Experimental and numerical investigations of free convection heat transfer in solar oven

The use of solar energy for baking, heating or drying represents a sustainable way of solar energy applications with negligible negative effects. Solar oven is an alternative to conventional oven that rely heavily on coal and wood or Electric oven that uses the power from the National grid of which the end users have little or no control. Since the Solar oven uses no fuel and it cost nothing to run, it use are widely promoted especially in situations where minimum fuel consumption or fire risks are considered highly important. As useful as the Solar Oven proved, it major setback in the area of applications has been its future sustainability. For the use of Solar Oven/Cookers to be sustained in the future, the design and development of solar oven must rely on sound analytical tools. Therefore, this work focused on the design and development of the solar oven. To test the performance of the Small Solar Oven a 5000cm3 beaker of water was put into the Oven and the temperature of the water was found to reach 810C after about 3hrs under an average ambient temperature of 300C. On no load test, the oven reached a maximum temperature of 112oC in 6hrs. In order to carry out the parametric studies and improve the performance of the Solar Oven, Mathematical models were developed and solved by using Characteristics-Based Split (CBS) Finite Element Method. The Model results were compared with the Experimental results and a good agreement ware found between the two results

A Study on Thermal Performance of Palladium as Material for Passive Heat Transfer Enhancement Devices in Thermal and Electronics Systems

In this work, the thermal behavior of fin made of palladium material under the influences of thermal radiation and internal heat generation is investigated. The thermal model for the extended surface made of palladium as the fin material is first developed and solved numerically using finite difference method. The influences of the thermal model parameters on the heat transfer behaviour of the extended surface are investigated. The results show that the rate of heat transfer through the fin and the thermal efficiency of the fin increase as the thermal conductivity of the fin material increases. This shows that fin is more efficient and effective for a larger value of thermal conductivity. However, the thermal conductivity of the fin with palladium material is low and constant at the value of approximately 75 W/mK in a wider temperature range of -100℃ and 227℃ . Also, it is shown that the thermal efficiencies of potential materials (except for stainless steel and brass) for fins decrease as the fin temperatures increase. This is because the thermal conductivities of most of the materials used for fins decreases as temperature increases.However, keeping other fin properties and the external conditions constant, the thermal efficiency of the palladium is constant as the temperature of the fin increases within the temperature range of -100℃ and 227℃. And outside the given range of temperature, the thermal conductivity of the material increases which increases the efficiency of the fin. The study will assist in the selection of proper material for the fin and in the design of passive heat enhancement devices under different applications and conditions

Nonlinear Vibration Analysis of an Electrostatically Actuated Microbeam using Differential Transformation Method

In this paper, nonlinear vibration of electrostatically actuated microbeam is analyzed using differential transformation method.The high level of accuracy of the analytical solutions of the method was established through comparison of the results of the solutions of exact analytical method, variational approach, homotopy analysis method and energy balance methods. Also,with the aid of the present analytical solution, the time response, velocity variation and the phase plots of the system are presented graphically. It is hope that the method will be widely applied to more nonlinear problems of systems in various fields of study.

Analytical Investigations of Kinetic and Heat Transfer in Slow Pyrolysis of a Biomass Particle

The utilization of biomass for heat and power generation has aroused the interest of most researchers especially those of energy .In converting solid fuel to a USAble form of energy,pyrolysis plays an integral role. Understanding this very important phenomenon in the thermochemical conversion processes and representing it with appropriate mathematical models is vital in the design of pyrolysis reactors and biomass gasifiers. Therefore, this study presents analytical solutions to the kinetic and the heat transfer equations that describe the slow pyrolysis of a biomass particle. The effects of Biot number, temperature and residence time on biomass particle decomposition were studied. The results from the proposed analytical models are in good agreement with the reported experimental results. The developed analytical solutions to the heat transfer equations which have been stated to be “analytically involved” showed average percentageerror and standard deviations 0.439 and 0.103 from the experimental results respectively as compared with previous model in literature which gives average percentage error and standard deviations 0.75 and 0.106 from the experimental results respectively. This work is of great importance in the design of some pyrolysis reactors/units and in the optimal design of the biomass gasifiers

Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of Combustion and Gasification Zones

The prevalent challenges of global warming, food security, food production, crop production systems, environment control called for consideration and better utilization of green energy system such as biomass. The advanced thermo-chemical conversion of the renewable energy source which is aimed at production of optimal yield of energy has not been well understood. In order to have better physical insights into the detailed structure of the biomass burning process inside a solid bed, the kinetics of the biomass combustion and gasification must be properly analyzed. Consequently, improved kinetic models of the combustion and gasification zones in the thermochemical conversion system are very required. Therefore, the present study focuses on the development of improved kinetic modeling of the combustion and gasification zones in the biomass gasification system. The performance of the biomass gasifier system is evaluated through the equivalence ratio, the syngas composition, cold gas efficiency and lower heating value. Also, the effects of the equivalent ratio on gas compositions, the gasifier performance and the low heating value of the biomass are analyzed. From the analysis, it is established that the concentration of CO, H2 and CH4 in the gasifier decrease as the equivalence ratio increases. However, CO2 concentration increases with an increase in the equivalence ratio. The cold efficiency and LHV decreases as the equivalence ratio increases while the gas yield increases with an increase in the equivalence ratio. The quantity of gas produced increases as the amount of oxygen consumed increases. Also, the ratio of CO/CO2 decreases as the temperature of the reduction zone increases. Such analysis as presented in this work, is very useful as a time-saving and cost-effective tool for designing and optimizing the biomass gasifier. Therefore, it is evident that this work will play a significant role in the system design including analysis of the distribution of products and ash deposit in the downdraft gasifiers

