Finite element analysis of stresses during cooling of eggs with different physical characteristics

Maximum thermally induced stresses in eggshell under rapid cooling conditions were predicted using a validated axisymmetric finite element model (AFEM). The maximum thermally induced stress in the eggshell occurred immediately upon cooling, i.e., after 1 s of rapid cooling (h = 2839.0 W/m² °C or 500 Btu/h-ft²-°F). For typical extra-large eggs, the AFEM calculated eggshell stresses were 1.79 MPa (260 psi) and 1.73 MPa (251 psi) for meridional and circumferential directions, respectively. Maximum thermally induced stresses occurred along the outer boundary at the interface between air cell and albumen. Increasing eggshell thickness, air cell size, cooling rate, and the taper angle favored higher thermally induced stresses. Among the ten test cases, Case 7 (M, THIN), which was a medium egg (the maximum principal, i.e., pole to pole, dimension a = 28.5 mm (1.1 in.), minimum principal dimension b = 21.2 mm (0.83 in.), taper angle θ = 5°, air cell size = 5% by volume) with thin eggshell (shell thickness, t = 0.305 mm (0.012 in.) under rapid cooling, experienced the smallest maximum thermally induced stress (1.47 MPa or 214 psi). Consequently, an egg with these or similar physical characteristic values is likely to have less damage due to stress-induced cracking during rapid cooling.