scholarly journals The Effect of Tree-Planting Patterns on the Microclimate within a Courtyard

2019 ◽  
Vol 11 (6) ◽  
pp. 1665 ◽  
Author(s):  
Junying Li ◽  
Jiying Liu ◽  
Jelena Srebric ◽  
Yuanman Hu ◽  
Miao Liu ◽  
...  
Keyword(s):  
Air Temperature ◽  
Local Heat Transfer ◽  
Field Measurements ◽  
Weather Conditions ◽  
Local Heat ◽  
Tree Planting ◽  
Cfd Model ◽  
Planting Pattern ◽  
Wind Velocities ◽  
Computational Fluid Dynamics Cfd

Current landscape design within a courtyard usually does not take into account the influence of the tree-planting pattern, which has an important influence on the outdoor microclimate and occupants’ thermal comfort. At present, the extent of the influence on the microclimate has not yet been made clear. Computational Fluid Dynamics (CFD) was employed to run this model under hot summer weather conditions. Field measurements validated the performance of the CFD model. This study conducted numerical simulations for five different tree-planting patterns, including (i) focused tree-planting (F), (ii) cornered tree-planting (C), (iii) multi-row tree-planting (R), (iv) surround tree-planting (S) and (v) no tree-planting (N). Our study found that the tree-planting pattern affects both the distribution of air temperature and the degree of local heat transfer. Specifically, the C, S and N patterns allow for higher ventilation in the studied courtyard, while the F and R patterns cause lower wind velocities and associated courtyard ventilation. The average air temperature for the C pattern is lower during summer afternoons than the other patterns. The wind flow pattern in the studied courtyard does not vary significantly with different tree-planting patterns. Nevertheless, the general relative humidity in the courtyard does not vary significantly with different tree-planting patterns, except for the N pattern. A future analysis is needed to investigate the mechanisms of the phenomenon.

scholarly journals Experimental verification of a CFD model for the closed plant factory under artificial lighting

2020 ◽  
Vol 213 ◽  
pp. 03013
Author(s):  
Wei Lu ◽  
Yiwen Hu ◽  
Shenghan Zhou ◽  
Xin Zhang ◽  
Quan Yuan ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Air Temperature ◽  
Experimental Verification ◽  
Cfd Model ◽  
Air Velocity ◽  
Artificial Lighting ◽  
Mean Relative Error ◽  
Plant Factory ◽  
Computational Fluid Dynamics Cfd ◽  
The Mean

A computational fluid dynamics (CFD) model for the closed plant factory under artificial lighting has been developed in this study, the experimental verification of CFD model with the air velocity value was compared with the measured air temperature value. The results showed that the mean relative error of validation with the air velocity was 15%, and comparable with experimentally observed air temperature profile inside the plant factory with RMSE of 3% which show the utility of CFD to study plant factory microclimatic parameters.

Heat Transfer, Pressure Loss and Flow Field Measurements Downstream of Staggered Two-Row Circular and Elliptical Pin Fin Arrays

2005 ◽  
Vol 127 (5) ◽  
pp. 458-471 ◽  
Author(s):  
Oguz Uzol ◽  
Cengiz Camci
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Pressure Loss ◽  
Total Pressure ◽  
Local Heat Transfer ◽  
Field Measurements ◽  
Local Heat ◽  
Wake Flow ◽  
Pin Fin ◽  
Pin Fin Arrays

This paper presents the results of heat transfer, total pressure loss, and wake flow field measurements downstream of two-row staggered elliptical and circular pin fin arrays. Two different types of elliptical fins are tested, i.e., a Standard Elliptical Fin (SEF) and a fin that is based on NACA four digit symmetrical airfoil shapes (N fin). The results are compared to those of a corresponding circular pin fin array. The minor axis lengths for both types of elliptical fins are kept equal to the diameter of the circular fins. Experiments are performed using Liquid Crystal Thermography and total pressure probe wake surveys in a Reynolds number range of 18 000 and 86 000 as well as Particle Image Velocimetry (PIV) measurements at ReD=18 000. The pin fins had a height-to-diameter ratio of 1.5. The streamwise and the transverse spacings were equal to one circular fin diameter, i.e., S/D=X/D=2. For the circular fin array, average Nusselt numbers on the endwall within the wake are about 27% higher than those of SEF and N fin arrays. Different local heat transfer enhancement patterns are observed for elliptical and circular fins. In terms of total pressure loss, there is a substantial reduction in case of SEF and N fins. The loss levels for the circular fin are 46.5% and 59.5% higher on average than those of the SEF and N fins, respectively. An examination of the Reynolds analogy performance parameter show that the performance indices of the SEF and the N fins are 1.49 and 2.0 times higher on average than that of circular fins, respectively. The thermal performance indices show a collapse of the data, and the differences are much less evident. Nevertheless, N fins still show slightly higher thermal performance values. The wake flow field measurements show that the circular fin array creates a relatively large low momentum wake zone compared to the SEF and N fin arrays. The wake trajectories of the first row of fins in circular, SEF and N fin arrays are also different from each other. The turbulent kinetic energy levels within the wake of the circular fin array are higher than those for the SEF and the N fin arrays. The transverse variations in turbulence levels correlate well with the corresponding local heat transfer enhancement variations.

