Thermal Balances Research Articles

Calculation of production balances and costs in ladle furnace refining process with addition of scrap steel

As increasing the scrap steel ratio has become an important approach for energy conservation and emission reduction in the steel industry, the technology of multi-point scrap addition has emerged. Ladle furnace (LF) refining is a feasible step for scrap steel utilisation, which is often overlooked and relied solely on empirical adjustment, resulting in difficulty of precise control. It is necessary to conduct in-depth research on this process using scientific methods and explore the impact of scrap steel addition on other materials. A comprehensive calculation model was established by scientifically investigating material and thermal balances in the LF process in this article, and the impact of initial steel and scrap compositions, temperature, mass and price of scrap on production costs were analysed and compared based on the model. The results showed that as the carbon and silicon content in the initial steel increase by every 0.01% could on average reduce the production cost per ton of steel by 4.013 CNY and 0.8473 CNY, respectively, and increases by 0.123 CNY as the sulphur content increase every 0.001%. The impact of scrap composition on costs is similar to that of the initial molten steel. Increasing the carbon and sulphur content in scrap by every 0.01% will on average increase costs by 0.0765 CNY and 0.01 CNY, respectively. When the price difference between scrap and the crude steel price is within 450–500 CNY/t, increasing scrap addition will create more profit. The relative reduction in smelting time is 7.97 s as the scrap temperature increases every 50°C. The present study holds academic and industrial significance in improving LF efficiency and promoting the LF process towards a more sustainable direction.

A Direct Entropic Approach to the Thermal Balance of Spontaneous Chemical Reactions.

When working with, and learning about, the thermal balance of a chemical reaction, we need to consider two overlapping but conceptually distinct aspects: one relates to the process of reallocating entropy between reactants and products (because of different specific entropies of the new substances compared to those of the old), and the other to dissipative processes. Together, they determine how much entropy is exchanged between the chemicals and their environment (i.e., in heating and cooling). By making explicit use of (a) the two conjugate pairs chemical amount (i.e., amount of substance) and chemical potential, and entropy and temperature, respectively, (b) the laws of balance of amount of substance on the one hand and entropy on the other, and (c) a generalized approach to the energy principle, it is possible to create both imaginative and formal conceptual tools for modeling thermal balances associated with chemical transformations in general and exothermic and endothermic reactions in particular. In this paper, we outline the concepts and relations needed for a direct approach to chemical and thermal dynamics, create a model of exothermic and endothermic reactions, including numerical examples, and discuss how to relate the direct entropic approach to traditional models of these phenomena.

Reliability-based sizing of islanded multi-energy microgrid: a conic chance-constrained optimization approach

AbstractThis paper presents a methodology to optimally design a multi-energy microgrid with thermal and electric loads considering $$N-1$$ N - 1 and probabilistic regulation reserves. This methodology consists of a chance-constrained optimization that determines the optimal sizing of the microgrid. Microgrid operations are rigorously considered by modelling hourly thermal and electric demand patterns as well as technology production schedules over a year. Such schedules include both electric and thermal power balances, ramp constraints, $$N-1$$ N - 1 and regulation reserves, among others. To ensure a reliable microgrid design and operation, reserve constraints have been proposed to deal with both $$N-1$$ N - 1 generation contingencies, and forecast errors. $$N-1$$ N - 1 reserves guarantee that a sudden outage of any of the electric generators is strategically covered by the remaining generators in order to avoid load shedding. Additionally, nonzero-mean random forecast errors of electric load and solar production are addressed by a set of chance constraints able to schedule asymmetric up and down regulation reserves. Their levels are high enough to cover hourly random forecast errors (or intermittencies) with a high threshold probability. The proposed methodology results in a mixed integer second-order cone program. Results of microgrid designs with and without reliability reserves are carefully analysed and compared. Neglecting reliability constraints leads to a lower-cost design at the expense of exposing the microgrid to unsafe operation. Finally, sensitivity analysis to study the optimal portfolio sizing with respect to electric BESS investment cost, solar production forecast mean error, and random intermittency threshold probability are performed.

