Engineering Science and Technology, an International Journal (Dec 2022)
Heat transfer characteristics of a periodically transient flow for turbulent wall-bounded dual jet
Abstract
The thermal characteristics and aerodynamic behaviours of an unsteady flow for a turbulent wall-bounded dual jet are computationally studied in the present paper. It is quite important to analyse thermal characteristics of such flows, as a function of independent parameters like Reynolds number. These jets are used in different industrial applications, such as, cooling of electronic devices and heat exchange systems. The capabilities of different Reynolds-Averaged Navier-Stokes (RANS) turbulence modeling approaches, such as, renormalization group k-ɛ (RNG), realizable k-ɛ, standard k-ω, and shear-stress transport k-ω (SST) models in predicting thermal performance of a turbulent dual jet are investigated. The comparison shows that among four turbulence models, the SST k-ω model provides a good agreement with the reported experimental results. The transient RANS equations have been used to simulate the complex behaviour of a turbulent dual jet. The Reynolds number (Re) is varied from 10,000 to 40,000 for a fixed offset ratio of 2 under isothermal boundary wall conditions. The results reveal that the axial position of the merge point is independent of Re and remains almost constant as Re is further increased. It is also noticed that the velocity becomes self-similar and independent of Re after a streamwise position of X = 30. The time series of U and V velocity signals unveil sinusoidal oscillations and display peak to peak amplitude difference at the far axial location. The FFT assessment of the U velocity signal displays a solo peak dominant frequency which is the same as shown by V velocity in the FFT plot corresponding to the Strouhal number of the vortex shedding phenomenon. The average Nusselt number and the average heat flux increase with Re. A correlation has been developed for the average Nusselt number and the average heat flux. These outcomes will improve the current knowledge of various engineering and industrial applications to enhance the heat transfer in different heat exchange systems, such as, electronics cooling systems.
