Hot-humid Areas Research Articles

Crop water requirement and irrigation scheduling of dry season irrigated crops in Pawe district, lowland hot humid area of Ethiopia

Knowledge of irrigation water requirements and irrigation time schedules improves irrigation water management and crop productivity in the field. The CROPWAT model calculates the ETo, CWR, and IRs to develop the irrigation schedules under different administration conditions and water supply plans. The objective of this study was to determine the crop water requirement of tomato, onion and soybean crops and their irrigation scheduling under local climate condition of Pawe district. Local climate, crop type and soil data were used as input data to determine crop water requirement (CWR) and irrigation scheduling. The finding of this study was crop water requirements of tomato, onion and soyabean were 547.7, 362.8 and 337 mm respectively per season on black clay soil of Pawe district. The obtained irrigation scheduling were twelve irrigation schedules for tomatoes, elven for onion and five for soybean. The study will help to improve the management of water resources and loss of crop productivity. This study can be used as a reference for decision-making for future irrigation scheme planning and irrigation water development of Pawe district.

Soil Physicochemical Properties and Caper (Capparis spinosa L.) Growth in Response to Various Mulches

ABSTRACT One of the sustainable and the most effective methods for controlling wind erosion is protecting the ground surface by mulching and vegetation cover. This study was done to assess the effect of organic and inorganic mulches and also compaction levels on soil properties and growth characteristics of caper plants, as one of the important shrubs to combat desertification in hot-humid areas. Results suggested that sugarcane bagasse and palm waste compost mulches significantly increased soil organic carbon (OC), nutrients (available nitrogen, phosphorus, and potassium), and moisture, and decreased soil electrical conductivity (EC), pH, and temperature. Petroleum mulch increased soil penetration resistance (69.50 kPa) and temperature (25.50). Petroleum and cement-slag mulch, and also their combination (petroleum-cement mulch) decreased soil moisture to the minimum extent. For either compaction level, using petroleum mulch increases penetration resistance. Compaction decreased soil moisture by 0.96% and increased total neutralizing value (TNV) and bulk density (BD) by 1.52% and 0.31 g cm−3, respectively. For either compaction level, soil porosity increased with the application of sugarcane bagasse mulch and palm waste compost. Using sugarcane bagasse mulch and palm waste compost increased stem length, leaf number, above ground and root weight, and shoot to root ratio of caper plant. Soil temperature (a = −0.70, R2 = 55.70%, P ≤ 0.001), EC (a = −0.87, R2 = 42.49%, P ≤ 0.001) and penetration resistance (a = −1.32, R2 = 17.03%, P ≤ 0.01) decreased with increasing soil moisture. BD (a = −1.20, R2 = 37.08%, P ≤ 0.001) decreased with increasing soil OC. Findings suggested the significant effect of organic mulches on improving some soil properties and growth characteristics of caper plants.

Thermal Environment and Energy Performance of a Typical Classroom Building in a Hot-Humid Region: A Case Study in Guangzhou, China

Buildings and the construction sector account substantially for global energy consumption. In hot-humid areas of China, suboptimal thermal comfort in classrooms has heightened their cooling load and energy consumption. It is necessary to renovate the buildings of outdated code according to the current weather conditions to save energy. This study thus aimed to examine the thermal effects of such designs on the cooling load, based on an actual classroom building during summers in hot-humid southern China. Using air temperature and PMV values to evaluate thermal comfort, this study conducted simulation through EnergyPlus and DesignBuilder. The resultant updated typical meteorological year (TMY) and the monthly and hourly analyses of indoor thermal comfort revealed persistent classroom overheating. To mitigate the cooling load, numerous design variables were investigated: space form, roofing, external walls, windows, and shading devices. Evaluative comparisons found that appropriate choice of external windows and shading devices represented the two most effective strategies in mitigating the cooling load. Furthermore, jointly applying effective retrofit strategies to the building yielded a favorable reduction in the annual cooling energy consumption by 16.6%. The findings herein are envisioned to provide evidence-based referential guidance for building designs for classrooms in a hot-humid climate.

