Heat Balance Model Research Articles

Development and workflow of a separation process for optimum design: A case of phenylenediamine

AbstractAn industrial project based upon the multi‐scale objective‐oriented process development (MOPD) method for developing an optimum process for separating phenylenediamine (PDA) isomers was executed. This article reports the first four (4) steps of that project. In the first step, the solution for this separation problem was conceptualized. It is a distillation‐crystallization‐hybrid process. The second step is to validate the concept experimentally from the thermodynamic point of view followed by kinetic considerations. It was found that a 2‐stage crystallization is required to purify the main product isomers to the desirable specification that is higher than 99.5 mol%. A heat and material balance model was then constructed for analyzing and optimizing various design variables, also used to understand the operability of the process. Finally, with proper HAZOP analysis and detailed engineering, the pilot unit was designed. Throughout the project, all exercises and efforts are well focused with clear objectives, hence there are minimum detours on the execution; furthermore, the clear objectives enhanced the communications among various disciplines tremendously. It is a valuable asset for senior management in the allocation of resources and budgets.

Developing a new adaptive heat balance model to enhance thermal comfort predictions and reduce energy consumption

Accurate thermal comfort prediction is essential for enhancing both thermal comfort and energy efficiency in buildings. The heat balance and adaptive models, while widely used, have been often questioned in relation to their strengths and limitations. To overcome these challenges, a comprehensive understanding of both the physical parameters influencing heat exchange and occupants’ adaptive capacities is essential.This study introduces an analytical method to formulate a new adaptive heat balance model, the adPMV, which integrates the strengths of both models considering various parameters influencing thermal perception. The model integrates the PMV with an adaptive factor associated with the running mean outdoor temperature, in line with adaptive theory.Tested on 1377 samples from European university classrooms, the adPMV demonstrates enhanced accuracy (MAE=0.74, RMSE=1.01, MBE=-0.11) compared to PMV and other adaptive heat balance models. Validation on naturally ventilated university classrooms from ASHRAE’s databases further confirms promising results, showcasing reduced error indices (MAE=0.68, RMSE=0.81, MBE=-0.03). Notably, using adPMV setpoints not only improves thermal sensation prediction accuracy but also leads to a substantial reduction in heating demand, reaching up to 40 %.The adaptability of this model to different contexts, such as building types, climates, and HVAC system operations, presents it as a versatile tool for exploring adaptive principles.

Simulation of urban surface temperature and surface heat balance in the Tokyo metropolitan area

This study aimed to propose a method for simulating ground surface temperature and surface heat balance using thermal infrared remote sensing and an urban surface heat balance model and to conduct a simulation in the Tokyo metropolitan area. Previous studies have typically employed ground surface temperatures obtained through satellite remote sensing to analyze urban thermal environments. However, these studies were limited to using surface temperature data available only at the time of satellite passage. Therefore, in this study, we conducted a simulation for the Tokyo metropolitan area by integrating a one-dimensional heat balance model with ground surface temperatures observed by satellites. The novelty of this study lies in the utilization of parameters related to heat balance obtained through calculations of physical processes, as opposed to relying on empirical formulas or parameters. Consequently, realistic ground surface characteristics, including parameters such as evaporation efficiency and thermal inertia essential for the simulation, were derived by this combined method. Furthermore, diurnal variations in ground surface temperature distributions were accurately represented by using realistic surface temperature data based on satellite remote sensing, considering the effect of heat storage in urban areas—an aspect challenging to reproduce using conventional local meteorological models.

Machine-Learning-Based Kinetic-Free Hybrid Gray-Box Model to Predict Sulfuric-Acid-Catalyzed Esterification Reaction.

The sulfuric-acid-catalyzed esterification reaction of 2-butanol and propionic anhydride is a vital industrial process. In this paper, several experiments are conducted via reaction calorimetry to validate that both sulfuric and propionic acids have discernible catalytic effects on the reaction. This finding complicates the accurate description of the reaction kinetics through traditional methods. So this paper turns to a kinetic-free black-box model, Gaussian process regression (GPR) model via 24 experiments, as a more adaptable approach. Besides, the best GPR model is combined with traditional heat balance model to generate a hybrid gray-box model, which can give complete knowledge of reaction process. The hybrid gray-box model finally achieves maximum root-mean-square error (RMSE) of 0.0069 for conversion, 0.6535 for temperature, and 10.6087 for heat flow rate, underscoring its pretty good predictive ability.