Hydrodynamic evaluation of a full-scale facultative pond by computational fluid dynamics (CFD) and field measurements

2014 ◽  
Vol 70 (3) ◽  
pp. 569-575 ◽  
Author(s):  
Ricardo Gomes Passos ◽  
Marcos von Sperling ◽  
Thiago Bressani Ribeiro
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Short Circuit ◽  
Field Measurements ◽  
Tracer Test ◽  
Full Scale ◽  
Cfd Model ◽  
Cfd Modelling ◽  
Hydraulic Behaviour ◽  
Computational Fluid Dynamics Cfd

Knowledge of the hydraulic behaviour is very important in the characterization of a stabilization pond, since pond hydrodynamics plays a fundamental role in treatment efficiency. An advanced hydrodynamics characterization may be achieved by carrying out measurements with tracers, dyes and drogues or using mathematical simulation employing computational fluid dynamics (CFD). The current study involved experimental determinations and mathematical simulations of a full-scale facultative pond in Brazil. A 3D CFD model showed major flow lines, degree of dispersion, dead zones and short circuit regions in the pond. Drogue tracking, wind measurements and dye dispersion were also used in order to obtain information about the actual flow in the pond and as a means of assessing the performance of the CFD model. The drogue, designed and built as part of this research, and which included a geographical positioning system (GPS), presented very satisfactory results. The CFD modelling has proven to be very useful in the evaluation of the hydrodynamic conditions of the facultative pond. A virtual tracer test allowed an estimation of the real mean hydraulic retention time and mixing conditions in the pond. The computational model in CFD corresponded well to what was verified in the field.

Experimental Flow Field and Heat Transfer Study of a Slot Jet Reattaching Onto a Flat Plate

2001 ◽  
Author(s):  
V. Narayanan ◽  
J. Seyed-Yagoobi ◽  
R. H. Page
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Surface Pressure ◽  
Local Heat Transfer ◽  
Field Measurements ◽  
Local Heat ◽  
Surface Pressure Distribution ◽  
Mean Pressure ◽  
Transfer Study ◽  
Impingement Surface

Abstract Detailed heat transfer, impingement surface pressure and flow field measurements on a submerged slot jet reattachment nozzle are presented. The nozzle is comprised of a rectangular region of aspect ratio 20:1, with circular ends. The jet exits the nozzle parallel to an adjacent flat impingement surface and reattaches onto it. Contours of local heat transfer exhibit three-dimensionality within the recirculation and reattachment regions with increase in nozzle-to-surface spacing. Mean and time averaged fluctuating surface pressure distribution at the center plane of the nozzle along the minor indicate that the location of peak fluctuating pressure occurs upstream of the peak mean pressure. Flow field measurements are presented for a nozzle-to-surface spacing of 3.85 exit hydraulic diameters from the surface, at a turbulent exit Reynolds number of 10 500. Surface pressure and flow field observations are used to explain heat transfer results in the recirculation and reattachment regions.

scholarly journals Heat Transfer Behaviour and Flow Field Characterisation of Impinging Synthetic Jets for a Wide Range of Parameters

2010 ◽  
Author(s):  
Rayhaan Farrelly ◽  
Alan McGuinn ◽  
Tim Persoons ◽  
Darina Murray
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
High Speed ◽  
Local Heat Transfer ◽  
Field Measurements ◽  
Local Heat ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Flow Measurements ◽  
Wide Range

