Description of small and large-scale cross laminated timber fire tests

A large-scale fire test was conducted on a compartment constructed from cross laminated timber (CLT). The internal faces of the compartment were lined with non-combustible board, with the exception of one wall and the ceiling where the CLT was exposed directly to the fire inside the compartment. Extinction of the fire occurred without intervention. During the fire test, measurements were made of incident radiant heat flux, gas phase temperature, and in-depth temperature in the CLT. In addition, gas flow velocities and gas phase temperatures at the opening were measured, as well as incident heat fluxes at the facade due to flames and the plume leaving the opening. The fuel load was chosen to be sufficient to attain flashover, to achieve steady-state burning conditions of the exposed CLT, but to minimize the probability of uncertain behaviors induced by the specific characteristics of the CLT. Ventilation conditions were chosen to approximate maximum temperatures within a compartment. Wood cribs were used as fuel and, following decay of the cribs, self-extinction of the exposed CLT rapidly occurred. In parallel with the large-scale test, a small scale study focusing on CLT self-extinction was conducted. This study was used to establish: the range of incident heat fluxes for which self-extinction of the CLT can occur; the duration of exposure after which steady-state burning occurred; and the duration of exposure at which debonding of the CLT could occur. The large-scale test is described, and the results from both the small and large-scale tests are compared. It is found that self-extinction occurred in the large-scale compartment within the range of critical heat fluxes obtained from the small scale tests.     

Thermal comfort of people in the hot and humid area of China—impacts of season,climate, and thermal history

We conducted a climate chamber study on the thermal comfort of people in the hot and humid area of China. Sixty subjects from naturally ventilated buildings and buildings with split air conditioners participated in the study, and identical experiments were conducted in a climate chamber in both summer and winter. Psychological and physiological responses were observed over a wide range of conditions, and the impacts of season, climate, and thermal history on human thermal comfort were analyzed. Seasonal and climatic heat acclimatization was confirmed, but they were found to have no significant impacts on human thermal sensation and comfort. The outdoor thermal history was much less important than the indoor thermal history in regard to human thermal sensation, and the indoor thermal history in all seasons of a year played a key role in shaping the subjects' sensations in a wide range of thermal conditions. A warmer indoor thermal history in warm seasons produced a higher neutral temperature, a lower thermal sensitivity, and lower thermal sensations in warm conditions. The comfort and acceptable conditions were identified for people in the hot and humid area of China.     

Fire thermal boundary condition measurement using a hybrid heat flux gage

New experimental methods have been developed using a hybrid heat flux gage to quantify the thermal boundary condition to a surface exposed to fire. The hybrid heat flux gage is capable of measuring the net heat flux and exposure heat flux at gage temperatures up to 1000 °C without the need for water cooling. Using these heat fluxes at elevated surface temperatures, new methods were developed to quantify the convective heat transfer coefficient and adiabatic surface temperature. In addition, a procedure is presented for determining the convective and radiative heat flux components when the gas temperature is measured close to the gage surface. Techniques were validated in a series of experiments performed in a cone calorimeter at different heat fluxes. Cold surface heat fluxes from the hybrid heat flux gage were within 5% of heat fluxes measured using a water-cooled Schmidt-Boelter gage. Temporal adiabatic surface temperature measurements from the hybrid gage compared well with steady-state plate thermometer measurements.     

A comparison of the thermal adaptability of people accustomed to air-conditioned environments and naturally ventilated environments

It has been reported previously that people who are acclimated to naturally ventilated (NV) environments respond to hot and warm environments differently than people who are acclimated to air-conditioned (AC) environments. However, it is not clear whether physiological acclimatization contributes to this discrepancy. To study whether living and working in NV or AC environments for long periods of time can lead to different types of physiological acclimatization, and whether physiological acclimatization has an important influence on people's responses of thermal comfort, measurements of physiological reactions (including skin temperature, sweat rate, heart rate variability, and heat stress protein 70) and thermal comfort responses were conducted in a 'heat shock' environment (climate chamber) with 20 people (10 in the NV group and 10 in the AC group). The results showed that the NV group had a significantly stronger capacity for physiological regulation to the heat shock than the AC group. In other words, the NV group did not feel as hot and uncomfortable as the AC group did. These results strongly indicate that living and working in indoor thermal environments for long periods of time affects people's physiological acclimatization. Also, it appears that long-term exposure to stable AC environments may weaken people's thermal adaptability. PRACTICAL IMPLICATIONS: This study examined the psychological and physiological differences of thermal adaptability of people used to air-conditioned environments and naturally ventilated environments. The results suggested that long-term exposure to stable air-conditioned environments may weaken people's thermal adaptability. Therefore, it might be advantageous for people to spend less time in static air-conditioned environments; this is not only because of its possible deleterious impact on people's physiological adaptability, but also because the air-conditioners' high-energy consumption will contribute to the effects of global warming.     

