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The effects of compression ratio and injection timing on a direct injection spark ignition hydrogen engine under various excessive air ratios were analyzed using a 0.4-L single-cylinder engine in this study. The engine speed was set to 1500 rpm, and the excessive air ratio was changed by controlling the amount of injected hydrogen under wide-open throttle conditions. The compression ratio was changed from 10, 12, and 14 and the injection timing was varied from BTDC 200, 160, 120°CA. The results revealed that for a compression ratio 14 at a rich limit, late injection timing reduced knocking incidence by taking advantage of stratified mixtures combustion and increased indicated thermal efficiency by reducing combustion loss while producing lower NOx emissions. For compression ratio 14 at an excessive air ratio of 2.2, late injection timing increased indicated thermal efficiency by reducing both combustion and heat losses, achieving the higher indicated thermal efficiency of 42.3%. Although NOx emissions increased with the injection timing retardation, NOx emissions decreased to under 1 g/kWh under excessive air ratios above 2.5 conditions at all injection timings. [ABSTRACT FROM AUTHOR]

Considering environmental challenges and the diminishing share of energy expenses in the final product cost, evaluating energy‐intensive systems is crucial. This study examines the drying process of wet glass containers in a honey processing plant using a continuous convection dryer through energy and exergy analyses. Mass, energy, and exergy balances were performed using EES software. The energetic performance indicators revealed a heat loss rate of 3.33 kW, energy efficiency of 20.45%, and specific energy consumption of 11711.25 kJ kg‐1H₂O. Exergetic performance indicators included an exergy destruction rate of 24.05 kW, improvement potential rate of 20.79 kW, total exergy efficiency of 14.14%, exergy efficiency of 11.14%, specific exergy consumption of 2763.92 kJ kg‐1H₂O, and a sustainability index of 1.16. Results indicated that 60.12% of exergy destruction is related to air heating, with exhaust air losing 200.54 kW, equivalent to 89.84% of total input energy, suggesting exhaust air recirculation to reduce losses. Practical applications: The wet container dryer in a honey processing plant, as the most energy‐intensive component, was chosen for thermodynamic analysis. Mass, energy, and exergy balances were conducted to evaluate the system's thermodynamic performance. The exhaust air dryer lost 200.54 kW, equivalent to 89.84% of the total input energy, without utilization. Additionally, the results showed that 60.12% of the total exergy destruction in the convective drying process was related to air heating. Therefore, recirculating the exhaust air from the dryer moves the system toward an ideal thermodynamic state. [ABSTRACT FROM AUTHOR]

The problem of reducing primary energy consumption is increasingly discussed in the technical literature. Relatively large amounts of energy are used to heat rooms. In the case of resources of much cheaper waste energy or energy from renewable sources with a temperature lower than required in the rooms, the so-called "thermal barrier" placed in external walls can be used to reduce heat transmission losses. The thermal barrier is a vertical wall element with pipes with a heating medium installed in the partition, with a temperature lower than the temperature in the room but higher than that resulting from the heat transfer through the partition without a barrier. An analytical calculation of heat flow through a thermal barrier has not been encountered in the literature. Therefore, a methodology for thermal barrier calculations was developed. In the paper, the heat fluxes flowing from the room to the partition and from the partition to the outside are determined. The developed model of partition with thermal barrier is then presented and the formula for thermal barrier efficiency is derived. Based mainly on theoretical models for the assumed input values and the partition's surroundings it was found that the efficiency of the thermal barrier does not depend on the temperatures of the barrier base and the wall environment, but only on the geometrical and thermodynamic parameters of the partition. It has also been shown that the efficiency of the thermal barrier is the highest when the resistance of the partition on both sides of the barrier is the same. It should be noted that the total amount of heat given off by a wall with a thermal barrier is greater than through a wall without a barrier, but the costs of heating the room may be lower. [ABSTRACT FROM AUTHOR]

Propagation of combustion front with effect to the external heat loss is studied by the two-dimensional discrete periodic and disorder systems. Discrete periodic systems are modeled by the regular arrangement of burnt and unburnt point heat sources characterized by the identical rate of heat release and different heat loss parameter. Discrete disorder systems, namely, S1, S2 and S3 are considered with the concatenation of regular burnt and unburnt point heat sources distributed by different shaping parameter of beta distribution function. The unburnt point heat sources in a discrete disorder system are characterized by the different heat loss parameter and incorporation of two categories of distributions for the rate of heat release namely (i) gamma (a = 20) and (ii) gamma (a = 2). The oscillations in ignition time delay, with the manifestation of bifurcation pattern, have been detected for discrete periodic systems. In a discrete disorder system, the external heat loss plays a crucial role in developing the fingering instabilities and determining the early onset of unstable combustion, quenching and combustion limit. Degree of randomness in the distribution of heat release for the disorder system affects the duration of combustion, burn rate without affecting the combustion limit. Computed values of burn rate and combustion limit from the discrete combustion model have been compared with the available data from experiment. [ABSTRACT FROM AUTHOR]

The problem of reducing primary energy consumption is increasingly discussed in the technical literature. Relatively large amounts of energy are used to heat rooms. In the case of resources of much cheaper waste energy or energy from renewable sources with a temperature lower than required in the rooms, the so-called "thermal barrier" placed in external walls can be used to reduce heat transmission losses. The thermal barrier is a vertical wall element with pipes with a heating medium installed in the partition, with a temperature lower than the temperature in the room but higher than that resulting from the heat transfer through the partition without a barrier. In the paper, on the basis of the developed model of a partition with the thermal barrier, for the assumed input values and the partition's surroundings, the efficiency of the thermal barrier was defined and determined. A formula for its efficiency was derived. The efficiency of the thermal barrier does not depend on the temperatures of the barrier base and the wall environment, but only on the geometrical and thermodynamic parameters of the partition. It has also been shown that the efficiency of the thermal barrier is the highest when the resistance of the partition on both sides of the barrier is the same. Knowledge of the barrier efficiency will allow to easily determine the average barrier temperature and the amount of heat given off by the room and by the heating medium flowing in the barrier. It should be noted that the total amount of heat given off by a wall with a thermal barrier is greater than through a wall without a barrier, but the costs of heating the room may be lower.

