Thermoelectric Heat Exchanger Research Articles

Enhanced Heat Transfer in Thermoelectric Generator Heat Exchanger for Sustainable Cold Chain Logistics: Entropy and Exergy Analysis

This study investigates the application of thermoelectric power generation devices in conjunction with cold chain logistics transport vehicles, focusing on their efficiency and performance. Our experimental results highlight the impact of thermoelectric module characteristics, such as thermal conductivity and the filling thickness of copper foam, on the energy utilization efficiency of the system. The specific experimental setup involved a simulated logistics cold chain transport vehicle exhaust waste heat recovery thermoelectric power generation system, consisting of a high-temperature exhaust heat exchanger channel and two side cooling water tanks. Thermoelectric modules (TEMs) were installed between the heat exchanger and the water tanks to use the temperature difference and convert heat energy into electrical energy. The analysis demonstrates that using high-performance thermoelectric modules with a lower thermal conductivity results in better utilization of the temperature difference for power generation. Additionally, the insertion of porous metal copper foam within the heat exchanger channel enhances convective heat transfer, leading to an improved performance. Furthermore, the study examines the concepts of exergy and entropy generation, providing insights into the system energy conversion processes and efficiency. Overall, this research offers valuable insights for optimizing the design and operation of thermoelectric generators in cold chain logistics transport vehicles to enhance energy utilization and sustainability.

Enhancing Ocean Thermal Energy Conversion Performance: Optimized Thermoelectric Generator-Integrated Heat Exchangers with Longitudinal Vortex Generators

The effective utilization of renewable energy has become critical to technological advancement for the energetic transition from fossil fuels to clean and sustainable sources. Ocean Thermal Energy Conversion (OTEC) technology, which generates electricity by leveraging the temperature differential between surface and deep ocean waters, enables stable power generation around the clock. In this domain, the combination of thermoelectric generators (TEGs) and heat exchangers has exhibited immense potential for ameliorating the deficiencies of conventional OTEC. This study uses finite element numerical simulation of the COMSOL5.5 software to investigate the fluid dynamics characteristics of heat exchangers with flat fins and different types of longitudinal vortex generators (LVGs) under the same number of fins. This research encompasses heat exchangers with rectangular, triangular, and trapezoidal LVGs. Concurrently, the analysis examines how the vortices generated by the LVGs influence the thermoelectric performance of the TEGs. The results demonstrate that heat exchangers integrating flat fins and LVGs can enhance the power generation efficiency of TEGs. However, the pumping power required by the LVGs constrains the thermoelectric conversion efficiency. Compared to rectangular and triangular LVGs, trapezoidal LVGs achieve a superior balance between output and pumping power. Heat exchangers utilizing trapezoidal LVGs can attain the highest TEG thermoelectric conversion efficiency with a specific seawater flow velocity. Overall, these findings provide valuable reference information for applying TEGs and heat exchangers in OTEC design.

Modeling and thermodynamic optimization of a solar-driven two-stage multi-element thermoelectric generator

In this article, a finite-time thermodynamic model of solar-driven two-stage multi-element thermoelectric generator is developed. Considering external heat transfers, radiation loss of collector, Joule heat and Fourier heat leakage, analytical formulas for heat balance equations, power and efficiency are derived. Working temperatures of thermoelectric device are obtained by solving four equations simultaneously, and basic performance of the system is explored. Performance optimization is executed by adjusting electrical current, thermoelectric element distribution and heat exchanger inventory distribution. The optimal allocations for different total thermoelectric element numbers are given by the enumeration method. Influences of various factors on maximal power and efficiency are analyzed, and the upper bounds of power and efficiency are given. Results show that an optimal collector temperature exists to achieve optimal performance for this solar power device. Power and efficiency show the same variation trend, and the efficiency is maximal when power reaches its maximum. The system performance is optimal when external heat transfers and inner structure parameters are optimal. At this time, the corresponding junction temperatures reach their optimal values, the total thermal conductance should be divided in a half to two heat exchangers, and the corresponding thermoelectric element is allocated nearly half to upper generator.

