Coatings are applied to improve various properties, such as corrosion resistance, abrasion resistance, toughness, chemical resistance, etc. One of the most common materials used for coating purposes is polyurethane foams because of their simple handling, economic cost, and proper physical properties [
1,
2,
3]. In the recent decade, researchers have studied how coating thickness affects heat transfer in finned-tube heat exchangers [
4,
5]. An accurate estimation of coating thickness is crucial to increase the heat exchanger lifetime especially in high working temperatures [
6]. Machine-learning methods have recently attracted much attention along usual approaches for heat transfer and thermodynamics analysis. For instance, estimating the heat values of different kinds of fuel with machine-learning methods is faster and computationally cheaper instead of direct calculations and experiments [
7,
8]. Machine-learning models are also employed to predict the optimal system design. Mohamed et al. suggested multiple machine-learning models to predict eleven different parameters for the optimal design of proton exchange membrane (PEM) electrolyzer cells [
9]. Recently, machine learning has shown great promise in computational fluid dynamics (CFD) studies [
10] and is becoming more accurate and faster [
11,
12]. Making machine-learning models with acceptable generalization capability for different heat transfer problems is another approach that made analysis faster. For instance, a universal condensation heat transfer and pressure drop model has been recently proposed by using machine learning techniques [
13]. These techniques are also used to analyze heat exchangers for different purposes like predicting the thermal performance of fins for a novel heat exchanger [
14]. Lindqvist et al. used machine learning models to optimize heat exchanger designs and developed good correlations with trends in the CFD model [
15]. Moreover, machine-learning has shown great potential in predicting heat transfer for high order nonlinear cases [
16]. In the absence of a valid physical-based model, machine learning can be utilized to predict heat transfer in many thermal systems [
17]. Considering recent advances in machine learning techniques, CFD computational cost can be reduced by using genetic algorithms [
18]. Similarly, neural networks were found to be effective for analyzing thermal conductivity assessment of oil-based hybrid nanofluids [
19]. Gradient boosting decision trees can reduce the cost of measuring equipment for computing transient heat flux [
20]. Although more advanced ensemble models can lead to better results for more complicated datasets [
21], the use of such models in heat transfer problems has received less attention. The most common model of this category, random forest, showed a remarkable ability to evaluate heat transfer across various scenarios [
22]. Swarts et al. compared three different algorithms for predicting critical heat flux for pillar-modified surfaces and concluded that random forest provides the best results [
23]. Its performance on large datasets [
24] and a precise ranking of features' importance [
25] are the main Random forest's advantages. Despite the benefits of random forest and other machine learning algorithms, collecting training data can be a challenge. The number of data required for training can be minimized by combining features, which enhances the regression accuracy too [
26]. As far as the author knows, there are no studies on machine-learning models that investigate the correlation between coating and heat transfer in a heat exchanger. This study fills this gap with machine-learning models with acceptable generalization capability on unseen data
.
In this study, a new method of combining input features is proposed to investigate the effect of variable coating thickness on the prediction of heat transfer in a finned-tube heat exchanger at different inlet Reynolds numbers. Almost 1000 different cases are simulated using a 3D finite volume model to generate the data set. The random forest model is initially trained using numerical simulation data. By using the created model, selected features are combined, and new features are added. In addition, various new data are used to validate models’ interpolations. At last, the capability of the introduced method for dimension reduction is investigated with different models. The main contributions of this study are summarized as follows.