scholarly journals Assessment of Haar Wavelet-Quasilinearization Technique in Heat Convection-Radiation Equations

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Umer Saeed ◽  
Mujeeb ur Rehman
Keyword(s):  
Heat Transfer ◽  
Haar Wavelet ◽  
Variable Thermal Conductivity ◽  
The Other ◽  
Wavelet Method ◽  
Combined Convection ◽  
Transfer Equations ◽  
Quasilinearization Technique ◽  
Good Agreement ◽  
Distribution Equation

We showed that solutions by the Haar wavelet-quasilinearization technique for the two problems, namely, (i) temperature distribution equation in lumped system of combined convection-radiation in a slab made of materials with variable thermal conductivity and (ii) cooling of a lumped system by combined convection and radiation are strongly reliable and also more accurate than the other numerical methods and are in good agreement with exact solution. According to the Haar wavelet-quasilinearization technique, we convert the nonlinear heat transfer equation to linear discretized equation with the help of quasilinearization technique and apply the Haar wavelet method at each iteration of quasilinearization technique to get the solution. The main aim of present work is to show the reliability of the Haar wavelet-quasilinearization technique for heat transfer equations.

Optimal Perturbation Iteration Method for Solving Nonlinear Heat Transfer Equations

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Sinan Deniz
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Iteration Method ◽  
Numerical Solutions ◽  
Nonlinear Differential Equations ◽  
Optimal Perturbation ◽  
Transfer Equations ◽  
Better Than ◽  
Good Agreement ◽  
Distribution Equation

In this paper, the new optimal perturbation iteration method (OPIM) is introduced and applied for solving nonlinear differential equations arising in heat transfer. The effectiveness of the proposed method will be tested by considering two specific applications: the temperature distribution equation in a thick rectangular fin radiation to free space and cooling of a lumped system with variable specific heat. Comparing different methods shows that the results obtained by optimal perturbation iteration method are very good agreement with the numerical solutions and perform better than the most existing analytic methods.

scholarly journals Effect of temperature-dependency of surface emissivity on heat transfer using the parameterized perturbation method

2011 ◽  
Vol 15 (suppl. 1) ◽  
pp. 123-125 ◽  
Author(s):  
Maziar Jalaal ◽  
Esmaiil Ghasemi ◽  
Domiri Ganji ◽  
Hasan Bararnia ◽  
Soheil Soleimani ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Perturbation Method ◽  
Industrial Processes ◽  
Effect Of Temperature ◽  
Temperature Dependency ◽  
Surface Emissivity ◽  
Runge Kutta Method ◽  
Transfer Equations ◽  
Parameterized Perturbation Method ◽  
Good Agreement

Knowledge of the temperature dependence of the physical properties such surface emissivity, which controls the radiative problem, is fundamental for determining the thermal balance of many scientific and industrial processes. The current work studies the ability of a strong analytical method called parameterized perturbation method (PPM), which unlike classic perturbation method do not need small parameter, for nonlinear heat transfer equations. The results are compared with the numerical Runge-Kutta method showed good Agreement.

scholarly journals Analysis of non-Fourier thermal behavior for multi-layer skin model

2011 ◽  
Vol 15 (suppl. 1) ◽  
pp. 61-67 ◽  
Author(s):  
Kuo-Chi Liu ◽  
Po-Jen Cheng ◽  
Yan-Nan Wang
Keyword(s):  
Heat Transfer ◽  
Wave Model ◽  
Bioheat Transfer ◽  
Phase Lag ◽  
Dual Phase ◽  
Order Partial Differential Equation ◽  
Transfer Equations ◽  
Lag Model ◽  
Fourier Equation ◽  
Good Agreement

This paper studies the effect of micro-structural interaction on bioheat transfer in skin, which was stratified into epidermis, dermis, and subcutaneous. A modified non-Fourier equation of bio-heat transfer was developed based on the second-order Taylor expansion of dual-phase-lag model and can be simplified as the bio-heat transfer equations derived from Pennes? model, thermal wave model, and the linearized form of dual-phase-lag model. It is a fourth order partial differential equation, and the boundary conditions at the interface between two adjacent layers become complicated. There are mathematical difficulties in dealing with such a problem. A hybrid numerical scheme is extended to solve the present problem. The numerical results are in a good agreement with the contents of open literature. It evidences the rationality and reliability of the present results.