This article focuses on the thermal bridging issues associated with interface of parkade concrete suspended slab to base of wall. The study aims to determine the optimal length and thickness of insulation at the top and underside of the suspended slab to minimize heat loss. The thermal performance of wall to parkade suspended slab is investigated, for both wood frame and steel stud constructions. Various insulation configurations are proposed and evaluated, including different lengths and thicknesses of extruded polystyrene foam (XPS) and Fiberglass spray insulations. The thermal performance calculations are conducted using steady-state heat transfer analysis. A finite-element based software is utilized for the simulations. The study provides a detailed methodology for analyzing the thermal performance of building envelope details, considering different insulation configurations. The results of the simulations are presented as Thermal Resistance Values (R-Values) and Linear Thermal Resistance Values (PSI-Values), allowing for a comparison of the thermal efficiency of different insulation configurations. The results show that utilizing the optimal insulation configuration can lead to up to 80 % enhancement in the thermal efficiency of the assembly. The findings serve as a guideline and aim to assist building designers in improving the thermal performance of concrete suspended slabs.

This article focuses on the thermal bridging issues associated with interface of parkade concrete suspended slab to base of wall. The study aims to determine the optimal length and thickness of insulation at the top and underside of the suspended slab to minimize heat loss. The thermal performance of wall to parkade suspended slab is investigated, for both wood frame and steel stud constructions. Various insulation configurations are proposed and evaluated, including different lengths and thicknesses of extruded polystyrene foam (XPS) and Fiberglass spray insulations. The thermal performance calculations are conducted using steady-state heat transfer analysis. A finiteelement based software is utilized for the simulations. The study provides a detailed methodology for analyzing the thermal performance of building envelope details, considering different insulation configurations. The results of the simulations are presented as Thermal Resistance Values (R-Values) and Linear Thermal Resistance Values (PSI-Values), allowing for a comparison of the thermal efficiency of different insulation configurations. The results show that utilizing the optimal insulation configuration can lead to up to 80 % enhancement in the thermal efficiency of the assembly. The findings serve as a guideline and aim to assist building designers in improving the thermal performance of concrete suspended slabs. [ABSTRACT FROM AUTHOR]

Solar air heaters (SAHs) are widely used for drying vegetables and fruits or for domestic heating. Certain sizing parameters are necessary to obtain the right dimensions for the required air temperature, flow rate, and thus useful thermal energy. The well‐known Hottel–Whillier–Bliss equation was used and made dimensionless by applying the collector longitudinal and transversal aspect ratios (rl and rt) of a double‐glazed flat plate solar air heater (DG‐FPSAH). The steady‐state equations are solved to determine the average temperatures. Thereafter, one could calculate the overall loss heat coefficient and efficiency factor, obtained analytically. A Matlab code was developed to estimate primarily unknown temperatures, useful energy, and the Nusselt number. An iterative numerical method is used until convergence occurs. The inlet cross‐sectional area and air flow velocity are defined as input data. The proposed sizing method depends on the output temperature required by the customer. This temperature can be determined from the plotted curves of the dimensionless ratios. Hence, the SAH‐needed dimensions are determined graphically depending on the functional requirements for construction planning, such as technology choice, work breakdown, and budgeting. In the present case study, based on the input parameters, an airflow rate of 1.2 kg/s entering a DG‐FPSAH with an output temperature of 41.5°C yields the dimensions of Lin = 3.824 m, Win = 2.735 m, and Hin = 0.1825, specifying the collector length, width, and air duct height. The gathered energy and thermohydraulic efficiency are: Qu = 7.91 kW, ηcol = 0.752, respectively. [ABSTRACT FROM AUTHOR]

This study developed a one-step chemical reaction model for hydrogen combustion and investigated the effect of heat loss on premixed hydrogen/air deflagration in closed pipelines using numerical simulations with the CFD code GASFLOW-MPI. The simulation results were compared and verified with experimental data. The numerical simulations accurately predicted the flame front structure, pressure, and flame tip position during the deflagration of premixed hydrogen/air. Furthermore, a comparison of adiabatic simulation and heat transfer simulation results revealed that large-scale vortices within the turbulent flow were closely linked to heat loss during the tulip flame stage. Simultaneously, heat loss reduced pressure and flame tip position by diminishing the flame wrinkling factor caused by thermodiffusive instability. Finally, convective heat transfer identified as the most critical factor contributing to heat loss during the deflagration of premixed hydrogen/air in closed pipelines. Specifically, during the tulip flame stage, heat loss was mainly due to convective heat transfer (73.8%∼76.3%), with radiation playing a minor role (23.7%∼26.2%). Therefore, accurate prediction of characteristic parameters during the deflagration of premixed hydrogen/air requires numerical simulations that account for both convective and radiative heat transfer. • Heat transfer simulation can better predict the evolution of hydrogen deflagration. • Heat loss can cause a reduction in pressure and flame tip position. • Large-scale vortices within the turbulent flow are closely linked to heat loss. • Thermodiffusive instability is closely related to heat loss. • Convection heat transfer plays a crucial role in the heat loss. [ABSTRACT FROM AUTHOR]

During air injection into an oil reservoir, an oxidation reaction generates some heat to raise the reservoir temperature. When the reservoir temperature reaches an ignition temperature, spontaneous ignition occurs. There is a time delay from the injection to ignition. There are mixed results regarding the feasibility of spontaneous ignition in real-field projects and in laboratory experiments. No analytical model is available in the literature to estimate the oxidation time required to reach spontaneous ignition with heat loss. This paper discusses the feasibility of spontaneous ignition from theoretical points and experimental and field project observations. An analytical model considering heat loss is proposed. Analytical models with and without heat loss investigate the factors that affect spontaneous ignition. Based on the discussion and investigations, we find that it is more difficult for spontaneous ignition to occur in laboratory experiments than in oil reservoirs; spontaneous ignition is strongly affected by the initial reservoir temperature, oil activity, and heat loss; spontaneous ignition is only possible when the initial reservoir temperature is high, the oil oxidation rate is high, and the heat loss is low. [ABSTRACT FROM AUTHOR]

