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Applying Dynamic U-Value Measurements for State Forecasting in Buildings 应用动态 U 值测量进行建筑状态预测
IF 0.6 Q4 PHYSICS, APPLIED Pub Date : 2023-12-01 DOI: 10.2478/lpts-2023-0047
J. Telicko, A. Jakovics
Abstract In the present day, monitoring and automated control stand as pivotal factors for the energy-efficient and comfortable operation of buildings. As the demand for indoor climate control grows, building management systems have become more intricate, making their control challenging due to the increasing number of controllable elements. Replacing manual human analysis of complex systems can be achieved through the utilization of algorithms like model-based control. It is important to note that performance of this method usually relies on the accuracy of neural network-based building state forecasts. Studying the internal dynamics of climate as influenced by temperature changes necessitates a brief record of measurements, whereas evaluating structural modifications through moisture transfer demands data covering a more extended period. Neural networks such as Long Short-Term Memory have the potential to lose information within lengthy time-series data, and the intricate nature of moisture transfer further adds complexity to the task of approximating functions, ultimately leading to a reduction in energy efficiency. In order to improve the precision of indoor climate predictions, our suggestion involves not only assessing changes in temperature but also considering alterations in U-values triggered by temperature variations and moisture transfer. Our preliminary assessment of the influence of U-value, conducted through numerical simulations using WUFI6, exposes variations of up to 10 % of U-value in certain scenarios. Dealing with these computations in real time using physical models proves to be demanding due to computational requirements and limited data availability. To tackle this issue, we present an innovative preprocessing approach for on-the-fly evaluation of U-values. Empirical trials involving three years of monitoring data indicate that the suggested technique led to an approximate 8 % reduction in the average mean squared error of climate predictions based on neural network models, in specific instances.
摘要在当今社会,监控和自动化控制是建筑节能和舒适运行的关键因素。随着室内气候控制需求的增长,建筑管理系统变得更加复杂,由于可控元素数量的增加,使其控制变得具有挑战性。通过使用基于模型的控制等算法,可以取代人工对复杂系统的分析。值得注意的是,这种方法的性能通常依赖于基于神经网络的建筑状态预测的准确性。研究受温度变化影响的气候内部动力学需要一个简短的测量记录,而通过水分转移评估结构变化则需要覆盖更长的时期的数据。像长短期记忆这样的神经网络有可能在长时间序列数据中丢失信息,而水分转移的复杂性进一步增加了近似函数的复杂性,最终导致能源效率的降低。为了提高室内气候预测的精度,我们建议不仅要评估温度变化,还要考虑温度变化和水分转移引起的u值变化。我们通过使用WUFI6的数值模拟对u值的影响进行了初步评估,揭示了在某些情况下u值的变化高达10%。由于计算需求和有限的数据可用性,使用物理模型实时处理这些计算被证明是非常苛刻的。为了解决这个问题,我们提出了一种创新的u值动态评估预处理方法。涉及三年监测数据的经验试验表明,在特定情况下,所建议的技术使基于神经网络模型的气候预测的平均均方误差减少了大约8%。
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引用次数: 0
Density-Based Topological Optimization of 3D-Printed Casts for Fracture Treatment with Freefem Software 利用 Freefem 软件对用于断裂处理的三维打印铸件进行基于密度的拓扑优化
IF 0.6 Q4 PHYSICS, APPLIED Pub Date : 2023-12-01 DOI: 10.2478/lpts-2023-0050
K. Kokars, A. Krauze, K. Muiznieks, J. Virbulis, P. Verners, A. Gutcaits, J. Olins
Abstract 3D printed plastic casts can be used for healing bone fractures. The main requirements for these cases are: they should be light, require little printing time, have good mechanical properties, and ensure proper skin ventilation. We present a density-based topology optimization algorithm for obtaining optimal cast shapes that fulfil these requirements. The algorithm uses a linear stress model and simplified boundary conditions to model the contact problems. The cast shapes were optimized against the influence of several sharp corners. The parametric studies showed that the mass of optimized casts was reduced by 20 %–25 % in comparison with original industrial casts, and the printing time is reduced by 1.4–1.7 h for the largest cast. A major model drawback is the use of 3D numerical volume to model the density distribution. The density distribution should be homogenized across the cast layer. The overhang problem should also be addressed. We also suggest that the cast producers collect more experimental data on the cast breakages for a better calibration of the numerical model.