Development of an Activity Coefficient Model for the Aqueous Amino Acid Solution

AbstractThe enthalpy and solubility of aqueous amino acid solutions are essential thermodynamic properties for the modeling of heat and mass balance, and these properties can be estimated by considering the activity coefficient in thermodynamic calculations. In this study, the parameters of a non‐random two‐liquid model were identified using heat capacity and solubility data together to calculate the acceptable activity coefficient for an aqueous amino acid system. As a result, a highly accurate activity coefficient model of an aqueous amino acid solution was developed, and inaccurate alternative solutions regressed with heat capacity or solubility only can be avoided.

Implications of heat exchange for a free-living endangered marsupial determined by non-invasive thermal imaging.

We used thermal imagining and heat balance modelling to examine the thermal ecology of wild mammals, using the diurnal marsupial numbat (Myrmecobius fasciatus) as a model. Body surface temperature was measured using infra-red thermography at environmental wet and dry bulb temperatures of 11.7-29°C and 16.4-49.3°C, respectively; surface temperature varied for different body parts and with environmental temperature. Radiative and convective heat exchange varied markedly with environmental conditions and for various body surfaces reflecting their shapes, surface areas and projected areas. Both the anterior and posterior dorsolateral body areas functioned as thermal windows. Numbats in the shade had lower rates of solar radiative heat gain but non-solar avenues for radiative heat gain were substantial. Radiative gain was higher for black and lower for white stripes, but overall, the stripes had no thermal role. Total heat gain was generally positive (<4 to >20W) and often greatly exceeded metabolic heat production (3-6W). Our heat balance model indicates that high environmental heat loads limit foraging in open areas to as little as 10min and that climate change may extend periods of inactivity, with implications for future conservation and management. We conclude that non-invasive thermal imaging is informative for modelling heat balance of free-living mammals.

Modeling of an ammonia decomposition membrane reactor including purity with complex geometry and non-isothermal behavior

A fully coupled mass, momentum, and heat balance model was constructed in axisymmetric 2D for an ammonia decomposition packed bed membrane reactor using computational fluid dynamics and compared to experimental results for a Pd/YSZ membrane surrounded by Ru/Al2O3 catalyst. In addition to the complex geometry of the fittings used to seal the membrane, a total of 16 design variables were found to be required to fully specify the tubular integrated membrane reactor. Aside from emissivity, all input variables were experimentally determined or obtained from tabulated material property data, and no correlation fitting was performed. Experimental data were obtained for temperatures of 450 °C–530 °C, trans-membrane pressures of 0 MPa–0.4 MPa, and gas hourly space velocity feed rates of 375 h−1 to 620 h−1, chosen such that the ammonia conversion and hydrogen recovery spanned a broad range with maximum values of 99.9 % conversion or 88 % recovery with greater than 99.8 % purity. The model was able to successfully determine the ammonia conversion and hydrogen recovery of the experimental results to within an average error of −0.31 % and −2.4 %, respectively. The purity was determined within +0.0071 %, but experimental detection limitations of the impurities affected the fit between experiment and model of the N2 and NH3 in the permeate. The sensitivity of the model to various assumptions and input variables was explored. Notably, the inclusion of purity is a rarity in published models and this study adds to the discussion on the ability of modeling to predict high purity results. Compared to the relatively minimal effects of using the full geometry, the inclusion of heat transfer and radial diffusion were critical in successfully predicting the experimental results.

Improving the energy effectivity of biomass drying for utilisation in energy systems by combining convective and contact drying

The article deals with reducing the energy consumption of biomass drying before combustion in energy plants. The combination of traditionally used convective hot air drying and less applies contact drying is analyzed. To determine the basic drying characteristics, the experiments on a contact dryer and a convective hot air dryer were carried out with wet wood chips. A heat balance model of a system with serial connection of a convective air dryer and a contact dryer was compiled. In the model, the utilization of condensation heat from the waste vapor leaving contact drying to preheat the drying air for convective drying was considered. Based on these results, the system could be optimized to achieve the lowest energy consumption, drying time, and dryer sizing. This solution can significantly improve the energy efficiency of drying moist biomass before combustion from 3.29 and 2.76 MJ per kg of evaporated water for only convective drying and only contact drying, respectively, to 1.48 or 1.33 MJ per kg of evaporated water, depending on the order of the dryers in their connection.