A new environmental heat stress index for indoor hot and humid environments based on Cox regression

Physical work in hot and humid environments imposes health risks, productivity falling and safety problems on workers. Protection of workers from heat related problems requires quantitative heat stress assessment of the workplace. In this paper, a new index-equivalent temperature (ET) is proposed to measure the environmental heat stress in indoor hot and humid environments. A climate chamber was built to simulate the indoor hot and humid environment. And the safe working time of 144 male volunteers were studied under different climatic conditions in the chamber. Cox regression method is adopted to obtain the impacts of variables on the safe working time. Then the new index-ET is proposed based on the Cox regression results. The correlations between the ET and the common used indexes are determined to test the validity of this new index. Finally the safe working time concerned with the ET is summarized. The results show that the new index gives physiological correlates and physical means. The ET developed in this paper has the potential to be a practical index to measure the environmental heat stress in indoor hot and humid environments.     

A study of coupled heat and mass transfer across a porous building component in intertropical conditions

In this paper, one-dimensional coupled heat and mass transfer through a plane geometry porous building component submitted to intertropical climatic conditions is studied. An analytical method using the periodic solution approach has been proposed to evaluate the heat and moisture transfer process in building materials. Results are discussed using the three climatic regions of Cameroon (2-13 °N). With latitude of 11°, it offers examples of practically whole range of intertropical climates. Influence of latitude on various temperature and moisture content through the building component has been presented. The results are in good agreement with the experimental data and other analytical solutions published in the literature.     

Productivity and physiological responses during exposure to varying air temperatures and clothing conditions

This study assessed the effects of clothing and air temperature combinations on workplace productivity and physiological response. Ten male Japanese subjects were exposed to six combinations of clothing (0.3 clo and 0.9 clo) and air temperature (16°C, 26°C, and 36°C) during which cognitive performance (Bourdon and calculation tests), manual motor performance (finger-tapping test), and physiological responses (heart rate, blood pressure, and skin and oral temperatures) were measured. Both cold exposure and lower clothing levels likely increased the Bourdon test performance. Calculation test performance tended to be affected by exposure to cold or neutral temperatures at the beginning of the test. Cold exposure undermined manual motor performance (especially when combined with fewer clothing items) while heat exposure significantly increased heart rate. Both cold exposure and higher clothing level during heat exposure increased blood pressure. Body temperature, particularly mean skin temperature, increased with higher air temperature and was significantly influenced by clothing insulation during cold exposure. These results provide novel evidence for the effects of clothing and air temperature (particularly cold) on human productivity and physiological responses in humans.     

The impact of heat and water stress conditions on the growth of the biofuel plant Jatropha curcas

Pot experiments were carried out to evaluate the effects of drought and salinity stresses and mulch amendment on Jatropha in sand dune soil under three conditions: glasshouse, shade house and open area. Plants were irrigated with freshwater and diluted seawater adjusted to two levels of electrical conductivity- 3 and 6 dS m^-1. The results showed that experimental conditions remarkably affected the evapo-transpiration rate, soil moisture, salts accumulation and plant biomass production. Low temperature (23°C) conditions exhibited highest plant growth and soil moisture and lowest salts deposition. Plants showed no symptoms of heat stress in the glasshouse. The shade house and the open area profoundly reduced plant biomass and water content in the soil. Compared to the control, the mulch amended treatments had sufficient water for plant growth even in the high temperature of the open area. High salt content was found in salinity treated pots but the salinity level did not reduce Jatropha growth. Salt accumulated in the salinity treated pots helped retain more water, reduced the temperature and provided nutrients to the plants, with results which were almost similar to those from the mulch effect. The temperature conditions of the shade house and the open area (max>40°C) caused substantial water loss and induced death of plants. Jatropha is a succulent and drought tolerant plant and a close irrigation interval is not the best option for Jatropha growth. But, organic amendment is needed when there is a big loss of soil water due to heat stress condition.     