Prediction of Production-Inflow Profile of a Well Producing Single-Phase Flow of Slightly Compressible Fluid from Multilayer Systems by Temperature and/or Pressure Transient Data

Summary This study focuses on the prediction of the production-inflow profile of a well producing a single-phase flow of slightly compressible fluid (water or oil flow) in a multilayered system using the layer permeability and skin values estimated by history matching spatial and temporal temperature and/or pressure data sets along the completion interval. Such data may be acquired by wireline formation testing, production-logging-tool (PLT), or distributed temperature sensing (DTS) fiber-optic cables. We use an in-house thermal, transient coupled reservoir/wellbore simulator developed during this study. It solves transient mass, momentum, and energy conservation equations simultaneously for both reservoir and wellbore. The effects of the Joule-Thomson (J-T), adiabatic expansion, conduction, and convection are all included for predicting the flow profiles across the wellbore. The results from our in-house simulator are verified with the results from a commercial simulator for the single-phase fluid flow of a vertical well producing geothermal brine and oil in a two-zone multilayer system. We also compare the results from our rigorous transient coupled wellbore/reservoir model with the results from a model assuming steady-state thermal wellbore model used in the previous studies. We find that the steady-state thermal wellbore model used in the previous studies that ignore accumulation terms in mass, momentum, and thermal energy balances is a reasonably accurate model for predicting wellbore pressures and temperatures when it is coupled with a nonisothermal reservoir model for slightly compressible fluid because the transient effect in the wellbore is less important with the slightly compressible fluid. We investigate the nonlinear parameter estimation problem based on the use of single or multiple observed temperature and/or pressure (if available) profiles recorded spatially inside the wellbore and at the sandface. The purpose is to identify if the wellbore or sandface data profiles are more useful to accurately estimate the permeability and skin information and predict a production-inflow profile of the well depending on the representation of an actual multilayer system by a reduced-layered or fine-layered model. We show that using an upscaled-layered model (e.g., representing each heterogeneous layer with a lumped single layer with uniform permeability and skin) provides estimates that are more toward the thickness-average permeability and skin factors of the layers and may not provide a good prediction of the well’s production-inflow profile. We show that including the sandface temperature data in regression worsens, while the use of wellbore temperature data sets improves the quality of parameter estimation if an upscaled multilayered model is used. We also show that regressing on multiple temperature profiles, preferably at the sandface, alone could be used to predict the production-inflow profile accurately if a “fine” multilayered heterogeneous model is used. We also investigate if including or excluding the temperature and/or pressure measurements at the nonperforated sections along the completion interval could help enhance the parameter estimation problem. The results show that when multiple profiles of temperatures including the data at nonperforated zones at different production rates are regressed, reliable estimates of the individual layer properties that predict the production-inflow profile accurately can be obtained, though layer permeability and skin factors may often exhibit wide 95% confidence intervals and high correlations among them. Adding sandface or wellbore pressure data, if available, into observed data sets in history matching always improves the quality of parameter estimation.

A Review of the Modeling of Parabolic Trough Solar Collectors Coupled to Solar Receivers with Photovoltaic/Thermal Generation

This paper is a summary of the last ten years of work on the study of parabolic trough collectors (PTCs) and compound parabolic collectors (CPCs) coupled to photovoltaic and thermal solar receiver collectors (SCR-PVTs). While reviewing the state of the art, numerous review papers were found that focused on conventional solar receiver collector (SRC) technology for solar thermal generation. However, there is a lack of review papers summarizing SRC-PVT hybrid technology for solar electric/thermal generation, which would be beneficial for researchers interested in this area of research. This paper provides a review of SRC-PVT hybrid technologies. The theoretical foundations for analyzing and modeling PTC and CPC concentrators coupled to SRC-PVT are described, with an emphasis on modeling through thermal resistances and energy balances. Additionally, this section provides a concise overview of previous studies that have addressed the modeling of PTC and CPC collectors coupled to SCR-PVT, as well as experimental information useful for the validation of new mathematical models of SRC-PVT.