Validations of CROPWAT Based Irrigation Practice for Tomato Productivity in Lowland Hot Humid Area of Ethiopia

The efficient management of applied water volume and wise water application is accomplished by irrigation scheduling. Microclimate is the most important factor affecting the irrigation schedule, which determines when and how much irrigation water will be used. The objective of this experiment was to validate the experimental effects of CROPWAT irrigation practice compared to farmer’s practice on crop and water productivity of tomato. The CROPWAT Penman–Monteith method was used to calculate crop water requirement and irrigation scheduling of tomato as compared to farmers irrigation practice. The total water applied were 1087.5mm and 1275.5mm for 2020 and 895.3mm and 1242.6mm for 2021 respectively for CROPWAT and farmers’ practice. The obtained validated result revealed that farmers' irrigation practices for marketable tomato fruit were 25.8% lower when based on CROPWAT irrigation practice, while those for unmarketable tomato fruit were 46.18% lower. In contrast to farmers' irrigation practices, the CROPWAT irrigation system can reduce loss by 46.1 percent for the production of tomato fruit. Similarly for tomato water productivity, CROPWAT-based irrigation systems received an incremental 37.5 percent advantage over farmers' practices. As a result, this study came to the conclusion that CROPWAT-based irrigation practices are crucial for field crop irrigation scheduling and crop water requirements. The study will contribute to bettering tomato fruit productivity and water resource management. This study might serve as a guide for making choices regarding upcoming planning.

Influence of Non-Constant Hygrothermal Parameters on Heat and Moisture Transfer in Rammed Earth Walls

As environment-friendly building materials, earth materials are attracting significant attention because of their favorable hygrothermal properties. In this study, the earth materials in northwest Sichuan were tested and curves of thermal conductivity and water vapor permeability with relative humidity were obtained. The function curves and constants of the two coefficients were substituted into the verified nonstationary model of heat and moisture transfer in rammed earth walls and indoor air for calculation. The difference in the calculation results when the hygrothermal parameters are functions and constants were analyzed, and the influence of the non-constant hygrothermal parameters on the heat and moisture transfer in rammed earth walls, was obtained. The test results show that thermal conductivity is linearly related to moisture content, and water vapor permeability has a small variation in the relative humidity range of 0–60% and increases exponentially above 60%. The calculation results indicate that the non-constant hygrothermal parameters have little influence on the internal surface temperature of the rammed earth walls and Mianyang City’s indoor air temperature and humidity during the summer and winter. The heat transfer on the internal surface will be underestimated by using a non-constant for the hygrothermal parameter when the moisture content of the wall is low, and vice versa. In hot-humid areas or seasons with large differences in temperature and humidity between indoors and outdoors, non-constant hygrothermal parameters have a more obvious effect on heat transfer on the internal surface of the wall. The results of this study demonstrate the necessity of parameter testing.

The Impact of Internal Courtyard Configuration on Thermal Performance Of Long Strip Houses in Hot-Humid Area of Hainan Island, China

The Impact of Internal Courtyard Configuration on Thermal Performance Of Long Strip Houses in Hot-Humid Area of Hainan Island, China

Effect of moisture transfer on heat transfer through exterior corners of cooled buildings in hot and humid areas

In building thermal calculation, the exterior corner is a typical thermal bridge. The heat flow through this part is more concentrated and significantly larger than that through the surrounding walls. The effects of moisture on heat transfer through corners are not taken into account due to the complexity of moisture transfer. Storage and transfer of moisture will change the thermal conductivity of porous building materials and lead to latent heat flow. Neglecting the effect of moisture transfer can contribute to large errors in the calculation of heat transfer through corners, especially in the areas with high temperature and humidity. Therefore, this paper mainly analyses the process of heat and moisture transfer in the exterior corners of cooled buildings in hot and humid areas. Different outdoor environments and corner structures influence the heat and moisture transfer in the corners. Simulation results are compared with the calculations that ignore moisture effects. In addition, two typical cities, one in hot-humid area and the other in cold-dry area, are compared under cooling conditions. Finally, the correction of the average thermal transmittance of the exterior corners was determined in major cities of China. The results show that the thermal bridge effect is aggravated by moisture transfer, and heat loss at the corner is significantly affected. The impact level is related to the outdoor relative humidity, column materials, column width and insulation thickness. The correction values of the average thermal transmittance of the exterior corners (7–25.6%) in hot and humid areas of China are generally higher than that in other areas. • The hygrothermal performance of building corners is analyzed. • Moisture effects on heat transfer under different conditions are quantified. • Simulation results in different areas are compared. • Correction of average thermal transmittance of corners is determined.