Effects of steady-state noise and temperature conditions on environmental perception and acceptability

The combined effects of noise and temperature on environmental perception and acceptability were studied on 18 lightly clothed subjects (0.6 clo), individually exposed for 2 h in a climatic chamber. Three homogeneous climatic conditions were chosen (air temperature at 18, 24 or 30 degrees C, air velocity =0.1 m/s). For each of them, three different noise levels were continuously maintained (35, 60, 75 dBA, recorded fan noise). The 18 subjects were divided into three groups and each group experienced only one single thermal condition, at each level of noise, during three different experimental sessions. Subjective answers about perception and comfort were obtained at t = 30 and 120 min. Main results indicate that acoustic perception decreases when thermal environment is far from thermoneutrality. Although the combined effects of noise and temperature did not influence the physiological data, our results show that whatever the ambient temperature, thermal unpleasantness is higher when noise level increases. Finally, equivalence between acoustic and thermal sensations is proposed for short-term exposure (1 degree C = 2.6 dBA) and for steady state (1 degrees C = 2.9 dBA). In conclusion, this study strongly suggests that interactions between environmental components do exist, right from perceptual level, and might explain some combined effects on cognitive performance.     

Ignition of wood under time-varying radiant exposures

Many studies have utilized a small-scale experimental apparatus such as the cone calorimeter to investigate the piloted ignition of wood exposed to constant levels of incident heat flux; however, there is a deficiency of similar studies related to the non-piloted ignition of wood exposed to time-varying heat fluxes which might represent more realistic fire exposures. In this study, a method was established for producing well-controlled, time-varying exposures using the conical radiant heater of a cone calorimeter. Experiments were conducted in which the incident flux, time to non-piloted ignition, and back-surface temperature of spruce wood were measured. Measured data were used in combination with a numerical heat transfer model to compute the time-dependent temperature distribution through each specimen, and thereby deduce the surface temperature at ignition. From the 30 specimens tested, the average surface temperature for non-piloted ignition of wood was determined to be 521±10 °C. From this surface temperature range, the heat transfer model was used to predict the range of time over which non-piloted ignition was likely to occur for a given time-varying exposure. This procedure was found to produce excellent predictions of ignition time for the time-varying exposures considered in this study. In addition, several existing ignition models were considered, and their suitability for predicting the non-piloted ignition of wood was assessed.     

制冷工况下水平埋管换热器运行试验研究

通过夏季工况的地源热泵运行试验,对运行过程中水平埋管的换热性能参数、试验场地周围气象因素和换热过程中土体的温湿度变化等因素进行实时监测,探讨了地源热泵运行过程中水平埋管换热器热交换性能及其周围土壤的温、湿度场变化规律。研究结果表明,地源热泵间隙运行有利于土壤温度场的恢复,随着停机时间的增加,水平埋管与周围土壤的热交换能力明显提高;气候变化对水平埋管周围土壤的温度场分布具有显著影响,随着埋深的递减,土壤温度受气候变化的影响越明显;水平埋管周围土壤温度的变化幅度随着与埋管距离的增加呈递减趋势,其影响半径为1.0m左右;热交换对水平埋管周围土壤湿度场的影响不明显,但大气降雨引起的地表水入渗对土壤湿度场的分布具有显著影响。     

人工气候环境下考虑荷载应力影响的混凝土温度响应研究

通过自制的持续加载装置对混凝土试件施加不同水平的拉应力或压应力,并在恒温恒湿箱模拟的人工气候条件下进行混凝土试件的升温试验,研究不同应力水平对混凝土微环境温度响应的影响;通过对试验结果的分析,并结合混凝土传热学的相关理论,计算出不同应力水平下混凝土的导热系数,进而建立考虑荷载应力影响的混凝土导热系数预测模型。结果表明:在恒定的人工气候条件下,混凝土的压应力水平越高,其温度响应速率越快,而拉应力水平越高,其温度响应速率越慢;对于同样的应力水平,压应力对混凝土温度响应的影响更显著;所得研究成果可以为实际工程结构中混凝土内部温度响应的预测奠定一定的理论基础。     

