Refrigerator's Air Curtain - energy saving

Horizontal Air Curtain:

minimizing food waisting

• The act of opening the refrigerator door push some fresh cool air out, noticed by someone feet who’s shoeless

• An ice transportting truck, while loading/unloading: cool air leaking

• Bar refrigerator with top termometer. It’s value it’s rapidly increased when the door is opened.

• Reason: density diference due to air temperature diference.

Cool air has higher density then warm or hot air. Being cool air inside the refrigerator chamber, it leaves it to make room for warm air, heating food and reducing preservation time.

Observed Facts:

Refrigerator wih closed door. Whole interior with cool air.

Short period door openning time: cool air leaving the chamber.

Long period door openning time: cool air completely wasted.

Observed Facts:

• With warm or hot air inside the chamber, food is quickly heated.

• Eventhought being a short period heating, there’s remarkable consequences: food reduces it’s preservation time.

• With the increasing number of single living people houses, the same milk liter will now take longer time to be consumed in comparison with a house where a whole family lives. -> lot of unnecessary food waisting !!

Consequences:

• In a hot summer day, a 15 seconds oppening time pushed the compressor to work up to 170% addicional time then a closed door pattern.

Door opening: internal temperature expectations:

(tests over domestic refrigerator)

• Operation Range, closed door: 2 C 6 C

• Operation time without opening the door: 8 min

• From 6 C to 2 C in 8 min = 0,5 C / minute

• Door opening in a hot day, compressor runs for 22 minutes.

• 22 minutes in 0,5 C/min = compressor beats a 11 C internal temperature diference, total 13 C internal peak temperature with single door opening.

• Efects:

• In food, degradation accelerared

• Beverages: continuous temperature change can promote caracteristics variation.

• In both: unnecessary energy losses

Testing the energetic losses:

Horizontal Air Curtain made by exhaust and sucction air nozzles, instaled in the door knocker.

Solution proposal:

Does it work??

Solution proposal:

Prototype:

Obs: prototype project did not predicted installing in-wall tubulation. In final product conception, it would be only notable a little bit thicker wall.

Test to evaluate the effects of door opening as a function of the door opening time.

Testing the energetic losses:

Opened door for X seconds:

Testing the energetic losses:

• Reduces hot load infiltration.

• Maximizes the no-perish food storage time.

• Weaker compressors and smaller heat exchange area for the same load: lower production costs.

Advantages:

• Reduces the after door opening compressor running time: saves energy.

• Comercial refrigerator (0 a -6 C) - Chamber: 497L

- Compressor power: 580 w

One refrigerator in a comercial store (opened 16h/day), door opened 70 times/day.

• With obtained eficiency, 13%, 2% in electrical energy saved.

• If optimized eficiency of 30%, 4% in electrical energy saved.

• Best scenario: 65% air curtain eficiency, 7,6% in electrical energy saved.

Energy Economy estimation:

• Energy cost (Brasil currency): R$0,45/kWh

• R$16,45/month economy.

• 36,56 kWh/month economy

• Lighting consume in a 100m² comercial office: 320kWh/month

• For a air curtain eficiency of 65%

• In 5 years, R$987,20 economy (deflated)

• 2193,75 kWh/5 years economy

• In a five years air curtain operation, one refrigerator saves enouth to run the office light for 6,8 months.

Energy Economy estimation:

In domestic refrigerator, internal peak temperature after door opening was about 13 C, without air curtain technology.

• With reached eficiency, 13%, internal peak temperature of 8 C

• If optimized eficiency of 30%, 6,9 C of i.p.temperature.

• Best scenario: 65% air curtain eficiency 4,45 C (assuming a 2 C internal temperature at the moment of the door opening).

Internal temperature estimation:

• Patent requested

• In wide spread use can save big amounts of energy and food, a big sustainable gain.

Actual state:

• Talking to refrigerator manufacturer and government.

• Trying to spread the knowledge for the masses, so the people can ask their manufacturer for the tecnology and antecipate food and energy saves.

Thank you.

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