Heat Recovery Research Articles

Assessment of the impact of intensification of heat exchange processes in heaters on power unit efficiency

In various spheres of modern industry, including power engineering, the issue of low efficiency of operation of heatexchange equipment, where condensation of vapour-gas media occurs, is a significant concern. It is known that one of the effective ways of solving this problem is intensification of heat exchange processes by transitioning from the traditional film condensation mode to the droplet condensation mode. A promising and technically straightforward way to achieve the droplet mode of condensation is a method based on the treatment of heat-exchange surfaces using a surfactant – octadecylamine (ODA). The analysis of studies, in which results of experimental research and industrial implementation are given, has shown that application of the specified method in conditions of condensation of water steam promotes formation of a stable droplet mode of condensation; as a result, the heat transfer coefficient on the steam side can more than double.Equally important and interesting is the question of how the efficiency of heat exchangers impacts the overall efficiency of complex systems, in which they operate. In this study, we examined the effect of the operational efficiency of network and regenerative heaters on the energy efficiency and economic performance of a power unit based on steam turbine unit T-110-12,8-3 operating in the heat recovery mode. To this end, we calculated the thermal scheme under various operating conditions of these heat exchangers and determined several key efficiency indicators, including the fuel heat utilisation factor (HUF) and electrical efficiency (EE). It is revealed that intensification of heat-exchange processes by a factor of 2 in horizontal delivery water heaters (HDWH) or in low-pressure heaters (LPH) significantly enhances the efficiency indicators of the power unit as a whole. At the same time, as the analysis of calculation results showed, the greatest benefits are realized when this measure is implemented in HDWH.

PbSe Thermoelectrics: Efficient Candidates for Power Generation and Cooling

AbstractThermoelectric materials enable efficient and clean conversion between heat and electricity, offering significant application prospects in waste heat recovery and solid‐state cooling. Lead selenide (PbSe) is a more abundant and cost‐effective alternative to PbTe with promising potential for mid‐temperature applications. However, things have changed very recently with the discovery of the traditional power generator PbSe being rather competitive as a thermoelectric cooler, opening new avenues for investigating this compound. This review aims to comb how the research achievements and promising performance of PbSe have shifted from medium to near‐room temperatures, by comprehensively discussing various strategies to enhance the thermoelectric efficiency at different temperature ranges. Subsequently, it is reviewed how these advances in materials have triggered deep investigations on constructing high‐efficiency power generation and cooling devices based on PbSe. Finally, a personal summary and outlook are presented on how to fully exploit the high‐ranged thermoelectric performance of PbSe materials and manufacture high‐efficiency power generators and coolers, thus promoting practical applications in the future.

Roadmap for Power Generation of Industrial Hot Extruded Bi2Te3-Based Thermoelectric Device in Real-World Heat Sources.

Recovering waste heat through thermoelectric (TE) technology is critical for enhancing energy efficiency. However, commercial devices often require n- and p-type thermoelectric units to have similar cross-sectional areas and conductivities, complicating optimization of their figure of merit (ZT). Moreover, real-world heat sources are not constant temperature sources, and only heat flux can be measured. Given these constraints, selecting appropriate parameters for TE devices to maximize their output power for specific heat sources is of significant scientific and practical importance. In this work, we studied a series of n- and p-type Bi2Te3-based TE materials, prepared using commercial hot extrusion techniques, with average conductivities of approximately 650 S cm-1, 820 S cm-1, 1050 S cm-1, and 1300 S cm-1 over the temperature range of 50-250 °C. These materials were assembled into four different thermoelectric devices (HE1, HE2, HE3, and HE4). Finite element simulations for devices HE1, HE2, HE3, and HE4 (TE leg: 1.4 mm × 1.4 mm × 1.6 mm, device area: 40 mm × 40 mm) showed maximum power densities of 3953.5 W m-2 and 1300.8 W m-2 at 67,000 W m-2 and 33,500 W m-2 heat fluxes, respectively. The fabricated devices achieved maximum power densities of 2907.1, 3014.0, 2910.9, and 2525.4 W m-2 at 67,000 W m-2 heat flux, with discrepancies attributed to interface thermal resistance. Based on these findings, we have plotted output performance roadmaps for TE devices with different average electrical conductivities under various heat flux densities (67,000 W m-2 and 33,500 W m-2) as functions of external load and TE leg height. These roadmaps enable rapid design of TE devices tailored to specific external heat source conditions and cost requirements, thereby maximizing waste heat recovery. This study's use of electrical conductivity as a performance indicator for final device output power density offers direct guidance for practical waste heat recovery applications.

