In this paper we give an introduction to the ideas of quantum thermodynamics, using only basic concepts from quantum and statistical mechanics. Then, we discuss the framework of non-equilibrium processes in quantum systems. We then apply these results to the problem of atom-cavity system while their interaction describe by Jaynes-Cummings model. Here, we introduce the concept of quantum thermodynamics of close quantum system and so by considering a good cavity, coupling of cavity modes with its reservoir has been omitted.