Hot Zone Research Articles

A field investigation on thermal comfort of kindergarten children in China’s Hot Summer and Cold Winter zone during winter

A field investigation on thermal comfort of kindergarten children in China’s Hot Summer and Cold Winter zone during winter

Research on predicting the thermocompression deformation behavior of Mg-Li matrix composite using machine learning and traditional techniques

Artificial intelligence and machine learning (ML) technologies have emerged as powerful tools for analyzing the thermal compression deformation behavior of metal matrix composites, offering significant potential to optimize their plastic deformation processing techniques. In this study, the Al3La/LAZ532 composite based on in-situ self-reaction technology was successfully prepared by adding La2O3 particles. Then, the thermal compression flow behavior of the as-cast composite was comparatively researched using a traditional Arrhenius model and advanced machine learning methods (Linear Regression, AdaBoost, Random Forest, and XGBoost). The flow stresses were predicted under various thermal operating conditions, and the performance of all models was assessed using root mean square error (RMSE), coefficient of determination (R2) and mean absolute error (MAE). Analysis shows that the Random Forest model outperforms traditional models and other ML methods in predictive accuracy, achieving an R2 of 0.97, an MAE of 5.8, and an RMSE of 7.07. Additionally, the stable hot working zone for the composite at 300 °C and a strain rate of 0.001∼0.01 s⁻1 can be identified by combining the microscopic structure with the macroscopic hot working map. This zone is characterized by a uniformly distributed, fine-grained structure with high levels of dynamic recrystallization (DRX). The texture with the <0001> axis of the grains aligned parallel to the compression direction (CD) is formed in the thermally deformed microstructure, and the DRX mechanism is discontinuous dynamic recrystallization (DDRX).

Evaluating the Effect of Adaptive Reuse in the Energy Performance of Historic Buildings: A Case Study from Türkiye

The building sector accounts for 30% to 40% of total energy consumption, and historic buildings play an important role in this proportion. Historical buildings that do not meet the required comfort conditions for the residents are adaptively reused, with various revisions. Recognizing the energy design of a historical building in its original condition and comparing the current situation can help create future solutions. This study examines the changes that a historic house in a hot climate zone in Türkiye experiences, from its original state up until the current situation. Energy analyses of the pre- and post-restoration situation are carried out, and the effect of adaptive reuse decisions on the energy performance of the building is investigated. A dynamic thermal simulation created with DesignBuilder was used to identify the energy use, carbon emissions, and thermal comfort. TM59 adaptive thermal comfort was used for the pre-restoration and the Fanger model for the post-restoration phase. This building, which was repurposed from a three-block residence, consists of a four-block hotel. Although the preservation of its original value is at the forefront, various structural changes were observed. The analysis demonstrates a higher occurrence of discomfort hours during summer compared to winter, consistent across both phases. Furthermore, energy consumption increased significantly, predominantly for heating, representing a doubling of energy use during the post-restoration phase. This is attributed to the building’s conversion into a hotel and the use of mechanical systems. Future research is required to develop strategies to reduce the energy consumption, carbon emissions, and discomfort hours while maintaining the value of the historic building and its materials.

Temperature distribution considering the film-wise condensation and its impact on multi-stage oil production during the co-injection of steam-CO2

The co-injection of steam and CO2 into oil sands reservoirs has proved to be one of the most efficient and environmentally friendly methods to produce bitumen. Nevertheless, the condensation mechanism of steam in the reservoir is film-wise condensation under the effect of CO2, which reduces the heat transfer efficiency of steam. To obtain accurate oil production during the co-injection of steam-CO2, it is critical to predict the temperature distribution considering the film-wise condensation and clear its impact on oil production. In this study, laboratory experiments with different injectors were conducted to clear the effect of film-wise condensation on temperature distribution in the formation. Then, a mathematical model considering film-wise condensation was established to predict the temperature distribution and oil production, compared with the measured experiment result and multi-stage oil production from field data. Finally, the effect of temperature distribution on multi-stage oil production was analyzed through different injection volumes. The results indicated that the impact of film-wise condensation inhibits the development of the steam zone(Ts) but explicitly expands the hot water zone(Ts ∼ Tr). Moreover, the different injection components affect film-wise condensation, and CO2 has a more pronounced effect, whereas steam has little impact on the hot water zone despite its significant effect on steam zone expansion by weakening the film-wise condensation. Furthermore, the oil production exhibits the multi-stage characteristic controlled by different heating zones(the steam zone and the hot water zone), such that the steam zone contributes to higher oil production in the rising stage, and a larger hot water zone induces a longer life of the rising stage and the stable stage.

