Horizontal tube liquid-driven evaporators find widespread application in industries such as chemicals, textiles, and food processing. In evaporative heat exchangers, heat transfer variables around the horizontal round tube inherently fluctuate. Significant variations in film thickness are observed in the upper and lower regions of the tube. Employing a transient liquid surface tracking technique, focusing on the interface of two immiscible phases, is crucial. This paper conducts an insightful study to analyze the surface heat transfer and hydrodynamic behaviour of gravity driven film flow, considering various factors such as geometrical arrangements, liquid flow rate (Ref = 850, 1050 & 1250), and flow fluctuations. The influence of film thickness is investigated by a Volume of Fluid (VOF) model implemented in ANSYS CFD software. The results, validated against Nusselt (1916) correlations and experiments conducted by researchers documented in the literature, indicate that the maximum error in simulations is limited to 6%.