This study examines the impact of thermal insulation on thermal comfort and energy consumption in an existing house that did not comply with building regulations. Thermal insulation included adding layers of polystyrene in the ceiling and floor, the areas with the highest heat gain and loss. After renovation, findings demonstrated a 55% reduction in heating energy required for winter. Reduction in air conditioning power was 18% during the summer. Simulations using the DesignBuilder software for the house revealed a 42% and a 17% reduction in the energy needed for heating and cooling. TRNSYS software simulation indicated a 500 kWh average annual energy consumption reduction. Experimental results measurements in two days of summer proved that the indoor temperatures of the house did not exceed 25.1°C and remained stable regardless of changes in external temperatures. Thermal insulation is a promising solution for reducing energy consumption and achieving thermal comfort in buildings. [ABSTRACT FROM AUTHOR]

Trombe wall serves as an effective passive heating element, and its performance is heavily reliant on local climate conditions. This study involved both experimental and numerical analyses of a full‐scale test room equipped with a Trombe wall under Iraqi climate conditions. To facilitate this investigation, an experimental test room was constructed in Kirkuk city with dimensions of 4.0 m × 3.0 m × 2.75 m. In addition, a numerical simulation method based on computational fluid dynamics was developed and a computer code was created to investigate the performance of the system. The accuracy of the developed numerical approach was validated against experimental data collected from the test room. This analysis was conducted specifically for the period of February 17–18, which represents the coldest month of winter in the study area. The performance of the system was assessed with respect to various parameters; air gap width variations (2, 4, 6, and 10 cm), massive wall thickness ranging from 15 to 35 cm with 5 cm increments, channel width options (3, 5, 10, 15, and 20 cm), and vent heights ranging from 5 to 20 cm in 5 cm increments. Furthermore, an investigation of the impact of replacing the air in the air gap with inert gases, specifically argon, krypton, and a mixture of these gases with air was conducted, as well. The outcomes indicate that both the channel width and vent height do not have a significant impact on the system's performance. However, the width of the air gap has a modest effect on system performance, and the best performance was observed with a smaller gap width, specifically 2 cm. The most significant impact on room temperature is observed when the storage wall thickness is varied. In the case of wall thickness of 15 cm, there is a notably higher fluctuation in room temperature between the maximum and minimum values, reaching approximately 16°C. For a wall thickness of 35 cm, however, this fluctuation is significantly reduced to about 3°C. The system efficiency as determined after 24 h of operation period improved significantly when the air was replaced by an inert gases or a mixture of gases in the air gap. Compared to air, the increase in efficiency is about 14.8% for argon, 17.7% for krypton, and 20.6% for the mixture of gases. [ABSTRACT FROM AUTHOR]

To compare changes in oesophageal (T-Oeso) and rectal (T-Rec) temperature in dogs during general anaesthesia and premedicated with fentanyl, medetomidine–fentanyl or acepromazine–fentanyl. Prospective, randomized, blind clinical study. A total of 120 healthy dogs, aged 2–10 years and weighing 5–20 kg. Dogs were randomly allocated to one of three groups. Animals of F group were premedicated with fentanyl (0.01 mg kg–1), MF group with medetomidine (0.005 mg kg–1) and fentanyl (0.01 mg kg–1) and AF group with acepromazine (0.01 mg kg–1) and fentanyl (0.01 mg kg–1). Anaesthesia was induced with propofol and maintained with isoflurane in oxygen–air mixture. Fentanyl was administered continuously (0.01 mg kg–1 hour–1). The T-Oeso, T-Rec and ambient temperatures were recorded after induction (T0) and subsequently at 10 minute intervals for 60 minutes (T10–T60). Data were analysed using anova or their non-parametric equivalents (p < 0.05). Median T-Oeso was significantly higher in MF group between T0–T20 compared with other groups. Median T-Oeso significantly decreased in F group from 38.0 °C (T0) to 37.4 °C (T30), 37.1 °C (T40), 36.9 °C (T50) and 36.6 °C (T60), in MF group from 38.3 °C (T0) to 37.7 °C (T30), 37.5 °C (T40), 37.2 °C (T50) and 37.1 °C (T60) and in AF group from 37.7 °C (T0) to 37.3 °C (T40), 37.2 °C (T50) and 37.1 °C (T60). The T-Rec significantly decreased in F group from 38.0 °C (T0) to 37.4 °C (T40), 37.2 °C (T50) and 36.9 °C (T60), in MF group from 38.3 °C (T0) to 37.5 °C (T50) and 37.4 °C (T60) and in AF group from 38.2 °C (T0) to 37.6 °C (T40), 37.5 °C (T50) and 37.4 °C (T60). Premedication with fentanyl, medetomidine–fentanyl or acepromazine–fentanyl in the doses used decreased the T-Oeso and T-Rec. The T-Oeso at the beginning of anaesthesia was higher after premedication with medetomidine–fentanyl. However, this difference was not clinically significant. [ABSTRACT FROM AUTHOR]

Humans produce different rates of sweating depending on the intensity level of a given activity. The clothing worn during the activity has a significant effect on the latent heat loss that can occur before, during, and after the activity. The water adsorption and spreading properties of a material yield differences in the amount of heat exchange that can occur between the person and the environment. Current test methods evaluate this using a value known as evaporative resistance, which is used to determine the heat exchange potential of a material. However, this value is only taken once the material has reached "steady state" and does not consider the sweating period before steady state is reached, or the drying period after steady state is reached. Therefore, an area under the curve (AUC) value was derived during these periods to compare the heat exchange properties of different materials. A sweating guarded hot plate was used to simulate different sweat rates, and therefore activity levels, to compare materials constructed of cotton, viscose, polyester, and wool. The overall latent heat loss of the hydrophobic wool was much less compared to the other samples with a gentler slope and lower AUC values than the other samples. It was found that the segment of time analyzed has a significant impact on the conclusion drawn about the latent heat loss of a material, p < 0.0001. Sweat rate also has a significant impact on the heat loss value, p < 0.0001, but is perhaps less useful when comparing samples to each other. It was found that comparing the different periods of the test could yield different conclusions when comparing materials for latent heat loss. Several current test methods do not consider phases outside of the steady state period and therefore miss valuable information pertinent to user comfort during these phases, especially in the post-exercise phase. [ABSTRACT FROM AUTHOR]

