Recovery Heat Exchanger Research Articles

Heat Transfer Characteristics of Heat Exchangers for Waste Heat Recovery from a Billet Casting Process

The application of the thermoelectric generator (TEG) system to various industrial facilities has been explored to reduce greenhouse gas emissions and improve the efficiency of such industrial facilities. In this study, numerical analysis was conducted according to the types and geometry of heat exchangers and manufacture process conditions to recover waste heat from a billet casting process using the TEG system. The total heat absorption increased by up to 10.0% depending on the geometry of the heat exchanger. Under natural convection conditions, the total heat absorption increased by up to 45.5%. As the minimum temperature increased, the effective area increased by five times. When a copper heat exchanger of direct conduction type was used, the difference between the maximum and minimum temperatures was significantly reduced compared to when a stainless steel heat exchanger was used. This confirmed that the copper heat exchanger is more favorable for securing a uniform heat exchanger temperature. A prototype TEG system, including a thermosyphon heat exchanger, was installed and a maximum power of 8.0 W and power density of 740 W/m2 was achieved at a hot side temperature of 130 °C. The results suggest the possibility of recovering waste heat from billet casting processes.

Proposal of a thermally-driven air compressor for waste heat recovery

The industrial sector accounts for one third of the global energy use, mainly due to the energy-intensive industries. Waste heat recovery plays a major role among the advances that can lead to potential savings in these industries. The present work proposes an air compressor that generates industrial compressed air in a novel manner only by recovering heat from exhaust gases, not by consuming electric power, and employing readily available technologies transferred from other sectors. The proposed system is an externally-heated open-loop Brayton cycle operating with air in which a fraction of the compressed air from the compressor is delivered as product, while the remainder is heated up and processed in the expander. In its turn, the expander drives only the compressor and not also an electric generator as in conventional cycles. The system is simply realized combining a single- or a two-stage turbocharger from marine reciprocating engines and a recovery heat exchanger. In single-stage, it can deliver compressed air at a pressure up to 500 kPa, while in two-stage over 1000 kPa. Here, the two-stage configuration is applied to a container glass manufacturing plant and simulated accurately with the code Aspen Plus and Aspen EDR. This work demonstrates that the system could be realized with proven technology from other industrial sectors. It indicates also that 2342 m3/h of compressed air at 800 kPa can be produced from the exhaust gas at 12,000 m3/h (referred to 0 °C and 101.325 kPa) and 560 °C. The performance is affected strongly by the ambient air condition and the furnace load with variations of the compressed air rate ranging from −92% up to +52% in the extreme conditions. The intercooling power is typically around just 35% of the waste heat recovery and, in any case, always lower than 50%. The gross and net equivalent electric efficiencies are in the range 12–16% and 10–14%, respectively, similarly to conventional heat recovery power plants of same size. The performance can be further improved by employing the hot air from the expander as preheated combustion air or for cogeneration. Ultimately, with respect to conventional plants, the system is a simpler technology operating with a harmless fluid, requiring a lower cooling power and a smaller footprint.

Підвищення ефективності комбінованих теплоутилізаційних систем газоспоживальних котельних установок

Викладено результати досліджень ефективності використання в теплоутилізаційних технологіях газоспоживальних опалювальних котелень удосконалених комбінованих систем утилізації теплоти, призначених для нагрівання води систем теплопостачання та хімічного водоочищення і повітря на горіння. Дослідження виконано для водогрійного котла ТВГ-8 за різних режимів його роботи згідно з тепловим графіком котельні залежно від температури навколишнього середовища в опалювальний період. Визначено в розглянутих умовах для відповідних теплообмінників-теплоутилізаторів такі основні параметри, як: теплопродуктивність, приріст коефіцієнта використання теплоти палива КВТП котла та кількість утвореного в системі конденсату за нормованих значень витрати води на підживлення теплових мереж. За отриманими основними показниками проведено порівняльний аналіз пропонованих систем теплоутилізації та відомих комбінованих систем з нагріванням тільки зворотної тепломережної води та дуттьового повітря. Показано, що доповнення відомої системи додатковим теплообмінником, призначеним для попереднього нагрівання холодної води на хімводоочищення (ХВО), дає змогу шляхом глибшого охолодження вихідних газів котельної установки підвищити її КВТП максимально на 9,4 %, що на 0,5 % більше порівняно з відсутністю нагрівання води на ХВО.

