Search

Buildings on tropical islands in the South China Sea are facing an overheating challenge. High-water-absorbency unglazed porous ceramic (UPC) materials could counteract heat gain by evaporation. Salty humid air and seawater in the marine environment lead to evaporative cooling differences from inland conditions. This research replicated a salty humid atmosphere with a stable concentration similar to the actual environment in a dynamic hot-humid climate wind tunnel (DHWT). The influence of salt in gas-liquid media on evaporative cooling is discussed. The results showed that the salt concentration of humid air in the wind tunnel can be controlled by adjusting the atomization rate and the concentration of the atomized liquid. Humid air and liquid with salt reduced the evaporation rate of the UPC tiles. The influence of salty humid air was generally less than that of seawater. In 6 mg/m3 salty air, the total evaporative cooling effect decreased by 2.63% and 40.44% when saturated with fresh water and a 3.5% sodium chloride solution, respectively, relative to saturation with fresh water and evaporation in humid air without salt. In conclusion, sea salt in humid air and in the liquid phase reduced but did not eliminate the evaporative cooling effect of UPC materials. Seawater source utilization showed a significant benefit in cooling and water conservation aspects in coastal areas.

Pervious pavements are efficient in the mitigation of urban heat island effects. Many studies have revealed the water availability of pervious paving materials dominates the evaporative cooling effect. However, the water retention capacity of these materials is affected by the water absorption capability, which has scarcely been investigated in relation to evaporation. Therefore, this study investigates the water absorption capability of pervious paving materials and its influence on evaporative cooling performance. We examine the water absorption capability of three similar-coloured materials, including sintered ceramic pervious brick (CB), pervious concrete brick (PB), and open-graded pervious concrete (PC), as well as their evaporative cooling performance under a steady-state hot-humid environment in a climatic wind tunnel. The results indicate that: (1) CB had the highest water absorption coefficient of 2.04 kg/m2·s0.5, which is approximately about 30 and 200 times higher than that of PB and PC, respectively; however, these materials had similar water retention capabilities, with a capillary moisture content of 110 ± 10 kg/m3, revealing that CB could hold more water in a very short time; and (2) CB and PB could effectively reduce the surface temperature by up to 20 °C and 12 °C with a cooling period of 16 h and 12 h, respectively. In comparison, PC demonstrated a weak cooling effect of 2 °C, which only lasted for 4 h. Overall, materials with a high water absorption capability can maintain hydraulic continuity balance for a long time, which is beneficial to enhancing evaporation and further lowering the surface temperature.

Pervious pavement system (PPS) is a suitable alternative technique for mitigating urban flooding and urban heat island (UHI) simultaneously. However, existing literature has revealed that PPSs cannot achieve the expected permeability and evaporation. To overcome this gap, this study presents an elaborate review of problems associated with PPSs and highlights its benefits to stormwater management and UHI mitigation. We determined key parameters of PPSs that could influence urban flooding and UHI mitigation, including hydrological properties, thermal physical properties, structure design, and clogging resistance. We identified the co-benefits approach of PPS towards performance synergism on stormwater management and UHI mitigation from quality controlled design and fabrication, periodic maintenance, and effective evaluation system based on practice environments. The results indicate that existing studies of PPSs primarily focus on permeability, while little emphasis is given to the evaporative cooling performance, leading to a biased development with a loss of test standards and regulations that cannot control the cooling potential of the system. The performance synergism of permeability and evaporative cooling in PPS should be studied further, while considering quality control of the materials and in-situ practice design. Parameter controls (with commonly used standards) during fabrication, periodic maintenance (during operation), and pre- and post-evaluation processes of PPSs should work collectively to achieve optimal benefits and reduced costs.

