Hot-side Heat Exchanger Research Articles

Evaluation method for assessing heat transfer enhancement effect on performance improvement of thermoelectric generator systems

The total power output of a thermoelectric generator system can be increased by enhancing the heat transfer performance of its hot-side heat exchanger. However, heat transfer enhancement is usually accompanied by the consumption of additional pump power. Therefore, it is unclear whether the net power output, that is, the difference between the total power output and the pump power, increases. Developing a comprehensive evaluation method based on the net power output is necessary to determine the heat transfer enhancement effect on performance improvement of the system. In this paper, the concept of net power ratio which integrates the total power output and the pump power consumption was proposed to evaluate the heat transfer enhancement effect on the performance improvement of a thermoelectric generator system. Based on a ring-shaped thermoelectric generator, the analytical solution of the net power ratio was theoretically derived. Compared with the numerical and experimental methods, the proposed net power ratio in a thermoelectric generator system is convenient and time-saving with adequate accuracy for engineering applications. Moreover, the application of net power ratio in a real thermoelectric generator system was investigated by case studies. Results show that both the inlet fluid temperature and the mass flow rate affect the net power ratio. When using net power ratio to evaluate the performance improvement of a thermoelectric generator system, net power should also be considered to obtain optimal working conditions for a thermoelectric generator system.

Prospects of waste-heat recovery from a real industry using thermoelectric generators: Economic and power output analysis

One of the options to reduce industrial energy costs and the environmental impact is to recover the waste-heat produce in some processes. This paper proposes the use of thermoelectric generators at a stone wool manufacturing plant to transform waste-heat from a hot gas flow into useful electricity. A combination of two computational models, previously developed and validated, has been used to perform the optimization from a double point of view: power output and economic cost. The proposed thermoelectric generator includes fin dissipaters and biphasic thermosyphons as the hot and cold side heat exchangers respectively. The model takes into account the temperature drop along the duct where the gases flow, the electric consumption of the auxiliary equipment, and the configuration and geometry of the heat exchangers. After the simulations a maximum net power production of 45 838 W is achieved considering an occupancy ratio of 0.40 and a fin spacing of 10 mm. The installation cost is minimized to 10.6 €/W with an occupancy ratio of 0.24. Besides, the Levelised Cost of Electricity, LCOE, is estimated for a thermoelectric generator for the first time. It is necessary to use standar methodologies to compare this technology to others. The LCOE estimated for the proposed design is around 15 c€/kWh within the ranges of current energy sources, proving, in this way, the capabilities of waste-heat recovery from industrial processes at reasonable prices with thermoelectric generators.

New opportunities for electricity generation in shallow hot dry rock fields: A study of thermoelectric generators with different heat exchangers

Despite being one of the largest renewable sources, geothermal energy is not widely utilized for electricity generation. In order to leverage shallow hot dry rock (HDR) fields, the present paper proposes an alternative to enhanced geothermal systems (EGS): thermoelectric generators. Based on the conditions of Timanfaya National Park, a prototype has been built to experimentally analyze the feasibility of the proposed solution. The prototype is composed by a two phase closed thermosyphon (TPCT) as hot side heat exchanger, two thermoelectric modules, and it considers different cold side heat exchangers: fin dissipators assisted by a fan and loop thermosyphons, both with various geometries. Experiments have demonstrated that loop thermosyphons represent the best alternative due to their low thermal resistance and, especially, due to their lack of auxiliary consumption, leading to a maximum net power generation of 3.29 W per module with a temperature difference of 180 °C (200 °C in the hot side and 20 °C as ambient temperature), 54% more than with fin dissipators. Hence, there exists a new opportunity for electricity generation in shallow hot dry rock fields: thermoelectric generators with biphasic thermosyphons as heat exchangers, a patented and robust solution.