Effect of Land Use Changes on the Urban Surface Temperature in Umuahia Town, Southeast, Nigeria

The land surfaces of hot-humid tropical urban areas are exposed to significant levels of solar radiation. Increased heat gain adds to different land surface temperature profiles in cities, resulting in different thermal discomfort thresholds. Using multi-temporal (1986, 2001, and 2017) landsat data, this study examined the impact of land use change on urban temperature profiles in Umuahia, Nigeria. The findings revealed that over time, built-up regions grow in surface area and temperature at the expense of other land use. The transfer matrix, showed that approximately 59.88 percent of vegetation and 8.23 percent of bareland were respectively changed into built up during the course of 31 years. The highest annual mean temperature in built-up regions was 21.50°C in 1986, 22.20°C in 2001, and 26.01°C in 2017. Transect profiles across the landuses reveals that surface Temperature rises slowly around water/vegetation and quickly over built-up and bare land area. The study observed drastic changes in land cover with a corresponding increase in surface temperature for the period between 1986 and 2017 with consistent decrease in water bodies and bare land in the study area. Overall, the spatio-temporal distribution of surface temperature in densely built up areas was higher than the adjacent rural surroundings, which is evidence of Urban Heat Island. The impact of landuse change on urban surface temperature profiles could provide detailed data to planners and decision makers in evaluating thermal comfort levels and other risk considerations in the study area.

Cooling effects of a mist-spraying system on ethylene tetrafluoroethylene cushion roofs in hot-humid areas: A case study in Guangzhou, China

Ethylene tetrafluoroethylene (ETFE) cushion roofs are used for improving indoor natural lighting. However, their poor thermal insulation compromises the indoor thermal environment. Water spraying offers promising potential in roof cooling, but its cooling and shading effects on ETFE cushion roofs have not been examined. This paper on roof-mount spraying systems aimed to address this gap with numerical simulation and a full-scale field experiment. Our findings indicated that exterior surface temperatures of ETFE cushion roofs should be kept below 33.7°C to establish a thermally tolerable indoor environment. Secondly, under limitations of field conditions, decreases in exterior and interior surface temperatures yielded by the spraying system respectively ranged from 4.8°C to 19.5°C and from 0.2°C to 4.9°C. Thirdly, the shading effects generated by spraying have been insignificant, with the average solar radiation shading rate being only 0.23. Lastly, decreases in temperatures for both exterior and interior roof surfaces could be expressed as a function of only four parameters with good accuracy (R2 = 0.93 and 0.87, respectively). Decreases in exterior surface temperatures were most affected by exterior surface temperatures, followed by solar radiation, wind speed, and lastly the wet-bulb temperature, whereas decreases in interior surface temperatures were most affected by solar radiation.

Reduction of apparent temperature under urban trees in a hot-humid green area

A thermo-hygrometric analysis was carried out at 9, 12 and 16 hrs, under six groups of urban tree species with different levels of shading, plus a lawn as control area, on a hot and humid day of November 2018 in Campos dos Goytacazes, Rio de Janeiro. Air temperature and relative humidity data were converted into apparent temperature heat indexes (HI). The results obtained were subjected to analysis of variance and, if significant, a regression analysis was performed. Shading indexes were calculated using five fisheye photos taken under each group of tree species, in order to obtain a mean sky view factor (SVF) for each location. Values of SVF and HI of each different evaluation time were subjected to Pearson’s correlation analysis. There was a significant difference within the groups of trees at the three evaluation times. The maximum HI (43.91°C) was recorded at midday. On the lawn area, there was a significant positive correlation between the SVF and the HI at different evaluation times, and it was higher at noon. Increased sunlight exposure, due to decreased sky blockage, causes a significant increase in HI.

