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In the present study, an experimental investigation of performance evaluation of plate heat exchanger (PHE) with the rough surface using AL2O3/water nanofluid was achieved. The experiments were developed for different surface roughnesses of 0.978 µm (smooth surface), 1.276 µm, 2.825 µm and 3.657 µm with different volume fractions of nanoparticles of 1.2 vol.%, 1.9 vol.% and 2.6 vol.% at Reynolds number of 500 ≤ Re ≤5000. The Nusselt number (Nu), the friction factor (f) and the heat transfer enhancement factor (HTEF) were estimated. The results show that increasing the volume fraction of nanoparticles and surface roughness enhances the heat transfer rate as well as increases the pressure drop in PHE. Hence, the influence of surface roughness is more considerable than that of volume fraction of nanoparticles on PHE performance. Furthermore, for smooth surface, the HTEF is improved by 2%, 3.7% and 5.4% for volume fraction of nanoparticles of 1.2 vol.%, 1.9 vol.% and 2.6 vol.%, respectively; while these values for the highest value of surface roughness, i.e., 3.657 µm, are 9.4%, 11.8% and 13.7%. Based on the experimental results, a new empirical correlation to predict Nu for base fluid is obtained with a maximum deviation of 2.87%. [ABSTRACT FROM AUTHOR]

• Fluid flow and thermal performances of PHE are investigated experimentally. • The effectiveness and NTU of PHE are improved with increasing Rr. • Pressure drop and pumping power are increased by increasing Rr. • SHR is improved with increasing surface roughness particularly at low Reynolds number. • Empirical correlations are proposed to predict SHR as a function of Rr and Re. In the present paper, an experimental study of the effectiveness and pumping power of plate heat exchanger (PHE) with rough surface was performed. The experiments were developed for different values of relative roughness, Rr, of 2.6 * 10−4 (smooth surface), 3.4 * 10−4, 7.5 * 10−4 and 9.8 * 10−4 for Reynolds number, Re, varied from 500 to 5000. The average heat transfer rate, Q avg , hence the effectiveness of PHE, ε , and number of transfer units, NTU , as well as pressure drop, Δp , consequently pumping power, P, and specfic heat rate, SHR, were estimated. The results show that Q avg and NTU are enhanced with increasing Rr ; while, they are decreased with increasing Re. At Re = 5000, the effectiveness of PHE with relative roughness of 3.4 * 10−4, 7.5 * 10−4 and 9.8 * 10−4 is greater than that of the smooth surface by 11.5%, 16.6% and 18.6%, respectively. Furthermore, Δp and P are increased by increasing Rr and Re. Moreover, at Re = 500, SHR is enhanced with increasing Rr and its improvements compared with the smooth surface are 39.5%, 23.4% and 6.9% for Rr of 3.4 * 10−4, 7.5 * 10−4 and 9.8 * 10−4, respectively. In addition, empirical correlations are proposed to estimate SHR as a function of Rr and Re with a standard deviation of 5.1%. [ABSTRACT FROM AUTHOR]