Utilizing jet impingement on protrusion/dimple heated plate to improve the performance of double pass solar heat collector

Abstract

The effect of geometrical parameters of jet impingement on indented protrusion absorber in double-pass solar heat collector (DPSHC) was investigated. For fixed optimum values of protrusion parameters namely arc angle (αp), relative height ratio (ep/Dh), and relative pitch ratio (p/Dh), four different jet height ratios (Hji/Dh) ranging from 0.11 to 0.44 have been used with varying streamwise pitch (Xji/Dh) and spanwise pitch ratio (Yji/Dh). At a constant jet diameter ratio (Dji/Dh), the Reynolds number (Re) of the airflow fluctuated between 2500 and 22500. It has been found that the Hji/Dh plays an important role in the performance of DPSHC and that the maximum value of the Nusselt number (Nudp) = 544 with friction factor (ffdp) = 0.206 was obtained at Xji/Dh=1.32, Hji/Dh=0.22, and Yji/Dh=1.32. The investigation reveals that the thermohydraulic performance (ηdp) of the DPSHC increases as the Re increases from 2500 to 15000 and after that from 15000 to 22500 it starts to decline. The optimum value of ηdp = 3.86 has been found corresponding to Re = 15000, Hji/Dh=0.22, Xji/Dh=1.32, and Yji/Dh=1.32. Nudp and ffdp correlations were developed in terms of jet impingement parameters and the selected range of Re which can be useful for estimating the performance of a DPSHC with the combined technique. The optimum deviation in the Nudp and ffdp values was ±10%, which correlated well with the experimental results.