Overview
Orwell Design Associates was appointed to deliver the refrigeration design consultancy for a major new National Distribution Centre in the East Midlands for one of the UK's leading supermarket retailers.
Designed to support a large-scale, multi-temperature operation, the project required a highly efficient refrigeration solution capable of delivering reliable performance, operational resilience and long-term energy efficiency.
The Challenge
Facilities of this scale demand more than refrigeration capacity alone. The system needed to operate efficiently across varying temperature zones while maintaining flexibility, minimising energy consumption and supporting future maintenance.
The project also required careful consideration of system resilience, controls integration and safe operation, ensuring the distribution centre could operate reliably around the clock.
Our Approach
ODA developed a high-efficiency CO₂ refrigeration solution centred around six transcritical refrigeration packs. The design incorporated variable speed compressors, parallel compression and heat reclaim technology to optimise system performance across a wide range of operating conditions.
Attention was given to every aspect of the design, from pipework layout and pressure management to plant coordination and controls integration. By considering maintainability alongside performance, we delivered a solution that was both efficient to operate and practical to install and service.
Key Elements
- Six CO₂ transcritical refrigeration rack systems
- Multi-temperature refrigeration design
- Variable speed compressor technology
- Parallel compression for improved efficiency
- Heat reclaim for underfloor heating
- Integrated electrical controls
- Optimised pipework design and system coordination
RDM was selected for the project controls and front-end system. Heat reclaim for the freezer underfloor is connected to packs DT4, 6 & 6 LT discharge. This removes more heat than air cooled de-superheater due to low water temperature.
Refrigeration Rack Systems
Our pack design for performance & energy consideration included:
- 5K TD between room temperature & evaporating temperature’
- 2K TD allowed between gas cooler outlet temperature & maximum ambient temperature = Trans-critical operation 9K TD between condensing temperature & ambient temperature with 5K subcooling for subcritical.
- Parallel compressor is used for better performance.
- Air cooled LT de-superheater is arranged for DT 1, 2 & 3. Heat reclaim plate heat exchanger for freezer underfloor heating connected to DT 4, 5 & 6 LT discharge line as LT de-superheater for better performance.
- Pipework is designed to allow a maximum 0.5K pressure drop in all suction lines.
- All pipes run high level inside the coldrooms to minimise the non-useful superheat in all suction lines.
- Four dual PRV sets are installed on each pack (HT suction, LT suction, liquid receiver & HT discharge).
- Minimum 12.6°C condensing temperature restricted by compressor envelope.
- Discharge pressure 120 bar.
- 3 x 170 litre receivers for DT1, 2 & 3, and 2 x 170 litre receivers for DT4, 5 & 6
Gas Cooler design consideration:
- Coolers & Condensers gas coolers were supplied with EC fans, with each fan motor fitted with local electrical isolation.
- 2K TD between gas cooler outlet temperature and maximum ambient temperature for trans-critical.
- Maximum 10K TD between condensing temperature and ambient temperature for subcritical.
- Gas cooler was sized for 2K TD between gas cooler outlet temperature and maximum ambient temperature for trans-critical. 9K TD between condensing temperature and ambient temperature with 5K subcooling for subcritical.
- Gas cooler fitted with Ecomesh adiabatic pack for better performance at high ambient temperature.
- Blygold coil coating.
The Outcome
ODA delivered a coordinated refrigeration design that met the client's operational, energy and performance objectives for one of its largest distribution facilities. By combining detailed engineering with a consultancy-led approach, the project achieved an efficient, resilient refrigeration solution designed to support reliable operation for years to come.
