Industrial Waste Heat Recovery System Research Articles

Preparation and characterization of steel slag-based low, medium, and high-temperature composite phase change energy storage materials

In this study, industrial solid waste steel slag was used as supporting material for the first time, and polyethylene glycol (PEG), sodium nitrate (NaNO3), and sodium sulfate (Na2SO4) were used as low, medium, and high-temperature phase change materials (PCMs). A series of shape-stable composite phase change materials (C-PCMs) were prepared by vacuum impregnation and mixing-sintering methods. The morphology, thermal properties, and thermal reliability of C-PCMs were characterized by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC). The results show that the three PCMs are uniformly dispersed in the pores of steel slag, and the maximum loading is 35 %, 40 %, and 50 %, respectively, and they have good chemical compatibility with steel slag. Compared with their pure PCMs, the three prepared C-PCMs showed a reduction in subcooling of 2.64 °C, 4.53 °C and 0.79 °C, respectively, and an increase in thermal conductivity of 172 %, 54.9 % and 82.4 %, respectively, all with good phase change thermal storage properties. Even after 100 thermal cycles, the latent heat retention rate was more than 97 %, which had good thermal reliability. Therefore, it can be concluded that the three kinds of low, medium, and high-temperature C-PCMs have considerable application potential in different temperature areas, such as building latent heat storage, solar energy storage systems, and industrial waste heat recovery system.

Performance characteristics of PCM based thermal energy storage system for fluctuating waste heat sources

The large temperature fluctuations of industrial waste heat pose great economic and operational challenge for the feasibility of industrial waste heat recovery systems. In this regard, Phase Change Material (PCM) based Thermal Energy Storage (TES) systems can effectively dampen large thermal fluctuations during the charging cycle. The current work focuses on the assessment of the performance of a shell and tube latent TES unit when subjected to fluctuating thermal cycles of waste heat from clinker cooling process (420 K − 600 K ) as Cycle 1 & 2 and internal combustion engines (360 K − 780 K ) as Cycle 3–5, using HITEC® industrial salt as PCM. The complete melting time of PCM for Cycle 1 is 41.6% higher than Cycle 2 whereas the average PCM temperature for Cycle 1 is found to be 9.3% lower than for Cycle 2. Similarly, Cycle 5 accelerates the PCM melting by 37.4% and 33.3% as compared to Cycle 3 and Cycle 4. The sharp dips in source temperatures decelerate the melting process and cause localized re-solidification of PCM. The PCM dampens the source temperature fluctuations by more than 80%. The constant overall PCM melting time for both fluctuating and mean temperature sources indicate the effectiveness of latent TES system.

The Thermal Economy of a Circulating Medium and Low Temperature Waste Heat Recovery System of Industrial Flue Gas

The waste heat recovered by traditional industrial waste heat recovery systems is mostly high-temperature flue gas and combustible gas, while the waste heat of medium and low temperature flue gas that accounts for more than 50% of the total waste heat resources has been ignored, which is not conducive to the effective energy saving of industrial production and manufacturing process. In the meantime, few studies have concerned about the changes in the economy of circulating industrial waste heat recovery system. Therefore, to fill in this research gap, this paper aimed at the economy problem of circulating medium and low temperature industrial waste heat recovery system and carried out a series of research. The paper completed the thermodynamic analysis of different medium and low temperature waste heat recovery modes of industrial flue gas, and gave the analysis steps of the economy of circulating medium and low temperature waste heat recovery system of industrial flue gas. The effectiveness and accuracy of the thermodynamic and thermo-economic models constructed in the paper were proved by experimental results.

