Latent heat of a phase change material (PCM) is commonly used for energy storage and thermal management. A flat bed configuration is commonly used in latent energy storage systems, in which, fluid flow over a PCM bed results in heat transfer to/from and melting/solidification of the PCM. Understanding the nature of heat transfer in such systems is critical for design and performance optimization. This paper presents an analytical model for conjugate heat transfer in a flat bed latent energy storage system. The model solves the governing energy conservation equations by utilizing the interfacial conditions to iterate between the PCM and fluid flow. Good convergence of the iterative technique is demonstrated. The model is used to study phase change propagation and energy storage as functions of various problem parameters such as imposed temperature difference, flow velocity and thermal properties of PCM and fluid flow. It is found that the convective heat transfer coefficient between the PCM and fluid flow is not constant, but, rather, is a function of space and time, and is affected by flow speed and properties, as well as thermal properties of the PCM. The general methodology presented here can be adapted for annular and other latent energy storage configurations. This work contributes towards a fundamental understanding of heat transfer processes in an important energy storage system that is commonly encountered in practical applications.