TY  - JOUR
A1  - Blanke, Tobias
A1  - Hagenkamp, Markus
A1  - Döring, Bernd
A1  - Göttsche, Joachim
A1  - Reger, Vitali
A1  - Kuhnhenne, Markus
T1  - Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates
JF  - Geothermal Energy
N2  - Previous studies optimized the dimensions of coaxial heat exchangers using constant mass fow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar fow types. In contrast, in this study, fow conditions in the circular ring are kept constant (a set of fxed Reynolds numbers) during optimization. This approach ensures fxed fow conditions and prevents inappropriately high or low mass fow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic efort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass fow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefcients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy diference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy fux and hydraulic efort. The Reynolds number in the circular ring is instead of the mass fow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar fow and 60% for turbulent fow scenarios. Net-exergetic optimization shows a predominant infuence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the fow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.
Y1  - 2021
U6  - https://doi.org/10.1186/s40517-021-00201-3
SN  - 2195-9706
N1  - Corresponding author: Tobias Blanke
VL  - 9
IS  - Article number: 19
PB  - Springer
CY  - Berlin
ER  - 
TY  - CHAP
A1  - Atmane, Ilias
A1  - Hirech, Kamal
A1  - Kassmi, K.
A1  - Mahdi, Zahra
A1  - Alexopoulos, Spiros
A1  - Schwarzer, Klemens
A1  - Chayeb, H.
A1  - Bachiri, N.
ED  - Omrane, Amina
ED  - Kassmi, Khalil
ED  - Akram, Muhammad Wasim
ED  - Khanna, Ashish
ED  - Mostafiz, Imtiaz
T1  - Design and realization of a pilot solar desalination plant in Douar El Hamri in the province of Berkane (Morocco)
T2  - Sustainable entrepreneurship, renewable energy-based projects, and digitalization
N2  - Producing fresh water from saline water has become one of the most difficult challenges to overcome especially with the high demand and shortage of fresh water. In this context, as part of a collaboration with Germany, the authors propose a design and implementation of a pilot multi-stage solar desalination system (MSD), remotely controlled, at Douar Al Hamri in the rural town of Boughriba in the province of Berkane, Morocco. More specifically, they present their contribution on the remote control and supervision system, which makes the functioning of the MSD system reliable and guarantees the production of drinking water for the population of Douar. The results obtained show that the electronic cards and computer communication software implemented allow the acquisition of all electrical (currents, voltages, powers, yields), thermal (temperatures of each stage), and meteorological (irradiance and ambient temperature), remote control and maintenance (switching on, off, data transfer). By comparing with the literature carried out in the field of solar energy, the authors conclude that the MSD and electronic desalination systems realized during this work represent a contribution in terms of the reliability and durability of providing drinking water in rural and urban areas.
Y1  - 2020
SN  - 9781000292541 (E-Book)
SN  - 9781003097921 (E-Book)
SN  - 9780367468378 (Hardcover)
PB  - CRC Press
CY  - Boca Raton, Fa.
ER  - 
TY  - JOUR
A1  - Alexopoulos, Spiros
A1  - Hoffschmidt, Bernhard
T1  - Advances in solar tower technology
JF  - Wiley interdisciplinary reviews : Energy and Environment : WIREs
Y1  - 2017
U6  - https://doi.org/10.1002/wene.217
SN  - 2041-840X
VL  - 6
IS  - 1
SP  - 1
EP  - 19
PB  - Wiley
CY  - Weinheim
ER  -