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Borehole Heat Exchanger
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Gunter Rockendorf – One of the best experts on this subject based on the ideXlab platform.
unglazed pvt collectors as additional Heat source in Heat pump systems with Borehole Heat ExchangerEnergy Procedia, 2012Co-Authors: Erik Bertram, Jens Glembin, Gunter RockendorfAbstract:
An unglazed photovoltaic-thermal (PVT) collector provides a double benefit in a Heat pump system compared to a conventional Heat pump system with PV and Borehole Heat Exchanger. First, the PV cells in the PVT collector are cooled, leading to lower cell temperatures and a higher PV efficiency. Second, the PVT Heat raises the temperature level of the Heat pump and the Borehole Heat Exchanger and consequently leads to a higher Heat pump system performance. In this context a system was measured with a 39 m2 unglazed PVT collector field. The impact of the solar Heat to the Heat pump is determined by TRNSYS simulations using energetic weighted temperatures for validation and to quantify the impact of the solar Heat. The investigated system revealed a temperature increase of 3 K which equals 9% lower electricity consumption. The yearly additional PV yield was determined to 4% by reference measurement of uncooled conventional PV panels. Additionally, system simulations in TRNSYS are presented.
Heat pump systems with Borehole Heat Exchanger and unglazed pvt collectorISES Solar World Congress 2011, 2011Co-Authors: Erik Bertram, Gunter Rockendorf, Martin StegmannAbstract:
In the future energy supply both efficient Heat pump systems for Heat generation and photovoltaic (PV) electricity production will play an important role. Therefore, a Heat pump system with a combined Heat source consisting of a photovoltaic-thermal (PVT) collector and a Borehole Heat Exchanger (BHE) is assumed to be a promising solution, because this particular combination provides a double benefit compared to conventional Heat pump and PV-systems. First, the PV cells in the PVT collector are cooled, leading to lower cell temperatures and a higher PV efficiency. Second, the Heat from the PVT collector raises the temperature level of the Heat pump and the Borehole Heat Exchanger. Consequently, the temperature increase of the Heat source leads to a higher Heat pump performance factor.
Björn Palm – One of the best experts on this subject based on the ideXlab platform.
transient Heat transfer in a coaxial Borehole Heat ExchangerGeothermics, 2014Co-Authors: Richard A Beier, José Acuña, Palne Mogensen, Björn PalmAbstract:
Ground-source Heat pumps often use vertical Boreholes to exchange Heat with the ground. A transient Heat transfer model has been developed for a thermal response test on a pipe-in-pipe coaxial Borehole Heat Exchanger. The analytical model calculates the vertical temperature profiles in the fluid flowing through the pipes, which are coupled to the surrounding grout and ground. The model is verified against measured vertical temperature profiles in the circulating fluid during a distributed thermal response test. The comparison with measured data indicates that the proposed model gives a more accurate estimate of the Borehole thermal resistance than the conventional analytical model that uses a mean temperature approximation. The model demonstrates how strongly the shapes of the temperature profiles are dependent on the thermal resistance of the internal pipe wall and the flow direction.
DISTRIBUTED TEMPERATURE MEASUREMENTS ON A MULTI-PIPE COAXIAL Borehole Heat Exchanger, 2012Co-Authors: José Acuña, Björn PalmAbstract:
The first experiences with a multi-pipe Borehole Heat Exchanger prototype consisting of an insulated central pipe and twelve parallel peripheral pipes are described. Secondary fluid distributed temperature measurements along the Borehole depth, being the only ones of its kind in this type of Heat Exchanger, are presented and discussed. The measurements are carried out with fiber optic cables during Heat injection into the ground, giving a detailed visualization of what happens both along the central and peripheral flow channels. The Heat exchange with the ground mainly occurs along the peripheral channels and an indication of almost no thermal short circuiting, even while having large temperature differences between the down and upwards channels, is observed.
distributed thermal response tests on a multi pipe coaxial Borehole Heat ExchangerHvac&r Research, 2011Co-Authors: José Acuña, Palne Mogensen, Björn PalmAbstract:
In a distributed thermal response test, distributed temperature measurements are taken along a Borehole Heat Exchanger during thermal response tests, allowing the determination of local ground ther …
Mehdi Maerefat – One of the best experts on this subject based on the ideXlab platform.
thermal resistance capacity model for short term Borehole Heat Exchanger simulation with non stiff ordinary differential equationsGeothermics, 2017Co-Authors: A Minaei, Mehdi MaerefatAbstract:
Abstract In the present study, a new thermal resistance capacity circuit for the Heat transfer modeling in Borehole Heat Exchanger with low computation time is developed. Generally, the thermal circuit models result in sets of ordinary differential equations which are solved numerically. The system of equations derived from the traditional thermal resistance capacity model (TRCM) are usually stiff and lead to unstable results unless for a very small time steps which can increase the computation time significantly. Meanwhile, the system of ordinary differential equations derived from the present model is non-stiff and there is no time step limitation for the stability of the results. It is shown that the present model yields accurate and stable results even for large time steps. Finally, the two-dimensional model is extended to the three-dimensional model. The results of the three-dimensional solution of the present model are in good agreement with the numerical results and experimental measurements reported in the literature.
a new analytical model for short term Borehole Heat Exchanger based on thermal resistance capacity modelEnergy and Buildings, 2017Co-Authors: A Minaei, Mehdi MaerefatAbstract:
Abstract The present study develops a new accurate and simple analytical method for modeling of Heat transfer in Borehole Heat Exchanger for short time periods. The thermal resistance and capacity circuit is used for derivation of the governing equations inside the Borehole for single U-tube and double U-tube configurations. Also, radial Heat transfer is taken into account in the ground around the Borehole. The Laplace transform is used for solving the governing equations. The effects of the fluid and grout thermal capacities are considered in the present model. Unlike the previous analytical models reported in the literature, the real geometry of the Borehole with single and double U-tube configurations is considered in the present model. The results of the present analytical model are compared with reference experimental measurements and numerical simulation results. It is found that the mean fluid temperature and the Borehole wall temperatures obtained from the present analytical method are in very good agreement with the reference numerical results.