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The efficacy of saving energy standards depends on the ability to anticipate the heat loss of buildings. Environmentally friendly materials, also known as eco-friendly or sustainable materials, have a minimal negative impact on the environment throughout their life cycle. These materials are designed to conserve resources, reduce pollution, and promote sustainability. The characteristics of non-stationary and non-linear heat loss through environmentally friendly materials make it challenging to anticipate accurately. At the same time, many of the industry's presently accessible computational models have been created with this in mind; the majority call for powerful computers and time-consuming computations. The artificial neural network (ANN) has been utilized for prediction, and ground-breaking research has shown the viability of this strategy. This research proposes an artificial neural network (ANN) prototype to estimate construction cooling load usage. ANN is integrated with the vortex search algorithm (VS), stochastic fractal search (SFS), and multi-verse optimizer (MVO) models to compare the three models' outcomes and suggest a more accurate strategy. These techniques make a linear mapping among the output and input parameters, often utilized for modeling and regression. The value of the multiple determination coefficient is also determined. The values of the training R2 (coefficient of multiple determination) are 0.9464, 0.99827, and 0.99522 for VS-MLP, SFS-MLP, and MVO-MLP, respectively, with an unknown dataset which is acceptable. The training RMSE amounts for VS-MLP, SFS-MLP, and MVO-MLP are 0.06433, 0.00619, and 0.01028 for the unknown dataset, which is acceptable. According to the MAE values of 0.0082902, 0.0047834, and 0.0076534 in the training phase for VS-MLP, SFS-MLP, and MVO-MLP approaches and the values of testing MAE error of 0.029107, 0.018167, and 0.029212 for VS-MLP, SFS-MLP, and MVO-MLP approaches, respectively, it is obtained that the SFS-MLP has a lower MAE value. The lowest RMSE value and the higher R2 value indicate the favorable accuracy of the SFS-MLP technique. [ABSTRACT FROM AUTHOR]

The article presents a structure of the algorithm and mathematical and software systems. The general characteristics of the algorithm for determining heat losses in the hearth of a blast furnace based on the use of the heat balance of the lower zone are presented. External heat losses in the process of melting occurring through the tuyere belt, barrel, and bosh, are determined by the difference between the input and output components of the zonal heat balance for the lower part of heat transfer. The determination of heat losses by the heat balance in the lower heat transfer part allows their value to be estimated according to the current information about the operation of the furnace under specific raw materials and operating parameters. The information support of the system is presented, the software architecture is described, the characteristics of the software modules are given, and fragments of its work are illustrated. The information modeling system is distinguished by taking into account the basic physical and chemical laws of the processes of the control object, the principles of system analysis, and the use of modern principles for the development and construction of mathematical models and software. Heat loss control is necessary to assess the condition of the blast furnace refractory lining and rational gas distribution, as well as to adjust the coke rate. [ABSTRACT FROM AUTHOR]

The author has given a solution to the problem on the distribution of heat around a cylindrical rod of infinitely small radius and with a constant temperature. The obtained solution belongs to a novel class of self-similar problems with an arbitrary positive parameter approaching zero as close as is wished. Based on the obtained results, an asymptotic (at large times) expression has been found for the coefficient of heat transfer of a cylindrical pipe with a heat-insulation shell. [ABSTRACT FROM AUTHOR]

To reduce the volume of landfill sludge, a more environmentally friendly technology is used to study the effects of different freeze–thaw–vacuum pretreatment modes. In addition to the cumulative effect of cooling time within different temperature bands, we analyse the temperature difference loss rate of shallow sludge over the period of cooling. During the annular freezing process, the mechanism of ice front formation is revealed by exploring the energy transfer process of landfill sludge. When repeated freeze–thaw–vacuums are performed, the pretreatment modes of a single pre-freeze–thaw and two consecutive pre-freeze–thaws are compared. The superiority of two modes is discussed in the light of local differences in dewatering performance and overall settlement trend characteristics. Furthermore, the final micromorphological structure indicates that the repeated freeze–thaw–vacuum pretreatment mode of sludge is affected by its depth to a certain extent. It is found that factors such as sludge depth and radial water migration have a significant impact on the time accumulative effect and energy transfer of frozen sludge. The sludge treatment mode of two consecutive pre-freeze–thaws has a better effect on the overall dewatering and reduction. [ABSTRACT FROM AUTHOR]

Conversion of solar radiation into steam is presently one of the trends in "green" energy (solar thermal energy), ecology, and clean water production. For the first time, a study of the heating and evaporation of a rotating graphene nanofluid under the influence of radiation from a solar simulator was carried out. The influence of various factors on these processes, including the direction of irradiation, graphene concentration, and liquid rotation speed, is considered. It has been shown that the evaporation rate significantly depends on the graphene concentration and the method of irradiation of the samples. When samples are irradiated from the side, as the graphene concentration increases, the average evaporation rate increases and reaches a maximum value and then decreases. When samples are irradiated from above and the liquid–air interface is in direct contact with the incident radiation, only a decrease in the evaporation rate is observed as the graphene concentration increases. In this case, heating of graphene also depends on the method of irradiating the sample. When in direct contact with radiation, graphene is heated to a high temperature, while in the bulk it is heated less efficiently than the base liquid (distilled water). It has been shown that the rate of evaporation from the surface of a rotating graphene nanofluid and the temperature of its volume significantly depend on the rotation speed. Of all the samples studied, a graphene nanofluid with a volume concentration of 0.5% is heated most efficiently. The use of thermal insulation can improve heating by approximately 5%. An analytical calculation of the profile of the interfacial surface is presented and its area is determined at different speeds of rotation of the liquid. Some effects that arise during the rotation of a graphene nanofluid and their influence on the parameters of hydrodynamics and heat and mass transfer, which is important for fundamental and applied energy problems, have been identified. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents an analytical analysis of the effect of heat losses on the possibility of occurrence of the most effective gas-phase combustion of a single boron particle in air at different initial temperatures and pressures of the oxidizing medium. The analysis is performed with account for the possibility that the particle enters into an air medium (its temperature is lower than the melting point of boron) after its ignition and the establishment of a steady gas-phase combustion. A method for calculating the maximum initial air temperature below which a burning boron particle cools down and extinguishes is developed. The boundaries of the regions of its gas-phase combustion and extinguishing are determined. It has been established that when a single boron particle in a state of gas-phase combustion enters air with a temperature below the melting point, the main factor determining the its combustion mechanism is the air temperature. Depending on the air temperature, either the gas-phase combustion of the particle continues or the particle cools down and the gas-phase combustion changes to heterogeneous combustion. [ABSTRACT FROM AUTHOR]