Permeable pavements are effective in mitigating the urban heat island effect via evaporative cooling and have been widely used in south China. However, few studies focus on the impact of evaporative cooling of different permeable paving materials on the outdoor thermal environment. In this study, two widely used permeable paving materials, sintered ceramic porous brick (CB) and open-graded permeable concrete (PC) were investigated. First, partial immersion tests were performed to characterize the water absorption properties of these materials. The results indicated that CB had a higher water absorption rate and a larger water retaining capacity than PC. Then, field measurements were conducted to evaluate the evaporative cooling performance of these materials. The results indicated that (1) water absorption capacity has an important impact on the evaporative cooling effect of permeable materials, a high upward capillary force could maintain the hydraulic continuity over a long distance, thus effectively prolongs the first stage of evaporation, (2) sprinkling water could reduce the surface temperature of both CB and PC by up to 10 °C and lower the ratio of sensible heat flux to the net shortwave radiation of CB and PC to 13.12% and 29.62%, respectively, (3) compared to non-sprinkling conditions, the maximum air temperature above CB and PC could be decreased by up to 1 °C. Additionally, CB could lower the black globe temperature and wet-bulb globe temperature (WBGT) of 0.5 m by up to 3 °C and 2 °C after sprinkling, respectively, suggesting that sprinkling water can improve thermal comfort above pavements.

The evaporative cooling of porous building materials is one of the passive strategies used for building energy conservation. The effect of evaporative cooling strongly depends on the evaporation rate, which is defined as the mass of water evaporated from a unit area of a porous material per unit time. In contrast to previous studies, which focused on the influence of material properties on the evaporation rate, the present work investigates the effects produced by climatic factors. In particular, porous clay tiles with pore sizes of 2.0–6.0 µm and porosity of 27.34% were selected as water storage media, and the impacts of four climatic factors (air temperature, solar radiation intensity, wind velocity, and partial pressure of water vapour) were examined at three different levels. The obtained results indicate that the evaporation process from porous tiles consists of constant evaporation rate, falling evaporation rate, and low evaporation rate stages. Moreover, by conducting range analysis, the studied factors can be ranked by their impact on the evaporative cooling process as follows: the intensity of solar radiation, air temperature, partial pressure of water vapour, and wind velocity.

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.

Outdoor thermal measurement is the most direct and accurate technique to investigate and assess urban overheating. Thanks to operational convenience and low costs, mobile measurements are regarded as more efficient than fixed measurements. However, the accuracy of mobile measurements has not been adequately studied, especially given the lack of a standardized method for “stop-and-go”. This paper aimed to develop an optimized method suitable for mobile measurements. By comparing data from mobile and fixed points, the settling time, the effective period, and the staying time of air temperature (Ta) and black globe temperature (Tg) were elucidated. Further verification and application of this optimized method was achieved. The results show that: (i) the spatial transformation caused initial differences for both Ta and Tg, which could be reduced by average settling times of 3.1 min and 4.6 min, respectively; (ii) elimination of the data in the first 5 min improved the result accuracy of Ta by 20 % and Tg by 30 %; and (iii) a staying time of 10 min could afford acceptable result accuracy. In short, through regulating the settling time and staying time, the optimized method for mobile measurements could achieve excellent result accuracy on thermal environments in complex urban spaces.

Urban pipe rack is a type of underground tunnel used for centralized laying of municipal pipelines in cities. In this study, the effort of using urban underground pipe rack to preheating or cooling ambient air for building thermal comfort as a new passive energy saving method was made. This is similar with the existing earth to air heat exchanger (ETAHE). In the research, a long-term static air temperature and humidity test and ventilation experiments in summer/winter were carried out in the underground pipe rack located in Guangzhou, the thermal performance of the pipe rack which includes temperature performance, cooling and heating potential was also made. The static air temperature in the pipe rack is lower than ambient temperature in daytime in summer and higher than ambient temperature all day in winter. After air flowed through 200-meter pipe rack, its maximum temperature drop and rise in summer and winter could reach 7.5 °C and 11.2 °C respectively. The daily average cooling potential in summer and heating potential in winter of the 200-meter pipe rack was 467.3 MJ and 1418.6 MJ respectively. The COP of the pipe rack was found to be 2.4 in summer and 2.7 in winter. Results show the potential of pipe rack in providing low energy cooling and heating.

