In designing ship equipment, we encounter many problems concerning heat convection which depends upon turbulent flow of gas, such as the distribution of cold air in reefer hold of refrigerating cargo ship and the atmosphere in cabin during air-conditioning. Most of these problems have been treated so far by the practical way along with the empirical trial and error. However, according to enlarge the scale of air-conditioning system and refrigerating system, rigorous analyses to estimate the quantity of heat transfer and the distribution of air temperature are required for strict energy saving. In this paper, the eddy viscosity coefficient of turbulent flow is obtained by use of so-called two equation models¹⁾ which are the transport equations on the kinetic energy of turbulence and the turbulence energy dissipation rate. The equation of convectional heat diffusion is solved subsequently using the obtained coefficient. Finite element method is applied through the above-mentioned procedure to solve the equations in this report. Practical applications of the analyses of the atmosphere in reefer holds of refrigerating cargo ship, in which heat sensitive cargoes are stored, are carried out to estimate the variations of the distribution of flow velocity, eddy diffusion coefficient and air temperature. The relations between the variation of air temperature as time proceeds and the decisive factors governing thermal diffusion, i. e. type of duct system, number of inlets and thickness of heat insulation, are clarified by the results of analyses.