Thermal Efficiency Of Process Research Articles

Optimization Design of Closed-Loop Thermosyphons: Experimentation and Computational Fluid Dynamics Modeling

The well-established practice of integrating heat pipes into thermosyphons is recognized for its efficacy in achieving energy savings. This integration facilitates heat transfer and fluid circulation without requiring additional pumps or energy input, resulting in reduced consumption, lowered operational costs, and an overall improvement in system efficiency. This research explores the energy-saving potential of closed-loop thermosyphons, with a specific focus on their integration in latent heat-based heat pipe technologies in industrial settings. The study systematically investigates the influence of thermosyphon orientation on energy efficiency through a combination of experiments and computational fluid dynamics (CFD) simulations. Thereby, it results in superior heat transfer rates in forced convection scenarios. A closed-loop thermosyphon heat exchanger undergoes evaluation in three panel installation configurations relative to the ground, taking into consideration factors including copper diameters, coolants (with or without R410a), and temperature conditions. CFD validation identifies an efficient thermosyphon design—a panel oriented perpendicularly to the ground and filled with R410a refrigerant at 90 °C. It utilizes a 19.05 mm copper tube for forced convection. This optimized design demonstrates a commendable heat transfer rate of 1485 W and a heat transfer coefficient of 1252 W/(m2·K), significantly enhancing thermal process efficiency and resulting in notable energy savings.

Energy and Exergy Analysis of Solar Air Gap Membrane Distillation System for Seawater Desalination

Air gap membrane distillation (AGMD) is a widely utilized technology for producing drinking water due to its low heat loss, high thermal efficiency, and compatibility with solar energy. The application of the first and second laws of thermodynamics in energy and exergy analyses provides a comprehensive evaluation of the efficiency of thermal processes. This study aims to examine numerically the energy and exergy performance indicators of a solar AGMD system used for seawater desalination. The simulation was carried out using MATLAB 9.7 software. The total thermal efficiency and overall efficiency of each element in the AGMD system were calculated for various solar field energy outputs, and moreover, a parametric study was conducted. The results indicate that the exergetic efficiency of the AGMD system components was the lowest in the solar field, with the concentrator having the lowest energy efficiency. Additionally, the thermal and exergetic efficiency of the entire solar AGMD system decreases along with the raise of ambient temperature. An additional investigation was conducted to better apprehend the sources of exergy destruction in the solar field. The obtained results from this study can be employed as a guide to reduce exergy destruction in the whole solar AGMD desalination system with recognition of the main sources of irreversibility.

Enhancement of Heat and Mass Transfer in the DCMD Process Using UV-Assisted 1-Hexene-Grafted PP Membranes.

The two main challenges for industrial application of membrane distillation (MD) are mitigation of temperature polarization and reduction of high-energy consumption. Despite the development of advanced materials and the configuration improvements of MD units, membrane surface modification is still one of the alternatives to overcome temperature polarization and improve membrane performance. This work reports a novel and simple method to modify the physical and chemical properties of the polypropylene membrane in order to improve its performance in direct contact membrane distillation (DCMD). The membrane was grafted by polymerization with 1-hexene, UV irradiation, and benzophenone as a photoinitiator. A grafting degree of up to 41% was obtained under UV irradiation for 4 h. The performance of the modified membrane in DCMD was evaluated at different temperatures and salt concentrations in the feed. First, it was found that there was an increase of the vapor permeate flux in the MD process within the range of tested temperatures and salt concentrations. The results were analyzed in terms of the physical properties of the membrane, the transport phenomena, and the thermal efficiency of the process. Theoretical analysis of the results indicated that grafting increased the transfer coefficients of mass and heat of the membrane. Hence, it improved the membrane performance and the thermal efficiency of the DCMD process.

