scholarly journals CFD Simulation of Convective Heat Transfer on Vernacular Sustainable Architecture: Validation and Application of Methodology

2019 ◽  
Vol 11 (15) ◽  
pp. 4231
Author(s):  
Wenzhou Zhong ◽  
Tong Zhang ◽  
Tetsuro Tamura
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Flow Field ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Vernacular Architecture ◽  
Building Design ◽  
Building Model

The global background of energy shortages and climate deterioration demands bioclimatic sustainable buildings. Vernacular architecture can provide a useful resource of passive strategies and techniques for creating inner comfort conditions with minimum heating, ventilation, and air conditioning (HVAC) assistance. The identification and verification of such knowledge are essential for climate responsive or energy passive building design. Among the methods, computational fluid dynamics (CFD) is a useful tool for simulating convective heat transfer of vernacular architecture and predicting the convective heat transfer coefficient (CHTC) and flow field. Geometric complexity and diversity of building samples are crucial in the development of an effective simulation methodology in terms of computational cost and accuracy. Therefore, this paper presents high-resolution 3D steady Reynolds-averaged Navier–Stokes (RANS) CFD simulations of convective heat transfer on Japanese vernacular architecture, namely, “machiya.” A CFD validation study on the CHTC is performed based on wind-tunnel experiments on a cube heated by constant heat flux and placed in a turbulent channel flow with a Reynolds number of 3.3 × 104. Three steady RANS models and two boundary layer modeling approaches are compared and discussed. Results show that the SST k-ω model applied with low Reynolds number modeling approach is suitable for CHTC simulations on a simplified building model. The RNG k-ε model applied with wall functions is an appropriate choice for simulating flow field of a complicated building model. Overall, this study develops a methodology involving RANS model selection, boundary layer modeling, and target model fitting to predict the convective heat transfer on vernacular architecture.

scholarly journals Determination of Heat Transfer Coefficients Over Ribbed Surfaces With Infrared Thermography

1997 ◽  
Author(s):  
Francisco P. Brójo ◽  
Luís C. Gonçalves ◽  
Pedro D. Silva
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Stanton Number ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The scope of the present work is to characterize the heat transfer between a ribbed surface and an air flow. The convective heat transfer coefficients, the Stanton number and the Nusselt number were calculated in the Reynolds number range, 5.13 × 105 to 1.02 × 106. The tests were performed inside a turbulent wind tunnel with one roughness height (e/Dh = 0.07). The ribs had triangular section with an attack angle of 60°. The surface temperatures were measured using an infrared (IR) thermographic equipment, which allows the measurement of the temperature with a good spatial definition (10.24 × 10−6 m2) and a resolution of 0.1°C. The experimental measures allowed the calculation of the convective heat transfer coefficient, the Stanton number and the Nusselt number. The results obtained suggested a flow pattern that includes both reattachment and recirculation. Low values of the dimensionless Stanton number, i.e. Stx*, are obtained at the recirculation zones and very high values of Stx* at the zones of reattachment. The reattachment is located at a dimensionless distance of 0.38 from the top of the rib. That distance seems to be independent of the Reynolds number. The local dimensionless Stanton number remains constant as the Reynolds number varies. The convective heat transfer coefficient presents an uncertainty in the range of 3 to 6%.

Gas Solids Suspension Convective Heat Transfer at a Reynolds Number of 130,000

1968 ◽  
Vol 90 (4) ◽  
pp. 464-468 ◽  
Author(s):  
R. Briller ◽  
R. L. Peskin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Particle Temperature ◽  
Convective Heat Transfer Coefficient ◽  
Loading Ratio ◽  
High Reynolds

An experiment was performed to determine the convective heat-transfer coefficient to heated and cooled gas solids suspensions at a Reynolds number of 130,000. Measurements of the heat transfer were performed by traversing the stream at various locations along the pipe with specially designed probes which measured air and particle temperature locally. The results showed that for a high Reynolds number, the heat-transfer coefficient for the suspension appears to be equal to that of the pure gas at the same Reynolds number, and independent of solids loading ratio, heating or cooling, and particle size (between 0.0011 and 0.0058 in. dia).