Sizing large-scale industrial heat pump for heat recovery from treated municipal sewage in coal-fired district heating system

Electrification of district heating and deep integration of sectors of national economies are fundamental elements of the future smart energy systems. This paper discusses the problem of optimal sizing of large-scale high-temperature heat pumps using treated sewage water as a heat source in a coal-fired district heating system. The study presents an approach to modelling of heat pump system that enables techno-economic analysis for investment decision making. Such analysis is enabled by a black-box-type identification model of the selected industrial heat pump. The model was developed based on the data generated by physical modelling of the heat pump using Ebsilon Professional software. In addition, it is proposed that the heat pump system is integrated with a dedicated photovoltaic power plant. The case study takes into consideration site-specific technical, economic, ecological, and legal constraints, weather conditions, hydraulic performance of the heat-ing network, and variability of loads within the sewage and the district heating systems. The results revealed that the proposed modelling approach is effective regarding multiple simulations and system optimisation. In addition, it was found that large-scale heat pump projects can be technically feasible and profitable if the heat pump is appropriately sized and operated. In the given case, the optimum size of the heat pump for a city of around 180 000 inhabitants is around 12 MW under maximum winter load.

Waste Heat Utilization in Marine Energy Systems for Enhanced Efficiency

The maritime industry, central to global trade, faces critical challenges related to energy efficiency and environmental sustainability due to significant energy loss from waste heat in marine engines. This review investigates the potential of waste heat recovery (WHR) technologies to enhance operational efficiency and reduce emissions in marine systems. By analyzing major WHR methods, such as heat exchangers, Organic Rankine Cycle (ORC) systems, thermoelectric generators, and combined heat and power (CHP) systems, this work highlights the specific advantages, limitations, and practical considerations of each approach. Unique to this review is an examination of WHR performance in confined marine spaces and compatibility with existing ship components, providing essential insights for practical implementation. Findings emphasize WHR as a viable strategy to reduce fuel consumption and meet environmental regulations, contributing to a more sustainable maritime industry.

Comprehensive performance evaluation of steam generating heat pumps for industrial waste heat recovery

Steam generating heat pump (SGHP) is a key technology for industrial decarbonization. For comprehensive evaluation of the feasibility and reliability of SGHP in different industrial sector, the work develops a thorough evaluation model for assessing the performance of SGHP by considering waste heat recovery, CO2 trading value, and pollutant emission cost, in addition to the conventional evaluation criteria. This work presents a thorough comparison of the thermodynamic performance and sustainability of various types of SGHPs across different industrial sector. Additionally, the conflicting relationships between the coefficient of performance (COP) and exergy efficiency are balanced through the application of the technique for order preference by similarity to ideal solution (TOPSIS). The results show that all the indexes of SGHP connected to an open heat pump (SGHPO) with different application scenarios are higher than those of SGHP connected to a flash tank (SGHPF). At the most unfavorable operating condition of the system, the COP minimum value is 1.31 and the exergy efficiency minimum value is 20.42%. These results indicate that replacing the coal-fired boiler with SGHP is feasible and the work could provide theoretical guidance for optimal design and equipment manufacture.

Physiological Effects of TolC-Dependent Multidrug Efflux Pumps in Escherichia coli: Impact on Motility and Growth Under Stress Conditions.