Numerical optimization of obstructed high temperature heat exchanger for recovery from the flue gases by considering ash fouling characteristics

PurposeThe purpose of this paper is to recommend a validated numerical model for simulation the flue gases heat recovery recuperators. Due to fulfill of this demand, the influences of ash fouling characteristics during the transient/steady-state simulation and optimization of a 3D complex heat exchanger equipped with inner plain fins and side plate fins are studied.Design/methodology/approachFor the particle dispersion modeling, the discrete phase model is applied and the flow field has been solved using SIMPLE algorithm.FindingsAccording to obtained results, for the recuperator equipped with combine inner plain and side plate fins, determination of ash fouling characteristics is really important, effective and determinative. It is clear that by underestimating the ash fouling characteristics, the achieved results are wrong and different with reality.Originality/valueFinally, the configuration with inner plain fins with characteristics of: di =5 mm, do = 6 mm, dg = 2 mm, dk = 3 mm and NIPFT = 9 and side plate fins with characteristics of: TF = 3 mm, PF = 19 mm, NSPF = 17·2 = 34, WF = 10 mm, HF = 25 mm, LF = 24 mm and ß = 0° is introduced as the optimum model with the best performance among all studied configurations.

A novel electrical charging condensing heat exchanger for efficient particle emission reduction in small wood boilers

Small-scale biomass combustion is an important source of fine particles in ambient air, causing adverse health and environmental effects. Thus, there is a clear need to develop efficient and feasible flue gas cleaning technologies for small-scale combustion appliances. In this study a novel electrical charging condensing heat exchanger (eCHX) for combined fine particle removal and efficient heat recovery from flue gases was demonstrated in a small biomass-fired boiler. The method is based on the combination of a shielded corona charger and a condensing heat exchanger, where fine particles are removed by the electrophoretic, thermophoretic and diffusiophoretic forces. The eCHX was found to decrease >80% of fine particle mass (PM1) emissions and >40% of particle number emissions with simultaneous high thermal efficiency in the heat exchanger. The usage of the condensing heat exchanger without electrical charging resulted in 40% decrease in PM1 emissions when compared to the usage of a traditional tube heat exchanger. The advantage of the eCHX system is that it replaces the conventional heat exchanger in boilers, making it a compact and inexpensive solution, when compared to additional flue gas cleaning devices installed after the boiler.

Development of heat exchanger for heat recovery of process gases

Due to new requirements of the Russian laws on the environment and energy efficiency, studies on effective methods for recovering waste heat from flue gases are crucial. Most oil and gas, metallurgy and chemical manufacturers remove high-temperature process gases. Gas cooling preceding cleaning reduces a volume of cleaned gases. For example, the most efficient dust and gas cleaning systems usually operate at a gas temperature of up to 200 °C. An increase in gas temperature can cause irreversible deformations of metal structures of the gas cleaning equipment and its premature failure. In addition, bag filters used for gas cleaning have strict limitations on gas temperature. As a part of the present project, an optimal design of staggered heat exchange elements in the form of perforated copper ribs was developed. The design documentation was developed and an experimental heat exchanger was designed. To monitor and control heat exchanger parameters, sensors were installed on the experimental heat exchanger (EHE). The algorithms of the automated system were developed. Laboratory and pilot tests proved the efficiency of the equipment designed for cooling waste process gases. The heat exchanger can be installed in gas flues of various diameters. The number of cooling units depends on technical requirements and operating and installation conditions.

Exergy cost accounting and thermoeconomic diagnosis for Double-Solar-Gas-Turbine system (DSGT)

ABSTRACT The selection of the cost-effective design for energy systems is one of the important issues in the design and optimization of the power generation systems. To achieve this goal, the thermodynamic analysis and fault detection is one of the useful methods. Thus, in this paper, the thermoeconomic diagnosis and fault detection method is used for the selection of effective Double-Solar-Gas-Turbine system (DSGT). In the proposed DSGT system, the heliostat solar system and combustion of fossil fuel are used as a heat source of the power plant. To achieve the research goals, in the first steps, the energy and exergy analysis is performed, and the energy and exergy parameter is evaluated. Then, the thermoeconomic and the exergy cost accounting analysis is performed and based on this analysis; the exergy cost parameters are examined for all the components and flows. Finally, the malfunction of each component is evaluated with the thermoeconomic diagnosis approach and based on this approach, the effects of irreversibility in each component on other components are investigated. Results show that one of the heat exchangers (intercooler in the bottom cycle) has the highest exergetic cost in comparison to other components, but this heat exchanger has a very small impact on the irreversibility of other components. Conversely, the heat recovery heat exchanger (recovery between the two cycles) has a major effect on the irreversibility of other components, and thus the most correction should be performed in this converter.