Low-grade industrial waste heat utilization in urban district heating: Simulation-based performance assessment of a seasonal thermal energy storage system

In this study, a large-scale industrial waste heat heating system integrated with borehole thermal energy storage (BTES) and an absorption heat pump was proposed, designed, and assessed using long-term dynamic simulations. Simulations were performed with different reference combinations of storage volumes and circulation flow rates for the borehole heat exchanger, and a procedure for determining the optimal design parameters was demonstrated. The simulation results indicated that a large-scale BTES has significant potential for buffering short-term temperature variations in industrial waste heat recovery systems. The initial quasi-stable temperature of the BTES established itself gradually, and the energy input and output of the storage tended towards stability after 3–4 years of operations. The effect of increasing storage capacity tended to gradually decline with increasing circulation flow rate and storage volume after reaching a peak, becoming marginal at higher design parameter values. This result indicate that the storage volume and circulation flow rate of the system should be optimized according to an appropriate economic index, to maximize economic benefits. The simulation results emphasized the potential of large-scale seasonal BTES systems to be integrated with industrial waste heat recovery systems and district heating networks, to improve the stability of energy demand and efficiency.

(Invited) Ultra-Thin MEMS Thermoelectric Chip and Its Applications

Ultra-thin MEMS Thermoelectric Chip and Its ApplicationsZhiyu HuInstitute NanoMicroEnergy, Department of Micro/Nano-ElectronicsShanghai Jiao Tong University, Shanghai, China, 200240Email: zhiyuhu@sjtu.edu.cn : For a long time, mankind has been seeking inexhaustible energy in nature. There is an urgent need to obtain new types of sustainable, environmentally friendly and green energy to reduce our dependence on petrochemical energy. The thermoelectric generator (TEG) can directly convert heat into electrical energy through the Seebeck effect, thereby obtaining electrical energy, which makes it a promising environmentally friendly energy conversion method. TEG has many special advantages, such as no moving parts, no pollution, no noise, no mechanical vibration, etc. At present, all TEGs on the market is made with traditional method which yields high cost, low efficiency, not suitable for massive and economic production.Thermoelectric generator (TEG) can directly convert heat into electrical energy. Due to its special advantages, such as no pollution, no noise, no mechanical vibration, etc., TEG has been widely used in vehicles, wearable devices, solar energy systems, and industrial waste heat recovery systems. In order to promote the application of thermoelectric devices, it is necessary to improve the performance of thermoelectric materials through nanostructures. Generally, thermal resources are concentrated on increasing the temperature at the hot end of the TEG. In this article, the heat in the environment is pumped into the external space through radiant cooling (RC), thereby generating the cold end of the TEG and a continuous self-powered system was obtained.Taking advantages of micro/nano-fabrication and the scale effects of heat theory, we are able to design and build a thermoelectric chip in a large array and maintain a stable temperature difference between sub-micrometer-thick of a thermoelectric unit on a silicon wafer. The submicron-thick TEG containing more than 46,000 thermoelectric modules in series was fabricated on SiO2/Si. The combined Seebeck coefficients of Sb2Te3 and Bi2Te3 were adopted the average value which were evaluated to be 250 μV/K. The details of the fabrication method were proposed first and demonstrated in our previous work.Nanostructured multilayer thermoelectric films have been developed to improve thermoelectric efficiency. The effects of interface microstructure on the cross-plane thermal conductivities of the multilayer thin films have been extensively examined and the thermal transfer mechanism has been explored. Experimental results indicate that ultrathin thermoelectric device works stable and reliable, and is suitable for fabrication of thinner and higher integrality devices in mass production.We have demonstrated a novel energy utilization that MEMS-based thermoelectric chip can produce electricity by radiative cooling (RC) in day and night. Thermal emitter composed evaporated Ag layer and 12 alternating SiO2 and Si3N4 layer periods deposited on a silicon by plasma enhanced chemical vapor deposition (PECVD). The absorptivity of the thermal emitter is 80.8%. Here, the emission is caused by phonon-polaron excitation in the Si3N4 layer. SiO2 was chosen to fully reduce the adverse radiation loss because it has an absorption peak close to 9 μm in the atmospheric window due to its phonon-polaron resonance. The silver-plated layer can enhance the electromagnetic wave reflection without resonance.In addition, the MOST material that collected solar energy in Gothenburg，Sweden has been delivered to Shanghai, China by express mail, and successfully generated electricity on the MEMS TE chip a few months later.MEMS-based thermoelectric chips can use ultra-low thermal energy to directly generate electricity with a very small temperature difference. In future, when such advanced energy technology is wildly available and at very low costs, we then will obtain truly sustainable, completely environmentally friendly clean energy, and greatly reducing our dependence on petrochemical energy. MEMS-based thermoelectric chip can also be used as an ultra-sensitive temperature sensor, several testing examples will be introduced and with further discussions.