Crystal surface heat transfer during the growth of 300mm monocrystalline silicon by the Czochralski process

This paper investigated the lower heat transfer efficiency of ingot after increasing the size of Czochralski monocrystalline silicon. To improve the heat transfer efficiency, industrial Czochralski monocrystalline furnaces use water-cooling jackets to enhance crystal heat transfer. Through two-dimensional modeling, radiative heat transfer between monocrystalline silicon and the water-cooling jacket was investigated. The results showed that the effective radiation on the crystal surface decreased, then increased, and then decreased again. Numerical simulations showed that the maximum effective radiation on the surface was greater than 60 000 W/m2, which represents a significant increase in the heat flow density compared with the radiation of the crystal without using water cooling. According to the angle factor definition, a model of the radiative heat transfer angle factor between the water-cooling jacket and silicon rod was established. The dynamic correlation equation between the radiation angle factor and geometrical parameter of the hot zone, solidification rate, and solidification time was derived. Finally, a water-cooling jacket suitable for growing large monocrystalline silicon rod was designed according to the model, which improved the growth efficiency of the crystals. The results of the study are of great significance for optimizing water-cooling jackets.

Investigating the formation of soot in CH4 pyrolysis reactor: A numerical, experimental, and characterization study

Methane pyrolysis is a promising method for eco-friendly hydrogen production, but soot formation and carbon interaction pose challenges for scaling up. Therefore, understanding the dynamics of soot formation and carbon deposition is crucial. This study delves into the intricacies of soot formation in methane pyrolysis under industrially relevant conditions, namely operations at atmospheric pressure, employing a H2:CH4 ratio of 2 and exploring a range of hot zone temperatures (1473 K, 1573 K, 1673 K, and 1773 K) with a 5 s residence time. Utilizing a detailed gas-phase kinetic model with direct carbon deposition reactions, the research adopts the method of moments coupled with a one-dimensional plug flow reactor model to simulate soot formation. The model is validated by characterizing soot particles that were produced in a pyrolysis reactor by means of transmission electron microscopy, Dynamic light scattering (DLS), and Raman spectroscopy. Results show that lower temperatures lead to nucleation-dominated growth, whereas higher temperatures significantly restrain particle growth due to carbon deposition. DLS data indicate a complex balance between particle growth and deposition processes. These findings provide insights into operational parameters that can enhance reactor performance and sustainability in hydrogen production processes by mitigating soot and carbon deposition.

Flux growth of Cs1-xRbxBF3 (B = Ca, Sr) crystals by the micro-pulling-down method

The possibility of growing Cs1-xRbxBF3 (B = Ca, Sr) crystals by micro-pulling-down was investigated due to their potential for application in ultrafast scintillation detectors. A LiF flux was applied to lower the melting point and therefore suppress evaporation of CsF from the melt. Suitable growth conditions were obtained through careful choice of the hot zone elements. A crucible with minimal nozzle length improved mass transport and an afterheater with four windows provided a steep temperature gradient. Inclusion and crack-free crystals of Cs1-xRbxCaF3 (x = 0, 0.1, 0.25, 0.5, 0.75, 0.9, and 1) and CsCa1-xSrxF3 (x = 0, 0.1, and 0.25) were grown under optimized conditions. Despite the hygroscopic nature of the heavy alkali metal fluorides, all the grown crystals are non-hygroscopic which significantly improves their application potential. Growth of CsCa1-xSrxF3 crystals with higher Sr concentration was complicated by the low solubility of SrF2 in the LiF-CsF melt and the hygroscopic nature of the CsSrF3. The formation of solid solution in the Cs1-xRbxCaF3 and CsCa1-xSrxF3 systems was investigated through the dependence of lattice parameters on nominal composition.

