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Show Refinery Heater Simulation by Hottel Zoning Hethod 11 VI. BXHTPGH - Refinery Box Heaters The simplest design is the radiant single gas space cabin heater (Figure 3) . Variations may include: 1 . side wall, floor, roof, one side or both ends firing, 2 . vertical or horizontal tubes, 3 . single row of tubes in vertical center plane with burners on both sides of coil, 4 . free standing wall in center with burners floor burners firing against or near wall, 5 . tubes above floor with down draft. A two gas space heater (Figure 4) may have all the above variations. In addition, the two cells may have different services. In this case it would be analyzed as a two gas space radiant box with a common convection section. If services were equal in all respects, then it would be analyzed as two equal single gas space etc. Hany refinery heaters have four gas spaces, they are treated as two gas spaces having two of end gas space I and 2 of the interior gas space . A three gas space analysis is required to analyze the U-tube design (Figure 7) and reactor heater (Figure 8). A. Box Gas Space Zoning Each different gas space is zoned 3 by 4 by 4 in the X, Y and Z dimensions. Z is always in the direction of firing, and X , the narrower of the other two dimensions. Figure 9 is an example of a single gas space radiant box fired from both ends. The gas control volume is defined by the outer dash lines. A long narrow box which is floor fired can be modelled by using a single gas space having one or two burners. The results are corrected for the actual Y dimension by the appropriate multiplier . B . Total Interchange Areas (TIA) For each gas space and each gas medium, 48 by 48 gas - gas volume zones TIAs, 48 by 80 gas - surface zones and 80 by 80 surface - surfaces zones are computed or 37632 TIAs for a single gas space. The computational procedure is to: 1 . Divide the each gas volume zone into near-square subzones, taking B - Hinimum (~X , ~Y, ~Z) / N |