Evaporative cooling from porous building materials is one of the passive strategies used for building energy conservation. In this study, a porous clay tile (PCT) with specific pore size and porosity characteristics was selected as water storage medium. A composite construction, comprising the PCT, a waterproof coating, a cement mortar layer, and a base layer, was manufactured and its performances as an evaporative cooling structure were evaluated. First, the water absorption properties of the tile were characterized using a partial immersion test, from which the water absorption coefficient and the capillary water content were determined. The solar evaporative cooling performance of the composite construction was then investigated using a special wind tunnel, which allowed controlling the temperature, relative humidity, wind velocity, and simulated solar radiation conditions. The porous clay tile exhibits a relatively high water absorption rate, with a water absorption coefficient of 0.3286 kg/m 2 ·s 0.5 . Although the water retaining capacity of the tile (as represented by a capillary water content of 168.7 kg/m 3 ) was not outstanding, the composite construction still produced significant evaporative cooling when water was applied on the PCT. In cyclic experiments performed inside the wind tunnel, the energy balance analysis revealed that, even though the shortwave radiation absorbed by the surface of the wet specimen was larger than that absorbed by the dry specimen surface, 80% of the radiation absorbed by the wet specimen was transformed into latent heat flux, which decreased the external surface temperature by up to 11 °C and reduced the internal surface heat flux by 67.7%.

The evaporative-cooling roof is a popular passive energy conservation technique. This article presents a novel approach for modelling and analysing the influence of evaporation on roof thermal performance. A multivariate nonlinear model was developed for the prediction of the evaporation rate from porous tile. A computer program was then developed based on the one-dimensional roof unsteady heat transfer theory. Finally, the computer program and hourly weather data of Guangzhou, China, were used to analyse the impacts of evaporation (including the evaporation start time and water-application frequency) and slope orientation on roof thermal performance. Evaporation beginning at 11:00 can reduce the external surface temperatures of a horizontal roof and 30°-inclined east-sloping and west-sloping roofs by up to 11.3, 10.7, and 9.8 °C, respectively, from those of a non-evaporative roof. This, in turn, can reduce the peak-hour (16:00–20:00) internal surface heat flux. Additionally, with the horizontal roof, the reduction in the peak-hour heat flux can be doubled if the evaporative layer is frequently replenished with water.

Vertical green facades (VGFs) are one of the most promising technologies for reducing building energy consumption and mitigating the urban heat island phenomenon. Many studies have investigated the cooling effects of VGFs; however, research on the thermal behavior of VGFs and the impacts on indoor and outdoor thermal environments are scarce, which limits the understanding and application of VGFs. Therefore, field measurements were conducted in the subtropical city of Guangzhou, China, during hot days. First, the thermal balance of the vegetation canopy was investigated. In particular, the net photosynthesis and transpiration of foliage were measured to estimate the thermal effect of plant physiological activities. Moreover, the operative temperature (OT) and wet bulb globe temperature (WBGT) were measured to assess the comprehensive effects of the VGF on the indoor and outdoor thermal environments, respectively. The results indicated that transpiration could consume approximately 50% of solar radiation absorbed by the vegetation canopy. Furthermore, the thermal effect ratio of net photosynthesis to transpiration was less than 5.5%, suggesting that omission of the thermal effect of the net photosynthesis of climbing plants in thermal balance calculations could result in an error lower than 2.9%; such a low error may be acceptable for most engineering applications of VGFs. The VGF caused a decline in room air temperature and mean radiation temperature, resulting in a peak OT reduction of 3.6 °C. Moreover, the peak WBGT in the outdoor environment could be reduced by up to 2.7 °C due to the shading effect and transpiration cooling of the VGF. These findings help advance our understanding of the thermal transfer process of VGFs and extend the application of VGFs from a single cooling purpose to comprehensive improvement of the thermal environment.

