Exhaust gas recirculation (EGR) cooler plays an important role in reducing the nitrogen oxides (NOx) emission of diesel engines. By using the CFDesign software, in this paper, the finite element models are established for analyzing the thermodynamic performance of an EGR cooler. The temperature, velocity and pressure fields of the fluids in the EGR cooler are simulated and verified. Based on these models, furthermore, the thermodynamic performance of the EGR cooler with different structures of cooling tube are analyzed, compared and discussed. The results show that, under the fixed pressure boundary conditions, the EGR cooling efficiency can be significantly increased by properly design the fin number of the cooling tube in EGR coolers.

The most attractive secret of the leaves is why they have the various shapes and the weight of the leaves. Based on the theory of gene and ecological environment, a model is built in this paper to explore it. The result can be extended to predict the weight of any parts of the tree and adapted for great majority kinds of trees.

The analytical evaluation and finite element methods are used to analyze the critical stability of the shallow spherical roof of oil storage tank with an axial symmetrical corrosion region. At first, the nonlinear finite element method is adopted to calculate the global critical load of the storage tank roof, and the local corrosion region is equivalent to a circular corrosion pit with uniform depth. The results show that the tank wall and inner pressure of the stored oil have slight effects on the stability of the roof. To build the formula of local critical load of the tank roof, the circular corrosion pit is separated from the whole roof and treated as a shallow spherical shell which is elastically supported on the rest part of the roof. The equivalent support stiffness is obtained by the deformation compatibility at the edge of the corrosion pit. The resulted nonlinear stability equation is solved with a modified iteration method to determine the local critical load. The local critical load for an in-service corroded oil tank roof is analyzed by the proposed approach and the results are compared with those calculated by the conventional nonlinear finite element method with good agreement and the geometrical parameter of the corrosion region corresponding to the minimal critical load is 9.5.