scholarly journals Numerical Investigation of Parameters Affecting the Thermal and Hydrodynamic Characteristics of Impinging Jets in Cross Flow

1970 ◽  
Vol 1 (1) ◽  
Author(s):  
B. M. Suloiman ◽  
B. A. Jubran
Keyword(s):  
Numerical Investigation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Impinging Jets ◽  
Minor Effect ◽  
Vortex Strength ◽  
Effective Velocity

In this investigation the hydrodynamic and the thermal fields due to a single impinging jet in cross-flow have been investigated numerically, using a 2-D axisymmetric model in order to predict the ground vortex characteristics. The parameters investigated include the effective velocity ratio, the nozzle height, the nozzle pressure ratio, the intake location, the intake mass flow rate and the jet temperature ratio. It is interesting to note that even with the 2-D modeling limitations it was possible to capture most of the thermal and fluid field characteristics of the ground vortex. It was found that the temperature distribution in the flow field is greatly affected by the effective velocity, and the maximum penetration point of the ground vortex is equal to the hot gas penetration. The ground vortex strength increases slightly with increasing the intake mass flow rate but has a minor effect on the ground vortex geometry and on the penetration of the hot gases. The intake location has a significant effect on the ground vortex strength when it is located upstream of the ground vortex core. Key Words: Numerical investigation, Turbulence Models, Impinging jets, Cross-flow.

Theoretical study of the effect of liquid desiccant mass flow rate on the performance of a cross flow parallel-plate liquid desiccant-air dehumidifier

2013 ◽  
Vol 49 (11) ◽  
pp. 1587-1593 ◽  
Author(s):  
Abdulrahman Th. Mohammad ◽  
Sohif Bin Mat ◽  
M. Y. Sulaiman ◽  
K. Sopian ◽  
Abduljalil A. Al-abidi
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Parallel Plate ◽  
Theoretical Study ◽  
Cross Flow ◽  
Liquid Desiccant

A New Concept of Impingement Cooling for Gas Turbine Hot Parts and Its Influence on Plant Performance

2003 ◽  
Author(s):  
B. Facchini ◽  
M. Surace ◽  
S. Zecchi
Keyword(s):  
Gas Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Power Plants ◽  
Cooling System ◽  
Impinging Jets ◽  
Plant Performance ◽  
Transfer Coefficients ◽  
Impingement Cooling

Significant improvements in gas turbine cooling technology are becoming harder as progress goes over and over. Several impingement cooling solutions have been extensively studied in past literature. An accurate and extensive numerical 1D simulation on a new concept of sequential impingement was performed, showing good results. Instead of having a single impingement plate, we used several perforated plates, connecting the inlet of each one with the outlet of the previous one. Main advantages are: absence of the negative interaction between transverse flow and last rows impinging jets (reduced deflection); better distribution of pressure losses and heat transfer coefficients among the different plates, especially when pressure drops are significant and available coolant mass flow rate is low (lean premixed combustion chamber and LP turbine stages). Practical applications can have a positive influence on both cooled nozzles and combustion chambers, in terms of increased cooling efficiency and coolant mass flow rate reduction. Calculated effects are used to analyze main influences of such a cooling system on global performances of power plants.

Transient Response of a Cross Flow Heat Exchanger Subjected to Temperature and Flow Perturbations

2015 ◽  
Author(s):  
Karthik Silaipillayarputhur ◽  
Stephen A. Idem
Keyword(s):  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Transient Performance ◽  
Numerical Predictions ◽  
Minimum Capacity ◽  
Flow Heat