Updated results on the integration of metal–organic framework with functional materials toward n-alkane for latent heat retention and reliability

Phase change composites are in high demand in thermal management systems. Various supporting materials, including nanocomposites, have been employed to develop shape-stable phase change materials (PCMs). As the reliability of most composite materials has mostly been studied right after the preparation with specific thermal cycling measurements, it is difficult to analyze the long-term leakage-resistance capability and energy retention capacity. Additionally, achieving multifunctional phase change composites is a significant challenge for single supporting materials. Herein, we provide a follow-up report on the thermal performance of hybrid material-supported n-alkane after a storage time of one year and 50 heating/cooling cycles. The interconnected hybrid material composed of a metal–organic framework (MOF) and graphite improved the shape/thermal stability of tetradecane (TD). The as-synthesized MOF/graphite/TD composites exhibited a high latent heat retention capacity of 84.2%, low leakage rate of 1.25%, and high PCM loading capacity, making them suitable for thermal management applications, such as industrial waste heat recovery systems. Furthermore, the intermolecular interactions and capillary forces between the hybrid materials and TD provided high stability and compatibility. Therefore, the as-prepared hybrid material fabricated in this study can be important in the development of multidirectional composite PCMs with comprehensive thermal characteristics.

A Framework for Design and Operation Optimization for Utilizing Low-Grade Industrial Waste Heat in District Heating and Cooling

In the process industry, a large amount of low-grade waste heat is discharged into the environment. Furthermore, district heating and cooling systems require considerable low-grade energy. The integration of the two systems has great significance for energy saving. Because the energy demand of consumers varies in periods, the design and operation of an industrial waste heat recovery system need to match with the fluctuations of district energy demand. However, the impact of the periodic changes on the integration schemes are not considered enough in existing research. In this study, a framework method for solving above problem is proposed. Industrial waste heat was integrated with a district heating and cooling system through a heat recovery loop. A three-step mathematical programming method was used in design and operation optimization for multiperiod integration. A case study was conducted, and the results show that the multiperiod optimization method can bring significant benefits to the system. By solving the mixed integer nonlinear programming model, the optimal operation plans of the integration in different periods can be obtained.

Numerical study on acid condensation and corrosion characteristics of three-dimensional finned tube surface

Low temperature corrosion is a key factor affecting the performance and safety of heat exchanger for industrial waste heat recovery system. Acid dew point temperature and vapor condensation characteristics are two major parameters to evaluate corrosion behavior. However, previous studies focused solely on acid dew point temperature or condensation characteristics. In present paper, a numerical model was established to investigate the heat and mass transfer process of flue gas on three-dimensional finned tube surface and predict the acid dew point temperature and condensation characteristics simultaneously. Firstly, the effects of operation parameters were examined both by single variable method and orthogonal method. The results show that the flue gas inlet velocity and acid vapor concentration have the most significant effects on acid dew point temperature; the tube wall temperature and water vapor concentration have the most significant effects on the condensed acid solution concentration. Then, the corrosion characteristics was discussed and the optimization working parameters (the water vapor concentration in flue gas below 10.12% and the tube wall temperature above 349.3 K) are recommended.

A novel method for rotor profile optimization of high temperature screw expanders employed in waste heat recovery systems

High temperature expanders have always been employed in industrial waste heat recovery systems, where twin-screw expanders were frequently adopted. However, the significant thermal deformation of rotors contributes to much technical difficulty on the designation and manufacturing of high temperature twin-screw expanders. The profile should be optimized with consideration of its thermal deformation in high temperature working conditions. In this article, a novel method for twin-screw expander profile optimization is developed. The thermal deformation of rotors is considered with meshing pair rules and interlobe clearance presetting. Theoretical analysis on interlobe clearance is made any steam inlet temperature from 20°C to 400°C, while experimental facility was built to figure out its reliability at high temperature. The optimized profile proved the effectiveness of this method. The clearance decreases significantly, decreasing from 1.28 mm at the working temperature of 20°C to 0.16 mm at 400°C. The testing results illustrated that the significant thermal deformation of rotors causes much interlobe abrasion once the operating temperature reached 400°C. With clearance of 0.1 mm and the radius correction angle of 0.0758°, the screw expander was proved to be reliably working at 400°C.

