Air-conditioned Room Research Articles

Neonatal Oxidative Stress Impairs Cortical Synapse Formation and GABA Homeostasis in Parvalbumin-Expressing Interneurons.

Neonatal brain injury is often caused by preterm birth. Brain development is vulnerable to increased environmental stress, including oxidative stress challenges. Due to a premature change of the fetal living environment from low oxygen in utero into postnatal high-oxygen room air conditions ex utero, the immature preterm brain is exposed to a relative hyperoxia, which can induce oxidative stress and impair neuronal cell development. To simulate the drastic increase of oxygen exposure in the immature brain, 5-day-old C57BL/6 mice were exposed to hyperoxia (80% oxygen) for 48 hours or kept in room air (normoxia, 21% oxygen) and mice were analyzed for maturational alterations of cortical GABAergic interneurons. As a result, oxidative stress was indicated by elevated tyrosine nitration of proteins. We found perturbation of perineuronal net formation in line with decreased density of parvalbumin-expressing (PVALB) cortical interneurons in hyperoxic mice. Moreover, maturational deficits of cortical PVALB+ interneurons were obtained by decreased glutamate decarboxylase 67 (GAD67) protein expression in Western blot analysis and lower gamma-aminobutyric acid (GABA) fluorescence intensity in immunostaining. Hyperoxia-induced oxidative stress affected cortical synaptogenesis by decreasing synapsin 1, synapsin 2, and synaptophysin expression. Developmental delay of synaptic marker expression was demonstrated together with decreased PI3K-signaling as a pathway being involved in synaptogenesis. These results elucidate that neonatal oxidative stress caused by increased oxygen exposure can lead to GABAergic interneuron damage which may serve as an explanation for the high incidence of psychiatric and behavioral alterations found in preterm infants.

ECOFEMINISM OF FORESTRY CONSERVATION IN RIAU

In the last 18 years, Riau Province, especially Pekanbaru and its surroundings, has often been surrounded by smoke from forest fires. Based on National Board and Disaster Management, Riau is the province with the largest forest fires. There were 49,266 hectares of land burned with 90 hotspots detected until August 2019. The effect of it was the air pollution index in Pekanbaru and its surroundings has reached red degrees. This condition is very dangerous, especially for vulnerable groups such as women, pregnant women, elderly group and children. The central and local government have taken many actions every year, but still not sufficient to protect public health, especially vulnerable groups. So far, women and children have been forced to inhale the smoke intensively without any protective equipment (N95 masks) or proper shelters in case of forest fires. The children were forced not to go to school for weeks, because the classrooms were not equipped with air-conditioned rooms and air purifiers. Several studies have found that smoke-contaminated air, soil and food are very bad for health before and after birth. Toxic substances inhaled by pregnant women can interfere with their health and interfere with the nutrition and oxygen flow of the fetus. Another study also found that exposure to Indonesia’s forest fires in late 1997 caused more than 15,600 child, infant and fetal deaths, meaning children’s survival rates decreased by 1.2 percentage points due to exposure to toxic fumes. A child’s nutrition and health can be directly compromised after inhaling toxic fumes or ingesting them in contaminated raw food. In addition to health impacts, forest fires also have a major impact on the economic, social and environmental affairs of local communities. And the biggest group that bears the impact is again women. The Women Research Institute (2016) states that women as the person in charge of domestic affairs turned out to be the most real victims in the domino effect of these forest fires. To name a few examples, women have to take care of sick family members even though they themselves are in poor health conditions. Women who are pregnant and breastfeeding have to breathe toxic air which results in low nutrition delivered to their children. If the head of the family cannot actively work because of illness, then it is the woman who must be the backbone of the family. Because they are directly affected, women have also been shown to be actively involved in various efforts to extinguish forest fires. Starting from technical forest fires to informal advocacy against companies that have forest concession permits. However, in various decision-making forums between the government and companies related to forest concessions that involve elements of the community, women’s groups are often not involved, so women’s aspirations and interests are not taken into account. In fact, in forest management and utilization, men and women have different roles and knowledge, so that their involvement is very important to realize proper governance. This study intends to explore and identify the extent to which women and their groups are involved in forest and environmental conservation efforts in Riau. The information obtained later is expected to be able to explain how the cultural and social constructs of society in supporting the involvement of women in these efforts. Including how these cultural constructs ultimately influence the government’s decision to involve women’s groups.
 Keywords: Ecofeminism, Forestry, Conservation, Forest fires

