Investigated thermal properties of different grouting materials used in underground thermal energy storage

ABSTRACTMSc THESISINVESTIGATED THERMAL PROPERTIES OF DIFFERENTGROUTING MATERIALS USED IN UNDERGROUNDTHERMAL ENERGY STORAGEMetin Özer YILMAZDEPARTMENT OF CHEMISTRY INSTITUTE OFNATURAL AND APPLIED SCIENCES UNIVERSITY OFÇUKUROVASupervisor : Prof. Dr. Halime Ö. PAKSOYYear : 2005, Pages : 64Jury : Prof. Dr. Halime Ö. PAKSOYProf. Dr. Serdar ÖZTEKİNAssoc. Prof. Dr. Sultan GİRAYGrouting or back-fill materials are used to seal the annulus between theborehole and heat exchanger loops in GSHP and UTES systems. Designing groundheat exhangers for these systems is dependent on thermal conductivity of the groutingand thermal resistance (Rb) of the borehole system. In this study, different groutingmaterials were tested in the experimental well model in the laboratory. In theexperiments, the heat carrier fluid was circulated in U-pipe with different flowrate(l/s). Outlet (Two) and inlet (Twi) temperatures in the U-pipe were measured at steady-state conditions. Temperatures were also measured in the borehole, in U-pipe and outof casing in the surrounding formation with thermocouples. The measurements weretaken at regular intervals of 10 minutes. The duration of experiment was 25 hours.The thermal resistance and thermal conductivities of the bazalt grouting weredetermined using temperature measurements. Thermal resistance of borehole valueswere ranging from 0,012-0,576 (K/W) and thermal conductivity of system valueswere found 0,2-8,22 (W/mK). The effect of using PCM as grouting for the purpose ofshort term utilization of Borehole Thermal Energy Storage system were studied.Key Words: Underground Thermal Energy Storage, Borehole of Grouting Material,Phase Change Material (PCM), Thermal Conductivity, Thermal ResistanceII