Comparative Study of Laminar and Turbulent Heat Transfer in Microchannels

Abstract

This study investigated the heat transfer and fluid flow characteristics of laminar and turbulent regimes in microchannels using a combined experimental and numerical approach. The objective of the study was to evaluate the influence of Reynolds number on thermal and hydraulic performance and to assess the applicability of conventional heat transfer correlations at microscale dimensions. An experimental setup consisting of a heated microchannel test section, controlled flow delivery system, and precision temperature and pressure measurement instruments was employed to obtain data for a wide range of Reynolds numbers covering both laminar and turbulent flow regimes. Complementary computational fluid dynamics simulations were conducted using appropriate governing equations and boundary conditions to predict velocity, temperature, and pressure fields within the microchannel. The results showed that the Nusselt number increased with Reynolds number in both flow regimes, with turbulent flow exhibiting significantly higher heat transfer rates than laminar flow. However, the turbulent regime was also associated with substantially higher friction factors and pressure drops, indicating increased pumping power requirements. The experimental and numerical results demonstrated close agreement, validating the reliability of the numerical model. The study further revealed that microscale effects such as entrance length influence and enhanced convection caused deviations from classical theoretical predictions developed for macroscale channels. Overall, the findings established that optimal microchannel thermal performance was achieved at moderate turbulent Reynolds numbers, where heat transfer enhancement outweighed hydraulic penalties. The study provided valuable insights for the design and optimisation of microchannel heat exchangers used in electronics cooling, energy systems, and other high heat flux applications.