Comparative analysis of the energy efficiency of air-conditioner and variable refrigerant flow systems in residential buildings in the Yangtze River region

Two types of air-conditioning systems, named as room air conditioners (RAC) and multi-connected air-conditioners (variable refrigerant flow (VRF) systems) have become popular heating and cooling facilities for residential buildings featured with ‘part-time-part-space’ operation characteristics in the Yangtze River region. However, the research on the energy efficiency of these two systems in residential buildings is currently lacking. Based on the actual measured air-conditioning operation hours and demand characteristics, this study analyzed the annual operation performance of the two systems by modelling and simulation. In addition, a field test of twelve RACs and five VRFs in residential buildings was conducted in the Yangtze River region, showing the annual performance factors of VRFs and RACs ranged from 3.7 to 5.3 kWh·kWh−1 and 3.0 to 4.6 kWh·kWh−1, respectively. It is found that for the same operation hours and the total cooling capacity of VRF systems RACs, the VRF has low energy efficiency at low load ratios (generally less than 25%); which is the key barrier to its application in residential buildings in the Yangtze River region. It is suggested the RAC is the appropriate solution for heating and cooling a residential building with a ‘part-time-part-space’ operation mode as it is more energy-efficient. New advanced technologies for VRF systems are expected to be developed in order to adapt the part-load operation mode to achieve high energy efficiency. This study contributes to providing evidence for the decision-making of RAC and VRF systems for policymakers, and building and engineering designers in the context of energy efficiency for the region.

Studi Bahan Kemasan terhadap Viabilitas Benih Kedelai (Glycine max [L.] Merril) Pascasimpan Dua Belas Bulan di Ruang Simpan Suhu Rendah

Soybean is a commodity that is a source of vegetable protein that is easily obtained at a low price. The factor that affects low soybean productivity in Indonesia is the lack of use of quality seeds by farmers. Efforts to maintain the shelf life of soybean seeds can be done by using good packaging materials. The purpose of this study was to determine the effect of packaging materials that have different characteristics under low temperature storage conditions on the viability of soybean seeds after twelve months of storage. This research was carried out at the Seed and Plant Breeding Laboratory, Faculty, Agriculture, University of Lampung from October 2019 to June 2020. The treatment design was a single and unstructured factor, namely packaging material (b). The treatment of packaging materials consisted of aluminum foil (b1), polyethylene (b2), polypropylene (b3), brown envelope paper (b4), ordinary plastic (b5), calico fabric (b6). The packaging materials for six treatments were arranged in a randomized block design (RAK) with four replications. The results of this study showed that the viability of seeds was high in aluminum foil, polyethylene, polypropylene, ordinary plastic, envelope paper, and calico packaging materials in low temperature storage in an air-conditioned storage room after twelve months of storage. Twelve months post-stored seed viability was indicated by the germination rate of 87.48%; maximum growth potential of 96.25%; germination speed 30.96%; strong normal sprouts 81.19%; hypocotyl length 11.99 cm; dry weight of normal sprouts 31.82 mg; water content 7.30%; and electrical conductivity of 244.96 S/cm. Key words: viability, soybean seed, storage, packaging material, low temperature

Energy conservation and climate change mitigation potential of improving efficiency of room air conditioners in Pakistan

