scholarly journals A Simulation Study on Temperature Uniformity of Photovoltaic Thermal Using Computational Fluid Dynamics

2021 ◽  
Vol 82 (1) ◽  
pp. 21-38
Author(s):  
Mohd Afzanizam Mohd Rosli ◽  
Irfan Alias Farhan Latif ◽  
Muhammad Zaid Nawam ◽  
Mohd Noor Asril Saadun ◽  
Hasila Jarimi ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Temperature Distribution ◽  
Thermal Stresses ◽  
High Efficiency ◽  
Cfd Simulation ◽  
Operating Conditions ◽  
Working Fluid ◽  
Percentage Error ◽  
Pv Module

The temperature distribution across the photovoltaic (PV) module in most cases is not uniform, leading to regions of hotspots. The cells in these regions perform less efficiently, leading to an overall lower PV module efficiency. They can also be permanently damaged due to high thermal stresses. To enable the high-efficiency operation and a longer lifetime of the PV module, the temperatures must not fluctuate wildly across the PV module. In this study, a custom absorber is designed based on literature to provide a more even temperature distribution across the PV module. This design is two standard sets of spiral absorbers connected. This design is relatively less complicated for this reason and it allows room for adjusting the pipe spacing without much complication. The absorber design is tested via computational fluid dynamics (CFD) simulation using ANSYS Fluent 19.2, and the simulation model is validated by an experimental study with the highest percentage error of 9.44%. The custom and the serpentine absorber utilized in the experiment are simulated under the same operating conditions having water as the working fluid. The custom absorber design is found to have a more uniform temperature distribution on more areas of the PV module as compared to the absorber design utilized in the experiment, which leads to a lower average surface temperature of the PV module. This results in an increase in thermal and electrical efficiency of the PV module by 3.21% and 0.65%, respectively.

scholarly journals Thermal and Flow Simulation of Concentric Annular Heat Pipe with Symmetric or Asymmetric Condenser

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3333
Author(s):  
Eui-Hyeok Song ◽  
Kye-Bock Lee ◽  
Seok-Ho Rhi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Dissipation ◽  
Cfd Simulation ◽  
Research Work ◽  
Experimental Results ◽  
Working Fluid ◽  
Computational Fluid Dynamics Cfd

The current research work describes the flow and thermal analysis inside the circular flow region of an annular heat pipe with a working fluid, using computational fluid dynamics (CFD) simulation. A two-phase flow involving simultaneous evaporation and condensation phenomena in a concentric annular heat pipe (CAHP) is modeled. To simulate the interaction between these phases, the volume of fluid (VOF) technique is used. The temperature profile predicted using computational fluid dynamics (CFD) in the CAHP was compared with previously obtained experimental results. Two-dimensional and three-dimensional simulations were carried out, in order to verify the usefulness of 3D modeling. Our goal was to compute the flow characteristics, temperature distribution, and velocity field inside the CAHP. Depending on the shape of the annular heat pipe, the thermal performance can be improved through the optimal design of components, such as the inner width of the annular heat pipe, the location of the condensation part, and the amount of working fluid. To evaluate the thermal performance of a CAHP, a numerical simulation of a 50 mm long stainless steel CAHP (1.1 and 1.3 in diameter ratio and fixed inner tube diameter (78 mm)) was done, which was identical to the experimental system. In the simulated analysis results, similar results to the experiment were obtained, and it was confirmed that the heat dissipation was higher than that of the existing conventional heat pipe, where the heat transfer performance was improved when the asymmetric area was cooled. Moreover, the simulation results were validated using the experimental results. The 3-D simulation shows good agreement with the experimental results to a reasonable degree.

Design of double teeth metallic card clothing for the high-efficiency carding process by computational fluid dynamics

2021 ◽  
pp. 004051752110367
Author(s):  
Weihua Gu ◽  
Fuguo Li ◽  
Qinchao Gao ◽  
Chengzhi Zhuo ◽  
Zhong Lu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Textile Industry ◽  
High Efficiency ◽  
Cfd Simulation ◽  
Quality Level ◽  
Cylinder Surface ◽  
Operational Experience ◽  
Measuring Device ◽  
Double Teeth

The design of metallic card clothing, which is one of the most important devices in the textile industry, has always been based on operational experience. With the development of types of fibers and the requirements for the quality of yarns, those principles concluded by engineers seem to be losing their efficiency. Recent research found that airflow played an important role in the card process, which means airflow should be carefully studied. Computational fluid dynamics (CFD) simulation greatly helps in the analysis of airflow because the gauge between carding elements is too narrow to put in any measuring device. In the present study, with the help of CFD simulation, the air around different carding clothing with varied tooth depth was analyzed. It was concluded that the carding efficiency improvement in card clothing with lower tooth depth may be related to more concentrated air velocity at the tooth tips. This resulted in more probabilities that fibers would get through the cylinder surface at the teeth tips, so that the fibers could be caught by flat-top needles more efficiently. With this assumption, a new generation of card clothing called “double teeth” containing two teeth in a single section has been invented. The new configuration design of card clothing was then applied in several spinning mills on an industrial scale for experiments. The results showed about a 30% improvement in production at the same quality level as conventional card clothing, which implied the usefulness of the newly applied principles related to airflow. Despite the difficulty in the study of the complex carding process, the new airflow analysis method has shown an optional and worthwhile way of thinking that could make a difference in future research in the textile industry.

