Heat Balance Model Research Articles

Reduced Carbon Consumption and CO2 Emission at the Blast Furnace by Use of Briquettes Containing Torrefied Sawdust

Lowering the carbon consumption and fossil CO2 emissions is a priority in blast furnace (BF) ironmaking. Renewable biomass is one option that can play an important role in future low-carbon ironmaking particularly in the countries rich in biomass resources. In this study, full-scale trials to investigate the impact of briquettes containing torrefied sawdust on the BF efficiency and process stability have been conducted. Briquettes containing 1.8% of torrefied pelletized sawdust (TPS), 86.2% of steel mill residues, and 12% cement with sufficient mechanical strength have been produced on industrial scale. The bio-briquettes were charged at two different rates: 37% ( ~ 39 kg/tHM) and 55% ( ~ 64 kg/tHM) bio-briquettes to the SSAB BF No. 4 in Oxelösund. The gas utilization was higher during bio-briquette-charging periods without change in pressure drop up to 55% bio-briquettes, indicating sustained shaft permeability. BF dust generation or properties did not change significantly. Measurements of the top gas composition using mass spectrometry did not indicate release of hydrocarbon from TPS in connection to the charging of bio-briquettes. Evaluation of process data has been carried out using a heat and mass balance model. The evaluation of operational data in the model indicated lowering of thermal reserve zone temperature by 45 °C and reduction in carbon consumption by ~ 10 kg/tHM when charging 55% bio-briquettes compared to the reference case. The total CO2 emission was reduced by about 33–40 kg/tHM when using 55% bio-briquettes.

Impacts of Observational Constraints Related to Sea Level on Estimates of Climate Sensitivity

AbstractReduced complexity climate models are useful tools for quantifying decision‐relevant uncertainties, given their flexibility, computational efficiency, and suitability for large‐ensemble frameworks necessary for statistical estimation using resampling techniques (e.g., Markov chain Monte Carlo). Here we document a new version of the simple, open‐source, global climate model Hector, coupled with a 1‐D diffusive heat and energy balance model (Diffusion Ocean Energy balance CLIMate model) and a sea level change module (Building blocks for Relevant Ice and Climate Knowledge) that also represents contributions from thermal expansion, glaciers and ice caps, and polar ice sheets. We apply a Bayesian calibration approach to quantify model uncertainties surrounding 39 model parameters with prescribed radiative forcing, using observational information from global surface temperature, thermal expansion, and other contributors to sea level change. We find the addition of thermal expansion as an observational constraint sharpens inference for the upper tail of posterior equilibrium climate sensitivity estimates (the 97.5 percentile is tightened from 7.1 to 6.6 K), while other contributors to sea level change play a lesser role. The thermal expansion constraint also has implications for probabilistic projections of global surface temperature (the 97.5 percentile for RCP8.5 2100 temperature decreases 0.3 K). Due to the model's parameterization of thermal expansion as an uncertain function of global ocean heat, we note a trade‐off between two ways of incorporating thermal expansion information: Ocean heat data provide a somewhat sharper equilibrium climate sensitivity estimate while thermal expansion data allow for constrained sea level projections.

Use of Heat from Wastewater

There are increasing demands on energy efficiency at all areas of life e.g. heating, cooling and hot water supply. Using waste water is meeting requirements of sustainability and environmental protection. Waste water has great energy potential. The article deals with the optimization of sewer heat exchanger and economic efficiency. Heat exchanger effect is depending on shape and geometry of heat exchanger. Also temperature of waste water affects heat exchanger effect. Usual temperature of sewage is about 20 degrees Celsius in summer and about 10 degrees Celsius in winter. Cooling for a maximum about 1 degrees Celsius and flow at least 10 litters per second is required for seamless operation. To pass requirement of minimum flow is this system suitable for bigger buildings. It is also necessary for positive economic effect. For proper design and optimization it is necessary to use three basic methods: diagnostics, heat balance calculations and modelling. Numeric simulations are made for selection of the best sewer heat recovery. Recovered heat energy was used for heating, cooling also for hot water supply. Positive economic effect is provided in case study of administrative building.