The present study predicts the energy savings, carbon emissions reduction and economic benefits for Pakistan through energy efficiency improvements for room air conditioners under different policy scenarios. The simulation model assumes that room air conditioner stock will increase from 2.7 million for year 2020 to 4.9 million for year 2030. A market average energy efficiency ratio of 2.95 is assumed for year 2020. The impact of improvement in energy efficiency ratio is analyzed for business as usual and four other different scenarios: continuous improvement (5-years and 2-years cycles) and accelerated improvement (5-years and 2-years cycles). The model dynamically incorporates the retiring of old stock and addition of new stock every year. Our results show that annual national electricity consumption for this sector is projected to increase from 7.3 TWh in 2020 to 12.6 TWh in 2030 under the business as usual scenario. The cumulative energy consumption and carbon emissions are 103.5 TWh and 63.1 MtCO 2. However, implementing energy efficiency policies can result in electricity savings of 11.6 TWh over the ten years or savings nearly 7 million barrels of oil import. Policy recommendations aimed at promoting energy labeling, minimum energy performance standards, regulatory policies, and further country-specific studies for variety of appliances are provided.

Associating thermal comfort and preference in Malaysian universities’ air-conditioned office rooms under various set-point temperatures

Overcooling indoor spaces in hot-and-humid regions indicate excessive usage of air conditioner (AC). Understanding the occupants' thermal perception in AC settings helps navigate the cooling energy required. This study investigated thermal comfort in biased and non-biased environments and examined the occupants’ preferences. Four set-point temperature conditions (Original, Original ±2 °C, and MS Standard) were implemented in a semi-controlled field study done in 19 offices. 628 samples were taken from 42 occupants via thermal measurements and questionnaire surveys. The indoor air temperature in the typical AC settings (Original set-point) was 23.1 °C, denoting non-compliance to the local guideline. The results showed that occupants generally felt more comfortable when the indoor air temperature was increased. The mean comfort temperature was 24.6 °C, and the proportion of comfort votes depletes when the operative temperature reaches 26 °C. The preferred temperature was estimated at 23.9 °C, and the linear relationship with comfort temperatures revealed that occupants preferred a cooler environment despite being thermally comfortable. The findings suggest that occupants could tolerate higher AC settings well, but thermal preference may be a critical factor in estimating the comfort temperature limits.

“Other voices, other rooms:” notes on the production of Africanist scholarship in Africa and in the global north

Two starting points for the paper are a summary account of the accomplishments of Bernth Lindfors, whose career is seen as achieving a symbiosis between work on African literary scholarship done in the global north and in parts of Africa, and a paper by Carli Coetzee on journal work in African literary studies as, ideally, ethical labor. The title of the article by Coetzee referencing the “air-conditioned room” prompts the title of the present paper (with a nod to Truman Capote’s title, which I borrow) and provides the impetus for a consideration of the production of academic journals in Africa. African literary scholarship stands to gain from regional and continental exchanges and partnerships made on a more even footing than the conventional north-south divide currently allows for. Although not without controversy, Lindfors attempted to undo the material and other inequities implied in Coetzee’s title, to facilitate other voices, and provide wider access to multiple spaces of Anglophone African literature.

Role of central irisin in the cardiorespiratory and metabolic control of adult rats