Computational Fluid Dynamics of a Radial Compressor Operating With Supercritical CO2

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
Rene Pecnik ◽  
Enrico Rinaldi ◽  
Piero Colonna
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Critical Point ◽  
Gas Turbine ◽  
Supercritical Co2 ◽  
Power Plants ◽  
Compressible Flows ◽  
High Efficiency ◽  
Working Fluid ◽  
Maximum Pressure

The merit of using supercritical CO2(scCO2) as the working fluid of a closed Brayton cycle gas turbine is now widely recognized, and the development of this technology is now actively pursued. scCO2 gas turbine power plants are an attractive option for solar, geothermal, and nuclear energy conversion. Among the challenges that must be overcome in order to successfully bring the technology to the market is that the efficiency of the compressor and turbine operating with the supercritical fluid should be increased as much as possible. High efficiency can be reached by means of sophisticated aerodynamic design, which, compared to other overall efficiency improvements, like cycle maximum pressure and temperature increase, or increase of recuperator effectiveness, does not require an increase in equipment cost, but only an additional effort in research and development. This paper reports a three-dimensional computational fluid dynamics (CFD) study of a high-speed centrifugal compressor operating with CO2 in the thermodynamic region slightly above the vapor–liquid critical point. The investigated geometry is the compressor impeller tested in the Sandia scCO2 compression loop facility. The fluid dynamic simulations are performed with a fully implicit parallel Reynolds-averaged Navier–Stokes code based on a finite volume formulation on arbitrary polyhedral mesh elements. In order to account for the strongly nonlinear variation of the thermophysical properties of supercritical CO2, the CFD code is coupled with an extensive library for the computation of properties of fluids and mixtures. A specialized look-up table approach and a meshing technique suited for turbomachinery geometries are also among the novelties introduced in the developed methodology. A detailed evaluation of the CFD results highlights the challenges of numerical studies aimed at the simulation of technically relevant compressible flows occurring close to the liquid–vapor critical point. The data of the obtained flow field are used for a comparison with experiments performed at the Sandia scCO2 compression-loop facility.

Effect of Operating Conditions on the Elasto-Hydrodynamic Performance of Foil Thrust Bearings for Supercritical CO2 Cycles

2016 ◽  
Author(s):  
Kan Qin ◽  
Ingo H. Jahn ◽  
Peter A. Jacobs
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Supercritical Co2 ◽  
Operating Conditions ◽  
Hydrodynamic Performance ◽  
Working Fluid ◽  
Inertia Force ◽  
Fluid Structure ◽  
Thrust Bearings ◽  
Foil Bearings

In order to efficiently utilize the abundant solar resources in Australia, the supercritical CO2 cycle is proposed as an alternative to conventional steam power cycles due to high thermal efficiency and compact system layout. To mature the technology readiness of the supercritical CO2 cycle, each part, including turbine, compressor, seals and bearings, needs to be evaluated and possibly re-designed under consideration of the high density working fluid. One key technology is the foil thrust bearing, which is an enabler for high speed operation and oil-free systems. Bearings are at the core of the turbomachinery system and have a significant influence on the performance of the whole system. In this paper, a quasi three-dimensional fluid-structure model, using computational fluid dynamics for the fluid phase is presented to study the elasto-hydrodynamic performance of foil thrust bearings. For the simulation of the gas flows within the thin gap, the computational fluid dynamics solver Eilmer is extended and a new solver is developed to simulate the bump and top foil within foil thrust bearings. These two solvers are linked using a coupling algorithm that maps pressure and deflection at the fluid structure interface. Results are presented for ambient CO2 conditions varying between 0.1 to 4.0MPa and 300 to 400K. It is found that the centrifugal inertia force can play a significant impact on the performance of foil thrust bearings with the highly dense CO2 and that the centrifugal inertia forces create unusual radial velocity profiles. In the ramp region of the foil thrust bearings, they generate an additional inflow close to the rotor inner edge, resulting in a higher peak pressure. Contrary in the flat region, the inertia force creates a rapid mass loss through the bearing outer edge, which reduces pressure in this region. This different flow field alters bearing performance compared to conventional air foil bearings. In addition, the effect of turbulence in load capacity and bearing torque is investigated. This study provides new insight into the flow physics within foil bearings operating with dense gases and for the selection of optimal operating condition to suit foil thrust bearings in supercritical CO2 cycles.