Modelling and Simulation Study of a Segmented Converging Thermoelectric Heat Exchanger for Power Generation Efficiency Improvement

Modelling and Simulation Study of a Segmented Converging Thermoelectric Heat Exchanger for Power Generation Efficiency Improvement

Development and validation of thermal performances in a novel thermoelectric generator model for automotive waste heat recovery systems

Integrated thermoelectric generators (TEGs) and heat exchangers (HEX) can transform heat into electrical power by converting temperature gradients between heat sources and cold sinks. Predicting TEG thermal performances with compact HEX is crucial to designing efficient TEGs for automotive waste heat recovery. However, previous investigations mainly concentrated on TEG electrical performance, neglecting the thermal performances under high Reynolds numbers (Re) of exhaust gasses. This study utilizes the model-based development (MBD) method to develop a novel 1D TEG model, focusing heat transfer coefficient α and pressure drop ΔP inside a louvered corrugated fin HEX, component temperatures, and boundary heat flux, which affect electrical power from thermoelectric modules (TEM). The performance data are measured from 36 tests under different fin pitches Fp = 1.0 - 2.0 mm, Re = 4,000–14,000, and inlet gas conditions. Two methods are used to develop the model using user-defined functions (UDFs) for friction coefficient Cf and α, accounting for actual fin geometries. In Method 1, UDF multipliers for each Fp are required to calibrate the TEG model. In Method 2, simplified UDFs for Cf and α are implemented. Method 1 shows that the model is well-calibrated with maximum average relative errors δa< 6.7% but requires model fitting for each Fp. The fast-predictive TEG model with the novel calibration Method 2 can reproduce the thermal and electrical performances with δa< 20% without model tuning, which can be used for TEG redesign and integrated into vehicle-level MBD with a conventional and electrified powertrain, leveraging a fast driving-cycle simulation.

Novel thermoelectric generator heat exchanger for indirect heat recovery from molten CuCl in the thermochemical Cu–Cl cycle of hydrogen production

The looming threat of global warming has elicited efforts to develop reliable sustainable energy resources. Hydrogen as a clean fuel is deemed a potential solution to the problem of storage of power from renewable energy technologies. Among current thermochemical hydrogen generation methods, the thermochemical copper-chlorine (Cu–Cl) cycle is of high interest owing to lower temperature requirements. Present study investigates a novel heat exchanger comprising a thermoelectric generator (TEG) to recover heat from high temperature molten CuCl exiting the thermolysis reactor. Employing casting/extrusion method, the performance of the proposed heat exchanger is numerically examined using COMSOL Multiphysics. Results indicate that maximum generated power could exceed 40 W at the matching current of 4.5 A. Maximum energy conversion efficiency yields to 7.1%. Results demonstrate that TEG performance boosts with increasing the inlet Re number, particularly at the hot end. For the molten CuCl chamber, findings denote that there is a 36% discrepancy between highest and lowest Re numbers. Similarly, the highest efficiency value pertains to the case with the highest inlet velocity. Moreover, the highest temperature difference between inlet and outlet of the cooling water is about 28 °C and 10 °C for the lowest and highest inlet Re numbers, respectively. Average deviation from anticipated friction factor and Nusselt number are 0.31% and 12.62%, respectively.

