Computational Heat Transfer Analysis and Design of Third-World Cookstoves

2009 ◽  
Author(s):  
Alex Wohlgemuth ◽  
Sandip Mazumder ◽  
Dale Andreatta
Keyword(s):  
Heat Transfer ◽  
Thermal Efficiency ◽  
Third World ◽  
Operating Conditions ◽  
Heat Transfer Analysis ◽  
Vertical Position ◽  
Conducting Material ◽  
Unknown Parameters ◽  
Analysis And Design ◽  
Computational Fluid Dynamics Cfd

In many developing countries, natural gas, wood, or biomass fired cookstoves find prolific usage. These cookstoves are constructed without paying much too attention to their thermal efficiency. In this study, a computational heat transfer analysis of a generic third-world cookstove is conducted with the goal to understand the effect of various operating conditions and geometric parameters on the overall heat transfer characteristics and thermal efficiency. A Computational Fluid Dynamics (CFD) model, including turbulence and heat transfer by all three modes, was first created. The model was first validated against experimental data, also collected as part of this study. Unknown parameters in the model were calibrated to better match experimental observations. It is generally believed that placing a skirt around the stove and cook-pot enhances thermal efficiency. The model was explored to study the effects several skirt-related parameters. These include the vertical position of the skirt, the width of the gap between the skirt and the cook-pot, and the thermal conductivity of the skirt (insulating vs. conducting material). It was found that the skirt must either be made out of an insulating material or insulated on the outer surface for it to provide maximum benefits. It was also found that it must be placed at an optimum distance away from the cook-pot for maximum thermal efficiency.

Computational Heat Transfer Analysis of the Effect of Skirts on the Performance of Third-World Cookstoves

2009 ◽  
Vol 1 (4) ◽  
Author(s):  
Alex Wohlgemuth ◽  
Sandip Mazumder ◽  
Dale Andreatta
Keyword(s):  
Heat Transfer ◽  
Thermal Efficiency ◽  
Third World ◽  
Heat Transfer Analysis ◽  
Vertical Position ◽  
Dynamics Model ◽  
Unknown Parameters ◽  
Insulating Layer ◽  
Computational Predictions

In many developing countries, natural gas, wood, or biomass fired cookstoves find prolific usage. Skirts, placed around the cookpot, have been proposed as a means to improve the thermal efficiency. However, use of skirts has shown conflicting results, and the role of skirts is poorly understood. In this study, a computational heat transfer analysis of a generic third-world cookstove is conducted with the goal to understand the effect of various skirt-related parameters on the overall heat transfer characteristics and thermal efficiency. A computational fluid dynamics model, including turbulence and heat transfer by all three modes, was created. The model was first validated against the experimental data, also collected as part of this study. Unknown parameters in the model were calibrated to better match the experimental observations. Subsequently, the model was explored to study the effects of several skirt-related parameters. These include the vertical position of the skirt, the width of the gap between the skirt and the cookpot, and the thermal conductivity of the skirt (insulating versus conducting material). The computational predictions suggest that the skirt must either be made out of an insulating material or insulated on the outer surface by a backing insulating layer for it to provide maximum benefits. It was also found that it must be placed at an optimum distance away from the cookpot and aligned with the mouth of the cookstove chimney for maximum thermal efficiency. An optimum set of conditions obtained through this computational analysis resulted in an increase in the thermal efficiency from 20.7% to 28.7%.

Heat Transfer Analysis of a Novel Pressurized Air Receiver for Concentrated Solar Power via Combined Cycles

2009 ◽  
Vol 1 (4) ◽  
Author(s):  
I. Hischier ◽  
D. Hess ◽  
W. Lipiński ◽  
M. Modest ◽  
A. Steinfeld
Keyword(s):  
Heat Transfer ◽  
Thermal Efficiency ◽  
Porous Ceramic ◽  
Conservation Equation ◽  
Heat Transfer Analysis ◽  
Operational Parameters ◽  
Small Aperture ◽  
Solar Absorber ◽  
Energy Conservation Equation ◽  
Combined Cycles

A novel design of a high-temperature pressurized solar air receiver for power generation via combined Brayton–Rankine cycles is proposed. It consists of an annular reticulate porous ceramic (RPC) bounded by two concentric cylinders. The inner cylinder, which serves as the solar absorber, has a cavity-type configuration and a small aperture for the access of concentrated solar radiation. Absorbed heat is transferred by conduction, radiation, and convection to the pressurized air flowing across the RPC. A 2D steady-state energy conservation equation coupling the three modes of heat transfer is formulated and solved by the finite volume technique and by applying the Rosseland diffusion, P1, and Monte Carlo radiation methods. Key results include the temperature distribution and thermal efficiency as a function of the geometrical and operational parameters. For a solar concentration ratio of 3000 suns, the outlet air temperature reaches 1000°C at 10 bars, yielding a thermal efficiency of 78%.

