Exhaust Waste Heat Research Articles

Economic Analyses of a New Power and Cooling System at Low Temperature Applications

Recent research suggests that the implementation of more efficient combined cooling and power systems, which enable the cogeneration of electricity and cooling, can enhance the efficiency of hybrid plants. The present investigation is motivated by finding that, in the literature review on combined power and cooling systems, there is very limited information on the coupling of the organic Rankine cycle (ORC) and the ejector refrigeration cycle (ERC) with low sink temperatures. A suggested approach to do this involves using hot exhaust gas and waste heat engines to power an ORC hybrid system. To enhance the ORC–ERC system's performance, three heater configurations use waste heat from the ORC turbine exhaust, ejector, and engine waste heat to heat the working fluid. Renewable energy sources are the primary focus of most current research initiatives. The present research focuses on unique ORC and ERC systems, considered as combined power and cooling systems, with the goal of improving exergy performance at low temperatures. The suggested ORC–ERC can generate energy destruction of 69.85 kW at a source temperature of 155 °C, with an exergetic efficiency of 76.9% at the turbine. Setting the entrainment ratio at 0.5 results in a total sum unit cost of products (SUCP) of 465 $/kW‐h for the ORC–ERC. Furthermore, the 37.83% exergy destruction ratio introduces heat exchanger 2 (HE2) as the primary cause of the suggested ORC–ERC's irreversibility. A detailed parametric study reveals that altering the hot source temperature and entrainment ratio improves the system's SUCP. The current examination at high sink temperatures may be expanded to an advanced exergoenvironmental investigation.

Thermal flow and thermoelectricity characteristics in a sandwich flat plate thermoelectric power generation device under diesel engine exhaust conditions

Thermoelectric power generation (TEG) technology can be used to recover exhaust waste heat, but its effective application is restricted by bulky size and low thermoelectric conversion efficiency. The compactness evaluation of thermoelectric devices characterized by the power density is lacking. In this paper, a three-dimensional thermal flow and thermoelectricity multi-physics field model of a sandwich flat plate TEG device with multi-layer thermoelectric modules (TEMs) was established. An engine thermoelectric recovery bench test was carried out to verify the model and present the thermal parameters and output performance. The thermal, flow and electrical field distributions of the TEG device, as well as voltage, power and conversion efficiency with engine loads, and power density, were presented. The results show that the hot side temperatures, voltages and powers for each thermoelectric module (TEM) are greatly affected by the position occupied by the TEMs and engine loads. At full load and the coolant flow of 8.5 L/min, the device achieves the peak values of the power of 80.9 W and thermoelectric efficiency of 2.1 %, respectively. The device shows good compactness with the power density of 19.8 kW/m3, attributed to the reasonable arrangement of the collectors, coolers, and TEMs. This work can provide some insights of the relationship between the structural form and size, thermal parameters, electrical parameters and conversion efficiency of the sandwich type TEG device.

Investigation of low-GWP working fluids as substitutes for R245fa in organic Rankine cycle application

This study presents a thermo-economic assessment of three low-global-warming-potential (GWP) substitutes, R1233zd(E), R1234ze(Z) and R1234ze(E), for R245fa used in organic Rankine cycle (ORC) systems, considering two models with different heat sources. The exhaust heat from a diesel generator is served as heat source of Model I, while the waste heat of exhaust and jacket cooling water are used as heat source of Model II. It is noted that the working pressure of R1234ze(E) is much higher than that of R1233zd(E), R1234ze(Z) and R245fa in a fixed evaporation-temperature range. Furthermore, the system using R1234ze(E) has the minimum net power output for Model I, while it turns into the maximum net power output for Model II. In addition, both R1234ze(Z) and R1233zd(E) can be used as good alternative working fluids for R245fa because R1234ze(Z), R1233zd(E) and R245fa have close working pressures, maximum net power outputs, and minimum levelized energy costs. Compared to Model I, LECmin of R1233ed(E) and R1234ze(Z) are reduced by 10.8 % and 9.9 % and PBmin of R1233ed(E) and R1234ze(Z) are reduced by 11.5 % and 10.1 %, respectively, in Model II. However, R1233zd(E) has the highest minimum payback period for both Model I and Model II among the four working fluids investigated.