Parametric Analysis of a Radiant Gas Heating System for Controlled-Environment Agriculture with Preheated Ventilation

This article explores the fundamental principles of the software method for calculating the gas-fired heating system of a cultivation structure, where the main source of heat is provided by ceiling-mounted gas infrared radiators. To maintain the required thermal regime within the premises, a gas air heater is utilized, designed to preheat the outdoor air to the necessary temperature before supplying it to the heated space.The calculation method is based on solving a system of interconnected equations of thermal and material balances for the cultivation structure, its enclosure, and the soil surface. Possible utilization of thermal energy from high-potential combustion products of gaseous fuel is taken into account.Using the example of the “Farmer 7.5” industrial greenhouse (Russian Federation), designed for year-round cultivation of plants in closed soil (in this case, cucumbers were the subject of study until the fruitbearing stage in the winter-spring cycle), the impacts of various factors are investigated: outside air temperature, thermal resistance of the enclosing structure on the heating system’s thermal power (in combination with the gas air heater), and variable parameters of the microclimate. The latter includes the enclosure temperature of the industrial greenhouse and the intake air temperature for general exchange ventilation needs. Specific conclusions and prospects for further scientific research are drawn based on the obtained results.

РЕКУПЕРАЦИЯ ТЕПЛОТЫ ИЗ ВОЗДУХА, УДАЛЯЕМОГО ИЗ ЖИВОТНОВОДЧЕСКОГО ПОМЕЩЕНИЯ

The air removed from the livestock premises by the forced ventilation system contains a significant amount of heat, that can be usefully used, for example, the supply air heating. Currently this energy saving area in the literature is being actively considered. The amount of heat air had being recovered from the indoor rooms depends on the area’s latitude where the livestock farm is located. The influence of cattle farm area’s latitude location saving heat from the air removed from the livestock premises is analyzed. The calculations for three regions of the Russian Federation’s European part located at different latitudes (Rostov, Tambov and Arkhangelsk), in relation to a 280-head cattle farm were performed. To determine the thermal power extracted from the exhaust air, these rooms thermal and material balances (the latter in terms of moisture and carbon dioxide) for the cold (winter) period of the year were compiled and the exhaust air consumption was calculated. In the calculations, a scheme of intermediate coolant, propylene glycol was considered, that circulates between two heating units, the first -on supply air, the second one - on the removed one were installed. It is shown that the farm’s location area latitude gives a significant impact on the energysaving effect: the more northerly the farm is located, the greater the effect, explaining by different indicators of the regions’ heating period under consideration. An payback period’s assessment for capital expenditures and installation work of this system implementation was carried out. The cost of three KSk3-11 brand heaters, a Grundfos UPS 32-80 F 220 circulation pump, 50 liters of propylene glycol aqueous solution, and 100 m of mounting pipes to material costs are attributed. This assessment showed considered heat recovery system’s expediency using. The numerical calculations of obtained results for country’s specified regions can be used economic effect magnitude estimate resulting.

The exergetic approach for the analysis of HDH desalination process using a pulverized column

In the process of humidification-dehumidification, the cross transfer of heat and mass is due to the affinity between water and air. In the present work, a mathematical model was developed basing on the mass, thermal and exergy balances in order to analyse the performance of a freshwater productivity by desalination of seawater. Firstly, we acquired the thermodynamic properties of the binary system (air-vapour water) through the use of the virial equation of state. To determine the impact of operating variables on the performance of the unit, the concept of degrees of freedom has been introduced. Basing on a rigorous algorithm, the performance of HDH was approached by calculating the productivity of fresh water and exergetic efficiency in relation with the operating variables. The results of the simulation show that the productivity and the gained-output ratio (GOR) increase with the increase of the ratio of the flow rates and the temperature of the inlet air in the humidifier. However, it decreases simultaneously with the outlet water temperature. Besides, the humidifier and dehumidifier exergetic efficiencies increase simultaneously by increasing of the mass flow rates ratio and the temperature of the air at the inlet of the humidifier. Also, we note that the exergetic efficiency of the dehumidifier decreases with outlet water temperature. The simulation results establish that the collector performance diminishes with the liquid mass flow rate. Nevertheless, these results show that the major part of exergy destruction in the unit is localized in the collector with the lowest exergetic efficiency. The largest exergy losses are caused by increasing of the pinch of temperature.