The transient performance of a multi-pass cross flow heat exchanger subjected to temperature and mass flow rate perturbations, where the heat exchanger flow circuiting is neither parallel flow nor counter flow, is considered in this work. A detailed numerical study was performed for representative single-pass, two-pass, and three-pass heat exchangers. Numerical predictions were obtained for cases where the minimum capacity rate fluid was subjected to a step change in inlet temperature in absence of mass flow rate perturbations. Likewise, numerical predictions were obtained for the heat exchangers operating initially at steady state, where a step mass flow rate change of the minimum capacity rate fluid was imposed in the absence of any fluid temperature perturbations. The transient performance of this particular heat exchanger configuration subjected to these temperature and flow disturbances has not been discussed previously in the available literature. In the present study the energy balance equations for the hot and cold fluids and the heat exchanger wall were solved using an implicit central finite difference method. A parametric study was conducted by varying the dimensionless quantities that govern the transient response of the heat exchanger over a typical range of values. Because of the storage of energy in the heat exchanger wall, and finite propagation times associated with the inlet perturbations, the outlet temperatures of both fluids do not respond instantaneously. The results are compared with previously published transient performance predictions of multi-pass counter flow and parallel flow heat exchangers.

scholarly journals Multiple Impinging Jet Air-Assisted Atomization

2017 ◽  
Author(s):  
Mário Costa ◽  
Bruno Pizziol ◽  
Miguel Panao ◽  
André Silva
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Alternative Fuels ◽  
Fossil Fuels ◽  
Cross Flow ◽  
Liquid Sheet ◽  
Air Mass ◽  
Breakup Mechanism ◽  
The Impact

The growth of the aviation sector triggered the search for alternative fuels and continued improvements in thecombustion process. This work addresses the technological challenges associated with spray systems and theconcern of mixing biofuels with fossil fuels to produce alternative and more ecological fuels for aviation. This workproposes a new injector design based on sprays produced from the simultaneous impact of multiple jets, using anadditional jet of air to assist the atomization process. The results evidence the ability to control the average dropsize through the air-mass flow rate. Depending on the air-mass flow rate there is a transition between atomizationby hydrodynamic breakup of the liquid sheet formed on the impact point, to an aerodynamic breakup mechanism,as found in the atomization of inclined jets under cross-flow conditions. The aerodynamic shear breakupdeteriorates the atomization performance, but within the same order of magnitude. Finally, our experiments showthat mixing a biofuel with a fossil fuel does not significantly alter the spray characteristics, regarded as a stepfurther in developing alternative and more ecological fuels for aero-engines.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4737

Review and Analysis of Cross Flow Heat Exchanger Transient Modeling for Flow Rate and Temperature Variations

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Tianyi Gao ◽  
James Geer ◽  
Bahgat Sammakia
Keyword(s):  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Transient Response ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Inlet Temperature ◽  
Flow Rate Change ◽  
Flow Heat

Heat exchangers are important facilities that are widely used in heating, ventilating, and air conditioning (HVAC) systems. For example, heat exchangers are the primary units used in the design of the heat transfer loops of cooling systems for data centers. The performance of a heat exchanger strongly influences the thermal performance of the entire cooling system. The prediction of transient phenomenon of heat exchangers is of increasing interest in many application areas. In this work, a dynamic thermal model for a cross flow heat exchanger is solved numerically in order to predict the transient response under step changes in the fluid mass flow rate and the fluid inlet temperature. Transient responses of both the primary and secondary fluid outlet temperatures are characterized under different scenarios, including fluid mass flow rate change and a combination of changes in the fluid inlet temperature and the mass flow rate. In the ε-NTU (number of transfer units) method, the minimum capacity, denoted by Cmin, is the smaller of Ch and Cc. Due to a mass flow rate change, Cmin may vary from one fluid to another fluid. The numerical procedure and transient response regarding the case of varying Cmin are investigated in detail in this study. A review and comparison of several journal articles related to the similar topic are performed. Several sets of data available in the literatures which are in error are studied and analyzed in detail.

scholarly journals The Eulerian–Lagrangian Approach for the Numerical Investigation of an Acoustic Field Generated by a High-Speed Gas-Droplet Flow

Fluids ◽  
2021 ◽  
Vol 6 (8) ◽  
pp. 274
Author(s):  
Valeriia G. Melnikova ◽  
Andrey S. Epikhin ◽  
Matvey V. Kraposhin
Keyword(s):  
Numerical Investigation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
High Speed ◽  
Acoustic Noise ◽  
Hybrid Approach ◽  
Lagrangian Approach ◽  
Acoustic Properties ◽  
Lagrangian Model