Laminar Natural Convection in an Inclined Rectangular Box With the Lower Surface Half-Heated and Half-Insulated

1983 ◽  
Vol 105 (3) ◽  
pp. 425-432 ◽  
Author(s):  
P. K.-B. Chao ◽  
H. Ozoe ◽  
S. W. Churchill ◽  
N. Lior
Keyword(s):  
Heat Transfer ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Lower Surface ◽  
The Other ◽  
Uniform Temperature ◽  
Side Walls ◽  
Laminar Natural Convection ◽  
Rayleigh Numbers ◽  
Good Agreement

The pattern of circulation and the rate of heat transfer were determined experimentally and also by three-dimensional, finite-difference calculations for an inclined 2 × 1 × 1 rectangular enclosure with a 1 × 1 segment of the lower 2 × 1 surface at a uniform temperature, the other 1 × 1 segment and four side walls insulated, and the upper surface at a lower uniform temperature. As contrasted with an enclosure heated and cooled on the horizontal surfaces, a fluid motion occurs and the rate of heat transfer exceeds that for pure conduction for all temperature differences and orientations. The effects of elevation of the heated and insulated segments were investigated, as well as of inclination about the longer dimension. Despite differences in the Prandtl and Rayleigh numbers, the observed and predicted patterns of circulation are in good agreement, and the measured and predicted rates of heat are in qualitative agreement.

scholarly journals Simulation of shell and tube heat exchanger using COMSOL software

2021 ◽  
Vol 947 (1) ◽  
pp. 012008
Author(s):  
Trung Kim Nguyen ◽  
Tuan Nguyen Ba ◽  
Pha Bui Ngoc ◽  
Abdul Mutalib Embong ◽  
Ngoc Nguyen Thi Nhu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Conclusive Evidence ◽  
Pressure Drops ◽  
Tube Heat Exchanger ◽  
Water Flows ◽  
Proposed Model ◽  
Transfer Equations ◽  
Shell And Tube ◽  
Good Agreement

Abstract The aim of this paper is to propose a model to simulate the behaviour of water flows in shell and tube heat exchanger. Particularly, the continuity equation, the general heat transfer equations and the energy equation in COMSOL Multiphysics software were implemented in the numerical modelling. Besides, the experiment was also conducted to validate the proposed COMSOL model. The water temperature at locations close to the inlet and outlet of the shell side was respectively predicted at 31.5°C and 34.6°C in the simulation, and it was respectively measured at 31.5°C and 35°C in the experiment. These findings showed that the simulation results had a good agreement with the experiment. Next, this model was extended to simulate the overall heat coefficient and the pressure drops of the water flows in such heat exchanger. The overall heat coefficient was at 736.62 W/m2K. The pressure drops at the inlet/outlet areas of the shell and tubes were at 849.93 Pa and 6255.50 Pa, respectively. Conclusive evidence showed that the proposed model is a reliable method for studying the heat transfer behaviour of the shell and heat exchanger.

Analysis of Heat Transfer by Natural Convection Across Vertical Fluid Layers

1977 ◽  
Vol 99 (2) ◽  
pp. 287-293 ◽  
Author(s):  
G. D. Raithby ◽  
K. G. T. Hollands ◽  
T. E. Unny
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Average Nusselt Number ◽  
Vertical Temperature ◽  
The Core ◽  
Aspect Ratios ◽  
Fluid Layers ◽  
Transfer Equations ◽  
Vertical Temperature Distribution ◽  
Good Agreement