Evaluating thermal comfort conditions and health responses during an extremely hot summer in Athens

In summer 2007, in the city of Athens, Greece, extremely high air temperatures were recorded, inducing heat discomfort conditions in the urban environment. Four biometeorological indices were calculated in order to evaluate human thermal sensation and thermal comfort: Actual Sensation Vote (ASV), Thermal Sensation-Ginovi method (TS), Discomfort Index (DI) and Heat Load Index (HL). Data included measurements of ambient temperature, temperature of the surrounding ground surface, relative humidity, air pressure, wind velocity and solar radiation obtained from National Observatory of Athens (NOA) station. During this period the daily number of patients probably affected by heat in emergency department units of cardiac clinics of four public general hospitals in Athens was recorded. The results revealed high values of DI and HL indices, demonstrating severe heat stress conditions during the last ten day period of June and July, while the ASV tends to classify too many cases into the comfort zone compared to TS, DI and HL. The statistical analysis revealed a negative relationship between the number of heat affected patients and the estimated indices values.     

Measuring the human body's microclimate using a thermal manikin

The human body is surrounded by a microclimate, which results from its convective release of heat. In this study, the air temperature and flow velocity of this microclimate were measured in a climate chamber at various room temperatures, using a thermal manikin simulating the heat release of the human being. Different techniques (Particle Streak Tracking, thermography, anemometry, and thermistors) were used for measurement and visualization. The manikin surface temperature was adjusted to the particular indoor climate based on simulations with a thermoregulation model (UCBerkeley Thermal Comfort Model). We found that generally, the microclimate is thinner at the lower part of the torso, but expands going up. At the head, there is a relatively thick thermal layer, which results in an ascending plume above the head. However, the microclimate shape strongly depends not only on the body segment, but also on boundary conditions: The higher the temperature difference between the surface temperature of the manikin and the air temperature, the faster the airflow in the microclimate. Finally, convective heat transfer coefficients strongly increase with falling room temperature, while radiative heat transfer coefficients decrease. The type of body segment strongly influences the convective heat transfer coefficient, while only minimally influencing the radiative heat transfer coefficient.     

Physiological and psychological reactions of sub‐tropically acclimatized subjects exposed to different indoor temperatures at a relative humidity of 70%

Thermal comfort, self‐reported acute health symptoms, cognitive performance, and physiological reactions were examined at four temperatures (26, 30, 33, and 37°C) at a relative humidity of 70%. Thirty‐two sub‐tropically acclimatized subjects experienced each condition for 175 minute, in balanced order, in a climatic chamber. The perception of heat gradually increased with increasing temperature, but the subjects felt hot only at 37°C. The temperature of 33°C was on average rated as acceptable and only just uncomfortable. The acceptability of air quality decreased linearly with increasing temperature. The intensity of acute health symptoms reported by the subjects increased with increasing temperature, but it was no more than moderate even at the highest temperature; dryness of skin and eye were alleviated. The eardrum temperature, skin temperature and moisture, heart rate, end‐tidal carbon dioxide, and weight loss increased significantly with increasing temperature, whereas the percentage of adjacent heart inter‐beat intervals differing by >50 ms decreased significantly. These results suggest that the perceived heat, self‐reported symptoms, and physiological reactions occurred concurrently. They show additionally that acclimatization to heat may shift the boundary of thermal discomfort to a higher temperature. The role of psychological adaptation and of the contextual aspects of this process still requires clarification in future experiments.     

Modeling thermal response of steel–concrete floor systems in a furnace

A methodology was developed to predict the thermal exposure from a furnace onto a floor assembly specimen. In furnaces with low conductivity wall linings and gas fired burners with complete combustion, the gas attenuation effects were determined to be small indicating that radiation between surfaces and convection are the dominant modes of heat transfer. This was modeled by assigning the internal furnace wall temperature to the furnace time–temperature exposure and performing a three-dimensional heat transfer analysis on the specimen. The furnace exposure model predicted heat transfer to the specimen surface that was within 5–14% of measured heat fluxes. The proposed furnace exposure methodology was used to predict the temperature rise of steel in a floor assembly where the test specimen can view itself as well as the furnace, making radiation exchange an important aspect of the problem. Predictions were within 5–10% of the measured values, which was within the experimental uncertainty.     