Preparation of 97% pure nickel-cobalt alloy from waste Ni-MH batteries by using waste glass as a fluxing agent

With the e-waste growing rapidly all over the globe due to growing demand of electronics, smartphones, etc., coming up with an efficient and sustainable recycling process is the need of the hour. The present work reports a novel and sustainable process of manufacturing Ni alloy by bringing together three major waste streams such as waste Ni-MH batteries, e-waste plastics, and waste glass. The chosen temperature (1550 °C) favours the reduction of nickel-oxide by e-waste plastic as the reductant and sends rare earth elements present in the waste Ni-MH battery as oxide mixture to the slag phase. Waste glass powder used in this process functions as the fluxing agent, hence not requiring any additional flux. The reduction mechanism is gas-based, controlled mainly by hydrogen and carbon monoxide gases released as a result of decomposition of e-waste plastic as reaction commenced from cold zone (∼300 °C) to hot zone (1550 °C) in the horizontal tubular furnace. Formation of nickel alloy and enrichment of slag with mixture of rare earth oxides were confirmed by XRD, SEM-EDS, and Rietveld refining analysis performed on the XRD spectra of slag phase. ICP-OES (Inductively coupled plasma optical emission spectroscopy) and LIBS (laser induced breakdown spectrometer KT-100S) confirmed the high metal content in the alloy, thereby emphasizing the purity (∼98%) which is close to the composition of nickel super alloy. A maximum of 61% by weight REO enrichment was achieved in the slag phase, having La2O3:44.6%, Pr2O3:14.8%, and Nd2O3: 1.6% under optimised experimental conditions (1550 °C, 15 min, and 20% waste glass powder). This scientific investigation evinces a promising route for efficient utilisation of waste streams emanating from e-waste, thereby devising a sustainable recycling technique and protecting the environment, too.

Research on the energy saving behaviors of university students based on TPB in a hot summer–cold winter area in China

Energy saving in higher education institutions holds significant importance in the establishment of environmentally friendly and low-carbon societies, with the energy-saving behaviors of university students playing a pivotal role in the development of sustainable campuses. However, there is a clear need for customized strategies to encourage energy-saving habits among university students in areas of China with extreme weather conditions, such as hot summers and cold winters. This study offers a thorough examination of the literature regarding energy-saving behaviors among college students and presents a new theoretical framework based on the Theory of Planned Behavior (TPB). A survey questionnaire is conducted at universities in regions with hot summers and cold winters across China, with the goal of identifying the main factors that influence students' intentions and actions regarding campus energy conservation. From July to August 2022, we collected 512 survey responses from different university campuses in China's hot summer-cold winter weather zone. The survey asked about subjective norms, understanding of energy conservation, and the importance of saving energy. Utilizing the Structural Equation Model (SEM), we examined how influencing factors are associated with energy conservation behaviors. Our findings indicate that (1) both the significance of energy conservation and subjective norms significantly drive energy-saving actions; (2) distinct factors impact different forms of energy-saving practices; and (3) the inclination to save energy partially mediates the relationship between comfort choices and the significance of energy conservation. This study presents a validated behavioral model tailored for regions experiencing hot summers and cold winters, offering valuable insights for college administrators in managing energy usage while also serving as a theoretical reference for establishing environmentally sustainable campuses.

