Gas Heat Research Articles

Multiple thermoelectric cogeneration system in an industrial thermal peeling press machine – Thermal modeling, case studies, and parametric analysis

Cogeneration systems, exploiting waste heat sources, have emerged as crucial solutions in decreasing energy consumption and mitigating CO2 emissions across diverse industrial domains. This study delves into the innovative integration of multiple waste heat recovery (MWHR) mechanisms with thermoelectric generators (TEGs) within industrial contexts, with a specific emphasis on harnessing exhaust gas heat. Through meticulous investigation, six distinct configurations of TEG placement covering three unique systems were examined to expose their influence on overall system efficacy. Findings clarify a deep correlation between TEG positioning and system performance, with TEGs strategically positioned in close to heat sources, particularly along the inner walls of exhaust pipes, demonstrating the most auspicious outcomes in terms of power generation. Furthermore, the study reveals notable metrics, including a maximum power efficiency of 0.11 W per TEG and a water heat flow rate peaking at 5114 W. However, a comprehensive analysis underscores the imperative for interpreting the primary mechanisms governing TEG placement's impact on system performance, alongside defining the practical implications of the observed power efficiency and water heat flow rate. These empirical insights underscore the transformative potential of WHR-TEG interactions in optimizing energy utilization within industrial ecosystems, highlighting the request for further research actions aimed at implementation strategies and sustainability benchmarks.

Thermodynamic analysis of power generation thermal management system for heat and cold exergy utilization from liquid hydrogen-fueled turbojet engine

Hydrogen propulsion is generally treated as the ultimate net zero-emission option for aviation, therein liquid hydrogen storage appears to provide the only feasible solution for aircraft with the constraints imposed by aircraft weight and volume. Hydrogen liquefaction consumes a great amount of energy, which significantly boosts the cost of hydrogen as an aviation fuel. Besides the H2 chemical exergy for combustion to provide thrust, the H2 physical exergy in the form of cold energy is also a kind of high-quality clean energy to produce power output, which offers great opportunities to achieve cost-effective use of hydrogen fuel. Thus, this paper presents a Rankine cycle and H2 direct expansion cycle (RC-DEC) combined power generation thermal management system for the simultaneous utilization of exhaust gas heat exergy and hydrogen fuel cold exergy from the liquid hydrogen-fueled turbojet engine. In the Rankine cycle, the transcritical mode is applied on the hot side while the liquid separation condensation concept is adopted on the cold side to achieve better thermal matchings with heat and cold sources. The hydrocarbon/inert gas binary mixture is proposed as the working fluid of the Rankine cycle. The effects of key thermodynamic parameters and the influence of Para-Ortho hydrogen conversion on system performance are discussed, then a comparison of the mixture working fluid is conducted. Results show that there exists an optimal separation temperature ratio and condensation pressure of RC to obtain maximum total net power output. As the DEC expander inlet pressure increases, the total net power output first increases and then levels off. The introduction of the Para-Ortho hydrogen conversion has a negligible impact on net power output but leads to a significant reduction in the exergy efficiency, which is attributed to the cold energy release nature of Para-Ortho hydrogen conversion. The results of the working fluid comparison indicate that the optimal inert gas retardant for CH4 is Kr, while those for C2H6 and C3H8 are Xe to achieve the maximum net power output and exergy efficiency of the proposed power generation system. Among them, C2H6/Xe(0.6/0.4) obtains the maximum net power output of 2717.9 kW and maximum exergy efficiency of 33.1%, which suggests an opportunity to provide megawatts of electrical power for the aircraft in place of the APU.

Multi-Indicator Assessment of a Thermal Insulation Investment, Taking into Account the Pre-Set Temperature

The article proposes indicators to evaluate a thermal insulation investment in a building, such as net present value (NPV), profitability index, discounted payback period, and ecological cost efficiency. Economic and ecological aspects were taken into account. Life Cycle Assessment (LCA) was used in the ecological analysis. The following heat sources in the building were considered: condensing gas boiler and heat pump. The developed indicators also depend on the pre-set temperature in residential premises. A methodology to determine the optimum thermal insulation thickness for both economic and ecological reasons was also proposed. A case study was analyzed, and a reference building, typical for Polish construction conditions, was used for research. Various solutions were suggested regarding the type of thermal insulation material and heat sources. The values of the indicators were determined for the proposed variants and for the economically and ecologically optimum thermal insulation thicknesses. Based on the conducted research, it was found that air temperatures maintained in the rooms of the building undergoing thermal modernization should be taken into account in the energy audit. The energy demand of the building for a room temperature of 26 °C is higher by 61% compared to the demand for the same building at the design temperature (20 °C). The innovation in the proposed approach to the economic and ecological assessment of a building is the combination of a wide range of temperatures potentially maintained in living spaces with ecological cost-effectiveness.