Dynamic performance and control analysis of supercritical CO2 brayton cycle for solid oxide fuel cell waste heat recovery

Due to the high-temperature operation of solid oxide fuel cell, recovering its exhaust waste heat is worthwhile. The supercritical CO2 cycle features low compression power consumption and high thermal efficiency, making it a promising power cycle. Therefore, this paper adopts the supercritical CO2 recompression cycle as the bottom cycle, combined with solid oxide fuel cell to form a joint system, further improving energy utilization. Given the long temperature response time of the solid oxide fuel cell and the variability of its exhaust waste heat with load changes, this paper innovatively proposes establishing an integrated dynamic model of the joint system, instead of directly providing heat source flow and temperature changes as in traditional research, to more accurately study the dynamic response of the cycle during solid oxide fuel cell startup and load variations. Based on this, a control strategy utilizing inventory control is proposed, and the feasibility of the control effect is verified. The research results indicate that the uncontrolled cycle may lead to safety issues with a significant increase in turbine inlet temperature when solid oxide fuel cell load increases. Under the control strategy, the turbine inlet temperature and main compressor inlet temperature are rapidly stabilized at the target values. The controlled cycle achieves higher efficiency compared to the uncontrolled cycle, particularly prominent during solid oxide fuel cell load reduction, with an efficiency increase of approximately 5.23%.

IMPROVING THE PLANTS EFFICIENCY OF THERMAL INCINERATION HOUSEHOLD WASTE BY RECOVERING WASTE HEAT

The work is devoted to research on the creation of recovery exchanger for waste heat exhaust gases of household waste incineration plants. The purpose of the work is to develop a technical solution for the heat recovery exchanger of waste incineration plants (WIP) and determine its thermal efficiency indicators. The main objectives of the study were to analysis of the modern experience of using the WIP and establish requirements for the creation of a exhaust gas heat recovery exchanger, develop a new technical solution for the heat recovery exchanger, and determine the change patterns in its main thermal indicators in different operating modes of the WIP. The known methods of thermal calculation of heat exchangers and the results of previous studies on the development and implementation of heat recovery equipment operating on dusty gases were used. The results of work on the creation of a new technical solution for an air-heating heat recovery exchanger with the ability to clean working surfaces from dust deposits are presented. The heat exchange surface of the heat recovery exchanger is composed of steel panels formed by tubes with membranes. The tubes applied have circular flow turbulizators on their internal surfaces. Turbulizators provide heat transfer intensification by 1.4 to 1.8 times with a moderate increase in aerodynamic resistance compared to other methods of heat transfer intensification. The regularities of changes in the main indicators of the heat recovery unit in different operating modes during the year in the practical range of changes in its input parameters were established. The research results show that, depending on the initial temperatures of gases and air, the excess air ratio in exhaust gases and the dust level of the working surface, the heat recovery exchanger provides heating capacity of 72-263 kW; cooling of exhaust gases to a temperature of 107-245 °C; heating of air to 96-220 °C. It was also established that the deposition of dust on the heat exchange surface of the heat recovery unit under the considered conditions leads to a decrease in the heating air temperature by 1.3-1.4 times and an increase in the final exhaust gas temperature by 1.1-1.2 times. At the same time, the heating capacity of the heat recovery exchanger is reduced by half. To increase heat recovery efficiency, it is necessary to periodically clean the working surfaces of the heat recovery unit with compressed air.

