N. Kyriakis

Conjugate Heat and Mass Transfer from a Drying Rectangular Cylinder in Confined Air Flow

Heat and mass transfer from a porous body subject to convective drying is investigated numerically based on Luikovs equations. The air flow is assumed incompressible, two-dimensional, laminar, confined in a channel, and parallel to the rectangular-shaped solid. The finite-volume method is used and the computed temporal and spatial variations of moisture content, temperature, concentration, and flow parameters for two different flow rates are analyzed. Two flow configurations are studied: with and without a flow divider upstream of the cylinder in an attempt to eliminate the presence of separation zones and study their effect on drying. It was found that such effects may greatly affect the drying process, along with frontal area stagnation and the thickness of the body.

Reconciliation of macroscale and microscale motor vehicle emission estimates

A generalised approach is presented for the compilation of spatially and temporally disaggregated motor vehicle emission inventories. Top-down (macroscale) and bottom-up (microscale) estimates of activity data and emission factors are carried out independently and are then compared and reconciled in order to produce estimates with the fewest possible uncertainties. The proposed methodology was applied with some simplifications in the urban area of Thessaloniki, and a disaggregated traffic emission inventory was created, showing that in principle it is possible to bring in line top-down and bottom-up assessments.

Energy consumption of a residential building: comparison of conventional and RES-based systems

The energy needs of a typical one-family house in the Thessaloniki area for heating, cooling and domestic hot water production are calculated. The calculations are based on the typical average daily consumption of hot water and on the degree-day method for heating and cooling. The results are finally translated into thermal energy consumption, assuming the typical Greek situation (heating with diesel oil boilers and conventional radiators, cooling with local air-to-air split-type heat pumps and hot water production with electric heaters). The same energy needs are assumed to be covered by a vertical closed loop ground heat exchanger combined with a water-to-water heat pump system with fan-coils for heating and cooling and a thermosyphonic solar system for domestic hot water production. The ground heat exchanger/heat pump system efficiency is determined using data from an existing and continuously monitored similar system installed in the broader area of Thessaloniki. The solar system load coverage is calculated using the f-chart method. The energy consumption of the renewable energy systems is calculated and compared to that of the conventional system. The results prove that significant energy savings can be achieved.

Actual emissions of vehicles of the N1 category

Abstract Thirty in-use vehicles (both petrol and diesel-powered) of the N1 international category were tested under loaded and unloaded conditions (i.e. a total of 60 vehicles), using the FTP75 and urban and extra-urban European driving cycles. The emission factors derived are presented. Emission factor correlations for the different cycles are given. Based on the experimental results and the available literature, the possibilities for emission standards are discussed, taking into account the availability of emission control systems.

Time dependence of traffic emissions in the urban area of Thessaloniki

Abstract The available traffic load data were evaluated and proved that three time zones with relatively constant traffic load can be identified. The driving patterns of the city as well as of the individual roads were derived, based on 1500 km of real time speed recordings. The driving patterns were derived on a 24 h basis as well as for each time zone with constant traffic load. Based on the mean speed of these driving patterns, on the emission factors experimentally determined from 580 passenger cars, the CORINAIR methodology and the vehicle fleet data for the area of Thessaloniki, mean annual emissions were calculated. The time dependence of the emission factors of each road (kg/km·h) was determined, using the same procedure and taking into account the traffic load data and the traffic load synthesis per hour.

Parametric study for a ceramic diesel particulate trap application on a light duty truck

The paper presents the results of an experimental evaluation of a number of parameters affecting both the loading and the regeneration conditions of the cellular cordierite diesel particulate filler (DPF), when a cerium based fuel additive is used to enhance regeneration at low temperatures. The parameters studied comprised the size of the filter, its positioning along the exhaust pipe and the additive concentration in the fuel. The results show that filter regeneration was always possible at continuous low speed driving at relatively high filter backpressure levels, with a measurable effect on fuel consumption. On the other hand, the New European Driving Cycle, with alternate urban and extra urban operation of the vehicle, always provides the necessary conditions for trap regeneration, affecting neither the fuel consumption nor the maximum engine power output.

An Identification Approach for Performance Characterization and Simulation of Large Solar Heating Systems

An efficient and simple simulation methodology for large solar water heaters has been developed, based on the input-output approach. This approach gives the ability to estimate the expected energy behavior under specific meteorological condition by using the characteristic Input-Output equation of the solar system. The coefficients of this equation can be determined through an experiment-based identification procedure The proposed methodology can be used not only for optimization of the system performance but also for evaluation of experimental results of an existing system in order to improve it further.

Effects of low aromatics and low sulphur diesel fuels on particulate emissions

The particulate emissions of a diesel passenger car running on 13 fuels (including a reference one), featuring major differences in aromatic content and minor differences in specific energy were measured, following the legislated European certification procedure. The tests included PM mass measurements, volatile and non-volatile PM split and particle number and size distribution over the NEDC, using an Electrical Low Pressure Impactor (ELPI). The paper presents the results of the measurements and discusses the effects of fuel properties on the physical and chemical character of the particulates. It was found that the PM and CO emissions are in good correlation with the aromatic and sulphur content of the fuel, the size distribution of particulates being also affected.