Energy, exergy, economic and exergoeconomic (4E) multicriteria analysis of an industrial waste heat valorization system through district heating

The purpose of this article is to determine the multicriteria-optimal design of an industrial waste heat recovery system for district heating in Grenoble (France). Energy, exergy and cost flow balances were applied unit by unit allowing to assess the process performance based on two innovative methods. First, the performance assessment includes all units involved in the heat valorization process, not only focusing on the recovery system. Second, the yearly management of energy flows was optimized through mixed-integer linear programming, anticipating fluctuations in residential demands and waste heat availability. This multicriteria analysis with a systemic-anticipatory approach allowed to select the appropriate inlet temperature and storage capacity. It was found that the most promising inlet temperature and heat storage capacity are 35 °C and 30 MWh, respectively. With this design, the system recovers 41% of industrial waste heat, covers 48% of residential needs, has an estimated net present value of 11.7 million euros over 20 years, and reduces the district’s overall exergy destruction and exergy destruction costs by 20% (4.2 GWh/year) and 9% (286 k€/year), respectively. Remarkably, none of the mono-criterion analyses prioritized this design. Therefore, the multicriteria analysis with systemic-anticipatory approach was of utmost importance for detecting the most promising solution.

Performance and Sustainability Analysis of an Organic Rankine Cycle System in Subcritical and Supercritical Conditions for Waste Heat Recovery

This study addresses the performance analysis of a subcritical and supercritical Organic Rankine Cycle (ORC) with the addition of a preheater or superheater integrated with a turbofan engine. This analysis will try to explore the heat transfer throughout the evaporator for the purpose of determining the ORC output power and thermal efficiency. A simplified numerical model of the ORC for waste heat recovery is presented. The model depicts the evaporator by using a distributed model, and includes parameters such as the effectiveness, heat capacity and inlet temperature of the waste heat and the organic fluid. For a given set of initial parameter values, the output power and thermal efficiency, as well as the mass flow rate of the working fluid are acquired by solving the system’s thermodynamic cycle with the aid of MATLAB software. The model is then verified by using data from an industrial waste heat recovery system. The connection between the turbofan engine and the ORC system was established and evaluated by means of Thrust-Specific Fuel Consumption (TSFC) as well as fuel burn. It was found that the supercritical ORC with a preheater and superheater exhibits lower TSFC than the subcritical ORC, whereas the impact of the ORC in terms of waste heat recovery in relation to the environment and sustainability indices is quite small, but still considerable depending on the engine’s weight.

Energy- and exergy-based optimal designs of a low-temperature industrial waste heat recovery system in district heating

This paper illustrates how the choice of indicators changes the design of a waste heat recovery system in district heating. A prospective system in Grenoble (France) aims to valorize waste heat from the French National Laboratory of Intense Magnetic Fields (LNCMI) by injecting it at 85 °C to the nearby district heating network. We optimize its design for three possible waste heat temperatures: 35 °C (current), 50 °C (viable) and 85 °C (innovative). As major components, the system includes a thermal storage (ranging from 10 MWh to 40 MWh) and may include a heat pump depending on the waste heat’s temperature. Different optimizations are guided by two energetic indicators (one source-oriented, the other demand-oriented) and by the overall exergy efficiency. The system’s annual performance is assessed through the Sankey and Grassman diagrams and compared between optimal designs. Yearly simulation included optimal management of the thermal storage, through mixed-integer linear programming. The demand-oriented optimal design suggests recovering waste heat at 35 °C with a heat pump and a 40-MWh storage, granting the highest coverage of residential needs (49%). On the other hand, the source-oriented optimal design suggests recovering waste heat at 85 °C without heat pump and with a 40-MWh storage, reaching the highest recovery of waste heat (55%). Exergy analysis supports the source-oriented design, as it reaches the highest global exergy efficiency (27%). Our prospective techno-economic and exergo-economic analyses should complement these results and may change some conclusions, especially regarding the storage capacity.