Enterobacteriaceae possess eight TolC-dependent multidrug efflux pumps: AcrAB-TolC, AcrAD-TolC, AcrEF-TolC, MdtEF-TolC, MdtABC-TolC, EmrAB-TolC, EmrYK-TolC, and MacAB-TolC, which efflux bile salts, antibiotics, metabolites, or other compounds. However, our understanding of their physiological roles remains limited, especially for less-studied pumps like EmrYK-TolC. In this study, we tested the effects on swimming motility and growth under stress conditions of Escherichia coli mutants individually deleted for each inner-membrane transporter component of all eight TolC-dependent pumps, a mutant deleted for the AcrB-accessory protein AcrZ, and a mutant simultaneously deleted for all eight pumps (ΔtolC). We found that all mutants tested, except the ΔemrY and ΔacrZ mutants, displayed increased swimming motility. Additionally, the loss of each individual TolC-dependent pump or AcrZ did not reduce growth and sometimes even enhanced it compared to the parental strain under various growth conditions: temperature (LB at 25, 30, 37, and 42°C), pH (LB at pH 6.0, 7.4, and 9.0; and LB buffered to pH 6.0, 7.4, and 8.25), LB with limited air exchange, and nutritional stress (M9-glucose or M9-glycerol). In contrast, the ΔtolC mutant grew significantly slower than the parental strain under all conditions tested except in LB-TRIS pH 7.4 and LB with limited air exchange. Overall, these findings indicate that while individual TolC-dependent pumps are generally dispensable for growth under many stress conditions in the absence of antimicrobials, possibly due to their partially overlapping substrate profiles, TolC-dependent efflux is required for maximal growth under most conditions.

Evaluation of the Heat Transfer Performance of a Device Utilizing an Asymmetric Pulsating Heat Pipe Structure Based on Global and Local Analysis

PHPs (pulsating heat pipes) are widely used as an efficient heat transfer element in equipment thermal management and waste heat recovery due to their flexibility. The purpose of this study was to design a heat transfer device that utilizes an asymmetric pulsating heat pipe structure by adjusting the lengths of selected pipes within the entire circulation pipeline. In the experiment, a constant temperature water bath was used as the heat source, with heat dissipated in the condensing section via natural convection. An infrared thermal imager was used to record the temperature of the condensing section, and the local wall temperature distribution was measured in different channels of the condensing section. Based on an in-depth analysis of the wavelet frequency, the following research conclusions are drawn: Firstly, as the heat source temperature increases, the start-up time of the pulsating heat pipe is shortened, the operating state changes from start–stop–start to stable and continuous oscillation, and the oscillation mode changes from high amplitude and low frequency to low amplitude and high frequency. These changes are especially pronounced when the heat source temperature is 80 °C, which is when the thermal resistance reaches its lowest value of 0.0074 K/W, and the equivalent thermal conductivity reaches its highest value of 666.29 W/(m·K). Secondly, the flow and oscillation of the working fluid can be effectively promoted by appropriately shortening the length of the condensing section of the pulsating heat pipes or the heat transfer distance between the evaporation and condensing sections. Third, under a low-temperature heat source, the oscillation frequency of each channel of a pulsating heat pipe is found to be low based on wavelet analysis. However, as the heat source temperature increases, the energy content of the temperature signal of the working fluid in each channel changes from a low- to a high-frequency value, gradually converging to the same characteristic frequency. At this point, the working fluid in the pipes no longer flows randomly in multiple directions but rather in a single direction. Finally, we determined that the maximum oscillation frequency of working fluid in a PHP is around 0.7 HZ when using the water bath heating method.

