Begell House Inc.
Computational Thermal Sciences: An International Journal
CTS
1940-2503
7
3
2015
APPLICATION OF GENE EXPRESSION PROGRAMMING FOR ESTIMATING TOTAL EMISSIVITY OF H2O−CO2 MIXTURES IN AIR−FUEL COMBUSTION WITHOUT SOOT FORMATION
191-215
10.1615/ComputThermalScien.2015011633
Babak
Maghbooli
Farayand Sabz Engineering Company, No. 117, Somaye Street, Tehran, Iran
Hamidreza
Najafi
Farayand Sabz Engineering Company, No. 117, Somaye Street, Tehran, Iran
Mohammad Amin
Sobati
School of Chemical Engineering, Iran University of Science and Technology (IUST), Postal Box 16765-163, Tehran, Iran
gene expression programming
total gas emissivity
combustion
statistical narrow-band model
water vapor
carbon dioxide
homogenous media
RADCAL
In the present study, a gene expression programming algorithm has been applied to propose new and accurate correlations for estimating total emissivity of CO2−H2O homogeneous mixtures in air−fuel combustion environment without soot formation at atmospheric condition. The main parameters of the correlations include temperature (T: 300−2500 K), partial pressure of water vapor (pw: 2.0265−20.265 kPa), partial pressure of carbon dioxide (pc: 4.053−20.265 kPa), and mean beam length (L: 0.01−25 m). The RADCAL statistical narrow-band model was used in order to generate 78,000 values of total emissivity to be used as the benchmark data for the correlations. 34,620 total emissivity data points were selected for developing the correlations and 43,380 data points were selected for the optimization and testing the capability of the correlations. All the benchmark data were split into two sub-data sets based on temperature (i.e., the first data set: 300 K ≤ T <1200 K, the second data set: 1200 K ≤ T ≤ 2500 K). For each sub-data set, different correlations have been developed. The average absolute relative deviations of the estimated results from the benchmark data are 3.6% of the low temperature, and 3.9% of the high temperature data sets.
PERFORMANCE INVESTIGATION OF AIR WASHER FOR DIFFERENT PSYCHOMETRIC CONDITIONS
217-230
10.1615/ComputThermalScien.2015012415
Sidharth S.
Chakrabarti
OP Jindal University, Raigarh, Chattisgarh, 496001, India
Prasanta Kumar
Das
Department of Mechanical Engineering, Indian Institute of Technology
Kharagpur, Kharagpur 721302, India
evaporation
wet cooling tower
thermal performance
The paper develops an approach for the effective analysis for air washer. The approach can be used for the simultaneous heat and mass transfer in air washers operating as evaporative coolers. By using proper computational technique, the solution has been obtained for the above air washer. The solution gave an excellent match with the results available in the literature. The performance study of the air washer was carried out by varying several essential parameters such as inlet humidity ratio, airflow rate, water inlet temperature, and inlet air dry bulb temperature. The variation of outlet air temperature with respect to water inlet temperature was investigated under different inlet humidity ratio, mass ratio, inlet dry bulb temperature, and length of air washer. It was observed that the efficacy of air washer will increase by reducing inlet water temperature air flow rate and inlet humidity ratio. Further, the results show that the effect of inlet water temperature on the air outlet temperature is more for larger air washer length. The effect of spray ratio on outlet air temperature decreases as the water inlet temperature increases and this effect becomes zero at a particular inlet water temperature.
FINITE DIFFERENCES ANALYSIS ON NONUNIFORM MESH FOR FREE CONVECTION IN A POROUS MEDIUM AND COMPARISON WITH SIMILARITY APPROACH
231-243
10.1615/ComputThermalScien.2015013165
Driss
Achemlal
University of Sidi Mohammed Ben Abdellah, Polydisciplinary Faculty of Taza
M.
