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Summary: The evaporative cooling technique is an efficient approach for cooling application. This study aims to establish a performance evaluation method to advance the appropriate design for multistage indirect evaporative cooling systems. A mathematical formulation has been developed for the indirect evaporative cooler (IEC). After the validation, the mathematical model was used to analyze the evaluation criteria by considering the simultaneous influence of the cooling effectiveness, the pressure drop, and the cooling capacity of the multistage IEC operating in two modes. The Mode‐1 IEC is a conventional counterflow unit, while the Mode‐2 IEC employs a regenerative M‐cycle arrangement. The IECs are operated in a tandem arrangement. The multistage system is capable of improving the cooling performance and reducing the outlet air temperature. In addition, the multistage system displays a higher pressure drop resulting in a lager consumption of fan power. The analysis of performance evaluation criteria indicates that the appropriate maximum stage is suggested to be three‐stage and two‐stage for the Mode‐1 and the Mode‐2 IEC, respectively. [ABSTRACT FROM AUTHOR]

Urban vegetation is an important factor for urban heat island mitigation, which also contributes to indoor cooling energy reduction. In this study, a one-way coupled simulation method which linked the ENVI-met and Energyplus models was developed to evaluate the impacts of urban vegetation on micro-climate parameters and the building cooling energy consumptions. The simulation results from 27 cases (three typical scenarios with nine vegetation configurations) under extreme hot weather in the summer of Xi'an city, China were compared and analyzed. Compared to that in high-rise blocks, the vegetation in low-rise blocks showed a larger potential at cooling-energy saving. The maximum air temperature reduction around the buildings reached to 0.40 °C, the maximum mean radiant temperature reduction reached to 1.78 °C, and the sensible cooling load of some thermal zones dropped by 2.13%. Although the overall effect of vegetation on decreasing the district cooling load is positive, the evaporation effect and the limited area of vegetation cooling may induce a limited rate on the cooling energy saving, especially in the high-rise blocks. This study provides a method for evaluating the potential of environmental and energy-saving benefits of vegetation planting in different urban blocks, and the result is valuable for planners to balance the costs and benefits of green configurations. • A coupled model was developed to evaluate microclimate impact on building energy. • The cooling mechanisms and benefits of planting in different scenarios were analyzed. • Planting brought a 2.13% (1.81%) sensible (latent) cooling load change in maximum. • The overall energy saving potential by planting in different districts were evaluated. [ABSTRACT FROM AUTHOR]

• Results from 33 measurement points in 5 selected urban districts were analyzed. • Urban morphology explains 34% of the variation in air temperature. • Suggested morphological indices are proposed to mitigate the high temperature. • 20m buffer zone is proper to analyze microclimate in high anthropogenic heat areas. • The microclimatic prediction models were established for sustainable development. The negative impacts of urban heat island (UHI) have attracted more and more academic attention. Currently, few studies have considered the effects of anthropogenic heat emission (AHE) in different urban districts. To explore the spatial and temporal differences in microclimate in high-AHE areas, five high-anthropogenic-heat-emission blocks in Xi'an, China were selected, and the microclimatic indices of air temperature (AT) and relative humidity (RH) were measured in 33 urban points in the five typical urban blocks. Meanwhile, the urban morphological indices of 33 points were calculated in the 20 m and 50 m buffer areas (BAs). Results show that the green cover ratio (GCR), the impervious surface area ratio (ISAR), sky view factor (SVF) and reflectivity (REF) were important variables affecting microclimate. These indices explained up to 35% and 31% of the changes in AT and RH, respectively. In addition, the ISAR should be controlled within 44% and the REF should be controlled above 21.5%, in order to ensure that the maximum AT remained less than 37°C (high-temperature orange warning) inside the block on a typical summer day. This study improves the prediction method of high summer temperatures in high-AHE blocks and provides hints for developing UHI mitigation strategies. [ABSTRACT FROM AUTHOR]

Increased artificial constructions due to urbanization absorb more solar radiation, making urban surface and air temperatures rise and affecting the energy performance of urban buildings and the human health. Many studies have reported that green facades and roofs, materials with high albedos can noticeably reduce building surface temperatures and cool the air in summer. However, little is known about the cooling effects and assessment of different mitigation strategies when they are adopted in a block scale. This study focuses on assessing and comparing the effects in the high-rise communities in Xi'an, China, which are a good representation of the city because they are composed of a high density of buildings, and they cover the majority of the current urban sprawl land. Simulations of three community prototypes through ENVI-met software were carried out in order to assess the mitigation techniques in terms of the ground surface, building surface, and vertical canopy air temperature decrease. The main techniques adopted were cool pavements, cool coating facades and roofs, green facades with ivy and green roofs with funkia and 15 cm substrates, and combinations of those. The statistical analysis results revealed that green roof can cool the roof more than the cool roof, while cool facade can cool the facade more than green facade. As to single mitigation strategy, the cool pavement have the most significant potential to decrease canopy air temperature. In general, the combination of different strategies had much more positive effects than single solution. These positive results indicate that the cooling strategies are urgently needed in the current urban construction to alleviate the urban heat island effect. Image 1 • The cooling potentials of various strategies and their combinations were compared in three high-rise community. • The performance of computational simulation software ENVI-met were tested by comparing measured data. • Decrease of land surface temperature, building surface temperature and canopy air temperature were achieved and evaluated. • The community characteristics affect the cooling effects. [ABSTRACT FROM AUTHOR]