Times have changed. Hardly 40 years ago, it was common practice to equip every refrigerated cabinet
with a stand-alone refrigeration unit. There were 25 of these standing around in the Freiburg cafeteria
on the Natural Sciences Campus, some even dating back to the early seventies. The kitchen equipment
was just as technically outdated, which is why the operator of the facility, the Studentenwerk, decided to fundamentally renovate the cafeteria kitchen, which of course automatically included renovation of the refrigeration technology. GEA Küba supplied the necessary evaporators.

Renovation of the refrigeration system was planned for two stages. Stage one is complete, but until stage two follows in 2010, two refrigeration systems will still be running in parallel. The refrigerated cabinets, four cold rooms, and one freezer room of the renovated cafeteria kitchen are connected to a new central refrigeration plant, but the cold-storage rooms for supplies in the basement are still being cooled by the old water chiller.

“When we designed the plant, we naturally took into account future expansion in terms of power required. The plant delivers approx. 35 kW, which is about 10 – 12 kW more than required right now. This capacity will be needed in future for the cold rooms in the basement,” says Jochen Windisch, Managing Director of the company Müller & Co GmbH of Rosenberg, Germany. The design office Vtechnik GmbH in Gaggenau, Germany, did the planning for the central refrigeration plant and the kitchen and food serving counter. Installation of the refrigeration piping and electric cabling was somewhat adventuresome at times. The new refrigeration units were installed in the utility room for heating and ventilation in the basement directly adjacent to the old refrigeration units that are still serving the basement section. The pipes and cables therefore already lay tightly squeezed in under the ceiling. To install the required new lines, it was necessary at times to climb over old and existing lines and air ducts at heights of over four meters, to find enough available space for installation.

The multicompressor refrigeration system for chilling is a 4-stage Bitzer compound unit. This makes the single switching steps relatively small, facilitating optimal output adjustment. The plant supplies 21 refrigerated display cabinets and 15 refrigerated counters with prepared dishes and beverages, plus three adjacent cold rooms and the preparation cold room. Fruit, vegetables, meat, and dairy products are cooled here. The refrigerant R404A was used. The system is connected to a heat-recovery system to noticeably increase the system’s energy balance, thereby exploiting savings potential.

The waste heat warms 800 liters of domestic water in a separate boiler, via a heat exchanger. This volume of water covers hot-water demand in the kitchen. The freezer room is decoupled (also spatially) and has its own refrigeration system. The same applies to the shock freezer. Müller & Co GmbH, refrigeration and air conditioning specialists, installs mainly GEA Küba evaporators and in this project again equipped the cold rooms with space-saving slim-line ceiling Air Coolers from the Küba Green Line Junior DF series. Mr. Windisch is delighted with the quality of the evaporators. “The units run trouble-free and are durable. The corrosion resistance is outstanding. The entire construction is maintenance-friendly and is designed in such a way that we can integrate valves and other components without a problem. The performance specifications are reliable and the extensive range of duty allows a wide cooling range to be covered.”

The cold-storage rooms measure between 6 and 22 m². GEA Küba’s DF evaporators provide consistently reliable cooling. One DFA 022 C was installed in each of the milk and vegetable cold-storage rooms. The evaporators are defrosted twice a day using ambient air – thereby saving energy. In the third cold room, where the meat is stored, a Junior DFA evaporator of the same design and with electric defrosting was installed. The condensate is drained off to the outside, thus reliably preventing any proliferation of pathogens.

Each evaporator has two fans with 4.5-cm fin spacing; the output of the fans is exactly tailored to the size of the rooms, along with an air throw of 6 m. The separate preparation room is cooled by a DFBE 051 C evaporator with 7-mm fin spacing. Due to the high rate of access to the room with the resulting inflow of humidity, this unit also has an electric heater for defrosting. A GEA Küba Market Plus Green Line SPBE 022D high-performance evaporator was installed in the freezer room.

“I am time and again impressed by the perfect frosting pattern. We have had no icing problems so far. It couldn’t be better!” said Mr. Windisch in a discussion. The entire plant is fitted with electronic cooling controllers enabling full remote control and temperature records via a bus and RS485 interface. The chef in the kitchen can supervise and save the temperature status and possible fault messages on his computer, to monitor and control the system. Should a door not be properly closed, this is immediately displayed on the chef’s PC and an alarm is triggered. In the second construction stage, the cold storage rooms in the basement will be connected to the central multicompressor refrigeration system – “again with GEA Küba evaporators of course,” concluded Mr. Windisch.

Müller & Co GmbH’s success story started 45 years ago. A steady expansion of staff and clientele has created a solid foundation for healthy company growth. Müller & Co GmbH is a modern training company operating throughout Germany with a competent team of 10 persons. The main area of activity is in communal catering, such as commercial kitchens, company canteens, hospitals, etc. A wide field is also covered in the air conditioning sector with split and VRV air conditioning units. Water chillers and heat exchangers in the industrial sector constitute another key area in their much-diversified field of business.