Research on the Basic Properties and Preparation Methods of Heat Conversion Materials

The purpose of this literature review is to discuss the research progress and application prospects of high-efficiency thermoelectric conversion materials. In recent years, high-efficiency thermoelectric materials have garnered extensive attention due to their significant applications in waste heat recovery and energy conversion. This paper reviews various types of thermoelectric materials, including metal chalcogenides, silicides, and skutterudite materials, and analyzes their synthesis methods, properties, and advantages and disadvantages. The findings indicate that chemical vapor deposition (CVD), hydrothermal synthesis, and hot pressing are the primary methods for preparing thermoelectric materials, each with distinct advantages and limitations. Nevertheless, by optimizing the preparation processes and material compositions, high-efficiency thermoelectric materials are poised to play a crucial role in the field of sustainable energy in the future. This review summarizes the key findings of current research and suggests potential directions and challenges for future studies.

Performance of sCO2 Cycles for Waste Heat Recovery and Techno-Economic Perspective as Gas Turbine Bottoming Cycle

Abstract Supercritical carbon dioxide (sCO2) cycles are compact, cost-effective and widely adaptable to various heat sources, including the waste heat from gas turbine (GT) exhaust gases. While the addition of a steam cycle enhances the typical 40% efficiency of GTs up to 60%, their substantial investments render them less appealing for smaller GTs. This creates an opportunity for sCO2 cycles, but a comprehensive comparison of their performance with that of steam across a range of applications remains lacking. Moreover, their applicability to various industrial scenarios based on existing installations is missing from a techno-economic standpoint. To address these needs, four promising sCO2 cycles are evaluated and optimized using Aspen, and compared with the simple steam cycle. Their techno-economic performances are then investigated for 20 industrial GTs of different size up to the larger combined cycle gas turbine (CCGT) units incorporating amine-based carbon capture systems. Due to the significant investments required by the carbon capture unit, the implementation of a CC unit is only investigated for the largest CCGT units. The analysis yielded performance maps demonstrating comparable performances for sCO2 and steam cycles, as well as significant techno-economic advantages for sCO2 bottoming cycles for smaller GTs. However, when it comes to larger GTs combined with reheats and expansions steam cycles, sCO2 cannot outperform them in current technological standards. Nevertheless sCO2 cycles offers an attractive alternative, facilitating cogeneration. Among the different approaches designed to integrate the heat requirements of amine-based capture, steam cycles have always proved more suitable because of the thermal stability of amines. In conclusion, the research underscores the cost-effectiveness and adaptability of sCO2 cycles for heat recovery applications, particularly as bottoming cycles for smaller GTs, while larger GTs present a challenge. The work conducted sheds light on the substantial promise of sCO2 cycles, encouraging further exploration and implementation of these systems in the energy sector.

Intelligent Optimization and Impact Analysis of Energy Efficiency and Carbon Reduction in the High-Temperature Sintered Ore Production Process

The coordinated optimization of energy conservation, efficiency improvement, and pollution reduction in the sintering production process is vital for the efficient and sustainable development of the sintering department. However, previous studies have shown shortcomings in the multi-objective collaborative optimization of sintering systems and the quantification of pollutant impacts. To address these, this paper proposes a multi-objective optimization method integrated with the NSGA-III algorithm and establishes an integrated system optimization model for sintered ore production and high-temperature waste heat recovery. The results demonstrate significant improvements: energy utilization efficiency increased by 0.67%, energy consumption decreased by 17.3 MJ/t, production costs were reduced by 11.45 CNY/t, and the emissions of CO2, SO2, and NOx were reduced by 0.464 kg/t, 0.034 kg/t, and 0.008 kg/t, respectively. Additionally, the study identified optimal configuration parameters and analyzed the quantitative impact of several key factors on multiple indicators. The results also show that reducing the water content of the mixture, decreasing the middling coal content in the fuel, and increasing the thickness of the material layer are effective strategies to reduce energy consumption and pollutant emissions in the sintering process. Overall, implementing these optimizations can bring significant economic and environmental benefits to the steel industry.