Computational fluid dynamics simulation of the supersonic steam ejector. Part 2. Optimal design of geometry and the effect of operating conditions on the ejector

2011 ◽  
Vol 226 (3) ◽  
pp. 715-723 ◽  
Author(s):  
L Cai ◽  
H T Zheng ◽  
Y J Li ◽  
Z M Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Optimal Design ◽  
Critical Pressure ◽  
Operating Conditions ◽  
Dynamics Simulation ◽  
Working Fluid ◽  
Entrainment Ratio ◽  
Steam Ejector ◽  
Mixing Chamber

The aim of this study is to investigate the use of computational fluid dynamics in predicting the performance and optimal design of the geometry of a steam ejector used in a steam turbine. In the current part, the real gas model was considered using IAPWS IF97 model, and the influences of working fluid pressure and backpressure were investigated. The results illustrate that working critical pressure and backflow critical pressure exist in the flow. Moreover, the entrainment ratio reaches its peak at the working critical pressure. The performance of the ejector was nearly the same when the outlet pressure was lower than the critical backpressure. Effects of ejector geometries were also investigated. The distance between the primary nozzle and the mixing chamber was at optimum, the length of the mixing chamber and the diameter of the throat had an optimal value according to the entrainment ratio. When the length of the diffuser or throat was decreased within a range, the entrainment ratio did not change significantly.

scholarly journals Computational Fluid Dynamics (CFD) Simulation on Mixing in T-Shaped Micromixer

2020 ◽  
Vol 932 ◽  
pp. 012006
Author(s):  
S N A Ahmad Termizi ◽  
C Y Khor ◽  
M A M Nawi ◽  
Nurlela Ahmad ◽  
Muhammad Ikman Ishak ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cfd Simulation ◽  
Computational Fluid Dynamics Cfd

A Study on the Performance of Stratified Air Conditioning Design in Assembly Halls – A Case Study at the Dazhi Cultural Center in Taiwan

2013 ◽  
Vol 368-370 ◽  
pp. 599-602 ◽  
Author(s):  
Ian Hung ◽  
Hsien Te Lin ◽  
Yu Chung Wang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Indoor Air ◽  
Air Conditioning ◽  
Cfd Simulation ◽  
Indoor Temperature ◽  
Cultural Center ◽  
Computational Fluid Dynamics Cfd

This study focuses on the performance of air conditioning design at the Dazhi Cultural Center and uses a computational fluid dynamics (CFD) simulation to discuss the differences in wind velocity and ambient indoor temperature between all-zone air conditioning design and stratified air conditioning design. The results have strong implications for air conditioning design and can improve the indoor air quality of assembly halls.

Computational Fluid Dynamics Thermohydrodynamic Analysis of Three-Dimensional Sector-Pad Thrust Bearings With Rectangular Dimples

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
C. I. Papadopoulos ◽  
L. Kaiktsis ◽  
M. Fillon
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Carrying Capacity ◽  
Thermal Effects ◽  
Operating Conditions ◽  
Load Carrying Capacity ◽  
Performance Indices ◽  
Thrust Bearings ◽  
Load Carrying ◽  
Texture Design

The paper presents a detailed computational study of flow patterns and performance indices in a dimpled parallel thrust bearing. The bearing consists of eight pads; the stator surface of each pad is partially textured with rectangular dimples, aiming at maximizing the load carrying capacity. The bearing tribological performance is characterized by means of computational fluid dynamics (CFD) simulations, based on the numerical solution of the Navier–Stokes and energy equations for incompressible flow. Realistic boundary conditions are implemented. The effects of operating conditions and texture design are studied for the case of isothermal flow. First, for a reference texture pattern, the effects of varying operating conditions, in particular minimum film thickness (thrust load), rotational speed and feeding oil pressure are investigated. Next, the effects of varying texture geometry characteristics, in particular texture zone circumferential/radial extent, dimple depth, and texture density on the bearing performance indices (load carrying capacity, friction torque, and friction coefficient) are studied, for a representative operating point. For the reference texture design, the effects of varying operating conditions are further investigated, by also taking into account thermal effects. In particular, adiabatic conditions and conjugate heat transfer at the bearing pad are considered. The results of the present study indicate that parallel thrust bearings textured by proper rectangular dimples are characterized by substantial load carrying capacity levels. Thermal effects may significantly reduce load capacity, especially in the range of high speeds and high loads. Based on the present results, favorable texture designs can be assessed.

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