Building evaporative cooling is an effective energy saving technology. With the aim to provide a reliable experimental method for the building evaporative cooling research, the dynamic evaporating and heat transfer process of two samples were studied by using the Climatic Wind Tunnel (CWT). The results of this study indicate the following: (1) The thermal resistance of the wet sample was two times that of the dry sample, which significantly improved the thermal insulation capacity of the wet sample. (2) The Penman–Monteith (P–M) model in Pedology was introduced to analyze the evaporation amount which was caused by the comprehensive effect of radiation term and aerodynamic term. The results displayed that the evaporation amount caused by radiation term accounted for 80.4% of the total evaporation amount. (3) The hourly evaporation data were used to calculate the heat balance equation on the facing layer of the wet sample. The calculation results demonstrated that the evaporating process can consume approximately 70% of the maximum incident solar radiation heat.

Airflow utilization is a traditional and effective way for people to improve their thermal comfort in summer in the areas of China that are hot and humid. We conducted a summer-long field study on nine naturally ventilated buildings in Guangzhou and collected airflow-related behaviors, motivations, and perceptions from 32 college students. The results show that the behaviors of opening windows and doors were driven by both indoor air quality and thermal comfort motivations. The proportions of open windows and doors increased linearly and slowly with the indoor ET*, and the acceptable range for opening windows and doors was an indoor ET* ≤30.3 °C with the condition that a maximum of 0.25 m/s indoor air speed needs to be achieved. The behaviors of using fans were driven by thermal comfort motivations. The proportions of use of fans increased strongly with the indoor ET*, and the acceptable range for using fans was an indoor ET* ≤31.0 °C with the condition that a maximum of 0.87 m/s indoor air speed needs to be achieved. A strategy for airflow utilization was proposed. Our study is believed to provide a better understanding of airflow-related behaviors, motivations, and perceptions as well as better designs of natural ventilation and fans and better simulations of performance for buildings in the hot and humid areas of China.

Material properties are crucial input parameters for the analysis of heat, air and moisture transfer phenomena in built environment. However, many round robin tests reveal that the measurements on material properties – especially hygric properties – have poor reproducibility. Thus the measurement and data analysis methods should be questioned, and the currently available databases for material properties are not perfectly reliable. In this paper we aim at analyzing the material errors, repeatability errors, between-lab errors and reproducibility errors involved in the determination of hygric properties of porous building materials. The same materials as those used in the EC HAMSTAD project – autoclaved aerated concrete, calcium silicate board and ceramic brick – are chosen as target materials in our tests to facilitate error analysis. Static gravimetric tests, cup tests, capillary absorption tests, vacuum saturation tests and pressure plate tests have been repeated three times under repeatability conditions. Then the experimental results are analyzed in combination with the EC HAMSTAD report to calculate various errors. Results show that different materials have different heterogeneity errors, which can hardly be avoided. Moreover, in general these tests have excellent repeatability, indicating that under proper control the tests themselves are trustworthy. However, the large between-lab errors and the subsequent poor reproducibility demonstrate that in different labs the experimental procedures, condition controls, as well as data processing methods can deviate significantly. As a result, stricter and more detailed instructions are needed to improve the reproducibility of the tests for determining the hygric properties of porous building materials.

An experimental study of human responses to step changes of temperature and humidity was carried out on people in hot-humid area of China. Thirty college students who were naturally acclimatized to local climate and well experienced with air-conditioned environments participated in the experiment. Their physiological and psychological responses were measured continuously under conditions of neutral-warm and neutral-cool. Psychological lead occurs in all conditions expressed as psychological responses reaching steady state in a much shorter time than physiological ones, and overshoot occurs under sudden heating and does not occur under sudden cooling. Validation test of the Two-Node model shows that the model overestimates the steady state skin temperature under conditions of 20, 23 and 29 °C, and underestimates the change rate of skin temperature at the initial time of step changes. Heat acclimatization is suggested to be taken into account while applying the Two-Node model in hot-humid area of China. Relationships between physiological and psychological responses under step changes of neutral-warm and neutral-cool are established, indicating that both skin temperature and its change rate over time have significant impacts on thermal sensation. The acceptable conditions for transitional spaces in hot-humid area of China are recommended as the upper limits of air temperature 29.2 °C at 50% RH and 28.0 °C at 70% RH for 90% percentage satisfied, and 31.0 °C at 50% RH and 29.5 °C at 70% RH for 73% percentage satisfied.

