Optimizing Thermal Performance of Mini Heat Exchangers: An Experimental Analysis Using a Full Factorial Design  
[PERSON]  
1 Department of Mechanical Engineering, Federal University of Pernambuco, Cidade Universitaria, 1235, Re Reife 50670-901, Brazil; [EMAIL_ADDRESS] (S.G.S.F. ); [EMAIL_ADDRESS] (A.A.S.L. );[EMAIL_ADDRESS] (J.A.P.d.C). [PERSON]  
1 Department of Mechanical Engineering, Federal University of Pernambuco, Cidade Universitaria, 1235, Reife 50670-901, Brazil; [EMAIL_ADDRESS] (S.G.S.F. ); [EMAIL_ADDRESS] (A.A.S.L. );[EMAIL_ADDRESS] (J.A.P.d.C). [PERSON]  
1 Department of Mechanical Engineering, Federal University of Pernambuco, Cidade Universitaria, 1235, Reife 50670-901, Brazil; [EMAIL_ADDRESS] (S.G.S.F. ); [EMAIL_ADDRESS] (A.A.S.L. );[EMAIL_ADDRESS] (J.A.P.d.C). [PERSON]  
1 Department of Mechanical Engineering, Federal University of Pernambuco, Cidade Universitaria, 1235, Reife 50670-901, Brazil; [EMAIL_ADDRESS] (S.G.S.F. ); [EMAIL_ADDRESS] (A.A.S.L. );[EMAIL_ADDRESS] (J.A.P.d.C). [PERSON]  
2 Department of Higher Education Courses (DACS), Federal Institute of Education, Science and Technology of Pernambuco, Av. [PERSON], 500, Reife 507040-545, Brazil; [EMAIL_ADDRESS] (G.A.N.P.L. );[EMAIL_ADDRESS] (M.V. ); [EMAIL_ADDRESS] (K.A.F.) [PERSON]  
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components [5]. Nevertheless, as channel sizes decrease, the flow and heat transfer characteristics can differ considerably from those observed at conventional scales [6]. Additional experimental studies are necessary, as existing research results have been insufficient and, in some cases, show significant discrepancies [7]. Several studies have demonstrated the influence of various parameters on the heat dissipation process in micro-heat exchangers [8], including geometry [9], the nanofluid concentration [10], Reynolds number [10; 11], the twist ratio [10], the mass flow rate [12], temperature, pressure, the exergy loss rate, the friction factor, and efficiency [11], among others. However, evaluating the effect of these parameters is challenging and time-consuming. The traditional technique used for this evaluation is the _one-factor-at-a-time_ (OFAT) method, where one variable is changed while the others remain at fixed levels. In contrast, a more efficient approach involves using chemometric methods, such as full factorial designs (FFDs), where the levels of all parameters are simultaneously altered [13]. In FFDs, the response variable (e.g., process efficiency) is measured for all possible combinations of the chosen factor levels. Comparing FFDs with the classical OFAT experiment is essential to understand the advantages and limitations of each approach in scientific experimentation. An FFD involves manipulating all factors of interest simultaneously at all possible levels. This approach allows for observing not only the main effects of each factor but also the interactions between them. The primary advantages of an FFD include the identification of interactions, as it enables the detection of interactions between factors, which the OFAT method cannot achieve [14; 15]. Additionally, an FFD provides statistical efficiency by generating more precise estimates of the effects of factors and interactions due to efficient data use [16]. An FFD also offers a comprehensive exploration of the experimental space, providing a comprehensive view of how factors influence the outcome, thereby enabling the construction of more robust predictive models [17]. Contrarily to chemometric methods, the OFAT method involves varying one factor while keeping all others constant. This approach is simpler to implement and analyze, particularly in preliminary experiments. However, it has several limitations. A major limitation is its inability to detect interactions, as only one factor is varied at a time [14; 15].