Effect of thermoelectric modules with different characteristics on the performance of thermoelectric generators inserted in the central flow region with porous foam copper

The recovery and utilization of waste heat by thermoelectric power generation technology can effectively improve energy utilization efficiency and solve the problem of environmental pollution and resource shortage. In this study, a thermoelectric power generation system is established to recover and utilize high temperature waste heat for thermoelectric power generation. In order to improve the conversion efficiency of thermoelectric generator, porous foam copper is inserted into the central flow region of thermoelectric generator to enhance the heat transfer effect at the hot side, and the thermoelectric generator Comprehensive Performance (TEGCP) as a evaluation standard is used to analyze the performance of thermoelectric generator under the porous foam copper central flow region inserted method. The results show that the thermoelectric module with low thermal conductivity and high electrical conductivity can play a better performance in the thermoelectric generator. Moreover, the heat exchange capability of the thermoelectric generator heat exchanger can be significantly increased when the porous foam copper is inserted in the central flow region. Compared with an insert-free thermoelectric generator, the output power of the thermoelectric generator using porous foam copper with high pore density and high volume ratio is increased by 2.3 times. Through the TEGCP that, the use of 15 mm thickness (75 % volume ratio), 20PPI porous foam copper with the module KTGM161-18 and the central flow region inserted method has the best influence of the thermoelectric generator.

Impact of a thermoelectric subcooler heat exchanger on a carbon dioxide transcritical refrigeration facility

To improve the performance of vapour compression refrigeration cycles, the inclusion of a thermoelectric subcooler for low-medium power units has been the focus of recent studies due to its robustness, compactness and simplicity of operation. In thermoelectric systems, it has been demonstrated that the heat exchangers used in the hot and cold side of the thermoelectric modules have a critical impact in the performance of the system. This influence has not yet been studied for thermoelectric subcooling systems in vapour compression cycles. This work, for the first time, evaluates the impact that the heat exchangers of a thermoelectric subcooler, included in a transcritical carbon dioxide refrigeration cycle, have, in the performance of the refrigeration cycle. The influence is quantified in terms of: optimum working conditions, coefficient of performance and cooling capacity. The results show that, through an optimization of the heat exchangers of the thermoelectric subcooler, the performance improvements on the coefficient of performance using this technology are boosted from 11.96 to 14.75 % and the upgrade in the cooling capacity of the system rises from 21.4 to 26.3 %. Moreover, the optimum gas-cooler working pressure of the system is reduced and the optimum voltage supplied to the thermoelectric modules increases.

When power factor supersedes zT to determine power in a thermocouple

The primary material parameter determining power in a thermoelectric is the figure of merit zT. This figure of merit comes from the requirement for thermal impedance matching between the thermoelectric legs and heat exchangers in an optimally designed thermoelectric module. However, in a thermocouple temperature sensor, the geometry is constrained for temperature sensing. If the geometry is constrained so that the length of the thermoelectric elements is greater than a characteristic length, then the material thermal conductivity becomes less relevant. This makes the power factor the determining material metric for power output in such a device designed for temperature sensing.

Novel designs of thermoelectric generator for automotive waste heat recovery: A review

&lt;abstract&gt; &lt;p&gt;Many worldwide scientists have concentrated on using waste heat recovery technology in automotive applications because of increasingly strict fuel consumption. The thermoelectric generator (TEG) has garnered significant interest in the automobile sector as a viable waste heat recovery solution over the past several decades. A short survey of thermoelectric materials and heat exchangers for TEG systems is initially presented in this paper. To overcome the heat exchanger's current shortcomings, some previous studies designed a variety of the heat exchanger geometry of the TEG system. They suggested concentric cylindrical TEG system utilizes an annular thermoelectric module instead of the traditional square-shaped one. It uses the heat pipe's benefits to improve radial heat transmission. A comparison of the water-inside and gas-inside arrangements indicated that the water-inside concentric cylindrical TEG system provided a greater power output in our simulations to test the performance of the proposed system.&lt;/p&gt; &lt;/abstract&gt;

Heat Flux Based Optimization of Combined Heat and Power Thermoelectric Heat Exchanger