A pilot plant comprising membrane distillation is tested for coordinated inlet temperature for the feed and cold streams with a fixed difference. Selected inlet temperature differences of 30, 40, and 50 °C were examined. It is found that water production increases with both temperature difference and inlet feed temperature. Specifically, the water production at a temperature difference of 50 °C can be 13%, and 30% higher than that at a temperature difference of 40, and 30 °C, respectively. The measurements of the mass flux were used to validate the internal mass and heat transfer equations which proved to provide an excellent prediction of the water production with up to 3.7% average error. The measurements of the exit temperature of the brine and permeate streams were used to confirm the macroscale heat balance equations. They revealed a considerable discrepancy between the heat supplied by the feed stream and the heat transferred between the two channels as well as between the heat gained by the cold stream and the heat supplied. The first discrepancy is ascribed to the existence of environmental heat loss at the feed side. The second discrepancy is attributed to the existence of environmental heat loss and the contribution of the heat of condensation to additionally warm up the cold stream. [ABSTRACT FROM AUTHOR]

Thermal efficiency serves as a crucial indicator of performance, facilitating the prediction of the overarching functionality of large-scale systems through the analysis of parabolic trough behavior in relation to the working fluid's temperature. This study examines the influence of heat loss on the efficiency of collectors, employing a numerical simulation to distribute the tube's thermal efficiency across the four distinct seasons. A comprehensive heat transfer model for the thermal analysis of parabolic trough solar receivers has been developed, considering significant variables such as solar intensity, the flow rate of heat transfer, and heat losses. This research endeavors to evaluate the performance of a specifically designed 24-metre parabolic trough solar collector (PTSC) under Cairo's climatic conditions, focusing on surface temperatures and thermal efficiency. The system was numerically analysed during winter, from January 15 to January 21, highlighting efficiency metrics across the week at a mass flow rate of 1.41 kg/s, where efficiency did not surpass 35% on the concluding day. The proposed model incorporates precise heat transfer correlations and an in-depth examination of radiative heat transfer, aiming to underpin the foundation for the manufacture of larger units within Egypt. The results indicate that thermal efficiency is critically impacted by heat loss, underscoring the necessity for refined models that accurately represent heat transfer dynamics within parabolic trough solar collectors. [ABSTRACT FROM AUTHOR]

Aiming at the low efficiency of heavy-oil thermal recovery, a downhole multi-thermal fluid generator (DMTFG) can improve the viscosity reduction effect by reducing the heat loss of multi-thermal fluid in the process of wellbore transportation. The steam generated by the MDTFG causes damage to the packer and casing, owing to the return upwards along the annular space passage of the oil casing. To mitigate this damage, a heat transfer model for multi-channel coiled tubing wells and a prediction model for the upward return of the steam temperature field in the annulus were established with the basic laws of thermodynamics. Models were further verified by ANSYS. The results indicate the following four conclusions. First of all, when the surface pressure is constant, the deeper the located DMTFG, the shorter the distance for the steam to return would be. It is easier to liquefy the steam. Second, the higher the temperature of the steam produced by the downhole polythermal fluid generator, the larger the upward distance of the steam would be. Third, the higher the steam pressure at the outlet of the downhole polythermal fluid generator, the smaller the distance of steam upward return would be. Finally, the larger the diameter of the multi-channel conversion piping, the greater the distance of the steam return would be. It is meaningful to provide valuable theoretical guidance for packer position designing in the field. Meanwhile, the study also provides a modeling basis for the subsequent study of artificial intelligence in the downhole temperature field. [ABSTRACT FROM AUTHOR]

Experimental investigations have been conducted in hydrogen-oxygen mixtures with equivalence ratio of 1.5 at cryogenic temperature (77 K) and initial pressure (P 0) from 0.2 to 0.5 atm. The pressure sensors and optical fibers are used to measure the overpressure and flame velocity, respectively. The precursor shock wave is formed by the combination of the 1st and 2nd shock waves. When flame catches up with the precursor shock wave, detonation occurs. Strong flame acceleration was observed in all tested conditions, which can be well characterized and predicted by the Zel'dovich number and expansion ratio. The stuttering and galloping modes were observed at 0.5 and 0.3 atm, respectively. With the decrease of the initial pressure to 0.20–0.25 atm, detonation could not occur, only the deflagration mode was observed. The stability of the mixture can be indicated by the parameter χ , and the improvement of stability of mixture will shorten the initial pressure range where the galloping mode occurs. The heat loss effect on detonation limit has subsequently been examined for the present experiments as well as those with equivalence ratio of 2.6 reported in our previous study [Shen, X. et al., Proceedings of the Combustion Institute 2022]. For equivalence ratio of 2.6, the heat loss is found to have dominant effect on the appearance of detonation limit. Its influence can be quantitatively characterized by critical ratio of heat loss to heat release. However, for equivalence ratio of 1.5, the heat loss effect is found to have only relatively small effect on detonation limit. • The combustion of hydrogen-oxygen mixture at cryogenic temperature of 77 K is investigated. • The 1st and 2nd shock waves would merge to form a stronger precursor shock wave. • Strong flame acceleration could be predicted by expansion ratio and Zel'dovich number. • The stuttering mode and the galloping mode of detonation are both observed. • The effect of heat loss on the detonation limit is examined. [ABSTRACT FROM AUTHOR]

