A new analytical model for short vertical ground heat exchangers with Neumann and Robin boundary conditions on ground surface

This research was carried out to compare selected forecasting methods, such as the following: Artificial Neural Networks (ANNs), Classification and Regression Trees (CARTs), Chi-squared Automatic Interaction Detector (CHAID), Fuzzy Logic Toolbox (FUZZY), Multivariant Adaptive Regression Splines (MARSs), Regression Trees (RTs), Rough Set Theory (RST), and Support Regression Trees (SRTs), in the context of determining the temperature of brine from vertical ground heat exchangers used by a heat pump heating system. The subject of the analysis was a public building located in Poland, in a temperate continental climate zone. The results of this study indicate that the models based on Rough Set Theory (RST) and Artificial Neural Networks (ANNs) achieved the highest accuracy in predicting brine temperature, with the choice of the preferred method depending on the input variables used for modeling. Using three independent variables (mean outdoor air temperature, month of the heating season, mean solar irradiance), Rough Set Theory (RST) was one of the best models, for which the evaluation rates were as follows: CV RMSE 21.6%, MAE 0.3 °C, MAPE 14.3%, MBE 3.1%, and R2 0.96. By including an additional variable (brine flow rate), Artificial Neural Networks (ANNs) achieved the most accurate predictions. They had the following evaluation rates: CV RMSE 4.6%, MAE 0.05 °C, MAPE 1.7%, MBE 0.4%, and R2 0.99.

Section: Introductionmentioning

confidence: 99%

Comparative Analysis of Methods for Predicting Brine Temperature in Vertical Ground Heat Exchanger—A Case Study

Piotrowska-Woroniak,

Nęcka,

Szul

et al. 2024

“…Therefore, it is advantageous to calculate the lower parameters of the heat source as accurately as possible. There are many attempts to solve this problem in an analytical way and with the help of computer simulations [12][13][14][15][16][17][18][19][20][21][22][23][24], but so far there is no universal formula. Real measurement results are required for calculations and simulations.…”

Section: Introductionmentioning

confidence: 99%

Determination of the Selected Wells Operational Power with Borehole Heat Exchangers Operating in Real Conditions, Based on Experimental Tests

Piotrowska-Woroniak

2021

On the basis of experimental studies, the operational power of four borehole heat exchangers (BHE) under real conditions was determined. The research was carried out in 2018–2019. The theoretical power of the BHE was verified with its operating power. The amount of thermal energy absorbed from the ground by individual BHEs, the operating temperatures obtained at the inlet and outlet of the exchanger, the annual brine flow rate, and the average operating power of the tested wells in two heating seasons were compared and analyzed. Both in 2018 and 2019, none of the examined exchangers achieved an average unit capacity of a well. The aim of the work is to verify the specific ground thermal efficiency indicators adopted for the design of the lower heat source, determined using the computational method and the TRT test with data obtained on the basis of experimental tests. The differences between the results of the tests of the operating parameters of the analyzed BHEs were shown. The data obtained in real conditions is valuable in the research and development of the BHE system.

“…Therefore, it is preferable to calculate the lower parameters of the heat source as accurately as possible. There are many attempts to solve this problem analytically and with the help of computer simulations [37][38][39][40][41][42][43][44][45][46][47][48][49], but so far there is no universal formula. Real measurement results are required for calculations and simulations.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Ground Regeneration around Borehole Heat Exchangers between Heating Seasons in Cold Climates: A Case Study in Bialystok (NE, Poland)

Piotrowska-Woroniak

2021

Based on the experimental studies, the process of ground regeneration around the borehole loaded with brine-water heat pumps working exclusively for heating purposes in the period of four consecutive heating seasons in a cold climate was presented. The research was conducted in north-eastern Poland. The aim of the work is to verify the phenomenon of thermal ground regeneration in the period between heating seasons on the basis of the recorded data and to check whether the ground is able to regenerate itself and at what rate. It was noticed that the ground does not fully regenerate, especially during heating seasons with lower temperatures. In the analyzed period, from 22 September 2016 to 12 October 2020, the ground probably cooled irreversibly by 1.5 °C. In order to illustrate and evaluate the speed of changes in the ground, the one’s profile with an undisturbed temperature field was presented for each month of the year. The presented results can be a very important source of information for the analysis of geothermal conditions occurring in the ground. They can be used to verify mathematical models and conduct long-term simulations that allow us to see the complexity of the processes taking place in the ground.