Refrigeration / Fruit and vegetable Storages

At the Hamburg Central Market Hall, the lights go on bright and early – not long after lights have gone out in other businesses. Under the undulating roof of the great hall – built in 1962 and now protected as part of German architectural heritage – night becomes as bright as day. Stand operators begin to set up their shopping displays before midnight to ensure that wholesalers can purchase fresh fruit and vegetables. From 1:00 a.m. to 9:00 a.m., wholesale buying of fruit and vegetables takes place. At this wholesale market, fresh-food businesses face tough competition. Structural evolutions that have recently taken place in the German food retail business have left behind clearly telling signs. Earlier, the Hamburg Central Market Hall primarily served suppliers of weekly food markets throughout the city. Now, however, the majority of customers are food service wholesalers, who for the most part order peeled, shelled, and sliced goods.

The wholesale stand of the “Die Neuenkirchener Heidekartoffel GmbH includes approx. 650 m² of open space for pallets and for maneuvering of the forklifts, four cold rooms, as well as an energy house that accommodates administration and staff rooms. The open space provides room for sacked onions and canned goods, as well as offerings of other noncooled goods. Sacked potatoes are stored in two cold rooms at 5 to 7 °C. The cold room controlled at 3 to 5 °C contains easily perishable goods, convenience food, and eggs. The fourth cold room, at 4 to 6 °C, stores ready-to-cook peeled or sliced potatoes, vegetables, and herbs. The total refrigerated space includes 500 m², and together there is a total of approx. 80 pallet storage points in the four cold rooms.

Compared to power consumption of the old systems, the present concept designed by Wassim Dahche – Project Engineer of the Hamburg refrigeration company Westermann Kältetechnik – and the new multicompressor refrigeration system built by Westermann achieves, for the same cold room volume and the same floor space, power savings of one-third. This Westermann multicompressor plant, with two GEA Bock HGX compressors, as well as Kelvion evaporators, has maximum refrigeration duty of 60.0 kW. The refrigeration plant is output- and frequency controlled, since the compressors are regulated via an inverter. The Küba SGBE 092C direct evaporators are monitored via electronically controlled injection valves. Energy efficiency in the cold rooms. In each of the four cold rooms, one Küba SGBE 092C air cooler with a duty range between 15 and 19 kW assures the proper temperature as well as sufficient relative humidity. The Kelvion evaporators each have two fans, which circulate air at a rate of 9,060 m³/h. With fin spacing of 7 mm, air throw in the open space is 37 m, at an air velocity of 0.5 m/s.

Despite the low temperature difference at the evaporator, the great surface area and the air output provide for constant and controlled relative humidity – which ensures that the products can be stored on the shelves in accordance with regulations. The electronic injection valves provide optimal and output-oriented control of the direct evaporators and, in turn, offer great energy efficiency of the refrigeration plant. The refrigeration plant in Hamburg is controlled with the aid of a load- and switchcontrol cabinet with electronic refrigeration actuators and signal lamps. A databus connects each refrigeration point as well as the multicompressor refrigeration plant with a PC in the administration center, from which the systems are monitored. This system immediately provides acoustic and optical alarms in case of malfunctions such as temperature deviations in the cold rooms. As soon as the doors of the cold rooms are opened, the refrigeration system is immediately switched off by the door contact switch. The entire energy-efficient package – which meets extremely high standards also with respect to lighting systems and other building operations – is designed for a life cycle of 20 years.