• Energy Research

Abstract The design of workwear has significant effects on worker performance. However, the current workwear for coal miners in Northern China is poor in fitness and thermal comfort. In this study, new workwear (NEW) for coal miners was developed with the design features providing better cold protection and movement comfort performance, as compared with a commonly worn workwear (CON). To evaluate the effectiveness of NEW, we conducted human trials which were performed using simulated work movements (i.e., sitting, shoveling, squatting, and crawling) in a climate chamber (10°C, 75% RH). Physiological measurements and perceptual responses were obtained. The results demonstrated that the local skin temperatures at chest, scapula, thigh, and calf; mean skin temperatures,; and thermal comfort in NEW were significantly higher than those in CON. NEW also exerted an improvement in enhancing movement comfort. We conclude that NEW could meet well with the cold protective and mobility requirements.

Because of rapid urbanization, traffic problems, and other factors, underground spaces have been used more in the twenty-first century. Large underground spaces are required for underground city, metro, tunnel, mine, industrial and agricultural engineering, and civil air defense engineering. Underground spaces with varying thermal, ventilation, and lighting environments can face problems of comfort, health, and safety. High temperatures, high humidity, difficulty in flue gas emission, harmful microorganisms, radon, and physical and psychological problems are examples of issues. Air quality control technologies for underground spaces, such as ventilation, dehumidification, natural energy utilization, smoke extraction, and ventilation resistance reduction, are discussed. Ventilation for smoke-proofing/evacuation is also extensively addressed.

Abstract Personal comfort systems usually use a single heat transfer mode to improve local thermal comfort by only stimulating one local body part. A novel hybrid convection and radiation combined terminal device, which could be used both in summer and winter, was proposed. A total of sixteen human subjects took part in a winter subjective experiment to test its performance on the improvement of occupants’ thermal comfort and cognitive performance in winter. Occupants’ thermal comfort, air movement perception, eye dryness and cognitive performance were investigated. The results showed that 88% of the subjects accepted 16℃ room temperature. 0.4 m/s air speed to face and abdomen parts is acceptable when convective airflow temperature is 4.5℃ higher than room temperature. No dry eye discomfort was reported while using a controllable device. Furthermore, subjects’ cognitive performance, including self-evaluate work performance, math (mental performance) and typing performance (dexterity), could be significantly improved by using the novel device. Energy efficient thermal comfort can be achieved by less intensifying ambient heating temperature to 16℃ in winter.

Abstract Liquid dehumidification air-conditioning (LDAC) systems are a promising dehumidification technology that reduce energy consumption. However, in hot and humid climates, liquid regeneration deteriorates the performance of regenerators and limits their applications. Therefore, developing methods to ensure regeneration performance in harsh climates as well as to reduce the droplet splatter is a challenging task that must be undertaken to advance the technology and make it viable. In this study, a novel regeneration method using the direct contact membrane distillation (DCMD) regenerator was applied to the LDAC system. The mathematical model of the DCMD solution regeneration process was developed and verified through PTFE hollow fiber membrane liquid regeneration experiments. The impacts of membrane length, temperature, concentration, and solution volume flow on the temperature and concentration of the resultant solution at the outlet, regeneration capacity mass transfer coefficient, membrane water flux, and heat flow were analyzed. The results indicate that the concentration of the solution at the outlet linearly increases from 34.9% to 35.9% when the solution is heated from 40 to 85 °C. However, when the temperature of the solution is less than 45 °C, the solution concentration at the outlet is lower than that at the inlet, which indicates that the regeneration capacity is negative. Thus, the solution temperature at the DCMD regenerator inlet should be maintained at >65 °C to provide a higher and stable regeneration efficiency. Finally, it was established that a flow rate that is either extremely high or low would impair the DCMD regeneration, whilst a volume flow of 1800 ml min−1 is still most appropriate for the regenerator to regenerate high-concentration solutions. Research on the cold side indicates that when the temperature of the water does not exceed 30 °C, the regenerator still has the ability to regenerate, and increasing the volume flow of water can enhance the regeneration effect.

The impact of heat waves arising from climate change on human health is predicted to be profound. It is important to be prepared with various preventive measures for such impacts on society. The objective of this study was to investigate whether personal cooling with phase change materials (PCM) could improve thermal comfort in simulated office work at 34°C. Cooling vests with PCM were measured on a thermal manikin before studies on human subjects. Eight male subjects participated in the study in a climatic chamber (T(a) = 34°C, RH = 60%, and ν(a) = 0.4 m/s). Results showed that the cooling effect on the manikin torso was 29.1 W/m(2) in the isothermal condition. The results on the manikin using a constant heating power mode reflect directly the local cooling effect on subjects. The results on the subjects showed that the torso skin temperature decreased by about 2-3°C and remained at 33.3°C. Both whole body and torso thermal sensations were improved. The findings indicate that the personal cooling with PCM can be used as an option to improve thermal comfort for office workers without air conditioning and may be used for vulnerable groups, such as elderly people, when confronted with heat waves.Wearable personal cooling integrated with phase change materials has the advantage of cooling human body's micro-environment in contrast to stationary personalized cooling and entire room or building cooling, thus providing greater mobility and helping to save energy. In places where air conditioning is not usually used, this personal cooling method can be used as a preventive measure when confronted with heat waves for office workers, vulnerable populations such as the elderly and disabled people, people with chronic diseases, and for use at home.

Face and neck cooling has been found effective in improving thermal comfort during exercise in the heat despite the fact that the surface area of human face and neck regions accounts for only 5.5% of the entire body. Presently very little documented research has been conducted to investigate cooling the face and neck only to improve indoor thermal comfort. In this study, two highly energy efficient wearable face and neck cooling fans were used to improve occupant thermal comfort in two warm indoor conditions (30 and 32 °C). Local skin temperatures and perceptual responses while using the two wearable cooling fans were examined and compared. Results showed that both cooling fans could significantly reduce local skin temperatures at the forehead, face and neck regions by up to 2.1 °C. Local thermal sensation votes at the face and neck were decreased by 0.82–1.21 scale unit at the two studied temperatures. Overall TSVs decreased by 1.03–1.14 and 1.34–1.66 scale units at 30 and 32 °C temperatures, respectively. Both cooling fans could raise the acceptable HVAC temperature setpoint to 32.0 °C, resulting in a 45.7% energy saving over the baseline HVAC setpoint of 24.5 °C. Furthermore, occupants are advised to use the free-control cooling mode when using those two types of wearable cooling fans to improve thermal comfort. Finally, despite some issues on dry eyes and dry lips associated with those wearable cooling fans, it is concluded that those two highly energy-efficient wearable cooling fans could greatly improve thermal comfort and save HVAC energy.

Temporarily occupied space (TOS) is defined as a conditioned space in which most of occupants stay for less than a certain period (e.g., 40 min). Base on the concept of TOS, specific application scenarios for transient and non-uniform thermal environments were explored by chamber tests. In the study, human subjective assessments were obtained from 16 subjects (8 males and 8 females). The synergy effect of temporal and spatial alliesthesia in TOS was quantitatively analyzed, which could achieve energy efficient thermal comfort. The synergy effect extended human thermal comfort under lower neutral temperature.