Department of Mechanical Engineering, DIT University, Dehradun, Uttarakhand (U.K), India
Department of Mechanical Engineering, DIT University, Dehradun, Uttarakhand, India
J. S. Saini
Mechanical and Industrial Engineering Department, IIT, Roorkee, Uttarakhand-247667, India; Department of Mechanical Engineering, DIT University, Dehradun, U.K, India
This paper presents the experimental study on heat transfer and friction factor in a rectangular section air heater duct having 45° V-up baffle blocks with staggered racetrack-shaped perforations. The air heater duct is subjected to a constant heat flux at one wall with turbulent airflow beneath the heated surface. The parameters affecting the duct's performance include the relative roughness height (e/H), relative pitch (p/e), and flow Reynolds number (Re). Besides the study of parameters influence on Nusselt number (Nu), friction factor (ƒ) and thermohydraulic performance factor (η), the investigation encompasses the development of the correlations for 'Nu' and 'ƒ's. The results present that the V-up baffle blocks with racetrack-shaped openings lead to a uniform spanwise dispersion of air-jets through perforations affecting the wake region's flow pattern significantly. The turbulence affects upsurging further with staggered holes results in a substantial rise of Nusselt number and friction factor in the duct. The baffle blocks having e/H of 0.7, p/e of 2 shows up to a 381 % increase in Nusselt number values and a rise of 36 times in friction factor over the smooth duct. The thermohydraulic performance factor's maximum value of 1.405 is obtained for the baffle block having e ⁄ H of 0.6, p ⁄ e of 2 at Reynolds number 14062. The correlations of 'Nu' & 'ƒ' established lies in the ± 11 % & ± 8 % deviation range, respectively.