Impinging synthetic jets are considered as a potential solution for convective cooling, in applications that match their main characteristics (high local heat transfer rates, zero net mass flux, scalability, active control). Nevertheless the understanding of heat transfer to synthetic jets falls short of that available for steady jets. To address this, this paper uses detailed flow field measurements to help identify the main heat transfer mechanisms in impinging synthetic jets. Local heat transfer measurements have been performed for an impinging round synthetic jet at a range of Reynolds numbers between 1000 and 3000, nozzle to plate spacings between 4D and 16D and stroke lengths (L0) between 2D and 32D. The heat transfer results show evidence of distinct regimes in terms of L0/D and L0/H ratios. Based on appropriate scaling, four heat transfer regimes are identified which justifies a detailed study of the flow field characteristics. High speed particle image velocimetry (PIV) has been employed to measure the time-resolved velocity flow fields of the synthetic jet to identify the flow structures at selected L0/H values corresponding to the identified heat transfer regimes. The flow measurements support the same regimes as identified from the heat transfer measurements and provide physical insight for the heat transfer behaviour.

Measurements of Local Heat Transfer Coefficient Over the Full Surface of a Bank of Pedestals With Fillet Radii

1994 ◽  
Author(s):  
Zuolan Wang ◽  
Peter Ireland ◽  
Terry Jones ◽  
S. Toby Kohler
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Field Measurements ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Gas Temperature ◽  
Transfer Method

Complete distributions of local heat transfer coefficient have been measured over the full surface of a pedestal bank at a number of Reynolds numbers. The transient heat transfer method with thermochromic liquid crystals used as the surface thermometer was used to obtain the data. The pedestal geometry included fillet radii representative of those used in engine blade cooling passages. The heat transfer coefficient distributions are compared to previously reported local measurements made on a bank of plain cylinders. Averaged values based on the local mixed bulk gas temperature are compared to established correlations. The distributions of local heat transfer coefficient show a remarkable periodicity when based on a local temperature. These patterns are discussed in terms of the interpreted flow field. Measurements of pressure drop are also reported and, for a range of engine representative Reynolds numbers, agree with an existing correlation for prismatic pedestals.

scholarly journals CFD-modeling of fume formation in kraft recovery boilers

TAPPI Journal ◽  
2013 ◽  
Vol 12 (3) ◽  
pp. 25-32 ◽  
Author(s):  
AINO LEPPÄNEN ◽  
ERKKI VÄLIMÄKI ◽  
ANTTI OKSANEN ◽  
HONGHI TRAN
Keyword(s):  
Field Measurements ◽  
Enrichment Factors ◽  
Cfd Modeling ◽  
Cfd Model ◽  
Metal Chemistry ◽  
Kraft Recovery Boilers ◽  
Recovery Boilers ◽  
Computational Fluid Dynamics Cfd ◽  
Potassium Enrichment ◽  
Particle Mass Concentration

A computational fluid dynamics (CFD) model was developed to simulate alkali metal chemistry and fume particle formation in a kraft recovery boiler. The modeling results were partially validated against previously obtained field measurements. The model provides information about fume composition, chlorine and potassium enrichment factors, and particle mass concentration at different locations in the boiler.

Time Domain Analysis of the Temperatures in an Electrical Auxiliary Building Room

2009 ◽  
Author(s):  
Andron Creary ◽  
Matthew F. King ◽  
Matthew Langston ◽  
Cable Kurwitz ◽  
Paul Nelson ◽  
...  
Keyword(s):  
Air Temperature ◽  
Model Experiment ◽  
Time Domain Analysis ◽  
Lumped Parameter Model ◽  
Scale Model ◽  
Small Scale ◽  
Cfd Model ◽  
Air Temperatures ◽  
Lumped Parameter ◽  
Computational Fluid Dynamics Cfd

A computational fluid dynamics (CFD) model has been developed to predict air temperatures within the switchgear room environment of a nuclear plant’s Electronics Auxiliary Building (EAB). In order to validate the CFD model output, a scale model experiment has been developed using an analytical model to properly scale important EAB room parameters to allow small scale experiments to be performed for validation of the CFD model. The focus of this paper is the development of the methodology used to accurately predict the bulk air temperature or the EAB room. The CFD model is compared to a simple lumped parameter model as well as a scale model experiment. The scaling approach matches the eigenvalues of the lumped parameter model. An experiment based on this scaling approach was performed and compared with CFD output. The time predicted by the CFD model of the Electrical Auxiliary Building room for the average air temperature to increase from 17.7 °C (64 °F) to 40 °C (104 °F) is 23.5 minutes. The lumped parameter analytic solution produces a mean time of 22 minutes. The heat up time for the experiment matches the CFD model providing confidence in the fidelity of the CFD model.

