*Article* **Comparisons of Numerical and Experimental Investigations of the Thermal Performance of Al2O<sup>3</sup> and TiO<sup>2</sup> Nanofluids in a Compact Plate Heat Exchanger**

**Wagd Ajeeb and S M Sohel Murshed \***

IDMEC, Department of Mechanical Engineering, Instituto Superior Técnico, University of Lisbon, 1049-001 Lisbon, Portugal

**\*** Correspondence: smurshed@tecnico.ulisboa.pt

**Abstract:** This study reports the thermal performance of Al2O<sup>3</sup> and TiO<sup>2</sup> nanofluids (NFs) flowing inside a compact plate heat exchanger (CPHE) by comparing the experimental and numerical investigations. The NF samples were prepared for five concentrations each of Al2O<sup>3</sup> and TiO<sup>2</sup> nanoparticles dispersed in distilled water (DW) as a base fluid (BF). The stability of NF samples was ensured, and their viscosity and thermal conductivity were measured. Firstly, the experimental measurements were performed for the heat transfer and fluid flow of the NFs in the plate heat exchanger (PHE) system and then the numerical investigation method was developed for the same PHE dimensions and operation conditions of the experimental investigation. A finite volume method (FVM) and single-phase fluid were used for numerical modelling. The obtained experimental and numerical results show that the thermal performance of the CPHE enhances by adding nanoparticles to the BFs. Furthermore, numerical predictions present lower values of convection heat transfer coefficients than the experimental measurements with a maximum deviation of 12% at the highest flow rate. Nevertheless, the numerical model is suitable with acceptable accuracy for the prediction of NFs through PHE and it becomes better for relatively small particles' concentrations and low flow rates.

**Keywords:** plate heat exchanger; heat transfer; Al2O<sup>3</sup> and TiO<sup>2</sup> nanofluids; numerical model
