Humid Climate Area Research Articles

The pore water pressure changes on forested slopes in tropical humid climate area

The pore water pressure changes on forested slopes in tropical humid climate area

Evaluation of passive cooling through natural ventilation strategies in historic residential buildings using CFD simulations

Natural ventilation in hot climates has the potential to save energy by reducing the need to use mechanical systems. Particularly in historic buildings, it should be considered as a passive retrofit strategy before the addition of any mechanical systems to accommodate their unique indoor environmental characteristics and ensure their preservation. This study investigates the efficiency of multiple natural ventilation strategies in cooling a historic residential structure located in San Antonio, Texas, USA, a hot and humid climate area. It also analyzes their potential to provide a thermally comfortable indoor environment during the spring and summer. Onsite data and ASHRAE standards were used to create and validate Computational Fluid Dynamics (CFD) and energy models. Six different natural ventilation approaches were simulated, and the results were analyzed and compared. The analysis revealed that all the considered scenarios can contribute to energy savings in both seasons, especially in spring, with cross ventilation being the most efficient strategy. It also proved that the size of the openings has an impact on thermal comfort. This study demonstrated that historic preservation and thermal comfort goals can be achieved simultaneously, and the results can be replicated in multiple historic structures in similar climate regions around the globe.

Geographical and morphological changes of conifers in Yunnan, China during the Cenozoic in response to climatic changes

Yunnan province, known as a hot spot of plant diversity, is located in Southwest China and on the southeastern margin of the Qinghai-Tibet Plateau. Today, there are four families, 21 genera and 56 species of conifers found in Yunnan. Three families, 15 genera and 44 species of fossil conifers have been reported from the Cenozoic in Yunnan. In this study, we investigated the fossil conifers from the Cenozoic in Yunnan and their corresponding living species and evaluated the distribution and climatic conditions of the extant genera. Based on this analysis, paleoclimates of the fossils were reconstructed to determine the migration patterns of these conifers in response to climatic changes caused by the uplift of the Qinghai-Tibet Plateau. Our analyses show that the cooling trend led to a southward expansion and migration of conifers to warm and humid climate areas since the early Oligocene. In addition, the drought tendency led to the disappearance of certain conifer species from Yunnan, and the strengthening monsoon climate resulted in the migration of conifers eastward to eastern China or coastal areas, westward to western Yunnan, southeast Tibet and northern Myanmar and northward to dry and cold North China and North Korea. Likely adaptive morphological changes also occurred among the conifer species. The study also revealed that the diversity and composition of conifers in Yunnan have changed significantly since the early Oligocene with the uplift of the Qinghai-Tibet Plateau and climatic changes and that the extant lineages of Yunnan conifers appeared in the late Miocene.

An Anti-Condensation Radiant Heating Floor System in Buildings under Moistening Weather

In most regions of southern China, condensation frequently occurs on building surfaces during the period from March to April. This phenomenon has been affecting people’s safety and structural properties. This article proposes an innovative anti-condensation floor system based on the reverse Carnot cycle. The evaporation side treats the air and reduces the moisture content, and the heat extracted from the condensation side is recovered by a heat exchanger and transferred to the floor through capillary mats. Simulation studies of the dynamic operation performance have been conducted through the TRNSYS 18 software. The results show that an innovative anti-condensation floor system can effectively keep the floor dry in Guilin. At the same time, regarding the indoor comfort level index, the PMV value is within ±0.5, and the energy consumption of the system is 42% less than that of the cooling dehumidification system. The system also performs well in representative cities where the air moisture content is less than 12 g/kg. This article also provides a reference for the feasibility of radiant floor systems in humid climate areas.