This paper presents the Eulerian–Lagrangian approach for numerical modeling of high-speed gas-droplet flows and aeroacoustics. The proposed hybrid approach is implemented using the OpenFOAM library and two different methods. The first method is based on a hybrid convective terms approximation method employing a Kurganov–Tadmor and PIMPLE scheme. The second method employs the regularized or quasi-gas dynamic equations. The Lagrangian part of the flow description uses the OpenFOAM cloud model. Within this model, the injected droplets are simulated as packages (parcels) of particles with constant mass and diameter within each parcel. According to this model, parcels moving in the gas flow could undergo deceleration, heating, evaporation, and breakup due to hydrodynamic instabilities. The far-field acoustic noise is predicted using Ffowcs Williams and Hawking’s analogy. The Lagrangian model is verified using the cases with droplet evaporation and motion. Numerical investigation of water microjet injection into the hot ideally expanded jet allowed studying acoustic properties and flow structures, which emerged due to the interaction of gas and liquid. Simulation results showed that water injection with a mass flow rate equal to 13% of the gas jet mass flow rate reduced the noise by approximately 2 dB. This result was in good coincidence with the experimental observations, where maximum noise reduction was about 1.6 dB.

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 Numerical investigation on the cooling performance of a novel jet cooler design for a supercritical CO2 turbine rotor shaft cooling

2021 ◽  
Vol 22 ◽  
pp. 51
Author(s):  
Jun Li ◽  
Hal Gurgenci ◽  
Jishun Li ◽  
Zhiqiang Guan ◽  
Lun Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Negative Impact ◽  
Dominant Factor ◽  
Transfer Performance ◽  
Fluid Density

Numerical investigation was carried out to study the heat transfer performance for a high-speed rotating cylindrical surface subjected to single row array round jets impingement, under a very small gap spacing. Various parameters that affect heat transfer, such as the fluid density, flow velocity and Nusselt number distributions of the radius clearance were studied based on varied nozzle to target surface spacing H and mass flow rate. It has been found that the fluid density was a dominant factor and the velocity was the secondary factor for the gas jet heat transfer performances. The overall heat transfer was improved with a reduction in the number of nozzles, for given inlet mass flow rate boundary conditions. The decrease of H/di (di, nozzle diameter) may have positive or negative effects on the heat transfer performance from the impingement surface. Reducing the radius gap H, for a certainty, increases the average density of the fluid in the clearance, which is desirable in applications that enhance heat transfer performance. But when the radius gap (H) is small enough, increasing di may have a negative impact on heat transfer.

Numerical Investigation on the Flow Characteristics in a Cover-Plate Pre-Swirl System

2021 ◽  
Author(s):  
Menghua Jian ◽  
Xuesen Yang ◽  
Wei Dong
Keyword(s):  
Reynolds Number ◽  
Numerical Investigation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Circumferential Velocity ◽  
Cover Plate ◽  
Temperature Reduction

Abstract This paper presents a numerical investigation on the flow characteristics in a cover-plate pre-swirl system. The Reynolds-averaged Navier-Stokes equations, coupled with the standard k-ε turbulent model, are adopted and solved. With the inlet total pressure and total temperature being constant, the influences of the temperature reduction and flow resistance by changing pressure ratios and rotational Reynolds numbers were conducted. Flow features in the pre-swirl nozzle, pre-swirl cavity, receiver hole and cover-plate cavity were summarized. The results obtained in this study indicate that the pressure ratio and rotational Reynolds number have a significant influence on the vortex structure of the pre-swirl system. As the air is accelerated by the pre-swirl nozzle, the difference of circumferential velocity between the air and the rotational domain would be reduced, and the static temperature of the air would be decreased. The pressure drop in the pre-swirl system mainly occurs in the pre-swirl nozzle and the pre-swirl cavity. In addition, with the increase of the pressure ratio, the air mass flow rate and the circumferential velocity of the air out of the nozzle increased, thereby leading to an increment in temperature reduction. Moreover, with the increasing of the rotational Reynolds number, the dimensionless mass flow rate and temperature reduction of the pre-swirl system, which are mainly determined by the flow incidence angle of cooling air at the receiver hole, will first increase to a maximum and then decrease.

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