Thermal stability and material compatibility for hexamethyldisiloxane as the working fluids of organic Rankine cycle

The organic Rankine cycle (ORC) is one of the most suitable methods to generate electricity for renewable energy and industrial waste heat recovery systems. High temperature ORCs have recently attracted much interest because of the improved theoretical thermal efficiency. For high temperature ORCs, the working fluids need high critical temperature, low flammability and good thermal stability. Siloxanes are considered as the promising working fluids for high temperature ORCs in previous studies because of their high critical temperature, low flammability and environmental friendliness. The thermal stability and material compatibility of working fluid is the primary limitation for the working fluid selection at high temperatures. However, the results about thermal stability and material compatibility of siloxanes are scarce in previous studies. In this paper, the thermal stability and material compatibility of siloxanes were studied with hexamethyldisiloxane (MM) as a representative fluid. A test system and an experimental method were designed to identify the compositions of decomposition products. The masses of liquid samples were measured before and after tests to confirm the mass fractions of gaseous and liquid compositions in decomposition products. Liquid decomposition products, such as octamethyltrisiloxane (MDM) and tetramethylsilane, were found to be the main decomposition products of MM. The possible decomposition paths of MM were analyzed by the results of decomposition product composition analysis. The decomposition ratios of MM at 220, 240, 260, 280 and 300°C were measured after decomposition for 24 h. The decomposition could be detected at 240°C, which was lower than the critical temperature of MM. Thus, the thermal stability of MM should be emphasized for supercritical ORCs if the decomposition of MM is unacceptable in ORC systems. The air was confirmed to have big effects on MM decomposition and could change the reaction paths of MM decomposition. Thus, air dissolved in the liquid working fluid should be removed before filling the working fluid into ORC systems. The material compatibility of MM with metal samples was measured experimentally. 304 stainless steel and copper were chosen as test metal materials and the metal samples were processed into the shapes for the tensile experiments. The experimental temperature was 220°C, which was considered as a thermal stable temperature for MM. The material compatibility experimental periods in this study were 10 days, which were long enough in previous studies. The experimental results showed that the mass and hardness relative changes in both metal samples were very small and could be negligible. However, the tensile strength changes in the copper samples were obviously bigger than those in 304 stainless steel samples. Thus, 304 stainless steel has better compatibility with MM than copper as the metal material in systems at 220°C. The material compatibility of n-pentane with metal samples at 220°C was also measured using the same test system and method to be a comparison. The results showed that the tensile strength changes in metal samples with n-pentane were much bigger than those with MM. Thus, MM exhibited better compatibility with metal materials than n-pentane at 220°C as ORC working fluids.

A strategy for designing microencapsulated composite phase change thermal storage materials with tunable melting temperature

Thermal energy storage technology with high temperature phase change materials (PCMs) plays an increasingly important role in the concentrated solar power plants and industrial waste heat recovery systems. In this study, a novel displacement reaction between tetraethoxysilane as SiO2 source and molten raw Al powder was purposed to successfully prepare Al-Si/Al2O3 high temperature composite PCMs. Interestingly, by proposed synthetic methodology, we not only achieved the in-situ synthesis of Al-Si alloy PCM and Al2O3 shell, but also realized the controllability of Al-Si alloy composition and Al2O3 shell layer thickness. Our results indicated that the melting temperature of the prepared composite PCMs depended on the composition of Al-Si alloy, and could be designed within a certain temperature range (from 574.0 °C to 641.4 °C), instead of a particular temperature point. The melting temperature adjustability of the prepared composite PCMs provided an additional flexibility in different working temperature conditions. Moreover, the prepared composite PCMs exhibited a relatively high thermal storage capacity (248.6 J/g to 331.0 J/g), good thermal stability, excellent repeatable utilization property and certain shell layer self-repairing ability in the working temperature range. Therefore, the prepared composite PCMs can prove to be promising thermal energy storage materials for improving the energy efficiency in various systems under different working temperature conditions.