Heat Transfer Analysis of Human Cell Culture Under RF Exposure

2005 ◽  
Author(s):  
Muhammad Khalid ◽  
Chenn Zhou ◽  
Ashish Bassi ◽  
San Ming Wang ◽  
Howard Gerber ◽  
...  
Keyword(s):  
Gene Expression ◽  
Heat Transfer ◽  
Electric Field ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Heat Transfer Analysis ◽  
Heat Shock Gene ◽  
Exposure System ◽  
Finite Element Software ◽  
Rf Exposure

A 2.45 GHz radio frequency (RF) exposure system was designed and used to study the RF effects on the genome-wide gene expression in cultured human cells. In this system, a T-25 culture flask, which contains 10 × 106 cells in a 10ml medium, is placed in a WR 340 waveguide. The waveguide serves as an environmental chamber. The source is a pulsed magnetron for obtaining a high electric field with the specific absorption rate (SAR) at approximately 10 W/kg. In order to ensure the non-thermal effect, the system was designed to maintain a temperature of 37°C. In this research, the heat transfer analysis of the system was conducted using the computational fluid dynamic (CFD) software FLUENT® coupled with the finite element software, High Frequency Structural Simulation (HFSS) by Ansoft. The electric field was first analyzed by using HFSS to calculate the SAR distribution as a heat source input for CFD calculations. The fluid flow and temperature distributions within the flask were then analyzed using FLUENT®. The results were validated experimentally by measuring the temperatures with fluoroptic thermometer probes as well as by examining the level of heat shock gene expression. These results provide useful information for a better understanding and controlling of the operating conditions of the system.

One-Dimensional Zonal Model for the Unsteady Heat Transfer Analysis in an Open Volumetric Air Receiver

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Gurveer Singh ◽  
Vishwa Deepak Kumar ◽  
Laltu Chandra ◽  
R. Shekhar ◽  
P. S. Ghoshdastidar
Keyword(s):  
Heat Transfer ◽  
High Heat ◽  
Operating Conditions ◽  
Heat Transfer Analysis ◽  
Transfer Model ◽  
High Heat Flux ◽  
Unsteady Heat Transfer ◽  
Volumetric Heating ◽  
One Dimensional ◽  
Zonal Model

Abstract The open volumetric air receiver (OVAR)-based central solar thermal systems provide air at a temperature > 1000 K. Such a receiver is comprised of porous absorbers, which are exposed to a high heat-flux > 800 Suns (1 Sun = 1 kW/m2). A reliable assessment of heat transfer in an OVAR is necessary to operate such a receiver under transient conditions. Based on a literature review, the need for developing a comprehensive, unsteady, heat transfer model is realized. In this paper, a seven-equations based, one-dimensional, zonal model is deduced. This includes heat transfer in porous absorber, primary-air, return-air, receiver casing, and their detailed interaction. The zonal model is validated with an inhouse experiment showing its predictive capability, for unsteady and steady conditions, within the reported uncertainty of ±7%. The validated model is used for investigating the effect of operating conditions and absorber geometry on the thermal performance of an absorber. Some of the salient observations are (a) the maximum absorber porosity of 70–90% may be preferred for non-volumetric and volumetric-heating conditions, (b) the minimum air-return ratio should be 0.7, and (c) the smallest gap to absorber-length ratio of 0.2 should suffice. Finally, suggestions are provided for extending the model.

A 3D SHAPE OPTIMIZATION PROBLEM IN HEAT TRANSFER: ANALYSIS AND APPROXIMATION VIA BEM

2006 ◽  
Vol 16 (08) ◽  
pp. 1243-1270 ◽  
Author(s):  
ANTONELLA ABBÀ ◽  
FAUSTO SALERI ◽  
CARLO D'ANGELO
Keyword(s):  
Heat Transfer ◽  
Shape Control ◽  
Adjoint Equation ◽  
Optimal Shape ◽  
Heat Transfer Analysis ◽  
Industrial Plant ◽  
Flame Surface ◽  
Cost Functional ◽  
Analysis And Design ◽  
Flame Shape

In this paper an optimal shape control problem dealing with heat transfer in enclosures is studied. We have considered an enclosure heated by a flame surface (taking into account radiation, conduction and convection effects), and we look for an optimal flame shape which minimizes a cost functional defined on the temperature field. This kind of problem arises in industrial furnaces optimization, as temperature uniformity is one of the most important aspects in industrial plant analysis and design. Analytical results (smoothness of the control-to-state mapping, existence of an optimal shape in a certain admissible class) as well as numerical optimization results by the boundary element method have been obtained; we have employed the gradient method to optimize the flame shape, exploiting the adjoint equation associated with our state equation and cost functional.