We analyzed the potential of thermoelectrics for electricity generation in a combined heat and power (CHP) waste heat recovery system. The state-of-the-art organic Rankine cycle CHP system provides hot water and space heating while electricity is also generated with an efficiency of up to 12% at the MW scale. Thermoelectrics, in contrast, will serve smaller and distributed systems. Considering the limited heat flux from the waste heat source, we investigated a counterflow heat exchanger with an integrated thermoelectric module for maximum power, high efficiency, or low cost. Irreversible thermal resistances connected to the thermoelectric legs determine the energy conversion performance. The exit temperatures of fluids through the heat exchanger are important for the system efficiency to match the applications. Based on the analytic model for the thermoelectric integrated subsystem, the design for maximum power output with a given heat flux requires thermoelectric legs 40–70% longer than the case of fixed temperature reservoir boundary conditions. With existing thermoelectric materials, 300–400 W/m2 electrical energy can be generated at a material cost of $3–4 per watt. The prospects of improvements in thermoelectric materials were also studied. While the combined system efficiency is nearly 100%, the balance between the hot and cold flow rates needs to be adjusted for the heat recovery applications.

Improving the Efficiency of the Liquid Heater in the Pre-Start Preparation of the Internal Combustion Engin

Introduction. In this article the study subject is the power supply system of the pre-start heater. The purpose of the study is to evaluate the possibility of using a thermoelectric generator to power the liquid preheater with optimization of the flow section of the thermoelectric generator heat exchanger. Materials and Methods. It is proposed to use a thermoelectric generator as an additional energy source to reduce electric power consumption by a pre-start heater. In the course of the study, various structures of the flow section of the thermoelectric generator heat exchanger have been modeled. The thermal and hydrodynamic analyses were carried out in the software environment ANSYS Workbench, Solidworks Flow Simulation to develop the most effective design for the flow section of the thermoelectric generator heat exchanger Results. An experimental installation was assembled and the dependence of the temperature modes of the pre-start heater on the output parameters of the thermoelectric generator was determined. Discussion and Conclusion. It has been proved the possibility of reducing the power consumption of the vehicle battery during thermal preparation of the internal combustion engine by using a thermoelectric generator adapted to the power supply system of the liquid pre-start heater.

Experimental analysis of thermoelectric heat exchanger powered by solar energy

Experiments were performed to test a novel solar photovoltaic (PV) powered Thermoelectric Heat Exchanger (TE-HE) to provide hot/cold water. The experiments were carried out for 3 configurations- cold reservoir charging, hot reservoir charging and single pass test. In the charging experiments, the water was recirculated in either the hot or cold reservoir to obtain heated or cooled water. In single pass test, water was circulated as a free stream to obtain cold/ hot output. The device was powered by solar PV, making it portable and able to work in remote places. The Coefficient of Performance (COP) of the device was calculated. The effect of changing the volume flow rates on the hot and cold sides of the Thermoelectric Modules (TEM) was studied. The change in COP of the cooler/ heater with the change in number of TEMs was also assessed. It was observed that the COP in the cold reservoir charging phase increased with the increase in water flow rates through the hot and cold water jackets. A maximum COP of the cold water charging mode of 1.33 was obtained for hot side flow rate of 150 L/h and cold side flow rate of 75 L/h. The performance of the thermoelectric (TE) device in cooling configuration was influenced positively by varying the size of the hot reservoir. The highest COP obtained for the heating configuration was 1.73 at the maximum water flow rates. Increasing the number of TEMs increased the performance of the heater. The minimum and maximum outlet temperatures in the single pass test were 10 °C and 49 °C respectively. The COPmax value for the cooling configuration was 0.71, and 0.92 for the heating configuration.

