Diffusivity by Twin Bulb Method Calculator

Diffusion Coefficient Formula:

\[ D_{AB} = \frac{\frac{L}{a \times t} \times \ln\left(\frac{P_T}{P_{A1}-P_{A2}}\right)}{\frac{1}{V_1} + \frac{1}{V_2}} \]

Length of Tube:

Inner Cross Section Area:

m²

Diffusion Time:

Total Pressure of Gas:

Partial Pressure in 1:

Partial Pressure in 2:

Volume of Gas 1:

m³

Volume of Gas 2:

m³

Diffusion Coefficient (m²/s):

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1. What is Diffusivity by Twin Bulb Method?

Definition: This calculator determines the diffusion coefficient (D_AB) of a gas pair using the twin bulb method, which measures how quickly one gas diffuses into another.

Purpose: It's essential for chemical engineering applications, gas separation processes, and understanding mass transfer phenomena.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ D_{AB} = \frac{\frac{L}{a \times t} \times \ln\left(\frac{P_T}{P_{A1}-P_{A2}}\right)}{\frac{1}{V_1} + \frac{1}{V_2}} \]

Where:

\( D_{AB} \) — Diffusion coefficient (m²/s)
\( L \) — Length of connecting tube (m)
\( a \) — Cross-sectional area of tube (m²)
\( t \) — Diffusion time (s)
\( P_T \) — Total pressure (Pa)
\( P_{A1}, P_{A2} \) — Partial pressures in bulbs 1 and 2 (Pa)
\( V_1, V_2 \) — Volumes of bulbs 1 and 2 (m³)

Explanation: The formula calculates how quickly component A diffuses through component B based on pressure changes in two connected bulbs over time.

3. Importance of Diffusion Coefficient

Details: The diffusion coefficient is crucial for designing separation processes, predicting gas mixing rates, and modeling mass transfer in chemical reactors.

4. Using the Calculator

Tips: Enter all required parameters in consistent SI units. Ensure partial pressure difference (P_A1 - P_A2) is positive for valid calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for diffusion coefficients?
A: For gases at standard conditions, D_AB typically ranges from 10^-6 to 10^-5 m²/s.

Q2: Why use the twin bulb method?
A: It provides a simple experimental setup for measuring gas diffusivity with reasonable accuracy.

Q3: How does temperature affect the results?
A: Diffusion coefficients increase with temperature (≈T^1.75). This calculator assumes isothermal conditions.

Q4: What if I get a negative value?
A: Check your pressure inputs - P_A1 must be greater than P_A2 for valid results.

Q5: How accurate is this method?
A: Accuracy depends on precise measurement of all parameters, especially the partial pressures and time.