Two-converter steelmaking process for high silicon hot metal

ABSTRACT The Corex furnace can produce hot metal without using coke, but the silicon content of the hot metal is abnormal within a week of reopening the furnace. The silicon content of the abnormal hot metal is 2–5.0 mass%. In order to produce with the high silicon hot metal, a new converter steelmaking process is developed. Two converters are used in the operation process. The first converter is used to remove a large amount of silicon of hot metal, and the second converter is used to carry out the decarburization and dephosphorization process. The new converter refining process can treat the high Si content hot metal. But it also brings some new problems. The biggest problem is to control the heat balance of the molten bath. By establishing a regression model and calculation of material and heat balance of BOF 1, the addition amount of slag material and scrap can be obtained under the different conditions of hot metal. After optimization of the new operation, the end point temperature of semi steel is about 1500°C, and the scrap ratio of the whole process is higher than before. The quantity of iron bead taken by per 100 g slag is about 2.3 g, and the T.Fe of slag is less than 5 mass%. On the basis of the same processing time, the optimized new method is more accurate at temperature control of semi steel, more efficient and more reliable.

Granites and crustal heat budget

Abstract The origin of large I-type batholiths remains a disputed topic. One model states that I-type granites form by partial melting of older crustal lithologies (amphibolites or intermediate igneous rocks). In another view, granites are trapped rhyolitic liquids occurring at the end of fractionation trends defining a basalt–andesite–dacite–rhyolite series. This paper explores the thermal implications of both scenarios, using a heat balance model that abstracts the heat production and consumption during crustal melting. Heat is consumed by melting and by losses through the surface (conductive or advective, as a result of eruption). It is supplied as a basal conductive heat flux, as internal heat production or as advective heat carried by an influx of hot basalt into the crust. Using this abstract approach, it is possible to explore the role different parameters play in the balance of granites formed by differentiation of basalts or by crustal melting. Two end-member situations appear equally favourable to generating large volumes of granites: (1) short-lived environments dominated by high basaltic flux, where granites result mostly from basalt differentiation; and (2) long-lived systems with no or minimal basalt flux, with granites resulting chiefly from crustal melting.

Assessment of Climatic Conditions for Siberian Reindeer Herding on the Basis of Heat Balance Modelling

The purpose of the research is to assess suitable climatic conditions for traditional herding of reindeer by Indigenous people in different areas of Siberia. A сomputer simulation model allowed us to calculate reindeer’s heat balance according to a number of meteorological indices; it was used to assess climatic conditions in 70 localities. To show the impact of climatic conditions on reindeer’s well-being, we introduce the notion of the thermal comfort index (Kt). The best environmental conditions for reindeer are in the areas where Kt takes the highest values in winter and the lowest ones in summer. We showed the results of the reindeer heat balance computer simulation on two maps visualising the average Kt values in summer and in winter. Finally, using official statistics, we calculated the number of reindeer per 100 km2 in areas with different types of traditional reindeer herding. The territories with the largest domesticated reindeer populations per 100 km2 in the two major tundra reindeer breeding areas (Samoed and Chukchi-Koriak types of reindeer herding) are located in the regions with the relatively low value of Kt in summer and high in winter. In the taiga, Kt is relatively high in summer, and reindeer herding (Tungus and Saian types) is developed mostly in highlands, where the summer Kt is lower than in flatlands because of the vertical temperature gradient. The results obtained prove that thermal conditions are extremely important for traditional reindeer herding.

Estimation of thermal comfort felt by human exposed to extreme heat wave in a complex urban area using a WRF-MENEX model.

Thermal comfort could indicate human thermal sensation when exposed to a local meteorological condition. Because humans can suffer illness when exposed to heat or even die, it is essential to assess human comfort levels to increased temperature and to provide this information to the public. This study aims to estimate thermal comfort using the human heat balance model combined with a numerical meteorological model in Seoul mega city during the heat wave periods experienced during 2016. The gridded thermal comfort index of physiological subjective temperature (PST) was calculated based on the Man-Environment Heat Exchange (MENEX) model, which used as inputs the meteorological parameters, clothing insulations, and metabolic rates. High-resolution meteorological parameters were obtained by coupling Weather Research and Forecasting (WRF) model with Building Effect Parameterization (BEP) + Building Energy Model (BEM) using detailed urban classification. The modeling results showed that the PST distribution has a clearly heterogeneous spatial distribution during the heat wave period. The high PST values were largely found in the residential area during the day, due to the high temperature and low wind speed associated with high-density buildings, and the daily maximum PST reached a very hot level (44.1-54.0°C). Our study suggested that the human heat balance model combined with the numerical meteorological model could be used to provide more reliable information about thermal comfort to groups that may be vulnerable to the effects of heat waves in complex urban environments.