Role of proton exchange membrane fuel cell in efficiency improvement of ammonia–hydrogen fusion zero-carbon powertrains for long-haul, heavy-duty transportation

Ammonia fuel, a transport zero-carbon energy carrier with a much lower life-cycle greenhouse gas footprint than existing fuels and the ability to overcome the storage and transportation challenges of hydrogen fuel, is an effective means of realizing the energy transition for long-haul, heavy-duty transportation such as heavy trucks. Although the efficient use of liquid ammonia fuel cannot be realized directly at this stage, it can be realized indirectly by converting ammonia fuel into hydrogen and combining the hydrogen generated with ammonia in an ammonia–hydrogen fusion fuel supply method. In this study, we assess four ammonia–hydrogen fusion-fueled zero-carbon powertrains for heavy-duty commercial vehicles, each of which is designed to determine its most efficient green zero-carbon fuel utilization scenario at the point of steady state operation as well as over the entire power-demand interval. It was found that the required engine capacity decreases with the increase of the hydrogen energy ratio in the ammonia–hydrogen composite fuel. Considering the indicated thermal efficiency of the engine and the combustion stability in the cylinder, the ammonia–hydrogen composite fuel with 30% hydrogen energy share was selected for the matching design of the powertrains. The study results show that powertrain equipped with engine and fuel cell are more energy efficient than others. The powertrain with range extender consisting of the engine and fuel cell takes ammonia dissociation separation unit and fuel cell as an important part of engine exhaust gas heat recovery, which reduces the dependence of ammonia cracking hydrogen production on electric heating power. By regulating the energy distribution ratio between the engine and the fuel cell, the system can be maintained at a high level of energy efficiency. Under different power requirements of highway application scenarios, the system efficiency is not less than 36%, and the system energy utilization efficiency is higher than 44%. Compared to engine direct drive powertrain, engine range-extended powertrain, and fuel cell range-extended powertrain, the average system efficiency increases by 30.8%, 8.68%, and 14.24%, while the average system energy utilization increased by 41.12%, 25.26%, and 39.43%, respectively.

Fire detection and suppression in rooms with different geometries

The paper presents experimental research findings on the integral characteristics of physicochemical processes in the area around a fire at different stages of its development and suppression. The purpose of this study was to determine the characteristics of the operation of fire detectors in rooms of various geometries. The temperatures in different cross sections, as well as the composition of gaseo us products of thermal decomposition and flame combustion of materials were investigated. The study dealt with class A fires involving wood. Mock-ups of rooms with distinctly different geometries were used: a parallelepiped, a rectangular truncated pyramid and a bow-roof (arched) structure. Efficient arrangement of technical equipment (light and gas analysis sensors, heat and smoke detectors, nozzles) was determined to provide early detection of a fire, prompt initiation of suppression and completion of combustion and smoldering. Minimum volumes of a firefighting liquid (water in this case) and spraying times were identified that are necessary and sufficient to suppress combustion. Guidelines were proposed on the arrangement of technical equipment for early fire detection and efficient containment of fire in the shortest time. A mathematical apparatus has been developed that allows predicting the performance of fire detectors and sensors. The research results can be used to evaluate the most effective locations for fire sensors in the design of buildings and structures.