Study on Natural Ventilation Potential of Ordinary Office Buildings in Guangzhou Based on Architectural Factors

As a traditional architectural design technology, natural ventilation has the functions of improving thermal comfort, indoor air quality and energy saving, which is in line with the architectural development concept of green and healthy buildings.Guangzhou is located in the hot-humid area of Lingnan, where is rich in wind resources and attaches great importance to the natural ventilation of buildings. Natural ventilation potential (NVP) are evaluation indexes that can effectively assist and optimize the natural ventilation design of buildings. With abundant relevant studies at home and abroad, various NVP evaluation indexes and calculation methods have been proposed, and strategies for natural ventilation design of buildings in different regions have also been given. Based on the parametric building performance simulation platform, this paper introduces s new NVP evaluation method to carry out parametric simulation research on the ordinary office buildings suitable for natural ventilation in Guangzhou. The results showed that the main factors that limit the NVP of ordinary office buildings in Guangzhou is condensation in summer, and low building density, building toward southwest, high glazing ratio or cross ventilation will bring about high NVP. Meanwhile there is an optimal value for the thermal resistance of the roof, and the greater the thermal storage coefficient of the main material, the greater the night natural ventilation potential.

Developing a Calcium Silicate Prefabricated Board Ventilated Wall for Building Energy Efficiency Retrofit in Hot-Humid Areas

Ventilated wall is considered as an effective technique for building energy efficiency retrofit in hot-humid areas, and the heat exchange inside the ventilated layer blocks the heat gain into the wall. Most current researches focus on the performance assessment of the wall system but lack the optimize design of the external board. Here we demonstrated a new type of ventilated wall, using the calcium silicate material as the cladding panel for its excellent physical properties and easy installation and maintenance. In particular, the aluminum foil was attached to the interior side of the board to further lower the emissivity for achieving a better insulation effect. Based on the field experiment in summer days, the thermal performance of the new type of ventilation wall was obtained and further compared with the conventional wall. Moreover, the equivalent thermal resistance of this novel ventilated wall was also calculated. The results revealed that: the interior wall surface temperature and energy consumption of the new ventilated wall proposed was about 3-5°C and 39.2% lower than those of the conventional wall, respectively. The low emissivity significantly insulated the heat transfer inside the cavity. In parallel, the calculated equivalent thermal resistance of the ventilation wall (0.971m2⋅K/W) was also 2.07 higher than that of the conventional wall.

Thermal sensation under high-intensive exercise in naturally ventilated gymnasiums in hot-humid areas of China: Taking basketball players for example

As a public building for exercises and entertainments, gymnasiums play an important role in people's daily life. In regions with hot-humid climate, thermal sensation in gymnasiums is directly related to the human health as well as energy consumption. However, little can be found in the systematic evaluation system reported for thermal sensation of athletes in gymnasium in hot-humid climate regions; therefore, there is a need to develop a thermal sensation model for evaluating thermal sensation of athletes partaking sports in these environments. In this study, a field survey on thermal sensation of players in a basketball game was carried out in a naturally ventilated gymnasium in Guangzhou, China. The results showed that the human physiology and thermal sensation of subjects were highly different during active sport state. Moreover, the thermal sensation vote was increased with a rise in the air temperature, the mean radiant temperature and humidity ratio, while thermal sensation vote was reduced with an increase in the air velocity. The metabolic rate, systolic blood pressure and skin temperature were shown to have a positive correlation with the thermal sensation vote. According to the analysis, a predictive thermal sensation model, which has been developed by this study to estimate the thermal sensation under high-intensive sport activities in gymnasiums in regions with a high temperature and high humidity, was evaluated and validated.

