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Show I In i iu.il hlliticno (/ m Outlet I cinp. Ii'om Convective Section ^ c ,° "a E w 73 E U o .e H 0 j, : Final Outlet Temp, from Q j,r . < >utlet Temp, from the Boiler Rcjjencrativc Section 90 SO - / N: • 1 ' One 0* 1 1 1 1 V y i . -i 7 0gr / / ^ " - - ' ' 70 - - (SO r>00 - 400 - 200 P o u -«-> 03 U O a. s o 50 100 H By-pass Ratio, tp \ % | Fig. 3.7 Calculated Flue Gas Temperature and Thermal Efficiency vs. By-pass Ratio 4. DISCUSSION 4.1 Effect of Cycle Time on Heat Flux The temporal variation of heat flux was calculated by employing the unsteady heat transfer model that incorporated the periodic and repetitive heating and cooling of a semi-infinite section of the slab. A schematic diagram of the model is shown in Fig.4.1. Appropriate governing equations are given in Eq.(4.1)-(4.5). The results shown in Fig. 4.2 clearly show that the heat flux density is increased by shortening the cycle time. Since heating and cooling of the regenerator provides the unsteady heat transfer, short cycle time provides the maximum extraction of the heat flux. The results also show that the maximum extraction of heat flux occurs during the beginning of the unsteady heat condition. Surface Temperature 0 (JC,f)*=o Ceramics (SiC) thermal diffusivity K K = 0.109 m2/hr Initial Temperature 0 (JC,0«=o = 0 L x=0 Fig.4.1 Unsteady-state Heat Conduction of a Semi-Infinite Slab with Peripdic Temperature Change 12 11-8 |