Shell and coil tube heat exchangers (SCTHE) have superior thermal performances and, therefore, are well-suited for space-constrained applications, but face increased pressure drop (ΔP), pumping power (PP), and friction factor (fi). These parameters are influenced by the tube side Reynolds number (Rei), the Dean number (Dei), and the curvature ratio (δ). For inverted conical coils (CC) while deriving correlation to obtain the selection of significant contributing parameters based on regression, ANOVA, and multicollinearity is not found. To address this gap, a variation in δ was done by varying the shape and cone angles (ϴ). The ϴ ranges from 90° (Straight helical coil, SHC, δ=0.14) to 0° (spiral coil, SC, δ=0.059), with intermediate angles of 70° (δ=0.083), 50° (δ=0.063), and 30°(δ=0.048) representing CC configurations. For laminar and turbulent flow regimes, experiments were conducted over a range of Rei and Dei as 3700–21,000 and 700–8000, respectively. Results indicate that ΔP increases with increasing Rei and is higher in counter-flow. For the turbulent regime (Rei =20000), PP was highest for ϴ=0° followed by ϴ=90°, and was also found to be higher by 14–27% than CCs. Additionally, fi decreases as the flow transitions from laminar to turbulent. For the turbulent regime (Rei =10000–20000), SC exhibited 23–26% higher fi than δ = 0.063, and as δ increased from 0.063 to 0.14, fi also increased. Statistical analysis, including regression and ANOVA, was performed to identify significant parameters influencing fi. After accounting for multicollinearity among parameters, it was determined that fi is a function of Dei.δ2 and correlations are developed for individual coils as: fi=a. (Dei.δ2)b, with R² values above 0.90. Also fi for inverted CC was 14–29% higher than the fi of straight tubes. CC with ϴ =30° was found to be optimum, giving higher values of overall heat transfer coefficients (Ui) and lower values of ΔP and PP. This study demonstrated the selection of optimum SCTHE on the basis of Ui, ΔP, and PP.

Experimental investigation of friction factors and correlation development for shell and conical coil heat exchangers

期刊论文
发表日期：

2025年10月3日

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Susheel Madhavrao Magar,
Bharat Trimbak Tagad,
Gaurav Gugliani

摘要

Shell and coil tube heat exchangers (SCTHE) have superior thermal performances and, therefore, are well-suited for space-constrained applications, but face increased pressure drop (ΔP), pumping power (PP), and friction factor (f_i). These parameters are influenced by the tube side Reynolds number (Re_i), the Dean number (De_i), and the curvature ratio (δ). For inverted conical coils (CC) while deriving correlation to obtain the selection of significant contributing parameters based on regression, ANOVA, and multicollinearity is not found. To address this gap, a variation in δ was done by varying the shape and cone angles (ϴ). The ϴ ranges from 90° (Straight helical coil, SHC, δ=0.14) to 0° (spiral coil, SC, δ=0.059), with intermediate angles of 70° (δ=0.083), 50° (δ=0.063), and 30°(δ=0.048) representing CC configurations. For laminar and turbulent flow regimes, experiments were conducted over a range of Re_i and De_i as 3700–21,000 and 700–8000, respectively. Results indicate that ΔP increases with increasing Re_i and is higher in counter-flow. For the turbulent regime (Re_i =20000), PP was highest for ϴ=0° followed by ϴ=90°, and was also found to be higher by 14–27% than CCs. Additionally, f_i decreases as the flow transitions from laminar to turbulent. For the turbulent regime (Re_i =10000–20000), SC exhibited 23–26% higher f_i than δ = 0.063, and as δ increased from 0.063 to 0.14, f_i also increased. Statistical analysis, including regression and ANOVA, was performed to identify significant parameters influencing f_i. After accounting for multicollinearity among parameters, it was determined that f_i is a function of De_i.δ₂ and correlations are developed for individual coils as: f_i=a. (De_i.δ₂)_b, with R² values above 0.90. Also f_i for inverted CC was 14–29% higher than the f_i of straight tubes. CC with ϴ =30° was found to be optimum, giving higher values of overall heat transfer coefficients (U_i) and lower values of ΔP and PP. This study demonstrated the selection of optimum SCTHE on the basis of U_i, ΔP, and PP.