Optimisation of a sorption-enhanced chemical looping steam methane reforming process

An intensified hydrogen production steam reforming process named ‘Sorption-Enhanced Chemical Looping Steam Methane Reforming’ (SE-CL-SMR) was studied. Aspen Plus was used to carry out a thermodynamic investigation into the influence of various operating conditions on hydrogen production and process thermal efficiency. The steam to carbon molar ratio (S/C), the CaO to carbon molar ratio (CaO/C), the metal oxide to carbon molar ratio (MeO/C), the metal oxide composition (NiO:CuO), and the oxidising agent species were all shown to influence the process performance.The main findings were that; (1) the introduction of CaO reduces the potential for coke formation with predicted zero coke formation for CaO/C ratios > 0.4; (2) increasing amounts of metal oxide (MeO/C) and steam (S/C) enhance the hydrogen production yield and purity; (3) due to its involvement in an exothermic reaction, the presence of CuO allows for the reforming reactor to operate as an adiabatic reactor with an operating temperature within the range of 600 °C–700 °C; (4) an increase in the NiO:CuO ratio leads to an increase in methane conversion.With the operating conditions of S/C = 3, CaO/C = 1, MeO/C = 1, NiO:CuO = 0.9 and air as the oxidising agent, a hydrogen purity as high as 98% was predicted for the SE-CL-SMR process, along with the lowest observed CO2 production rate. Under the same conditions and using pinch analysis, the thermodynamic model prediction of the thermal process efficiency is reported as ca. 86%. This is significantly higher than the reported efficiency of 79% for the ‘Sorption-Enhanced Steam Methane Reforming’ (SE-SMR) process, predicted using similar thermodynamic models.

A POINT OF VIEW ON THE PERCEPTION OF FUTURE PROFESSIONALS ON ENERGY EFFICIENCY OF REFIRGERATION SYSTEMS

In the modern times, energy efficiency is of high interest because there is direct link between this concept and energy conservation, economics, environment and sustainable development. The energy efficiency intensification at international level is closely follow by national leaders and worldwide governments and organisations and by top companies as well. Considering this obvious aspects, higher education institutions are deeply involved in involving energy efficiency in the curricula of future professionals, in order to allow them to gain skills that will help in solving challenges specific to this activity. In this international context, Constanta Maritime University introduced in the curricula of the students enrolled in the specialization called Engineering and Environment Protection in Industry a discipline dealing with this very important activity, named Thermal Efficiency of Buildings and Industrial Processes. This paper is investigating the manner in which our students have mastered the tools of energy efficiency assessment of refrigeration systems, throughout a questionnaire applied to them, at the end of the chapter dedicated to these technologies. The students had to write short comments to very specific questions. Analysis of the comments helps the lecturer and the students to take appropriate measures in the next future. Thus, the feedback resulted to be quite positive because most of the students gained the knowledge provided in this respect. Still, delicate concepts, such as entropy, exergy or exergy destruction seem to raise difficulties to some students. In this respect, results that such an intermediary assessment has to be repeated more often, for other kind of technologies discussed during this course, with the involvement of the concepts introduced by the second law- which are essential in energy efficiency assessments.

Improving Energy Efficiency of Thermal Processes in Healthcare Institutions: A Review on the Latest Sustainable Energy Management Strategies

Healthcare institutions consume large amounts of energy, ranking the second highest energy-intensive buildings in the commercial sector. Within developed countries, the energy consumption of healthcare institutions may account for up to 18% of the overall energy usage in commercial sectors. Within developing countries, such as South Africa, the energy consumption of healthcare institutions is observed to be a close second to the food service sector. Energy consumption of healthcare institutions per bed typically range from 43–92 kWh per day. In this paper, the largest energy consumers in South African healthcare institutions are identified and appropriate energy-efficiency (EE) initiatives are proposed, in terms of performance, operation, equipment and technology efficiency (POET). Two main thermal energy consumers are identified as heating, ventilation and air conditioning (HVAC) and water-heating systems. These systems are critical to patient health and may be classified as non-deferrable loads. Therefore, several initiatives are suggested to improve the energy efficiency and demand-side management capability of these systems. These initiatives are subdivided into different levels: the conceptual level, active level, technical and further improvement level, as defined in the POET framework. At each level, energy-efficiency initiatives are introduced based on potential energy savings and the effort required to achieve these savings. In addition, model predictive control (MPC) approaches are discussed and reviewed as part of the further improvement section. Average possible energy savings ranged from 50%–70% at the conceptual level, while energy savings of 15%–30% may be expected for energy-efficiency initiatives at the active level. EE activities at the technical level and the further improvement level may result in savings of 50%–70% and 5%–10%, respectively.

