theoretical Investigation of Thermal Effectiveness in Multiperforated Plates for Combustor Liner Effusion Cooling

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Antonio Andreini ◽  
Bruno Facchini ◽  
Alessio Picchi ◽  
Lorenzo Tarchi ◽  
Fabio Turrini
Keyword(s):  
Film Cooling ◽  
Cooling System ◽  
Fluid Dynamic ◽  
Density Ratio ◽  
Heat Removal ◽  
Correlative Analysis ◽  
Pattern Shape ◽  
The Impact ◽  
Combustor Liner ◽  
Overall Effectiveness

State-of-the-art liner cooling technology for modern combustors is represented by effusion cooling (or full-coverage film cooling). Effusion is a very efficient cooling strategy based on the use of multiperforated liners, where the metal temperature is lowered by the combined protective effect of the coolant film and heat removal through forced convection inside each hole. The aim of this experimental campaign is the evaluation of the thermal performance of multiperforated liners with geometrical and fluid-dynamic parameters ranging among typical combustor engine values. Results were obtained as the adiabatic film effectiveness following the mass transfer analogy by the use of pressure sensitive paint, while the local values of the overall effectiveness were obtained by eight thermocouples housed in as many dead holes about 2 mm below the investigated surface. Concerning the tested geometries, different porosity levels were considered: such values were obtained by both increasing the hole diameter and pattern spacing. Then the effect of the hole inclination and aspect ratio pattern shape were tested to assess the impact of typical cooling system features. Seven multiperforated planar plates, reproducing the effusion arrays of real combustor liners, were tested, imposing six blowing ratios in the range 0.5–5. Additional experiments were performed in order to explore the effect of the density ratio (DR=1;1.5) on the film effectiveness. Test samples were made of stainless steel (AISI304) in order to achieve the Biot number similitude for the overall effectiveness tests. To extend the validity of the survey a correlative analysis was performed to point out, in an indirect way, the augmentation of the hot side heat transfer coefficient due to effusion jets. Finallyv,in order to address the thermal behavior of the different geometries in the presence of gas side radiation, additional simulations were performed considering different levels of radiative heat flux.

Gas Driven Circulation in an Adiabatic Air-Water Loop With Reference to Accelerator Driven Systems

2002 ◽  
Author(s):  
Mario De Salve ◽  
Mario Malandrone ◽  
Bruno Panella
Keyword(s):  
Void Fraction ◽  
Flow Rate ◽  
Liquid Velocity ◽  
Fluid Dynamic ◽  
Test Rig ◽  
Horizontal Pipe ◽  
Pressure Drops ◽  
Driven Systems ◽  
Experimental Apparatus ◽  
Accelerator Driven Systems

In order to investigate the fluid dynamic mechanisms of the gas driven circulation, with reference to the accelerator driven systems (ADS), an experimental research with water driven by air injected at the inlet of the vertical riser in an adiabatic test rig has been carried out. The present experimental apparatus consists essentially of two vertical plexiglass pipes 3.8 m long, 0.08 m I.D., that are connected at the bottom by a horizontal pipe and at the top by a large open tank. The test rig is equipped with differential pressure transducers and two quick closing valves to measure the pressure drops and the average void fraction. The air flow rate ranges up to 5000 Nl/h, at 7 bar pressure, and the liquid flow rate can reach the value of more than 5 kg/s. The research aim is to investigate the effect of the superficial gas velocity on the superficial liquid velocity, on the void fraction and on the pressure drops, for a given geometry. The test data have been compared with some two-phase pressure drops and void fraction correlations. The geometry effect has been investigated too.

Experimental and Theoretical Investigation of Thermal Effectiveness in Multi-Perforated Plates for Combustor Liner Effusion Cooling

2013 ◽  
Author(s):  
Antonio Andreini ◽  
Bruno Facchini ◽  
Alessio Picchi ◽  
Lorenzo Tarchi ◽  
Fabio Turrini
Keyword(s):  
Film Cooling ◽  
Cooling System ◽  
Fluid Dynamic ◽  
Heat Removal ◽  
Perforated Plates ◽  
Correlative Analysis ◽  
Pattern Shape ◽  
The Impact ◽  
Combustor Liner ◽  
Overall Effectiveness

