Analysis and Comparison of Some Low-Temperature Heat Sources for Heat Pumps

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.

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

“…Thanks to the laboratory results obtained from these studies, it is possible to determine the optimal pattern of behavior for entire vertical closed systems [33]. Neuberger and Adamovský [34] presented the results of operational monitoring, analysis and comparison of temperatures, power, and energy of antifreeze in the most commonly used low-temperature heat sources. The results of the verification showed that it was not possible to unequivocally define the most advantageous low-temperature heat source that meets the requirements for the efficiency of heat pump operation.…”

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.

“…Neuberger and Adamovsky [7,8] conducted measurements of the ground temperature near the slinky-coil and straight pipe exchangers. The research was conducted both during the heating season and for the thermal regeneration of the ground.…”

Section: Introductionmentioning

confidence: 99%

Modeling the Temperature Field in the Ground with an Installed Slinky-Coil Heat Exchanger

Gwadera

Kupiec

2021

In order to find the temperature field in the ground with a heat exchanger, it is necessary to determine temperature responses of the ground caused by heat sources and the influence of the environment. To determine the latter, a new model of heat transfer in the ground under natural conditions was developed. The heat flux of the evaporation of moisture from the ground was described by the relationship taking into account the annual amount of rainfall. The analytical solution for the equations of this model is presented. Under the conditions for which the calculations were performed, the following data were obtained: the average ground surface temperature Tsm = 10.67 °C, the ground surface temperature amplitude As = 13.88 K, and the phase angle Ps = 0.202 rad. This method makes it possible to easily determine the undisturbed ground temperature at any depth and at any time. This solution was used to find the temperature field in the ground with an installed slinky-coil heat exchanger that consisted of 63 coils. The results of calculations according to the presented model were compared with the results of measurements from the literature. The 3D model for the ground with an installed heat exchanger enables the analysis of the influence of miscellaneous parameters of the process of extracting or supplying heat from/to the ground on its temperature field.