Temperature response characteristics of the thermal control system of alpha magnetic spectrometer under the operations of international space station

Abstract The alpha magnetic spectrometer (AMS) in orbit is thermally affected by operations of the international space station (ISS). According to long-term monitoring data in orbit, three kinds of the most frequent ISS operations were determined, they were locking the ISS solar arrays by themselves, changing the ISS flying attitude with locking solar arrays and rotating the ISS starboard radiator with locking solar arrays. The β interval of ( − 75 ° , − 21 ° ) in which these three kinds of ISS operations have the most significant effect on the AMS thermal environment was calculated in reference to the ISS geometric model, and the calculation result was proved to agree well with the temperature records in orbit. The AMS radiator heat balance model was found under the different ISS operations. The numerical simulations were performed to provide quantitative analysis on external heat flux on AMS radiators. Based on those, the general temperature responses of the AMS radiators following the ISS β angle under the most frequent ISS operations were analyzed accordingly. We found that the ISS operations have varying degrees of the thermal influence on the AMS radiators under the same β angle. The suggestions of controlling the possible temperature anomalies caused by the ISS operations were given according to the temperature response characteristics of the AMS components under the most frequent ISS operations.

Assessment of Climatic Conditions for Siberian Reindeer Herding on the Basis of Heat Balance Modelling.

Assessment of Climatic Conditions for Siberian Reindeer Herding on the Basis of Heat Balance Modelling.

Development and optimization of a novel controller for regenerative indirect evaporative cooler

Abstract The main characteristic of an indirect evaporative cooler (IEC) is the high dependency on ambient air conditions. To ensure stable indoor temperature and provide better thermal comfort, proper control strategy is essential. However, very limited studies report the controller used in IEC. In this paper, a novel control scheme named high-low (H-L) is proposed for regenerative indirect evaporative cooler (RIEC). Under H-L control scheme, the fans would be switched between high speed and low speed rather than completely turned off. The H-L control adopts the multi-speed technology, providing energy saving potential compared with conventional on-off control and overcome the complexity and costly of variable speed technology. The annual performance of RIEC was simulated under H-L control based on the RIEC model and dynamic indoor heat and mass balance model. The influence of low speed to high speed ratio (L/H) is discussed in order to propose an optimal L/H by considering both the thermal comfort and annual energy consumption. The results show that the H-L control can provide stable indoor temperature and satisfactory thermal comfort with Predicted Mean Vote (PMV) in the range of -0.5 to 0.5 for 76.2% of time. The optimal L/H is found to be 0.25 to 0.33 because of high thermal comfort provided and lowest energy consumption.

Theoretical modeling of combined solar chimney and water wall for buildings

In this paper, a combined solar chimney and water wall is proposed to provide ventilation as well as moderate heating to an attached room. A transient heat balance model (THBM) is established to predict the thermal performance of the combined system under mild winter conditions in Sydney, Australia. The effects of the glass panel thickness, air gap width, water column thickness, surface tinting and the relative position of solar chimney and water wall are studied respectively. The results show that the combined solar chimney and water wall is capable of providing ventilation throughout the day and night while maintaining the warmth level of the room even though it continuously draws fresh air from the ambient into the room. It is found that increasing the glass panel thickness or reducing the water column thickness enhances the thermal performance of the combined system by increasing both the room temperature and the ventilation rate. On the other hand, increasing the air gap width helps to increase the ventilation rate, but will cause the room temperature to decrease. In addition, between the two configurations, one with the water wall in front of the solar chimney (referred to as the WW-SC configuration) and the other with the solar chimney in front of the water wall (referred to as the SC-WW configuration), the ventilation rate and room temperature obtained with the SC-WW configuration are higher, and thus the latter configuration is more favorable. Furthermore, it is found that surface tinting generally degrades the thermal performance of the proposed system.

A new approach to the mathematical model of thermal energy balance

Formation of balance of thermal energy and the heat carrier for a thermal network is carried out for the purpose of increase of efficiency of work of the heat supplying organization. The standard approach proposes to write off the difference between the released and realized heat energy for heat losses. The article proposes a new approach to the formation of the balance of thermal energy and coolant. It includes statistical analysis of telemetry data relating to the released thermal energy. Heat consumption was estimated by contractual load for heating, ventilation and hot water supply. In the mathematical model of the thermal balance for each term weight coefficients were introduced. To obtain the numerical values of these coefficients, the method of least squares was used. The results of checking the adequacy of mathematical models that take into account or neglect thermal losses are presented. The obtained coefficients for the mathematical model of heat balance were used for the mathematical model of mass balance. The results can be used to predict the cost of production and transmission of heat energy and coolant, to assess the efficiency of the heat network and the formation of tariff applications for the future.