Theoretical thermal analysis of heat recovery by two phase closed Thermosyphon from engine exhaust

Due to the increase in energy requirements for various process industries and depletion of fossil fuel reservoirs, it is necessary to recover the heat energy which is exhausted to the environment from different sources. Effective utilization and recovery of waste heat is of great importance for the preservation of energy sources and protection of an environment and health hazards. For many industrial practices because of high effectiveness the application of Thermosyphon is increasing for the recovery of waste heat. The focus of the present study is to investigate theoretically the performance parameters (thermal and geometrical) of the Single tube wickless heat pipe heat exchanger (Thermosyphon) for heat recovery at simulated diesel engine exhaust conditions (Air temperature of ~150, 250 and 350 °C and under forced convective heating and cooling at different Reynolds number). From the theoretical analysis it was observed that effectiveness of Thermosyphon was over 50% for each of the conditions and it was increased up to 88% with decreasing inlet hot air velocity down to 1 m/s at temperature of 350 °C. It was also observed that at equal heat capacity rate of hot and cold fluids the effectiveness is minimum.

Investigating energy saving potential in a big shopping center through ventilation control

This paper investigates energy saving measures for the ventilation system of large shopping centers. This kind of buildings is characterized by high yearly energy consumptions, because of the high level of operating hours and the frequent use of obsolete technologies. In the analyzed case studies, three big Do It Yourself (DIY) shops, located in Italy, are considered. Two different approaches are considered, they are aimed at reducing the annual energy consumption for the indoor air exchange of the sales area. The first considered retrofit solution consists in the installation of heat recovery exchangers, reducing the energy demand for the air thermal treatment without changing the airflow value. In the second scenario, smart air quality sensors are inputs for the modulation of the air exchange rate according to the actual requirement for indoor air quality. In a third scenario, the application of both retrofit solutions is considered. For each scenario, the paper reports the yearly energy savings, the avoided CO2 emissions and cost saving indicators. Furthermore, as the three shops are equipped with different heating systems and are located in different parts of Italy, a technological and climatic comparison is provided.

Design of a high-temperature heat to power conversion facility for testing supercritical CO2 equipment and packaged power units

This paper addresses the need of bridging between fundamental energy research and industrial exploitation of technologies by presenting a state of the art experimental facility to investigate pilot heat exchangers and plants dealing with high temperature waste heat recovery and conversion. The facility comprises a 830 kW process air heater with an exhaust mass flow rate of 1.0 kg/s at 70 mbarg and maximum temperature of 780 °C. The heater has a 2.0 m long test section for the installation and characterization of waste heat recovery heat exchangers. The heat sink is a 500 kW water dry cooler with full control of flow rate and temperature of the cooling stream. The high-temperature heat to power conversion facility hosts a 50 kWe power conversion unit based on the simple recuperated Joule-Brayton cycle with supercritical CO2 (sCO2) as working fluid. The packaged, plug and play sCO2 system utilizes a single-shaft Compressor-Generator-Turbine unit. The paper discusses the main design features of the test facility as well as operation and safety considerations.

Heat integration and heat recovery steam cycle optimization for a low-carbon lignite/biomass-to-jet fuel demonstration project

This paper reports the heat integration study for a demonstration plant to co-process lignite and woody biomass into jet fuel with CO2 capture and storage. Since all the main process reactions are exothermic and convert approximately 65% of the feedstock chemical energy into heat, designing an efficient heat recovery steam cycle and heat exchanger network is essential for the overall thermo-economic performance. Different integration options for the plant’s heat recovery steam cycle are analyzed and compared, considering costs and the key technical limitations. The design of the heat recovery steam cycle and heat exchanger network is optimized with an energy targeting methodology, a sequential synthesis method and a recently proposed simultaneous methodology. Given the high specific costs of the units caused by the novelty and small size and of the demonstration plant, the techno-economic optimization returns solutions with considerably lower efficiency (up to −5% percentage points) and power output (up to −18%) compared to the energy targeting methodology. The difference in optimal HRSC designs and performance are minor (less than −2% power output) for full-scale plants based on mature technologies.