Irisin has been identified as an important exercise‐induced myokine that acts in different physiological systems; however, little is known about the participation of irisin in cardiorespiratory and basal metabolic control. Therefore, the present study evaluated the effect of intracerebroventricular (icv) injection of vehicle or irisin (IR, 0.425 µg/µL) in the fourth ventricle (4V) of adult male rats on the cardiorespiratory and metabolic control during wakefulness and sleep under room air, hypercapnia (7% CO2) and hypoxia (10% O2). Our data show a tendency of reduction in basal ventilation of IR group during wakefulness (VEH: 1056.2 ± 61.8 vs IR: 816.9 ± 30.5 mL.Kg‐1.min‐1), due to a reduction in respiratory frequency (VEH: 105.1 ± 5.3 vs IR: 85.9 ± 5.1 breaths.min‐1) and a consequent decrease in arterial partial pressure of O2 (VEH: 95.1 ± 2.4 vs IR: 88.7 ± 3.1 mmHg). No difference was observed in metabolic rate; however, central IR promoted a reduction in the air convection requirement (VEH: 57.2 ± 4.7 vs IR: 39.6 ± 3.7). Regarding the cardiovascular parameters, central injection of IR caused a significant increase in heart rate during hypoxia exposure (VEH: 342.5 ± 38.0 vs IR: 406.2 ± 16.8 beats.min‐1) without changing arterial pressure. These effects were only observed in awake conditions, with no changes evidenced during sleep. No difference in cardiorespiratory and metabolic parameter were observed under CO2 exposure after central IR injection. Therefore, our preliminary results suggest that IR caused a hypoventilation under room air conditions, possibly due to a lower ventilation, increased heart rate under hypoxic conditions, suggesting that this myokine also acts in the central nervous system to modulate breathing and cardiovascular parameters.

Method of System Identification for Air Conditioning Systems in Operation

This study aims to optimize the operation of an air conditioning (AC) system by tracking situational changes due to outside temperature, number of people and computers, and other factors. Therefore, we studied the accurate estimation of system parameters of an AC unit during operation. We modeled the AC system using the first-order plus dead time model and discretized it using the autoregressive with exogenous input model. We developed a technique to estimate the system parameters using Bayesian optimization. Here, the system parameters are values that determine the physical characteristics of the combined air conditioning system and room. Therefore, we determined that there are cases where the characteristics deteriorate after repeated estimation. By solving this problem, we were able to establish a practical system. Keywords—ARX time-series model, Bayesian optimization method, First-order plus dead time, Gaussian process, PID control

Experimental Investigation of Using Liquid Suction Heat Exchanger with Condensed Cold-Water on the Performance of Air Conditioning System

This paper reports experimental investigation of using liquid suction heat exchanger (LSHX) with condensed cold-water (LSHX-CW) on the performance of a split type room air conditioning. To this end, we used a large room of a residential house of 64 m3 equipped with a 2-tons conventional commercial split-type air conditioner fitted with R22. The coaxial design of LSHX-CW allows to exchange heat between the vapor and liquid refrigerants in the center part and condensed water and the warm liquid refrigerant on the outer part. LSHX-CW was well insulated on the outside to reduce heat transfer with ambient. The air conditioning was tested several times for three scenarios namely, conventional system, system with LSHX alone and LSHX with condensed water LSHX-CW. Experimental results showed that the use of LSHX-CW improved the performance of air conditioning noticeably when compared to the use of LSHX alone. The maximum LSHX-CW effectiveness was 7.67%. The pressure discharge line and electricity consumed decreased by 8.23% and 9.40% respectively.

Experimental Investigation of Energy Efficient Room Air Conditioners for Mini-Stores

An experimental investigation of energy efficiency room air conditioners for the mini-stores was presented and illustrated in the paper. The experiment has been carried out in two well-insulated rooms with two different compressor technologies (fixed-speed and inverter) and essential equipment in a laboratory located at the School of Heat Engineering and Refrigeration (Hanoi University of Science and Technology). The authors conducted the test with three different heat load categories and weather conditions to examine the energy efficiency based on several factors such as room temperature and power consumption of air conditioner from records. Results show the significant effect of various aspects on the efficiency and the behaviour of air-cooled air conditioners including the indoor heat load and the outdoor temperature. The results also suggest a suitable cooling capacity choice that helps improve the energy efficiency of air conditioners besides the technical data such as CSPF (or SEER) and power consumption.