A Double Life of Freeze-Dried Enterococcus Faecium in Pet Food Industry

Freeze-dried <i>Enterococcus faecium</i> may able to lead a double life in pet food industry. Freeze-dried <i>Enterococcus faecium</i> can be identified both as a substitute for Salmonella in thermal processing validations and a special form of probiotics in formulations of pet foods. For the first life, freezedried <i>Enterococcus faecium</i> can be used as an indicator since its high thermal tolerance during processing, which is able to validate the inactivation efficiency of thermal processing in pet food industry, such as extrusion cooking.

Combustión sin llama como una alternativa para mejorar la eficiencia de sistemas térmicos: revisión del estado del arte

El aumento de la demanda energética, así como de las emisiones contaminantes ha generado un incremento de la investigación de tecnologías que permitan mitigar ambas problemáticas a nivel mundial. Dentro de las alternativas para mejorar la eficiencia de los procesos térmicos, el régimen de combustión sin llama se presenta como una de las alternativas más promisorias, puesto que permite obtener altos valores del rendimiento térmico mediante el mejoramiento de la transferencia de calor y del proceso de combustión, con la consiguiente reducción de las emisiones contaminantes. Debido a esto, en el presente estudio se realiza una revisión del estado del arte de dicha tecnología, haciendo énfasis en los aspectos fenomenológicos asociados, las principales características del régimen y su estabilidad, pasando por los mecanismos de obtención y la presentación de una serie de estudios, tanto a nivel nacional como internacional, en los que se utilizaron combustibles fósiles y alternativos. La revisión finaliza con la discusión de algunos casos en los cuales se ha implementado el régimen a nivel industrial.

The influence of steam injection for Enhanced Oil Recovery (EOR) on the quality of crude oil

ABSTRACTCurrently, due to reduction of oil reservoirs and the increasing need for oil as the main source for world energy, the need for production of heavy oil reservoirs is inevitable. The main purpose of this study is to determine the effectiveness of some operational and reservoir parameters and their impact on thermal and productive efficiency of thermal process of steam injection and quality of crude oil. In order to model the process, Eclipse-300 simulator was employed. Detection of these parameters, in addition to determining the best production scenario, can lead to the use of this method with better economic conditions. Hence, the results obtained from this study show that the optimal values obtained for operational parameters of stream injection such as steam quality, steam injection pressure, injection rate and well completion injection depth. The simulation results show that the use of optimal values of steam injection parameters can enhance efficiency of steam injection method and can make this method considered as third EOR method in heavy oil reservoirs than previously known in the petroleum industry.

Estimation of retorted phosphor powder from spent fluorescent lamps by thermal process

The degree of thermal stabilization of phosphor powder from spent fluorescent lamps (SFLs) manufactured by three companies (A, B, C) was estimated by examining mercury content in phosphor powder with retorting time, retorting temperature and rotational speed of drum. Mercury content of phosphor powders from spent fluorescent lamps manufactured by A, B and C companies as samples in thermal experiments was 4031mg/kg, 3522mg/kg and 3172mg/kg, respectively. In the thermal experiments, the optimal conditions for retorting time, retorting temperature, and rotational speed were determined at 6h, 400°C, and 2.0rpm, respectively. With thermal processing at the optimal conditions, mercury content of all samples for retorted phosphor powder was less than 3.0mg/kg, while efficiency of thermal process to control mercury content was higher than 99.9%. Leaching tests such as Toxicity Characteristic Leaching Procedure (TCLP) and Korea Extraction Test (KET) were subsequently carried out to verify if retorted phosphor powder is hazardous waste. Leaching concentrations of mercury for all samples of retorted phosphor powder were satisfied with regulatory levels in both leaching tests. Hence, retorted phosphor powders at the optimal conditions are considered to be non-hazardous wastes.