The DOC (diesel oxidation catalyst), DPF (diesel particulate filter), SCR (selective catalytic reduction), and ASC (ammonia slip catalyst) are widely used in diesel exhaust after-treatment systems. The thermal management of after-treatment systems using DOC, DPF, SCR, and ASC were investigated to improve the efficiency of these devices. This paper aims to identify the challenges of this topic and seek novel methods to control the temperature. Insulation methods and catalysts decrease the energy required for thermal management, which improves the efficiency of thermal management. Thermal insulation decreases the heat loss of the exhaust gas, which can reduce the after-treatment light-off time. The DOC light-off time was reduced by 75% under adiabatic conditions. A 400 W microwave can heat the DPF to the soot oxidation temperature of 873 K at a regeneration time of 150 s. An SCR burner can decrease NOx emissions by 93.5%. Electrically heated catalysts can decrease CO, HC, and NOx emissions by 80%, 80%, and 66%, respectively. Phase-change materials can control the SCR temperature with a two-thirds reduction in NOx emissions. Pt-Pd application in the catalyst can decrease the CO light-off temperature to 113 °C. Approaches of catalysts can enhance the efficiency of the after-treatment systems and reduce the energy consumption of thermal management. [ABSTRACT FROM AUTHOR]

Carbonization is a highly energy-intensive process for converting biomass into solid fuel, especially in conventional systems without heat insulators. During the process, heat losses are unavoidable; thus, it is vital for utilizing insulators to minimize the losses. Clay, a naturally abundant and inexpensive material, could be used as an insulator. The corn cob carbonization process is carried out using a used oil drum as a carbonization kilns (reactor), with 200 L capacity and 1.25 mm thickness, by adding a Y-shaped pipe with a diameter of 100 mm in the center of it. The testing procedure involved coating one drum with a 1.5 cm clay insulator and leaving the other drum uninsulated. Each drum was then filled with 21 kg of dried corn cobs. A type K thermocouple is attached to the reactor's side wall and cover, and then connected to a Graphtec type GL240 datalogger for automated temperature measurement and recording. The study and analysis showed that in the absence of insulators, heat losses due to radiation and convection reached 3611.94 W (55.64%) during a 220-minute charcoal production (carbonization process). Meanwhile, when an insulator was used, the heat loss was reduced to 2320.69 W (35.75%) during the 170-minute charcoal production (carbonization process). Therefore, the utilization of clay insulators can result in 14.89% reduced heat losses and 22.73% shorter carbonization time. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the Japan Research Association for Textile End-Uses / Sen'i Seihin Shohi Kagaku is the property of Japan Research Association for Textile End-Uses / Sen'i Seihin Shohi Kagaku and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Special Oil & Gas Reservoirs is the property of Special Oil & Gas Reservoirs Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The largest energy loss in buildings, which have a significant potential for energy efficiency, occurs in the building envelope. At present, one of the most basic approaches to reducing heat loss in the building envelope, which consists of various layers of different thicknesses and properties, is to avoid thermal bridges. Thermal bridges are areas where heat conduction is higher than other components of the building and where moisture problems are primarily encountered and are of great importance in the evaluation of building energy performance. In today's widely applied reinforced concrete frame construction system, many thermal bridges occur for various reasons. Thermal bridges occurring at the corner points of the building significantly affect the average thermal transmittance of the building. These areas are also the areas where condensation and mould formation are common. The insulation status of these regions affects the thermal and hygrothermal performance. Necessary measures should be taken by calculating the hygrothermal performance of the building envelope during the design phase. Various simulation tools are used for this purpose. In this way, the building envelope can provide energy, comfort, and health conditions during the design phase. In this study, heat losses and hygrothermal performance of thermal bridges are investigated. The thermal bridges occurring at the corner point of an existing residential building were evaluated according to the conditions of uninsulated, partially insulated and externally insulated. Analyses within the scope of the study were carried out with Quick Field 6.3 and Wufi 2D-4.3 programs. In the analyses, it is seen that 37% more heat loss occurs in the case of partial insulation of thermal bridges than in the case of continuous external insulation. Likewise, in terms of hygrothermal performance, there is no condensation risk in the case of continuous external insulation. [ABSTRACT FROM AUTHOR]

This study aims to solve the problem of decarbonization of industrial emissions from metallurgical furnaces using the process of carbothermic reduction of silicon in ore-thermal furnaces (OTFs) as an example. The methods used for cleaning the exhaust gases cannot completely ensure the processing of carbonaceous emissions. We propose a method of using conversion-type gasifiers for carbon reduction when processing combustion products of exothermic reactions in metallurgical units. Computational fluid dynamics and mathematical modeling are applied to confirm the feasibility of the proposed solution. As part of the scientific problem of decarbonization associated with reducing the carbon footprint, the thermodynamic processes in changing the dust–gas medium composition based on the solution of fundamental principles related to the modification of the Bell–Boudouard equation have been analyzed. Consequently, the calculated value of the carbon dioxide flow rate can become the initial parameter for the calculation model of a conversion gasifier for an OTF in the production of metallurgical-grade silicon. [ABSTRACT FROM AUTHOR]