The sorption isotherm is one of the most important hygrothermal properties of porous building materials, and is usually determined by the static gravimetric test. Typically the static gravimetric test takes weeks or months to complete, thus various measures are adopted to improve the test efficiency. Unfortunately, not all these measures have been validated specifically. This paper aims at validating several widely accepted measures to speed up the static gravimetric test on autoclaved aerated concrete at 25 C. Experimental results show that oven drying at 70 C gives nearly identical dry mass as desiccant drying at room temperature does, but is much faster than the desiccant method and avoids potential risks at 105 C. Moreover, large and small samples provide almost the same equilibrium moisture content, while small samples shorten test time obviously. In addition, as long as one-way adsorption process is kept without reverse, the effect of intermediate relative humidity levels on the equilibrium moisture content is negligible, supporting the method of exposing different samples to different RH levels simultaneously. Last but not least, a new mathematical model is introduced to fit the sorption curves. It works better than the Oswin, Henderson, Caurie, GAB, Hansen and Peleg models do. publisher: Elsevier articletitle: Validating various measures to accelerate the static gravimetric sorption isotherm determination journaltitle: Building and Environment articlelink: http://dx.doi.org/10.1016/j.buildenv.2013.08.005 content_type: article copyright: Copyright © 2013 Elsevier Ltd. All rights reserved. ispartof: Building and Environment vol:69 pages:64-71 status: published

This study examined the effects of personally controlled air movement on human thermal comfort and perceived air quality (PAQ) in warm-humid environments. At temperatures 26, 28, and 30 °C, and relative humidity (RH) 60% and 80%, sixteen human subjects were exposed to personally controlled air movement provided by floor fans in an environmental chamber. The subjects reported their thermal sensation, thermal comfort, and PAQ during the tests. Two breaks periods with elevated metabolic levels were used to simulate normal office activities. Results show that with personally controlled air movement, thermal comfort could be maintained up to 30 °C and 60% RH, and acceptable PAQ could be maintained up to 30 °C 80% RH, without discomfort from humidity, air movement or eye-dryness. Thermal comfort and PAQ were resumed within 5 min after the breaks. The 80% acceptable limit implicit in comfort standards could be extended to 30 °C and 60% RH. The average energy consumed by the fans for maintaining comfort was lower than 10 W per person, making air movement a very energy-efficient way to deliver comfort in warm-humid environments.

The effects of air movement from ceiling fans on subjective thermal comfort and perceived air quality (PAQ) were examined for warm-humid environments. In a climate chamber controlled at three temperatures (26 °C, 28 °C and 30 °C) and two relative humidity (RH 60% and 80%), sixteen subjects (8 males and 8 females) dressed in summer clothing (0.5 clo) were exposed to 7 levels of air speed ranging from 0.05 m/s to 1.8 m/s. The subjects were asked to rate their thermal sensation, comfort, PAQ, air movement acceptability, humidity sensation, eye-dryness during the 2-h and 15 min long tests. Air movement significantly improves the subjects' thermal comfort, PAQ, and humidity sensation without causing dry-eye discomfort. Without air movement, the 80% acceptable limit established by the ASHRAE standard 55 was reached at 26 °C/60%RH, 26 °C/80%RH, and 28 °C/60%RH. With air movement, more than 80% of the subjects perceived the environments acceptable at 28 °C/80%RH, 30 °C/60%RH, and 30 °C/80%RH. The preferred air speeds for ceiling fans were in many cases higher than the limit specified in ASHRAE Standard, which is 0.8 m/s when users have no control over the fan.

a b s t r a c t The microclimate around a building, establishing through the interaction with other buildings or the natural environment, is a significant factor in the building energy consumption. This paper presents a method for the quantitative analysis of building energy performance under any given urban contexts by linking the microclimate model ENVI-met to the building energy simulation (BES) program EnergyPlus. The full microclimatic factors such as solar radiation, long wave radiation, air temperature, air humidity, and wind speed have been considered in the proposed scheme. A case study has been conducted to analyze the effects of different microclimatic factors on the energy balance of an individual building. The method outlined in this paper could be useful for urban planning and building design.