A novel designation of LNG solid oxide fuel cells combined system for marine application

This paper presents a pioneering multigeneration system for marine vessel applications, involving the integration of solid oxide fuel cells (SOFCs) fueled by liquefied natural gas (LNG), coupled with LNG cold energy utilization cycles and exhaust gas heat recovery systems. The system comprises a tandem arrangement of organic Rankine cycle (ORC) and trans-critical carbon dioxide cycle (TCO2), specifically engineered to harness the cold energy released during LNG regasification process. The elevated temperature exhaust gases emanating from the SOFC are efficiently recuperated through a series of components including a gas turbine (GT), regenerative, steam Rankine cycle (SRC), and waste heat boiler (WHB). The proton exchange membrane fuel cells (PEMFC) is designed to enhance the overall operational flexibility and responsiveness of the multigeneration system. The Aspen Hysys V12.1 is used to simulate the propose system and numerical method is employed to parameter optimize of system. The first and second laws of thermodynamics are applied to establish the thermodynamics equations and calculated the system performances. The described system is estimated to obtain energy efficiency of 69.32 % and exergy efficiency of 33.85 %. The high-temperature exhaust gas harvesting integrated systems are sufficiently generated 2091.24 kW which accounted 35.49 % of entire power generate. Furthermore, the parametric researches are implemented to examine the influence of current density, β values to the performance indicators of systems. The WHB is designed to generate 1081 kg/h of superheated vapor at 170 °C and 405 kPa for various purposes of seafarers and equipment's onboard ship. The economic feasibility is performed to view the possibility of investment, maintenance cost and payback period for the described system.

Research on screening strategy of Organic Rankine Cycle working fluids based on quantum chemistry

The screening of working fluids is one of the key components in the study of power generation systems utilizing low-temperature waste heat. However, the variety of working fluids and their complex composition increase the difficulty of screening working fluids. In this study, a screening strategy for working fluids was developed from the perspective of the thermodynamic physical properties of working fluids. A comparative ideal gas heat capacity via the reduced ideal gas heat capacity factor (RCF) was proposed to characterize the dry and wet properties of working fluids, where RCF > 1 indicated a dry working fluid and RCF < 1 indicated a wet working fluid. A three-step screening strategy was developed for working fluid screening for organic Rankine cycles (ORCs). The strategy comprised basic physical property analysis of working fluids, research on dry and wet properties, and quantum chemical analysis. By comparing the RCF calculation result of 23 selected working fluid with values from the literature, the relative deviations of the data were less than 6.64% overall, indicating that the calculation result of the RCFs is reliable. The selection strategy explains the mechanism of working fluid selection in ORC systems from both micro- and macro-perspectives, laying a foundation for the study of structure-activity relationships in working fluids for ORCs.

Dimensioning Method for PVT Collectors as Heat Source of Heat Pumps for Residential Buildings

Photovoltaic-thermal (PVT) collectors are an emerging technology that is increasingly being used as a heat source for heat pump systems in residential buildings. However, a suitable standard methodology for sizing the PVT collectors for these systems is still not available. This paper initially provides a framework for the sizing of a PVT-heat pump system for small houses according to the German guideline VDI 4645. The dimensioning method of VDI 4645 and the sizing method for PVT collectors are incorporated in a web-based tool that is aimed to assist planners (or homeowners) during the preliminary planning of a heat pump system in single and multi-family houses. The methodology also covers the planning of systems with backup/additional heaters (e.g. gas boiler and heating rod), e.g. for buildings with limited roof areas for PVT installations. Different heat pump operation modes, i.e. monovalent, bivalent-alternative, or bivalent-parallel are also considered. A model of the IEA SHC Task44 SFH100, an existing single-family house with radiators, has been chosen as an example case to demonstrate the methodology. For the evaluation of the performance of the designed system, yearly simulations of the system are done in TRNSYS. The results show that the developed methodology provides plausible sizes for the example case. However, further development and validation are necessary to provide flexibility in system dimensioning.

Modelling physical controls on mine water heat storage systems

The use of abandoned mines as a heat source and store has been receiving increased attention as a renewable heat source and storage solution in the transition away from traditional gas heating. The hydraulic, thermal and geomechanical processes governing heat storage and extraction are complex and understanding these processes is critical to safe heat extraction and injection into mine water systems. This paper outlines the development of a fully coupled thermo-hydraulic-mechanical (THM) 2D model to understand the mechanical stability of room and pillar workings during heat injection and extraction. It was found that the cyclical injection and extraction of heat does have an impact on both the modelled displacements and mechanical stability of the system. The impact risk reduces with temperature and the operational processes (e.g. injection temperature and water level) have more of an impact than the underlying geological conditions. These results are significant and could be included in a regulatory system to reduce the likelihood of stability impacts in mine water heating and cooling schemes. Thematic collection: This article is part of The Earth as a thermal battery: future directions in subsurface thermal energy storage systems collection available at: https://www.lyellcollection.org/topic/collections/thermal-energy