scholarly journals Using CFD Modelling to Relate Pig Lying Locations to Environmental Variability in Finishing Pens

2020 ◽  
Vol 12 (5) ◽  
pp. 1928 ◽  
Author(s):  
Paul Jackson ◽  
Abozar Nasirahmadi ◽  
Jonathan H. Guy ◽  
Steve Bull ◽  
Peter J. Avery ◽  
...  
Keyword(s):  
Environmental Variability ◽  
Weather Conditions ◽  
Environmental Drivers ◽  
Cfd Model ◽  
Air Velocity ◽  
Cfd Modelling ◽  
Video Cameras ◽  
Finishing Pig ◽  
Computational Fluid Dynamics Cfd ◽  
Sequential Regression

The purpose of this research was to determine which environmental factors within the pen space differ between the locations where pigs choose to lie and areas they avoid. Data on external weather conditions and the construction parameters for an existing commercial finishing pig building were input into a Dynamic Thermal (DT) model generating heat flow and surface temperature patterns in the structure and these were then input into a Computational Fluid Dynamics (CFD) model to generate data on the theoretical spatial patterns of temperature and air velocity within one room of this building on a specified day. The exact location of each pig in six selected pens within this room was taken from images from ceiling-mounted video cameras at four representative time points across the day. Using extracted air velocity and temperature data at the height of 0.64 m above the floor and a grid of approximately 600 mm to create a series of ‘cells’, the effective draught temperature (TED) was calculated from the models for each cell. Using a sequential regression model, the extent to which the actual lying locations of the pigs could be reliably predicted from the environmental conditions generated by model outputs and other pen factors was explored. The results showed that air velocity, TED and proximity to a solid pen partition (all significant at P < 0.05) had significant predictive value and collectively explained 15.55% of the total explained deviation of 17.13%. When the presence of an adjacent pig was considered, results showed that lying next to an adjacent pig, TED, air velocity and temperature accounted for 53.9%, 1.3%, 1.5% and 0.5% of the deviation in lying patterns, respectively (all P < 0.001). Thus, CFD model outputs could potentially provide the industry with a better understanding of which environmental drivers affect pigs’ lying location choice, even before a building is built and stocked.

scholarly journals Experimental and CFD Investigation of a Modified Uneven-Span Greenhouse Solar Dryer in No-Load Conditions under Natural Convection Mode

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Abderrahman Mellalou ◽  
Walid Riad ◽  
Salma Kaotar Hnawi ◽  
Abdelaziz Tchenka ◽  
Abdelaziz Bacaoui ◽  
...  
Keyword(s):  
Natural Convection ◽  
Air Temperature ◽  
Weather Conditions ◽  
Cfd Model ◽  
Floor Covering ◽  
Gain Variation ◽  
Covering Material ◽  
The Hours ◽  
Load Conditions ◽  
Good Agreement

An uneven-span modified greenhouse dryer was constructed and tested in no-load conditions under natural convection mode under the weather conditions of Marrakech, Morocco, for two distinct days. Moreover, a CFD evaluation of the uneven-span greenhouse dryer was performed as tool to visualize the air temperature distribution inside the dryer. For validating the CFD model, the temperature variations along the hours of the day were compared to the experimental results. A good agreement is obtained between the computed and measured inside air temperature with a difference not exceeding 8.46°C, with a correlation coefficient ( r ) and root mean square percentage deviations ( e ) 0.94 and 8.17, respectively. Furthermore, the maximum inside air temperature was measured to be 56°C and 52°C while the minimum inside relative humidity was measured to be 17% and 12%, for day-1 and day-2, respectively. The benefice of using asphalt as a floor covering material was revealed as an efficient way to heat the inside air at low solar radiations. The performances of the dryer were evaluated by the percentage of net heat gain variation as a way to validate the effectiveness of the dryer. This latter is found to be equal to 46% and 48% for the two days, respectively.

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