Case Study
Conditioned Air Upgrade for a Spiral Cooler in a High-Volume Bakery
Overview
Client: Large UK Bakery Manufacturing Facility
Industry: Food Manufacturing
Project Overview: Newsome designed and delivered a conditioned air system for a spiral cooler at a bakery site, replacing inconsistent ambient air supply that caused overcooling in winter and poor performance in summer. The new solution combined mixed air tempering and chilled glycol cooling to provide stable temperatures, improve product consistency, and support better hygiene and efficiency.
Newsome was appointed to design and deliver a new conditioned air solution for a Manhattan Spiral Cooler at a large bakery manufacturing site. The existing cooler was supplied with unconditioned ambient air, which created inconsistent operating conditions across the year. In winter, the product was being overcooled. In summer, the available cooling duty was not sufficient to maintain the required performance. At the same time, the site wanted to achieve a lower and more consistent product core temperature to support satisfactory downstream cutting.
The project involved the replacement of an ageing air handling unit, together with the introduction of tempered supply air through mixed return and fresh air in low ambient conditions, and chilled glycol cooling during higher summer temperatures. The final design provided a more stable and controllable process environment while also addressing hygiene, reliability and energy performance.
The Challenge
The existing air handling unit had reached the end of its useful service life. Installed in 2004, it was in poor hygienic condition and was fitted with an inefficient belt-driven centrifugal fan arrangement. From a process point of view, the operating strategy was also limiting performance. Because the spiral cooler was supplied with untreated ambient air, the system was fully exposed to seasonal variation. During winter, low outdoor temperatures caused overcooling. During summer, warm ambient conditions reduced the cooling effect available to the spiral cooler, leading to inconsistent product temperature control. This variation affected process stability and made it more difficult to achieve the lower guaranteed product core temperature the client wanted.
A further constraint was that the cooler and its associated ductwork had already been designed around a defined airflow volume. The new system therefore had to match the existing supply and exhaust duties while improving air treatment and plant efficiency.
Design Criteria
Newsome developed the replacement system around the existing airflow requirement for the spiral cooler. The design supply air volume was set at 12 m³/s, with return and exhaust airflow at 11 m³/s. The design supply air temperature was based on 10°C, with the minimum supply air temperature varying through the use of mixed return air during low ambient conditions.
For summer operation, the system was sized around a maximum ambient design condition of 32°C and 40% relative humidity. Cooling was to be provided by a dedicated packaged chiller supplying glycol at minus 1°C flow and plus 6°C return. The design objective was to maintain a more stable air condition to the spiral cooler across the full annual operating range.
The Newsome Solution
To resolve the seasonal inconsistency, Newsome proposed a new air handling unit with the ability to temper fresh air by mixing it with return and exhaust air during colder periods, and to cool fresh air via a chilled glycol coil during warmer conditions. This gave the client full control over supply air condition without changing the basic airflow arrangement of the cooler.
The replacement AHU was built with hygienic and long-life performance in mind. The construction used Plastisol panels internally and externally, mounted within a painted aluminium pentapost framework. Internally, the unit incorporated a return air fan section with EC direct-drive backward curved fans, a mixing chamber with fully modulating dampers, G4 pre-filtration, high-grade bag filtration, a split chilled glycol cooling coil and a supply fan section with EC motors.
This arrangement replaced the inefficient belt-driven fan arrangement with a far more efficient EC fan package, improving controllability, reducing maintenance burden and supporting lower running costs.
Air Handling Unit Performance
The air handling unit was designed to match the existing process airflow while improving the quality and consistency of supply air. The extract fan arrangement handled 11 m³/s using four EC backward curved fans arranged in a quad fan configuration. The supply side handled 12 m³/s using a matching four-fan arrangement. This provided the required duty while also introducing fan redundancy and improved controllability.
The filtration stages were selected to improve air cleanliness and protect both the cooling coil and the process environment. A panel filter stage was installed upstream, followed by rigid high-efficiency filtration. This gave the unit a more appropriate hygienic standard than the original equipment and improved its suitability for food manufacturing use.
The cooling coil was manufactured using polyester-coated copper tubes, aluminium fins and a painted galvanised casing to provide long-term resistance against the airborne process additives present within the area. Under design summer conditions, the coil was sized to cool incoming air from 32°C down to 10°C, with a total duty of approximately 484 kW.
Chilled Glycol Plant
To serve the new AHU cooling coil, Newsome also supplied a dedicated roof-mounted air-cooled packaged chiller. The selected unit was sized to provide approximately 485 kW of cooling at design conditions. It used R454B refrigerant, selected for its comparatively low Global Warming Potential and suitability as a modern long-term alternative to higher GWP refrigerants such as R410A. The chiller was positioned on existing roof steelwork previously used for a redundant chiller, making effective use of the available plant space. Redundant rooftop equipment in the area was also cleared as part of the works.
From a performance perspective, the chiller was configured with multiple scroll compressors, dual refrigeration circuits and a shell-and-tube evaporator. This provided resilience, good part-load performance and dependable operation in a demanding industrial application. The stated energy efficiency ratio and seasonal performance figures supported the project objective of improving not only process consistency but also overall plant efficiency.
Pipework, Controls and Integration
New 304 stainless steel glycol pipework was installed between the chiller and the AHU cooling coil. The pipework was supported from Unistrut bracketry fixed beneath the existing roof gantry steelwork, with insulated support blocks provided throughout to prevent thermal bridging. The circuit included a three-port modulating control valve, isolating valves, regulating valves, vents and drains to support commissioning, balancing and future maintenance. Once pressure tested and filled, the pipework was insulated with foil-faced phenolic insulation and finished with plain Aluzinc cladding. Valves and flanges were enclosed in purpose-made insulated boxes to maintain a consistent finish and allow future access.
The AHU was supplied with an integral Easy IO controls package, and Newsome included full controls commissioning. This allowed the new plant to modulate between mixed-air tempering and chilled operation depending on ambient conditions, giving the site a much greater level of process control than the previous ambient air system.
Installation and Delivery
The installation was carefully planned around roof access, lifting requirements and site safety. The lifting operation was based on crane access from the rear car park. The existing AHU was isolated, stripped of insulation and cladding, mechanically disconnected and then split into sections for removal. Existing duct taper sections were also replaced with new galvanised steel sections.
Following removal of the original unit and preparation of the support steelwork, the new AHU sections were lifted into place, fixed together and sealed. The new taper sections were connected, and the rooftop ductwork was re-insulated and clad to match the new specification. At the end of the works, Newsome completed full commissioning, client handover and project documentation.
Outcome
The completed installation provided the bakery with a far more stable and controllable air supply to its Manhattan Spiral Cooler. The previous dependence on ambient air was removed, allowing the site to avoid overcooling in winter and insufficient cooling in summer. The new arrangement also supported the client’s requirement for a lower, more reliable product core temperature to improve downstream cutting performance. In addition to the process benefit, the project addressed several plant-related concerns. The old end-of-life AHU was replaced with a cleaner, more hygienic and more efficient system. EC fan technology improved electrical efficiency and reduced maintenance compared with the previous belt-driven arrangement. The introduction of dedicated chilled glycol cooling and intelligent air mixing gave the client year-round control of supply air condition.
This project is a strong example of Newsome’s ability to design and deliver engineered temperature control upgrades that solve practical production problems while improving hygiene, efficiency and long-term reliability in food manufacturing environments.