Identification of primary input parameters affecting evacuation in ventilated main control room through CFAST simulations and application of a machine learning algorithm to replace CFAST model

Accurately predicting evacuation time in a ventilated main control room (MCR) during fire emergencies is crucial for ensuring the safety of personnel at nuclear power plants. This study proposes to use neural networks alongside consolidated fire and smoke transport (CFAST) simulations to serve as a surrogate model for physics-based simulation tools. Our neural networks can promptly predict the evacuation time in MCRs, proving to be a valuable asset in fire emergencies and eliminating the need for time-consuming rollouts of the CFAST simulations. The CFAST model simulates fire and evacuation scenarios in a ventilated MCR with variations in input parameters such as door conditions, ventilation flow rate, leakage area, and fire propagation time. Target output parameters, such as hot gas layer temperature (HGLT), heat flux (HF), and optical density (OD), are used alongside standardized evacuation variables to train a machine learning model for predicting evacuation time. The findings suggest that high ventilation flow rates help to dilute smoke and discharge hot gas, leading to lower target output parameters and quicker evacuation. Standardized evacuation variables exceed the required abandonment criteria for all door conditions, indicating the importance of proper evacuation procedures. The results show that neural networks can generate evacuation times close to those obtained from CFAST simulations.

An empirical study on thermal efficiency and dusty moisture removal efficiency using enthalpy wheel in industrial waste incineration plant

In this work, an empirical study is conducted on the waste heat recovery and moisture removal performance of an enthalpy wheel installed in an industrial waste incineration plant. The enthalpy wheel made of a metal mesh is placed in parallel with the wet scrubber of the incineration plant to exchange heat with high-temperature exhaust at 200 °C. In the enthalpy wheel, exhaust gas and external air exchange heat in the form of a counter flow, and the condensation effect is maximized by installing a water-spray nozzle at the inlet of the enthalpy wheel. Empirical data were collected over 100 days spanning July to October. To evaluate the performance of the enthalpy wheel, thermal efficiency, moisture removal efficiency, and dust removal efficiency were tested under high-temperature humid conditions. In some results, the overall thermal efficiency reached peaked at 61.2 %. Regarding moisture removal performance, the average moisture removal rate was 493 kg/h, affording an efficiency of 49.2 %. In terms of dust removal performance, the average dust removal efficiency was 79.6 %.

Experimental Investigation on Solution Regeneration Performance and Coefficients in Full-Open System for Heat and Water Recovery of Flue Gas

Experimental Investigation on Solution Regeneration Performance and Coefficients in Full-Open System for Heat and Water Recovery of Flue Gas

Prenatal risk factors of indoor environment and incidence of childhood eczema in the Japan Environment and Children's Study

The quality of indoor environment is a risk factor for early childhood eczema and atopic dermatitis; however, its influence during pregnancy on childhood eczema in Japan has not been investigated. In this study, we aimed to determine the indoor environmental factors that are associated with eczema in children up to 3 years of age, using national birth cohort data from the Japan Environment and Children's Study (JECS).Information on indoor environments and eczema symptoms until 3 years of age was collected using self-administered questionnaires to the mothers. A total of 71,883 and 58,639 mother-child pairs at 1.5- and 3-years-old, respectively, were included in the former analyses. To account for prenatal indoor risk factors, 17,568 (1.5-years-old) and 7063 (3-years-old) children without indoor mold and/or ETS exposure were included in the final analysis. A higher mold index, gas heater use, parquet flooring use, and frequent insecticide use showed significantly increased risks for childhood eczema up to 3 years of age. These associations were consistent after stratification analysis among children whose parents did not have a history of allergies. The updated WHO guidelines on indoor air quality should be implemented based on recent findings regarding the effects of prenatal exposure to indoor dampness on health effects of children further in life, including asthma, respiratory effects, eczema, and other immunological effects.

