<p>An experimental investigation was conducted to evaluate heat transfer and pressure drop characteristics in a gasketed plain-plate heat exchanger using ethylene glycol–water solutions as the process fluid. The study covers four channel gaps (0.58 mm, 0.96 mm, 1.06 mm and 1.70 mm), three fluid concentrations (50%, 70% and 100% ethylene glycol), and inlet temperatures of 50 °C, 60 °C, 70 °C and 80 °C, corresponding to Reynolds numbers of 55–1782 and Prandtl numbers of 8.4–53.5. The results demonstrate that heat transfer behaviour in plain-plate channels is strongly governed by fluid viscosity and channel geometry. Reducing the channel gap from 1.70 mm to 0.58 mm increases the heat transfer coefficient by up to 2.2 times, accompanied by a 4 to 7-fold increase in pressure drop. A crossover phenomenon is identified, where the widest channel exceeds narrower configurations at higher flow rates due to a higher flow-rate exponent. In addition, a performance plateau is observed between intermediate gap sizes (0.96–1.06 mm), indicating negligible thermal benefit within this range. The analysis shows that correlation parameters vary significantly with channel gap, reflecting changes in flow regime from laminar to transitional conditions. As a result, a single generalized dimensionless correlation is not adequate to represent all configurations. Instead, geometry-specific correlations incorporating viscosity effects and gasket thickness scaling are developed, representing the full dataset within the stated uncertainty. The per-gasket correlations achieve root-mean-square deviation < 12% and the generalised equation covers all configurations with a root-mean-square deviation of 10.56%. The central contribution of this work is the systematic demonstration that the single generalized correlation -<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(Nu=C\cdot Re^n\cdot Pr^m\)</EquationSource> </InlineEquation>, widely applied to plate heat exchangers, does not hold for plain (non-corrugated) plate channels operating with viscous fluids across a range of channel gaps. This breakdown is established independently by two diagnostics: the heat-transfer flow-rate exponent increases with channel gap (≈ 0.28 to 0.65), while the friction-factor exponent weakens with gap ( ≈ − 0.56 to − 0.20), both indicating a progressive shift from laminar toward transitional flow as the gap widens. The findings provide experimentally derived design guidance for plain plate heat exchangers handling viscous fluids and contribute data in a high-Prandtl-number regime that is underrepresented in the literature.</p>

Experimental investigation of heat transfer and pressure drop of ethylene glycol solutions in a plain-plate heat exchanger: effects of channel gap, concentration, and flow regime

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发表日期：

2026年7月25日

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Vikram Mohite

摘要

An experimental investigation was conducted to evaluate heat transfer and pressure drop characteristics in a gasketed plain-plate heat exchanger using ethylene glycol–water solutions as the process fluid. The study covers four channel gaps (0.58 mm, 0.96 mm, 1.06 mm and 1.70 mm), three fluid concentrations (50%, 70% and 100% ethylene glycol), and inlet temperatures of 50 °C, 60 °C, 70 °C and 80 °C, corresponding to Reynolds numbers of 55–1782 and Prandtl numbers of 8.4–53.5. The results demonstrate that heat transfer behaviour in plain-plate channels is strongly governed by fluid viscosity and channel geometry. Reducing the channel gap from 1.70 mm to 0.58 mm increases the heat transfer coefficient by up to 2.2 times, accompanied by a 4 to 7-fold increase in pressure drop. A crossover phenomenon is identified, where the widest channel exceeds narrower configurations at higher flow rates due to a higher flow-rate exponent. In addition, a performance plateau is observed between intermediate gap sizes (0.96–1.06 mm), indicating negligible thermal benefit within this range. The analysis shows that correlation parameters vary significantly with channel gap, reflecting changes in flow regime from laminar to transitional conditions. As a result, a single generalized dimensionless correlation is not adequate to represent all configurations. Instead, geometry-specific correlations incorporating viscosity effects and gasket thickness scaling are developed, representing the full dataset within the stated uncertainty. The per-gasket correlations achieve root-mean-square deviation < 12% and the generalised equation covers all configurations with a root-mean-square deviation of 10.56%. The central contribution of this work is the systematic demonstration that the single generalized correlation - \(Nu=C\cdot Re^n\cdot Pr^m\) , widely applied to plate heat exchangers, does not hold for plain (non-corrugated) plate channels operating with viscous fluids across a range of channel gaps. This breakdown is established independently by two diagnostics: the heat-transfer flow-rate exponent increases with channel gap (≈ 0.28 to 0.65), while the friction-factor exponent weakens with gap ( ≈ − 0.56 to − 0.20), both indicating a progressive shift from laminar toward transitional flow as the gap widens. The findings provide experimentally derived design guidance for plain plate heat exchangers handling viscous fluids and contribute data in a high-Prandtl-number regime that is underrepresented in the literature.