A major amount of fuel energy is lost in the form of heat is one of the major concern in an internal combustion (IC) engine, which can be avoided by providing the engines with better cooling systems in automobiles. Due to weight constraints, air cooling is the only way to cool the small engine in motorcycles. The fins significantly increases the heat transfer rate, but by changing their parameters, the rate of heat transfer of these fins can be increased even further. The majority of previous research has been done on small displacement engines ranging from 50 cc to 150 cc, and no research work has been reported beyond that. The majority of previous work has been carried out on fin shape and design rather than its thickness and count. These concerns have been addressed in this study, where an analysis of the heat transfer of air-cooled IC engines with a displacement of 373 cc has been taken into consideration. The design modelling of the engine body has been done with different fin thicknesses. In the first phase, computational fluid dynamics (CFD) analysis of the engine body has been done by SOLIDWORKS Flow Simulation. Airstream passing over the engine body has been studied at variable speeds. Thermal analysis of the engine body was carried out by varying the vehicle speed, fin thickness, and materials. Properties like temperature on the fin, temperature on the engine head, and heat loss from the engine were analysed for different vehicle speeds, fin thickness, and materials. Lastly, the results obtained by using those boundary conditions were compared with previous research and reported. It was found that fins with a thickness of 5 mm performed better with Aluminium Alloy as their material as compared to other fin thicknesses and materials. This will help with optimum cooling of the engine, which makes the motorcycle engine perform well and increase its life. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Steam flooding is one of the most widely used heavy oil thermal recovery technologies. Steam transfers heat to heavy oil to reduce viscosity and improve fluidity. The current problem is that steam loses a lot of heat in the formation, and there are serious carbon emissions in the whole production process. In this paper, flue gas and steam were combined to drive heavy oil in the form of composite thermal fluid, and foam was added on this basis. With the help of one-dimensional sandpack model, both single-model and parallel dual-model with permeability ratio experiments were conducted to investigate key characteristics such as steam heat transfer, heavy oil production and flue gas retention during the displacement process. The experimental results indicated that flue gas effectively inhibited steam condensation and reduced heat loss during the flow process. Compared to steam flooding, the sandpack model exhibited temperature rises of 4.4°C and 9.1°C at the middle and end, respectively. While flue gas foam fell slightly short of flue gas in terms of enhanced heat transfer, it outperforms in recovery factor, achieving a 10.4% improvement over flue gas-assisted steam flooding. The foam blocked gas channeling by accumulating and capturing along the flow path, resulting in a gas retention volume of 389 mL within the model. Furthermore, the flue gas foam facilitated steam flow to previously unswept low-permeability areas, thus enhancing oil recovery. In the parallel double-model experiment, the low-permeability model exhibited significantly improved oil displacement efficiency compared to flue gas-assisted steam flooding, and the remaining oil content in the end of the high permeability model was increased by 1.9%, while the remaining oil content in the front and end of the low-permeability model was reduced by 3.5% and 3.8% respectively. [ABSTRACT FROM AUTHOR]

The occurrence of late spring frosts due to climate change causes great damage to plantation production worldwide. The main objective of the paper is to provide a comprehensive overview of the problem and to outline effective protective measures against late spring frosts. The nature of frost depends on regional, altitudinal, and geographic differences, but they all share a common problem: they remove heat, resulting in the freezing of new plant growth and flowers. Tissue freezing is affected by critical temperatures and the frost type, intensity, and duration. Protection against late spring frosts can be broadly divided into three categories: active, passive, and chemical measures. In the field of agricultural engineering, various techniques have been thoroughly researched, and their effectiveness has been confirmed by research. These include various sprinkler systems, different heating devices, and large-diameter fans. Conclusive findings are being made on the performance of these systems in sub-zero temperatures and their cost-effectiveness. Climate change increases the importance of protecting permanent crops from late spring frosts and requires advances in agricultural technology to meet changing production demands and challenges. [ABSTRACT FROM AUTHOR]

The attainment of energy sustainability in the building sector can be realised by implementing a green building programme, which has grown significantly over the last thirty years. Green building is considered a technical and management strategy within the building and construction industries. Many different prediction methods, both complex and simple, have been put out in recent years and used to solve a wide variety of issues. Several case studies have highlighted factors that impede energy and resource usage in green buildings. The utilisation, trends, and consequences of wall and thermal insulation materials are examined. The main scope of this investigation is to predict buildings' heat loss by applying artificial neural networks according to the heat transfer coefficients of walls and coating materials, as well as indoor, outdoor, and external surface temperatures. The data has been normalised and presented to two selected neural networks (Harmony search (HS) and particle swarm optimisation are used and contrasted (PSO)). For evaluating the accuracy of models, two statistical indexes are used (R² and RMSE). Model performance of PSO-MLP is shown by R² amounts of 0.97055 and 0.87381, respectively, and RMSE amounts of 0.02534 and 0.09685. Similarly, HS-MLP model accuracy is also indicated by R² amounts of 0.93839 and 0.84176 and RMSE amounts of 0.03635 and 0.10753. The analysis in this paper shows that PSO-MLP predicts heat loss with higher accuracy and improved performance. [ABSTRACT FROM AUTHOR]

The paper presents the results of experiments with a solar greenhouse used to ensure the most favorable temperature regime. In order to provide thermal insulation and reduce heat losses, a solar greenhouse structure with an arched shape and a total area of 200 m2 has been developed. It is located directly in the ground, at a depth of 0.5 m and a height of 4.0 m above ground. The total height of the greenhouse is 4.5 m, the length is 20 m, and the width is 10 m. These dimensions comply with the standards established in KMK 2.09.08-97 Greenhouses and Hotbeds. On the outer part of the solar greenhouse, a layer of dry straw with sufficient permeability to sunlight is placed between two transparent enclosures during the winter period for thermal insulation. This significantly reduces heat losses through the top transparent surface and enhances the greenhouse effect. This transparent enclosure design allows heavy mechanical loads, is resistant to mechanical cleaning processes, and at the same time, has high thermal insulation properties. By using the solar greenhouse structure with the energy flow scheme presented, a more homogeneous air environment with temperature inside the greenhouse can be achieved, even during daily fluctuations in the temperature of the surrounding air. The temperature and humidity parameters inside the solar greenhouse vary due to the absorption of solar radiation from the ground surface and the evaporation of moisture from the soil. The results of the experiments show that the solar greenhouse based on our energy flow scheme, using the ground as thermal insulation, significantly reduces heat losses through the floor. The method of insulation between two transparent enclosures provides a more homogeneous air environment with air temperature inside the greenhouse, despite significant daily fluctuations in the temperature of the surrounding air, and effective accumulation of solar energy inside the solar greenhouse. [ABSTRACT FROM AUTHOR]