Power Augmentation of Gas Turbine Using Exhaust Flue Gas Operated Vapor Absorption Machine

Industrial gas turbines (GT) that operate at constant speed are constant-volume-flow combustion machines. As the specific volume of air is directly proportional to the temperature, an increase in air density results in a higher air mass flow rate at low air ambient temperatures. This results more mass of air is now passes through same volume gas turbine space. Consequently, the gas turbine power output increases proportionally with the increase in air mass flow rate. For geographic regions where warm and humid months are predominant throughout the year, significant power loss occurs during these months, and a higher rate of expensive fuel is fired at reduced power output. A gas turbine inlet air cooling technique is a useful option to enhance GT output. One of the innovative options for power augmentation of gas turbine is inlet air conditioning using a vapor absorption machine (VAM). Using VAM for GT intake air conditioning has the advantage over other systems in that it can be operated from waste heat. Many gas turbine machines, particularly natural gas pumping stations, are operated without heat recovery steam generator (HRSG) or heat recovery option. Valuable heat energy is escaped with exhaust flue gas in these systems. This paper demonstrates how GT exhaust waste heat can be utilized for its own power generation enhancement. In this study, a flue gas-based vapor absorption machine is selected for cooling the inlet air of a 26 MW gas turbine, which is used to drive the booster compressor of a natural gas pumping station. The capacity of the VAM for the required cooling effect has been calculated. The expected GT power enhancement from intake air gas conditioning has also been estimated in this paper.

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.

Performance analysis of a multi-tube exhaust waste heat recovery methanol reforming to hydrogen reactor

Performance analysis of a multi-tube exhaust waste heat recovery methanol reforming to hydrogen reactor

Thermodynamic and techno-economic evaluation of a CAES based cogeneration system integrated with high-temperature thermal energy storage and ammonia absorption refrigeration

The development of compressed air energy storage (CAES) technology can ensure the safe and stable operation of the power system, promote the consumption of renewable energy and reduce carbon emissions. In order to improve the comprehensive performance of the CAES system and meet the diversified demand of energy, a cooling, heating and power cogeneration system based on compressed air energy storage with high temperature thermal energy storage and ammonia absorption refrigeration are developed in this study. The compression heat of the energy storage process and the exhaust waste heat of the energy release process are fully utilized in this system. Thermodynamic analysis, techno-economic evaluation and parametric analysis are conducted. The thermodynamic analysis results show that the proposed system achieve an ENE of 81.51 %, an EXE of 53.51% and an ESD of 7.08 kWh/m3 under the design condition. The economic analysis results indicate that the NPV, IRR and LCOE for a system life of 25 years are 489497 $, 32.1 % and 0.0953 $/kWh, with a DPP of 3.91 years. Sensitivity analysis results conclude that the outlet temperature of HTTES, and the maximum and minimum operating pressures are the key parameters affecting the system performance.

A Hybrid Heavy Duty Diesel Power System for Off-Road Applications—Concept Validation

Abstract A multiyear power system R&D program was completed with the objective of developing an off-road hybrid heavy duty diesel engine with front end accessory drive-integrated energy storage. This system was validated to deliver 10.5–25.6% reduction in fuel consumption over current Tier 4 Final-based 18L diesel engines, over various off-road machine application cycles. The power system consisted of a downsized heavy-duty diesel 13L engine containing advanced combustion technologies, capable of elevated peak cylinder pressures and thermal efficiencies, thermal barrier coatings, exhaust waste heat recovery via SuperTurbo™ turbocompounding, and hybrid energy assisting and recovery through both mechanical and electrical systems. Following the concept definition, design, and analysis phases of the program, the final phase focused on building and validating the performance and efficiency in laboratory tests. While aspects of the system such as start/stop and reduced off-road cooling package energy losses were only analytically evaluated, the main 13L concept engine with full hybrid system was successfully built and tested in steady-state and in transient certification and real-world application cycles. Extensive simulations in Caterpillar's DYNASTY™ software environment utilized the validation test data to assess performance more fully and confidently over varied cycles and strategies. An average fuel consumption reduction of 17.9% was realized, and the majority (∼13%) of the benefit stemmed from the core concept 13L engine. To conclude, a total cost of ownership analysis provides context to commercial viability and where adoption focus should be placed.