Holistic analysis for the efficiency of the thermal mass performance of precast concrete panels in hot climate zones

PurposeThis paper investigates thermal mass performance (TMP) in hot climates. The impact of using precast concrete (PC) as a core envelope with different insulation materials has been studied. The aim is to find the effect of building mass with different weights on indoor energy consumption, specifically cooling load in hot climates.Design/methodology/approachThis research adopted a case study and simulation methods to find out the efficiency of different mass performances in hot and humid climate conditions. Different scenarios of light, moderate and heavyweight mass using PC have been developed and simulated. The impact of these scenarios on indoor cooling load has been investigated using the integrated environment solution-virtual environment (IES-VE) software.FindingsThe results showed that adopting a moderate weight mass of two PC sheets and a cavity layer in between can reduce indoor air temperature by 1.17 °C; however, this type of mass may increase the cooling demand. On the other hand, it has been proven that adopting a heavyweight mass for building envelopes and increasing the insulation material has a significant impact on reducing the cooling load. Using a PC Sandwich panel and increasing the insulation material layers for external walls and thickness by 50 mm will reduce the cooling load by 15.8%. Therefore, the heavyweight mass is more efficient compared to lightweight and moderate mass in hot, humid climate areas such as the UAE, in spite of the positive indoor TMP that can be provided by the lightweight mass in reducing the indoor air temperature in the summer season.Originality/valueThis research contributes to the thermal mass concept as one of these strategies that have recently been adopted to optimize the thermal performance of buildings and developments. Efficient TMP can have a massive impact on reducing energy consumption. However, less work has investigated TMP in hot and humid climate conditions. Furthermore, the impact of the PC on indoor thermal performance within hot climate areas has not been studied yet. The findings of this study on TMP in the summer season can be generated in all hot climate zones, and investigating the TMP in other seasons can be extended in future studies.

Simulation of roof retrofitting strategies to mitigate attic overheating issues of the terrace house under hot and humid climate

The purpose of this study is to investigate the potential mitigation strategies to overcome the overheating issue at the attic of the landed residential house located in a hot and humid climate area. An existing terrace house with 178 m2 was selected for this research. A building simulation model was created and calibrated by using the previous site measurement data collected by Ng et.al. in the year 2018. The calibrated model was subsequently used to evaluate various retrofitting methods and strategies, including roof insulation, and passive radiative cooling methods. The study shows that high albedo cool roof paint is the most effective roof retrofitting strategy compared to other approaches.

Development of an integrated index to quantify thermal comfort and walkability in urban areas

Although outdoor thermal comfort is extensively investigated in urban areas, the measures are barely focused to determine the walkability through these spaces. Therefore, a space with a high level of thermal comfort can experience a low level of pedestrian agglomeration while a space with a low level of thermal comfort can be massively used by inhabitants. Therefore, the solution to urban design and planning can be significantly altered if both dimensions are simultaneously taken into the account. This study investigates the relationship between spatial configuration and thermal comfort potential to evaluate the effect of spatial configuration on outdoor environmental quality. For this purpose, a framework is developed to understand the impact of built urban areas on thermal comfort and space syntax performance using a high-resolution spatial model to simulate the correlation of thermal comfort and betweenness centrality of a case study neighbourhood in the hot and humid climate area of Al-Khobar in Saudi Arabia. The mixed-use neighbourhood is analysed by the universal thermal comfort index and several space syntax metrics. The presented study uses Grasshopper environment and Ladybug and Decoding Spaces tools. The simulation study expressed that significant changes in orientation and buildings heights have a remarkable effect on improving OTC and space syntax in the urban neighbourhood.

Effect of the envelope structure on the indoor thermal environment of low-energy residential building in humid subtropical climate: In case of brick–timber vernacular dwelling in China

The brick–timber structure plays a crucial role in creating a comfort indoor thermal environment for low-energy vernacular dwellings. Herein, the thermal environment of the dwelling was studied by DesignBuilder software and evaluated using Adaptive Predicted Mean Vote (APMV) index. These results revealed that the indoor damp and cold feelings intensified in winter, and the mountain as a natural wind barrier weakened the attack of the prevailing wind in winter. These results leaded that the wind speed of the tested room was lower than 0.1 m/s. The thermal comfort satisfactory days in a year accounts for 56.2%, and the overall level of indoor thermal environment was low in the rest of the year, especially in winter. The simple structure of the exterior envelope and the single material were the main reasons for the poor indoor thermal environment of naturally ventilated buildings. Therefore, optimization strategies such as increasing the insulation materials of the envelope and adopting insulating glass windows were proposed. Compared to that before the retrofitting, the overall thermal environment grade of the vernacular dwelling has been improved by 4.7% (grade I), -0.3% (grade II) and -4.3% (grade III), respectively. The poor thermal performance and airtightness of the envelope easily lead to the negative effect of outdoor cold, heat and water vapor entering the house, which affects the thermal environment grade. These conclusions provided a reference for the optimization of the thermal environment of existing low-energy vernacular dwellings in subtropical humid climate areas. • Poor indoor thermal environment in winter in low-energy buildings. • Building airtightness is as important as the thermal performance of the envelope. • Buildings in humid subtropical climates should be well protected from moisture. • The height of surrounding buildings influences wind speed and shading

