temperature interference from the various surrounding materials.

It became evident that the strip curtain

• The extractor air volume( 12.94m ³/ s) exceeds the fresh air supply( 5m ³/ s). This FA value was provided by Viking

Also( as witnessed on several occasions), the plastic doors are often left ajar and the strip curtains draped over the doors

independent report on the effectiveness

does indeed offer zone separation;

based on the existing installed units.

or shelving, since both the doors and

of air curtains as opposed to strip curtains

nevertheless, the separation is not as

• The air volume entering through the

the plastic strips are an obstacle when

on all the openings of a supermarkets’

effective, because warm air continues

main entrance doors is estimated at

passing the doorway, especially when

bakery cold and freezer rooms.

to enter the cold room at ceiling level,

9m ³/ s [( 2.5m x 2.5m) x 1.44m / s)].

transporting goods. An air curtain would

Systemair installed a complete air curtain

with cold air losses at floor level being

• Most of the air curtains in the store

provide a definite thermal barrier— even

solution at a Gauteng supermarket to both

unacceptably high. These losses add

were switched off.

when the door is open and loading

reduce current energy consumption and

additional load to the refrigeration system,

• The extractor and canopy fans run

is taking place— resulting in a more

improve indoor temperature for not only

as well as added defrost cycles in an

continuously.

even and controlled temperature being

the store itself, but also cold and freezer

attempt to eliminate excessive ice build‐up

maintained within the rooms.

rooms. The entire store was fitted with

on the evaporator coils in the room.

Conclusion

The general store area is currently

Frico / Systemair air curtains, as well as door

To minimise the losses through cold and

operating at a negative pressure level

switches on all the openings to reduce the

Note: At the time of arrival the strip curtain

freezer room doors, and furthermore

as a result of the imbalance between

air curtain running time.

was draped over the door while loading

to ensure a controlled climate in these

the supply of fresh air and the extracted

As a comparison, the bakery cold room

was in progress, which could explain the

refrigerated rooms, the door openings

air volume. For the air curtains to

and freezer room doors weren’ t changed,

high room temperature. This would not

need to be sealed. At present this is done

maintain the necessary thermal barrier

so the strip curtains— still in good condition

have been the case had an air curtain

with plastic strip curtains and lightweight

between internal and external zones, it is

— were left intact.

been installed.

plastic doors.

imperative that the extracted and fresh

Tests were conducted on site by means

air supply are balanced. Introduction of

of a smoke machine to evaluate the zone separation of the air curtains on all the openings. These tests were, however, inconclusive as the zone separation could not be measured. After discussions with the technical department in Sweden and further onsite inspection, it was decided to measure the zone separation by means of

Entrance / receiving doors

• Inconclusive readings at the time of testing due to no / minor temperature difference between the inside and outside temperature.

• Receiving doors and hatches protected by single air curtains.

• Entrance protected by double air

An air curtain will provide a definite thermal barrier, even when the door is open and loading is taking place, resulting in a more even and controlled temperature being

the shortfall will balance the system. It is recommended that this be introduced at the extractor canopies so as not to add additional load to the existing airconditioning system.

Systemair / Frico AB remain confident in their air curtains to provide significant energy savings at this test installation. CLA

a thermal camera.

curtains.

• Note: An air velocity of 1.44m / s was

maintained within the rooms.

General info

• Ambient temperature 19.7 ° C

• Minimum temperature ‐6.0 ° C

• Maximum temperature 21.3 ° C

A bare polystyrene sheet ± 1 500mm wide by the full door height, was placed in the doorway against the door sill to provide a neutral background and limit the

measured coming into the store through the main entrance, equivalent to 9m ³/ s.

Summary of findings

• The store air-conditioning system was switched off at the time of the visit, and the extractor fans and canopies were all operational.

Even though these doors and plastic strip curtains work well— provided they are intact— they are delicate and easily damaged. Therefore, to prevent functionality losses due to damage, they need frequent maintenance in the form of repair and replacement, which is costly in the long run.

1. An independent study was conducted to test the effectiveness of air curtains as opposed to strip curtains on all the openings of a supermarket’ s bakery cold and freezer rooms.

2. The study found the air curtains to be more effective than the strip curtains.

3. An air curtain will provide a definite thermal barrier, even when the door is open.