Analysis of EEG, Cardiac Activity Status, and Thermal Comfort According to the Type of Cooling Seat during Rest in Indoor Temperature

In this study, electroencephalogram (EEG) and cardiac activity status of the human body while using various types of seats during rest were analyzed in indoor summer conditions. Thermal comfort was also evaluated through a subjective survey. The EEG, cardiac activity status, and subjective survey during rest indicated that the use of ventilation and cold water-cooling seats was effective. This effectiveness was because of the θ-wave and α-wave activation, sensorimotor rhythm, β-wave reduction, and left hemisphere activation, demonstrating that the conditions applied were suitable for rest. According to the analysis of the subjective questionnaire survey, the use of ventilation and cold water-cooling seats provided a more pleasant state than the basic seat, improving the subject’s warmth and comfort, and also the concentration. In addition, the use of a cold water-cooling seat provided the highest satisfaction level, being the most favorable condition for rest

Economic Analysis of Flat-Plate and U-Tube Solar Collectors Using an Al2O3 Nanofluid

In this study, the efficiencies of flat-plate and U-tube solar collectors were investigated experimentally when an Al2O3 nanofluid was used as a working fluid and compared to those of solar collectors using water. The energy savings and CO2 and SO2 generated were calculated and compared to those of solar collectors using water. In addition, based on the experimental results, an economic analysis of the use of solar collectors in various countries was performed. As the concentration of the Al2O3 nanofluid increased, the performance of the solar collector improved. The highest efficiency for the solar collectors was shown at the concentration of 1.0 vol % with the nanoparticle size of 20 nm. The maximum efficiencies of the flat-plate and U-tube solar collectors using a 1.0 vol %-Al2O3 nanofluid with 20-nm nanoparticles was 74.9% and 72.4%, respectively, when the heat loss parameter was zero. The efficiencies of the flat-plate and U-tube solar collectors using Al2O3 nanofluid were 14.8% and 10.7% higher, respectively, than those using water. When 50 EA (each) flat-plate solar collectors were operated for one year using an Al2O3 nanofluid, the coal use, generated CO2, and generated SO2 were 189.99 kg, 556.69 kg, and 2.03 kg less than those of solar collectors using water, respectively. In addition, the largest electricity cost reduction was in Germany

Experimental Study of Thermal Comfort Based on Driver Physiological Signals in Cooling Mode under Summer Conditions

In this study, electroencephalogram (EEG), photo-plethysmography (PPG), and surface temperature measurements of subjects were taken while performing a driving simulation when the cabin and vent discharge air temperature in summer were changed from discomfort to comfort conditions. Additionally, subjective questionnaires were used to analyze the subject’s thermal comfort under the various driving environments. As a result, the surface temperatures of the forehead, left hand, right hand, and abdomen of the subject during driving were reduced by 2, 0.97, 2.18, and 5.86 °C, respectively, by operating a 12.5 °C vent cooling function at a cabin temperature of 35 °C. As a comprehensive analysis of the subjective survey, PPG, and EEG results, total power (TP), the standard deviation of N-N interval (SDNN), and the root mean square of successive differences (RMSSD) of subjects increased and stress index decreased at cabin and vent discharge air temperatures of 30–27.5 °C and 16.5–18.5 °C, respectively. Furthermore, the relative sensory motor rhythm (SMR) wave and concentration index (CI) of the frontal lobe tended to increase under the same temperature conditions. Accordingly, it was confirmed that these temperature conditions provided a pleasant driving environment for the driver and increased concentration on driving

Evaluation on the Performance of Automobile Engine Using Air Injection Nozzle in the Intake Manifold

In the present study, a nozzle was used to improve the flow performance of an intake manifold, and its effects on the automobile engine output and the exhaust gas were experimentally studied. It was found that the engine output of a vehicle with a mileage of 30,000 km increased by 4.7% and 6.5% when nozzles with diameters of 5 and 2.5 mm were used. In addition, the engine output of a vehicle with a mileage of 180,000 km increased by 3.3% and 13.3% when nozzles with diameters of 5 and 2.5 mm were used compared to those of the same vehicle when no nozzle was used. Thus, using a nozzle for the inflow of outside air created a uniform combustion environment to improve the engine output and reduce harmful exhaust gases, such as hydrocarbon, carbon monoxide, and nitrogen oxides, by generating vortexes inside the intake manifold and increasing the degree of mixing. Furthermore, the smaller nozzle with a diameter of 2.5 mm had greater effects

Investigation of performance and energy cost of automobile air-conditioner using alternative refrigerants based on thermal comfort using various cooling seats

During hot summer days, the rapid rise in temperature inside a vehicle and the direct transmission of radiant energy cause significant discomfort to drivers, and the driving distance of an electric vehicle is greatly reduced due to the operation of the air-conditioner. Therefore, it is essential to provide a thermally comfortable environment to the driver and reduce the energy consumption of air-conditioners in the EV. This study investigated the thermal comfort of the driver according to the use of a basic seat (BSS), ventilation seat (VLS), and cold-water seat (CWS) in the car cabin under summer condition. Also, based on thermal comfort, the system performance and energy cost of an automobile air-conditioner using various alternative refrigerants were analyzed and compared. As a result, when the CWS was used, the stress index of subjects was the lowest in the PPG, and the relative β/α of the subjects decreased in the EEG. In addition, the results of the subjective questionnaires and bio-signal measurement showed the most thermally comfortable when using the CWS. The COPs of the air-conditioner using R134a, R1234yf, R1234ze(E), and R152a increased by 19.3 %, 18.9 %, 19.0 %, and 19.3 %, respectively, and annual energy consumption of the air-conditioner decreased. In addition, in the five European countries, the annual electric charging costs and annual eq-CO2 emissions for using the CWS showed the most significant reduction in Germany. Therefore, it was confirmed that using CWS can provide a thermally comfortable environment for drivers inside the vehicle during summer and effectively reduce power consumption used for air conditioning in EVs

Performance Characteristics of Automobile Air Conditioning Using the R134a/R1234yf Mixture

In this study, the energy and exergy of an automobile refrigeration system using R134a and R134a/R1234yf were analyzed experimentally with respect to outdoor air temperature and compressor speed. As outdoor air temperature increased from 32.5 °C to 37.5 °C, the coefficient of performance (COP) and total exergy destruction rate of the refrigeration system using Mix30 decreased by 5.19% and 25.8% on average, compared to that of the system using R134a. The exergy efficiency of the Mix30 refrigeration system was on average 21.8% higher than that of the R134a system. As the compressor rotating speed increased from 1000 to 2000 rpm, the cooling capacity of the refrigeration system using R134a and R134a/R1234yf increased, while the COP decreased. The COP and total exergy destruction rate of the refrigeration system using Mix30 decreased by 4.82% and 19.5%, compared to that of the system using R134a. The exergy efficiency of the Mix30 refrigeration system increased on average by 20.7%, compared to that of the R134a system. The total exergy destruction rate of the automobile refrigeration system using R134a/R1234yf decreased with increase in R1234yf, while exergy efficiency increased. In addition, the exergy destruction rate of the automobile refrigeration system decreased as the amount of R1234yf in the R134a/R1234yf automobile refrigeration system increased