Numerical study on nonuniform segmented enhancement method for thermoelectric power generator

Thermoelectric power generators (TEGs) have received considerable attention in the vehicular waste heat recovery. Large temperature difference between hot-side end and cold-side end of TE modules should be maintained to keep large power generation. However, the scaling-up problem of inevitably temperature drop of exhaust gas along the flow direction of vehicles is introduced when multiple TE modules are assembled. In this work, a three-dimensional fluid–thermal–electric multiphysics model with equivalent properties of TE modules is established. The influencing mechanism of longitudinal vortex generator (LVG) pair number and distribution in the hot-side heat exchanger on the local power generation performance of the TEGs is examined. It is found that the extent of the local power generation enhancement gets smaller or even deteriorates at the downstream TE modules by uniformly increasing the LVG pair number along the flow direction. Hence, to make the heat flux efficiently utilized, a nonuniform segmented enhancement method is used for the hot-side heat exchanger. The results show that compared with the TEG with a uniform heat exchanger or a downstream-denser heat exchanger, the total Seebeck voltage generated by the TEG with an upstream-denser heat exchanger is 28% higher, and its output power is 64.4% higher at the matched load resistance. The TEG with the upstream-denser heat exchanger significantly improves the overall power generation performance without additional pumping power.

Design and development of a test rig for the performance evaluation of automotive exhaust thermoelectric generator

In an automotive engine, around 40% of the heat produced by fuel combustion is wasted through exhaust gas. Conversion of part of this heat into electricity by a thermoelectric generator has the potential to improve the vehicle fuel efficiency. Developing an automotive exhaust thermoelectric generator (AETEG) for such conversion involves many challenges. The performance evaluation of the generator at the system level is one among them. The present work describes the design and development of a test rig for the evaluation of various characteristics of an AETEG. The test rig simulates the typical thermo-physical conditions of the engine of a light-duty vehicle using hot air. The temperature and the mass flow rate of the hot air entering the AETEG can be varied independently. The instruments provided in the system can measure the pressure drop, voltage-current and power-current characteristics of the AETEG under various inlet hot air conditions. An AETEG designed and assembled containing 40 modules each of 5 W capacity is tested for its performance in this test rig. Under the highest inlet temperature of 385°C and mass flow rate of 255 kg/h tested, the AETEG showed less than 1 kPa pressure drop with maximum open circuit voltage of 157 V and power of 27 W. The test rig could successfully map the temperature non-uniformity in the hot side heat exchanger and its effect on power output from each module. The overall efficiency of AETEG is only 0.4% mainly due to poor efficiency of the hot side heat exchanger.

동력 발생 최대화를 위한 열전모듈의 최적화

The objective of this study was to perform a theoretical investigation to optimize thermoelectric modules for maximization of power output using a novel one-dimensional analytic model, in which the thermal conductance of heat exchangers as well as the thermal and electrical contact resistances inherent in the modules are taken into account. It was established that there exist an optimum thermoelement length and an optimum external load resistance that maximize the power output when the heat source temperature, heat sink temperature and the thermal conductance of the available hot and cold side heat exchangers are given. The effects of the heat exchangers’ thermal conductance and the heat source temperature on the attainable maximum power, efficiency, the optimum thermoelement length and external load resistance were determined.

Numerical study and optimization of thermoelectric-hydraulic performance of a novel thermoelectric generator integrated recuperator

Abstract Thermoelectric modules are usually sandwiched between hot-side and cold-side heat exchangers to generate electrical power. But the sandwiched structures are unsuitable for recuperators because large thermal resistance caused by the thermoelectric modules significantly reduces the heat transfer efficiency. In order to maintain heat transfer efficiency and generate more electrical power, a novel concept of a thermoelectric generator integrated recuperator is proposed, with fins made of thermoelectric materials rather than steel. A numerical model is developed using FLUENT software with User Defined Function codes. Compared with conventional plate-fin recuperators, the new recuperator has similar thermal-hydraulic performance and generates additional electrical power. The effects of Reynolds number on open circuit voltage, internal resistance, heat transfer, output power, and pumping power are studied. The optimum hot gas velocity is 1.5 m/s, which produces a temperature difference of 147.6 K, an open circuit voltage of 31.5 mV, and an output power of 0.23 mW. The Taguchi method is employed to design numerical cases for geometrical optimization. Results show that the effect order is: channel width > TE fin thickness > TE fin height. The optimum values of channel width, fin thickness, and height are 1 mm, 3 mm, and 1 mm, respectively.