Multiphysics CFD Simulation for Design and Analysis of Thermoelectric Power Generation

The multiphysics simulation methodology presented in this paper permits extension of computational fluid dynamics (CFD) simulations to account for electric power generation and its effect on the energy transport, the Seebeck voltage, the electrical currents in thermoelectric systems. The energy transport through Fourier, Peltier, Thomson and Joule mechanisms as a function of temperature and electrical current, and the electrical connection between thermoelectric modules, is modeled using subgrid CFD models which make the approach computational efficient and generic. This also provides a solution to the scale separation problem that arise in CFD analysis of thermoelectric heat exchangers and allows the thermoelectric models to be fully coupled with the energy transport in the CFD analysis. Model validation includes measurement of the relevant fluid dynamic properties (pressure and temperature distribution) and electric properties (current and voltage) for a turbulent flow inside a thermoelectric heat exchanger designed for automotive applications. Predictions of pressure and temperature drop in the system are accurate and the error in predicted current and voltage is less than 1.5% at all exhaust gas flow rates and temperatures studied which is considered very good. Simulation results confirm high computational efficiency and stable simulations with low increase in computational time compared to standard CFD heat-transfer simulations. Analysis of the results also reveals that even at the lowest heat transfer rate studied it is required to use a full two way coupling in the energy transport to accurately predict the electric power generation.

THERMOELECTRIC HEAT EXCHANGER - HEAT TRANSMISSION INTENSIFIER FOR MAINTAINING A THERMAL REGIME IN ELECTRONIC SYSTEMS

Abstract. Aim. The article presents a thermoelectric heat exchanger / heat transfer intensifier design for ensuring the thermal regime of electronic equipment located in external installations.Method. Methods for modelling heat exchange processes were applied.Result. A thermoelectric system is proposed, consisting of a heat exchanger / heat transfer intensifier component located in an external installation. In structural terms, the external installation comprises a compartment disposing electronic heatgenerating components, in which are located channels for ventilating external air, while a second compartment contains elements that require to be sealed from external influences, in cluding contact with external cooling air. A mathematical model is provided for determining the temperature of air flows from the heatexchange surfaces of a thermoelectric system (TES), as well as the limiting length of a thermoelectric system to achieve equal output temperature at given supply currents of thermoelectric batteries.Conclusion. On the basis of the conducted studies, it is concluded that a longer thermoelectric system for ensuring the intensification mode corresponds to an increased difference in the temperature of the coolant at the inlet. The temperature of the air flow at the outlet becomes lower with a further increase in length due to the thermoelectric heat exchanger entering the operating mode of the thermoelectric refrigeration unit.

STUDY OF A FLOWING-TYPE HEAT TRANSFER INTENSIFIER USED AS PART OF A THERMOELECTRIC SEA WATER DESALINATION SYSTEM

Objectives To analyse the thermophysical processes in the thermoelectric heat transfer intensifier operating as part of a desalination system based on semiconductor thermoelectric converters.Method A mathematical model for the design of a desalter containing a thermoelectric heat exchanger, which provides for the use of heat flows by natural thermal conductivity due to so-called heat channels, is proposed. The proposed method of using additional heat sinks on the heat-absorbing side of the device and additional heat sources on the fuel side determines the need for a new mathematical model that differs from the known mathematical models describing heat transfer in the heat transfer flowing-type intensifier.Results The analysis of modelling results shows that a significant contribution to the temperature field of heat conductors is made when considering the heat transfer over the heat channels. The value of the contribution is the greater, the higher the thermal conductivity of the heat channels and the temperature difference between the heat conductors and the surface of the heat channels. In accordance with their purpose, flow-type thermoelectric heat transfer intensifiers (THTIs) for desalination applications must ensure efficient heat transfer from the cooled fluid flow to the heated fluid flow. The results show that, at a given limited length of the heat exchanger, the use of a thermoelectric battery together with heat channels allows equality of temperatures of heat conductors at the output to be achieved.Conclusion The modelling results show that, under the operating conditions of the thermal battery in intensifier mode, the length of the heat exchanger shall not exceed the value, at which the temperature of the heat conductor at the outlet becomes equal. The system solution provides the required length of the thermal battery, which allows equality of coolant temperatures to be achieved at the exit from the THTI operation mode. Following the logic of the desalter scheme under consideration, it is obvious that the reduction in the length of the heat exchanger, with all other things being equal, gives a reduction in the mass and size of the device as a whole.