Membrane heat exchanger for novel heat recovery in carbon capture

In this work, we experimentally demonstrate a commercial ceramic membrane heat exchanger (CMHE) with an average pore size of 4 nm for novel heat recovery in post-combustion carbon capture. The CMHE shows superior performance over a conventional stainless steel heat exchanger (SSHE) with the same dimensions in recovering heat from the stripped gas mixture (H2O(g)/CO2) on top of the stripper in a monoethanolamine-based rich-split carbon capture process. Due to the coupled mass and heat transfers of water vapor through the membrane, the CMHE has higher heat flux, heat recovery and overall heat transfer coefficient than the SSHE. Liquid water transfer dominates the mass transfer mechanism in the CMHE. Thermal conduction contributes to more than 80% of the total heat transfer, dominating the heat transfer through the membrane heat exchanger. Our study demonstrates that membrane heat exchangers can be excellent candidates for heat recovery in post-combustion carbon capture. In further research, more types of membranes with higher thermal conductivities (e.g., porous metal membranes with lower porosity and smaller thickness) should be fabricated and tested for further performance enhancement.

Compact potential of exhaust heat exchangers for engine waste heat recovery using metal foams

Compact potential of exhaust heat exchangers for engine waste heat recovery using metal foams

Comparative study of two novel micro-CCHP systems based on organic Rankine cycle and Kalina cycle

With regard to the significant role of combined cooling, heating, and power (CCHP) systems in performance enhancement of power plants, two novel micro-CCHP systems are presented which are based on organic Rankine cycle (ORC) and Kalina cycle (KC) as topping cycles. Additionally, ejector refrigeration cycle (ERC) and vapor compression heat pump cycle (VCHPC) are utilized as the bottoming cycle of the power systems. To demonstrate feasibility of the recommended micro-CCHP systems, an exhaustive thermodynamic modeling and exergoeconomic analysis are employed as the most effective tools for performance evaluation of the systems. Also, to get better performance of the systems, single- and multi-criteria optimizations are carried out, using genetic algorithm. It is figured out that the KC-based micro-CCHP system has higher optimum thermal efficiency and total sum unit cost of the product (SUCP) than the ORC-based micro-CCHP system, while it had lower exergy efficiency. Regarding that, the optimum thermal efficiency for the ORC- and KC-based micro-CCHP systems are computed by 76.54% and 77.32%, respectively, whilst the optimum exergy efficiency for the ORC- and KC-based micro-CCHP systems are calculated by 48.37% and 31.2%, respectively. In addition, generator had the major exergy destruction rate among all components for both systems. Furthermore, the results of parametric study proved that higher thermal (energy) efficiency can be computed with increasing the heat source temperature, heater temperature, evaporation temperature, and terminal temperature difference of the recovery heat exchangers.

Investigation of a single room ventilation heat recovery exchanger under frosting conditions: Modeling, experimental validation and operating strategies evaluation

This paper tackles the issue of frost formation in air-to-air heat recovery devices dedicated to single room ventilation by means of both numerical simulations and experimental approaches. In such heat exchangers, it is commonly known that the formation of a frost layer on the surface generates an additional thermal resistance and a flow section reduction, which leads to an overall degradation of the overall unit performance. This paper proposes a three-zone model, considering a dry, a wet and a frost zone, by determining the location of moving boundaries. Each zone is handled independently and the relative proportion of each zone is determined by means of the exchanger wall temperature. Besides this frost model, a defrost model is also envisaged. Once validated with experimental data collected on a U-flow-type heat exchanger, the developed model is used to implement different strategies to reduce or prevent frost formation in the exchanger. Based on three different criteria, these strategies are compared with each other to evaluate their benefits and drawbacks. The criteria give information on the energy efficiency of the ventilation, on the air renewal quality and on the pressure balance between the inside and the outside of the building.