An analysis is presented which predicts the heat transfer across fluid layers bounded laterally by vertical isothermal surface and adiabatic surfaces on the top and bottom. The vertical temperature distribution in the core of the cavity is also predicted. Extensive comparisons of average Nusselt number and temperature distribution are made with experimental data for aspect ratios greater than 5. Good agreement between analysis and experiment is found. The heat-transfer equations for vertical layers are generalized to include layers which are tilted up to 20° from the vertical, making the results useful for the design of solar collectors.

scholarly journals Comparison of aerosol LIDAR retrieval methods for boundary layer height detection using ceilometer backscatter data

2016 ◽  
Author(s):  
Vanessa Caicedo ◽  
Bernhard Rappenglueck ◽  
Barry Lefer ◽  
Gary Morris ◽  
Daniel Toledo ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Gradient Method ◽  
Haar Wavelet ◽  
Cluster Method ◽  
Wavelet Method ◽  
Haar Wavelet Method ◽  
Boundary Layer Height ◽  
Cluster Analysis Method ◽  
Aerosol Backscatter ◽  
Good Agreement

Abstract. Three algorithms for estimating the boundary layer heights are assessed: an aerosol gradient method, a cluster analysis method, and a Haar wavelet method. Over 40 daytime radiosonde profiles are used to compare aerosol backscatter boundary layer heights retrieved by a Vaisala CL31 ceilometer. Overall good agreement between radiosonde and aerosol derived boundary layer heights was found for all methods. The cluster method was found to be particularly sensitive to noise in ceilometer signals and lofted aerosol layers (48.8 % of comparisons), while the gradient method showed limitations in low aerosol backscatter conditions. The Haar Wavelet method demonstrating to be the most robust only showing limitations (22.5 % of all observations) due to the basic assumptions used to derive BLH from aerosol backscatter concentrations rather than errors with the algorithm itself. Disagreement between thermodynamically and aerosol derived boundary layer heights and the methodology used to estimate these heights was seen with all methods.

Numerical Study of the Effects of Volumetric Heat Transfer and Emissivity Coefficient and Porosity on Combustion and Pollutants Formation in a Porous Burner

2008 ◽  
Author(s):  
Siamak Hossainpour ◽  
Bahman Haddadi
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
High Power ◽  
Numerical Study ◽  
The Other ◽  
Porous Burner ◽  
Co Emission ◽  
Solid Temperature ◽  
Emissivity Coefficient ◽  
Good Agreement

In recent years, more attention has been focused on the use of porous materials to enhance the efficiency of combustion systems and to reduce the emission of pollutants. This is because combustion in inert porous media offers an interesting and promising route towards burner with high-power density, high-power dynamic range, and very low emission of pollutants such as NOx and CO. This work reports one-dimensional combustion in a porous burner using three combustion models: GRI 3.0, GRI 2.11, skeletal mechanism. We conclude that GRI 2.11 mechanism has a good agreement with GRI 3.0 and it costs less. At first, we present a numerical study which shows the effects of these models on temperature, species and pollutant emissions. Then, we investigate the effects of volumetric heat transfer and emissivity coefficient and porosity on combustion and pollutions. It was concluded that NO and CO emission depend mainly on the volumetric and emissivity coefficient. When volumetric heat transfer increased, the difference between gas and solid temperature reduced, therewith NO formation noticeably decreased whereas CO emission didn’t change sensible. On the other hand, the flame peak temperature is increased with the reduction of the solid emissivity coefficient. This important conclusion means that NO and CO emission and velocity increases. Also gas and solid temperature increase and vice versa. The other parameter is Porosity. Increasing in porosity of burner resulted in decreasing gas and solid temperature and subsequently NO and CO emission decreased sensible. Porosity has effected on velocity, too. As porosity decreased, velocity increased. Emissivity effects on the rate of heat flux which issue from burner. As the emissivity increased the efficiency of burner arose. Also these parameters have important roles in decreasing the emission especially on No emission because it has more depend on temperature. In addition the resulted gas and solid temperatures were compared with reported measurements of center line temperature in a cylindrical porous burner. The good agreement with experimental observation upholds that the numerical model is a perfect tool to investigate combustion and pollutants formation in porous media.

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