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    Thermal hydraulic performance evaluation of an additively manufactured minichannel heat exchanger using a combined experimental and multivariate regression model-based approach
    (Elsevier, 2025-09) Aneesh, A.M.
    This study investigates the thermal–hydraulic performance of an additively manufactured heat exchanger (AMHE) operating in a nitrogen-nitrogen counter flow open loop. The AMHE, consisting of ten semicircular mini channels with diverging inlets and converging outlet headers for both hot and cold fluids, was 3D printed using the Selective Laser Melting (SLM) technique with AlSi10Mg. The rough surface of its internal channels is characterized by using a cut sample with Field Emission Scanning Electron Microscopy (FESEM) images and a surface profilometer. An open-loop experimental test facility was developed to evaluate AMHE performance. Experiments are conducted by varying balanced mass flow rates (1.11 to 4.44 kg/h) and hot inlet temperatures (324.9 to 353.0 K). Balanced mass flow rate, temperature, and pressure measurements were recorded at steady state, and heat transfer rates and channel pressure drops were calculated. AMHE achieved a maximum power density of about 125.4 kW/m3 at a low log mean temperature difference (LMTD) of 6.5 K in a counter-flow arrangement. The experimental results were compared with standard ∊-NTU correlations available in the literature and showed agreement within 1 %. We noted that the effectiveness and entropy generation increase, and axial conduction decreases with an increase in balanced flow rates. A multivariable regression model was developed to predict the experimentally obtained heat transfer rate and pressure drops within a 2 % error limit and used to predict the effect of various operating conditions. Parametric results showed that increasing the balanced flow rate and hot inlet temperature enhanced the heat transfer rate by a factor of about 5, with the corresponding pressure drop rising by up to a factor of 10. This novel combined experimental and multivariable regression approach provides practical predictive correlations for gas-to-gas mini-channel heat exchangers, compensates for input variations, and enables reliable performance estimation under varied operating conditions, offering a valuable contribution for future design and optimization.
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    Thermal-hydraulic characteristics and performance of 3D straight channel based printed circuit heat exchanger
    (Elsevier, 2016-04) Aneesh, A.M.
    CFD study is done to propose an efficient PCHE (Printed Circuit Heat Exchanger) model; used as a recuperator in International Thermonuclear Experimental Reactor (ITER). 3D steady-state conjugate heat-transfer simulations are done with helium as a working fluid and alloy 617 as the solid substrate. Effect of variation of thermo-physical properties, operating conditions and three different design modifications are studied. Thermal hydraulic performance is found better for single as compared to double banking and is the same for aligned as compared to the staggered arrangement of the hot and cold channels. PCHE models with hemispherical dimples are found to give better thermal hydraulic performance. The performance is presented for the variation of the heat transfer density (for a PCHE model) and the pressure drop (in the hot and cold channel). Various types of flow patterns are presented to analyze the thermal-hydraulic characteristics − leading to the heat transfer enhancement by the dimples.
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    Thermal-hydraulic characteristics and performance of 3D wavy channel based printed circuit heat exchanger
    (Elsevier, 2015-08) Aneesh, A.M.
    CFD study is done here to propose an efficient PCHE (Printed Circuit Heat Exchanger) model; used as a recuperator in International Thermonuclear Experimental Reactor (ITER). 3D steady state conjugate heat-transfer numerical simulations are done; considering the variation of thermo-physical properties as a function of temperature. Helium is used as a working fluid and alloy 617 as solid substrate. The study is done for various angle of bend (θ = 0°(straight), 5°, 10° and 15°) and Reynolds number (Re = 350, 700, 1400 and 2100). Various types of flow patterns, within one wavy-section, are presented to analyze thermal-hydraulic characteristics. Thermal hydraulic performance parameters are presented for the various wavy-sections as well as within a section; and for the complete PCHE model. Heat transfer enhancement as compared to pressure penalty is higher for the wavy channel; and increases with increasing Re and θ. Wavy as compared to plane channel based PCHE is demonstrated here to give better thermal-hydraulic performance. A detailed characteristics as well as performance-parameters for thermal hydraulics in a 3D wavy channel based PCHE model − not found in the literature − is presented here.