Assured Chill behind bars
The public purse is empty. That’s why municipalities and states are increasingly having public building projects financed by private investors. This model is known as public private partnership (PPP). Sachsen-Anhalt was the first German Federal State to approve new construction and partly also the operation of a prison through public private partnership. In Burg, a consortium controlled by Bilfinger Berger BOT GmbH built Europe’s most modern and secure prison with a total investment of EUR 512 million and housing 650 inmates on an area the size of 27 football fields. The planners also played it safe with respect to the refrigeration systems: GEA Küba supplied the evaporators for the canteen kitchen’s refrigeration plant.
Initial planning for the major project started in 2002. In April 2007, Justice Minister Prof. Angela Kolb turned the first sod for the construction of the new prison on the roughly 220,000 m² site near Magdeburg, Germany adjacent to the A2 freeway. Following a two-year construction period, the first inmates moved in at the beginning of May 2009. Shortly before this we had open house, at which around 22,000 visitors had an inspection tour of the four prison buildings and used the opportunity
to view the prison cells. The State has signed a 25-year license agreement and pays a rental for preventive and restorative maintenance by private service providers.
Virtually simultaneous with the Minister breaking ground, Kühlanlagenbau Süd-West GmbH, a subsidiary of Dresdener Kühlanlagenbau GmbH, started with planning for a refrigeration plant for a total of six coldstorage rooms and three freezer rooms for the canteen kitchen. The design called for separation of cold storage and a cold room for daily use. Location and layout of the rooms was specified.
The facilities feature a self-contained refrigeration complex comprising four cold-storage and two freezer rooms and a precooler room in the center with air lock. This area is accessible from two sides and is used for storage. One of the access points is directly from the kitchen. The opposite door is for delivery. “The doors are opened several times a day. This causes a rather high exchange of air with the corresponding moisture formation in the precooler room,” says Andreas Henker, the site manager for the Burg correctional facility at the Greiz, Germany, offices of Kühlanlagenbau Süd-West GmbH. To meet this situation with energy-effectiveness, he included two GEA Küba Junior DFB evaporators with three fans, each already at the planning stage. The large fin surface facilitates effective dehumidification. The difference between the temperature of the air influx and the evaporation temperature of the refrigerant is approx. 5 to 6 K. Icing of the fins can thus safely be prevented even without electrical defrosting.
“We exclusively install GEA Küba evaporators for applications such as these. We have been doing this for many years. In our experience, there’s nothing better. The Junior DF series cannot be beaten from the handling and reliability points of view and they have the necessary performance reserves to remain on the safe side, even in extreme situations. And the service is tops. Should a problem arise, the GEA Küba Service team is immediately at hand with a solution. This we can rely on,” says Henker.
The Küba Junior DF is a ceiling air cooler from the GEA Küba Green Line, designed in 14 output sizes especially for commercial refrigeration and excels by a 9‑m maximum air throw. The drip tray has an optional horizontal or vertical drain. The high-grade powder-coated aluminum housing offers ideal corrosion protection. An integrated deflector ensures optimal airflow. The drip tray can be folded down for easier cleaning and maintenance.
The DF evaporators provide assured consistent refrigeration – also in the cold-storage rooms for meat, dairy products, vegetables, fats, and oils. For the almost 8 m² of area per cold room, Henker selected
fin tube heat exchangers with 7 mm fin spacing, with an output accurately matching these requirements. To defrost, the evaporators are briefly switched off twice daily while the fans continue running, swirling cold air up to 6 °C over the fins. “This is enough to properly defrost the fins,” says Henker.
A GEA Küba Market Plus SPB high-performance evaporator with fan and with 7-mm fin spacing and 2.45 kW cooling duty was installed in each of the two freezer rooms located at the back of the cooling system to the left and right of the precooler room. The air coolers feature electric defrosting. The easily removable side covers enable quick access to the fins with the thermostatic injector valve and the electric terminal box for the defrosting heater and fans. This reduces maintenance costs. “The GEA Küba components are extremely maintenance-friendly. Another reason why we install only this equipment,” says Henker.
A separate cold-storage room for daily access with an adjoining freezer room is located next to the main cold storage; it is used for preparing the meals and is more easily accessible to the chefs. The evaporator design is identical to the other heat exchangers, since the spatial arrangements are the same. There were no additional installation requirements to secure the evaporators against vandalism or unscrewing. “It was basically a very conventional building site – once you were inside,” says Henker. The only area where he always felt uneasy was at the checkpoint, where the security staff had very stringent instructions to enforce. “If we arrived in a car without having submitted its number plate beforehand for checking, they would leave you waiting an hour and a half before closed doors,” recalls Henker.
In the autumn of 2007, the refrigeration fitters started with the installation. Turnover was in February 2008. “We switched off the plant after a flawless three weeks test run. The plant was started only when the first inmates arrived,” says Henker. Since then, the Küba evaporators guarantee assured chill behind closed doors.