A comparative performance evaluation of the reversed Brayton cycle operated heat pump based on thermo-ecological criteria through many and multi objective approaches

Thermodynamic and ecological performance evaluation of the reversed Brayton cycle operated heat pump is analyzed in this work. Performance assessment of the heat pump is carried out through many-objective as well as multi-objective optimization. Maximization of coefficient of performance, ecological coefficient of performance, exergy efficiency and ecological function of the heat pump are considered simultaneously during many-objective optimization. Four operating variable of the heat pump which include temperature ratio, compressor pressure ratio, hot side and cold side heat exchanger effectiveness are investigated in the optimization study. The conflicting level between thermo-ecological behaviour of heat pump is explored through comparison between multi-objective (i.e. two-objective) and many-objective (i.e. four-objective) optimization results. Both, multi-objective and many-objective optimization problem of heat pump are solved using the heat transfer search algorithm and results are presented in the form of Pareto-optimal points. Further, the effect of the design variables and its sensitivity to thermo-ecological behaviour of the heat pump are also presented. Comparative results reveal that, 16.16–37.93% variation in the thermo-ecological behaviour of the heat pump is observed during many-objective optimization as compared to multi-objective optimization. Different decision making approaches are used to select a final optimal solution from Pareto optimal set of many-objective optimization. Finally, the optimization results are compared with the experimental results of the heat pump system. The comparative results revels that 10.95% deviation in co-efficient of performance and 12.3% deviation in exergy efficiency are observed between optimization and experimental results.

New Paradigms in Defining Optimum Cost Conditions in Thermoelectric Energy Recovery Designs

Cost is just as important as power density or efficiency for the adoption of waste heat recovery (WHR) thermoelectric generators (TEG). Prior work [1] has shown that the system design that minimizes cost (e.g., the G [$/W] value) can be close to the designs that maximize power, but these design regimes are not necessarily aligned with high system conversion efficiency or power density. Recent work [2–5] further explores the impact of heat exchanger conditions on the optimum TEG fill factors and cost scaling of a waste heat recovery thermoelectric generator with a detailed treatment of the hot side exhaust heat exchanger. The cost scaling analysis considers the overall TEG system costs, including TE material costs, manufacturing costs, and specifically heat exchanger costs; and the performance analysis accounts for heat lost to the environment and updated relationships between the optimum hot-side and cold-side conductances that maximize power output. The optimum fill factor, Fopt, to minimize TEG energy recovery system costs is strongly dependent on the heat leakage fraction, σ, the mass flow rate of the exhaust, the hot-side heat exchanger effectiveness, heat exchanger UAu, and interfacial heat flux [1]. A more rigorous analysis and conclusion for the optimum fill factor was recently introduced and characterized at the 14th European Conference on Thermoelectrics [5] in 2016. A new, more comprehensive relationship for Fopt has created an updated, more rigorous relationship for the optimum cost, Gopt, relationship for thermoelectric energy recovery systems. These new [Gopt, Fopt] relationships are explored and characterized to show the inherent design complexities. The heat exchanger costs can often dominate the TEG cost equation and it is critical to fully understand the tradeoff between heat exchanger performance, TEG manufacturing and material costs, optimum TEG fill factors, and TE performance to establish potentially optimum design points within the cost-performance design space. This work explores and characterizes new design tradeoffs and new cost minimization relationships within this cost-performance design space for a typical thermoelectric energy recovery system application where the interplay between optimum TEG fill factors, TE device design parameters, and heat exchanger design parameters can impact system footprint, volume, and mass in weight-sensitive applications. This work shows how heat exchanger UAu, interfacial heat flux, and Fopt govern cost minimization and create and control cost regimes within the overall cost-performance design domain. This shift of emphasis acknowledging the interdependence of optimum TE fill factors, heat exchanger performance, and interfacial heat flux has significant implications on thermoelectric WHR system designs, their performance, and their operation.

Parametric study of thermoelectric power generators under large temperature difference conditions

To help study the performance of thermoelectric power generators in conditions where there are large temperature differences between the hot-side heat exchanger and the cold-side heat exchanger, this paper presents a simplified numerical model that includes temperature-dependent properties of thermoelectric materials. Specifically, the temperature difference is added into the calculations of the current across thermoelectric legs. The results indicate that the simplified numerical model could reduce calculation time without reducing calculation accuracy. The variable physical properties of thermoelectric materials should be considered in the counter-flow arrangement at high temperature, but they can be neglected in the co-flow arrangement. The inlet temperature of hot fluid and the variable physical properties of thermoelectric materials have a coupling influence on the performance of thermoelectric power generation, which could change the variation trend of output power. The performance of thermoelectric power generation for the counter-flow arrangement is better than that for the co-flow arrangement, especially with high heat transfer coefficients and long channel lengths. When the the various physical properties of thermoelectric materials are considered, the maximum output power and efficiency occur at ratios of load resistance to internal resistance of about 1.5–1.8 for output power and 1.7–2 for efficiency.