An approach for computing the thermal balance and energy consumption of concrete pits during boiling of frozed logs for veneer production

ABSTRACT An approach for computing the thermal balance and energy consumption of pits during boiling of frozed logs intended for veneer production has been presented. With the help of our own non-stationary model, the boiling times of beech logs with a diameter of 0.4 m, initial temperature of −10°C, and moisture content of 0.6 kg·kg−1 were determined at water temperatures in the pit equal to 70°C, 80°C and 90°C. Using the determined logs’ boiling durations and the mentioned approach, the change in energy required for the entire boiling process and that for each of the components of the thermal balance was calculated. Computer simulations were performed for concrete pit with a volume of 20 m3 and a degree of filling with logs 45%, 60%, and 75%. It was found that the total energy consumption of the pit increases from 169 to 205 kWh·m−3 when the temperature of the boiling water increases from 70°C to 90°C at a pit filling level of 75%. The approach can be applied to compute thermal balances of concrete pits during boiling of frozed and non-frozed logs to any desired final average mass temperature required for the mechanical processing of the plasticized logs.

The Influence of Roost Type and Diet on Energy Expenditure in Bats

Bats spend most of their lives resting, socializing, and raising their young in roosts. Roost conditions may affect the lifetime energy expenditure of bats, and this could, in turn, influence fitness of individuals. Different kinds of roosts impose different microclimatic conditions that can affect the thermal balances of bats that use them. Bats thermoregulate by using both physiological mechanisms (such as changes in conductance) and behavioral responses (huddling or active search of certain microclimates). We hypothesized that the contribution of these thermoregulatory strategies would differ depending on the roost type that bats use. To test this idea, we collated data from the literature on metabolic rate (MR), body temperature (Tb), ambient temperature at which MR and Tb were collected, roost type, and diet for 43 species of bats spanning eleven families. From these data, we calculated, for each species, the wet conductance and the area of the thermoregulatory polygon (TRP) as a proxy for the physiological thermoregulatory capabilities of bats. We found that, after controlling for phylogeny, wet conductance and the area of the TRP were higher in bats that use more exposed roosts than in those bats who use roosts that can buffer environmental conditions. Our results suggest that energy expenditure is similar for all species, but in bats that live in more exposed roosts, the contribution of physiological responses was more important than behavior at the entire range of environmental temperatures, whereas bats in more protected roosts seem to rely more on behavioral responses to thermoregulate. Considering that roosts represent valuable resources, the availability of roosts with the proper microclimatic conditions could determine the patterns of distribution of bat populations.

Reliable energy management of residential buildings with hybrid energy systems

Distributed energy resources like photovoltaic (PV), fuel cells (FCs), and others are receiving more and more attention as a solution to the rise in residential energy consumption. In this paper, a reliability-based energy management model is proposed for residential buildings with local generation units. The proposed model studies the contingency analysis of the hybrid system of the residential buildings considering demand response (DR) programs under different participation rates of residents in DR. Along with accounting for the energy flows across the various components of the hybrid energy system, the analysis of PV power output utilization to sale of power to the main grid, battery charging, and demand supply are also taken into consideration. The proposed model aims to choose the best operating strategies while ensuring the system is well-functioning with energy supplement costs as the objective function to be reduced. In addition to the optimal electric and thermal balances, findings allow for the reasonable deduction of the PV module and fuel cell forms. A numerical example is implemented and examined to confirm the practicality of the suggested approach. From various viewpoints, the best operational techniques are determined and contrasted, where the findings are analyzed considering the reliable operation of the system. Applying DR with different participation rates has varying effects on energy management during contingency occurrences at off/on-peak hours. A 30% DR participation during off-peak hours reduces daily energy supplement cost by roughly one third. During on-peak hours, DR participation reduces energy supplement cost by over 76%.

Resource and Energy Saving Control of the Steelmaking Converter Process, Taking into Account Waste Recycling

With the development of the energy control system of iron and steel enterprises, the urgency of solving the problem of the resource and energy saving control of steelmaking processes increases, taking into account the reconfiguration of production to a new task, intensification of the processes of recycling of raw materials, as well as reducing the waste intensity of production. The way to solve the problem of resource and energy saving of steelmaking production is the creation of a computer system. It allows one to analyze the state of the refractory converter lining, calculation of the material and thermal balances, the amount of slag-forming materials, the quantitative characteristics of slag corrosion, as well as predict the phase and chemical composition of the slag in order to impart the properties necessary in the production of mineral binders and other building materials. The computer system allows one to identify complex fuzzy relationships between process parameters and issue recommendations on the resource and energy saving control of the converter process, taking into account the waste recycling. The testing of the computer system, according to the industrial data of the enterprises CherMF (PJSC Severstal) and PJSC NLMF, confirmed its operability and the possibility of its use at iron and steel enterprises.