Application of Ventilation Technology of Bamboo Houses in Modern High-Rise Buildings

<p>The principle of L-shaped natural ventilation system of bamboo houses, traditional buildings in the hot-humid area of Lingnan, China, is now widely applied in the design of modern high-rise buildings. Taking the typical building case, the office building of Guangzhou Zhujiang Power Plant as an example, this article studies the natural ventilation system by the experimental method of combining actual measurement and simulation. It is concluded that the application benefits of the natural ventilation system in high-rise buildings can be improved by forming a complete ventilation path, increasing the area of air inlet and the distance between air inlet and air outlet.</p><p> </p>

Effects of increased humidity on physiological responses, thermal comfort, perceived air quality, and Sick Building Syndrome symptoms at elevated indoor temperatures for subjects in a hot-humid climate.

Recently, studies suggest that the average indoor temperature is typically >30°C and that the maximum temperature can reach 37.5°C in hot-humid areas. However, the effects caused by increasing the humidity at high indoor temperatures are not clear. In this study, twelve female and twelve male subjects were exposed to different operative temperature (26.6, 30.6, and 37.4°C) and relative humidity (50% and 70%) in a climate chamber. Data concerning thermal sensation, perceived air quality, and Sick Building Syndrome (SBS) were collected during 190-min-long exposure to each thermal condition. Heart rate, respiration rate, respiratory ventilation rate, mean skin temperature, and eardrum temperature were measured. It was found that increasing the relative humidity from 50% to 70% at 26 and 30°C had no significant effects on the physiological responses, thermal comfort, perceived air quality, or SBS symptoms of the subjects. However, when the temperature was elevated to 37°C, the heart rate, respiration rate, respiratory ventilation rate, mean skin temperature, and eardrum temperature increased significantly as a result of the increase in the relative humidity from 50% to 70%. The subjects felt hotter and more uncomfortable, and they found indoor air quality was more difficult to accept. The subjects are acclimatized to hot environments and more tolerant to heat. Therefore, the results are applicable to the acclimated people living in hot-humid climate.

Thermal Performance of Vertical Courtyard System in Office Buildings Under Typical Hot Days in Hot-Humid Climate Area: A Case Study

Due to the different types of courtyards in vertical courtyard system (VCS), their impacts on thermal performance in office buildings may vary. To better understand this issue, this paper investigates the thermal performance impact of three typical vertical courtyards. A field case study was conducted in VCSs during two typical extreme hot days under hot-humid climate conditions. The results show that the vertical courtyards have significant cooling effects under hot-humid climatic conditions. Via testing on linear, integrated, and rooftop courtyard with fusion layout, the fusion one has an obviously positive impact on air temperature reduction (4.3 °C). Compared with the linear and integrated courtyards, the maximum air temperature difference of fusion layout is around 1.6 °C. The thermal radiation environment of the fusion layout was better than that of the other two (linear and integrated). Besides, the surface temperature of the pavements (wood panel) in the vertical courtyards can reach 47 °C, while the vegetation can lower it by 8 °C under the same weather conditions. These findings show that the courtyard with fusion layout is more suitable for extreme hot weather conditions.

Modeling the influences of layouts of residential townhouses and tree-planting patterns on outdoor thermal comfort in Bangkok suburb

In Bangkok, reducing the extreme heat in summer is a critical challenge for urban planners and researchers associated with the built environment. A significant cause of such extreme heat is the rapid expansion of residential development without corresponding planning and design. This work explores layout designs for residential townhouses, building geometries, and tree-planting patterns for enhancing outdoor thermal comfort in a Bangkok suburb. The microclimatic conditions of a total of 192 designs were simulated through modeling based on ENVI-met software. The climatic conditions were then transferred to the ENVI-met BioMET package to calculate the hourly physiological equivalent temperature (PET) values in a street canyon. The information was used to determine acceptable comfort conditions, as compared to an upper limit of outdoor thermal comfort from a prior work. It is found that the aspect ratio and street canyon orientation can significantly improve outdoor thermal comfort performance, as compared to increases in building density or decreases in tree-planting distance. Tree and building shade can reduce the PET value by 8.6 °C and 14.2 °C, respectively. For example, street trees can increase the outdoor thermal comfort conditions of an avenue canyon (H/W = 0.5–0.7) by up to 82%. However, building and tree shade cannot reduce the extreme conditions in E-W oriented canyons, as the overhead shade requires further protection from the angle of the sun's rays. The study's findings could assist in the development of new guidelines for the design and planning of residential townhouse projects for providing a cooler outdoor environment and comfortable conditions, especially in hot-humid areas of Bangkok.