Investigating the 17 March 2013 Geomagnetic Storm Impacts on the Wholly Coupled Solar Wind‐Magnetosphere‐Ionosphere‐Thermosphere System‐Of‐Systems

AbstractIn this study, we investigate the impacts of the 17 March 2013 strong geomagnetic storm on the wholly coupled Solar Wind‐Magnetosphere‐Ionosphere‐Thermosphere system‐of‐systems. Obtained from multipoint observations, our new results show (1) the solar‐wind Alfven waves propagating antisunward in the sheath region and (2) oscillating solar wind interplanetary magnetic field (IMF) and electric (E) field (IEF EY) that powered (3) rigorous dayside and nightside flux transfer events (FTEs) when (4) the nightside‐reconnection‐related short circuiting led to fast‐time Subauroral Ion Drifts (SAID) and Subauroral Polarization Streams (SAPS) E field development across the inner‐magnetosphere plasmapause where the solar‐wind Alfven waves (4) transitioned into kinetic Alfven waves (5) fueling the hot zone. Also, the antisunward solar‐wind Alfven waves (6) drove enhanced large‐scale region‐1 field‐aligned currents creating (7) undershielding conditions (8) allowing the dawn‐to‐dusk convection E field's earthward penetration, and (9) generated increased solar‐wind kinetic energy, which became deposited (10) to the ionosphere increasing the ionospheric electron temperature (by the downward flowing suprathermal electron fluxes) and (11) to the thermosphere oscillating the neutral winds and increasing the neutral temperature, and finally leading to (12) the development of bright stable auroral red (SAR) arcs in (13) the enhanced SAID/SAPS flow channels (FCs) developed during FTEs, (14) demonstrated with FC‐2 and FC‐3 events, in the enhanced polar convection that (15) the Rice Convection Model could reproduce. Finally, we conclude the antisunward‐propagating large‐amplitude solar‐wind Alfven waves' ultimate significant role in creating the favorable conditions for the various phenomena documented with the new observational results (1–14).

Classification of SARS-CoV-2 sequences as recombinants via a pre-trained CNN and identification of a mathematical signature relative to recombinant feature at Spike, via interpretability.

The global impact of the SARS-CoV-2 pandemic has underscored the need for a deeper understanding of viral evolution to anticipate new viruses or variants. Genetic recombination is a fundamental mechanism in viral evolution, yet it remains poorly understood. In this study, we conducted a comprehensive research on the genetic regions associated with genetic recombination features in SARS-CoV-2. With this aim, we implemented a two-phase transfer learning approach using genomic spectrograms of complete SARS-CoV-2 sequences. In the first phase, we utilized a pre-trained VGG-16 model with genomic spectrograms of HIV-1, and in the second phase, we applied HIV-1 VGG-16 model to SARS-CoV-2 spectrograms. The identification of key recombination hot zones was achieved using the Grad-CAM interpretability tool, and the results were analyzed by mathematical and image processing techniques. Our findings unequivocally identify the SARS-CoV-2 Spike protein (S protein) as the pivotal region in the genetic recombination feature. For non-recombinant sequences, the relevant frequencies clustered around 1/6 and 1/12. In recombinant sequences, the sharp prominence of the main hot zone in the Spike protein prominently indicated a frequency of 1/6. These findings suggest that in the arithmetic series, every 6 nucleotides (two triplets) in S may encode crucial information, potentially concealing essential details about viral characteristics, in this case, recombinant feature of a SARS-CoV-2 genetic sequence. This insight further underscores the potential presence of multifaceted information within the genome, including mathematical signatures that define an organism's unique attributes.

Thermal Performance and Building Energy Simulation of Precast Insulation Walls in Two Climate Zones

Traditional concrete buildings exhibit low energy consumption and high heat loss, which results in a larger environmental problem. Precast insulation walls are proposed for strengthening thermal insulation efficiency and mitigating heat loss. Numerous studies have investigated the thermal performance of insulation walls over the past decades. However, gaps remain in practical engineering applications. This study aims to bridge these gaps by providing practical design recommendations based on experimental research. Nine different types of precast insulation walls were tested to examine the thermal performance, and the parameters of the insulation material, insulation form, insulation layer thickness, and concrete rib width were investigated. Then, numerical models of these walls were developed for simulating the thermal performance of the tested specimens. Finally, a six-story student apartment model using designed walls was developed to assess energy consumption in two distinct climate zones: the hot summer and cold winter zone of Changsha City, and the cold zone of Harbin City. The results indicate that the precast insulation wall with external insulation form shows better thermal performance than the sandwich insulation form. It is recommended to use precast insulation walls with 50 mm extruded polystyrene (XPS) external thermal insulation form in Changsha City and 80 mm XPS external thermal insulation form in Harbin City. Furthermore, buildings using precast insulation walls can significantly reduce energy consumption by 49.25% in Changsha and 49.38% in Harbin compared to traditional concrete wall buildings. Based on these findings, suitable design suggestions for this precast concrete wall panel building composed of insulation walls are given.