MAVEN/NGIMS Dayside Exospheric Temperatures Over Solar Cycle and Seasons: Role of Dayside Thermal Balances in Regulating Temperatures

AbstractSeveral important processes of the Mars upper atmosphere are regulated by exospheric temperature (Texo) variations, including atmospheric escape rates. From the MAVEN mission, significant and largely periodic variability of Mars dayside Texo is now revealed by Neutral Gas and Ion Mass Spectrometer (NGIMS) data sets collected throughout solar cycle 24. Two complementary methods are utilized to extract temperatures from NGIMS data sets. These NGIMS dayside mean exospheric temperatures are shown to vary by ∼80 K (∼180–260 K) over solar cycle 24. This corresponds to a ΔTexo/ΔEUV sensitivity of ∼38 K m2 mW−1, where Lyman‐α is the solar index. Previous Mars Global Surveyor derived Texo values for solar cycle 23 yielded a sensitivity of ∼45 in the same units. This close correspondence suggests that the underlying dayside energy balances are similar yet slightly different over these two solar cycles. Corresponding Mars Global Ionosphere‐Thermosphere Model simulations show that molecular thermal conduction largely balances EUV heating for the Mars dayside thermosphere, while CO2 15‐µm cooling is secondary in importance, along with global winds. It is valuable to compare this Mars sensitivity to that computed for the dayside thermosphere of Venus. Pioneer Venus dayside data sets imply a sensitivity of ∼17.5 K m2 mW−1 units for solar cycle 21, a factor of ∼2.2 smaller than computed for Mars. This is because Venus CO2 cooling strongly balances EUV heating near its peak, thereby serving as a more efficient thermostat regulating dayside temperatures. CO2 cooling is much weaker for Mars.

Определение теплового режима изделия на поверхности Луны с учетом зеркально-диффузного отражения

The paper considers issues of calculating the thermal regime of a spacecraft on the Moon surface. A method for calculating the external radiant fluxes is provided for this case. Geographical position of the spacecraft on the Moon surface and the initial date were set as the initial data for calculation. The spacecraft thermal regime was calculated by the method of thermal balances on the Moon surface taking into account the specular-diffuse heat transfer for cases, where the nature of the outer surface reflection of the screen-vacuum thermal insulation (SVTI) is diffuse or specular. The calculation showed that the nature of reflection (specular or diffuse) of the SVTI outer surface for the case under consideration was not affecting the SVTI surface temperature and the spacecraft temperature, and its operating temperature ranged from 80 to 400 K.

Mathematical Modeling of Nucleation and Growth Processes of Ellipsoidal Crystals in Binary Melts

The transient behavior of an ensemble of ellipsoidal particles in a supercooled binary melt is considered. The model laws, based on the Fokker-Planck type kinetic equation for the particle-volume distribution function, the thermal and mass integral balances for the binary melt temperature and solute concentration, as well as the corresponding boundary and initial conditions, are formulated and solved analytically. We show that the temperature and concentration increase with time due to the effects of impurity displacement and latent heat emission by the growing ellipsoidal particles. These effects are also responsible for metastability reduction. As this takes place, increasing the initial solute concentration in a metastable binary melt increases the intensity of its desupercooling. The theory is developed for arbitrary nucleation frequency with special consideration of two important nucleation kinetics according to the Meirs and Weber-Volmer-Frenkel Zel’dovich mechanisms. An analytical solution to the integrodifferential model equations is found in a parametric form. The theory contains all limiting transitions to previously developed analytical approaches. Namely, it contains the growth of spherical crystals in binary melts and ellipsoidal crystals in single-component melts.

