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Title:	Heat transfer enhancement in twin circular jet impingement flows
Authors:	Mahir Faris Abdullah (P74532)
Supervisor:	Rozli Zulkifli, Assoc. Prof. Ir. Dr.
Keywords:	Heat -- Transmission Jets Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	2-Oct-2019
Description:	Impinging jets are used in several heating and cooling-related industrial and engineering applications like the cooling of the electronic chips and gas turbine blades, and the dry food industries, owing to their high convective heat transfer coefficients. In this study, the author noted a lack of information regarding the increase in the heat transfer rate using the twin impingement jets placed at a horizontal distance from a stagnation point. Very few studies used a nanocoated aluminium plate for enhancing the heat transfer. Furthermore, none of the studies investigated the relationship between the Nusselt number and other parameters. Here, the author aimed to study the mixing region of the twin jets arrangement for improving the flow and heat transfer; determine the effect of altering the aluminium plate surface by surfacecoating it with 3 different TiO2 nanosolution concentrations, and determine the heat transfer rate at a horizontal distance from a stagnation point at the surface. This study tried to improve the heat transfer rate using a twin jet impingement system and investigated the effect of the nozzle-plate distance, nozzle-nozzle distance, and the Reynolds number at a horizontal distance from the stagnation point on the Nusselt number (Nu) and heat transfer coefficients. The heat flux values were also measured using temperature microfoil sensor. This study used a Design of Experiment (DOE) approach along with the Response Surface Methodology (RSM) by D-optimal algorithm for designing 25 experiments, analysing the empirical model and optimising all factors used in the study. These factors included a variation in the jet-plate position at differing nozzle-plate distances (H/d) of 0.5, 3, and 5.5 and a nozzle-nozzle space (S/d) of 0.5, 1, and 1.5; nanocoat concentrations (Ø) of 0.2, 1 and 2% (v/v); and Reynolds numbers of 17,000, 13000, and 9000. 3 differing heat transfer enhancement processes which are TiO2 nanocoat, aluminium plate heat sink along with the twin jet impingement system were considered. This study also determined whether parameters like nozzle space, nanosolution concentration, and nozzle-plate distance increased the heat transfer rate of a twin jet impingement system on the hot aluminium surface. Furthermore, this study conducted a computational study by stimulating the twin impingement jet, using an RNG k-ε turbulence model in the ANSYS Fluent Software. Various nanosolutions, of different nanoparticle concentrations, were coated on a metal surface. Then, an X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) analysis were done, which highlighted the structure and showed that the nanosolution coated the surface homogenously. The position of the twin jets was investigated best model that helped in estimating the heat transfer coefficient and maximum Nu of 94.7, where H/d = S/d = 0.5; Reynolds number of 17000, and TiO2 nanosolution concentration of 1% (v/v). After analysing the results, it's concluded that the flow structure of the twin impingement jets at an interference zone was the main aspect which affected the heat transfer enhancement. The combined effect of the spacing and the nanosolution concentration significantly influenced the flow structure, and heat transfer properties, while the Reynolds number (nanosolution concentration of 1%, v/v) significantly affected the Nu number. The numerical simulation study indicated of increased the heat transfer rate by 24% while from experimental was around 37%. The results also described the effect of the different models on the twin impingement jet.,Ph.D.
Pages:	196
Call Number:	QC320.A233 2019 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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