Climatic zoning for energy efficiency applications in buildings based on multivariate statistics: The case of the Brazilian semiarid region

This study aimed to propose climatic zones in the Brazilian semiarid region using multivariate statistical techniques and to characterize these zones for energy efficiency applications in buildings. Principal component analysis (PCA) was used to select the variables with the greatest practical relevance. From this selection, hierarchical cluster analysis (HCA) was used to spatially define climatically homogeneous zones. For each defined zone, the most feasible constructive thermal conditioning strategies were defined, and the thermal indexes of heat and degree-hours of cooling and heating were calculated. As result, PCA reduced the dimensionality of the initial database from 104 to 48 variables, among which the climatic and bioclimatic variables related to temperature stood out. From the HCA, three climatic zones were defined for the Brazilian semiarid region. For all zones, there was a high demand for constructive conditioning strategies, which have to be adopted in more than half of the total annual hours. The proposed zoning is adapted to the climatic aspects of the Brazilian semiarid and has significant potential for applications in construction planning in this region. Moreover, the methodology presented can be applied for establishing climatic zones in other regions, which can contribute to increasing the energy efficiency of buildings.     

Thermal comfort, skin temperature distribution, and sensible heat loss distribution in the sitting posture in various asymmetric radiant fields

This study aimed at investigating the thermal comfort for the whole body as well as for certain local areas, skin temperatures, and sensible heat losses in various asymmetric radiant fields. Human subject experiments were conducted to assess the overall comfort sensation and local discomfort, and local skin temperatures were measured. Through thermal manikin experiments, we discovered a new method for the precise measurement of the local sensible heat loss in nonuniform thermal environments. The local sensible heat losses were measured by the use of a thermal manikin that had the same local skin temperatures as the human subjects. The experimental conditions consisted of the anterior–posterior, right–left, and up–down asymmetric thermal environments created by radiation panels. A total of 35 thermal environmental conditions were created ranging from 25.5 to 30.5 °C for air temperature, from 11.5 to 44.5 °C for surface temperature of radiation panels, from 40% RH to 50% RH for humidity, and less than 0.05 m/s for inlet air velocity to the climatic chamber. The local skin temperature changed depending on the environmental thermal nonuniformity, even if the mean skin temperature remained almost the same. It is essential to use the skin temperature distribution as well as mean skin temperature for expressing thermal comfort in nonuniform environments. The local sensible heat loss changed depending on the environmental thermal nonuniformity, even if the mean sensible heat loss remained almost the same. The relationship between the local skin temperature and local sensible heat loss cannot be depicted by a simple line; instead, it varies depending on the environmental thermal nonuniformity. The local heat discomfort in the head area was dependent on both the local skin temperature and local sensible heat loss. However, the local cold discomfort in the foot area was related only to the local skin temperature.     

Seasonal effect of pavement on outdoor thermal environments in subtropical Taiwan

This study investigated how pavement affects outdoor thermal environment during summer and winter in subtropical Taiwan. The experiment was carried out on five pavements in three areas of Taiwan. The results demonstrated no significant differences in average air temperature among several pavements except at noon time during the summer. The surface temperatures of the artificial pavements were 10 °C higher than those of the vegetation surface at noon during the summer. Of all the factors measured in this investigation, surface temperature was most closely correlated with air temperature. The calculated heat output reveals that heat conduction strongly influenced total heat output. The value of heat output was primarily determined by the proportion of heat conduction in heat absorption. The heat output also significantly affected the air temperature and mean radiant temperature.     

太阳能热泵区域性设计

通过分析不同地区的太阳能资源季节分布以及室外气温等气候参数之间的对应关系,将气候分区的概念引入太阳能热泵系统设计中。根据全国各地的气候特点,将全国划分为4个不同的区域,提出可使用4种不同类型的热泵系统,并分别给出其适用区域。提出一种储热型多功能太阳能热泵系统作为例子,分析其在不同条件下的运行模式,结果表明其可适用于不同地区和季节及用户的需要。