3D打印塑料铸件可用于骨折愈合。这些外壳的主要要求是:它们应该很轻,需要很少的打印时间,具有良好的机械性能,并确保适当的皮肤通风。我们提出了一种基于密度的拓扑优化算法,以获得满足这些要求的最佳铸件形状。该算法采用线性应力模型和简化的边界条件来模拟接触问题。针对几个尖角的影响,优化了铸件形状。参数研究表明,优化后的铸件质量比原工业铸件降低了20% ~ 25%,最大铸件的打印时间缩短了1.4 ~ 1.7 h。一个主要的模型缺陷是使用三维数值体积来模拟密度分布。密度分布应均匀分布在铸层上。悬空问题也应加以解决。我们还建议铸造生产商收集更多的铸造破损实验数据,以便更好地校准数值模型。
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引用次数: 0
Building Ventilation Optimization Through Occupant-Centered Computer Vision Analysis 通过以住户为中心的计算机视觉分析优化楼宇通风
IF 0.6 Q4 PHYSICS, APPLIED Pub Date : 2023-12-01 DOI: 10.2478/lpts-2023-0045
J. Telicko, K. Bolotin
Abstract Buildings consume about 40 % of all energy. Ventilation plays a significant role in both the energy consumption of buildings and the comfort of occupants. To achieve energy efficiency and comfort, smarter ventilation control algorithms can be employed, such as those with feedback based on CO2 levels. Furthermore, by knowing the current number of people in a space, ventilation can theoretically be adjusted to maintain a constant CO2 level without wasting energy when people are not present. An additional benefit of such control could arise due to occupants’ habits. For example, if a person senses elevated CO2 levels, even if the ventilation system has started operating more intense, they might choose to open a window, potentially compromising energy efficiency. Therefore, if the control algorithm were to maintain a constant CO2 level, occupants may be less likely to open windows. In our work, we explore a model in combination with a custom monitoring system based on computer vision to implement such control. The monitoring system combines outside and inside CO2 sensors with precise people counting based on computer vision to provide data to the model. The model relies on the mass balance equation for CO2 and considers the historical data of the number of occupants and their activities to estimate the overall CO2 generation in indoor spaces. The results suggest that the model can effectively forecast CO2 dynamics with an absolute deviation of 40 ppm. However, it was observed that the analysis of the actual air exchange level could be compromised by several factors.
建筑消耗了大约40%的能源。通风在建筑物的能耗和居住者的舒适度方面都起着重要的作用。为了实现能源效率和舒适度,可以采用更智能的通风控制算法,例如基于二氧化碳水平的反馈算法。此外,通过了解当前空间中的人数,理论上可以调整通风以保持恒定的二氧化碳水平,而不会在没有人在场时浪费能源。这种控制的另一个好处是由于居住者的习惯。例如,如果一个人感觉到二氧化碳浓度升高,即使通风系统已经开始更强烈地运行,他们也可能会选择打开窗户,这可能会降低能源效率。因此,如果控制算法保持恒定的二氧化碳水平,居住者可能不太可能打开窗户。在我们的工作中,我们探索了一个结合基于计算机视觉的自定义监控系统的模型来实现这种控制。监测系统结合了外部和内部的二氧化碳传感器以及基于计算机视觉的精确人数统计,为模型提供数据。该模型依赖于二氧化碳的质量平衡方程,并考虑了居住者数量及其活动的历史数据,以估计室内空间的总体二氧化碳排放量。结果表明,该模型能有效预测CO2动态变化,绝对误差为40 ppm。但是,有人指出,对实际空气交换水平的分析可能受到若干因素的影响。
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引用次数: 0
Influence of Surface Waves on Liquid-to-Gas Mass Transfer in Molten Silicon 表面波对熔融硅中液气传质的影响
IF 0.6 Q4 PHYSICS, APPLIED Pub Date : 2023-12-01 DOI: 10.2478/lpts-2023-0049
G. Zageris, V. Geža, S. Pavlovs
Abstract The paper focuses on the numerical analysis of the mass transfer of impurities from the wavy surface of molten silicon to the gas phase. The mathematical model is described herein, with the modelling of a wavy silicon melt surface being done with the moving mesh technique. The model employs assumptions about the mass transfer process on the surface, namely, that it can be modelled with effective diffusion across the interface. The assumption is verified against limited experimental data for a stationary melt surface, and reasonable agreement is obtained. Thereafter, numerical studies are undertaken for a wavy melt surface. The dependence of impurity removal rate on the wave amplitude, wavelength and frequency is analysed. It is shown that the waves on the surface of the liquid increase the mass transfer rate in a certain parameter range. Finally, results are analysed to find an explanation for this increase and to determine technological factors that impact it. Surface enlargement due to waves and altered flow patterns near the silicon melt are determined as potential reasons for the improved impurity removal rate. A dimensionless criterion for the minimal wave amplitude required to obtain improved impurity removal is found and discussed.