Multi-objective optimization in a finite time thermodynamic method for dish-Stirling by branch and bound method and MOPSO algorithm

There are various analyses for a solar system with the dish Stirling technology. One of those analyses is the finite time thermodynamic analysis. By the finite time thermodynamic analysis, the total power of system can be obtained by calculating the process time. In this study, the convection and radiation heat transfer losses from collector surface, the conduction heat transfer between hot and cold cylinders and cold side heat exchanger have been considered. During this investigation, the four objective functions have been optimized simultaneously. These objective functions are included of the power, efficiency, entropy and economic factors. In addition to the four-objective optimization, three-objective, two-objective and single-objective optimizations have been done on the dish-Stirling model. In this study, the algorithm of MOPSO with post-expression of preferences is used for multi-objective optimizations while the Branch and Bound algorithm with Pre-expression of preferences is used for single-objective and multi-objective optimizations. In case of multi-objective optimizations with post-expression of preferences, Pareto optimal front are obtained, afterward by implementing the Fuzzy, LINMAP and TOPSIS decision making algorithms, the single optimum results can be achieved. At the end, the comparison of the results shows the benefits of MOPSO in optimizing dish Stirling finite time thermodynamic equations.

Thermodynamic analysis and multi-objective optimisation of endoreversible Lenoir heat engine cycle based on the thermo-economic performance criterion

ABSTRACTA thermodynamic model of a steady-flow endoreversible Lenoir heat engine cycle (a ‘three-point’ cycle) coupled with constant-temperature heat reservoirs is established in this paper by using finite-time thermodynamic theory. The cycle consists of one isochoric heating branch, one adiabatic expansion branch and one isobaric cooling branch. A mathematical approach based on the finite-time thermodynamic is proposed to obtain thermal efficiency, the output power and the entropy generation rate throughout the Lenoir system. In this study, an irreversible Lenoir engine is analysed thermodynamically in order to optimise its performance. In this regard, the optimal values of the ecological coefficient of performance and dimensionless thermo-economic objective functions of the Lenoir heat engine are determined. Multi-objective evolutionary algorithms based on Non-dominated Sorting Genetic Algorithm II algorithm is applied to the aforementioned system for calculating the optimal values of decision variables. Decision variables considered in this paper include the ratio of fluid temperature (), the effectiveness of the cold-side heat exchanger, the effectiveness of the hot-side heat exchanger, the temperature of state 1 and relative investment cost parameter of the hot-side heat exchanger. Moreover, Pareto optimal frontier is applied and an ultimate optimal answer is chosen via three competent decision-making approaches comprising Linear Programming Technique for Multidimensional Analysis of Preference, fuzzy Bellman-Zadeh and Technique for Order of Preference by Similarity to Ideal Solution.

Heat Exchanger Performance Impacts on Optimum Cost Conditions in Thermoelectric Energy Recovery Designs

Cost is just as important as power density or efficiency for the adoption of waste heat recovery thermoelectric generators (TEG). Prior work [1] has shown that the system design that minimizes cost (e.g., the $/W value) can be close to the designs that maximize the system’s efficiency or power density, however, it is important to understand the relationship between those designs to optimize TEG performance-cost compromises. Expanding on recent work [1, 2, 3] the impact of heat exchanger conditions on the optimum TEG fill factors and cost scaling of a waste heat recovery thermoelectric generator with a detailed treatment of the hot side exhaust heat exchanger has been investigated further. The effect of the heat lost to the environment and updated relationships between the hot-side and cold-side conductances [4] that maximize power output are considered. The optimum fill factor to minimize TEG energy recovery system costs is strongly dependent on the heat leakage fraction, σ, the mass flow rate of the exhaust, the hot-side heat exchanger effectiveness, heat exchanger UAh, and heat flux. These relationships are explored and characterized for typical exhaust gas-flow conditions to show the inherent design complexities. The heat exchanger costs often dominate the TEG cost equation and it is critical to fully understand the tradeoff between heat exchanger performance, optimum TEG fill factors, and cost to establish potentially optimum design points within the cost-performance design space. This work will explore the design tradeoffs and relationships within the cost-efficiency-power density design space for a typical thermoelectric energy recovery system application. The interplay between optimum TEG fill factors and heat exchanger design can impact system footprint, volume, and mass in weight-sensitive applications. Less-effective, low-cost heat exchangers may outperform higher cost alternatives from a market adoption perspective. This shift of emphasis acknowledging the interdependence of optimum TEG fill factors and heat exchanger performance has significant implications on thermoelectric waste heat recovery systems designs and their operation. In addition, preferred TEG design regimes exist that accommodate reasonable compromises in TE performance and cost. This effort highlights how the optimum fill factor–heat exchanger performance relations couple to these optimum TEG performance-cost domains based on TEG-system-level analyses and provides a focus for future system research and development efforts.

