How To Avoid Hot Spots in Fruit Ripening?

How to Avoid Hot Spots in Fruit Ripening Rooms

Hot spots happen because air cannot reach or circulate evenly through every box. Fix airflow first, then temperature control.

1. Use a Pressurized / Forced-Air System (Most Important)

Standard coolers blow air over fruit boxes.Pressurized systems push air through the boxes.

Install high-static unit coolers (250–400 Pa)

Use ducting / plenums to distribute air evenly

Air must flow top → down → through pallets → floor return

This alone removes 80% of hot spots.

2. Perfect Pallet & Box Spacing

Do NOT stack boxes tightly together.

Leave 10–15 cm gap between pallet rows

Leave 10 cm gap from walls

Leave 80–120 cm from air cooler outlet

Align boxes so air can flow through vents (not blocked)

Boxes with blocked ventilation = guaranteed hot spots.

3. Even Airflow Distribution

Use adjustable air deflectors to spread air wide

Balance airflow so left/right/front/back are equal

For large rooms: install 2 or more coolers on opposite walls

Avoid blowing cold air directly at fruit (causes cold spots)

4. Correct Air Changes Per Hour (ACH)

For ripening rooms:

40–80 ACH for uniform temperature

Fans run 24/7 continuously (not just when cooling)

Fans off = hot spots form within 30 minutes.

5. Proper Temperature Control Strategy

Set room temp 15–18°C for mango

Set room temp 14–16°C for banana

Use PID controllers (±0.3°C accuracy)

Avoid big temperature swings

Coil temperature not too low (prevents over-cooling)

6. Avoid These Common Mistakes

Overloading the room → air can’t circulate

Uneven stacking height → air flows over top

Boxes touching walls/ceiling → dead zones

Fans too weak / low static → no penetration

Dirty coils / filters → weak airflow

Single cooler in a large room → uneven coverage

7. Use Multiple Sensors to Monitor

Place temperature sensors at:

Near cooler

Far corner

Middle of room

Bottom & top of pallets

If any sensor differs by >1°C, you have a hot spot.

8. Room Design That Prevents Hot Spots Automatically

Ceiling-mounted coolers

Floor return air path

PU insulated panels (no heat leakage)

Air locks / proper door seals

No pillars or obstacles in air path