Improving the air environment of vehicle cabins

BACKGROUND: The use of an innovative irrigated nozzle for air purification in the cabins of small class tractors is justified. The use of it makes it possible to comprehensively solve the problem of the state of air environment in the case of tractors operation in conditions of limited air exchange. AIM: Reduction of the content of harmful substances in the air of small tractors’ cabins. METHODS: Physical and chemical processes -chemical processes, during which the cabin air can be purified from harmful substances in the air cooler nozzle, are taken into account. RESULTS: The irrigated nozzle developed for the air coolers of the cabins of the mentioned tractors makes it possible to clean the exhaust gases from harmful impurities. CONCLUSION: Nozzles of a regular structure, irrigated with water with sodium bicarbonate and potassium permanganate dissolved in it, make it possible to comprehensively solve the problem of improving the state of air environment in the case of small class tractors operation in conditions of limited air exchange.

Performance Analysis of Cement Plant Waste‐Heat Recovery for Power Generation Based on Partial Evaporating Cycle with Ejector

In the cement industry, much waste heat is released into the environment. The organic Rankine cycle is widely utilized to harness waste heat for power generation. However, significant energy is lost in the heat recovery process due to the finite temperature difference between the heat source and working fluid, resulting in low power output andefficiency. To enhance the heat recovery from the cement flue gas and increase power output and overall efficiency, a novel partial evaporating cycle with ejector is proposed and investigated in this study. Pinch point analysis is performed to characterize the heat recovery process in the evaporator. The effects of the evaporating temperature, outlet quality of the evaporator, and exit pressure of the primary expander on system performance are also investigated. Results show that partially evaporating the fluid improves heat matching and reduces the irreversibilities in the evaporator by up to 18.1% when the outlet quality of the fluid is 0.33. Maximum net power of 803.15 kW can be generated with an evaporating temperature of , outlet quality of 0.33, and expander exit pressure of 1054.9 kPa. Additionally, the inclusion of the ejector increases the net power produced by up to 76.07 kW.

Investigating the concentration and health risk assessment of bioaerosols in the surgery centers and hospital operating rooms of Shahid Beheshti University of Medical Sciences

Introduction: Due to the special conditions in operating rooms, infection control is important to maintain health. So, the aim of this study was to survey of air exchange rate/changes per hour (ACH) and health risk assessment of bioaerosols in the surgery center or hospital operating rooms. Materials and Methods: The results of measuring of bioaerosols by pollution measurement companies were used, in 1401. In 1402, 10 operating rooms were randomly selected and the reliability of the results was examined for these two years. Sampling and analysis of the samples was provided based on the NIOSH 0800 method and ACH were measured by a anemometer. The relationship between the number of bioaerosols and ACH, and also, the reliability between results were calculated with the PCC and the ICC test, respectively, in SPSS-V22 software. The health risk assessment and the probability of risk were estimated by Monte Carlo simulation, in Crystal Ball software. Results: Among 62 operating rooms, the average number of bacterial and fungal colonies was 69.73±14.59 CFU/m3 and 21.67±4.52 CFU/m3, respectively, which is less than the recommended limit of WHO. The average ACH was 19.67±2.18 per hour. No significant relationship was observed between ACH and the number of colonies (p-value ≥ 0.05). Risk assessment for bacteria and fungi were at an acceptable level and the concentration of bioaerosols was recognized as the most sensitive variable influencing the risk. Conclusion: Increasing ACH will not lead to a reduction in the load of bioaerosol pollution in operating rooms, which can be very important in the management of reducing energy consumption.

