No abstract

Electric vehicles (EVs) generally use an electric heating system to provide heat. However, the heating system consumes a large amount of energy, and therefore reduces the mileage of the vehicle. The energy consumption can be reduced by replacing the electric heating system with a heat pump air conditioning system. Such systems achieve an effective heating of the vehicle interior, but do not provide a defog or dehumidification function. Consequently, the inside surface of the windshield tends to fog in cold weather; leading to poor driver visibility and an impaired road safety. Accordingly, the present study proposes a novel high-efficiency heating, ventilation and air conditioning (HVAC) system with both heating and defog/dehumidification functions for electric vehicles. The effectiveness of the proposed system is investigated experimentally using a simulated cabin placed in a temperature and humidity-controlled test chamber. The experimental results confirm that the HVAC system achieves the required cooling, heating and defog/dehumidification functions and meets the corresponding standards. Moreover, the application of HVAC in EVs could lead to significant electrical power saving effect.

This study investigated the spray cooling heat transfer performance of Al2O3-water nanofluid given four different subcooling degrees (0 °C, 10 °C, 20 °C, and 30 °C). The results showed that the subcooled nanofluids were ranked in order of a reducing spray cooling heat transfer performance as follows: 20 °C, 10 °C, 0 °C, and 30 °C. On average, the heat transfer coefficient obtained using the nanofluid with 20 °C subcooling was around 8.3%, 8.6%, and 15.6% higher than that obtained with 10 °C, 0 °C, and 30 °C subcooling, respectively. However, the heat transfer performance decreased with an increasing spray operating time. The scanning electron microscopy observations showed that the reduction in the heat transfer coefficient was the result of a gradual increase in the thickness of the nano-adsorption layer on the heated surface as the spray operating time increased.

No abstract

This study investigates the air leakage ventilation phenomenon in a passenger car and examines its effects on the concentration of carbon dioxide in the cabin. A theoretical general equation (Q AL ¼ f½A car ðv 2 car Þ m 1 2 þ ½A fan ðv 2 fan Þ m 2 2 g 1=2) is proposed for predicting the air leakage ventilation rate. The validity of the equation is demonstrated by means of real car on-road experiments. The results show that when the car is at rest, the effect of the fan-supplied air speed on the air leakage ventilation rate is more apparent. However, for a moving vehicle, the contribution of the fan-supplied air speed to the cabin indoor air quality reduces, while that of the car speed increases. Applying a curve-fitting technique to the experimental data, it is shown that parameters A car , m 1 , A fan and m 2 in the proposed theoretical equation have values of 1:15 Â 10 À4 , 0.725, 1:6 Â 10 À3 and 0.315, respectively, for the present experimental car (a Mitsubishi Galant). In general, the results obtained in this study suggest that a fractional fresh air ventilation mode should be employed to guarantee the ASHRAE standard for the minimum fresh air requirement of 2.5 l/s per individual at low driving speeds.