Analysis of the fins geometry of a hot-side heat exchanger on the performance parameters of a thermoelectric generation system

This paper presents the influence of hot-side heat exchanger (HHX) design on the operational parameters of a thermoelectric generator (TEG). The approach is comprehensive, power needs due to pressure losses in the device are accounted for the analysis. The TEG used in the installation always requires additional power to overcome pressure drops. This directly influences the net generated power of the device – which is the main benefit of using a TEG – and should always be taken into account in TEG analyses. The study shows that the power expenditure of the flow arrangement providing the most uniform temperature can be higher than the potential benefit, so the temperature distribution on the HHX casing may not be the only determinant of its quality. Only a detailed analysis of all crucial parameters for the operating conditions of a TEG can provide guidelines for selecting an HHX geometry for specific uses. Among the cases analyzed, the non-uniform temperature distribution generated by an HHX with equal fins provides the highest net generated power.

Experimental investigation on thermoelectric generator with non-uniform hot-side heat exchanger for waste heat recovery

In typical gas-to-liquid thermoelectric generators for waste heat recovery, the stream-wise gas temperature drop in the hot-side heat exchanger leads to the decrease of power output of the whole system. Denser fins are usually arranged on the downstream of the hot-side heat exchanger to improve the uniformity of temperature field and thus the total power output performance of thermoelectric generators when the steam-wise temperature drop is small, but it is not benificial when the steam-wise temperature drop is large. This work investigates the effect of configuration of winglet vortex generators on the performance of thermoelectric generator system. Three sets of hot-side heat exchangers, including a heat exchanger with smooth channel, a heat exchanger with uniform configuration of winglet vortex generators and a heat exchanger with non-uniform configuration of winglet vortex generators, are tested in a gas-to-liquid thermoelectric generators experimental system. The hot-side Reynolds number ranges from 3000 to 6400 and the hot-side inlet temperature is within 523–553K. The experimental results show that the total and net power output of thermoelectric generator under matched load resistance with uniform heat exchanger can respectively outperform that with smooth heat exchanger by 97.5% and 77.7% in average, whereas that with non-uniform heat exchanger by 189.1% and 177.4% in average. Since the uniform and non-uniform heat exchangers have the same number but different configuration of winglet vortex generators, this kind of active cascade control of heat transfer enhancement elements is proved to be effective in improving the power output of thermoelectric generator system without increasing pumping power.

Simulation-driven design of a passive liquid cooling system for a thermoelectric generator

Active cooling of thermoelectric generators (TEGs) is problematic since mechanical devices such as pumps and fans draw a high proportion of the limited power generated. Increasing the coolant fluid flow rate is typically a scenario of diminishing gains since the increased TEG power can be more than offset by the increase in power required for the fluid mover. Passive air cooling is an option, however the high air-side thermal resistance results in poor TEG power performance and low thermal efficiency. To address these issues, and others, a passive single phase liquid thermosyphon cooling system for use with TEGs has been designed, computationally simulated and experimentally tested. The novelty of the cooling system centres not only on the hot-side heat exchanger design, but also on the use of an open liquid reservoir as a dual-purposed heat store and air-side heat sink. This results in an effective source-to-sink heat exchange system that is entirely passive while providing effective cooling. This work describes the Simulation-Driven Design approach used to design the system for an example of a single TEG, experimental verification of the simulation results and TEG performance characteristics with the new cooling system.

