Search Results (7)

Battery electric vehicles (BEVs) are one promising approach to mitigating local greenhouse gas emissions. However, they still lag behind conventional vehicles in terms of maximum driving range. Using the heating, ventilation, and air-conditioning (HVAC) system reduces the maximum driving range of the vehicle even further since the energy for the HVAC system must come from the battery. This work investigates the impact of (1) an air–air heat exchanger and (2) an improved thermal insulation of a truck cabin on the heating performance of the HVAC system. Additionally, the required fresh-air volume flow rate to keep the CO₂ level within the truck cabin below the critical value of 1000 ppm is factored in. The results show that the two simple measures proposed could increase the energy efficiency of the truck’s HVAC system by 22%. When two persons are present in the truck cabin, a fresh-air volume flow of around 100 m³/h is required to keep the CO₂ concentration around 1000 ppm. These results prove that, even with simple measures, the energy efficiency of vehicles’ subsystems can be increased. In the future, more research will be necessary to further improve the energy efficiency of other vehicular subsystems. Full article

With the growing prevalence of lithium battery electric vehicles, the incidence of fires resulting from thermal runaway in lithium batteries is also on the rise. In contrast to conventional fuel vehicle fires, fires involving lithium battery electric vehicles exhibit distinct differences in fire dynamics, fire loads, and smoke characteristics. These variations impose more stringent requirements on the design of passive fire protection systems within tunnels. To evaluate the fire resistance performance of existing passive fire protection systems under electric vehicle fire conditions, this study first used PyroSim software 2022 (integrating FDS 6.7.9) to establish fire models for combustion engine trucks and electric trucks, comparing the combustion characteristics of both types of fires without insulation lining materials. Based on the electric truck fire model, different insulation lining materials were added. The analysis of the simulation results focused on the impact of the thermal conductivity and emissivity of each lining material on peak tunnel temperatures, aiming to identify the insulation lining material with the best fire resistance performance. The results indicate that the heat release rate, temperature distribution, toxic gas concentration, and smoke propagation of lithium battery combustion engine truck fires are all higher than those of combustion engine truck fires. Among the five insulation lining materials studied, SiO₂ gel material demonstrated superior fire resistance compared to the others. This research provides a scientific and rational basis for tunnel fire protection design and fire response strategies, aiming to mitigate the damage caused by lithium battery electric vehicle fires to tunnel lining structures. Full article

Due to legislations introduced to prevent global warming, vehicle manufacturers must find new ways to reduce CO₂ emissions. This paper explores a way to reduce rolling resistance by heat-insulating and covering a truck’s wheelhouse. Truck tyre rolling resistance was measured at +5 °C ambient temperature for consecutive speed steps in a climate wind chamber with and without heat insulation. The study showed that by encapsulating and insulating the wheelhouse, already generated strain-induced heat could be kept in the tyre, consequently leading to reduced rolling resistance. The tyre shoulder temperature was monitored during the experiments along with the tyre pressure. When the wheelhouses were encapsulated, a significant reduction in rolling resistance and an increase in tyre pressure and temperature were measured at all evaluated speed levels. Full article

This paper aims to provide an updated review and current understanding of the impact of extreme temperatures—focusing on heat stress (HS)—on the quality of pork and poultry meat, particularly amidst an unprecedented global rise in environmental temperatures. Acute or chronic HS can lead to the development of pale, soft, and exudative (PSE) meat during short transportation or of dark, firm, and dry (DFD) meat associated with long transportation and seasonal changes in pork and poultry meat. While HS is more likely to result in PSE meat, cold stress (CS) is more commonly linked to the development of DFD meat. Methods aimed at mitigating the effects of HS include showering (water sprinkling/misting) during transport, as well as control and adequate ventilation rates in the truck, which not only improve animal welfare but also reduce mortality and the incidence of PSE meat. To mitigate CS, bedding on trailers and closing the tracks’ curtains (insulation) are viable strategies. Ongoing efforts to minimize meat quality deterioration due to HS or CS must prioritize the welfare of the livestock and focus on the scaleup of laboratory testing to commercial applications. Full article

Firefighting in high-rise buildings remains a difficult problem in the world because fire extinguishing equipment and tactics have many deficiencies in dealing with such building fires, especially for buildings higher than 50 m. In the present study, the LY100 fire extinguishing system is taken as an example to introduce the application of the fire drone in the fire control of high-rise buildings. The LY100 fire extinguishing system mainly contains the twin-rotor drone, high-pressure liquid fire extinguishing equipment, pressure fire extinguishing equipment, associated vehicle and extinguishing agent. The LY100 system can be deployed quickly and operated flexibly. Based on such advantages, the indoor fire, exterior thermal insulation layer fire and top platform fire of high-rise building can be extinguished in a timely manner with the LY100 system. In addition, four kinds of firefighting tactics are described in this paper, including one drone operation, double drone cooperative operation, three or more drone cooperative operations, and cooperating with the lifting fire truck. Finally, the experiments are presented to verify the spraying distance of the fire drone system. Full article

The cold chain—the system of refrigerated storage and transport that provides fresh produce or other essentials to be maintained at desired temperatures and environmental conditions—is responsible for substantial energy consumption and greenhouse gas (GHG) emissions, and failures in the cold chain lead to food and energy waste. Here, we introduce the mini container concept as an alternative to conventional reefers, particularly for small growers. Mini containers are relatively small, insulated boxes, with environmental conditions controlled by an electric-powered central driving unit, which can be aggregated as needed and transported by non-refrigerated trucks and trailers. We analyze the energy consumption and GHG emissions for the transport of tomatoes in two cities representing contrasting climates, Phoenix, Arizona, and Chicago, Illinois, for conventional reefers and the proposed mini containers. These two cities provide the opportunity to compare the energy consumption and GHG emissions for the proposed mini containers versus conventional refrigerated transport under extremely different climate conditions. The results show that, as expected in both cases, as the ambient air temperature increases, the energy consumption and GHG emissions also increase. For partial reefer loads less than 72% and 85% for Phoenix and Chicago, respectively, the use of the mini containers reduces energy consumption and GHG emissions because of the reduced volume requiring refrigeration. In general, since the mini containers are fully electrified, their corresponding GHG emissions can be dramatically reduced, and since the fresh produce can be pre-cooled with renewable energy, GHG emissions can even be eliminated. Full article

In road construction, it can happen that, for different reasons, the time between hot-mix asphalt (HMA) production and paving is extended to some hours. This can be reflected in several problems such as mix cooling and temperature segregation, but also in an extremely severe bitumen ageing due to its prolonged exposure to high temperatures. This paper deals with the investigation of these phenomena both in the laboratory and on site. In particular, the first part of the research aimed at observing the influence of the conditioning time, when the loose HMA is kept in the oven at a high temperature, on the mix properties. The second part focused on the ageing/cooling that happens on site during HMA hauling, as a function of time and type of truck. Temperatures were monitored using a thermal camera and different probes, and gyratory compactor specimens were produced by sampling some HMA from the trucks every 1 h for 3 h. The results showed that HMA stiffness rises if the time when the loose mix stays in the laboratory oven before compaction increases. However, on site, the HMA volumetric and mechanical properties do not change with hauling time up to 3 h, probably because the external material in the truck bed protects the HMA core from the access of oxygen, hindering bitumen oxidation and loss of volatiles. The temperature monitoring highlighted that temperature segregation, after 3 h hauling, can be higher than 30 °C but it can be reduced using insulated truck beds. Full article