Sriti
University of Sidi Mohamed Ben Abdellah, Polydisciplinary Faculty of Taza, LSI, Team of
Numerical Modeling in Mechanics Applied (MNMA), BP.1223, Taza, Morocco
free convection
finite differences method
similarity method
fluid suction/injection
porous medium
In this study, a numerical simulation of steady and laminar free convection flow over a heated vertical flat plate embedded in an unbounded saturated porous medium is presented. A computer program based on the finite differences method, is developed to obtain numerical solutions for resulting governing equations of mass, Darcy, and energy. Afterward, we validated our computational code by comparing the obtained results to those of the similarity approach. Subsequently, we conducted a parametric study of all parameters involved in the problem of heat transfer and flow. This study has been accompanied by the graphic representations and detailed analyses at the physical character.
MAGNETO-THERMOELASTIC RAYLEIGH WAVES IN A PRESTRESSED SOLID HALF-SPACE UNDER HEAT SOURCE USING GREEN AND LINDSAY'S MODEL
245-260
10.1615/ComputThermalScien.2015014069
Shikha
Kakar
Department of Electronics, SBBS University, Padhiana, India
Rajneesh
Kakar
Department of Physics, Adarsh Gurukul, Jalandhar, India
initial stress
magnetic pressure number
thermoelastic coupling
wave number
heat source
An in-depth study has been carried out for the propagation of the Rayleigh waves in thermo-magneto-elastic half-space under the effect of initial stress and heat source. Using GL theory of thermoelasticity, the frequency equation is derived for the said waves under the effect of various technical constants. The wave analysis further indicates that the initial stress, magnetic pressure number, thermoelastic coupling parameter, wave number, and heat source for cadmium material affect the Rayleigh wave velocity remarkably. The obtained results in presence of material parameters are further discussed graphically. The results can be useful to understand the working of highly sensitive thermal stress magnetic sensors.
NUMERICAL INVESTIGATION OF BOUNDARY CONDITION EFFECTS ON LAMINAR NATURAL CONVECTION OF POWER LAW FLUIDS IN SQUARE CROSS-SECTIONAL CYLINDRICAL ANNULAR SPACE WITH DIFFERENTIALLY HEATED VERTICAL WALLS
261-282
10.1615/ComputThermalScien.2015014174
Sahin
Yigit
School of Mechanical and Systems Engineering, Newcastle University, Newcastle-Upon-Tyne, United Kingdom
Joseph
Ford
School of Mechanical and Systems Engineering, Newcastle University, Newcastle-Upon-Tyne, United Kingdom
Robert J.
Poole
School of Engineering, University of Liverpool, Brownlow Hill, Liverpool, L69 3GH, UK
Nilanjan
Chakraborty
School of Mechanical and Systems Engineering, Newcastle University, Newcastle-Upon-Tyne, NE17RU, United Kingdom
Rayleigh number
Prandtl number
Nusselt number
radius-to-height ratio
power law exponent
Axisymmetric numerical simulations have been conducted to analyse steady-state convection of power law fluids in square cross-sectional cylindrical annular space with differentially heated vertical walls for nominal Rayleigh number range 103 ≤ Ra ≤ 106, nominal Prandtl number range 102 ≤ Pr ≤ 104, and power law exponent range 0.6 ≤ n ≤ 1.8 for both constant wall temperature (CWT) and constant wall heat flux (CWHF) boundary conditions. It has been shown that the mean Nusselt number based on the inner periphery Nui increases with decreasing (increasing) power law exponent (nominal Rayleigh number) due to strengthening of thermal advection. However, Nui has been found to be insensitive to the change in nominal Prandtl number. It has been demonstrated that Nui decreases with increasing internal cylinder radius (normalized by its height ri /L) before approaching the mean Nusselt number for a square enclosure in the limit at ri /L → ∞. By contrast, the mean Nusselt number normalized by the corresponding Nusselt number for pure conductive transport (i.e., Nui /Nucond) increases with increasing ri /L. It has been found that Nui assumes smaller values for the CWHF boundary condition than in the CWT boundary condition for the same set of values of nominal Rayleigh and Prandtl numbers, and power law exponent for large values of Ra. Detailed physical explanations have been provided for the observed behavior, and correlations for Nut have been proposed based on scaling arguments, which satisfactorily capture the mean Nusselt number obtained from these steady-state simulations.