Adhesive Bonding of Oxide Ceramics for Complex Ceramic Parts in High Temperature Furnaces

Within the scope of the project ENERTHERM: Energy efficiency of thermal processes which is funded by the Bavarian Ministry of Economy (BMWi) components and systems for high-temperature are being developed. Monolithic oxide ceramics (mullite, Al2O3) and oxide-fiber reinforced ceramics (O-CMC) show a high potential for high temperature (HT) applications. Additionally, the demand for complex HT-components such as HT-fanwheels for kilns, supporting HT-lightweight structures or hot gas liners increases. In according to the required component design, joining techniques are needed in order to realize such complex geometries. The generated joints were made by using commercial glass solder from the type Al2O3-SiO2-MgO. For realizing the joining process sintering-joining in HT-kilns was used because of the homogeneous temperature distribution. A CO2 laser (wavelength of 10.6 microns and a power of 1.5 kW) was used for rapid joining process. The mechanical properties were determined in according to DIN EN 843-1 and DIN EN 658-3 (4-point bending strength) and evaluated according to Weibull distribution.

Process modelling and heat management of the solar hybrid sulfur cycle

Thermochemical cycles for water splitting are considered as a promising example of emission-free routes for large-scale hydrogen production – with potentially higher efficiencies and lower costs compared to low temperature electrolysis of water. The hybrid–sulfur cycle was chosen as one of the most promising cycles from the ‘sulfur family’ of processes. A process model has been established to study the main parameters influencing efficiency with specific attention paid to dynamic effects when coupled to solar heat. The process is separated into two sections – one at steady-state, and the other one fictively imposed by transients. This allows a first analysis with respect to reasonable energy and mass flow management, while considering concepts of coupling such a process to a concentrating solar system in a later step. Process efficiencies are calculated based on conservative assumptions, revealing the most important development tasks for the future. The extensive usage of recoverable high temperature heat – including the heat from the highly corrosive condensing phases – is a key factor to attain reasonable efficiencies for industrial application. With idealised heat recovery rates – limited by thermodynamic considerations, but excluding heat exchange between stationary and dynamic sections – and for decomposer temperatures appropriate for volumetric solar receiver operation, a thermal process efficiency close to 30% is predicted for stationary operation based on the lower heating value of hydrogen. Subsequent investigations will derive annual yields, taking into account the effect of coupling to solar energy.

The Use of hiTRAN Wire Matrix Elements to Improve the Thermal Efficiency of Tubular Heat Exchangers in Single and Two‐Phase Flow

AbstractOver the past decades, innovations in the design of heat exchangers have improved thermal process efficiency. hiTRAN wire matrix technology is applied on the tube side of tubular heat exchangers and has been successfully used in a wide range of application, ranging from sensible heating and cooling to condensing and boiling services. The technology is used for both new designs and in revamp situations where it can increase the effectiveness of existing equipment. This review gives the required information to determine the process conditions for the most efficient use of this technology.

Two-channel control system of thermal drying

The possibility of increasing the efficiency of thermal processes in rotary kilns by various technological and organizational solutions, the most important of which is the hierarchical principle of the thermal management system based on modern computing tools.

Molecular Physics of Elementary Processes Relevant to Hypersonics: Atom-Molecule, Molecule-Molecule and Atoms-Surface Processes

In the present chapter some prototype gas and gas-surface processes occurring within the hypersonic flow layer surrounding spacecrafts at planetary entry are discussed. The discussion is based on microscopic dynamical calculations of the detailed cross sections and rate coefficients performed using classical mechanics treatments for atoms, molecules and surfaces. Such treatment allows the evaluation of the efficiency of thermal processes (both at equilibrium and non equilibrium distributions) based on state-to-state and state specific calculations properly averaged over the population of the initial states. The dependence of the efficiency of the considered processes on the initial partitioning of energy among the various degrees of freedom is discussed.

Повышение тепловой эффективности процесса плазменного напыления

Повышение тепловой эффективности процесса плазменного напыления

Reducing environmental problems and increasing saving energy by proposing new configuration for moving bed thermally coupled reactors

In recent years, more stringent environmental regulations as well as higher needs to enhancement of thermal efficiency of process being imposed on the chemical processes for development of new procedures to supply requirements of industries. Nowadays, natural gas is an attractive contributor to the world's energy needs, but unfortunately the presence of sulfur components in natural gas contributes to the environmental side-effects. In order to remove sulfur components, a portion of the inlet hydrogen sulfide (H2S) oxidizes to the sulfur dioxide (SO2), while sulfur dioxide has destructive effects on the human health and on the environment. In this study, according to main aims of process integration and environmental regulations, a new configuration for oxidation of sulfur dioxide as an exothermic reaction in the thermally coupled reactor has been investigated. In order to utilizing the generated heat in oxidization reaction, this reaction has been coupled with naphtha reforming process as an endothermic one. The mathematical modeling of process is accomplished in two dimensions (radial and axial). Then, the modeling results of thermally coupled reactor (TCR) are compared with the obtained results of conventional one.