摘要:本文着重对硅液波纹表面杂质向气相的传质过程进行了数值分析。本文描述了用移动网格技术对波浪状硅熔体表面进行建模的数学模型。该模型采用了关于表面传质过程的假设,即,它可以通过界面上的有效扩散来建模。用有限的固定熔体表面实验数据验证了这一假设,得到了合理的一致性。然后,对波浪状熔体表面进行了数值研究。分析了杂质去除率与波幅、波长和频率的关系。结果表明,在一定的参数范围内,液体表面的波增加了传质速率。最后,对结果进行分析,以找到这种增长的解释,并确定影响它的技术因素。由于硅熔体附近的波和流动模式的改变而引起的表面扩大被确定为杂质去除率提高的潜在原因。找到并讨论了获得改进的杂质去除所需的最小波幅的无量纲准则。
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引用次数: 0
Modelling of Methanol Production From Biogas 利用沼气生产甲醇的模型制作
IF 0.6 Q4 PHYSICS, APPLIED Pub Date : 2023-12-01 DOI: 10.2478/lpts-2023-0043
V. Kharitonov, V. Geža, L. Rodin, M. Shorohov
Abstract This article presents a computer model for the methanol production from biogas. The stages of autothermal and steam reforming of biogas and the methanol synthesis cycle are considered. A study has been performed on the influence of the composition of biogas and the method of its conversion on the amount of methanol produced. As a result of the computational experiment on the model, the optimal composition of biogas has been determined and the applicability of the methods of autothermal and steam reforming has been assessed. An assessment has been made of reducing the carbon pressure on the environment during the processing of biogas into methanol.
摘要本文建立了沼气制甲醇的计算机模型。考虑了沼气的自热重整和蒸汽重整阶段以及甲醇合成循环阶段。研究了沼气组成及其转化方法对甲醇产出量的影响。通过对该模型的计算实验,确定了沼气的最佳组成,并对自热重整和蒸汽重整方法的适用性进行了评价。在将沼气加工成甲醇的过程中,对降低对环境的碳压力进行了评估。
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引用次数: 0
Porous Material for Gas Thermal Compression in Space Conditions: Thermal Design Aspects 用于空间条件下气体热压缩的多孔材料:热设计方面
IF 0.6 Q4 PHYSICS, APPLIED Pub Date : 2023-12-01 DOI: 10.2478/lpts-2023-0048
I. Ušakovs
Abstract It is almost impossible to name a field of human activity where porous materials are not used. Filters, membranes, thermal insulators, fuel cells, catalysts, wicks of heat transfer devices, sorbents, textiles, and other examples of porous materials explain such an increased interest in the study of their properties, design of new materials, and development of technologies for their manufacture. The recent need for in-orbit spacecraft refuelling has led to the development of gas thermal compression technology based on the use of porous material as both a fuel retention mechanism and thermal interface. The present paper reveals the thermal aspects of porous material design for a device intended for pumping xenon, fuel for ion thrusters, in zero-gravity conditions – Xenon Refuelling Compressor.