Ventilation cooling technology (VCT) has been widely used for the notable energy saving, low first costs and conveniences for application in China in recent years. A new control strategy of VCT was provided to guarantee the indoor air temperature and humidity environment and maximize the energy saving. A simulation evaluation method for the energy saving of VCT which can be used for the different types of telecommunication base stations (TBS) under different meteorological conditions was proposed. The relations between each influencing factor and the annual saved energy were analyzed. And the application strategy of VCT was concluded as follows: the higher internal heat and the lower energy efficiency ratio of air conditionings, the more obvious energy savings would be achieved. VCT is not applicable when the internal heat is lower than a certain value and is more applicable in the hotter regions. The high temperature set point of air conditionings should be raised and the fan power should be reduced. The air change rate should be decided with the internal heat. The lowest internal heat of TBS for applying VCT and the highest annual saved energy of VCT for all types of TBSs was also provided.

Presently, there have been few studies on the outdoor thermal environment and thermal comfort of campus clusters in subtropical climate urban areas. In this study, first we investigated the influence of various types of design elements on the outdoor thermal environment around campus clusters in subtropical urban areas, such as pilotis, squares, and teaching building blocks. Second, we conducted a questionnaire survey on thermal sensation and thermal comfort in campus clusters to study the subjective response of young students to the outdoor thermal environment in subtropical urban areas. Assessment of thermal comfort by the SET∗ index suggests that the neutral SET∗ of young students is about 24 °C in an outdoor environment in subtropical urban areas in the summer. A 0.9 K temperature difference is observed between teaching building blocks and a grass-covered surface square, indicating the influence of the sky view factor (SVF) and heat capability of ground surface on air temperature distribution at night-time. Owing to a large SVF, more short-wave and long-wave reflections and long-wave radiations are incident on the square: attention should be paid to this fact, which may create an extremely hot outdoor thermal environment in the daytime. Influenced by MRT, the SET∗ around teaching building blocks is higher than those of the square and pilotis in the afternoon, which is expected to reduce the acceptable rate of the outdoor thermal environment. Pilotis can reduce SET∗ by 6–10 °C; therefore, the use of pilotis is encouraged to create an outdoor thermal environment of well-being in subtropical cities.

Polyvinylchloride (PVC) panel is one of the most favorite decorative materials that has been popularly applied as finishing of ceiling in residential buildings. It is about five years that the people incline to redecorate the ceiling of old buildings with PVC panel in big cities of Iran, such as Mashad. In this study, the influence of ceiling PVC panel on the cooling and heating loads of studied apartment were determined by software DeST-h. In addition, the summer natural ventilation of the mentioned apartment is investigated by determining the wind speed into the apartment through the computational fluid dynamics (CFD) software. The evaluation of environment indoor wind velocity showed that most of the apartment space is a comfortable zone. The results of studied building analyses demonstrated that using PVC panel on the ceiling can decline the energy consumption of the penthouse (fifth level) of the investigated building, which is about 3.7% and 7% for studied methods of without and with air layer, respectively. In addition, although the existence of air layer can decline the cooling and heating loads, the increase in air layer thickness did not show significant decrease on building energy consumption. However, the PVC panel is expensive and is not suitable to be used for ceiling thermal insulation, but adding a thin layer of air between ceiling and PVC panel can be a good step toward sustainable building, when the people are inclined to utilize it as a decorative ceiling.

Human responses to thermal environments in naturally ventilated (NV) buildings in hot-humid area of China were systematically investigated in the present study. Thirty local inhabitants long-time living in NV buildings participated in the study and reported their thermal sensations and perceptions and adaptive behaviors while all physical and personal variables were collected. Based on a year-long survey, a close match of indoor physical variables and occupants’ clothing insulation with outdoor climate was found as an important feature of NV buildings. Integrated indices can capture more thermal contexts in the NV buildings in hot-humid area of China than simple indices. Thermal sensation was found to be a good linear function of SET* with the thermal neutrality of 25.4 °C and the 90% (80%) acceptable range of 23.5–27.4 °C (22.1–28.7 °C) in SET*. The adaptive evidences were obtained for clothing adjustment, window opening and using fan respectively and the modified PMV model was validated to be applicable in NV buildings in hot-humid area of China with an expectancy factor of 0.822. Comparisons with other field studies indicate that people can develop various human-environment relationships through thermal adaptation to local climate, resulting in different thermal neutral temperatures in various climates. The subjects in hot-humid area of China are more acclimated and tolerable with hot and humid environments and more uncomfortable and intolerable with cold environments while compared with those in temperate climates.