Heat recovery technology and energy-saving effect analysis apply to cleanroom exhaust waste heat characteristics

To investigate the efficient waste heat recovery (WHR) technology suitable for cleanrooms, the energy-saving effectiveness of three WHR technologies of heat pipe, liquid circulation, and solution absorption was compared and the comparison was conducted across four different climate regions: severe cold, cold, hot summer cold winter, and hot summer warm winter. The findings reveal that the energy efficiency ratio (EER) of the heat pipe WHR surpasses that of the other two technologies. Specifically, the EER values for the heat pipe WHR in the four climate regions are 21.0, 15.4, 14.1, and 7.3, respectively. Furthermore, a two-stage heat pipe WHR technology is proposed to enhance the heat recovery efficiency of the heat pipe WHR technology, and experimental research has been conducted. The results show that the average heat recovery efficiency reaches 61.64 % when the wind speed is 2 m/s and the new exhaust air temperature difference is 6–11 °C. Compared to the single-stage HPHE, the use of two-stage heat pipe WHR technology in the four climates regions resulted in 6.9 %, 12.8 %, 21.5 %, and 13.6 % higher net heat recovery, 7.1 %, 13.5 %, 16.6 %, and 40.2 % higher energy-efficiency ratios, and 8.2 %, 13.5 %, 12.2 %, and 37.3 % shorter static payback periods, respectively. The heat recovery solution shows a good application prospect in cleanroom WHR.

Cost-Effective Design of Exhaust Waste Heat Recovery System: A Numerical and Optimization Approach

Cost-Effective Design of Exhaust Waste Heat Recovery System: A Numerical and Optimization Approach

Thermodynamic and thermo-economic analyses of a coupled heat-pump system for low-grade exhaust-air heat exchange in mines

ABSTRACT Combining mine exhaust waste heat with existing heat pump technology is a promising technical route to realise the efficient extraction and scientific use of low-grade waste heat resources in mines and to solve the problem of insufficient heat supply in remote mining areas. This study proposes a new type of mine-exhaust-air heat exchange coupled with heat-pump waste-heat-utilisation system based on deep enthalpy heat extraction. Using a mining area in Northwest China as a representative case, this study establishes a systematic exergy analytical model and a thermo-economic model. Through an in-depth analysis of the different evaporation temperatures and condensing temperatures, the system’s energy efficiency ratio (COP) reaches its optimal performance, with the total exergy efficiency surpassing 90%. The minimum efficiency of the subsystem return air heat exchanger is 35%. The unit thermal costs of the mine exhaust air waste heat utilisation system and a conventional coal-fired boiler system are 0.1291 and 0.1573 million RMB/kW·h, respectively. This is a thermal economics cost saving of 21%. The studied system demonstrates great economic viability and the potential for energy saving throughout its life cycle.

Prediction of electric power performance of the exhaust waste heat recovery system of an automobile with thermoelectrical generator under real driving conditions by means of machine learning algorithms

In internal combustion engines, approximately 40% of the thermal power obtained from fuel burning is thrown out to the environment from the exhaust system. Implementations of waste heat recovery systems with thermoelectrical generator over exhaust system have become widespread as it is the waste heat resource with the highest temperature in a vehicle. During literature research, experiments related to waste heat recovery under real road conditions are very few and no study on estimation of system performance by machine learning algorithms has been found; therefore, Toyota Corolla has designed an air-cooled waste heat recovery system using 3 thermoelectrical generators for the exhaust system of the automobile. During the road tests, temperature and electric power generation values obtained as per gear, vehicle speed and engine speed have been recorded. In the study, a dataset consisting of 10 attributes was created with each record as a result of the path test. Using this dataset, Random Forest, Support Vector Machine (SVM) and Naive Bayes machine learning algorithms estimated the electrical power to be generated from the thermoelectric generator recovery system. In the study, 7 electric power classification estimates were made. In the estimation process, 76% of the dataset was used for training and 24% was used for testing. In terms of estimation success; an estimation success of 96.6% has been achieved by Random Forest method; 94.6% by Support Vector Machine (SVM) method; and 76.7% by Naive Bayes method. The results show that prospective electricity generation estimation can be achieved with high level of accuracy.