Impact of various multishaft combined ventilation modes on the removal of harmful gases released from mussel decay in a long-distance water conveyance tunnel

The harmful gases released from the decay of biologically invasive mussels are a major threat to the maintenance safety of long-distance water transfer projects in hot and humid climate areas. Setting up multiple working shafts along the long-distance underground water conveyance tunnel for maintenance ventilation can eliminate harmful gases and improve ventilation efficiency. The rational multishaft combined ventilation mode is an important guarantee for effective decontamination and maintenance safety in long-distance water conveyance tunnels. However, research on the release rule of harmful gases produced by rotten mussels and the multishaft combined ventilation modes of long-distance water conveyance tunnels has rarely been performed. In this study, a ventilation mathematical model considering the influence of harmful gases released by rotten mussels was implemented. The release rule of harmful gases was obtained by a mussel decay experiment, and the mathematical model was validated based on the data of a ventilation model test. Furthermore, the ventilation performance of multishaft combined ventilation modes was compared using a series of numerical simulations. The obtained results show that NH3 is the main component in harmful gases released by rotten mussels. The cumulative concentration of NH3 increases with the decay time of the mussel, reaching a peak value of 309.26 mg/m3. The maximum release rate of NH3 is 185.51 mg/(m3·d). In addition, the ventilation mode of alternately delivered and discharged airflow between adjacent working shafts is confirmed to be the best for long-distance tunnels with multiple working shafts according to the comparison of the airflow distribution and the removal effect of harmful gases under different modes of multishaft combined ventilation. This study provides useful guidance for the design and optimization of maintenance ventilation schemes in long-distance water transfer projects.

The Influence of Greenery and Landscape Design on Solar Radiation and UHI Mitigation: A Case Study of a Boulevard in a Hot Climate

Greenery is one of the most influential factors in reducing the outdoor air temperature and enhancing the microclimate in hot areas. Previous studies focused on studying Urban Heat Islands (UHI) on a specific level; this research investigates the impact of greenery on different levels and three types of UHI, pedestrian, canopy, and boundary, to provide a holistic image of greenery impact on the atmosphere. Further, whereas vegetation impact has been addressed in previous studies, no valuable study has been found that investigates the impact of vegetation within the local climate conditions of the UAE. In this research, different types of greenery will be investigated to find their impact on outdoor microclimate parameters and the UHI within the hot climate conditions of the UAE. The case study of this research is a boulevard located in Dubai; the International Media Protection Zone’s main boulevard was selected to simulate different scenarios based on vegetation type and Leaf Area Density (LAD) using ENVI-met. The results showed that 12 m trees and the cylindrical tree are the most effective vegetation in reducing the air temperature; the variation between these scenarios and the existing case reaches 0.70 °C and 0.66 °C, respectively. The 10 m trees also have an influencing impact on reducing the air temperature by 0.50 °C. The same vegetation types showed a positive performance in absorbing shortwave radiation. The reduction in the reflected wave compared to the reference case was 36.07 W/m2 and 31.45 W/m2 for the 12 m and 10 m trees, respectively. Furthermore, the reduction in air temperature of a proposed scenario can reach 2.41 °C, 1.12 °C, and 1.08 °C for the investigated UHI levels. The results of this study will provide a canyon greenery prototype, with optimized performance in hot, humid climate areas.