Performance parameters and numerical model of thermoelectric generator dedicated for energy harvesting from flue gases

The paper presents results of preliminary studies of thermoelectric generator (TEG) dedicated for waste heat harvesting from flue gases. Investigation includes numerical analysis for estimating power losses due to pressure drop in the installation with the TEG and experimental tests for obtaining electrical parameters and operation conditions, such as casing temperatures and the temperature difference between the inlet and the outlet. Proposed prototype has been equipped with the pin fins for increase the heat transfer. Results indicates that power losses are negligible in comparison with generated electrical power. The heat exchanger's interior demands to be modified to enhance the efficiency by increasing temperatures on the external surfaces of the hot-side heat exchanger (HHX). Further research will focus on numerical analysis of the influence of geometry modifications on the thermal and flow parameters of the TEG resulting in the increase of generated power and efficiency.

Geometric optimization of thermoelectric elements for maximum efficiency and power output

The geometry of n- and p-type thermoelectric elements (TE) in terms of the cross-sectional area and length were optimized to yield either maximum thermal conversion efficiency ηth,max or maximum power output Po,max. The optimization process incorporated temperature-dependent material properties and independent thermal and electrical contact resistances that are a function of the contact area per TE leg. Additionally, ηth,max and Po,max were quantified by simultaneously optimizing the TE geometry and varying the hot-side fluid temperature, cold- and hot-side heat exchanger effective area and heat transfer coefficients using a complete one-dimensional thermal resistance network model. Optimized compared to non-optimized geometries, excluding contact resistances, achieve a maximum 10.4% increase in Po,max and 3.2% increase in ηth,max for conditions studied. Optimized compared to non-optimized geometries, taking into account independent thermal and electrical contact resistances, exhibit a 29% increase in volumetric power density and 12% increase in volumetric efficiency in comparison to non-optimized cases.

Thermodynamic multi-objective optimization of a solar-dish Brayton system based on maximum power output, thermal efficiency and ecological performance

Solar-dish Brayton system driven by the hybrid of fossil fuel and solar energy is characterized by continuously stable operation, simplified hybridization, low system costs and high thermal efficiency. In order to enable the system to operate with its highest capabilities, a thermodynamic multi-objective optimization was performed in this study based on maximum power output, thermal efficiency and ecological performance. A thermodynamic model was developed to obtain the dimensionless power output, thermal efficiency and ecological performance, in which the imperfect performance of parabolic dish solar collector, the external irreversibility of Brayton heat engine and the conductive thermal bridging loss were considered. The combination of NSGA-II algorithm and decision makings was used to realize multi-objective optimization, where the temperatures of absorber, cooling water and working fluid, the effectiveness of hot-side heat exchanger, cold-side heat exchanger and regenerator were considered as optimization variables. Using the decision makings of Shannon Entropy, LINMAP and TOPSIS, the final optimal solutions were chosen from the Pareto frontier obtained by NSGA-II. By comparing the deviation index of each final optimal solution from the ideal solution, it is shown that the multi-objective optimization can lead to a more desirable design compared to the single-objective optimizations, and the final optimal solution selected by TOPSIS decision making presents superior performance. Moreover, the fitted curve between the optimal power output, thermal efficiency and ecological performance derived from Pareto frontier is obtained for better insight into the optimal design of the system. The sensitivity analysis shows that the optimal system performance is strongly dependent on the temperatures of absorber, cooling water and working fluid, and the effectiveness of regenerator. The results of this work offer benefits for related theoretic research and basis for solar energy industry.

The Analysis of Heat Exchangers Geometry in Thermoelectric Generators for Waste Heat Utilization

The paper presents results of the analysis and comparison of the hot-side heat exchangers (HHXs) dedicated for the thermoelectric generators (TEGs). Efficient operation of TEG depends on, i.a. proper design of the HHX. Six geometries of the heat exchangers’ cross-section have been investigated and analysed in view of heat transfer effectiveness (ηTH) and pressure drop (ΔP). As an assumption, useful heat exchange surface has been set up as 2400 cm2 , maintaining heat exchanger (HX) length as 30 cm, which is enough for the placement of the 32 thermoelectric modules able to generate at least 160 W of the electrical power. The source of waste heat are flue gases, in the analysis approximate as an air. Cold-side heat exchanger (CHX) has been simplified and calculated as a water flow around the casing of the HHX to achieve comparable results. As a base, circular profile has been presented. Numerical calculations provide results suggesting which shape is most suitable for specified application. Results could be the first guidelines for selecting and designing the HX for the TEG. Further investigation will focus on optimization of the chosen HX in view of increasing ηTH and minimizing ΔP.