Experimental investigation on indoor environment and energy performance of convective terminals

The indoor environment and energy performances of convective terminals have been widely studied under the strong heating demands in cold regions. As different operative conditions affect the performances of heating devices, investigating these factors under different conditions can help improve the performances. In this study, the thermal performances of fan coil units (FCUs) and room air conditioners (RACs) were studied using comparative experiments, based on overall indoor environmental factors, local discomfort indices, energy performances, terminal characteristics, and integrated analysis. The results for the indoor environment were classified into different types, with the aim of analyzing approaches to obtaining a comfortable environment. The proper operating conditions reduce the percentages of dissatisfied caused by vertical temperature, floor temperature, and radiant asymmetry by 30.0%, 9.7%, and 28.8% for FCUs, respectively, and by 45.8%, 22.2%, and 0.2% for RACs, respectively. Long-term operation, high airspeed, downward air supply, and low set-point temperature were recommended to form a comfortable environment. The energy efficiency is improved by 9.6% and 2.7% with a low set-point temperature and downward supply air. The factors influencing thermal comfort and energy consumption are systematically analyzed, and the differences between continuous and intermittent convective terminals are compared.

Environmental satisfaction, mood and cognitive performance in semi-outdoor space in the tropics

The use of semi-outdoor space for the well-being of occupants is promoted in the tropics. Although a semi-outdoor space is often used for break space, environmental satisfaction and work performance are unclear in a semi-outdoor space as work activity space compared with air-conditioned (AC) room. This study focuses on the use of semi-outdoor space for short-term work activities such as office work and meetings. Experiments were carried out to evaluate environmental satisfaction, mood and cognitive performance in the cool and warm seasons in an AC room and a semi-outdoor space in Singapore. Eighty-nine participants answered questionnaires and conducted cognitive performance tests of Stroop test, visual backward digit span test, typing test and mind map test for 70 min per case in the AC room and semi-outdoor space with or without the operation of a ceiling fan. We analyzed the relationships among environmental satisfaction, mood, work performance by Structural Equation Modeling. The conditions which 80% of participants accepted in the semi-outdoor space were thermal environment ranged from 23.3 °C to 30.1 °C SET*, lighting levels of more than 260 lx and noise levels of less than 48 dBA. No differences in cognitive performance were found between the AC room and semi-outdoor space (p > 0.05). Mood influenced work performance (p < 0.001) while environmental satisfaction did not (p = 0.28). Self-reported performance, especially stress, influenced creativity (p = 0.047). These findings lead to the possibility of short-term work activities in the semi-outdoor space without a decrease in work performance.

A framework for short-term energy consumption prediction based on room air conditioner group characteristics

Owing to the convenient installation, low energy consumption, wide applicability, and flexible operation of room air conditioner (RAC), high application potential can be achieved in terms of load dispatch or demand response by aggregating numerous single RACs’ loads. The diverse behaviors of single occupants using RACs caused by different individual demands is one of the main factors leading to deviations in short-term (e.g., hourly) energy consumption prediction. In addition, owing to the lack of suitable quantitative indicators and subjective data, previous studies are rarely focused on the group behaviors of RACs, which is more appropriate for obtaining specific regional energy consumption. Aiming at optimizing the regional power grid load fluctuations in residential building, this paper proposes a framework for predicting short-term energy consumption based on RAC group characteristics by randomly selecting approximately 2000 samples from a cloud data platform. First, this study constructs multi-dimensional group features and based on the clustering method identifies three typical groups of RACs: i) Cluster a: continuous operation in summer and high energy consumption behavior; ii) Cluster b: annual intermittent operation and high energy consumption behavior; iii) Cluster c: mainly continuous operation in summer and energy-saving behavior. Second, the study generates five different aggregation sizes of RACs and integrates them with feature selection and random forest algorithms, to predict the hourly energy consumption of a residential RAC group. High precision achievement is shown by indicator indexes, such as the coefficient of determination (R2) reaches 90% and the relative mean absolute percentage error (MAPE) is basically within 15%. Finally, by adjusting the group behavior of the load aggregator scenarios of the above three RAC groups in this method, peak shaving capacity of approximately 35% is realized on a typical summer day.