Thermal comfort of people in a super high-rise building with central air-conditioning system in the hot-humid area of China

Built areas with centralized air conditioning systems have increased intensively in recent years in the hot-humid area of China's mainland. A longitudinal field survey was conducted in a super high-rise building with central air-conditioning system in Guangzhou for a whole year. Forty-four respondents participated in the survey; they were visited three times a week, and thermal comfort data on a large scale with sample size of 3,345 were obtained, containing indoor environmental parameters, personal factors, and subjective responses. The data analysis showed that the indoor environments varied in small operative temperature ranges of 22 °C–27 °C in summer and 19 °C–25 °C in non-summer months, with moderate relative humidity and an air speed of 0.1 m/s. The respondents’ clothing insulation changed in a narrow range of 0.55 clo to 0.60 clo in summer and in a wide range of 0.80 clo to 0.90 clo in non-summer months. The thermal neutral and acceptable operative temperatures were 27.9 °C and 22.0 °C– 29.5 °C in summer, and the thermal neutral temperature was 24.5 °C in non-summer months. A strong preference for a cooler environment was identified in summer. The PMV (Predicted Mean Vote) model was confirmed to be not applicable in, the adaptive thermal comfort theory is also applicable to people in centrally air-conditioned buildings. This study provides a better understanding of thermal comfort in centrally air-conditioned indoor environment, and it is beneficial to practices regarding the evaluation, design, and control of indoor environments for centrally air-conditioned buildings in the hot-humid area of China's mainland.

Thermal adaptation of the elderly during summer in a hot humid area: Psychological, behavioral, and physiological responses

Elderly demand for indoor thermal comfort and energy conservation is increasing in an aging society. To reveal the thermal responses of the elderly in a warm summer environment, a field study involving experimental measurements was conducted in Chongqing, China. The study included 333 subjects in 17 residential buildings and 119 subjects in 6 elderly nursing homes; it showed that elderly persons as passive users of air conditioners preferred cooling by natural ventilation. The mean thermal sensation vote was insensitive and lower than estimates obtained from the PMV model in warm environments. The physiological responses of eight elderly subjects (65 ± 3) were measured in a climate chamber at 18 °C and 34 °C and compared with those from eight college students (22 ± 1) and eight middle-aged subjects (50 ± 5). In this chamber, oral temperature, blood pressure, and heart rate of elderly and middle-aged persons were determined to be almost constant as the air temperature was changed to a hot/cold environment for 30 min, a different result from that of the young subjects. However, the skin temperatures for all age groups showed dependency with air temperature conditions, suggesting skin temperature as an optimal monitoring parameter for the entire population.

The synergistic effect of street canyons and neighbourhood layout design on pedestrian-level thermal comfort in hot-humid area of China

The traditional shophouse neighbourhoods (TSNs) appropriately integrated multiple variables of urban morphology for enhancement of pedestrian-level thermal comfort (PTC) in hot and humid climate zones. Understanding the synergistic effect of these design variables in TSNs on PTC is helpful for urban planners and designers. This research developed a prototype parametric TSN model to investigate the synergistic effect of four main variables: neighbourhood layout configurations, canyon type (alley, arcade street, boulevard), canyon axis orientation and canyon aspect ratio (HW). The data from the in-situ measurements in a TSN of Guangzhou in summer were used as the boundary condition for simulation in ENVI-met V4.3 and validation on the results. The Physiological Equivalent Temperature was adopted to assess PTC in different cases generated by the prototype parametric TSN model. The main findings are as follows: a) both arcade and greening had significant cooling efficiency for pedestrians, especially in East-West oriented streets; b) only the PTC in alleys was sensitive to all design variables; c) favourable PTC was shown in the neighbourhood with long East-West oriented arcade streets and that in square block layout with alleys; and d) the PTC in all boulevards dramatically responded only to HWs higher than 0.67.