Deep learning-assisted multi-objective optimization of coke dry quenching system efficiency

Coke dry quenching is a promising technology for energy saving and environmental protection in the industrial sectors. Prediction of system efficiency index (SEI) and dynamic adjustment of operating parameters are essential to ensure high system efficiency. In this study, a deep learning-assisted multi-objective optimization framework was proposed to improve coke quenching efficiency and steam production simultaneously. Firstly, numerous on-site process parameters were collected as the data basis for subsequent model construction, and a system-level heat balance model was established and validated for real-time calculation of coke burning loss rate. Then, an attention-based one-dimensional convolutional neural network was developed as a data-driven surrogate model to establish the mapping relationship between the operating parameters and SEI. Finally, the Non-dominated Sorting Genetic Algorithm II was combined with the Technique for Order of Preference by Similarity to Ideal Solution to rapidly identify the optimal operating parameters under different loads. The optimization results also provided a new insight into the system dynamic characteristics. The results show that the surrogate model can swiftly and precisely predict SEI, with R2 exceeding 0.9. Compared with initial operating conditions, the optimal decision scheme has improved SEI by 82 %, with the optimal coke burning loss rate and main steam flow rate of 0.56 % and 83.6 t/h, respectively. This work will provide valuable decision aids for technicians to reach the desired system efficiency.

Unbalancing mean radiant temperature and air temperature

Radiant heating and cooling systems promise to provide heat transfer over large surface areas to enable lower temperature supply improving both supply efficiency and user comfort. Radiant panels provide both radiant and convective heat transfer. We investigate the balance of the heat transfer occurring via radiation and convection. A commonly referenced benefit of radiant panels is that the radiant heating or cooling delivered to occupants allows thermal perception to remain neutral while lowering or raising air temperatures, which in turn reduces heat losses or gains through the facade. In our previous work on radiant systems, we have observed that very rarely do air temperatures actually get set to more ideal temperatures alongside the radiant panels. Using the framework of a recent study of an office space in Singapore we present a simulation showing the breakdown of radiant and convective heat and the resulting air temperature in a simple heat balance model. We then use a computational fluid dynamics (CFD) model and analytical model to observe the relationship between air temperature and mean radiant temperature (MRT) through space. We find that it can take up to 40 kW of additional heat gain to successfully decouple the air temperature from the MRT generated by the panel by more than 2 °C. We also show that in the CFD model, while the air temperature and MRT remain relatively tightly coupled, the vertical spatial variation of MRT is significant, changing by more than 2 °C across the space from floor to ceiling.

Dynamic comfort criteria – A possible solution to the conflict between heat balance and adaptive thermal comfort models

Physiologists typically assume that optimal thermal comfort can only be achieved by minimizing thermoregulatory efforts. People are thus believed to be thermally comfortable with a mean skin temperature of 33–34 °C and minimized sweating rate at a low metabolic rate. Many heat balance comfort models are established based on these fixed comfort criteria. However, occupants’ thermal requirements are found to be more flexible and dynamic because of physiological and psychological adaptions. In this study, dynamic comfort criteria (DCC) are proposed to consider the adaption in the PMV model. Occupants tend to accept a lower skin temperature in a cold climate and a slightly higher sweating rate in a hot climate. We provide two methods to infer DCC based on ASHRAE thermal comfort database II. One is to develop a generalized DCC that can be applied globally. Another is to use Bayesian calibration to develop a customized DCC that further localizes the thermal requirements. With DCC, the deficiency of the PMV and the adaptive model can be largely eliminated. Unlike PMV, the model with DCC performs consistently in different operation modes. DCC is conceptually different from actual physiological responses, although they can sometimes be close to each other in values. The study paves the road for unifying comfort theories and equipping traditional comfort models with the ability to re-learn.

Optimal Placement of Heat Exchangers in a Carbon Capture-Based Ventilation System

Achieving acceptable air quality levels in indoor spaces by regulating the concentrations of H2O and CO2 is important for occupant health. Conventional techniques rely on supplying dehumidified outdoor air to dilute these species to within their healthy ranges. Typically, the outdoor air dehumidification is conducted using vapor compression cooling either as standalone systems or integrated with desiccant dehumidifiers. These methods are known to be energy intensive, especially in hot and humid climates. Ventilation systems using indoor air with adsorption-based CO2 capture are thus proposed. These systems use adsorbent packed beds to dehumidify and decarbonize the indoor air before it is sensibly cooled and supplied to the space. For energy efficient operation of these systems, heat recovery units are necessary. In this work, heat and mass balance models were developed and used to determine the optimal placement location of the heat recovery units. It was found that a heat exchanger preceding the decarbonization bed increased the MOFs capacity, resulting in 33 % lower mass requirements. This was accompanied by a reduction in the thermal and electrical energy consumption by 43.5 % and 25 %, respectively, with respect to the configuration where the heat exchanger was placed after both air treatment systems.

