cooling surface
1.Based on several actual cases, the temperature control measures for roller compacted concrete (RCC) gravity dam and arch dam such as structural jointing for construction; lowering of concrete placing temperature; water pipe cooling; surface insulation; inclined-layer placing etc., the measures to improve the material properties i.e. the application of micro-expanding concrete; enhancement of material crack-resistance property and the requirement for the simulative analysis on both the temperature field and stress field as well as some problems concerned are summarized herein on the basis of the analysis on the material properties; construction characteristics and the changing characteristics of the thermal stress of roller compacted concrete.
5.A numerical method, based on single temperature sensor, constant heat flux assumed and arbitrary number future time steps, was employed to determine the heat flux during rapid cooling on high temperature surface with multiply immersed impinging water jets The finite volume discretization method and treatment of boundary condition were presented.
9.The results show that a warm high ridge at the middle level and transformed surface cold high over the plain provide a good background condition; a cooling process produced by net surface radiation fluxes is the trigger and strengthening mechanism for the fog event; the subsidence flow at the middle and low tropospheric levels is favorable for the setting-up and maintenance of stable stratification at the boundary layer and weak wind condition at the ground layer over the fog region; the transportation of weak warm advection at lower levels and weak lift motion at the boundary layer play a very important role to the long maintenance of the fog event; the intrusion of north wind accompanied by cold advection is a main dynamic factor of the fog dissipation.
10.Results showed that under furnace cooling and water cooling conditions,the volume fraction of Mo_2 Ni_3 Si primary dendrite and the secondary dendrite arm spacing decreased with increasing cooling rate. However,for the alloy under laser surface remelting condition which had the highest cooling rate (～10~3 K/s),the volume fraction of Mo_2 Ni_3 Si primary dendrite increased markedly to about 62%.