Experimental study of the effect of crude oil water content on boilover fire

When a tank experiences a boilover fire, oil droplets splash, heat release rate and flame height increase, posing significant hazards. Water is a necessary condition for boilover to occur, but current research mainly focuses on boilover caused by water layer, neglecting the influence of water content inherent in crude oil on boilover phenomena. In this study, crude oil with a water content ranging from 0.26 % to 3 % was utilized, and a series of boilover fire experiments were conducted by varying the presence or absence of a water layer and the initial oil thickness and by carrying out a series of boilover fire experiments focusing on the effect of water content on the boilover phenomenon. The results indicate that emulsified crude oil has a droplet micro-explosion phase during the stable combustion stage. When no water layer is present, the boilover process duration is brief, and the transient injection effect is notable, with boilover intensity increasing with water content. Upon adding a water layer, emulsified water abbreviates the boilover onset time, diminishes the combustion rate, and promotes the formation of the hot zone. The upper and lower limit values of the hot zone temperature decrease with increasing water content, while the temperature difference remains essentially unaffected, remaining constant at about 50 °C. Boilover intensity exhibits a nonlinear relationship with increasing water content, peaking at 2 % water content. The pre-boilover burned mass ratio remains relatively stable, maintained between 12 % and 15 % across all working conditions. Both the splash range and maximum heat flux increase with initial oil layer thickness but show no significant change with water content. Moreover, the safety distance corresponding to the heat radiation threshold exceeds the splash distance, indicating that heat radiation hazards predominate. The results of this paper will help provide guidance for fighting emulsified crude oil fires.

Quantification of interactions among agricultural drought indices within Köppen–Geiger climate zones in Bangladesh

Agricultural productivity is highly correlated with climatic variations, including drought events. This study is aimed at performing a comprehensive assessment of agricultural drought conditions in the Köppen–Geiger climate zones in Bangladesh, based on the temperature condition index (TCI), vegetation condition index (VCI), and vegetation health index (VHI). The zones are classified as follows: temperate dry winter with a hot summer zone, tropical savannah zone, and tropical monsoon zone. The range of VHI is optimized based on its correlation with TCI and VCI. The correlation among the stratified drought indices is also examined to quantify and measure the strength and direction of the linear relationships between them. Moreover, Mann–Kendall test is conducted to assess the statistical trends in the spatiotemporal propagation of droughts across different climate zones. The balanced correlation approach for VHI reveals that vegetation health is governed by the temperature conditions. Certain variations in the drought intensity, frequency, and duration are observed across climatic zones in earlier years while the recent years are noted with less droughts. Normal or no drought conditions are noticed mostly in the tropical monsoon zone through VCI and VHI. The correlations among the drought classes indicate that VHI is more strongly correlated with TCI than with VCI, while NDVI exhibits stronger correlations with VCI than with either VHI or TCI. The Mann-Kendall test revealed that VCI has significant downward trends in drought categories and an upward trend in normal conditions, whereas VHI and TCI displayed inconsistency in statistical trends. By extensively exploring the agricultural drought conditions within specific climate zones, this study offers valuable insights for agronomists and stakeholders involved in climate resilience planning and agricultural development in Bangladesh.