几乎不可能说出一个不使用多孔材料的人类活动领域。过滤器、膜、隔热体、燃料电池、催化剂、传热装置芯、吸附剂、纺织品和其他多孔材料的例子解释了人们对多孔材料性能研究、新材料设计和制造技术开发的兴趣日益增加。近年来对航天器在轨加油的需求导致了基于多孔材料作为燃料保留机制和热界面的气体热压缩技术的发展。本论文揭示了用于在零重力条件下泵送氙(离子推进器的燃料)的多孔材料设计的热方面-氙加油压缩机。
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引用次数: 0
CFD Analysis of Airborne Pathogen Disinfection in a UV-C Air Purification Device 紫外线-C 空气净化装置中空气传播病原体消毒的 CFD 分析
IF 0.6 Q4 PHYSICS, APPLIED Pub Date : 2023-12-01 DOI: 10.2478/lpts-2023-0042
A. Sabanskis, D. D. Vidulejs, J. Virbulis, A. Jakovics
Abstract Numerical simulations of the airflow inside a portable air purification device have been carried out. The simplified system geometry is comprised of key components – fans, particle filters and UV lamps for disinfection, which are included in the model. The study investigates the velocity distribution, UV irradiance, and its impact on air disinfection. The effects of the flow rate and UV dose on the purification efficacy have been investigated. The findings provide valuable insights for optimising the design and configuration of air purification devices, and their potential role in reducing the transmission of airborne diseases.
摘要对便携式空气净化装置内部气流进行了数值模拟。简化的系统几何结构由关键部件组成——风扇、粒子过滤器和用于消毒的紫外线灯,这些都包含在模型中。研究了空气消毒的速度分布、紫外线辐照度及其对空气消毒的影响。考察了流量和紫外线剂量对纯化效果的影响。这些发现为优化空气净化装置的设计和配置以及它们在减少空气传播疾病方面的潜在作用提供了有价值的见解。
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引用次数: 0
Numerical Insights Into Gas Mixing System Design for Energy Conversion Processes 能源转换过程中气体混合系统设计的数值见解
IF 0.6 Q4 PHYSICS, APPLIED Pub Date : 2023-12-01 DOI: 10.2478/lpts-2023-0044
M. Klevs, G. Zageris, A. A. Ziemelis, V. Dzelme, V. Geža, A. Jakovics
Abstract Uniform gas mixing is important in various scientific and engineering domains, particularly in a chemical reactor design employing pre-mixed gases for processes. Assessing the performance of different mixer designs through physical prototypes can be resource-intensive and time-consuming. Consequently, this study underscores the significance of numerical simulations to optimize gas mixing and distribution systems in energy conversion applications. The research primarily focuses on varying the base mixer geometry by modifying the configuration of cross-flow inlets alongside the chambers. By employing numerical simulations, critical factors influencing mixing uniformity are identified, and innovative solutions are proposed to enhance system performance. Additionally, this work extends its application to improving the operational conditions of an industrial biomass gasifier, underlining the practicality of numerical modelling in addressing complex engineering challenges.
均匀的气体混合在许多科学和工程领域都很重要,特别是在采用预混合气体进行工艺的化学反应器设计中。通过物理原型评估不同混合器设计的性能可能会耗费大量资源和时间。因此,本研究强调了数值模拟在能量转换应用中优化气体混合和分配系统的重要性。研究主要集中在通过改变沿腔室的交叉流入口的配置来改变基础混合器的几何形状。通过数值模拟,找出了影响混合均匀性的关键因素,并提出了提高系统性能的创新解决方案。此外,这项工作将其应用扩展到改善工业生物质气化炉的运行条件,强调了数值模拟在解决复杂工程挑战方面的实用性。
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引用次数: 0
Numerical Model and System for Prediction and Reduction of Indoor Infection Risk 预测和降低室内感染风险的数值模型和系统
IF 0.6 Q4 PHYSICS, APPLIED Pub Date : 2023-12-01 DOI: 10.2478/lpts-2023-0041
J. Virbulis, J. Telicko, A. Sabanskis, D. D. Vidulejs, A. Jakovics
Abstract The developed numerical model assesses the risk of a COVID-19 infection in a room based on the measurements of temperature, relative humidity, CO2 and particle concentration, as well as the number of people and occurrences of speech, coughing, and sneezing obtained through a low-cost sensor system. As the model operates faster than real-time, it can dynamically inform the persons in the room or building management system about the predicted risk level. When the infection risk is high, the model can activate an air purifier equipped with filtration and UV-C disinfection. This solution improves energy efficiency by reducing the ventilation intensity required during colder seasons to maintain the same safety level and activating the purifier only when the predicted infection risk surpasses a specified threshold.