Computational modelling of an Organic Rankine Cycle (ORC) waste heat recovery system for an aircraft engine

Escalating fuel prices and carbon dioxide emission are causing new interest in methods to increase the thrust force of an aircraft engine with limitation of fuel consumption. One viable means is the conversion of exhaust engine waste heat to a more useful form of energy or to be used in the aircraft environmental system. A one-dimensional analysis method has been proposed for the organic Rankine cycle (ORC) waste heat recovery system for turbofan engine in this paper. The paper contains two main parts: validation of the numerical model and a performance prediction of turbofan engine integrated to an ORC system. The cycle is compared with industrial waste heat recovery system from Hangzhou Chinen Steam Turbine Power CO., Ltd. The results show that thrust specific fuel consumption (TSFC) of the turbofan engine reach lowest value at 0.91 lbm/lbf.h for 7000 lbf of thrust force. When the system installation weight is applied, the system results in a 2.0% reduction in fuel burn. Hence implementation of ORC system for waste heat recovery to an aircraft engine can bring a great potential to the aviation industry.

Thermal stability of some hydrofluorocarbons as supercritical ORCs working fluids

Organic Rankine Cycles (ORC) are used to generate electricity in renewable energy and industrial waste heat recovery systems. Supercritical ORCs have recently attracted much interest due to their higher thermal and exergy efficiencies. Hydrofluorocarbons are used as working fluids in subcritical ORCs and are also good choices for supercritical ORCs due to their good thermal performance. However, the thermal stability of the hydrofluorocarbons must be considered at high temperatures in supercritical ORCs. This study used the fluoride ion concentration to be the indicator of hydrofluorocarbon decomposition. A test system was designed and decomposition temperatures of HFC245fa, HFC152a, HFC134a, HFC236fa and HCFC123 were measured experimentally. The relationships between thermal stability and molecular structures of hydrofluorocarbons were then analyzed. The results show that these hydrofluorocarbons were good selections for supercritical ORCs by thermal stability. The hydrofluorocarbon decomposition characteristics and the effects of the decomposition products on the test system were also analyzed in this paper.

Enhanced specific heat capacity of binary chloride salt by dissolving magnesium for high-temperature thermal energy storage and transfer

Thermal energy storage and transfer technology has received significant attention with respect to concentrating solar power (CSP) and industrial waste heat recovery systems.

Energy Conservation Opportunities in Industrial Waste Heat Recovery Systems

ABSTRACT This article discusses waste heat recovery opportunities. Some of the opportunities are taken from energy audits and feasibility studies carried out in various plants located in Ontario, Canada. Opportunities discussed in the article include compressed air waste heat recovery, the application of a condensing economizer for heating boiler make-up water, waste heat recovery from coffee roasters, waste heat recovery from chemical reactor exhaust to preheat combustion air, steam boiler blowdown heat recovery, etc. The article also points out how some of the opportunities can be very attractive, depending on specific process and the existing system.

06/01055 Probabilistic aspects in the technical and economic analysis of the industrial waste heat recovery system generating useful heat and refrigeration: Koziol, J. and Banasiak, K. International Journal of Energy Research, 2005, 29, (6), 485–497.

06/01055 Probabilistic aspects in the technical and economic analysis of the industrial waste heat recovery system generating useful heat and refrigeration: Koziol, J. and Banasiak, K. International Journal of Energy Research, 2005, 29, (6), 485–497.

Probabilistic aspects in the technical and economic analysis of the industrial waste heat recovery system generating useful heat and refrigeration

The technical and economic analysis of the industrial waste heat recovery system, considering probabilistic distribution of the input data is presented. A prospect and rationality of the application of the waste heat boiler and absorption refrigerator has been examined as an example, in view of covering integrated heat and refrigeration demands. The influence of changing ambient conditions as well as the exhaust gas temperature and its flow rate on the overall system performance has been simulated and assessed. Copyright © 2005 John Wiley & Sons, Ltd.