Temperature gradient tests deposits

The mechanism of temperature-gradient mass transfer is illustrated in Figure 1. This type of corrosion may be studied in a thermal-convection loop test (Figure 2). Because the solubility of most container materials in a particular liquid metal is temperature-dependent, solution in the hot section and subsequent deposition in a cooler section may occur. The results of this type of corrosion may be seen in Figures 3 and 4. 

The simplest nonisothermal flowing system where processes associated with dissolution and deposition occur is one in which flow is induced by thermal convection. This is accomplished by heating one leg of a closed loop and cooling another leg. The flow rate is dependent on the height of the heated and cooled sections, on the temperature gradient, and on the physical properties of the liquid. Both single-phase (all-liquid) and two-phase (liquid-vapor) loops have been tested. In some cases, thermal convection loops are destructively examined after operation [55,67]. In others, specimens are removed and replaced numerous times for cumulative periods of 10 000 h or more [22,54,68],... 

---