Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng Experimentation on effect of particle ratio on hydrothermal performance of plate heat exchanger using hybrid nanofluid Atul Bhattad, Jahar Sarkar ⁎ , Pradyumna Ghosh Department of Mechanical Engineering, Indian Institute of Technology (B.H.U.), Varanasi, UP 221005, India HIGHLIGHTS • Experimental investigation of hybrid nanofluid heat transfer in plate heat exchanger. • Effects of nanoparticle mixture ratio, flow rate and inlet temperature are discussed. • Energetic and exergetic performances are studied using Al 2 O 3 –MWCNT nanofluid. • Hydrothermal performance increases with increase in MWCNT ratio in mixture. ARTICLE INFO Keywords: Hybrid nanofluid MWCNT Plate heat exchanger Particle mixture ratio Performance index Exergy efficiency ABSTRACT To quantify the fostering in energetic and exergetic performances of counter flow corrugated plate heat ex- changer, several experiments were conducted using Al 2 O 3 –MWCNT hybrid nanofluids as coolant. The Al 2 O 3 –MWCNT hybrid nanofluids with different nanoparticle volume ratios (5:0, 4:1, 3:2, 2:3, 1:4 and 0:5) and 0.01 v% concentration were used as a coolant for sub-ambient temperature application. Operating parameters which were varied are the coolant flow rate ranging from 2.0 to 4.0 lpm and coolant inlet temperature from 10 to 25 °C. Effects on heat transfer coefficient, heat transfer coefficient to pressure drop ratio, pump work, perfor- mance index, irreversibility and exergetic efficiency are investigated. Variation of Nusselt number with Reynolds number has also been studied for different nanoparticle volume ratios. Improvement up to 15.2% has been observed in the heat transfer coefficient for MWCNT (0:5) nanofluid with the negligible enhancement of 0.02% in the pump work and 2.96% enhancement in the performance index. Hydrothermal performance of nanofluids increases with increase in MWCNT ratio in particle mixture due to the negligible effect on pressure drop. No optimum ratio has been found within the studied mixture ratios of nanoparticles. 1. Introduction Energy-saving can be done in the thermal systems by altering the thermo-physical properties of the working fluid or by changing the design of heat exchangers. Thus, counter-flow plate heat exchangers with the modulated surface are being used for better energy perfor- mance [1]. And different thermophysical properties of the working fluid are being improved by suspending similar or dissimilar nanosized particles (mono or hybrid nanofluid). Properly engineered hybrid na- nofluids [2] have a higher thermal conductivity as compared to base fluid and adjustable properties to suit different applications. Hybrid nanofluids have the capability to lessen thermal resistances and in- crease industrial groups that would benefit from such improvement, include transportation, electronics, medical, food, and manufacturing. The above abilities provided the gist necessary to begin research in hybrid nanofluids, with the intention that these fluids will play a crucial part in developing the next generation of cooling technology [3,4]. Hence, hybrid nanofluid may be a viable option for improving the en- ergy performance of plate heat exchanger. Since the last decade, many tests have been done on plate heat exchanger using mono nanofluids and showed that the addition of na- noparticles in the base fluid augments the performance of the plate heat exchanger [5–7]. However, studies on hybrid nanofluid in PHE are limited. Huang et al. [8] used a mixture of Al 2 O 3 -water and MWCNT- water nanofluids with 2.5:1 ratio in plate heat exchangers and observed a rise in pressure drop and heat transfer coefficient. Kumar et al. [9] performed an energetic and exergetic analyses on the plate heat ex- changer with various plate spacing using Cu-Al 2 O 3 /water hybrid na- nofluid and reported the best performance for 5 mm spacing. Kumar et al. [10] performed an exergetic analysis on the plate heat exchanger https://doi.org/10.1016/j.applthermaleng.2019.114309 Received 20 April 2019; Received in revised form 23 August 2019; Accepted 24 August 2019 ⁎ Corresponding author. E-mail address: jsarkar.mec@itbhu.ac.in (J. Sarkar). Applied Thermal Engineering 162 (2019) 114309 Available online 26 August 2019 1359-4311/ © 2019 Elsevier Ltd. All rights reserved. T