Performance Enhancement in Air Gap Membrane Distillation Using Heat Recovery Configurations

Experimental investigations were conducted on an air gap membrane distillation (AGMD) unit to evaluate the impact of heat recovery on system performance. The study utilized a steady-state heat source in conjunction with a spiral air gap membrane module for water desalination. The process was implemented using two configurations aimed to minimize heat loss enhancing productivity, gain output ratio (GOR), and thermal efficiency. The experiments involved feedwater with salt concentrations ranging from 10,000 to 30,000 ppm. The measurements were recorded for inlet and outlet temperatures of the heat source, water productivity, and thermal efficiency at various coolant and water feed flow rates. These configurations effectively addressed critical technical challenges in thermal AGMD systems by optimizing heat recovery. The incorporation of heat recovery resulted in a significant increase in water productivity by 37.07% compared to systems without heat recovery while maintaining the same initial heat input. The heat recovery in series (HRSS) and parallel (HRPS) configurations resulted in power consumption reductions of approximately 29.7% and 23.1%, respectively compared to the conventional configuration (CC) at a flow rate of 12 L/min. The levelized cost of water (LCOW) for the AGMD system was comprehensively evaluated and found to be $ 7.71 per cubic meter. This figure reflected the total cost of water production over the system's operational lifespan including capital expenditures, operating and maintenance costs, and energy consumption. The calculated LCOW provides a clear indicator of the system's economic viability, demonstrating the cost required to produce each cubic meter of water through the AGMD.

Solar-driven collaborative thermochemical energy storage and fuel production via integrating calcium looping and redox cycle

To better utilize solar energy and reduce CO2 emissions, this study proposes a novel idea of solar-driven thermochemical energy storage and fuel production via integrating calcium looping and redox cycle. Such integrated system design not only can realize solar energy storage and CO2 capture based on thermochemical reversible reaction of CaO/CaCO3, but also can achieve fuel production through thermochemical conversion of captured CO2 into CO based on redox cycle. More interestingly, the temperature required for CaCO3 calcination of calcium looping matches the temperature for the oxidation reaction of redox cycle, which means a good connection between calcium looping and redox cycle. Additionally, a solar-driven thermochemical reactor system and its comprehensive thermodynamic model of calcium looping and redox cycle are developed to present the performance of integrated system. Results indicate that such integrated system can achieve a 43.54 % of solar energy converted into chemical energy (40.53 % obtained by calcium looping and 3.01 % obtained by redox cycle) even after 100 cycles. Moreover, the solar-to-chemical efficiency can reach 57.69 % and solar-to-fuel efficiency can reach 32.76 % after 100 cycles, when the heat recovery is considered (heat recovery effectiveness is assumed to be ηrecovery = 70 % in this work). This study presents a promising path to simultaneously achieve solar energy storage, CO2 capture and renewable fuel production.

Exergy efficiency improvement by compression heat recovery for an integrated natural gas liquefaction-CO2 capture-NGL recovery process

For liquefied natual gas production, cryogenic distillation offers lower thermal energy consumption and a more compact footprint for carbon capture unit than the widely used chemical absorption. However, the reduction in thermal energy consumption comes at the cost of increased power consumption. To reduce the power consumption of cryogenic distillation based natural gas lqiuefaction plants, an integrated process for liquefied natual gas production, cryogenic CO2 capture and natural gas liquids recovery is proposed, which is called the base process. This base process is further integrated with a heat recovery unit (Organic Rankine cycle or Kalina cycle) to investigate the optimal utilization of compression heat in the system. The proposed processes are modeled in Aspen HYSYS and optimized using a genetic algorithm installed in Matlab. The results show that specific power consumption of the base case is 0.385 kWh/Nm3 NG. Due to the lack of compression heat recovery, significant exergy loss occurs at the water coolers, accounting for approximately 37 % of the total system exergy destruction. Among the evaluated methods, the supercritical Organic Rankine cycle, using R1234ze as the working fluid, recovers approximately 60 % of the exergy from compression heat with an 8.7 % improvement in system exergy efficiency. The subcritical Organic Rankine cycle, using R600a as the working fluid, achieves a slightly lower exergy efficiency improvement of 7.1 %. The Kalina cycle, while less efficient, still improves the system’s exergy efficiency by 6.3 %. Economic analysis reveals that the total annualized cost of the base process is $8,441,416, with a levelized cost of $0.1411/kg. The subcritical Organic Rankine Cycle provides the most cost-effective solution, with the lowest total annualized cost of $8,305,154 and a levelized cost of $0.1402/kg. The Kalina cycle ranks second in cost-effectiveness, with a total annualized cost of $8,345,914 and a levelized cost of $0.1405/kg NG. Although the supercritical ORC requires the highest capital investment, it proves more cost-effective than the base process due to its reduced annual operating costs.

