*Absorción: Introducción a los coeficientes de transferencia de masa: Problemas... parte 3

Calculating Global Mass Transfer Coefficients

In this section, the speaker discusses the calculation of global mass transfer coefficients, emphasizing the experimental determination or derivation from individual phase coefficients in both liquid and gas phases.

Determining Global Mass Transfer Coefficients

• Global coefficients are determined based on experimental values or derived from individual phase coefficients in both liquid and gas phases.

• Considerations for calculating coefficients include unit conversions of gradients and utilizing the slope in equilibrium equations.

• Total resistance is calculated as the sum of gas phase resistance and liquid phase resistance, involving the inverse of the global coefficient.

• The equation for total resistance includes terms related to individual phase coefficients and slopes.

Calculation of Volumetric Mass Transfer Coefficient

This part focuses on calculating volumetric mass transfer coefficients using specific values for slopes and individual coefficients.

Calculating Volumetric Coefficients

• By substituting given values into calculations, the volumetric mass transfer coefficient is determined in units of atmospheres.

• The next step involves finding another global volumetric mass transfer coefficient from the liquid phase using similar calculations with different parameters.

Determining Another Volumetric Mass Transfer Coefficient

Continuing with calculations, this section explores deriving a different volumetric mass transfer coefficient from known parameters.

Deriving Additional Volumetric Coefficient

• Utilizing expressions for total resistance again, a new volumetric mass transfer coefficient is computed incorporating various factors.

• The calculation involves manipulating equations to find the desired coefficient based on given values for individual coefficients and slopes.

Finding Global Mass Transfer Coefficient in Gas Phase

This segment delves into determining a global mass transfer coefficient specifically in the gas phase through detailed computations.

Computing Gas Phase Global Coefficient

• By substituting provided data into formulas, the global mass transfer coefficient in gas phase concentration units is calculated accurately.

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In this section, the speaker discusses the calculation of global mass transfer coefficients and concentration fractions in gas and liquid phases.

Calculating Global Mass Transfer Coefficients

• The total resistance is the sum of resistances in the gas phase and liquid phase, represented by 1/(overall volumetric coefficient * mol fraction gradient in gas phase).

• Calculation involves multiplying interfacial slope by mol fraction and dividing by volumetric coefficient. Units conversion from English units to mol fraction slope is explained.

• The mol fraction slope is determined as P_gas_total / C_gas_total - P_liquid_total / C_liquid_total.

• Substituting values into the equation yields a slope value for further calculations.

• By rearranging equations, the global coefficient is calculated as 1/(23.25 + 0.289/118.27), resulting in 22 lbmol/h-ft²-mol.

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This part delves into obtaining global mass transfer coefficients through resistance calculations and detailed mathematical operations.

Obtaining Global Mass Transfer Coefficients

• The process involves calculating global mass transfer volumetric coefficients and concentration fractions in both gas and liquid phases.

• Total resistance equals sum of resistances in gas and liquid phases, expressed as 1/(individual volumetric coefficient + individual volumetric coefficient * slope xy).

• The formula includes terms like kxa which can be referenced from transformation coefficient tables for computation ease.

• Simplifying the expression leads to a final equation for determining the global mass transfer coefficient based on given values.

Conclusion

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This section discusses the calculation of mass transfer coefficients and concentration ratios in different phases.

Calculation of Coefficient

• The calculation involves transitioning from a known global volumetric coefficient to a concentration fraction mole unit.

• In diluted solutions, the coefficients for concentration and weight ratios are practically the same.

• For diluted solutions, concentrations approach zero, simplifying calculations.

Coefficient Determination

• The coefficient is determined using a formula involving molecular weights and concentrations.

• Calculations involve specific values such as water's molecular weight (18), ammonia's molecular weight (17), and the given volumetric coefficient (6.358).

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This part focuses on obtaining the final coefficient value through calculations.

Final Coefficient Calculation

• By applying the provided formula with relevant values, a coefficient of 6.73 is obtained for mass transfer in liquid phase.

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Concluding the problem by analyzing resistances in gas and liquid phases.

Resistance Analysis

• Evaluating resistance percentages in gas and liquid phases relative to total resistance.

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In this section, the speaker discusses calculations related to resistance in liquid and gas phases, emphasizing the importance of accurate percentage values for successful formula application.

Resistance Calculations

• : Calculate resistance by multiplying mol by uppercase K and dividing by lowercase k volumetric.

• : Total resistance involves values such as slope at 22 obtained from point 289.

• : Calculate quizá at 118.27, resulting in a value of 5.37% for gas phase resistance.

• : Summing up gas phase (94.63%) and liquid phase (5.37%) resistances yields a total of 100%, validating the accuracy of the percentages in the formula.

• : Conclude problem-solving using individual and global mass transfer coefficients for liquid and gas phases.