High-Precision 3D reconstruction and quantitative structure description: Linking microstructure to macroscopic heat transfer of aerogels

The intricate interplay between microstructure and macroscopic transfer processes in porous materials has long been recognized, yet achieving a definitive link between them remains a formidable challenge. Herein, we propose an effective approach to address this challenge by introducing a high-precision 3D reconstruction and structure descriptor database analysis method of nanoporous aerogels, which enables deeper understanding and accurate predictions of structure-directed properties. By employing focused ion beam-scanning electron microscope (FIB-SEM) technique supplemented with image preprocessing and image segmentation, we successfully built a 3D reconstruction model that exhibits high consistency with experimental results. Then, a structure descriptor database from the view of original porous structure, structure connectivity, and topological information is established, and 10 descriptors are preliminarily filtered relevance with thermal conductivity. Consequently, the quantitative relationship between descriptor and thermal conductivity is evaluated via a back propagation (BP) neural network, and three categories structure descriptors which have the most significant impact are determined as (i) the description of gaseous heat transfer pathways, (ii) the description of three-dimensional connectivity, and (iii) the description of interface complexity. With the profound understanding of structure descriptor, the present work offers a novel, structure-focused strategy that closely link the microstructure to macroscopic properties of porous materials.

A Study of the Merging Dwarf Galaxy VCC322

Galaxy interactions and mergers can enhance or reduce star formation, but a complete understanding of the involved processes is still lacking. The effect of dwarf galaxy mergers is even less clear than their massive counterpart. We present a study on a dwarf merger remnant in the Virgo cluster, VCC322, which might form a triple system with VCC334 and VCC319. We identify a prominent long and straight tail-like substructure that has a size comparable to its host galaxy VCC322. By comparing the color–color (g − r versus r − H) distribution with simple stellar population models, we infer that the metallicity and stellar age of this tail are Z ⋆ ∼ 0.02 Z ⊙ and t ⋆ ∼ 10 Gyr, respectively. In VCC319, we find a sign of isophotal twisting. This suggests that VCC319 may be subject to tidal interaction. An analysis of the Sloan Digital Sky Survey optical spectra of VCC322 indicates mass- and light-weighted ages of about 109.8 yr and 107.5 yr, respectively, indicating an ongoing star formation activity. However, the star formation in VCC322 seems suppressed when compared to other star-forming dwarfs of comparable stellar masses. Our finding of shock excitation of optical emission lines indicates that interaction-induced shock may contribute to the heating of cold gas and suppression of star formation.

Optimal operation of multiple energy system considering load management approach and uncertainty

In recent years, the advancement of technology has led to the development of energy networks' infrastructure, resulting in the transformation of conventional networks into smart networks. By incorporating communication equipment, each component of the network can now exchange information with other components, creating an environment where innovative ideas can be implemented. One such idea is the utilization of multi-carrier energy systems, also known as Energy Hubs. Integrating energy hubs into traditional networks used to be a challenging task. However, with the expansion and enhancement of smart networks, the potential for incorporating and locating energy hubs within the power grid has significantly increased. In these systems, the focus shifts from optimizing a single energy carrier to ensuring the optimal operation of a system that encompasses multiple energy carriers, such as natural gas, electric grid, and thermal energy. Energy hubs act as intermediaries between energy supply companies and various consumers, including residential, commercial, and industrial sectors. These energy suppliers can encompass different energy networks, such as electricity, gas, and local heating. The integration of residential and commercial energy hubs has become a crucial aspect of modern energy systems, particularly in the context of load response applications. This paper proposes a novel approach for effectively utilizing residential and commercial energy hubs, taking into account the time of use (ToU) load response program. In the proposed system, the inherent uncertainties of the system are addressed using the two-point estimation method of the model. To achieve the desired objective, the Cuckoo optimization algorithm, a well-established meta-heuristic algorithm for solving optimization problems, is employed. This algorithm aids in determining the optimal scheduling of energy resources while considering ToU tariffs and load management plan signals. The results demonstrate that the proposed approach can significantly reduce energy costs for the energy system.

