The development of an embryo in an avian egg depends largely on its temperature. The embryo temperature is affected by its environment and the heat produced by the egg. In contemporary incubators, the environment holds the air surrounding the egg, the tray, neighbouring eggs and possibly the incubator itself. In this paper, the heat transfer from one egg in a tray towards its environment is studied by means of computational fluid dynamics (CFD). The objectives are: (1) to find out whether CFD can successfully simulate eggshell temperature from one egg in a tray, (2) to visualize flow and temperature distribution around the egg in a detailed way, (3) perform sensitivity analysis on several variables affecting heat transfer. To this end, a CFD model is tuned using temperature measurements and validated with an other set of measured data, yielding an effective model. From these simulations, flow and temperature distribution around the egg are visualized. Sensitivity analysis indicate that average eggshell temperature is mainly affected by the inlet air velocity and temperature, flow direction and the metabolic heat of the embryo, but far less by the thermal conductivity and emissivity of the egg and the thermal emissivity of the tray.