Environmental Effects on Viable Virus Transport and Resuspension in Ventilation Airflow.

To understand how SARS-CoV-2 spreads indoors, in this study bovine coronavirus was aerosolized as simulant into a plexiglass chamber with coupons of metal, wood and plastic surfaces. After aerosolization, chamber and coupon surfaces were swiped to quantify the virus concentrations using quantitative polymerase chain reaction (qPCR). Bio-layer interferometry showed stronger virus association on plastic and metal surfaces, however, higher dissociation from wood in 80% relative humidity. Virus aerosols were collected with the 100 L/min wetted wall cyclone and the 50 L/min MD8 air sampler and quantitated by qPCR. To monitor the effect of the ventilation on the virus movement, PRD1 bacteriophages as virus simulants were disseminated in a ¾ scale air-conditioned hospital test room with twelve PM2.5 samplers at 15 L/min. Higher virus concentrations were detected above the patient’s head and near the foot of the bed with the air inlet on the ceiling above, exhaust bottom left on the wall. Based on room layout, air measurements and bioaerosol collections computational flow models were created to visualize the movement of the virus in the room airflow. The addition of air curtain at the door minimized virus concentration while having the inlet and exhaust on the ceiling decreased overall aerosol concentration. Controlled laboratory experiments were conducted in a plexiglass chamber to gain more insight into the fundamental behavior of aerosolized SARS-CoV-2 and understand its fate and transport in the ambient environment of the hospital room.

Space Cooling Market in Europe: Assessment of the Final Energy Consumption for the Year 2016

This study investigates Europe’s space cooling energy field. The work aims to assess the European Union (plus the United Kingdom) final energy consumption for space cooling in both the residential and service sectors with 2016 as a baseline. An extensive literature review of datasets and journal papers has been conducted to fill the knowledge gaps of the investigated energy branch. The European space cooling market is mainly dominated by vapour compression (VC) technologies which, in this study, have been grouped as room air conditioners (RACs) and centralized air conditioners (CACs). These technology groups have been investigated, and their installed capacities, energy efficiency levels (seasonal energy efficiency ratio—SEER), equivalent full load hours (EFLHs), and amount of space cooling units installed have been identified as essential parameters to calculate the final energy consumption for space cooling. Overall, the total value of the European final energy consumption for the space cooling sector, including both the residential and service sectors, results in 106 TWh/year.

In vitro study on the effects of exogenic fibrolytic enzymes produced from Trichoderma longibrachiatum on ruminal degradation of olive mill waste.

Olive mill waste is low-quality feed and rarely used in ruminant nutrition because of its high lignocellulose content, the existence of anti-nutritional factors such as total polyphenol and condensed tannin, and low protein contents. This in vitro research was conducted to valorize this waste (crude olive cake, extracted olive cake, and olive leaves) using an exogenous fibrolytic enzyme produced from Trichoderma longibrachiatum in ruminal nutrition. The enzymatic activity of this additive was 1161 units of endoglucanase per millilitre, 113 units of exoglucanase per millilitre, and 2267 units of xylanases per millilitre. This treatment was applied by spraying substrates with four doses: 0 (control), 1 (low), 2 (medium), and 4 (high) of dry matter olive mill waste in an air-conditioned room at 26 for 12 h before in vitro incubation.For the crude olive cake, this additive at high doses increased degradation of 14 % of cellulose and 8 % of hemicellulose compared with the control at 12 h before the in vitro incubation. Consequently, it increased dry matter solubility and reduced sugars at this period compared to the control. Upon ruminal incubation, the high dose of exogenous fibrolytic enzyme increased the gas production from the immediately soluble fraction and insoluble fraction, the rate of gas production for the insoluble fraction, the dry matter degradability by 26 %, the organic matter degradability by 24 %, the metabolizable energy value by 28 %, and the microbial crude protein production by 24 % compared with the control. For olive leaves, an exogenous fibrolytic enzyme at medium dosage can also hydrolyse the hemicellulose compound, release fewer sugars, and increase dry matter solubility compared with the control at 12 h before the in vitro incubation.Upon in vitro incubation, the medium dose increased the gas production from immediately soluble and insoluble fractions, the rate of gas production for the insoluble fraction, the dry matter degradability by 13 %, the organic matter degradability by 11 %, the metabolizable energy value by 12 %, and the microbial crude protein production by 12 % compared with the control. However, the highest dose altered the gas production from insoluble fractions and decreased microbial crude protein production by 6 % compared with the control. Under the same conditions, an exogenous fibrolytic enzyme applied to extracted olive cake did not produce any effect in the chemical composition and nutritional value. These results showed clearly that effectiveness of exogenous fibrolytic enzyme varied with incubated waste. Increasing the nutritional value of crude olive cake and olive leaves using an exogenous fibrolytic enzyme can encourage breeders to use this waste as feed at a low cost in animal nutrition. This valorization of waste is a good solution to reduce pollution of soils and groundwater caused by throwing out this polluted waste into the environment.

