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Geothermal Energy

Science – Society – Technology

Fig. 4 | Geothermal Energy

Fig. 4

From: Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

Fig. 4

Exergetic results (a Influence of \({\text{SDR}}\) & ground resistance, b Influence of temperature difference, c Exergetic optimum, d Exergetic results) for laminar and turbulent flows a Change of optimal inner to outer pipe ratio (\({c_{\text{opt}}}\)) compared to hydraulic results over Standard Dimension Ratio (\({\text{SDR}}\)) and ground resistance (\({R_g}\)). b Change of optimal inner to outer pipe ratio (\({c_{\text{opt}}}\)) over ground resistance (\({R_g}\)) and temperature difference (\({\Delta T}\)). c optimal inner to outer pipe ratio (\({c_{\text{opt}}}\)) over Standard Dimension Ratio (\({\text{SDR}}\)) and ground resistance (\({R_g}\)) for fixed Reynolds numbers and fixed mass flow rates (\(\dot{m}\)). d Exemplary distribution of objective function over the range of \({c}\) and determined optimum \({c_{\text{opt}}}\) 

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