Heat Transfer Characteristics of an Array of Impinging Gaseous Slot Jets

2011 ◽  
Vol 396-398 ◽  
pp. 2234-2239
Author(s):  
Zu Ling Liu ◽  
Cheng Bo Wu ◽  
Xian Jun Wang ◽  
Zheng Rong Zhang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Nozzle Exit ◽  
Convective Heat Transfer Coefficient ◽  
Heat Transfer Characteristics ◽  
Forced Convective Heat Transfer

A comprehensive experiment was conducted for heat transfer characteristics for an array of impinging gaseous slot jets to a flat plate with strong turbulence (nozzle exit Reynolds number Re=22500~64700).Find that turbulence intensity of flow has an important influence on local forced convective heat transfer coefficient. Meanwhile, the nozzle-to-plate spacing and nozzle exit Reynolds number Re would affect the mean forced convective heat transfer coefficient of the slot jets. And heat transfer efficiency of slot jets has been set to show the relation between ability of the jets and energy consumption of gas supply.

Effect of Volume Fraction of Nanoparticles to the Convective Heat Transfer of Nanofluids

2011 ◽  
Vol 464 ◽  
pp. 528-531 ◽  
Author(s):  
Zhi Yong Ling ◽  
Tao Zou ◽  
Jian Ning Ding ◽  
Guang Gui Cheng ◽  
Peng Fei Fu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Volume Fraction ◽  
Small Difference ◽  
Numerical Study ◽  
Convective Heat Transfer Coefficient ◽  
Full Development ◽  
Significant Difference

A numerical study on the convective heat transfer characteristics of Cu-water nanofluid under the laminar flow condition was performed. The results show that the convective heat transfer coefficient increases with the increase of the volume fraction of the nanoparticles and the Reynolds number. There is a significant difference between the numerical simulation result and the result calculated from the Shah equation in the entrance region, but a small difference in full development areas. The numerical results agree well with that obtained from the Xuan equation when the Reynolds number and the volume fraction of the nanoparticles are small, but the errors between them increase as the increase of the Reynolds number and the volume fraction of nanoparticles.

scholarly journals Investigation on Heat Transfer and Pressure Drop Performance Utilizing GNP-based Colloidal Suspension Flow in Finned Conduit

2021 ◽  
Vol 945 (1) ◽  
pp. 012056
Author(s):  
Yanru Wang ◽  
Cheen Sean Oon ◽  
Manh-Vu Tran ◽  
Joshua Yap Kee An
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Colloidal Suspension ◽  
Convective Heat Transfer Coefficient ◽  
Constant Heat Flux

Abstract Heat exchangers have been widely used in various engineering applications. It is important to develop a highly efficient heat transfer equipment to reduce carbon footprint. In the current research, the effect of 0.025wt% CGNP/water nanofluid on convective heat transfer and pressure drop performance is investigated numerically in finned conduits with circular and square geometry. ANSYS FLUENT is used to analyze the turbulent flow inside the conduits with Reynolds number ranging from 7360 to 28011 and constant heat flux 12254.90W/m2 and 9615.38W/m2 in circular and square geometry, respectively. Only 1/8 of the pipe was constructed in the simulation as the geometry is symmetrical. The numbers of mesh elements are 465488 and 469144 for circular and square conduits. SST k-omega viscous model, SIMPLEC scheme and second-order upwind solvers are used in this model, where SST k-omega viscous model is good at solving turbulence parameters in the near wall boundary regions. It is found that the use of CGNP/water nanofluid can increase convective heat transfer coefficient without increasing pressure drop compared with water. Besides, the circular pipe shows higher heat transfer enhancement compared with square pipe. Furthermore, the increase in Reynolds number enhances the Nusselt number and heat transfer coefficient in both circular and square geometries. It is recommended that circular finned pipe and CGNP/water colloidal suspension could be applied in low turbulence flow setting heat exchanger.

