Abstract
Nowadays, applications of turbulent fluid flow in removing high heat flux in rib-roughened narrow channels are drawing much interest. In this work, an improved version of the κ-ε turbulence model is proposed for better prediction of thermal–hydraulic characteristics of flow inside rib-roughened (pitch-to-rib height (p/k) ratio = 10 and 20) narrow channels (channel height, H = 1.2 mm and 3.2 mm). For this, the four turbulence model parameters, Cμ, Cε1, Cε2, and σk, are calibrated. These parameters are adjustable empirical constants provided for controlling the accuracy of the turbulence model results when needed. The simulated data are used to develop correlations between the relative errors in predicting the friction factor (f), Nusselt number (Nu), and the model parameters using a multivariate nonlinear regression method. These correlations are used to optimize the errors using genetic algorithm. Results reveal that the calibrated parameters are not the same for all the narrow channel configurations. After calibration, the overall predictive improvements are up to 35.83% and 27.30% for p/k = 10 and p/k = 20 respectively when H = 1.2 mm. Also, up to 15.48% and 18.05% improvements are obtained for p/k = 10 and p/k = 20 respectively when H = 3.2 mm. The role of the two parameters Cε1 and Cε2 are found to be of primary importance. Furthermore, three types of nanofluids i.e. Al2O3-water, CuO-water, and TiO2-water are studied using the calibrated model to check the potentiality of heat transfer enhancement. Among them, CuO-water nanofluid is predicted to have around 1.32 times higher value of Nu than pure water for the same narrow channel configuration.Article Highlightsκ-ε turbulence model is calibrated for rib-roughened narrow rectangular channels using genetic algorithm.Cε1 and Cε2 are the most influential parameters on the performance of the model inside rib-roughened narrow channel.Suggested calibration process is more effective for channel height of 1.2 mm than 3.2 mm.
Highlights
Micro-channel and mini-channel heat sinks are the core components of modern heat removal technology
Multiphysics, a commercially available Computational Fluid Dynamics (CFD) tool. 75 combinations of the turbulence model parameters were used in the data generation stage and both ∈f and ∈Nu were computed for each combination
The data were the most scattered for σk indicating that it might have the weakest relationship with the predictive accuracy amongst the four turbulence model parameters
Summary
Micro-channel and mini-channel heat sinks are the core components of modern heat removal technology. The micro-channel and mini-channel heat sinks have their surfaces roughened with ribs ( called turbulence promoters) of various shapes and sizes. Micro-channel or mini-channel heat sink with a rib-roughened surface ensures better heat transfer performances with the expenses of pressure drop, it is difficult to accurately predict the fluid flow and heat transfer mechanisms. Heat transfer enhancement in micro/mini-channels with rib-roughened surfaces in the turbulent flow regime creates a high pressure drop. Islam et al [3] conducted a similar study on rectangular narrow channels with square microribs He later extended the work to analyze the influence of turbulence flow structure on the enhancement of heat transfer in those channels [4, 5]. Ma et al [9] performed a comparative study with steam and air for convective heat transfer performance inside a ribroughened channel
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
