Supermarket transcritical R744 pack sizing — start to spec
By DigiEntropy Engineering · 2026-02-08 · 7 min read
Transcritical CO2 has dominated new European supermarket refrigeration since ~2018. Pack sizing has its own conventions — booster vs flooded, parallel compression, ejectors, gas cooler approach. The Supermarket Refrigeration page walks through it.
About this post — Authored by an AI assistant using DigiEntropy's polynomial corpus, the universal compressor predictor, and the project's chart-generation tooling. Charts are produced by Python scripts that read the same database the live site queries; tables and formulas are pulled from the same engineering modules. Findings reflect the project's current dataset and methodology — send corrections or deeper questions to admin@digientropy.com. Every new commercial supermarket designed in the EU since the 2024 F-Gas Regulation tightening has been R744 transcritical. The architecture is well-understood (booster pack with MT + LT compressors sharing a gas cooler) but the sizing is non-trivial — you need to match MT load to MT compressors, LT load to LT compressors, gas cooler to combined heat rejection, and decide on parallel compression + ejector + heat reclaim before committing capex. Supermarket Refrigeration walks the design from store-level cabinet loads to the final pack spec. The MT vs LT load split MT loads: - Vertical refrigerated cabinets (dairy, deli, produce): -8 to +4 °C cabinet, evaporator typically -10 °C - Walk-in chillers (back-of-house): +2 °C room, evaporator typically -5 °C - Beverage coolers, sushi displays: similar to vertical cabinets LT loads: - Frozen vertical cabinets: -22 to -18 °C, evaporator typically -32 °C - Walk-in freezers: -22 to -18 °C, evaporator typically -28 °C - Ice cream cabinets (some plug-in, some on the LT rack): -25 to -22 °C cabinet A typical mid-size supermarket (2000 m² floor area, 400 m² refrigerated): 60-80 kW MT, 15-25 kW LT. Booster vs flooded The two dominant transcritical R744 architectures: Booster Flooded (parallel) --------- LT compression Single stage from -32 °C to MT pressure (25 bar) Single stage from -32 °C to discharge (100 bar) MT compression Second stage from MT pressure (25 bar) to discharge Direct from MT pressure to discharge Complexity Simpler — single gas cooler, no LT discharge to gas cooler More efficient at LT, more complex piping When to pick Most installations under 100 kW total Larger / energy-sensitive installations The Supermarket Refrigeration page defaults to booster and offers flooded as an upgrade with the COP delta computed in-line. Parallel compression + ejectors Once the base architecture is set, two add-ons swing efficiency significantly: Parallel compression — adds dedicated compressor(s) for the flash gas from the receiver. Without it, flash gas throttles down to MT pressure (wasting work). With it, flash gas is recompressed directly to discharge. - COP gain: typically…