Effects of solar energy absorbed by south wall on carbon emission from space heating in hot summer-cold winter region

Carbon emission caused by space heating (CEH) in hot summer and cold winter climate zone has increased dramatically. Taking advantage of the solar energy absorbed by south wall (SEASW) can effectively reduce CEH, however, the accurate quantification of its impact remains a challenge. The study investigates the potential of SEASW in mitigating CEH. Key parameters affecting CEH, such as sunny day ratio, insulation form, and outer surface heat transfer coefficient of south wall (h), were analyzed. Results show the reduction in carbon emissions caused by the solar energy absorbed by each unit area of the south-facing wall (ΔCreduction) can be as high as 18.61 kgCO2⋅m−2 for the wall employing internal insulation and smaller h. A prediction model of ΔCreduction was further developed by using multivariate nonlinear regression, which can estimate the reduction in CEH for different fuels as heating source by a south wall in different sizes. Besides, the potential of SEASW on the reduction of carbon emission per unit floor area can reach 12.2 %. This study underscores the importance of SEASW as a carbon-neutral heating strategy, particularly for regions characterized by short winter heating periods and lower heating loads compared to colder climates. It provides valuable insights for sustainable energy practices and policy formulation.

Determination of Thermal Properties of Carbon Materials above 2000 °C for Application in High Temperature Crystal Growth

AbstractThis work reports on the determination of the heat conductivity of high temperature stable carbon materials in the temperature range well above 2000 °C where classic material characterization methods fail. Dense graphite (DG) materials as well as rigid and soft felt isolation (RFI/SFI) components have been investigated which are used during crystal growth of SiC by the physical vapor transport method (PVT) in the temperature regime of 2000 and 2400 °C. The applied materials characterization methods include low temperature physical heat conductivity measurements using laser flash analysis (LFA) in the temperature range 25–1200 °C, data extrapolation to elevated temperatures up to 2400 °C, and a correlation of heating processes and computer simulation of the temperature field of different hot zone designs. Using this approach, the calculated temperatures and experimentally determined values with an error of less than ± 2% at 2400 °C can be merged.

Defining faces, defying borders: authority conflicts between medical specialties through cosmetic interventions

At first glance, medical specializations seem to be delineated according to well-defined scientific criteria; the apparently-functional division of labor generates a general hierarchy of specialized knowledge and practice. However, this unequal apportionment of professional power and authority also depends on capitalistic organization. While the medical rationale has always been market-related, starting in the 1980s—with the initiation of its neoliberal agenda—Turkey has enacted progressively aggressive policies, privatizing healthcare service and reconceptualizing it as a dynamic market, thereby forming a medical ethos entangled with neoliberal motifs. In this article, we analyzed how unregulated market conditions give rise to a chaotic scientific field, and how this apparent disorder serves to reproduce an underlying capitalistic logic. Of the multitude of human body parts, we choose the face, because it has become a hot zone in medicine as cosmetic demands from patients have skyrocketed, and because it is an area generating conflict between medical specialties seeking more authority and power. To this end, we interviewed thirty-three specialists from dermatology, otorhinolaryngology, and plastic surgery about their experiences on authority conflicts and their motivations for entering into an unregulated market. Our research highlights how actors in the medical field constitute a relational social context within which boundaries are fiercely negotiated through a market logic. Thereafter, we argue how the ambiguities of pathology, aesthetics, body, and norms that underlie cosmetic procedures are fluidized and become instruments of power, such that this ambiguity has become the very defining characteristic of the scientific field.

Thermal performance assessment of exterior building walls under intermittent air-conditioning operation in China's hot summer and cold winter zone

Optimizing the design and accurately assessing the performance of building envelopes are critical for substantially reducing energy use in the building sector. Existing studies on methods for evaluating the thermal performance of building envelopes have primarily focused on periodic unsteady conditions (often associated with continuous air-conditioning operation). This study aims to investigate the initial transient thermal performance of exterior building envelopes. Specifically, we examined varying insulation distributions considering the hot summer and cold winter zone of China as an example. To simulate real-world conditions, we developed a dynamic hot box facility that mimics both outdoor and indoor environments, enabling the measurement of key parameters of the dynamic thermal process of the wall. We evaluated the thermal response, energy performance, and heat storage metrics of the wall to understand the impact of the insulation distribution and air-conditioning operation modes on the thermal performance of opaque building walls. This assessment covered six intermittent operation stages—four construction structures and two types of building usage—for both summer and winter conditions. The proposed methodology provides a quantitative approach for assessing the dynamic thermal processes of the wall, with the results indicating that the heat transmission of walls during intermittent operation exhibited initial transient characteristics. As a result, thermal performance indices suitable for periodic unsteady conditions could not be directly applied to initial transient conditions. To address this issue, the metrics of daily mean dynamic thermal transmittance and daily mean dynamic thermal resistance were proposed and validated. These metrics accurately reflected the actual fluctuations in total transmission loads, thus providing an accurate rapid index-oriented method for assessing the energy-saving performance of walls. Overall, this study lays the groundwork for evaluating dynamic thermal behaviour of building envelopes.