Heat recovery during treatment of highly concentrated wastewater: economic evaluation and influencing factors.

This paper assesses the economics of heat recovery from biological wastewater treatment plants (WWTPs) treating concentrated wastewater, as higher concentrations result in higher heat generation in the treatment basin. A heat balance model has been applied to calculate the amount of recoverable heat from the system and the effect of the heat extraction capacity on the economics of a heat pump installation, evaluated using the internal rate of return. A sensitivity analysis has been performed to evaluate the effect of several parameters on the economics of heat recovery in this type of WWTP: the electricity price, the price of the fuel substituted by heating savings, the investment costs, the coefficient of performance (COP) and the amount of heat extracted from the system. It was calculated that the heat pump capacity has to be high enough to recover a significant amount of heat, but low enough to improve the economics of the system. The economic performance of the system is very dependent on the energy prices of both electrical power to run the heat pump and the fuel (heat) cost substituted by the heat pump.

Thermal modeling of heat balance through embankments in permafrost regions

Permafrost is widely distributed in the northern hemisphere and permafrost degradation underneath transportation infrastructure is on-going due to many factors, such as climate change. The test site, constructed in 2008 along Alaska Highway at Beaver Creek, Yukon, Canada, provides valuable information on the long-term thermal response of permafrost underneath transportation infrastructure, to disturbances induced by constructions and climate change. The temperature data collected can also be used to calibrate thermal models to gain insight into relative effects of different factors on the sensitivity of the ground thermal regime underneath transportation infrastructure to on-going climate change. A finite-element, 2D heat conduction model, taking ice-water phase change into account, was developed based on the Beaver Creek experimental site characteristics and conditions. To increase the accuracy of the model, site-specific parameters, such as soil properties, near surface air temperature, and embankment dimension, were measured and used as input parameters. After calibration of the model, sensitivity analysis of certain input parameters, such as air temperature, embankment thickness and ground temperature, was conducted for different site conditions. The model was used to develop an engineering design chart allowing assessing the heat balance at the interface between embankment and natural ground. The heat balance analysis and the design chart are based on the results of sensitivity analysis and validated using the data from the Tasiujaq airstrip in Northern Quebec, Canada.

Reliability considerations and economic benefits of dynamic transformer rating for wind energy integration

An increasing share of renewable energy on the electricity market creates the need for economic and efficient production, operation and integration technologies, associated with the specific behavior of renewable energy sources (RES). Dynamic rating (DR) provides a possibility to apply improvements to the system both during planning and operation stages. The DR benefits are well described in various literature sources. However, DR is often focused on more efficient exploitation of power lines, not power transformers. Power transformers are costly equipment and their efficient usage and planning can have drastic effect on total costs.Our analysis focuses on the dynamic transformer rating (DTR) for wind energy applications. The main objective is to study reliability effects of DTR from the component perspective. We utilize existing knowledge about transformer heat balance models from IEC and IEEE standards to obtain information on the loss of life (LOL) of the transformer under investigation and propose possible improvements for the system in question. The method can be employed for identifying the appropriate transformer size by taking into account ambient temperature and load variations and then overloading the transformer beyond nameplate ratings. The reliability of the proposed application is ensured by calculating the risk of overloading the transformer for each day of the year. A risk of overloading is quantified as LOL of the transformer. The risk is presented as a function of ambient temperature and duration of an overload. The final step consists of an economic analysis, which demonstrates economic benefits of DTR application.

Bulk temperature prediction of a two-speed automatic transmission for electric vehicles using thermal network method and experimental validation

Nowadays, the development of electric vehicle equipped with a two-speed automatic transmission has become a hotspot. As well known, the automatic transmission operates with power loss including gear meshing loss, bearing loss, and oil churning loss. This paper focuses on the bulk temperature prediction of a two-speed automatic transmission using thermal network method. An integrated model, including an efficiency model and a heat balance model, is proposed, which makes it possible to predict power loss, bulk temperature, and temperature distributions under different conditions. In the efficiency model, each part of power losses from gear meshes is studied to calculate the summation of mechanical power losses in the transmission, including losses of gear meshing, bearing and oil churning. In the heat balance model, the entire gearbox is divided into elements with a uniform temperature connected by thermal resistances which account for conduction, convection, and radiation, based upon the first law of thermodynamics for transient conditions. The effectiveness of bulk temperature prediction using thermal network method is validated by the comparison between simulation results and the experimental data. Consequently, this study on heat transfer characteristics, thermal characteristics, and bulk temperature prediction of the two-speed automatic transmission has significant academic and application values.

