Ktisis Cyprus University of Technologyhttps://ktisis.cut.ac.cyThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sun, 24 Jan 2021 05:32:28 GMT2021-01-24T05:32:28Z5071Thermal properties of rocks and compilation of geothermal maps of Cyprushttps://ktisis.cut.ac.cy/handle/10488/13377Title: Thermal properties of rocks and compilation of geothermal maps of Cyprus
Authors: Iosif-Stylianou, Iosifina; Florides, Georgios A.; Tassou, Savvas A.; Tsiolakis, Efthymios; Messaritis, Vassilios; Kalogirou, Soteris A.; Christodoulides, Paul
Thu, 01 Jun 2017 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/133772017-06-01T00:00:00ZGeo-Thermal Suitability Mapshttps://ktisis.cut.ac.cy/handle/10488/13371Title: Geo-Thermal Suitability Maps
Authors: Iosif-Stylianou, Iosifina; Florides, Georgios A.; Tassou, Savvas; Tsiolakis, Efthymios; Christodoulides, Paul
Tue, 01 May 2018 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/133712018-05-01T00:00:00ZGeothermal maps of the Greater Lefkosia Area - Cyprushttps://ktisis.cut.ac.cy/handle/10488/13378Title: Geothermal maps of the Greater Lefkosia Area - Cyprus
Authors: Iosif-Stylianou, Iosifina; Florides, Georgios A.; Tassou, Savvas A.; Tsiolakis, Efthymios; Christodoulides, Paul
Mon, 01 May 2017 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/133782017-05-01T00:00:00ZUsing artificial neural networks for the construction of contour maps of thermal conductivityhttps://ktisis.cut.ac.cy/handle/10488/3989Title: Using artificial neural networks for the construction of contour maps of thermal conductivity
Authors: Kalogirou, Soteris A.; Christodoulides, Paul; Florides, Georgios A.; Pouloupatis, Panayiotis; Iosif-Stylianou, Iosifina
Abstract: In this paper a neural network is used for the construction of a contour map. The particular case of the thermal conductivity map of the ground of the island of Cyprus is considered, with archived data at a number of boreholes throughout Cyprus being used for training a suitable artificial neural network. The data were randomly divided into a training and a validation dataset for a multiple hidden layer feed-forward architecture. The correlation coefficient obtained between the predicted and the training dataset is 0.966, indicating an accurate mapping of the data, while the validation (unknown) dataset exhibits an also satisfactory correlation coefficient of 0.955. The dataset was broadened by embedding the patterns used for the validation into the training dataset with the correlation coefficient equalling a higher 0.972. The available input parameters were then recorded for each grid point on a detailed topographic map of Cyprus, whereby the neural network was used to predict the thermal conductivity at each point. The coordinates and the estimated conductivity were then used as input to a specialized contour drawing software in order to draw the geothermal contour map.
Thu, 01 May 2014 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/39892014-05-01T00:00:00ZModeling and assessment of the efficiency of horizontal and vertical ground heat exchangershttps://ktisis.cut.ac.cy/handle/10488/3360Title: Modeling and assessment of the efficiency of horizontal and vertical ground heat exchangers
Authors: Florides, Georgios A.; Iosif-Stylianou, Iosifina; Tassou, Savvas A.; Zomeni, Zomenia; Tsiolakis, Efthymios; Pouloupatis, Panayiotis; Kalogirou, Soteris A.; Christodoulides, Paul; Messaritis, Vassilios; Panagiotou, Gregoris; Theofanous, Elisavet
Abstract: This paper describes the mathematical modeling of vertical and horizontal GHEs (ground heat exchangers) and compares their efficiency. The model used calculates the heat flow in the fluid, tubes, grout and ground. The vertical U-tube GHE is represented by two 100 m lines, embedded in four different types of ground with an additional bottom base. The horizontal GHE consists of four 50 m tube lines embedded in three ground layers. The initial ground temperature for all cases examined matches real data acquired in June at a location in Cyprus and the simulation results for the vertical GHE are validated using measured data showing very good agreement. Further simulations with the vertical GHE show that when the initial ground temperature rises, the mean temperature of the GHE fluid increases proportionally. Comparisons between horizontal and vertical GHEs reveal that under the same operating conditions and center-to-center distances of the tubes, the vertical GHE keeps a much lower mean temperature. Simulations for a horizontal GHE, for a 50-h of continuous operation period and 24 °C initial ground temperature, show that the mean fluid temperature can remain lower than that of the vertical GHE if the center-to-center distance of the tubes increases to 1 m.
Sun, 01 Sep 2013 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/33602013-09-01T00:00:00ZModeling of vertical ground heat exchangers in the presence of groundwater flow and underground temperature gradienthttps://ktisis.cut.ac.cy/handle/10488/13598Title: Modeling of vertical ground heat exchangers in the presence of groundwater flow and underground temperature gradient
Authors: Iosif-Stylianou, Iosifina; Tassou, Savvas A.; Christodoulides, Paul; Aresti, Lazaros; Florides, Georgios A.
Abstract: The paper focuses on the methodology for modeling the thermal response of vertical Ground Heat Exchangers (GHEs), when imposing underground water flow and a temperature gradient on the numerical model to represent the temperature of the depth profile. Four underground layers with different properties were studied, in order to identify their contribution in the total response of the GHE. In more detail, vertical GHEs in water saturated and dry soils, with or without water flow, are modeled with the equations that govern the heat transfer being presented. The numerical solution of the equations is based on the Finite Element Method (FEM) with boundary values. The model is validated with actual data of a Thermal Response Test (TRT) carried out in Lakatameia, Cyprus. Using the validated model, the heat injection rate of a GHE is investigated by determining the effect of the (a) summer and winter mode of operation, (b) underground temperature variation in depths smaller than 7 m due to daily and seasonal changes, (c) borehole radius, (d) borehole grout properties, (e) U-tube diameter, (f) U-tube leg and borehole centers distance, and (g) groundwater flow velocity.
Sat, 01 Jun 2019 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/135982019-06-01T00:00:00ZBorehole Ground Heat Exchangers and The Flow of Underground Waterhttps://ktisis.cut.ac.cy/handle/10488/13353Title: Borehole Ground Heat Exchangers and The Flow of Underground Water
Authors: Iosif-Stylianou, Iosifina; Christodoulides, Paul; Aresti, Lazaros; Tassou, Savvas A.; Florides, Georgios A.
Abstract: Vertical Ground Heat Exchangers (GHEs) in boreholes are a major form of Geothermal Energy applications.
When water flowing underground past the borehole the heat injection rates of the GHE are subject to change. Here, we
construct a mathematical model for such regimes. Then, based on the Finite Element Method we construct a corresponding
computational model, which is validated with experimental data of a Thermal Response Test carried out in Lakatameia,
Cyprus. Finally, using the validated model, the thermal behavior of borehole GHEs is investigated by studying the effect of
the (a) BH radius, (b) U-tube diameter, (c) U-tube leg and BH centers distance, (d) grout thermal conductivity and (e)
underground water velocity.
Description: Presented at 143th ISER International conference, 2018, 24-25 July, Melbourne, Australia
Sat, 01 Sep 2018 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/133532018-09-01T00:00:00Z