State-of-the-art liner cooling technology for modern combustors is represented by effusion cooling (or full-coverage film cooling). Effusion is a very efficient cooling strategy based on the use of multi-perforated liners, where metal temperature is lowered by the combined protective effect of coolant film and heat removal through forced convection inside each hole. The aim of this experimental campaign is the evaluation of the thermal performance of multi-perforated liners with geometrical and fluid-dynamic parameters ranging among typical combustor engine values. Results were obtained as adiabatic film effectiveness following the mass transfer analogy by the use of Pressure Sensitive Paint, while local values of overall effectiveness were obtained by eight thermocouples housed in as many dead holes about 2 mm below the investigated surface. Concerning the tested geometries, different porosity levels were considered: such values were obtained both increasing the hole diameter and pattern spacing. Then the effect of hole inclination and aspect ratio pattern shape were tested to assess the impact of typical cooling system features. Seven multi perforated planar plates, reproducing the effusion arrays of real combustor liners, were tested imposing 6 blowing ratios in the range 0.5–5. Test samples were made of stainless steel (AISI304) in order to achieve Biot number similitude for overall effectiveness tests. To extend the validity of the survey a correlative analysis was performed to point out, in an indirect way, the augmentation of hot side heat transfer coefficient due to effusion jets. Finally, to address the thermal behaviour of the different geometries in presence of gas side radiation, additional simulations were performed considering different levels of radiative heat flux.

scholarly journals A 3D Coupled Approach for the Thermal Design of Aero-Engine Combustor Liners

2016 ◽  
Author(s):  
L. Mazzei ◽  
A. Andreini ◽  
B. Facchini ◽  
L. Bellocci
Keyword(s):  
Design Process ◽  
Cfd Simulation ◽  
Swirling Flow ◽  
Cooling System ◽  
Fluid Dynamic ◽  
Heat Removal ◽  
Thermal Design ◽  
Flow Network ◽  
Aero Engine ◽  
Annular Combustor

The adoption of lean burn combustion to limit NOx emissions of modern aero-engines imposes a drastic reduction of air dedicated to cooling combustor dome and liners. In the latest years many aero-engine manufacturers are hence implementing effusion cooling, which provides uniform protection on the hot side of the liner and significant heat removal within the perforation. With an industrial perspective, the development of such components is usually carried out with different strategies depending on the level of accuracy required in the design phase involved (i.e preliminary or detailed). In the collaboration between GE Avio and University of Florence, the preliminary design of these devices is carried out with Therm1D, an in-house thermal flow-network solver based on the 1D correlative approach proposed by Lefebvre. This strategy, however, is not capable of taking into account the complexity of the three-dimensional nature of the flow field and the interaction between swirling flow and liner cooling, making necessary the use of Computational Fluid Dynamics (CFD) in the most advanced phases of the design process. Nevertheless, notwithstanding the increasing popularity of CFD, even a RANS simulation of a single sector of an annular combustor still presents a challenge, when the cooling system is taken into account. This issue becomes more critical in case of modern effusion cooled combustors, which may contain thousands of holes for each sector. With the aim of of increasing the fidelity of the prediction, keeping in mind the industrial needs for limited computational efforts, a new tool has been developed: Therm3D. This approach involves the CFD simulation of the combustor flametube by modelling effusion cooling with point mass sources, whereas the fluid dynamic prediction of the remaining part is fulfilled exploiting the equivalent flow-network solver implemented in Therm1D, which provides the estimation of flow split and cold side heat loads. The solution is coupled with two separate calculations aimed at solving flame radiation and heat conduction within the metal. This paper describes the main findings of the application of Therm3D to a lean annular combustor. The results obtained have been compared to experimental data and the above mentioned numerical tools employed during the design process.

scholarly journals Experimental Investigation and Comparison of the Thermal Performance of Additively and Conventionally Manufactured Heat Exchangers

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 574
Author(s):  
Ana Vafadar ◽  
Ferdinando Guzzomi ◽  
Kevin Hayward
Keyword(s):  
Surface Roughness ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
High Efficiency ◽  
Cooling System ◽  
Fluid Dynamic ◽  
Dynamic Performance ◽  
Experimental Studies ◽  
Manufacturing Method ◽  
Industrial Sectors