Innovative energy-saving technology in refrigerated containers transportation

The article presents the concept of innovative technology used to store refrigerated containers in port terminals or on ships that aims to reduce the energy consumption. The idea of new technology to store refrigerated containers was described on port’s terminal example. According to set assumptions, the mathematical heat-balance model of containers stored on yard has been proposed to calculate the savings, as well as the effects of such solution usage have been shown. The results of preliminary calculations were compared to results of experimental verification conducted in the laboratory and based on the approximate model. Obtained results both calculations and experimental verification proved the effectiveness of proposed concept; however, the experimental results indicate smaller savings, then the calculated one.

Study of influence of boundary conditions on deformation and stresses in a cooled piston of a diesel engine – part A - mathematical models

The paper presents influence of boundary conditions on mechanical and thermal stresses of an oil cooled piston in diesel engine Scania DC09 074A and its deformation due to high combustion pressure and variable temperature. Due to different fixing of the pin in the piston hub the deformation of the piston shape and von Misses stresses differ at the same boundary conditions. This part of paper describes mathematical model of the piston load especially of heat transfer to wall taking into account three elements: convection, radiation and conductivity of the piston material. Calculations of the piston loads were carried out by using 0D mathematical model at assumption of the Vibe combustion model and the Woschni heat transfer model for homogenous mixture. For precise determination of the gas temperature in the combustion chamber the CFD technique recently is used and for that case the simulation of compression, combustion and expansion processes was carried out by using the program Fluent. The numerical calculations were done for two kinds of fuel: diesel oil and CNG due to possibility of changing the oil fuelling system into gaseous fuelling system. In order to proper work of CNG engine the compression ratio should be decreased. This was done by reducing the volume of the combustion chamber. Most calculations have done by researchers at assumption that the piston hubs are fixed, but it is not right assumption. In summary the paper gives indications how to set boundary conditions for “floating” piston pin. The paper presents shortly mathematical model of heat balance in the piston and FEM solution of stresses and deformation which are based on strains. This study is an introduction to calculations showed in the part B.

Development of a bioclimatic wind rose tool for assessment of comfort wind resources in Sydney, Australia for 2013 and 2030.

This study assessed the effect of wind on human thermal comfort by preforming outdoor urban climatic comfort simulations using state-of-the-art heat-balance models of human thermo-physiology (Universal Thermal Climate Index-UTCI). A series of simulations for computing "wind cooling potential" have been performed using the UTCI index temperatures. The comfort cooling effect of wind has been estimated by modelling with wind taken into account, and under calm wind (0.05m/s) (ΔUTCI). A novel wind rose biometeorological data visualisation tool that integrates an additional thermal comfort dimension into the conventional climatology wind rose visualisation was developed in this study. The new wind rose graphic tool identifies "predominant" wind directions, and whether or not they are "desirable" from the human thermal comfort point of view. This tool's utility lies in its identification of the optimal building orientation in its surrounding urban morphology, based on the cooling potential of wind resources when enhanced ventilation is desirable for thermal comfort.

Accelerated carbonation of waste incinerator bottom ash in a rotating drum batch reactor

Accelerated carbonation is known to improve the leaching behaviour and geotechnical properties of waste incineration bottom ash (BA). Regarding process implementation on the industrial scale dynamic reactor configurations may be particularly suited since they enhance the mass exchange between gas and solid. Here we evaluated the influence of fundamental parameters on accelerated carbonation of BA in a rotating drum batch reactor equipped with an automated CO2 supply at close to atmospheric pressure conditions. Firstly, the effect of rotation speed and reactor fill level on the solids motion was studied. Secondly, the effects of CO2-concentration, fill level, and moisture on BA carbonation were investigated. Evaluation was based on the observed CO2 uptake, self-heating, and BA leachability. The bed behaviour of BA strongly differed from that of standard materials and was more affected by fill level than by rotation speed. The fill level was not a limiting factor for BA carbonation within the tested range (7–45 vol.-%). Both the CO2 uptake rate and the final level of carbonation increased as the CO2-concentration was raised from 15 to 75 vol.-%. A close relationship between CO2 uptake and reactor temperature was confirmed by benchmarking a heat balance model against the carbonation enthalpy. Carbonated BA exhibited a strongly decreased mobility of Pb and Zn as compared to fresh BA. The leaching behaviour of BA could be improved such as to comply with the German landfill ordinance for non-hazardous waste.