OCR Text |
Show (m3/sec) (m3 /cm) G Vm h A Flow rate of the combustion gas Net volume of the honeycomb cell Heat transfer coefficient Heat transfer surface area on the honeycomb cell (kcal/m2 sec °C) (m2 /cm) Fig. 2 shows the sequence for calcula ting the honeycomb cell tempera ture. While it exemplifies the case where combustion gas and air are supplied only once, actually the calculation is repeated until the temperature distribution of the honeycomb just before the changeover has the same profile as the previous data has. Equa tions (4)', (5)', (1)', and (6)' are those calcula ting the prehea ted air temperature in the reheat cycle, but detailed descriptions are omitted in this paper. The following assumptions are made in this simulation model: 1. The temperature gradient appears only on the combustion gas flow path in the regenerator media. 2. The combustion gas forms a plug flow without any drift. 3. The heat conductivity is sufficiently larger than the heat transfer coefficient. The temperature distribution in the honeycomb wall is negligible. 4. The heat loss in the regenerator media is not considered. (2) Wall thickness model The honeycomb wall is divided into ten layers in the direction of thickness, and the heat balance is examined in each layer. It is assumed that, as shown in Fig. 3, after the wall is heated by the combustion gas for a given time (i.e. , the changeover time), the wall is cooled by the air during the same time. This heating and cooling cycle is repeated until the temperature distribution of the wall just before the changeover has the same profile as in the previous data. For this calculations, the following 5 equations are used: q",1 hAC T" T 1 ) x 1 see q i ,j = kA x Isee q i - 1 ,i = q i ,j + QR i Q~.s (i • t .. 5) (i • t .. 4) [keal] [keal] [keal] [keal] [keal] (I) (2) (3) (4) (5) Wh~re qOl layer qij qRi Heat quantity transferred between the ambient gas and the first Heat quantity transferred between layer i and j h k Stored heat of layer i Heat transfer coefficient Heat conductivity of the wall (kcal/m2 sec A Cpm Heat transfer surface area on the wall (kcal/m sec (m2 ) Specific heat of the wall (kcal/m3 °C) T Wall thickness Ti Mean temperature of layer i TiO Initial temperature of layer i Calculating the above 5 equations every distribution of the honeycomb wall. - 3 - (m) (OC) (OC) second yields the temperature |