This paper analyzed the energy balance of extensive green roofs and presented a simple but practical energy balance model. Field experiment justified the validation and accuracy of this model. Experimental results demonstrated that within 24 h of a typical summer day, when soil was rich in water content, solar radiation accounted for 99.1% of the total heat gain of a Sedum lineare green roof while convection made up 0.9%. Of all dissipated heat 58.4% was by the evapotranspiration of the plants–soil system, 30.9% by the net long-wave radiative exchange between the canopy and the atmosphere, and 9.5% by the net photosynthesis of plants. Only 1.2% was stored by plants and soil, or transferred into the room beneath.

Taking a certain housing in Guangzhou as an example, we conduct the field measurement of the microclimate at fixed points for air temperature, relative humidity, black globe temperature and wind speed, etc. We investigate the effects of manmade lake, shade of trees and ground surface character on outdoor thermal environment, and make a quantitative analysis on the weighting position of the landscape design factors in design behavior. The study intends to explore a method to improve the thermal environment of residential quarters by changing the corresponding factors.

Telecommunication base stations (TBSs) in Guangzhou, China are used in large numbers, and have high heat density, a long cooling season and high energy consumption. To make full use of natural outdoor cooling resources, a new ventilation cooling technology (VCT) is proposed. As the heat from the telecommunication equipment can be dissipated directly by outdoor cold air, the runtime of the air conditioners can be shortened by VCT, resulting in notable energy savings. Based on field investigation of a typical TBS, VCT was studied systematically. The results show that the application of VCT to the TBSs in Guangzhou is feasible, the energy saving for VCT is about 49% and the payoff period is less than two years. Obvious economic and social benefits will be achieved, provided that VCT can be broadly applied. Also, computational fluid dynamics simulation results indicate that optimization of airflow organization has a strong influence on heat dissipation efficiency for VCT.

This study used the computational fluid dynamics (CFD) method to evaluate the indoor thermal environment of an air-conditioned train station building under three types of air-conditioning design schemes. The impacts of air-conditioning design parameters such as supply air temperature, velocity, altitude and angle of incidence were also investigated. The numerical results showed that if the waiting hall and entrance hall of the train station building were connected to each other and served with the cooling air respectively, when the cooling loads in the two halls were fixed and air-conditioning systems were designed properly, altering largely the cooling air supply scheme in the waiting hall while keeping the cooling air supply scheme in the entrance hall unchanged would have significant effects on the air distribution and thermal comfort in the occupied region of the waiting hall but may have some minor effects on those in the occupied region of the entrance hall. The uniformities of velocity and temperature distributions in the occupied region of waiting hall were satisfactory when side supply scheme was applied. Changing supply air temperature, velocity, altitude and angle of incidence would yield great effects on the thermal environment in the train station building. For the stratified air-conditioning design in the train station building, in order to obtain the satisfactory thermal comfort in the occupied region, the mid-height of the building was found to be a good position for the cooling air supply and the supply angle of 0° from the horizontal could be recommendable. The results also indicated that analyzing the effects of air-conditioning design parameters on the building environment with CFD was an effective method to find the way to optimize the air-conditioning design scheme.

This paper studies the summer natural wind environments inside an airport terminal building under two cases by the method of computational fluid dynamics (CFD). The two cases have different opening...

