Munich’s well-chilled “Belly”
They are Europe’s fifth largest food retail center: the Munich market halls in the center of town. “Munich’s belly” near the Isar was inaugurated in 1912 as a municipal undertaking and still supplies the population with high quality foods and flowers to this day. Josef Goldstein Fruchtimport-Export GmbH is one of the largest traders here. The company recently built three new long-term storage rooms for fruit and vegetables, including an entrance zone for selection and packaging, in the market halls – and in this process also invested in refrigeration systems. The contracted refrigeration company FRIESS-TECHNIK, FRIESS GmbH installed 16 industrial high-performance evaporators with hinged drip trays and hinged SG series fans in the GEA Küba’s Blue Line range, to meet the IFS (International Food Standard) hygiene standard and to reduce the maintenance costs of cleaning the heat exchangers.
The specifications presented to Mr. Friess-Becker were clear-cut: minimum investment, assured reliability, and sustained low operating costs. The cold-storage rooms were to be accommodated in an existing warehouse. To utilize the space to the maximum and simultaneously provide maximum reliability in the storerooms, the Munich plant-systems contractor installed four compounded systems with 5 compressors each and positioned these behind the hall. To minimize noise, horizontal scroll compressors were selected, which were in addition placed in noise-suppressing weatherproof
metal housing for better soundproofing. Since fresh fruit and vegetables are very perishable, Goldstein invested particularly in the reliability of the refrigeration system.
There are two linked systems to reliably cool the storerooms – depending on the products to be refrigerated and the demand – to between + 6 °C and ± 0 °C. Each cold-storage room is equipped with two Küba Blue Line SG evaporators. One evaporator per cold room is connected to one compounded system. Cross-connection guarantees reliable cooling of the sensitive produce, even if one of the system fails. Another advantage of this configuration is that sufficient cold gas is always
available for the defrosting phases. With cold-gas defrosting, the compressor pumps the refrigerant
through the air cooler in reverse direction. This sustainably saves energy. “I like this system since it has energy-saving advantages, due particularly to smaller temperature differences between ambient air and the defrosting medium – and it is above all gentler on materials than hot gas defrosting,” says Christian Friess- Becker.
“We first direct the gas flow through the evaporator drip tray and, once this is warm enough, through the coil,” says Friess-Becker. This ensures that the dripping condensate does not ice up in the drip tray. Individual compressors can also be switched off during partial-load operation. This reduces operating costs and is more energy-efficient than frequency control. The cold rooms are sometimes heavily frequented. Thanks to the entrance zone for selection and packaging, which serves as a cooling buffer and is reliably cooled by four SGB 50-F81 evaporators, energy loss due to circulating air exchange in the storerooms themselves is significantly reduced. As a result, the defrosting cycles are also relatively long. The system performed only twelve defrosting cycles in 2009.
Since larger volumes were stored in quicker succession during the summer months, with the outside temperatures high, the system at times defrosted automatically up to three times a month. During the winter months, on the other hand, defrosting was sometimes not necessary at all. Defrosting is induced fully automatically via the QKL-Mini 2 cooling controller. The controller operates through latent-heat management and initiates the defrosting process at the most energy-efficient time, as required. The system allows for fluctuating temperature differences. Depending on the degree of frosting on the
evaporators, the QKL-Mini 2 recognizes when defrosting is required and then utilizes the residual heat of the evaporator coils.
“The calculated savings potential with this plant configuration, as compared to conventional compressor frequency control and conventional time-based defrosting, is in the region of 20 % to 25 %” says Friess-Becker. Since some fruit and vegetables must be stored at a relative humidity of up to 98 % (e.g., asparagus), Friess- Becker specifically selected the SGB50-F62 high performance evaporators from the Küba Blue Line. The evaporators are designed for long service life and boast
a high cooling surface – a decisive criterion in case of heavy frost formation.
Optimal air circulation with even frosting of the fins guarantees quick and even cooling. This, in turn, prevents moisture loss in the refrigerated goods. The few and short defrosting phases ensure constant ambient temperature without major fluctuations. The sensitive produce therefore remains fresh for longer and thus retains its flavor and appearance.
The Munich market hall is a cultural asset and a global meeting point of the fruit and vegetable sector. A total of 3,000 work there. On 310,000 m² , 270 import and wholesale companies turn over 140 produce types from 83 countries – amounting to more than 750 million euros. This is in addition to 65 businesses for gardening products, 45 florists, and 15 wholesalers from other sectors. The total annual turnover is approx. 1.5 billion euros on the balance sheet. The distribution area of the market is also “unlimited”: it supplies a region with about 5 million people daily and provides produce to all foreign European countries.