How to simulate feed-effluent preheater — duty from the flowsheet, geometry from edr
A feed/effluent preheater, built so the **shell-and-tube rating** in the Analysis panel has a real duty to rate. The flowsheet answers *how much heat*; the rating answers *whether this exchanger can move it* — the split Aspen sells as EDR, and it had no curated example. **From the flowsheet.** Hot reactor effluent (130 mol/s at 420 K) preheats 120 mol/s of cold feed to 360 K, transferring **1.53 MW** and leaving the hot side at 373 K, against an LMTD of 66.4 K. Those are the numbers you carry into the rating. **The rating (Analysis > HX design).** Put a candidate bundle against that duty — a 0.6 m shell, 320 tubes of 19 mm OD on a 4.88 m length, two tube passes, 0.25 m baffle spacing — and the Bell-Delaware method returns U = **681 W/m2K**, 93.2 m2 available against 53.6 m2 required: **74% over-surface, adequate**. It also exposes the correction factors that actually decide the shell-side coefficient (segmental-cut j_c = 0.91, leakage j_l = 0.67, bypass j_b = 0.54, combined 0.33), which is where a real rating lives — most of the difference between an ideal bank and the bundle you can buy is leakage and bypass. **Reading the margin.** 74% over-surface is generous, not automatically right: it buys fouling allowance and turndown, and costs capital and residence time. The rating is the tool for trading those off — shrink the bundle and watch the margin close. **.
- 1Open the ready-made model
Open the "Feed-effluent preheater — duty from the flowsheet, geometry from EDR" model in the MaximaLabs workspace — no install, no license. It loads live on the canvas, ready to edit and run.
- 2Confirm the thermodynamics
This process is modeled with the PENG-ROBINSON property package over n_hexane, n_heptane — already selected, so the phase equilibrium and enthalpy are physically consistent from the first run.
- 3Review the flowsheet
The flowsheet chains FEED Preheater. Every block is a real, solvable unit op you can reconfigure on the canvas.
- 4Run the simulation
Click Run. The deterministic solver converges the material and energy balances (recycles included) and fills the live stream table — the AI never invents a number.
- 5Read the results and iterate
Inspect the converged streams, tweak a spec, and re-run — or ask the AI copilot to explain a result or diagnose a failed solve in plain English.
- Thermodynamics
- PENG-ROBINSON
- Components
- n_hexane, n_heptane
- Unit operations
- FEED Preheater
Opens live on the canvas — free, no install.
Explore the model & flowsheetModeling assumptions & limitations
What this model captures, and what it deliberately does not — from the engineers who built it.
- 1** Shell-side characterization (Reynolds, Prandtl, conductivity, tube-side coefficient) is supplied as screening input rather than derived from the stream, so this sizes and checks a bundle, it does not replace a vendor's thermal design. The exchanger in the flowsheet is specified by outlet temperature; its own `u_a` rating mode is the alternative when you want the duty to fall out of the geometry instead.
Frequently asked questions
- What does the Feed-effluent preheater — duty from the flowsheet, geometry from EDR model simulate?
- A feed/effluent preheater, built so the **shell-and-tube rating** in the Analysis panel has a real duty to rate. The flowsheet answers *how much heat*; the rating answers *whether this exchanger can move it* — the split Aspen sells as EDR, and it had no curated example. **From the flowsheet.** Hot reactor effluent (130 mol/s at 420 K) preheats 120 mol/s of cold feed to 360 K, transferring **1.53 MW** and leaving the hot side at 373 K, against an LMTD of 66.4 K. Those are the numbers you carry into the rating. **The rating (Analysis > HX design).** Put a candidate bundle against that duty — a 0.6 m shell, 320 tubes of 19 mm OD on a 4.88 m length, two tube passes, 0.25 m baffle spacing — and the Bell-Delaware method returns U = **681 W/m2K**, 93.2 m2 available against 53.6 m2 required: **74% over-surface, adequate**. It also exposes the correction factors that actually decide the shell-side coefficient (segmental-cut j_c = 0.91, leakage j_l = 0.67, bypass j_b = 0.54, combined 0.33), which is where a real rating lives — most of the difference between an ideal bank and the bundle you can buy is leakage and bypass. **Reading the margin.** 74% over-surface is generous, not automatically right: it buys fouling allowance and turndown, and costs capital and residence time. The rating is the tool for trading those off — shrink the bundle and watch the margin close. **.
- Which thermodynamic method does it use?
- The PENG-ROBINSON property package, over n_hexane, n_heptane — already selected. You can switch the method on the canvas before running.
- Which unit operations are in the flowsheet?
- It chains FEED Preheater. Every block is a real, solvable unit operation you can reconfigure, add to, or remove.
- Do I need to install software or buy a license?
- No. Feed-effluent preheater — duty from the flowsheet, geometry from EDR runs entirely in your browser on MaximaLabs — free, no install, no license. Open the model to load it live and run the deterministic solver.
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