|معرفی دومین سخنران کلیدی همایش|
آقای دکتر امیر فقری به عنوان دومین سخنران کلیدی همایش، معرفی شدند.
Distinguished Professor of Engineering and Distinguished Dean Emeritus of Engineering
School of Engineering, University of Connecticut, 191 Auditorium Rd., Unit 3139, Storrs, CT 06269
Telephone: (860) 377-9402
Email: Amir. Faghri@uconn.edu
Dr. Faghri is currently Distinguished Professor of Engineering and Distinguished Dean Emeritus of Engineering at the University of Connecticut. Dr. Faghri joined the University of Connecticut in 1994 and served as Head of the Mechanical Engineering Department from 1994-1998, and the Dean of the School of Engineering from 1998-2006. Dr. Faghri has authored four books, more than 350 archival technical publications (including over 230 journal papers), and thirteen U.S. patents. Dr. Faghri has served as a principal investigator conducting research in the area of thermal management and multiphase transport phenomena for applications ranging from advanced cooling systems to alternative energy systems, including heat pipes, fuel cells, solar energy systems and thermal energy storage devices. Dr. Faghri has received numerous external research contracts and grants from the National Science Foundation, Department of Energy, National Aeronautics & Space Administration, Department of Defense, Department of Education and various industries. Dr. Faghri is presently serving on the editorial board of seven scientific journals. Dr. Faghri has received many honors and awards, including the American Institute of Aeronautics & Astronautics (AIAA) Thermophysics Award in 1998, the American Society of Mechanical Engineering (ASME) Heat Transfer Memorial Award in 1998, the ASME James Harry Potter Gold Medal In 2005, and the ASME/AIChE Max Jakob Memorial Award in 2010, which is the highest honor in the field of heat transfer. He has served as a consultant to several major research centers and corporations, including Los Alamos and Oak Ridge national laboratories, Exxon Mobil, and Intel Corporation. He presently serves on the boards of directors of both publicly-traded and private companies. Dr. Faghri received his M.S. and Ph.D. degrees from the University of California at Berkeley, and a B.S with highest honors from Oregon State University.
Advances and Opportunities of Integrating Heat Pipe Concepts in Active and Passive Energy Systems
The 21st century will see the development of a wide range of both active and passive energy devices with application in energy management and power sources, electronic cooling, energy storage and bioengineering. Although these energy devices are effective, they are often inefficient and can be improved significantly by integrating heat pipe concepts in their design to enhance efficiency or make them completely passive (no moving parts). Advances and opportunities of integrating heat pipes and thermosyphons concepts in three energy technologies - Thermal Energy Storages, Cooling Towers, and Fuel cells are discussed.
Thermal Energy Storage - Phase Change Materials
Heat transfer devices and methodologies for novel thermal energy storage systems (TES) for various applications including concentrating solar power (CSP) generation systems using latent heat phase change materials (PCMs) are in great demand in the energy field. However, latent heat thermal energy storage PCMs, despite their great potential, suffer from low thermal conductivity. Faghri (1990, 1991) invented two methods to significantly increase the thermal conductivity of PCMs by embedding micro or conventional heat pipes in the PCM for applications in thermal energy storage systems and heat exchangers.
The effect of heat pipes on improving the performance of latent heat thermal energy storage systems has been investigated experimentally and theoretically (Shabgard et al., 2010, 2012, 2013; Robak et al., 2011; Sharifi et al., 2012). The experimental results of Robak et al. (2011) showed 60% to more than 100% increase in the heat transfer rates during melting and solidification, respectively, compared to the fin-assisted storage systems and non-fin, non-heat pipe configurations. Shabgard et al. (2010) developed a thermal network modeling approach for the computationally-efficient simulation of such heat pipe-assisted latent heat thermal energy storage systems. The modeling results showed a similar trend of substantial heat transfer enhancements during charging and discharging of latent heat thermal energy storage systems equipped with heat pipes. The developed thermal network model was later extended by Shabgard et al. (2012, 2013) to simulate a large-scale heat pipe-assisted cascaded latent heat thermal energy storage system for CSP applications. Sharifi et al. (2012) simulated the heat pipe-assisted melting of a PCM in a vertical cylindrical enclosure using detailed full numerical simulation and compared the heat pipe performance with that of rods and hollow tubes. It was found that the heat transfer rates of heat pipe-assisted melting are significantly higher than the two other. Sharifi et al. (2015) extended the simulation of heat pipe-assisted latent thermal energy storage to simultaneous charging and discharging with applications to dish-Stirling CSP systems.