Heat Transfer Analysis of a Novel Pressurized Air Receiver for Concentrated Solar Power Via Combined Cycles

2009 ◽  
Author(s):  
Illias Hischier ◽  
Daniel Hess ◽  
Wojciech Lipin´ski ◽  
Michael Modest ◽  
Aldo Steinfeld
Keyword(s):  
Heat Transfer ◽  
Thermal Efficiency ◽  
Porous Ceramic ◽  
Conservation Equation ◽  
Heat Transfer Analysis ◽  
Operational Parameters ◽  
Small Aperture ◽  
Solar Absorber ◽  
Energy Conservation Equation ◽  
Combined Cycles

A novel design of a high-temperature pressurized solar air receiver for power generation via combined Brayton-Rankine cycles is proposed. It consists of an annular reticulate porous ceramic (RPC) bounded by two concentric cylinders. The inner cylinder, which serves as the solar absorber, has a cavity-type configuration and a small aperture for the access of concentrated solar radiation. Absorbed heat is transferred by conduction, radiation, and convection to the pressurized air flowing across the RPC. A 2D steady-state energy conservation equation coupling the three modes of heat transfer is formulated and solved by the finite volume technique and by applying the Rosseland diffusion, P1, and Monte Carlo radiation methods. Key results include the temperature distribution and the thermal efficiency as a function of the geometrical and operational parameters. For a solar concentration ratio of 3000 suns, the outlet air temperature reaches 1000°C at 10 bars, yielding a thermal efficiency of 78%.

Conjugate Heat Transfer Analysis of a Cooled Turbine Blade Using Frozen Rotor Approach

2015 ◽  
Author(s):  
Kuo-San Ho ◽  
Jong Liu ◽  
Christopher Urwiller ◽  
S. Murthy Konan ◽  
Bruno Aguilar
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
High Performance ◽  
Conjugate Heat Transfer ◽  
Cfd Simulation ◽  
Heat Transfer Analysis ◽  
Research Papers ◽  
Ansys Cfx ◽  
Computational Fluid Dynamics Cfd ◽  
Maximum Temperatures

In recent years, conjugate heat transfer (CHT) computational fluid dynamics (CFD) simulation in turbomachinery played an important role in predicting metal temperature. Most of research papers of CHT CFD simulation were emphasized on the mixing plane method. In this paper the ANSYS CFX 14.0 CHT simulation using the frozen rotor approach is employed to predict the blade temperatures. The frozen rotor included five time instances in which the stator-rotor wake influence could be captured. In this study, the temperature predictions using the frozen rotor approach were compared to the mixing plane predictions and Silicon Carbide (SiC) chip measurements on three different radial spans. The frozen rotor results predicted the minimum and maximum temperatures that bounded the SiC chip data. Compared to the mixing plane predictions, the frozen rotor approach results were similar within 8 K at the mid-span. However, the frozen rotor approach provided more insight information and detailed guidance for model calibration. Finally several future works were suggested to continue striving for high performance gas turbines.

Modeling and Simulation Challenges in Embedded Two Phase Cooling: DARPA’s ICECool Program

2015 ◽  
Author(s):  
Kaiser Matin ◽  
Avram Bar-Cohen ◽  
Joseph J. Maurer
Keyword(s):  
Heat Transfer ◽  
Modeling And Simulation ◽  
Coefficient Of Thermal Expansion ◽  
Operating Conditions ◽  
Electrical Performance ◽  
Two Phase ◽  
Modeling Tools ◽  
Analysis And Design ◽  
System Pressure ◽  
The Impact

Modeling and simulation of two-phase phenomena, as well as their impact on electrical performance and physical integrity are critical to the success of embedded cooling strategies. In DARPA’s Intrachip/Interchip Embedded Cooling (ICECool) program, thermal/electrical/mechanical co-simulation and modeling tools are being applied to the analysis and design of RF GaN MMIC (Monolithic Microwave Integrated Circuit) Power Amplifiers (PA) and digital ICs, with the ultimate goal of achieving greater than 3X electronic performance improvement. This paper addresses various simulation strategies and numerical techniques adopted by the DARPA ICECool performers, with attention devoted to co-simulation through coupled iterations of thermal, mechanical and electrical behavior for capturing device characteristics and predicting reliability and “best in class” simulations that can provide an understanding of device behavior during rugged operating conditions impacted by multi-physics environments. The effect of CTE (Coefficient of Thermal Expansion) mismatch on bond and structural integrity, the impact of cooling fluid choice on performance, the factors affecting erosion/corrosion in the microchannels, as well as electro-migration limits and joule heating effects, will also be addressed. A separate discussion of various two-phase issues, including interface tracking, system pressure drops, conjugate heat transfer, estimating near wall heat transfer coefficients, and predicting CHF (Critical Heat Flux) and dryout is also provided.

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