Energy and exergy analysis of a thermoelectric generator system for automotive exhaust waste heat recovery

Thermoelectric generators are a viable solution for recovering and producing energy utilizing wasted energy in automotive exhaust. Exergy analysis can help identify irreversible losses that occur during the transfer of exhaust energy, which is essential for comprehending and developing exhaust thermoelectric generator systems. In this study, we proposed a model based on thermodynamic of the exhaust thermoelectric generator and conducted energy and exergy analyses. The results indicate that convective heat transfer exergy loss and PN junction thermal conductivity exergy loss are the primary exergy losses of the exhaust thermoelectric generator, accounting for more than 52.0 % of the total. Increasing the temperature of exhaust can boost the performance of systems, but it may also reduce the proportion of available energy obtained by the cooling water. When the exhaust heat transfer coefficient is increased to 300, the convective exergy losses of the exhaust can be reduced to 17.6 %, resulting in an overall exergy efficiency of 38.8 %. Furthermore, by increasing the exhaust flow rate from 10 g/s to 50 g/s, the power generation capacity has increased by a factor of 6.87, with little change in exergy losses. These findings are valuable for developing high-efficiency exhaust power generators.

High-Performance Paper-Based Thermoelectric Generator from Cu2SnS3 Nanocubes and Bulk-Traced Bismuth.

Flexible paper-based thermoelectric generators (PTEGs) have drawn significant interest in recent years due to their various advantages such as flexibility, adaptability, environment friendliness, low cost, and easy fabrication process. However, the reported PTEG's output performance still lags behind the performance of other flexible devices as it is not so easy to obtain a compact film on a paper-based substrate with desirable power output with the standard thermoelectric (TE) materials that have been previously utilized. In this direction, Cu2SnS3 (CTS), an earth-abundant, ternary sulfide, can be a good choice p-type semiconductor, when paired with a suitable n-type TE material. In this article, CTS nanocubes are synthesized via a simple hot injection method and a thick film device on emery paper was prepared and optimized. Furthermore, a flexible, 20-pair PTEG is fabricated with p-type CTS legs and traced and pressed n-type bismuth legs assembled using Kapton tape that produced a significantly high output power of 2.18 μW (output power density ∼0.85 nW cm-2 K-1) for a temperature gradient of ΔT = 80 K. The TE properties are also supported by finite element simulation. The bending test conducted for the PTEG suggests device stability for up to 800 cycles with <0.05% change in the internal resistance. A proof-of-concept field-based demonstration for energy harvesting from waste heat of a motorbike exhaust is shown recovering an output power of ∼42 nW for ΔT = 20 K, corroborating the experimental and theoretical results.

Experimental examination of the effect of thermal barrier coating in a 2-stroke gasoline engine on recovery performance in exhaust waste heat recovery system with thermoelectric generator and engine performance

In internal combustion engines, while the decrease in in-cylinder wall temperature increases the amount of energy passing towards the cooling system, it decreases temperature and pressure at the end of compression and accordingly reduces thermal efficiency of the engine. Moreover; combustion chamber elements are exposed to chemical corrosion and deformation as a result of uncompleted combustion in the cylinder. With thermal barrier coating application, the energy lost in cooling system will decrease and exhaust temperatures will increase in 2-stroke engines. Placement of a waste heat recover system with thermoelectric generator into the exhaust system can provide exhaust waste heat recovery and increase thermal efficiency of the engine. There is no study in the literature, which examines waste heavy recovery systems with thermal barrier and thermoelectric generator altogether. In this article, yttria stabilized zirconia coating has been applied by means of plasma spraying method in the combustion chamber of a 2-stroke gasoline engine, and effect of thermal barrier coating application on engine performance and exhaust waste heat recovery system has been examined experimentally. According the results of the experiment, maximum engine power has increased by 6.23%, maximum engine torque has increased by 6.02%, and specific fuel consumption decreased by 5.56%. While the exhaust temperatures have increased by 78.5 °C at maximum by means of thermal barrier coating application; by means of thermal barrier coating application with waste heat recovery system with thermoelectric generator, a higher waste heat recovery has been obtained by 64.8%.

Performance Optimization and Exergy Analysis of Thermoelectric Heat Recovery System for Gas Turbine Power Plants.