Allen et al. (2015a, 2015b) performed experiments to analyze the melting and solidification of a phase change material (PCM) enclosed in a vertical cylinder with a concentrically located heat pipe surrounded by either aluminum foam or radial aluminum foils, at various orientations. The PCM liquid fraction, temperature distribution, melting and solidification rates, and effectiveness were used to quantify the thermal performance in comparison to a simple rod-PCM configuration. The heat pipe-foil-PCM configuration was reported to have a porosity of 0.957 using 162 foils of thickness 0.024 mm, and attained an overall rate of phase change of about 15 times that of the rod-PCM case, and 10 times that of the heat pipe-PSM configuration.
Areas of minimal freshwater often struggle to provide the large amounts of water required for industrial processes, such as for the cooling of thermoelectric power plants. To decrease the water losses of a typical 500 MWe thermoelectric plant, Benn et al. (2016) proposed two concepts: (1) replacing the existing steam condenser with a direct-dry condenser to provide the phase change and heat rejection of previous once-through and recirculating cooling systems, and (2) replacing the conventional wet cooling towers with completely dry indirect cooling of the re-circulation water stream. For each concept, innovative hybridization of existing systems with closed two-phase thermosyphons allowed for necessary heat transfer of the power cycle. A modular top-down approach to system design allowed for manufacturing and installation simplification, and system performance was considered in terms of thermal and cost analysis. The proposed direct steam condenser with heat rejection to ambient air by Benn et al. (2016) yielded an effectiveness, coefficient of performance, and cost per kWth of 0.55, 376, and 831/kWth , respectively, while the dry indirect cooling tower performance specifications were 0.77, 206, 854/kWth , respectively. Hybrid arrangements of the dry condenser and dry cooling towers were also presented and analyzed, which provide easier retrofit, along with lower costs and greater water savings if combined with existing conventional wet cooling components.
Fuel cells are versatile energy conversion devices with numerous potential applications: large electrical plants, stationary electricity generation, vehicle propulsion, and small portable power (Bahrami and Faghri , 2013; Li and Faghri, 2013; Faghri and Guo, 2005). Two main ways in which heat pipe technology is beneficial for fuel cell development are: using heat pipes in fuel cells as thermal management components, and using the heat pipe concept in fuel cell systems to achieve passive and high-effective fluids-thermal management. The heat generated in a fuel cell stack may be dumped to the atmosphere, but it is often used in other components that require heat. In some cases, the heat is used to run a thermodynamic cycle for additional power generation. Heat pipes can be utilized in fuel cell systems for thermal management purposes, which allow for the effective use of the fuel cell byproduct, heat, leading to a substantial increase in heat transfer and overall system efficiency.
Heat generation in fuel cell stacks presents challenges for thermal management. Stacks operating at 40% to 60% efficiency generate heat at the rate of more than twice the rate of electric generation. Due to changes in mass concentration, temperature gradients, and in some cases, phase change throughout the stack, heat generation is not uniform. Non-uniform heat generation further increases thermal gradients in the stack. Increasing the mobility of the heat is a challenge that, if met, leads to three important benefits: (1) the risk of stack failure due to overheating is reduced, (2) the stack operates more closely to its design temperature, resulting in better power density and efficiency, and (3) the heat can be reused, perhaps for reactant preheating, pre-vaporization, combined cycle operation, or cogeneration. For example, the heat pipe embedded with a bipolar plate (Faghri and Guo, 2008) is an innovative approach that would increase heat transfer in fuel cell stacks while requiring significantly smaller thermal gradients and much smaller volumes and weights than alternative methods.Another method for thermal control in the fuel cell stack is presented with the integrated bipolar plate flat heat pipe .
Passive DMFC technology uses various capillary approaches to manage methanol and water without the need for a complex micro-fluidic subsystem (Huang and Faghri ,2014; Huang et al. 2014 ; Bahrami and Faghri , 2013; Li and Faghri , 2013; Guo and Faghri, 2006a, 2006b; Rice and Faghri, 2006). At the core of this new technology is a unique passive system that uses the heat pipe concept for fuel delivery. Furthermore, the fuel cell is designed for both passive water management and effective carbon dioxide removal. The passive components that are critical to the fuel cell design are the fuel delivery, air-breathing, and water recirculation systems. The passive fuel delivery system stores pure methanol, which can be mixed with water in situ without the use of a pumping system, and can be passively supplied to the anode. This water recirculation, in conjunction with the passive methanol fuel delivery, can dramatically extend the operation time of the fuel cell per refueling. The passive mass transfer concept (wick structure) developed in heat pipe technology is an effective approach for mass transfer management in various fuel cell technologies. The proposed DMFC technologies developed were operated passively, without moving parts, which resulted in a highly reliable system. Due to their significantly longer charging life, passive miniature DMFC systems are being considered for replacing the battery in applications such as cell phones, digital cameras and laptops.