Enhancing energy efficiency of PCM wall in winter with novel PCM-DLCB coupling design

In order to enhance the thermal performance of the phase change material (PCM) wall during winter, a novel PCM and double-layer capillary bundles (PCM-DLCB) coupling wall is proposed. The PCM-DLCB wall utilizes the capillary bundle near the outer surface to capture solar energy during sunny winter days. The heat is then transferred to the capillary bundle near the inner surface through a circulating pump, promoting the melting of the PCM. Optimization and long-term operation comparison research were conducted using numerical simulation to investigate the potential of the PCM-DLCB wall to improve energy efficiency during winter. Five structural parameters, including the type of PCM, the position of the capillary bundle, the position and thickness of the PCM layer, the spacing of the capillary bundles, and the flow velocity in the capillary bundle, were selected as variables for structural and operation optimization. The optimization target was the accumulated heat gain from the inner surface of the wall. The research results indicate that: (1) The most suitable PCM is RT-18HC; (2) Placing the PCM layer between the double-layer capillary bundle yields better results compared to other arrangements; (3) Optimal energy saving is achieved when the outer capillary bundle is positioned 6 mm away from the outer surface and the inner capillary bundle is positioned 8 mm away from the inner surface; (4) The optimal thickness of the PCM layer is 10 mm; (5) The optimal flow velocity in the capillary bundle is approximately 0.04 m/s. Furthermore, long-term operation results based on a typical hot summer and cold winter climate zone reveal that the optimized PCM-DLCB wall provides a 7.80 % increase in indoor heat gain compared to an ordinary PCM wall during winter, and an 18.4 % increase compared to a wall without PCM.

Enhancing thermal comfort in buildings through the integration of phase change material on the building envelope: a simulation study

Abstract According to the report published by the International Energy Agency (IEA), active space cooling and air conditioning systems consume approximately 16% of the building sector’s final electricity consumption and contribute 3.94% of global greenhouse gas emissions. In this regard, the use of low-cost but effective passive solutions, such as organic phase change materials (PCM) on the building envelope, can provide high thermal mass and thus can lower the temperature fluctuation inside the building. In the current study, the potential of PCM-enhanced building envelopes to enhance thermal comfort has been studied. The study has been performed using the conduction finite difference (ConFD) algorithm in EnergyPlus software. A comparative study has been done for a traditional reinforced cement concrete (RCC) reference test room of size (5m x 6m x 3m) and another room of the same size with PCM-enhanced walls for the hot and humid climate zone of Guwahati (latitude 26.1, longitude 91.7), in India. A PCM thickness of 20 mm is used at the external surface of the wall between the red clay burnt brick (120 mm in thickness) and the cement plaster (25mm thick). The PCM used for the study is a biocomposite PCM, named WH-PCM, with a melting point of 31.5°C and thermal conductivity of 0.27 W/mK. The simulation results reveal that the R-value of the external wall of the room with PCM walls has been increased by 84.90% compared to the reference room with the incorporation of WH-PCM, resulting in a mean zone temperature difference of 0.3°C throughout the year. Also, the indoor thermal discomfort hours have been annually reduced by 15.82% with the use of WH-PCM when compared with the reference room. A similar temperature difference trend, which is 1.93°C, is also observed in the single PCM brick experimental result under identical testing conditions as a regular brick of the same size.