Enhanced thermochemical heat storage performance of CaO/CaCO3 via pyroligneous acid impregnation and Co/Mn co-doping

Calcium-based thermochemical heat storage (TCHS) is an economical and environmentally friendly technology for efficient heat storage. It can strengthen the flexibility in power systems of renewable energy and promote the recovery and storage of waste heat in energy-intensive industries. However, CaO/CaCO3 is extremely prone to sintering at operational temperatures. Consequently, a cost-effective approach was proposed to synthesize calcium-based TCHS materials modified by pyroligneous acid (PA) impregnation and co-doping with dual transition metals. The heat storage performance, physicochemical property, and anti-sintering mechanism of synthesized CaO were comparatively examined. The sample prepared with a molar ratio of Ca: Co: Mn = 100:3:7 (PACa-Co3Mn7) exhibited an initial energy storage density of 1.76 MJ/kg, which gradually rose to 1.88 MJ/kg. After 20 cycles, the value decreased by only 4.39 % from its peak, indicating outstanding TCHS performance. Characterization results indicated that the specific surface area and pore volume of PACa-Co3Mn7 were 10.48 m2/g and 0.035 cm3/g, which were 2.34 and 2.69 times those of CaO stemmed from the calcination of limestone, respectively. The fruitful pores provided pathways for CO2 diffusion within the CaO particles or CaCO3 product layer. The uniformly distributed Co and Mn elements combined to form Ca3CoMnO6. Ca3CoMnO6 could serve as the inert carrier that mitigated the grain-growth of CaO, thereby stabilizing the pore structure and resisting the sintering of PACa-Co3Mn7. Furthermore, density functional theory (DFT) calculations demonstrated that the free Mn and Co elements efficiently promoted the electrons transfer between CaO and CO2, which improved the reactivity of PACa-Co3Mn7. Therefore, CaO modified by PA impregnation and co-doping with dual transition metal is a promising candidate for the TCHS system.

Optimal design of a high-performance heat exchanger for modular thermoelectric generator towards low-grade thermal energy recovery

Thermoelectric generator (TEG) has been identified as a promising method for low-grade thermal energy recovery owing to their lack of moving parts, scalability, and compatibility with other devices generating waste heat. Heat exchanger, as one of the most important components of the modular TEG, plays a crucial role in improving the overall performance of the TEG. Nevertheless, flow maldistribution inside the heat exchanger results in uneven surface temperature field of the heat exchanger, which will ultimately limit the output capacity of the TEG. Achieving a homogeneous flow distribution within the heat exchanger while minimizing flow resistance is essential. To address this, optimization of a plate-shaped heat exchanger for the modular TEG is conducted using CFD analysis and the Taguchi method to identify the optimal combination of parameters. The optimized heat exchanger demonstrates a flow maldistribution intensity (ζ) of only 4.75 % and a low flow resistance of 1.16 kPa. Furthermore, a unit of the modular TEG is constructed using two optimized heat exchangers and commercial thermoelectric modules (TEMs), and its performance is analyzed via an analytical model. The results indicate that the power per module, net power density, and conversion efficiency reached 1.2 W, 51.4 kW/m3, and 1.92 %, respectively, at a temperature difference of 70 °C. These findings suggest that the optimized heat exchanger could provide high output performance compared with other literature, offering significant potential for low-grade heat energy recovery.

Performance evaluation of a steam generation system using a novel semi-open heat pump for waste heat recovery in dyeing industry

Performance evaluation of a steam generation system using a novel semi-open heat pump for waste heat recovery in dyeing industry