Effects of different types of acid rain on water stability of asphalt pavement

As is known to all, China is one of the countries with more acid rain in the world, and acid rain is mainly distributed in the southern humid climate area of China. However, the construction of semi-flexible asphalt pavement exposed to acid rain environment is a very realistic problem. In order to clarify the influence of different types of acid rain on the water stability of semi-flexible pavement, sulfuric acid type acid rain, nitric acid type acid rain and mixed type acid rain were prepared in this paper, and the semi-flexible specimens were soaked periodically. The water stability of semi-flexible pavement under different types of acid rain corrosion was evaluated macroscopically by standard Marshall test, immersion Marshall test, freeze-thaw splitting test and vacuum saturation test. It was concluded that the Marshall stability, immersion Marshall residual stability, freeze-thaw splitting strength ratio and vacuum saturation residual stability of semi-flexible pavement under different types of acid rain showed different degrees of decline.The reasons for the decline of water stability of semi-flexible pavement under different types of acid rain corrosion were analyzed by scanning electron microscopy and infrared spectroscopy. It was concluded that the acidification condition of rainwater was the main reason for the decrease of ductility, viscosity and plasticity of petroleum asphalt, which affected the binding force between petroleum asphalt and limestone aggregate, and ultimately led to the decline of water stability of semi-flexible pavement.Based on the molecular dynamics theory, the molecular dynamics model of acid rain corrosion asphalt mixture is established. According to the sensitivity of acid components to the main components of semi-flexible asphalt mixture, the asphalt, oil, resin and calcium carbonate with the most content in semi-flexible asphalt mixture are selected to simulate and study. The changes of bonding energy and diffusion coefficient of asphalt mixture under different types of acid rain are calculated and analyzed. It is concluded that sulfuric acid acid rain has the greatest influence on the water stability of semi-flexible specimens, followed by mixed acid rain, and the influence of nitric acid rain is relatively small.

Effect of Different Regions and Ensiling Periods on Fermentation Quality and the Bacterial Community of Whole-Plant Maize Silage.

This study aimed to explore the changes in the microbial community on the silage material surface and during the ensiling process of whole-plant maize in different regions. Whole-plant maize silages were sampled in Ziyun, Guanling, and Weinning counties within warm and humid climate areas in southern China. Silages were sampled at 0, 2, 5, 10, 20, and 45 days during ensiling. The nutritional components, fermentation properties, and microbiomes were examined to evaluate the influence of sampling area and fermentation time on the quality of silage. The results showed that the pH values of all silages significantly decreased (<4.2 at ensiling day 2) during fermentation and all silages achieved satisfactory fermentation at 45 days. Butyric acid was not detected during ensiling, and the contents of acetic acid and ammonia nitrogen in the final silages were below 6 g/kg DM and 50 g/kg total nitrogen, respectively. Weissella was the dominant epiphytic bacteria of raw material in Ziyun and Weinning, while Lactobacillus was prevalent in Guanling. Lactobacillus dominated the ensiling process, and its abundance significantly increased with increasing fermentation time in the three groups. Lactobacillus was negatively correlated with pH of all silages (p < 0.05) and positively correlated with lactic acid, propionic acid and acetic acid (p < 0.05). Furthermore, the bacterial community was significantly correlated with environmental factors. Altitude had a highly positive correlation with the abundance of Stenotrophomonas, Chryseobacterium, and Massilia (p < 0.01), while precipitation was negatively correlated with these bacteria. The humidity and average temperature significantly influenced the Lactobacillus and Weissella abundances of fresh whole-plant maize. During the ensiling process, the silages from three regions had similar bacterial dynamic changes, and the Lactobacillus formed and maintained good fermentation characteristics in whole-plant maize silage.

Evaluation of spatial comfort on vernacular architecture in Aceh Besar District as a form of local wisdom in adapting surrounding environment

Aceh is located in a warm humid climate area. It has high relative humidity, which averages almost 80% and an air temperature of 27.50C. This study aims to evaluate the structure and material of a vernacular architectural style of the Indrapuri Mosque, located in Aceh Besar district, in relation to spatial comfort. The representation of vernacular architecture in relation to spatial comfort is the implication of the local wisdom value in designing architecture that is adaptive to the surrounding environment. In terms of spatial comfort, the study focuses on examining thermal and daylight performances. In doing this, primary data were collected by conducting a field survey and mechanical measurement. In supporting primary data, written sources as secondary data that related to the study were reviewed. The study found that a few new building materials installed have affected spatial discomfort. These new materials create a high indoor thermal performance. Concerning daylight performance, the whole interior space of the mosque receives adequate sunlight. However, a few building materials that have been replaced with new materials have affected spatial discomfort.. The study thus shows that traditional buildings are still suitable to be used in the current time. To anticipate having high indoor temperature, the installment of new material through building conservation activities should pay attention to the character of new materials close to the original building material.

