Thermal Behavior Investigation and Design Improvement of Shell and Tube Heat Exchangers

Shell and tube heat exchangers (STHE) are widely employed in critical industrial applications such as boilers, oil coolers, condensers, pre-heaters, process industries, and refrigeration and air conditioning systems. Their structural robustness and moderate form factor make them particularly suitable for high-pressure operations. The present study aims to experimentally investigate, validate, and propose design optimization strategies for an STHE fabricated from acrylic material, incorporating seven stainless steel tubes and two baffles. Hot fluid was circulated through the tube side while cold fluid passed through the shell side. Four K-type thermocouples were installed to measure the inlet and outlet temperatures of the hot and cold-water streams. The experimental investigation was performed under different combinations of hot and cold-water flow rates while maintaining various hot water inlet temperature conditions. A commercial CFD code was subsequently used to analyze the thermal and hydraulic flow behavior within the heat exchanger. The CFD methodology was validated against experimental results, confirming satisfactory agreement. Turbulent flow was observed consistently on the tube side, while the shell side exhibited predominantly laminar flow except at extreme hot water inlet temperatures. Accordingly, the transition k-kl-omega model was applied for transitional cases, and the Realizable k-epsilon model with non-equilibrium wall function was adopted for turbulent conditions. Analysis of temperature and velocity profiles revealed that nearly two-thirds of the shell-side fluid bypasses the tube surfaces due to biased flow, leading to reduced heat transfer efficiency and elevated pressure losses. To address this, the two baffles were rotated in opposing directions to enhance fluid circulation and improve tube surface contact. Multiple baffle configurations were simulated using CFD, and results are presented in terms of heat transfer enhancement and pressure drop characteristics.