The effect of melt viscosity on thermal efficiency for single screw extrusion of HDPE

In this work, a highly instrumented single screw extruder has been used to study the effect of polymer rheology on the thermal efficiency of the extrusion process. Three different molecular weight grades of high density polyethylene (HDPE) were extruded at a range of conditions. Three geometries of extruder screws were used at several set temperatures and screw rotation speeds. The extruder was equipped with real-time quantification of energy consumption; thermal dynamics of the process were examined using thermocouple grid sensors at the entrance to the die. Results showed that polymer rheology had a significant effect on process energy consumption and thermal homogeneity of the melt. Highest specific energy consumption and poorest homogeneity was observed for the highest viscosity grade of HDPE. Extruder screw geometry, set extrusion temperature and screw rotation speed were also found to have a direct effect on energy consumption and melt consistency. In particular, specific energy consumption was lower using a barrier flighted screw compared to single flighted screws at the same set conditions. These results highlight the complex nature of extrusion thermal dynamics and provide evidence that rheological properties of the polymer can significantly influence the thermal efficiency of the process.

Study of Fluid Flow and Heat Transfer Through Mini-Channel Heat Sink

Mini/Micro-channel type compact heat exchangers have attracted much attention during the last decade. The reason is mainly the possibilities of reducing the size, weight and cost of the heat exchangers compared to current designs. Also, new applications, where objects of small size need to be cooled, as electronics and micro-electro-mechanical devices, require heat exchangers with miniature channels. For the application of mini channel heat exchangers, it is necessary to have accurate design tools for predicting heat transfer and pressure drop. The present paper aims to set up an experimental set-up to study the fluid flow and single phase heat transfer through mini-channel heat sink. The present set-up add to the knowledge of the fundamentals of single phase heat transfer and pressure drop in narrow channels, thereby aiding in the development of this new, interesting technology with the possibility of decreasing the size of electronics through better cooling, and of increasing the energy efficiency of thermal processes and thermodynamic cycles through enhanced heat transfer.

CO2–steam mixture for direct and indirect gasification of rice straw in a downdraft gasifier: Laboratory-scale experiments and performance prediction

This paper explored the feasibility of CO2 as alternative gasifying agent of steam to obtain higher thermal efficiency in biomass gasification. The effect of the gasifying agent on gas evolution and thermal efficiency was examined by using a lab scale downdraft gasifier. The results were also compared with the output of pyrolysis with N2. The reaction atmosphere in indirect and direct gasification was simulated by carrying out the experiments without and with O2 presence. The reaction conditions were varied in the temperature range from 750°C to 950°C by changing the CO2 molar fraction in gasifying agent to the ratio of 0, 30 and 60vol.% in balance with steam. 40vol.% of N2 fraction was kept during O2 free experiments, while 31.7vol.% of N2 and 8.3vol.% O2 were kept during the experiments with the presence of O2. At all examined condition, gasification yielded more combustible gas than pyrolysis. Furthermore, high CO2 fraction in gasifying agent generally resulted in low H2 yield and high CO yield. These substitutions mostly lowered the energy yield of the producer gas, but in the other hand also reduced the preheating energy of gasifying agent. Thus, optimizations of these changes were investigated for gaining highest thermal efficiency of the gasification process. Highest thermal efficiency of the process without O2 was 52% under N2 (40vol.%)–CO2 (60vol.%) atmosphere at the temperature of 850°C. For the process with O2, where the part of gasifying agent preheating energy supplied by the biomass partial combustion, the highest thermal efficiency was 60% under the CO2 (60vol.%)–O2 (8.3vol.%)–N2 (31.7vol.%) atmosphere at the temperature of 950°C. CO2 utilization as a gasifying agent potentially increases the thermal efficiency of biomass conversion process compared with pyrolysis or conventional indirect and direct gasification, i.e. pure-steam gasification and O2–steam gasification.