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Table 3 Overview of modified parameters and variation range for thermal calculations

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

Parameters Units Reference case (st.) Range/variation Abbreviations
\({r}_{{i}}\) [m] [0.01:0.99]  
\({\text{SDR}}\) \([-]\) 11 6  
41  
flow type \([-]\) Turbulent (turb.) Laminar  
Turb. r. r. (rough regime)  
\({\lambda }\) [W/(m K)] Plastic/steel Steel/plastic \(\lambda _{\text{switch}}\)
Steel / steel \(\lambda _{\text{steel}}\)
(Inner/outer pipe) Plastic / plastic \(\lambda _{\text{plast}}\)
\({r_a}\) [mm] 75 39 \(r_{a,\min}\)
240 \(r_{a,\max}\)
\({r_o}\) [mm] 85 45 \(r_{o,\min}\)
250 \(r_{o,\max}\)
\({L}\) [m] 20 5 \(L_{\min}\)
100 \(L_{\max}\)
\({Re}\) \([-]\) 10000 1000 \(Re_{c,\text{lam}}\)
4000 \(Re_{c,\min}\)
100000 \(Re_{c,\max}\)