Thermoelectric (TE) waste heat recovery has attracted significant attention over the past decades, owing to its direct heat-to-electricity conversion capability and reliable operation. However, methods for application-specific, system-level TE design have not been thoroughly investigated. This work provides detailed design optimization strategies and exergy analysis for TE waste heat recovery systems. To this end, we propose the use of TE system equipped on the exhaust of a gas turbine power plant for exhaust waste heat recovery and use it as a case study. A numerical tool has been developed to solve the coupled charge and heat current equations with temperature-dependent material properties and convective heat transfer at the interfaces with the exhaust gases at the hot side and with the ambient air at the heat sink side. Our calculations show that at the optimum design with 50% fill factor and 6 mm leg thickness made of state-of-the-art Bi2Te3 alloys, the proposed system can reach power output of 10.5 kW for the TE system attached on a 2 m-long, 0.5 × 0.5 m2-area exhaust duct with system efficiency of 5% and material cost per power of 0.23 $/W. Our extensive exergy analysis reveals that only 1% of the exergy content of the exhaust gas is exploited in this heat recovery process and the exergy efficiency of the TE system can reach 8% with improvement potential of 85%.

Optimization design and performance analysis of methanol reforming reactor for exhaust waste heat recovery of marine engine

In order to improve the heat utilization of exhaust from the small or medium-sized ships without exhaust boilers, four types of methanol reforming reactors were designed and optimized via the field synergy principle. The effect of the operating parameters on the performance of optimized reactor under typical loads was also investigated. The analysis based on the field synergy principle shows that the R(S,1) reactor has higher heat transfer synergy performance, better evaporation performance, and more uniform vapour distribution at the inlet of the reaction section, which is more beneficial to the reforming reaction. The effect of the operating parameters on reactor performance shows that the reactor performs better at 75% load with hydro-alcohol molar fraction ratios (S/C) of 1.2 or 1.3. The engine load affects the reactor performance by influencing the temperature of the evaporation and reaction sections. The S/C of the mixed solution at the inlet of the reactor were set at 1.2 and 1.3 to explore the effect of engine loads on the reforming performance under E3 test cycle. The results show that the reactor performs better at S/C = 1.3 under the loads of 100, 75, and 25%; at S/C = 1.2, the reactor performed better under 50% load.

Thermodynamic and economic analysis of a novel thermoelectric-hydrogen co-generation system combining compressed air energy storage and chemical energy

With the adjustment of energy structure, the proportion of renewable energy is gradually increasing, and how to solve the problem of renewable energy consumption is becoming more and more prominent. Therefore, a novel thermoelectric-hydrogen co-generation system combining compressed air energy storage (CAES) and chemical energy (CE) is proposed. For energy storage, the system uses adiabatic compression with liquid piston to reduce the generation of compression heat, while using the generated compression heat to preheat the methanol. For energy release, the methanol is fed into the methanol steam reforming reactor (MSR) and the methanol decomposition reactor (MDR) in certain proportions for the hydrogen production reaction; the unreacted methanol and the carbon monoxide produced by the MDR are used as make-up heat for the reactors and the high-pressure air before the turbine, while the exhaust waste heat supplies heat to the customer. The thermodynamic, economic and environmental performances of the system were investigated separately by developing a mathematical model describing the system. The results show that under the design conditions, the system has an energy storage density of 12.00 kWh/m3, an energy efficiency of 88.47 %, an exergy efficiency of 77.04 %, a lifetime net present value of 59.20 M$, a payback period of 4 years, and a CO2 emission per unit of energy output of 227.85 kg/MWh. Increasing the thermostatic heat source temperature and increasing the reactor diameter and length increased the methanol conversion rate. Increasing heat exchange effectiveness of the heat exchanger and heat source temperature can all improve system thermodynamic and economic performance. The energy storage density, energy efficiency, net present value and profitability of the system varied parabolically with the reactor tube diameter. The system energy storage density had a maximum value of 12.03 kWh/m3 at a reactor diameter of 0.040 m.