Rong Hu

Tree-lined spaces as informal communication areas and important pathways for pedestrians are the second largest zones on university campuses, and they have a large impact on the microclimate. At present, the effects of the spatial form for tree-lined boulevards on microclimates have not been investigated. Thus, this study applied experimental and simulation methods to investigate the effects of tree-lined boulevards on microclimates in hot summer and cold winter regions. The main meteorological parameters including air temperature, relative humidity, wind speed, and solar radiation of the boulevard were obtained by experiments. Furthermore, the experimental data as a boundary condition were input into ENVI-met software to investigate the effects of the aspect ratio and canopy diameter of double-row open-canopy boulevards on microclimate regulation. The results showed that when the aspect ratio was reduced from 1.5 to 0.9, the temperature and UTCI increased by 0.047 °C and 0.21 °C, while relative humidity decreased by 0.227%. Decreasing the aspect ratio can effectively improve the microenvironment. As the canopy diameter increased from 7 m to 11 m, the temperature and UTCI of the boulevard space decreased by 0.064 °C and 0.45 °C, while relative humidity increased by 0.245%. An increase in canopy diameter is unfavorable to the improvement of microclimates. This study aims to provide a scientific basis for the design and improvement of tree-lined boulevards on university campuses.

Radiant cooling floors combined with ventilation systems have been widely applied in large space buildings. However, there has been a lack of research on system control strategies for their adaptation to weather changes. This study aimed to find control strategies for radiant cooling floors combined with displacement ventilation systems used in large space buildings in order to achieve energy conservation and environmental improvement. Supply air temperature and cooling surface temperature were determined to be the control variables. It was found that cooling capacity of the combined system and the comfort index, PMV (predicted mean vote), were linear in relation to the supply air temperature and cooling surface temperature. The linear equations regarding cooling capacity and PMV were established separately using environment data, and then the optimal region was determined. A case study on Terminal 3 of Xi’an Xianyang International Airport was conducted. The thermal environment was investigated through on-site measurements, questionnaires, and numerical simulations with CFD (computational fluid dynamics). It was found that supply air temperature and cooling surface temperature had a significant impact on PMV, and less impact on the cooling capacity. Therefore, it was determined that the supply air temperature should be altered first when the indoor temperature exceeds the upper limit, and then the cooling surface temperature should be changed if the indoor environment continues to overheat with the supply air temperature set to 18 °C. Thus, the supply air temperature was kept at 18 °C, and the floor surface temperature was set to be 22 °C on a high-temperature day. The average PMV was 0.87, and the cooling capacity of the combined system was 200 W/(m²·K), according to the CFD simulation. In addition, the surface heat transfer coefficient of the cooling floor was found to be 10.26 W/(m²·K). This research provides important references for the design and operational management of radiant cooling floors in large space buildings.

Due to their benefits in interior thermal comfort, energy saving, and noise reduction, radiant cooling systems have received wide attention. Radiant cooling systems can be viewed as a part of buildings’ maintenance structure and a component of cooling systems, depending on their construction. This article reviews studies on heat exchange in rooms utilizing radiant cooling systems, including research on conduction in radiant system structures, system cooling loads, cooling capacity, heat transfer coefficients of cooling surfaces, buildings’ thermal performance, and radiant system control strategy, with the goal of maximizing the benefits of energy conservation. Few studies have examined how radiant cooling systems interact with the indoor environment; instead, earlier research has focused on the thermal performance of radiant cooling systems themselves. Although several investigations have noted variations between the operating dynamics of radiant systems and conventional air conditioning systems, the cause has not yet been identified and quantified. According to heat transfer theory, the authors suggest that additional research on the performance of radiant systems should consider the thermal properties of inactive surfaces and that buildings’ thermal inertia should be used to coordinate radiant system operation.

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.

Cooling load is difficult to predict for a radiant system, because the interaction between a building’s thermal mass and radiation heat gain has not been well defined in a zone with a cooling surface. This study aims to reveal the effect of thermal mass in an external wall on the transmission load in a space with an active cooling surface. We investigated the thermal performances in a typical office building under various weather conditions by dynamic simulation with Energy-Plus. It was found that the thermal mass in the inside concrete layer had positives in terms of indoor temperature performance and energy conservation. The peak cooling load of the hydronic system decreases 28% in the proper operating state, taking into account the effect of the thermal mass in an external wall. Compared to the performances in zones with equivalent convective air systems (CASs), the peak cooling load and the accumulated load of the combined system (radiant system coupled by fresh air system) are higher by 9%–11% and 3%–4%, respectively. The effect of thermal mass is evident in a transient season with mild weather, when the relative effects are about 45% and 60%, respectively, for a building with radiant systems and a building with equivalent CASs.