Microwave-assisted extraction of chlorophyll and polyphenol with antioxidant activity from Pandanus amaryllifolius Roxb. in Vietnam

Pandanus amaryllifolius Roxb., also called as pandan leaf, is distributed mainly in hot and humid climate areas. Pandan leaf, grown very popular in Vietnam, contains many biological value compounds such as chlorophyll and polyphenol with oxidation prevention activity. Microwave-assisted extraction (MAE) has advantages such as reduced extraction time and high extraction efficiency in comprison to other extraction technologies. The aim of this study was to assess the effect of microwave-assisted extraction conditions on chlorophyll and polyphenol content as well as antioxidant activity of pandan leaf. Research results show that acetone solvents of 90°, pandan powder: acetone ratio of 1:30, microwave capacity of 300W, microwave-assisted time of 2 minutes are parameters for the highest extraction efficiency. With these conditions, chlorophyll a, b and total chlorophyll content are respectively 9.4278 μg/mL, 4.2460 μg/mL, 13.6738 μg/mL, polyphenol content is 2.7577 g/L and DPPH radical collection activity 1409.51 μmol/L.

Isolation, identification and utilization of lactic acid bacteria from silage in a warm and humid climate area

The study aimed to isolate and identify lactic acid bacteria (LAB) from silages and their application to improve the fermentation quality of alfalfa. Forty-nine LAB strains were isolated from silages, and two strains were screened for growth and acid production rates. Then two strains were selected for Physiological and morphological tests and 16S rRNA sequencing. They were Gram-positive and Catalase-negative and were able to grow at pH 3.5 and at 45 °C, were unable to grow different NaCl concentrations as 3.0% and 6.5%. Strain BDy3-10 was identified as Lactobacillus rhamnosus, while TSy1-3 was identified as L. buchneri. The selected strains were evaluated on fermentation of alfalfa silage. The highest crude protein content occurred in the BDy3-10 treatment group. The contents of neutral detergent fiber and acid detergent fiber in the TSy1-3 treatment were significantly lower than other treatment (P < 0.05). Compared to the control treatment, inoculation treatments deceased pH during ensiling (P < 0.001) and provided the most increased lactic acid content after ensiling for 10 days (P < 0.001). The acetic acid contents of all the inoculation groups were significantly increased (P < 0.001) during ensiling, and were lower than that of control group (P < 0.001). So, the TSy1-3 treatment most effectively improved the fermentation quality of alfalfa silage in warm and humid climate area.

Investigating the Impact of Integration the Saudi Code of Energy Conservation with the Solar PV Systems in Residential Buildings

The demand for air conditioning is increasing day by day in the world’s hot and humid climate areas. Energy conservation in buildings can play a vital role in meeting this high cooling demand. This paper attempts to consider the impacts of energy efficiency and renewable energy measures on the energy demand of Saudi Arabia’s residential buildings. The energy analysis and economic feasibility analysis of thermal insulations are performed in this paper by investigating the effect of residential buildings’ thermal insulations on the economic feasibility of grid-connected photovoltaic systems. This was the combined effort of building owners and government, and buildings were examined if a photovoltaic system and thermal insulation were used. The study was conducted in the three climate zones in Saudi Arabia. The results showed that the building base case’s annual electrical energy consumption in Riyadh city was 67,095 kWh, Hail 57,373 kWh, and Abha 26,799 kWh. For the basic case-building in Riyadh, 69% of the total electrical energy was used for cooling and heating. Applying the Saudi Building Code requirement for Riyadh will provide only 18% of the total energy used for cooling and heating. RETScreen 6.1 software was used to design a photovoltaic system; the analysis was done using technical and economic indicators. The annual yield factor for Riyadh, Hail, and Abha was 1649 kWh/kWp/year, 1711 kWh/kWp/year, and 1765 kWh/kWp/year, respectively. The capacity factors for Riyadh, Hail, and Abha were 18.8%, 19.5%, and 20.1%, respectively. The Unified photovoltaic Levelized energy costs were 0.031, 0.030, and 0.029 $/kWh for Riyadh, Hail, and Abha, respectively. Finally, the Net Present Value and greenhouse gas emissions reduction have been estimated.

