Plenary Lecture

Mathematical Method for Estimation the Temperature Field Changes by Vertical Heat Exchangers during Real Time Exploitation of Ground Source Heat Pump Systems

Professor Ioan David
Politehnica University Timisoara
Departament of Hydrotechnics
Romania
&
University of Applied Sciences
Facgbereich Bauwesen, Südanlage, Giessen
Germany
E-mail: Ioan.David@gmx.net

Abstract: In actually context of the general need to increase the share of alternative energy sources, the near surface geothermal energy i.e. the natural energy reservoir of the earth (up to 200-300m) which can be exploited to heating or cooling using ground source heat pump (GSHP) systems, have an important place. The performance of such an system depends basically on the temperature difference between heat source which is the natural ground outside of the heat exchangers borehole and the refrigerant which is recycled in the heat exchangers through the heat pump. Extraction of earth heat by heat pump leads to changes in initial temperature T0 from the outer wall of the heat exchanger borehole where the temperature will be namely TB< T0 in case of heating systems, and TB> T0 in case of cooling systems. An important characteristic of the real time exploitation of GSHP systems is its intermittent work in daily cycles (i.e. working time of tWh ours followed of a break time of tBh ours)which is integrated in yearly cycles (i.e. tWm working months in year with daily cycles followed of a break time of tBm months). The temperature change can reaches even 8 -150C during a daily cycle and several 0C during long time exploitation (i.e. several decades). These temperature changes can have a negative influence on the system performance directly and due to interference effects between the heat exchanger boreholes. Additionally the changed average temperature in a more or less extended area of the GSHP system during long time exploitation can move through transported by groundwater and so can arise a form of heat pollution of the ground.
In the present paper mathematical methods and formulas are proposed for estimating the evolution of temperature field changes on the borehole wall and in the neighbourhood area of the GSHP system during its real time exploitation. In opposite to the numerical modeling which is vary laborious for parameter analysis and need large running time, especially by long time exploitation of GSHP systems, the proposed methods, based on analytical solutions of the heat transfer equation have the advantage of an rapid analysis of the influence of different geometrical and physical parameters of the heat exchanger boreholes in interaction with the underground environment where they are located.

Brief Biography of the Speaker: Prof. Ioan DAVID, graduated at the University "Politehnica" of Timisoara-Romania in Civil Engineering (1964) and graduated at the Vest University Timisoara in Mathematics (1972). In 1973 he obtains a PhD (i.e. Dr. Eng) in Theoretical and Applied Fluid mechanics at the “Politehnica” University of Timisoara. In 1976 become "Alexander von Humbold" scientific postdoctoral fellow at the Technical University Darmstadt, Germany. In 1990 becomes full professor for Hydraulic and Numerical Methods in civil engineering and PhD scientific coordinator at the “Politehnica” University of Timisoara. From 1993 till 2005 professor for Groundwater Modelling and Numerical Methods in Fluid Mechanics at the Technical University Darmstadt, Germany.
http://www.iib.tu-darmstadt.de/mitarbeiter_iib/mitarbeiter_28.de.jsp
From 2006 professor at the “Politehnica” University in Timisoara and also teaching as visiting professor at the University of Applied Science Giessen, Germany in the same subjects and Renewable Energies.
Prof. David is author of about 200 Papers published in Proceedings of International Conferences and Journals, 16 books and 3 patents in the field of Mathematical Modelling in Water and Environmental Engineering. Examples of books published in Germany: Groundwater Hydraulic (Grunwasserhydraulik), Vieweg-Wiesbaden, 1998; Mathematical-Numerical Modelling of Technical Sytems.(Mathematisch Numerische Modellierung technischer Systeme), Couvillier Verlag Göttuingen, 2005.
http://www.google.de/search?hl=de&tbo=p&tbm=bks&q=inauthor:%22Ioan+David%22
He is member of several professional organizations/associations:
• Research Group “Computational Engineering”, Technical University of Darmstadt, Germany, http://www.rc.ce.tu-darmstadt.de/forschungszentrum_ce_rc/mitglieder_rc/mitarbeiter_details_rc_8903.de.jsp
• Consulting Engineer in Germany, http://www.ingkh.de/index.php?id=176&nr=63709;
• Hungarian Academy of Sciences (MTA - external corporation member); http://www.mta.hu/index.php?id=2800&LANG=h&TID=101138&cHash=aca7122ff9
• Editor in Chief of the Scientific Bulletin of "Politehnica" University of Timisoara, Transactions on Hydrotechnics; http://buletinulstiintific.hidro.upt.ro/contact.htm, • Editorial Board of the Romanian National Journal “HIDROTEHNICA”, Bucharest;
• American Romanian Academy of Arts and Sciences (ARA), vice president (2005-2009), general secretary ARA 2009-. http://www.meca.polymtl.ca/ion/ARA-AS/executive.htm
• General Association of the Engineers in Romania (AGIR);
Professionally Distinctions: Award for Scientific Research and Excellence in Academic Lectureship, Romanian Ministry of Education and Research; Diploma awarded by the German Foundation "Alexander von Humbold"; Academic title Honorary Professor of the Technical University of Darmstadt (Germany)(1999). Technical skills and competences: Implementation and solution of many planning and research projects at national and international level, using advanced mathematical and numerical modeling in some fields of the water and environmental engineering (e.g. Groundwater flow and pollutant transport, Open channel and river hydraulic, Complex hydro-technical plants, heat transfer modeling by geothermal energy exploitation systems etc.). Recent Projects: - “Establishing measures to rehabilitate the polluted groundwater altered du to landfill in collaboration with Grontmij Nederland, Dutch consultancy company (Water, civil engineering), Dutch Ministry of Economic Affairs (EVD, 2007-2008);
- “Integrated modelling of the sustainability of geothermal system” in the framework of Social Renewing Operative Programme in Hungary (TÁMOP-4.2.2/08/1): 2010-2011, innovative research teams from basic research to applied research (Hungary, Italy, New Zeeland and Romania): http://www.georen.unideb.hu/media/document/raport-ii-p1-david-transmis.pdf
-“Development of knowledge centres for life-long learning by involving of specialists and decision makers in flood risk management using advanced Hydroinformatics tools”, as Coordinator of an International EU Project -LEONARDO DA VINCI Transfer of Innovation (2012-2013), Project partnership: Romania, Hungary and DHI enterprise, Czech Republic