Simplified heat pump system model integrated in a tool chain for digitally and simulation-based planning shallow geothermal systems

In planning tools for shallow geothermal source systems, the heat pump is often considered in a highly simplified way without any dedicated control behavior or individual system setup. In this article, a simplified black-box heat pump system model for individual buildings up to city districts is presented that can be coupled to subsurface models. The model contains simplified algorithms for thermal storage balances and control strategies and is integrated into a tool chain for planning shallow geothermal systems in the early planning phase. The source code of the presented heat pump model is provided open-source according to the MIT license.

Mathematical description of the processes occurring during active grain ventilation

The subject of the study is the process of active ventilation of wheat grain with variable heat supply. The purpose of the work is a mathematical description of the nature of the flows of matter and energy in the process of active ventilation of wheat grain. Thanks to the selected original design of the exhaust coolant outlet unit, made in the form of a mesh spiral tube, it was possible to optimize the hydrodynamic situation in the layer of dried grain. The developed mathematical model, as a mathematical description, consists of equations of material, thermal balances, equations of hydrodynamics in steady and unsteady states. This mathematical model is the basis for creating a material model of the process and conducting an experiment with subsequent data processing. As a result, it is possible to obtain criteria equations of processes that make it relatively easy to calculate processes under various technological modes.

Методика оценки влияния эксплуатационных параметров на работу турбопитательного насоса

Background. Turbine feed pumps (TFP) are one of the main consumers of thermal energy for in-house needs of thermal power plants and nuclear power plants. Currently, much attention is paid to improve the efficiency of operation of turbine feed pumps. Thus, it is necessary to assess the impact of operational parameters. The problem is that it is necessary to process a large array of data. The solution to the problem is the development of a methodology that allows quantitative and qualitative assessment of operational parameters. Materials and methods. As initial data, the authors have used the data of 20 thermodynamic and hydraulic parameters recorded during the industrial operation of the TFP equipment and the equations of thermal balances to find the key performance indicators of the TFP. A complex of multidimensional statistical methods is used for data processing, i.e cluster and factor analysis in the Statistica software package. Results. A methodology to assess the impact of parameters on the operation efficiency of the TFP has been developed. The cluster analysis method is used to diagnose and classify the parameters under study. By the method of factor analysis, several parameters have been identified: feed water flow in the pipeline behind the TFP, differential pressure of water of the TFP, condensate flow in the pipeline behind the TFP condensate pumps, pressure drop of circulating water before and after the TFP condenser, condensate temperature of the drive turbine. The analysis of the results has showed that the identified parameters are the main components of the useful power of the turbine feed pump and the criteria for the efficiency of the TFP. Conclusions. The proposed methodology makes it possible to carry out a quantitative and qualitative assessment of operational parameters, solve the problem of processing large amounts of information, reduce the time and complexity of calculations. The results obtained are based on the developed methodology and can be used to design a statistical model using neural network technologies. This methodology can be chosen to evaluate the operation of technological systems and subsystems at thermal power plants and nuclear power plants.

Mathematical model of the natural gas absorption technological process

In the paper, a mathematical model of the absorption technological process as an object of management is obtained. This model describes the process of natural gas absorption and is designed to control this process automatically. The model is based on the equations of material and thermal balances. The results of numerical simulation confirm the sensitivity of the process behavior to automatic regulation.

Cinnamaldehyde and indocyanine green loaded lipid nanoparticles induced intracellular oxidative/thermal stress damage for effective cervical cancer therapy

The redox and thermal balances in cancer have been considered two fundamental bases for cancer progression. As a result, the development of novel action ways to disrupt these balances can therefore give potential anticancer benefits. Herein, cinnamaldehyde (CA) as a plant-derived drug which could accelerate the H2O2 generation and elevate the reactive oxygen species (ROS) level in cancer cells, is employed to elevate the ROS level of cancer cells while the indocyanine green (ICG) as a photothermal agent was co-delivered to induce oxidative/thermal stress damage to cells that provide a novel but effective way for effective cancer therapy. The CA and ICG were loaded in lipid nanoparticles to be a drug delivery system (DDS) for safe and effective drug delivery to tumour. The HeLa (human cervical cancer cell line) cells were employed as model and showed promising effects both in vitro and in vivo.