Passive Cooling Strategies for the Enhancement of Historical Buildings: A Comparison between Ventilation Chimneys and Courthouses

The balancing of protection needs and performance improvement are essential to keep in use valuable buildings. For this reason, it is fundamental to evaluate the effects on the energetic behaviour and conservation issues caused by retrofit measures in historical structures. The research aims at the performance improvement of Architectural Heritage promoting passive cooling strategies through a comparison between ventilation chimneys and historical courthouses. The architect J. R. Gordon (1863-1937) designed seventeen courthouses in Texas, twelve of which are still existing and functioning at this time. Reinterpreting the period’s attention in mechanical systems’ innovations for ventilation, cooling and heating, Gordon’s courthouse buildings exploits natural ventilation as a strategy for achieving buildings’ passive cooling, in the hot and humid climate areas of the Texas state, in a design process that evolved over time to become more technologically sophisticated and climatically efficient. This research investigates the design and construction features and climatic response strategies of Gordon’s different types of court houses, specifically examines and assesses their natural ventilation effects. This study discusses the climate-responsive approach, moving from already established models to the creation of new climate responsive typologies of ventilation chimneys through a process of typological metamorphosis.

Effect of moisture on the thermal performance of exterior walls in the tropical islands of the South China Sea

Accurate evaluation of the moisture effect on the thermal performance of building envelopes is essential to facilitate energy-saving building design in hot and humid climate areas. However, in extremely hot and humid climate areas, the coupled effect between the heat and moisture transfer is mostly neglected and a method to evaluate the moisture effect on the thermal performance has never been proposed. Thus, in this paper, a model is developed to simulate the coupled heat and moisture transfer inside an exterior wall subjected to extremely hot and humid climate. This model is validated using three benchmark tests and shows high accuracy. Based on the model, the effect of the moisture on the thermal performance of exterior walls in the tropical islands is firstly investigated quantitatively. The results show that moisture can substantially affect the thermal performance of an exterior wall. Neglecting the moisture effect, the total load is underestimated by 6.04–7.33%. Considering the moisture effect, the decrement factor is improved from 26.27–38.28 to 79.40–114.41 and the time lag is prolonged by 71–79 min. Finally, to clarify the spatiotemporal dynamic pattern of the moisture effect, a comparison between the four tropical islands and the continental city is performed.

Replacement Construction Technology of Collapsible Loess Subgrade in Typical Subtropical Humid Climate Area

Aiming at the problem of insufficient bearing capacity of collapsible loess in highway subgrade engineering, taking the second phase of KKH project in Pakistan as an example, Based on the analysis of the physical and mechanical properties of collapsible loess in this area and the actual situation of the project, the most effective construction technology is explored. The construction technology of replacing natural gravel is analyzed, and summarizes the actual operation of the construction methods, to provide some theoretical basis and construction reference for related projects. The results show that the design and construction requirements can only be met under the condition of strict implementation of the norms and standards, combined with the actual situation of the project, and the most effective construction technology explored can be applied to the construction of highway subgrade.

Exploring the suitable assessment method and best performance of human energy budget models for outdoor thermal comfort in hot and humid climate area

Global climate change and urban heat island intensification are making the outdoor environment more thermally uncomfortable during hot weather, and more dangerous during heat waves. This has generated considerable interest in the development of models to estimate the effect of heat on human bodies. However, it is not clear that which model provides the most accurate and precise results and which method could appropriately analyze the data. This study, conducted in Shanghai, China, compared the outputs of three of the most accepted human energy budget models with a database of 509 thermal sensation votes under various thermal conditions. We analyzed the results in three ways, including linear regression, curvilinear regression, and multinomial logistic regression assessment. Results showed that because thermal sensation votes are ordinal data, so the first two methods have theoretical limitations, while the latter method was determined to be the most appropriate for the data type of the three models tested. Further, in hot and humid climate area, we found COMfort FormulA (COMFA) is more accurate than Physiologically Equivalent Temperature (PET) and Universal Thermal Comfort Index (UTCI), thus it has more potential for use by urban designers in improving outdoor thermal comfort.