This paper presents an analysis of the mileage energy consumption for an electric passenger vehicle in terms of the introduction of numerous speed limits. Regulations concerning the limiting of vehicle speed to 30 km/h in cities or residential areas are particularly common. This restriction is intended to increase traffic safety, but at the same time introduces increased mileage fuel or energy consumption in electric drivetrain. Regardless of the energy carrier, any increase in energy causes negative effects for the environment. The analysis was focused on the mileage energy consumption of electric passenger cars for a constant speed under real traffic conditions. During the tests, the tested vehicles’ speed on a specially designated road section was changed gradually by 10 km/h, with simultaneous recording of the car’s traction parameters and mileage energy consumption. An analysis of the mileage energy consumption was then carried out for the assumed fleet of cars travelling one after another (in a so-called traffic jam), while maintaining a safe distance. This allowed for the calculation of the environment’s energy burden caused by a fleet of vehicles travelling on a given road section, indicating that a reduction in vehicle speed causes an increase in the vehicles’ energy consumption. Both total and mileage energy consumption of electric vehicles were analysed during the tests.

A lot of novel surface treatment technologies have appeared over the last few decades, offering great possibilities for practical use. Modified surfaces have confirmed their successful application in thermal engineering for boiling heat transfer enhancement and single-phase convection. Several classification approaches for boiling surfaces exist in the literature; however, a full, physically based, and commonly accepted universal system is still missing. This paper proposes such a classification system, based on considerations of physical mechanisms underlying the nucleation process and enhancement mechanism during different stages of vapor bubble growth. It also presents an overview of recent advances in the development of enhanced boiling surfaces.

The results of experimental studies on heat transfer and pressure drop with forced convection of air and liquid ethylene glycol in internally finned tubes are presented. The tubes with inte-gral fins were machined of an aluminium alloy by extrusion, the fins were straight along the tube or helically twisted, and their tips almost reached the tube axis. Depending on process parameters, the heat transfer coefficients of finned tubes obtained with these fluids are by factors of 3 to more than 8 higher than of plain tubes. The pressure drop is correspondingly higher for finned than for plain tubes. The heat transfer improvement cannot be explained quantitatively simply by a linear coupling with the enhancement of the surface area due to fin-ing. In addition to this quantitative effect, there is also a qualitative effect that is caused by the shape of the fins. The true heat transfer improvement appears to be governed by efficient secondary flows establishing in the flow channels between neighbouring fins which interact with the swirling core flow in the middle of the tube cross-section.