Performance analysis of sustainable solar energy operated ejector refrigeration system with the combined effect of Scheffler and parabolic trough collectors to lower greenhouse gases.

The work aims to analyse an ejector refrigeration system powered with solar energy through serially connected collectors to lower greenhouse gases. The collectors chosen for the work are Scheffler and parabolic collectors with an area of 2.5 m2 and 6 m2, respectively. The steam generated by the collectors is stored temporarily in a 15-l storage tank. The thermic fluid transfers heat between the steam storage tank and refrigerant, and thus the generator temperature increases. This design was intended as an alternate for a traditional 3.5kW room air conditioner with substantially lower energy consumption. This modified system consumed lesser energy input of about 20-30% than conventional air conditioners. Further, for the same specification, the ejector system has consumed less power of about 2.475kW than the traditional refrigeration system.

Airflow to disperse refrigerant leaks from hydrocarbon refrigeration systems✰

Whilst R290 is currently used to a limited extent in room air conditioners there is a desire for wider application due to its excellent performance and negligible global warming potential. The product standard IEC 60335–2–40 specifies requirements to limit the allowable refrigerant charge in such a way that it obstructs the wider use of R290. Airflow of an indoor unit can be used to dilute a refrigerant leak, enabling substantially greater charge quantities to be used. A numerical model based on entrainment theory was developed and supported by analysing the behaviour of experimentally simulated releases under various conditions with indoor unit airflow. The work determines the minimum airflow rate necessary to prevent formation of a flammable concentration within the room. Further, the work includes determination of appropriate response time and leak rate to initiate airflow once a leak has begun. The developed methodology can equally be applied to commercial refrigeration units and other flammable refrigerants.

Effect of walking in heat-stressful outdoor environments in an urban setting on cognitive performance indoors

Office workers and students in Japan routinely move between air-conditioned indoor environments and heat-stressful outdoor environments in summer. It is possible that a short walk in the outdoor environment affects workers' and students’ cognitive performance. However, it is unclear. This study aimed to investigate the effect of walking in a heat-stressful outdoor environment on indoor cognitive performance. In the experiments, a total of 96 participants took a mathematical addition test in an air-conditioned room before and after walking in an actual outdoor environment. Results of the experiments showed that walking outdoors under heat-stressful conditions (UTCI ≧ 44 °C) for 15 min decreased the cognitive performance (percentage of correct answers to numbers of problems solved) by 3.6% compared with that before walking. An analysis focusing on the sleep duration showed a negative relationship between sleep duration and the decrease in cognitive performance. This tendency became particularly clear among the participants whose sleep duration was less than 5 h. The reduction of cognitive performance was more pronounced in male participants than in female participants. Sleep-deprived men who walk in a heat-stressful outdoor environment are more likely to exhibit poor cognitive performance when they return to an air-conditioned room. Japanese office workers and students, especially men, need to be aware of this as they work and study.