Solar penetration through the transparent envelope can severely deteriorate indoor thermal environment inside an atrium building particularly in tropical climates. This paper reports the application of two low-cost measures, namely high level internal solar blinds and water spray, to minimise overheating problems on the three levels inside the atrium of a guesthouse in Southern China, where summer is hot and humid. The blinds reduce direct solar penetration at the top of the atrium whilst the evaporative spray system cools down the glazed surfaces of the atrium envelope. A site test was undertaken over 10 consecutive days covering both overcast days and clear days in July 2004. Measurement of indoor thermal environmental parameters was conducted on three levels in the atrium and the recorded data represent the internal conditions: with and without internal blinds protection from solar, and with and without water spray. This study has shown that on hot and clear summer days, with water spray and without blinds the average air temperature difference from 1200 to 1800 h between both first floor and second floor, and second floor and external were 5.7 and 1.7 K, respectively; whilst with blinds and without water spray the average air temperature differences were 8.7 and 4.8 K, respectively.

Telecommunication base station (TBS) buildings have large numbers, high energy consumptions and great potentials on energy conservation. Through field investigation of a typical TBS in Guangzhou, the basic information of TBS was achieved, the key factors influencing energy consumption of TBS were determined and several energy efficient envelope designs were proposed. The effect on annual cooling load was analyzed for each energy efficient design and the combined effects were achieved for several combinations of the designs by thermal simulation. The energy efficient design strategy of building envelope for TBS in Guangzhou was proposed.

In uncomfortably warm areas and seasons of the year, passive cooling effects resulting from natural rainfall evaporation can greatly cut down on building energy consumption. To simulate the passive evaporation cooling effect and evaluate the relevant energy-saving potentials, hourly rainfall data are needed. However, in currently used building energy simulation software, such as DOE, EnergyPlus and DeST, no rainfall information is provided in the climatic database. This paper uses a limited set of monthly and daily rainfall distribution data in Guangzhou area to identify and model monthly, daily and hourly rainfall patterns. For a current weather database used by building energy simulation software, rainy days and rainy hours are distinguished using distance discriminant analysis, which uses measured data samples for rain identification. According to an autocorrelation analysis of rain sequences, a one-order AR model is suitable for monthly rainfall estimation by AIC criterion judgment. Distribution of daily rainfall month-by-month shows a Gamma distribution model agrees well with daily rainfall distribution. Using a Gamma distribution model and monthly total rainfall, daily rainfall is assigned stochastically. Analysis shows distribution patterns of hourly rainfall percentage, both in the rainy season and non-rainy season, coincide well with the Beta distribution. Using a Beta distribution model and daily total rainfall, hourly rainfall is assigned stochastically. A comparison of statistics features of simulated data to that of measured data validates the method.

Rooftop shading is an effective green building design strategy in subtropical areas; it can create an ecological rooftop space and produce energy savings for rooms on the top floor. This article describes the rooftop shading system of the Humanities Building at SCUT (South China University of Technology). A shading calculation software developed by the Building Energy Efficiency Laboratory (BEEL) of SCUT is used to calculate and analyze the rooftop shading effect in summer and winter. The actual performance of this rooftop shading system was evaluated by measuring the wet bulb globe temperature (WBGT) in the shaded and unshaded areas under the shading system on July 2, 2003.

A method of laying a layer of humid porous medium on roof to gain free cooling effect by passive water evaporation is proposed. Numeric model for simulating cooling effect is built with the help of experimental results of physical properties for humid porous medium, which shows advantage over analytical solutions because of the supposition of constant physical properties in the latter. Through the comparison between simulated and experimental results, the model is validated. And the method of evaporation cooling effect with humid porous medium on the roof is tested to be feasible.

Joule heating of NiTi shape memory alloy wires is a commonly applied technique for heat treatment and shape setting in many applications. Another innovative use of this method is to produce functionally graded NiTi. In this study, NiTi wires with spatially varied shape memory characteristics along the length were created by electrical resistance over-aging of a Ni-rich superelastic NiTi alloy. The stress–strain behaviour of such wires exhibited some new and unique characteristics during the stress-induced martensitic transformation, including two discrete stress plateaus, stress serration during transition between the two stress plateaus and an arch-shaped stress plateau in the over-aged section. These unique features have direct implications to design using NiTi alloys and the underlying mechanisms are explained in this study.