Numerical Investigation of Convective Heat Transfer of Refined Kerosene-Alumina Nanofluid Under Laminar and Turbulent Regime

2018 ◽  
Vol 24 (8) ◽  
pp. 5543-5547
Author(s):  
Aldin Justin Sundararaj ◽  
B. C Pillai ◽  
Austin Lord Tennyson ◽  
Allison Edward ◽  
Bhaskar Gupta
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Computational Models ◽  
Volume Concentration ◽  
Convective Heat Transfer Coefficient ◽  
Nano Particles ◽  
Phase Model ◽  
Turbulent Regime

The study reports Computational Fluid Dynamics (CFD) investigations of the convective heat transfer coefficient of Al2O3/refined kerosene nanofluids. The study was carried out under laminar and turbulent regime in a circular tube under uniform and constant heat flux on the wall. The study was carried out for Re 500 to 5500 for base refined kerosene and with alumina added with 0.01% and 0.05% volume concentration in the base refined kerosene. The size of the alumina nanoparticle was 35 nm. Different computational models of Ansys-Fluent were used for the study. For laminar flows, laminar viscous models and K-Epsilon model for turbulence modelling was used. Energy model was used to define convective heat transfer and a discrete phase model to study particle behaviour and flow pattern in the tube. Multi-phase model with two phase refined kerosene suspended with alumina nano particles were used for the study. Experimental and simulation results showed that as the Reynolds number and the particle concentration increased there was an enhancement in the thermal performance of nanofluids which was found to be higher than that of the base fluid. The convective heat transfer increased by 14% for volume concentration of 0.05% and Reynolds number of 5500.

scholarly journals A variational method in the problem of convective heat transfer near the vertical plane of the outer building fence in terms of free air movement

2018 ◽  
Vol 170 ◽  
pp. 03012 ◽  
Author(s):  
Andrey Aksenov
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Convection ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Plane Surface ◽  
Convective Heat Transfer Coefficient ◽  
Vertical Plane ◽  
Vertical Component ◽  
Irreversible Processes

An unconventional method for solving the heat transfer problem for free convection near the vertical surfaces of the enclosing structures is proposed. It is based on the laws of thermodynamics of irreversible processes. A variational principle is used to find the unknown functions that analytically express the velocity fields and other flow quantities in the boundary layer near the vertical walls. A variational formulation of the hydrodynamic and thermal boundary layer near a vertical plane surface in conditions of free convection is given. It is given an analytical solution of the problem of the distribution of the vertical component of velocity and temperature in the wall boundary layer in the laminar flow. Theoretical formulas for the thickness of the boundary layer are obtained, as well as for the local and mean values of convective heat transfer coefficient.

scholarly journals SIMULATION OF HEAT TRANSFER FROM CANOPY SURFACES USING LOW-REYNOLDS NUMBER K-ε MODEL

2015 ◽  
pp. 186-191 ◽  
Author(s):  
Sivaraja Subramania Pillai ◽  
Ryuichiro Yoshie
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Wind Tunnel ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Low Reynolds Number ◽  
Convective Heat Transfer Coefficient ◽  
Low Reynolds

This study focuses on the Convective Heat Transfer Coefficient (CHTC) from urban building surfaces by numerical simulation. The heat transfer effects because of various geometrical and physical properties of urban areas exhibits a differential heating and uncomfortable environment compared to rural regions called as Urban Heat Island (UHI) phenomena. Investigation of Convective heat transfer coefficient becomes more important in the study of urban heat island phenomena. Experimental simulation of urban area with various urban canopy cases in thermally stratified wind tunnel is employed for the heat transfer kind of investigations in urban area. But, it is not an easy task in wind tunnel experiments to evaluate local CHTC, which vary on individual canyon surfaces transfer such as building roof, walls and ground. Numerical simulation validated by wind tunnel experiments can be an alternative for the prediction of CHTC from building surfaces in an urban area. In our study, Water evaporation technique used in wind tunnel experiment for the evaluation of convective heat transfer coefficient and naphthalene sublimation technique conducted by other researchers are used to validate the low-Reynolds-number k-ε model which was used for the evaluation of CHTC from surfaces. The calculated CFD results showed good agreement with both water evaporation technique and naphthalene sublimation experimental results. It is found that the low-Reynolds-number k-ε model is reliable for the investigations pertaining to heat transfer from urban canopy.

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