LNG Offloading and Tank Calculation

Overview

This project simulates the offloading of LNG from a trailer to a storage tank. It calculates the tank's final properties (pressure, temperature, mass, etc.) after offloading, based on thermodynamic data, and visualizes the process.

Features

• Interactive sliders for tank and trailer parameters
• Real-time calculations of final tank state
• Visualization of liquid/gas levels before and after offloading
• Detailed calculation steps displayed

Technologies Used

• HTML/CSS/JavaScript
• D3.js for visualization
• MathJax for equations

Project Structure

• index.html: Main app file with sliders, calculations, and visualization
• D3.js: Tank and process visualizations
• MathJax: Displaying math formulas

How to Run

1. Clone/download the project.
2. Open index.html in a browser.

Sliders and Inputs

• Tank Volume (V_tank): 30 - 80 m³
• Initial Liquid Level (Level_start): 1% - 99%
• Tank Pressure (P_start): 1 - 11 bar
• Trailer Pressure (P_trailer): 0.5 - 10 bar
• Offloaded Mass (m_offload): Mass of LNG offloaded

Calculations

• Interpolates thermodynamic properties using pressure and mass.
• Computes final state: total mass, liquid/gas volumes, pressure, and temperature.

Visualization

D3.js shows tank liquid and gas levels before and after offloading.

Explanation of State Equations

The state of the tank is calculated after offloading using thermodynamic equations, specifically focusing on mass and energy balance.

1. Mass Balance Equation

The total mass in the tank after offloading is the sum of the initial mass in the tank and the offloaded mass:

$$ m_{\text{total}}^{\text{final}} = m_{\text{total}}^{\text{start}} + m_{\text{offload}} $$

Where:

• ( m_{\text{total}}^{\text{final}} ) is the total mass in the tank after offloading.
• ( m_{\text{total}}^{\text{start}} ) is the initial mass in the tank.
• ( m_{\text{offload}} ) is the mass of LNG transferred from the trailer.

2. Energy Balance Equation

The internal energy of the system is updated by adding the energy associated with the offloaded LNG:

$$ U_{\text{total}}^{\text{final}} = U_{\text{total}}^{\text{start}} + (m_{\text{offload}} \cdot h_{\text{liquid}}^{\text{trailer}}) $$

Where:

• ( U_{\text{total}}^{\text{final}} ) is the total internal energy in the tank after offloading.
• ( h_{\text{liquid}}^{\text{trailer}} ) is the specific enthalpy of the liquid from the trailer.

3. Specific Internal Energy and Volume

After offloading, the average specific internal energy and specific volume of the tank are calculated as follows:

$$ u_{\text{final}} = \frac{U_{\text{total}}^{\text{final}}}{m_{\text{total}}^{\text{final}}} $$

$$ v_{\text{final}} = \frac{V_{\text{tank}}}{m_{\text{total}}^{\text{final}}} $$

Where:

• ( u_{\text{final}} ) is the specific internal energy after offloading.
• ( v_{\text{final}} ) is the specific volume after offloading.

4. Pressure Estimation

The final tank pressure ( P_{\text{final}} ) is determined by iterating through thermodynamic tables to find the pressure that corresponds to the calculated specific internal energy and volume:

$$ P_{\text{final}} = f(v_{\text{final}}, u_{\text{final}}) $$

5. Liquid-Gas Quality

The liquid-gas ratio (quality) ( x ) is determined by the following equation using the specific volumes of the liquid and gas:

$$ x = \frac{v_{\text{final}} - v_{\text{liquid}}}{v_{\text{gas}} - v_{\text{liquid}}} $$

Where:

• ( v_{\text{liquid}} ) is the specific volume of the liquid phase.
• ( v_{\text{gas}} ) is the specific volume of the gas phase.

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By using these equations, the program calculates the final pressure, temperature, liquid level, and mass distribution within the tank after offloading.