Number of Transfer Units (NTU)
Compute the number of transfer units (NTU) of an absorption or stripping column (dilute case), NTU = ln(C_in/C_out), from the inlet and outlet concentrations. NTU measures the 'difficulty' of the separation: the greater the removal desired, the more transfer units are needed. Together with the height of a unit (HTU), it defines the total packing height. Enter the inlet and outlet concentrations.
Result
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Número de unidades de transferência (NTU)
Quando se quer absorver um gás poluente numa torre (CO₂, H₂S, SO₂) ou arrancar (stripping) um componente de um líquido, surge a pergunta: que altura de coluna é preciso? O método HTU-NTU divide o problema em dois fatores independentes. O NTU (número de unidades de transferência) — aqui no caso diluído, NTU = ln(C_entrada/C_saída) — é a parte termodinâmica: mede a 'dificuldade' da separação, ou seja, o quão perto do equilíbrio se quer chegar. Remover 90% exige um certo NTU; remover 99% exige bem mais (a relação é logarítmica — os últimos resíduos são os mais difíceis de tirar). O NTU é como o número de 'andares' de equilíbrio necessários, mas para colunas recheadas (de operação contínua, sem pratos discretos). Multiplicado pela altura de cada unidade (HTU), dá a altura total do recheio. Informe as concentrações de entrada e de saída.
Related Tools
Packing Height (HTU·NTU)
Compute the packing height of an absorption or distillation column, Z = HTU·NTU, multiplying the height of a transfer unit (HTU, which depends on hydrodynamics and packing type) by the number of transfer units (NTU, which depends on the desired separation). It is the HTU-NTU method of sizing packed columns — it separates the 'kinetic' part (HTU) from the 'thermodynamic' (NTU). Enter the HTU and the NTU.
Actual Plates (Efficiency)
Compute the number of actual plates of a distillation column, N_actual = N_theoretical / (efficiency/100), from the number of theoretical (equilibrium) plates and the column's overall efficiency (%). Since no real plate reaches perfect equilibrium, more actual plates than theoretical are needed: a 50% efficiency doubles the plate count. It is the step that turns the theoretical design into the physical column. Enter the theoretical plates and the overall efficiency.
Minimum Reflux (Underwood)
Estimate the minimum reflux ratio of a binary distillation by Underwood's equation (saturated-liquid feed), Rmin = [xD/xF − α·(1−xD)/(1−xF)]/(α − 1), from the relative volatility (α) and the light-component mole fractions in the distillate (xD) and feed (xF). At minimum reflux, the column would need infinite plates; the operating reflux is a multiple of it (1.1–1.5×). It is a key number in column design. Enter α, xD and xF.
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