Numerical study of performance of porous fin heat sink of functionally graded material for improved thermal management of consumer electronics

YesThe ever-increasing demand for high performance electronic and computer systems has unequivocally called for increased microprocessor performance. However, increasing microprocessor performance requires increasing the power and on-chip power density of the microprocessor, both of which are associated with increased heat dissipation. In recent times, thermal management of electronic systems has gained intense research attention due to increased miniaturization trend in the electronics industry. In the paper, we present a numerical study on the performance of a convective-radiative porous heat sink with functionally graded material for improved cooling of various consumer electronics. For the theoretical investigation, the thermal property of the functionally graded material is assumed as a linear and power-law function. We solved the developed thermal models using the Chebyshev spectral collocation method. The effects of inhomogeneity index of FGM, convective and radiative parameters on the thermal behaviour of the porous heat sink are investigated. The present study shows that increase in the inhomogeneity index of FGM, convective and radiative parameter improves the thermal efficiency of the porous fin heat sink. Moreover, for all values of Nc and Rd, the temperature gradient along the fin of FGM is negligible compared to HM fin in both linear and power-law functions. For comparison, the thermal predictions made in the present study using Chebyshev spectral collocation method agrees excellently with the established results of Runge-Kutta with shooting and homotopy analytical method.Supported in part from PhD sponsorship of the first author by the Tertiary Education Trust Fund of the Federal Government of Nigeria

A Study on the Effects of Internal Heat Generation on the Thermal Performance of Solid and Porous Fins using Differential Transformation Method

In this study, the impacts of internal heat generation on heat transfer enhancement of porous fin is theoretical investigated using differential transform method. The parametric studies reveal that porosity enhances the finheat dissipating capacity but the internal heat generation decreases the heatenhancement capacity of extended surface. Also, it is established that whenthe internal heat parameter increases to some certain values, some negativeeffects are recorded where the fin stores heat rather than dissipating it. Thisscenario defeats the prime purpose of the cooling fin. Additionally, it is established in the present study that the limiting value of porosity parameterfor thermal stability for the passive device increases as internal heat parameter increases. This shows that although the internal heat parameter canhelp assist higher range and value of thermal stability of the fin, it producesnegative effect which greatly defeats the ultimate purpose of the fin. Theresults in the work will help in fin design for industrial applications whereinternal heat generation is involved

Thermal prediction of convective-radiative porous fin heatsink of functionally graded material using adomian decomposition method

YesIn recent times, the subject of effective cooling have become an interesting research topic for electronic and mechanical engineers due to the increased miniaturization trend in modern electronic systems. However, fins are useful for cooling various low and high power electronic systems. For improved thermal management of electronic systems, porous fins of functionally graded materials (FGM) have been identified as a viable candidate to enhance cooling. The present study presents an analysis of a convective–radiative porous fin of FGM. For theoretical investigations, the thermal property of the functionally graded material is assumed to follow linear and power-law functions. In this study, we investigated the effects of inhomogeneity index of FGM, convective and radiative variables on the thermal performance of the porous heatsink. The results of the present study show that an increase in the inhomogeneity index of FGM, convective and radiative parameter improves fin efficiency. Moreover, the rate of heat transfer in longitudinal FGM fin increases as b increases. The temperature prediction using the Adomian decomposition method is in excellent agreement with other analytical and method

Investigation of Simultaneous Effects of Surface Roughness, Porosity, and Magnetic Field of Rough Porous Microfin Under a Convective-Radiative Heat Transfer for Improved Microprocessor Cooling of Consumer Electronics

YesThe ever-increasing demand for high-processing electronic systems has unequivocally called for improved microprocessor performance. However, increasing microprocessor performance requires increasing power and on-chip power density, both of which are associated with increased heat dissipation. Electronic cooling using fins have been identified as a reliable cooling approach. However, an investigation into the thermal behaviour of fin would help in the design of miniaturized, effective heatsinks for reliable microprocessor cooling. The aim of this paper is to investigates the simultaneous effects of surface roughness, porosity and magnetic field on the performance of a porous micro-fin under a convective-radiative heat transfer mechanism. The developed thermal model considers variable thermal properties according to linear, exponential and power laws, and are solved using Chebychev spectral collocation method. Parametric studies are carried using the numerical solutions to establish the influences of porosity, surface roughness, and magnetic field on the microfin thermal behaviour. Following the results of the simulation, it is established that the thermal efficiency of the micro-fin is significantly affected by the porosity, magnetic field, geometric ratio, nonlinear thermal conductivity parameter, thermogeometric parameter and the surface roughness of the micro-fin. However, the performance of the micro-fin decreases when it operates only in a convective environment. In addition, we establish that the fin efficiency ratio which is the ratio of the efficiency of the rough fin to the efficiency of the smooth fin is found to be greater than unity when the rough and smooth fins of equal geometrical, physical, thermal and material properties are subjected to the same operating condition. The investigation establishes that improved thermal management of electronic systems would be achieved using rough surface fins with porosity under the influences of the magnetic field.Supported in part by the Tertiary Education Trust Fund of Federal Government of Nigeria, and the European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN- 2016SECRET-722424