M. Allen, T. L. Bergman, A. Faghri, and N. Sharifi, 2015a, “Robust Heat Transfer Enhancement During Melting and Solidification of a Phase Change Material Using a Combined Heat Pipe-Metal Foam or Foil Configuration,” Journal of Heat Transfer, Vol. 137, No. 102301-1.
M. Allen, N. Sharifi, A. Faghri, and T. L. Bergman, 2015b, “Effect of Inclination Angle During Melting and Solidification of a Phase Change Material Using a Combined Heat Pipe-Metal Foam or Foil Configuration,” International Journal of Heat and Mass Transfer, Vol. 80, pp. 767-780.
Bahrami, H., and Faghri, A., 2013 ,“Review and Advances on Direct Methanol Fuel Cells (DMFCs), Part II: Modelling and Numerical Solutions,” Journal of Power Sources, Vol. 230,pp. 303-320
S.P. Benn, L.M. Poplaski, A. Faghri, T.L. Bergman, 2016, “Analysis of Thermosyphon/Heat Pipe Integration for Feasibility of Dry Cooling for Thermoelectric Power Generation,” Applied Thermal Engineering, Vol. 104, pp.358-374
A. Faghri, 1990, “Thermal Energy Storage Heat Exchangers,” U.S. Patent Number 4976308.
A. Faghri, 1991, “Micro Heat Pipe Energy Storage Systems,” U.S. Patent Number 5000252.
A. Faghri and Z. Guo, 2005, “Challenges and Opportunities of Thermal Management Issues Related to Fuel Cell Technology and Modeling,” International Journal of Heat and Mass Transfer, Vol. 48, pp 3891-3920
A. Faghri and Z. Guo, 2008, “Integration of Heat Pipes into Fuel Cell Technology,” Heat Transfer Energy, Vol. 29, No. 3, pp. 232-238
Z. Guo, A. Faghri, 2006a, “Development of Planar Air Breathing Direct Methanol Fuel Cell Stacks,” Journal of Power Sources, 160, pp. 1183-1194
Z. Guo, A. Faghri, 2006b, “Miniature DMFCs with Passive Thermal-Fluids Management System,” Journal of Power Sources, 160, pp. 1142-1155
Huang, J., Bahrami, H., and Faghri, A., 2014, " Analysis of a Permselective Membrane-Free Alkaline Direct Ethanol Fuel Cell,” Journal of Fuel Cell Science and Technology," Vol., 11, No. 2
Huang, J. and Faghri, A., 2014,“Comparison of Alkaline Direct Ethanol Fuel Cells with and without Anion Exchange Membrane” Journal of Fuel Cell Science and Technology, Vol., 11, No., 5
Li, X.L., and Faghri, A.,2013 “Review and Advances on Direct Methanol Fuel Cells (DMFCs), Part I: Design, Fabrication, and Testing with High Concentration Methanol Solutions,” Journal of Power Sources, Vol. 226,, pp. 223-240.
Rice, J., and Faghri, A.,2006, “A Transient, Multiphase and Multi-Component Model of a New Passive Miniature DMFC,” International Journal of Heat and Mass Transfer, Vol. 49, pp. 4804-4820
C.W. Robak, T. L. Bergman, and A. Faghri, 2011, “Enhancement of Latent Heat Energy Storage using Embedded Heat Pipes,” International Journal of Heat and Mass Transfer, 54(15-16), 3476-3484
H. Shabgard, T. L. Bergman, N. Sharifi, and A. Faghri, 2010, “High Temperature Latent HeatThermal Energy Storage using Heat Pipes,” International Journal of Heat and Mass Transfer, 53(15-16), 2979-2988
H. Shabgard, CW Robak, T.L. Bergman, and A. Faghri, 2012, “Heat Transfer and EnergyAnalysis of Cascaded Latent Heat Storage with Gravity-Assisted Heat Pipes for Concentrating Solar Power Applications,” Solar Energy, Vol. 86, Issue 3, pp. 816-830
H. Shabgard, T. L. Bergman, and A. Faghri, 2013, “Exergy Analysis of Latent Heat Thermal Energy Storage for Solar Power Generation Accounting for Constraints Imposed by Long-term Operation and the Solar Day,” Energy, Vol. 60, pp. 474-484
N. Sharifi, A. Faghri, T.L. Bergman, and Charles E. Andraka, 2015, “Simulation Heat Pipe Assisted Latent Heat Thermal Energy Storage with Simultaneous Charging and Discharging,” International Journal of Heat and Mass Transfer, Vol. 80, pp. 170-179