Combined Cold Store Dehumidification Reducing Defrost Cycle (Food Related)
- No More Ice Accumulation Within Cold Store
- Clear and Dry Loading Bay
- Greatly Reduced Maintenance and Defrost Cycles
- Lucrative Payback
ROFLOW and Munters have teamed up once again and impressively enhanced cold store operation at WM Morrisons’ Distribution Centre in Bells Hill, Glasgow. The site is one of the supermarkets’ five UK Distribution centres in which supply their 400 stores throughout Great Britain. The vast premises offer intermittent storage of packaged goods before being transferred to the shelves of their familiar shops to be bought by the general public.
As air gets cooler, the amount of moisture in which it can hold reduces; thus, when humid air is cooled, there comes a point in which the air can no longer hold the moisture it contains and rejects it in the form of condensation. Within the sub-zero cold store, frost build up occurs due to the infiltration of humid air via the entrances and apertures of the freezer and condensing on the cold surfaces. The freezer contains doorways to both internal areas as well as external loading bays for lorries.
Measures are already taken to mitigate infiltration during the traffic of people and products in and out of the cold store such as airlocks, strip curtains and dock seals however frost build up is still inevitable and can not be effectively controlled with such measures.
SYSTEM 1 – LOADING BAYS
The loading bays are chilled to a temperature of around 0⁰C to – 4 ⁰C and are the most susceptible area to infiltration. The annual average relative humidity of outside air in Glasgow is around 79%, and when it comes into contact with the evaporator coils and cold surfaces of the walls and ceiling, condensation occurs and causes wet floors and visibility hindering fog as well as ice build-up around door entrances (See Fig 1.).
The system incorporates a Munters MLT 1400 Unit and decelerates the rate of condensation and frost build up by providing a strategically localised delivery of dry air to the evaporator coil whilst simultaneously extracting and expelling the saturated air from around the external loading doorway to atmosphere (See Fig 2. & Fig 3.). In doing so, this greatly reduces the average humidity across the coil thus subduing the frost accumulation. The system has also effectively eliminated the occurrence of fogging and wet floors.
SYSTEM 2 – COLD STORE
The actual cold store itself is maintained at a steady state of around – 25 ⁰C. The freezer contains 5 No. large evaporators at the far end of the cold store opposite the three doors leading to the loading bays. Frequent movement in and out the cold store and the subsequent humidity gain causes ice to form on the walls, ceiling, floor, and door entrances not to mention visibility reducing mist and fog (see Fig 4.).
The solution was to install 3 No. Ice Dry 1400 units and to supply the dry air directly over the door entrances (see Fig 5.). As a result of the installation of this system, ice build up within the cold store has effectively been eliminated and the maintenance and defrost requirement on the evaporators greatly reduced. Fogging at the doorways has also been subdued.