This paper proposes a one-dimensional model for in-cylinder heat convection based on the boundary layer theory. The model describes the temporal variations of the velocity boundary layer and thermal boundary layer separately. It is assumed that the behaviour of the boundary layers is quasi-steady: as a whole the boundary layers change with time and wall location, while inside the boundary layers the velocity and temperature profiles follow the steady-state power law.The model integrates the full one-dimensional thin-shear-layer equations with the F-factor correction suggested by Bradshaw and the revised Kutateladze and Leont'ev relation of the velocity and thermal boundary layers. The F factor can compensate for the model error in the curved flow. The revised Kutateladze and Leont'ev relation can correctly reflect the heat transfer mechanism.The model has been validated by a simple approach, using a fixed bulk flow velocity and a surface radius of curvature. The effects of bulk flow, wall temperature, flame penetration and equivalence ratio on heat convection have been investigated. A comparison between the present model and the Woschni formula shows that the calculated overall heat transfer coefficients are in good agreement.This paper clearly shows that the proposed heat convection model can be integrated with the filling-and-emptying method provided the bulk flow is determined either by estimation or by simple calculation. This model has the potential of being used in the multi-dimensional fluid flow code.