Air heat exchangers (HXs) are applicable in many industrial sectors because they offer a simple, reliable, and cost-effective cooling system. Additive manufacturing (AM) systems have significant potential in the construction of high-efficiency, lightweight HXs; however, HXs still mainly rely on conventional manufacturing (CM) systems such as milling, and brazing. This is due to the fact that little is known regarding the effects of AM on the performance of AM fabricated HXs. In this research, three air HXs comprising of a single fin fabricated from stainless steel 316 L using AM and CM methods—i.e., the HXs were fabricated by both direct metal printing and milling. To evaluate the fabricated HXs, microstructure images of the HXs were investigated, and the surface roughness of the samples was measured. Furthermore, an experimental test rig was designed and manufactured to conduct the experimental studies, and the thermal performance was investigated using four characteristics: heat transfer coefficient, Nusselt number, thermal fluid dynamic performance, and friction factor. The results showed that the manufacturing method has a considerable effect on the HX thermal performance. Furthermore, the surface roughness and distribution, and quantity of internal voids, which might be created during and after the printing process, affect the performance of HXs.

scholarly journals Performance Analysis of Hybrid Desiccant Cooling System with Enhanced Dehumidification Capability Using TRNSYS

2021 ◽  
Vol 11 (7) ◽  
pp. 3236
Author(s):  
Ji Hyeok Kim ◽  
Joon Ahn
Keyword(s):  
Thermal Comfort ◽  
Cooling System ◽  
Operation Mode ◽  
Heat Removal ◽  
Simulation Models ◽  
Coefficient Of Performance ◽  
Dimensional Structure ◽  
Dominant Factor ◽  
Exhaust Heat ◽  
Chp System

In a field test of a hybrid desiccant cooling system (HDCS) linked to a gas engine cogeneration system (the latter system is hereafter referred to as the combined heat and power (CHP) system), in the cooling operation mode, the exhaust heat remained and the latent heat removal was insufficient. In this study, the performance of an HDCS was simulated at a humidity ratio of 10 g/kg in conditioned spaces and for an increasing dehumidification capacity of the desiccant rotor. Simulation models of the HDCS linked to the CHP system were based on a transient system simulation tool (TRNSYS). Furthermore, TRNBuild (the TRNSYS Building Model) was used to simulate the three-dimensional structure of cooling spaces and solar lighting conditions. According to the simulation results, when the desiccant capacity increased, the thermal comfort conditions in all three conditioned spaces were sufficiently good. The higher the ambient temperature, the higher the evaporative cooling performance was. The variation in the regeneration heat with the outdoor conditions was the most dominant factor that determined the coefficient of performance (COP). Therefore, the COP was higher under high temperature and dry conditions, resulting in less regeneration heat being required. According to the prediction results, when the dehumidification capacity is sufficiently increased for using more exhaust heat, the overall efficiency of the CHP can be increased while ensuring suitable thermal comfort conditions in the cooling space.

Experimental and Numerical Validation of Conical Strainer Fluid/Structural Performance Model

2012 ◽  
Author(s):  
M. Carlomagno ◽  
S. Rossin ◽  
M. Delvecchio ◽  
A. Anichini
Keyword(s):  
Pressure Drop ◽  
Fluid Dynamic ◽  
Performance Model ◽  
Structural Performance ◽  
Mechanical Resistance ◽  
Gas Industry ◽  
Process Gas ◽  
Compressor Inlet ◽  
Geometric Variables ◽  
Definition Of

Temporary conical strainers are widely employed in the Oil & Gas industry as filtering devices in the Centrifugal Compressors suction line. They protect compressor stages from the ingestion of foreign objects whether coming from dirty process gas or left in the pipeline after its construction. Very few literature and research papers are available on the fluid dynamic and structural performance of conical strainers. The purpose of this work is to plug this gap by the definition of a theoretical-experimental model for the characterization of the pressure drop and mechanical resistance of these devices. Starting from the definition of the main fluid dynamics and geometric variables which influence the performances, an experimental campaign has been performed in order to derive the relationship governing the pressure drop behavior. The model efficacy has been confirmed by a CFD analysis, which also allowed a qualitative insight review into the dynamics of velocity and turbulence intensity fields. Further tests have been performed in order to validate the model at off-design points. As far as the structural analysis is concerned, several FEM models and DOE techniques have been implemented in order to define relationships for bust pressure computation and feasible design improvements with respect to the current state of the art. Besides fluid dynamic and structural correlations, the notable achievements of this work are the definition of best pressure static probes positioning and the maximum clogging level that a strainer can withstand before collapse. Furthermore, some guidelines are given in order to prevent pipeline resonance and acoustic fatigue caused by the interaction between strainer turbulence and compressor inlet flow.

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