Thermoelectric generation for waste heat recovery: Application of a system level design optimization approach via Taguchi method

Thermoelectric generator is a solid-state energy converter which can convert waste heat directly into electricity. During the past decades, thermoelectric materials have been widely investigated whereas the integrated design of thermoelectric generators have been less studied. This paper proposes and implements a framework for the design of thermoelectric generators, consisting of thermoelectric modules and heat exchangers, based on the Taguchi method. As compared with previous researches which optimize the thermoelectric module alone and assume fixed temperature or fixed heat fluxes for the thermoelectric modules, this work proposes a methodology to optimize the thermoelectric module and the heat exchanger together. Five design parameters (namely the height, the fill-ratio, the ratio of cross-sectional area of n-type material over p-type material of thermoelectric module, the length and the material of the heat exchanger) were analyzed for two different applications, waste heat recovery from marine and automotive engines. In order to perform the analysis, a L27 (35) orthogonal array was employed to assess all of the design parameters returning the maximum output power. By analysis of variance, it is found that the thermoelectric module height is the most important design parameter contributing for the 69.6% and 30.25% in automotive and marine application, respectively. And the optimal design parameter set are also determined in both applications.

Thermoelectric heat exchange and growth regulation in a continuous yeast culture.

We have designed a thermoelectric heat exchanger (TEHE) for microbial fermentations that is able to produce electric power from a microbial continuous culture using the intrinsic heat generated by microbial growth. While the TEHE was connected, the system proved able to stably self‐maintain both the temperature and the optical density of the culture. This paves the way toward a more sustainable operation of microbial fermentations, in which energy could be saved by converting part of the metabolic heat into usable electric power.

A Novel Design of Thermoelectric Generator for Automotive Waste Heat Recovery

With progressively stringent fuel consumption regulations, many researchers and engineers are focusing on the employment of waste heat recovery technologies for automotive applications. Regarded as a promising method of waste heat recovery, the thermoelectric generator (TEG) has been given increasing attention over the whole automotive industry for the last decade. In this study, we first give a brief review of improvements in thermoelectric materials and heat exchangers for TEG systems. We then present a novel design for a concentric cylindrical TEG system that addresses the existing weaknesses of the heat exchanger. In place of the typical square-shaped thermoelectric module, our proposed concentric cylindrical TEG system uses an annular thermoelectric module and employs the advantages of the heat pipe to enhance the heat transfer in the radial direction. The simulations we carried out to verify the performance of the proposed system showed better power output among the existing TEG system, and a comparison of water-inside and gas-inside arrangements showed that the water-inside concentric cylindrical TEG system produced a higher power output.

Theoretical investigation of a novel thermoelectric laundry dryer concept

The environmental impact of conventional heat pump dryers lies, apart from its energy consumption, in the use of a noxious refrigerant. By utilizing a thermoelectric heat pump laundry dryer, a refrigerant-free heat pump process is realized making especially the disposal of a laundry dryer more convenient. Moreover, the drying process is more efficient compared to a conventional condensation dryer as both the hot and cold side of the thermoelectric heat exchanger are used in the process.A novel cycle is introduced that combines thermoelectric heat pumping and air cooling by means of ambient air. This cycle is compared theoretically to two conventional cycles of a heat pump dryer and a condensation dryer. Moreover, a comprehensive system model is developed to evaluate the performance of such a dryer. Within the fully transient model temperature dependent material properties and contact resistances are considered. The performance of the thermoelectric heat exchanger is analyzed and significant variables are identified. Simulation results are compared with validated simulation results of a condensation and heat pump dryer. It is shown that the energy consumption of a thermoelectric heat-pump based tumble dryer lies between the two conventional dryers and thus can be seen as a promising technology.