An Improved Shallow Water Temperature Model for An Australian Tidal Wetland Environment Using Publicly Available Data

Larval mosquito development is directly impacted by environmental water temperature. Shallow water less than 1 m deep is a common larval mosquito habitat. Existing mathematical models estimate water temperature using meteorological variables, and they range in complexity. We developed a modification of an existing one-layer heat balance model for estimating hourly water temperature and compared its performance with that of a model that uses only air temperature and water volume as inputs and that uses air temperature itself as an indicator of water temperature. These models were assessed against field measurements from a shallow tidal wetland—a known larval habitat—in southwest Western Australia. We also analysed publicly available measurements of air temperature and river height to determine whether they could be used in lieu of field measurements to allow cost-effective long-term monitoring. The average error of the modified version of the heat balance equation was −0.5 °C per hour. Air temperature was the second-best performing method (x¯ error = −2.82 °C). The public data sources accurately represented the onsite water temperature measurements. The original heat balance model, which incorporates a parameterisation of evaporative heat flux, performed poorly in hot, dry, windy conditions. The modified model can be used as an input to larval mosquito development models, assisting Local Government Environmental Health officers to determine optimal mosquito development periods and the timing of mosquito monitoring activities to enhance mosquito control.

A theoretical approach to evaluate the effect of hydrocarbon and CO2 injection on blast furnace raceway: step towards reduction of CO2 emission

ABSTRACT A novel raceway heat and material balance model is developed considering all physico-chemical phenomena surrounding the raceway of the blast furnace (BF). This model is unique, as it considers reactions based on thermodynamics and determines important parameters such as raceway adiabatic flame temperature (RAFT), bosh gas properties, raceway coke rate etc. Importantly, the model also predicts blowing parameters in case of known RAFT and permeability of the furnace. This paper focuses on the raceway regime only considering the effect of different injectants, H2, CO, CH4, CO2 and coke oven gas (COG). Firstly, the paper describes the modelling approach, based on thermodynamic, heat and material balances. The first part of the paper quantifies the effect of injectants on the raceway keeping the blowing parameters constant, whereas second part presents the changes of raceway properties as well as blowing parameters keeping RAFT and permeability of the furnace constant.

Influence of Oxy-Fuel Lance Parameters on the Scrap Pre-Heating Temperature in the Hot Metal Ladle

As one of the vital ways to improve the converter heat balance and increase the scrap ratio, scrap pre-heating technology has attracted much attention from researchers. The aim of this paper is to reveal the effect of the oxy-fuel lance parameters on the temperature field, flow field, and scrap pre-heating temperature in the ladle by means of numerical simulations. For this, a three-dimensional mathematical model containing the turbulence model, the porous medium heat balance model, and other models has been developed. The research results show that the rational and correct choice of gas flow rate, lance position, and nozzle angle has an important influence on the temperature field and the average scrap temperature. When the gas flow rate increases, the internal annular combustion zone of the scrap gradually expands, the cold zone at the bottom of the scrap continues to decrease, and the average scrap temperature keeps increasing. When the gas flow rate is 5000 m3/h, and the average scrap temperature reaches 1197 K, the pre-heating time is 9.98 min. Lowering the oxy-fuel lance position helps to reduce the cold zone at the bottom of the scrap and increases the average temperature in the cold zone. Reasonable selection of the nozzle angle is conducive to improving the uniformity of the flow field. When the angle of the nozzle is 15°, the gas circulation zone is the largest, and the time to reach an average scrap temperature of 1197 K is the shortest.

Rücktitelbild Chem. Ing. Tech. 5/2023

Chemie Ingenieur TechnikVolume 95, Issue 5 p. 800-800 Back CoverFree Access Rücktitelbild Chem. Ing. Tech. 5/2023 First published: 25 April 2023 https://doi.org/10.1002/cite.202370508AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract A Kinetic & Heat Balance Model for Anionic Polymerization. Copyright: Felix Kandelhard Anionic polymerization is an established method for the synthesis of block copolymers. Due to the high reaction rates, a good knowledge of the process and its heat generation is of great importance for safe reaction control. The developed model, validated based on the block-co-polymerizations of styrene and isoprene, enables a prediction of the temperature profiles and the molecular weight distributions of the synthesized polymer. As a tool to identify the influence of various process parameters and the composition of the reaction mixture on the polymerization, it can be very useful in the optimization of anionic batch polymerizations. F. Kandelhard, P. Georgopanos, Chem. Ing. Tech. 2023, 95 (5), 754-760. DOI: 10.1002/cite.202200205 Volume95, Issue5Special Issue: Reaktionstechnik und Wärme‐ und StoffaustauschMay 2023Pages 800-800 RelatedInformation