A comprehensive multi-variable approach for evaluating the feasibility of integration a novel heat recovery model into a gas turbine power plant, producing electricity, heat, and methanol

Considering the importance of efficient thermal integration for a gas turbine cycle using its energetic flue gas, the current paper proposes an eco-friendly and efficient process integrated into a gas turbine cycle. The newly designed polygeneration structure produces power, hot water, and methanol. The components of this system include a heat provider unit, a direct carbon dioxide hydrogenation unit for the production of methanol, an ammonia Rankine cycle, a proton exchange membrane electrolyzer, a supercritical carbon dioxide power cycle, and two organic Rankine cycles. The feasibility of the proposed model is evaluated using a comprehensive multi-variable assessment from energy, exergy, economic, and environmental approaches. This system exhibits a power production capacity of 17197.23 kW and a methanol generation rate of 0.7573 kg/s. Also, the total irreversibility is equal to 68161.18 kW. Besides, the total energy and exergy efficiencies are found as 68.73% and 32.03%, respectively. This model's carbon dioxide emission is 18667.36 kgCO2/h, and its carbon footprint equals 0.2196 kgCO2/kWh. Furthermore, the economic analysis reveals that the project has an annual total cost of 194,602,338 and a net present value of 686,221,616. Besides, the computed total unit costs for products and energy are 0.3385 $/kWh and 89.81 $/GJ, respectively.

Development of an iot-based humidity, temperature, and air quality monitoring system

Monitoring the environment has become of great importance as it helps individuals keep tabs on their environment. Air pollution is very dangerous to human health and it is known to cause deadly health conditions. This research presents an IoT-based design that will effectively monitor the humidity, temperature, and air quality of a given environment. NodeMCU humidity, temperature, and gas sensors were deployed in the design of the system. The output interface was designed using the Blynk IoT platform. The system was tested in two stages using application of gas pollutants and heat on one hand, whilereadings were taken from a cool evening and sunny afternoon on the other hand. After testing all the functions of the system under various conditions, it revealed 76% humidity, 26.8oC temperature, and 461ppm on the application of gaseous air pollutants, 43.1% humidity, 45.6OC temperature, and 199ppm of air quality on the application of heat, 51.1 humidity, 20.4% temperature, 198ppm of air quality on a cool evening and 70.7% humidity, 29.5OC of temperature and 206ppm of air quality on a sunny afternoon. The system showed improved performance in terms of monitoring of humidity, temperature and air quality and can be deployed suitably in homes, schools, and industries.

Performance evaluation of cathode channels with different cross-sections for open-cathode polymer electrolyte membrane fuel cell stack

This study proposes six different cross-sectional cathode flow field designs such as square, trapezoid, dome, boot, pentagon, and triangular constructing four cells open cathode polymer electrolyte membrane fuel cell stack with various parameters optimization and suitability for system level development. Parameters, including pressure drop, oxygen concentration, airflow rate, blower power, stack temperature, cooling rates, net power output, and stability are investigated with focus on understanding the trend, interconnected dependencies among the parameters, which collectively influence the overall performance of the cross-section designs. Overall, studies show that, boot cross-section design possessing the optimum pressure drop of 23.9 Pa, shows better performance compared to other cross-section designs due to better oxygen gas distribution, water retention/removal, heat removal/retention, and net power output. Conversely, for galvanostatic analysis done at a higher current value of 35 A, dome and square cross-section designs show highest and stable potential, along with balanced stack temperature.

Analysis of preferences of households for choosing heating and cooling systems: A discrete choice analysis in Iran

The residential sector uses a large fraction of energy for heating and cooling to provide comfort conditions for households. Technical features of appliances are determining factors of the demand for energy. The present paper thus aims to study the determinants of household adoption decision by applying the discrete choice model. Households face with unordered choice, and multinomial and mixed logit models are employed to study the heterogeneity of choices of households related to heating and cooling technologies. While most of the research works have considered preferences based on cross-sectional data collected through discrete choice experiments, the present study employs micro-level household survey data including observed preferences in order to contribute to better understanding of the actual choice behavior of households. In addition, the dynamic effect of variation of variables on the household preferences have been investigated over time. The results show that heterogenous preferences of families in choosing appliances are affected by socio-demographic characteristics. Analysis of marginal effects indicate that urbanization, education, building type and households expenditure are the most effective parameters. The level of education has the most positive impact on the adoption of wall-mounted package and split air conditioner where the probability of using them has increased by 1.65% and 4.87%, respectively. On the other hand, high education level reduces the probability of gas heater and fan adoption by 3.49% and 3.43%. The estimated results show that urbanization increases the probability of choosing central heating by 3.73% and split air conditioner by 6.1% while it decreases the adoption probability of oil heater by 5.02% and fan as by 8.9%.