Artoza, Christian Jelo R. 2019-01811 BSCHE 3-1 Computer Applications in ChE Final Project Sizing of a Plate-Fin Heat Exchanger Operating Conditions and Geometrical Variables The goal is to Design a direct-transfer regenerator for an open-cycle gas-turbine plant operating at an effectiveness of 0.75355 with the following operating conditions and heat transfer surfaces. A. Mean Temperature Calculations and Fluid Properties Since the exchanger effectiveness was specified in the design problem, the definition of effectiveness was used to calculate the outlet temperature on both fluid sides. π= πΆβ πβ,π − πβ,π πΆπππ πβ,π − ππ,π = πΆπ ππ,π − ππ,π πΆπππ πβ,π − ππ,π πΆ For the first iteration, the same heat capacities for both fluid sides were assumed so that πΆβ = πβ . ππ π The resulting outlet temperatures for the first iteration were then used to calculate the mean temperature, and the heat capacity on both fluid sides. With the obtained heat capacity, a number of iterations were carried out to determine the outlet temperatures, and subsequently, the mean temperatures and the fluid properties were refined accordingly. B. NTU Calculations Both fluids were assumed to be unmixed, and the flow arrangement was set to be crossflow. Hence, the following effectiveness-NTU relationship was used: π = 1 − exp 1 πΆ∗ πππ 0.22 {exp −πΆ ∗ πππ 0.78 − 1} Where πΆ ∗ is the capacity rate ratio. The number of transfer units for the gas and air fluid sides, which are needed in the estimation of the mass velocities, were then estimated as ππππππ = ππππππ = 2πππ. C. Surface Basic Heat Transfer and Flow Friction Characteristics Heat transfer and flow friction data were retrieved from Kays and London (2018). With these data, j and f versus Re plots were constructed and appropriate curve fit models were obtained. Since Re is unknown in the first iteration, an approximate average of the ratio of the Colburn factor j to the friction factor f over the complete range of Re was obtained. Subsequently, mass velocities on the two fluid sides were obtained using the core mass velocity equation provided by Kays and London (2018): πΊ= π π Δπ ππ NTUπ πππ π£π Pr 2/3 Re, j and f on both fluid sides were then calculated with the mass velocities and the heat transfer data; and heat transfer coefficients were obtained using : β = ππΊππ Pr −2/3 D. Efficiencies and Overall Coefficient The fin efficiency and the extended surface efficiency on both fluid sides were obtained as follows, assuming that no heat transfer occurs at the tip of each fin: ππ = tanh ππ , ππ π= 2β , πππΏ ππ = 1 − 1 − ππ π΄π π΄ Where π= π −πΏ 2 Assuming no fouling resistances, the gas side overall heat transfer coefficient for the first iteration was obtained by: 1 1 = ππ ππ β + π πΌπ ΤπΌπ ππ β π The air side overall coefficient was obtained similarly. E. Areas and Flow Lengths F. Pressure Drops