A Kinetic and Heat Balance Model for Anionic Batch Block Copolymerization of Styrene and Isoprene

AbstractAnionic polymerization is an established process for the synthesis of well‐defined block copolymers. Due to the high reaction rates, a good knowledge of the process and its heat generation is of great importance for safe reaction control. This is to be achieved by the development and validation of a combined kinetic and heat transport model. The validation of the combined model was based on the experimentally anionic homo‐polymerization of styrene that was expanded for the block co‐polymerization of styrene and isoprene carried out in cyclohexane in batch reactors.

Modeling and Experimental Study on Drying Characteristics of Corn Particles with Hot Air in Downward Moving Bed

With regard to drying fresh grain prior to storage, the drying tower with a downward moving bed with hot air is often used, which always has high energy consumption during operation. To optimize the operation, according to the actual operating parameters of a corn drying tower with hot air, a heat balance model was established, and the heat transfer between the hot air and corn flow in a downward moving bed was analyzed. Since the downward moving time is short, the heat absorbed by corn significantly depends on the heat transfer coefficient, mainly the convective heat transfer, between the hot air and corn surface. To determine the convective heat transfer coefficient, a hot air drying experimental system for corn grains was established, and the effects of hot air temperature and wind speed on the central temperature and moisture content of corn grains were analyzed. Utilizing the heat balance model, the convective heat transfer coefficients between corn particles and hot air were calculated. The total convective heat transfer coefficients are in the range of 39.4–53.8 W/m2 · K. With an average value of 46.7 W/m2 · K, drying energy efficiencies in different drying zones in the drying tower were calculated, and the accuracy of the model was verified by the operation data. Due to the high inlet temperature of hot air, the maximum energy efficiency of the first zone is 60.15%, whereas when the temperature of hot air in the second drying tower is 140 °C, the energy efficiency is only 41.97%. Therefore, under the premise of ensuring the drying rate, the temperature of hot air of the second zone should be appropriately reduced to improve the whole drying energy efficiency.

Quantify the magnitude and energy impact of overcooling in a sub-tropical campus building

Overcooling leads to unnecessary energy wastes and low thermal satisfaction rate. This study investigates the magnitude and energy impact of overcooling in a sub-tropical university campus. We deployed an environmental sensing network with 577 temperature sensors across the campus, collecting data every 30 min for 2 years. We derived the suitable temperature set-point using heat balance model and adaptive comfort model. We compared the actual temperature measurements with the set-point recommended by thermal comfort theories and standards in different jurisdiction. We found the indoor temperature measured in the campus buildings are averagely 2.5 °C lower than the comfort temperature recommended by the heat balance and adaptive comfort theories. The magnitude of overcooling are inhomogeneous: offices and interiors thermal zones suffer more from overcooling compared with other functional spaces and exterior thermal zones. And overcooling is more severe in the morning and during working days. Next, we use building energy simulation engine EnergyPlus to quantify the energy impact of overcooling. The simulation results show that overcooling in the campus lead to 34% more annual cooling energy consumption and 20% higher peak cooling load. Considering the increasing demand for space cooling due to global warming, mitigating overcooling provides a non-negligible opportunity to reduce cooling energy consumption and associated carbon emissions without compromising comfort.

Process hazard assessment of energetic ionic liquid with kinetic evaluation and thermal equilibrium

With the continuous development of battery technology, there are new research investments in materials of various parts. In the field of electrolytes, ionic liquids (IL) are considered to be excellent electrolytes and have been widely studied in distinct energy fields. However, it is necessary to pay attention to the safety characteristics of ionic liquids at high temperature due to the application of energy, but there is little research on the reaction and kinetics of ionic liquids. To ensure the safety of ionic liquids, such as high temperature, the common ionic liquid 1-Ethyl-3-methylimidazolium nitrate ([Emim] NO3) was selected for analysis. The exothermic mode is obtained from the data of differential scanning calorimetry. The basic reaction parameters of [Emim] NO3 were determined with thermodynamic equation simulation. For ionic liquids in the actual situation, consider adding a heat balance model to estimate its temperature change pattern and find out the hazard temperature and related safety parameters. Temperature changes were estimated by constructing 25.0 g and 50.0 g packages to simulate material reactions and heat transfer in the external environment. The results showed that [Emim] NO3 had shorter TMRad and TCL (<1 day) when the temperature was above 180 °C.