## 1 Introduction
[36] have studied the effect of heat transfer on the ideal air standard cycle by considering the heat loss during the cycle of a real engine and have shown improved engine performance over a diesel engine. In the engine simulation, a highly accurate heat transfer coefficient must be used in the exhaust system to predict engine performance. This led to a proposal of a new heat model by considering the turbulence decay and velocity fluctuations, and results on enhanced predictions in engine performance are presented in [37]. A two-zone combustion model for an SI engine's heat transfer correlations is evaluated by [PERSON] et al. [38], considering heat loss to the chamber and heat exchange during knocking for better predictability. A multi-zone thermodynamic model for SI engine model prediction is assessed by considering flame wrinkling, flame development, geometry, and heat transfer for accurately modeling the engine combustion process [39]. The same has been reassessed by [PERSON] et al. [40], who have shown CFD comparisons for high accuracy. [PERSON] et al. [41] have performed studies for thermodynamic performance improvement of a diesel engine, considering heat transfer and friction loss, and showed power and efficiency improvement. Using heat release of combustion data, a calibrated heat transfer correlation has been assessed by [PERSON] et al. [42] for enhanced model prediction. The effects of heat transfer are studied not only on combustion engines, but also on sustainable mobilities such as battery electric vehicles. A numerical review of lithium-ion batteries is presented in [43], studying the effects of heat transfer for thermal runaway. The effect of heat transfer in a Stirling engine is studied for waste heat energy recovery by [PERSON] et al. [44]. Reliable conjugate heat transfer methodology to reduce the effect of engine heat losses is depicted in [45]. To reduce the heat transfer losses and increase thermal efficiency, an in-cylinder thermal barrier coating technique is studied by [PERSON] et al. [46]. The novelty of this work lies in evaluating the effect of the heat transfer coefficient during scavenging to predict the in-cylinder temperature and trapped mass in an advanced two-stroke powertrain. This evaluation assesses state-of-the-art heat transfer correlations and a proposed heat transfer coefficient. The proposed heat transfer correlation uses mass flow in the intake and exhaust ports to calculate the necessary convective coefficient during scavenging, and eliminates the usage of the mean piston velocity for calculating the convective heat transfer coefficient. The methodology followed in developing the proposed heat transfer model is yet to considered in any previous state-of-the-art heat transfer correlations. All the convective models are developed in a 1D engine model, and results for the evaluation are compared with CFD simulation results. Firstly, taking advantage of the experimental campaign, the 1D model is validated for fluid-dynamicperformance. Results from the validated 1D model are then used as initial and boundary conditions for CFD simulation. Finally, the proposed heat transfer correlation results are evaluated for potential impact during scavenging. A detailed description of the procedure followed to capture the experimental results is provided in Section 2 of this manuscript. The same section shows the information on the model developed in 1D mode, validation of the 1D model, and CFD setup. Section 3 presents the method followed in developing the state-of-the-art and proposed heat transfer models. Results comparing different heat transfer models are presented and discussed in Section 4. Finally, the conclusions showing the primary outcomes of this study are outlined.