Operation characteristics of air–air heat pipe inserted plate heat exchanger for heat recovery

The heat pipe inserted plate (HPIP) type air–air heat exchanger was developed to recover energy from the exhaust air. The heat pipe was inserted through the waved plates, and the two streams with temperature difference flowing opposite along both sides of the plate. The prototype HPIP heat exchanger charging the different refrigerant in the heat pipes was analyzed experimentally, and the influences of the indoor and outdoor temperature difference and the type of refrigerant in the loop heat pipes on the temperature effectiveness, heat transfer rate, and energy efficiency ratio (EER) of the prototype were investigated. Results showed that the heat transfer rate and EER of the heat exchanger increased with the increase of indoor and outdoor temperature difference in winter and summer conditions. The maximum temperature effectiveness reached 62% in winter conditions and 70% in summer conditions. When the loop heat pipes working medium was R32, the heat exchange performance of the heat exchanger in winter and summer conditions was improved. The analysis and calculation of the average annual EER of the heat exchanger while running in Harbin, Beijing, Shanghai, and Guangzhou (China) were 12.72, 7.70, 5.75, and 3.67, respectively.

Experimental Studies on Performance Parameters of Finned Tube Heat Exchanger for Waste Heat Recovery.

The demand for energy is rising significantly due to growth of nations. The use of diesel engines for the purpose of transportation is increasing because of their high efficiency and robustness. Around 30% of the input energy is carried by the engine exhaust gas, which in turn reduces thermal efficiency and increases environmental pollution. With an objective of waste heat recovery and reduction in pollution due to engine exhaust, this work focuses on the theoretical and experimental analysis of performance parameters of continuous plate fin-tube heat exchanger for waste heat recovery at simulated engine conditions. From the experimental data it was observed that fin tube heat exchanger is one of the best heat exchangers for recovery of waste heat at lower fluid flow rates and higher inlet temperatures. The heat recovered is calculated to be 110W, 60W and 52W at hot gas flow rates of 150, 170 and 190LPM respectively.

Effect on louver dampers configuration on gas maldistribution in a heat exchanger for waste heat recovery

This paper reports the results of visualization research involving a heat exchanger applied for waste heat recovery using of Digital Particle Image Velocimetry (DPIV) method. Five louver dampers configurations responsible for typical operation modes were tested. As a consequence, airflow maldistribution in the tube bundle section and bypass section were identified and described. Based on the measurements and analysis carried out, the authors have developed a way to implement design changes to optimize gas distribution inside the unit.

Thermodynamic and thermoeconomic analysis of basic and modified power generation systems fueled by biogas

Biogas has been used practically as an attractive renewable energy source for various combined power plants as a recent advancement in technologies. Feasibility investigation of a modified organic Rankine cycle coupled with a gas turbine cycle fueled by biogas (60% methane +40% carbon dioxide) as a heat source is carried out in this study. Thermodynamic and thermoeconomic analysis are employed as the most powerful tools to estimate performance and cost of the system and the results are compared with the basis coupled system. Also, to investigate how the proposed systems perform under any external disturbances, a thorough sensitivity study around the basic operating input parameters was carried out. The results of the second law analysis demonstrated that among all components and for both proposed systems, the combustion chamber had the highest value of exergy destruction rate, followed by the recovery heat exchanger. The proposed combined system could produce net output electricity of 1368 kW, resulting in the thermal efficiency, exergy efficiency and overall product cost of 41.83%, 38.91%, and 17.2 $/GJ, respectively. Moreover, it is found that the thermal and exergy efficiencies of both systems could be maximized with respect to the air compressor pressure ratio and steam turbine inlet pressure, while the overall product cost of the cycles can be minimized with air compressor pressure ratio and gas turbine inlet temperature.

Domestic thermoelectric cogeneration drying system: Thermal modeling and case study

The demand for reducing fuel consumption and mitigating exhaust fumes accountable for the greenhouse effect push toward developing efficient energy recovery systems. Optimizing the heat recovery process can be achieved by adding multi-recovery stages. In this frame, the present work suggests a new multi-stage recovery system for heating water and air and generating electricity. The concept of the system is applied to the exhaust gases of a chimney. A complete thermal modeling of the system is drawn. Then a case study is carried out for three different fed fuels (diesel, coal, wood). The results show that when diesel is used water temperature achieved 351 K and 240 W electric power is generated. Moreover, a 0.16 m2 heat recovery heat exchanger area is required to heat air to 363 K at an air flow rate of 0.0076 kg/s. Such system can recover up to 84% of the energy lost to the environment when wood is utilized as a fed fuel.