Thermal Comfort In Hot Climate Research Articles

A Systematic Review of Passive Cooling Methods in Hot and Humid Climates Using a Text Mining-Based Bibliometric Approach

The number of scientific papers has dramatically increased in recent years; however, such a huge number of papers often become difficult to review qualitatively because of limited time and cost. A text-mining-based bibliometric analysis method is developed to provide a comprehensive overview of passive cooling methods used in buildings in hot and humid climates. First, a comprehensive overview analysis is conducted to clarify the trends in studies on passive cooling methods between 1970 and 2022, using 39,604 publications. Second, 15 coding rules are constructed to perform a detailed analysis, and possible combinations of passive cooling methods are discussed. The detailed analysis of the co-occurrence network based on the comprehensive overview and 15 coding rules shows that the recent studies on thermal energy storage have mainly focused on phase change material (PCM), which is a latent heat storage material, rather than sensible heat storage materials such as concrete. The analysis of the co-occurrence network indicates that natural ventilation maintains the vital role of passive cooling methods by improving thermal comfort in hot climates. The constructed method and possible combinations of passive cooling methods for hot and humid climates will help engineers find effective combinations in the planning stage.

Evaluation of thermal comfort and urban heat island through cool paving materials using ENVI-Met

In urban literature, outdoor thermal comfort in hot climates is affected by different aspects, such as the size of the built environment and the variety of ground surface materials. Developing the outdoor thermal environment is crucial for achieving a balanced microclimate and creating a sustainable open space. This paper aims to provide thermal comfort and to promote sustainable urban development in Alexandria city (Egypt). The city faces problem of an increasing urban heat island, which influences the behavioral patterns of pedestrians. The case study of El Mosheir Street measured different simulated scenarios using ENVI-met 4.0 to achieve maximum thermal comfort. The results provided solutions through paving materials that present a high percentage of the city’s urban areas. The paper explained the concept of the urban heat Islands phenomenon and its mitigation strategies using paving materials.

The effect of urban shading and canyon geometry on outdoor thermal comfort in hot climates: A case study of Ahvaz, Iran

This study investigated the role of urban geometry and urban shading in improving the pedestrians’ thermal comfort in hot climate of Ahvaz, Iran. Six urban canyons are selected in Ahvaz. To determine the outdoor thermal comfort range, micrometeorological measurements and questionnaire survey were conducted in July 2018. ENVI-met is used to investigate the role of urban geometry and urban shadings. To evaluate the outdoor thermal comfort, physiologically equivalent temperature (PET) is calculated using RayMan. Using the results of the field studies, the outdoor thermal comfort range in Ahvaz is obtained within 19.6 °C to 30.9 °C PET. Simulation results show that the closer the canyon orientation is to the north-south direction, the lower the air temperature (Ta) and mean radiant temperature (MRT) are. Also, by reducing the canyon aspect ratio, PET increases as well. Urban shadings decreased MRT and PET up to 34 °C and 17.6 °C, respectively. In contrast, shadings did not affect the air temperature, significantly. PET reduction caused by shadings is more notable in east-west canyons, as well as in wider canyons. MRT and PET in all cases are highly correlated to SVF. The observations showed no strong correlation between Ta, relative humidity, and wind speed, with SVF in all canyons.

The effect of trees on human energy fluxes in a humid subtropical climate region.

Trees are considered to be an effective tool for improving human thermal comfort in hot climates and have been widely used in landscape architecture. However, it is not always clear how trees affect human-environment energy fluxes. In this study, an in-depth analysis of four common tree species was undertaken based on comprehensive field measurements, in terms of how each tree and its characteristics affected the energy fluxes of a person in a humid subtropical climate region. Results showed that the largest effect of trees was on radiation fluxes, with a much smaller effect on the convective and evaporative fluxes. For a person standing in shade, a tree can reduce approximately 25% of the absorbed radiation compared with an open reference point. Moreover, the cooling effect on radiation components was found to be greater in the solar radiation domain than in the terrestrial radiation domain. Solar radiation and ground surface temperature had the largest effect on a human energy budget, which was affected by characteristics of the trees and the thermophysical properties of ground surfaces. The effect from relative humidity and wind speed was quite minimal. For the four common tree species in this study, Ficus microcarpa had the best thermal performance by reducing the most absorbed solar radiation flux. This study shows a detailed empirical research about the thermal effects of trees on a person, providing recommendations for tree species selection in urban design.

Numerical modeling of outdoor thermal comfort in 3D

With the rise in urban air temperature, heat stress and thermal discomfort are challenging the livability of urban environments. To respond to this concern, we employ numerical modeling to evaluate the spatial and temporal variabilities of thermal comfort and introduce a simulation tool: outdoor thermal comfort in 3D (OTC3D). The model builds upon the work by Nazarian et al., 2017, and is a) extended to evaluate realistic urban configurations, b) validated against measurements, c) enabled to intake a wide resolution range of microclimate parameters (modular approach), and d) made available on an open-source platform. Using OTC3D, we evaluated outdoor thermal comfort (OTC) in two urban configurations: idealized and realistic. In the realistic configuration, we demonstrate the functionality of the model in presenting the variability of OTC in an urban neighborhood. Using the idealized configuration, on the other hand, we performed sensitivity studies regarding the effects of urban density and realistic surface heating. First, we observed that thermal comfort changes non-monotonically with urban density, as the ensuing change in wind speed and radiation patterns have counteracting effects on thermal comfort. Accordingly, to achieve the desired thermal comfort in hot climates, strategies to enhance urban ventilation are favored in higher densities, while strategies to minimize radiation are needed for lower urban packing densities. Furthermore, we observed that realistic distribution of surface temperature is critical when urban density is high (e.g. λp = 0.44). Therefore, approximations of surface temperature found in existing thermal comfort models are not suited for high-density urban areas. This further motivates the modular approach to improve the accuracy of thermal comfort analysis.

Effect of windexchanger duct cross-section area and geometry on the room airflow distribution

In this work, the effect of duct cross-section area and geometry, square and rectangular, of a windexchanger (WE) on the room airflow distribution is studied for a room with a window, at windward or leeward. Airflow distribution inside a room produced by natural ventilation is an important bioclimatic architecture strategy for thermal comfort in hot climates. Ten different WE types at different wind directions, resulting in 18 cases, are experimentally evaluated using scale models in a water channel and velocity measurements at the vertical central plane obtained by stereo-particle image velocimetry. The homogeneity index, the area percentage with a significant flow speed, the normalized turbulent kinetic energy and the normalized ventilation flow rate are used as evaluation parameters. It is demonstrated that in general by increasing the duct cross-section area of a given windexchanger, the windexchanger performance improves, the exceptions are when the openings of the WE have mixed functions, i.e. injection and extraction. Nevertheless, more important than the areas ratios are the configuration of the WE and the location of the window. The WEs show a better performance when all their openings have an opposite function to that of the window.

Thermal Insulation of Low-Cost Housing in Egypt

A common fault of architects and building designers in Egypt has been to produce buildings, particularly at the low-cost end of the market, with little regard to the climatic conditions that prevail. Satisfactory internal condi tions are achieved by using mechanical systems which in crease the initial capital cost of the building. In low-cost hous ing, artificial control over energy gains by means of air- conditioning is clearly not feasible on economic grounds. This paper discusses the criteria for thermal comfort in hot climates and reference is made to the BRE method of com putation of internal temperatures in tropical buildings, which has been validated by observations in Egypt. The effects of thermal capacity and insulation in buildings in hot climates are also discussed.