How to simulate desiccant rotor hvac — three-stage low-grade heat recovery
A desiccant dehumidification rotor whose **regeneration air is preheated by three low-grade heat sources in ascending temperature order**: a PVT (photovoltaic-thermal) collector loop at 40 °C, condenser heat rejected by the chiller at 50 °C, and a district-heating return at 55 °C. Cascading them warmest-last is the whole point — each coil lifts the air as far as its own source can reach, so the 55 °C district return is spent only on the final lift instead of being wasted on air that is still at ambient. Every coil leaves a **5 K approach at its hot end**, which is what makes this solvable: a cold stream can never leave an exchanger hotter than the hot stream entering it, and in a series train each coil's outlet is the next one's inlet, so a target that looks reasonable in isolation becomes impossible two units downstream. The hot-side flows are sized so the water gives up its duty over a modest ΔT and stays above the air at the cold end as well — specifying the approach alone is not enough if the heat-capacity flow rates don't support it. The rotor's two halves are `custom_block` equation blocks (the regen side and the process side), and the process air is finished to a 16 °C supply condition by the evaporator coil.
- 1Open the ready-made model
Open the "Desiccant rotor HVAC — three-stage low-grade heat recovery" 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 air, water — already selected, so the phase equilibrium and enthalpy are physically consistent from the first run.
- 3Review the flowsheet
The flowsheet chains 3× District Coil, 2× Dehum Section, Evap Coil. 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
- air, water
- Unit operations
- 3× District Coil2× Dehum SectionEvap Coil
Opens live on the canvas — free, no install.
Explore the model & flowsheetFrequently asked questions
- What does the Desiccant rotor HVAC — three-stage low-grade heat recovery model simulate?
- A desiccant dehumidification rotor whose **regeneration air is preheated by three low-grade heat sources in ascending temperature order**: a PVT (photovoltaic-thermal) collector loop at 40 °C, condenser heat rejected by the chiller at 50 °C, and a district-heating return at 55 °C. Cascading them warmest-last is the whole point — each coil lifts the air as far as its own source can reach, so the 55 °C district return is spent only on the final lift instead of being wasted on air that is still at ambient. Every coil leaves a **5 K approach at its hot end**, which is what makes this solvable: a cold stream can never leave an exchanger hotter than the hot stream entering it, and in a series train each coil's outlet is the next one's inlet, so a target that looks reasonable in isolation becomes impossible two units downstream. The hot-side flows are sized so the water gives up its duty over a modest ΔT and stays above the air at the cold end as well — specifying the approach alone is not enough if the heat-capacity flow rates don't support it. The rotor's two halves are `custom_block` equation blocks (the regen side and the process side), and the process air is finished to a 16 °C supply condition by the evaporator coil.
- Which thermodynamic method does it use?
- The PENG-ROBINSON property package, over air, water — already selected. You can switch the method on the canvas before running.
- Which unit operations are in the flowsheet?
- It chains 3× District Coil, 2× Dehum Section, Evap Coil. 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. Desiccant rotor HVAC — three-stage low-grade heat recovery 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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