At present, the majority of large electrotechnical companies around the world develop and produce high-voltage equipment involving the use of SF6 gas (sulfur hexafluoride, commonly known in Russia as elegaz). SF6 is a nontoxic, stable, chemically inert, nonflammable compound, which does not have color, smell, and taste, and which at STP conditions (20°С and 0.1 МPа) is in a gaseous state. By totality of its properties, SF6 gas is most preferred for use as insulating and arc-quenching medium in electrical apparatuses. However, at low temperatures SF6 transfers from a gaseous to a liquid state, in which its breaking capacity becomes degraded. Specialists have to cope with this problem in the development of equipment to be installed outdoors in regions with a cold climate. This drawback can be overcome by heating the apparatuses at an ambient temperature below the SF6 saturation temperature. The article considers a solution of this problem as applied to the linear bay of the ZF7-126 gas-insulated switchgear (GIS) by the China XD Group and ЕK ВВА. The power capacity of the device required for heating the GIS chambers filled with SF6 is determined subject to the conditions of bringing the equipment from cold to serviceable state within 2 h at an ambient temperature of –45°С. The device power must be sufficient for SF6 to transfer from liquefied to gaseous state (at a temperature on the chamber inner wall of –20°C), for heating the GIS chamber housing components frames, and to compensate for the heat loss from the chamber surfaces. The results of comparing the heat loss from the chamber surfaces when the GIS installed outdoors and indoors in an unheated room are presented. Recommendations on selecting the heating cable specific capacity and length in heating the sections of GIS chambers cylindrical surface. The article also presents the results of calculating the temperature variation on the chamber inner wall with distance away from the sections of the heated thermally insulated surface. [ABSTRACT FROM AUTHOR]

Thermoelectric devices are one of the technologies used either to generate electricity by applying a temperature difference using thermal energy or as a heating/cooling system by applying an electrical voltage. The number of materials required to produce a product is an important factor in determining its price. Production costs associated with these materials, as well as their availability and quality, play a crucial role in price determination by manufacturers. In this context, a method that employs a uniform volume distribution was implemented. This approach enabled the analysis to focus on other variables, thereby promoting a more precise and relevant evaluation of overall performance. Based on the finite element method, this study investigated the influence of geometric shape, including Rect-leg, Y-leg, Pin-leg and X-leg designs, on the performance of solar thermoelectric generators and thermoelectric coolers. The study was conducted considering the same hot alumina junction surface that receives solar radiation; however, the effective surface, which corresponded to the heat flow area and had a similar area near the exposed surface, varied depending on the chosen leg geometry, thus impacting the heat flux due to the variation in thermal resistance. In the case of a solar thermoelectric generator, the Rect-leg model, having the same effective surface area, presented the lowest heat loss value resulting from convection and radiation in the heat spreader and the hot alumina plate. Under the same conditions, the Y-leg showed the highest value. The Rect-leg design generated, by using thermal and optical concentration, the highest output power of 0.028 and 0.054 W, and efficiency of 3.47% and 4.7%, respectively, whereas the Y-leg generated lower values of 0.006523 and 0.018744 W for power, and 2.83% and 2.71% for efficiency, respectively. In the case of the thermoelectric coolers, the Y-leg generated the highest temperature difference between the hot and cold sides of 67.28 K at an electric current value of 1.8 A, whereas the Rect-leg, Pin-leg and X-leg generated ~66.25, ~67.02 and ~67.19 K at 6.1, 2.7 and 2.6 A. [ABSTRACT FROM AUTHOR]

The occurrence of late spring frosts due to climate change causes great damage to plantation production worldwide. The main objective of the paper is to provide a comprehensive overview of the problem and to outline effective protective measures against late spring frosts. The nature of frost depends on regional, altitudinal, and geographic differences, but they all share a common problem: they remove heat, resulting in the freezing of new plant growth and flowers. Tissue freezing is affected by critical temperatures and the frost type, intensity, and duration. Protection against late spring frosts can be broadly divided into three categories: active, passive, and chemical measures. In the field of agricultural engineering, various techniques have been thoroughly researched, and their effectiveness has been confirmed by research. These include various sprinkler systems, different heating devices, and large-diameter fans. Conclusive findings are being made on the performance of these systems in sub-zero temperatures and their cost-effectiveness. Climate change increases the importance of protecting permanent crops from late spring frosts and requires advances in agricultural technology to meet changing production demands and challenges.

An energy-efficient switched reluctance electric drive is considered in relation to electric rolling stock. It fully meets such requirements as good adjustment properties, high energy efficiency and operational reliability. The scientific and technical value of the results of the work lies in the development of an algorithm for controlling a traction switched reluctance motor that reduces the operating current while providing the necessary power. The calculations are made by means of specialized programs interacting with each other FEMM and MATLAB. The materials of this study are of practical value for improving the operational and technical and economic indicators of electric rolling stock.

Among the recognized patterns in traditional Iranian architecture, bathhouses have been considered to prevent the heat loss required by users during bathing. In this regard, various assumptions have been made about effective strategies to reduce heat loss and energy storage in different interpretations of traditional bathhouses. However, the function of these strategies has not been investigated with respect to the climatic differences of different cities in Iran. Therefore, the aim of this research is to compare more accurately the recognized physical strategies in this regard, including "density in texture and neighborhood", "entering the ground", "thermal mass of the building", and "enclosing the greenhouse space among uncontrolled spaces" in two bathhouses in Kerman city. This issue has been carried out quantitatively and with an energy simulation solution, and can have more computational credibility compared to previous estimates due to the extraction of calculations from thermal modeling of the discussed bathhouses. In the research process, two bathhouses, "Ganj Ali Khan" and "Vakil Kerman", were selected as examples and the amount of heat loss was calculated during cold months using Design Builder software based on volumetric and structural evidence of the discussed bathhouses. The results of this study indicate that the thermal mass of the building and enclosing the greenhouse space among uncontrolled spaces were the most effective strategies in preventing heat loss in the discussed bathhouses. These two strategies, depending on the type of walls and the centrality of the greenhouse among other spaces, had similar efficiencies while having diverse functions. The thermal mass of the walls in Ganj Ali Khan and Vakil Kerman bathhouses had an average impact of 39% and 44%, respectively, on reducing heat loss. This value was 23% and 14%, respectively, for using uncontrolled spaces around the greenhouse. The efficiency of these two strategies was approximately two to eight times higher compared to "entering the ground" and "density in texture and neighborhood", emphasizing their importance in design.