该数值模型通过低成本传感器系统测量房间内的温度、相对湿度、二氧化碳和颗粒浓度,以及说话、咳嗽和打喷嚏的人数和发生情况,来评估房间内COVID-19感染的风险。由于该模型运行速度快于实时,因此可以动态地将预测的风险等级告知房间或建筑物管理系统中的人员。当感染风险高时,该模型可以启动配备过滤和UV-C消毒的空气净化器。该解决方案通过降低寒冷季节所需的通风强度来提高能源效率,以保持相同的安全水平,并仅在预测感染风险超过指定阈值时激活净化器。
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引用次数: 0
The Use of Renewable Energy and Capillary Heat Exchangers for Energy Savings in the Existing Apartment 利用可再生能源和毛细管换热器为现有公寓节约能源
IF 0.6 Q4 PHYSICS, APPLIED Pub Date : 2023-12-01 DOI: 10.2478/lpts-2023-0046
S. Gendelis, A. Jakovics, O. Pulkis, I. Bukans
Abstract The use of capillary heat exchangers with a large area means the lowest heat carrier temperature – typically less than 30 °C for heating. This determines the very efficient use of the installed heat pump due to an increase in the coefficient of performance (COP) with a decrease in the provided water temperature. The aim of the study was to find out whether renewable energy sources and radiant capillary heat exchangers increase energy efficiency. In order to achieve the maximum energy efficiency during the renovation of the existing apartment, a combination of two green approaches was used. One of them is the replacement of the existing high-temperature radiator heating system with radiant capillary mats. The same system is also used for cooling, which was not possible with the existing system. The necessary energy is provided from renewable aerothermal energy by installing a heat pump together with PV panels to ensure electricity consumption. The measurements were made in the apartment to determine the thermal transmission properties of all boundary structures and an air exchange rate using long-term monitoring. Experimental data were used to create the heat balance, to estimate the heating and cooling powers, as well as the seasonal energy needs. The amount of capillary heat exchangers and the size of the heat pump were chosen accordingly. The very first energy consumption data allow concluding that the planned improvement of the energy efficiency has been successfully achieved by using technology combination described without improvement of the thermal properties.
使用面积大的毛细热交换器意味着最低的热载体温度-通常小于30°C进行加热。由于性能系数(COP)随着提供的水温的降低而增加,这决定了安装的热泵的非常有效的使用。这项研究的目的是找出可再生能源和辐射毛细管热交换器是否能提高能源效率。为了在现有公寓的改造过程中实现最大的能源效率,我们使用了两种绿色方法的组合。其中之一是用辐射毛细垫代替现有的高温散热器供暖系统。同样的系统也用于冷却,这在现有的系统中是不可能的。所需的能量来自可再生的空气热能源,通过安装热泵和光伏板来确保电力消耗。测量是在公寓内进行的,以确定所有边界结构的传热特性,并通过长期监测确定空气交换率。实验数据用于创建热平衡,以估计加热和冷却功率,以及季节性能源需求。对毛细管换热器的数量和热泵的尺寸进行了相应的选择。第一个能耗数据可以得出结论,通过使用所描述的技术组合,在不改善热性能的情况下,成功地实现了计划中的能效改进。
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引用次数: 0
期刊
Latvian Journal of Physics and Technical Sciences
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