Experimental investigation of the thermosiphonic phenomenon in domestic solar water heaters

The deeper understanding of the ‘thermosiphonic phenomenon’ and the identification of the key parameters affecting it, is the main aim of a research project currently in process in Cyprus. In this work a review of the existing standards and scientific knowledge concerning domestic solar water heaters is presented. The first preliminary results of the experimental investigation of the ‘thermosiphonic phenomenon’ in domestic solar water heaters are also presented. For this purpose a special test rig was set up and equipped with all sensors necessary to measure all parameters that are most likely to affect the ‘thermosiphonic phenomenon’. All tests were conducted according to ISO 9459- 2:1995(E). At first, the solar collector was tested according to EN12975-2:2006 in order to determine the thermal performance characteristics at a flow and operation conditions specified by the standard. Consequently, the efficiency of the collector operating thermosiphonically was calculated based on quasi-dynamic approach. Finally, a series of correlations were attempted using the data acquired when the collector is operating themosiphonically which are the following: (i) the temperature difference of the water at the outlet and the inlet of the collector (ΔΤ) with the solar global radiation, (ii) the water mass flow with the solar global radiation, (iii) the water mass flow with the temperature difference of the water at the outlet and the inlet of the collector (ΔΤ). The results of the data analysis showed that these parameters are very well correlated between them since the coefficient of determination (R2) is over 0.91 in all cases

Analysis of spatiotemporal data to predict traffic conditions aiming at a smart navigation system for sustainable urban mobility

Urban traffic congestion created by unsustainable transport systems and considered as a crucial problem for the urbanised areas provoking air pollution, heavy economic losses due to the time and fuel wasted and social inequity. The mitigation of this problem can improve efficiency, connectivity, accessibility, safety and quality of life, which are crucial parameters of sustainable urban mobility. Encouraging sustainable urban mobility through smart solutions is essential to make the cities more liveable, sustainable and smarter. In this context, this research aims to use spatiotemporal data that taxi vehicles adequately provide, to develop an intelligent system able to predict traffic conditions and provide navigation based on these predictions. GPS (Global Positioning System) data from taxi are analysed for the case of Thessaloniki city. Trough data mining and map-matching process, the most appropriate data are selected for travel time calculations and predictions. Several algorithms are investigated to find the optimum for traffic states prediction for the specific case study concluding that ANN (Artificial Neural Networks) outperforms. Then, a new road network map is created by producing spatiotemporal models for every road segment under investigation through a linear regression implementation. Moreover, the possibility to predict vehicle emissions from travel times is investigated. Finally, an application with a graphical user interface is developed, that navigates the users with the criteria of the shortest path in terms of trip length, travel time shortest path and “eco” path. The outcome of this research is an essential tool for drivers to avoid congestion spots saving time and fuel, for stakeholders to reveal the problematic of the road network that needs amendments and for emergency vehicles to arrive at the emergency spot faster. Besides that, according to an indicator-based qualitative assessment of the proposed navigation system, it is concluded that it contributes significantly to environmental protection and economy enhancing sustainable urban mobility

Experimental Investigation of the Effect of Solar Collector’s Inclination Angle on the Generation of Thermosiphonic Flow

Cyprus is currently the leading country in the world with respect to the application of solar water heaters for domestic applications, with more than 93 % of the houses equipped with such a system. The great majority of these solar water heaters are of the thermosiphonic type. Currently, the knowledge about the parameters affecting the ‘thermosiphonic phenomenon’ is rather poor while on an international level (International Organization for Standardization, ISO, and Comité Européen de Normalisation CEN committees) there is no standard available to test thermosiphon solar collectors. The deeper understanding of the ‘thermosiphonic phenomenon’ and the identification of the key parameters affecting it is the main aim of a research project currently in process in Cyprus. In this chapter, the experimental results of the research project are presented. Specifically, a special test rig was set up and equipped with all the sensors necessary to measure all the parameters that are most likely to affect the ‘thermosiphonic phenomenon’. All tests were conducted according to ISO 9459-2:1995(E). The system was able to operate in various weather and operating conditions and could accommodate the change of inclination of the collector. During the experimental procedure, three different inclination angles of the solar collector were tested in order to evaluate their effect on the generation of thermosiphonic flow. The thermal performance of the collector was calculated both in thermosiphonic operation and also according to EN12975-2:2006 in order to determine the thermal performance at a flow and operation conditions specified by the standard. Finally, a series of correlations were attempted using the experimental results for the thermosiphonic operation of the collector which are the following: (i) the temperature difference of the water at the outlet and the inlet of the collector (ΔT) with solar global radiation, (ii) the water mass flow with the solar global radiation and (iii) the water mass flow with the temperature difference of the water at the outlet and the inlet of the collector. The results of the data analysis showed that the examined parameters were well correlated and also the optimum inclination angle in terms of the highest thermosiphonic flow generation was that of 45°