ANALISIS SUB-BULUH PADA MODEL REAKTOR SUSUNAN BAHAN BAKAR BUJURSANGKAR ATAU HEKSAGONAL

• Main Author: Winarto
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/1790
• Institution: Institut Teknologi Bandung

Sub-channel analysis is a method for analyzing thermal hydraulic aspects on reactors or heat exchangers, including distribution of fluid temperature, pressure, axial velocity, transverse velocity, and fuel rod temperature or fuel rod heat flux. Using the sub-channel method, calculations of these variables can be done easily and quickly. The purpose of this thesis is to increase the accuracy of the subchannel method. For this purpose, it has been tried to apply three equations for effective enthalpy transported by the diversion cross-flow rate, i.e.: up wind, exponential and central difference, and two equations for effective velocity transported by the diversion cross-flow rate, i.e.: up wind and average velocity. <br /> The differences among calculation results obtained by programs that apply equation of up wind, exponential or central difference for the effective enthalpy transported by the diversion cross-flow rate are very small. This is because the temperature differences of each sub-channel are not large compared to the temperature of its neighbors. Thus, the interface temperatures calculated by up wind, exponential, or central difference are not large difference. Theoretically, the method will be more accurate if using the up wind equation for upstream region and the central difference equation for downstream region. This is because the Peclet number is large at the upstream region and gradually decreases toward the downstream. Applying up wind or average velocity in determining effective velocity transported by the diversion cross-flow rate has little influence to the results of calculation. This is because the velocity differences of each subchannel are small compared to the velocity of its neighbors. Numerically, using the average velocity to determine effective velocity is not a problem so that this equation can be used if needed. Accuracy of the sub-channel method can be increased if the volumeaveraged and area-averaged enthalpy in the energy equation, and the volumeaverage density in the axial momentum equation are calculated based on the fluid temperature at the middle of control volume. Previously, these quantities were determined by using the temperature at topside of the control volume. This causes inaccuracy, and calculation becomes more inaccurate if the control volume is longer.