Articles
Optimising citrus Opentop cartons for efficient container cooling and minimal bottom sag
Article number
1396_57
Pages
435 – 440
Language
English
Abstract
The South African citrus industry recently designed and implemented a high-ventilation A15C telescopic carton that significantly improves cooling performance during shipping.
This carton allows the industry to ship chilling-injury-sensitive citrus fruit at more uniform temperatures using higher set points.
However, citrus fruit packed in Opentop (display) cartons does not have access to similarly set points.
The studys aim was thus to design an Ultravent Opentop carton with an equivalent porosity to the new A15C carton.
However, the main challenge is overcoming bottom sag displacement due to the loss of structural strength as the vent size increases along the bottom wall of the carton.
Finite-element analysis was applied to identify optimal vent hole positioning.
The resistance to airflow (inverse of cooling rate) was evaluated using a custom-built wind tunnel.
The mechano-sorptive creep (bottom sag) was tested experimentally for each carton design by loading carton stacks with 19.5-kg water bags and placing them in cold storage (0°C, ~95%) for 28 days.
Key findings indicate that a vent area of 28000 mm2 is needed to reach the desired resistance of 2000-2500 kg m-4. Bottom sag displacement was significantly higher for the Ultravent cartons (35.5±4.5 mm) compared to Standard Opentop (26.0±3.0 mm) and No-vent (23.3±2.8 mm) designs.
However, slightly increasing the board strength, significantly reduced bottom sag when applying the Ultravent ventilation design.
The study showed the Ultravent has a comparable porosity to the new A15C carton and is mechanically viable for commercial export.
This carton allows the industry to ship chilling-injury-sensitive citrus fruit at more uniform temperatures using higher set points.
However, citrus fruit packed in Opentop (display) cartons does not have access to similarly set points.
The studys aim was thus to design an Ultravent Opentop carton with an equivalent porosity to the new A15C carton.
However, the main challenge is overcoming bottom sag displacement due to the loss of structural strength as the vent size increases along the bottom wall of the carton.
Finite-element analysis was applied to identify optimal vent hole positioning.
The resistance to airflow (inverse of cooling rate) was evaluated using a custom-built wind tunnel.
The mechano-sorptive creep (bottom sag) was tested experimentally for each carton design by loading carton stacks with 19.5-kg water bags and placing them in cold storage (0°C, ~95%) for 28 days.
Key findings indicate that a vent area of 28000 mm2 is needed to reach the desired resistance of 2000-2500 kg m-4. Bottom sag displacement was significantly higher for the Ultravent cartons (35.5±4.5 mm) compared to Standard Opentop (26.0±3.0 mm) and No-vent (23.3±2.8 mm) designs.
However, slightly increasing the board strength, significantly reduced bottom sag when applying the Ultravent ventilation design.
The study showed the Ultravent has a comparable porosity to the new A15C carton and is mechanically viable for commercial export.
Authors
T. Berry, H. Geldenhuys, S.-H. Chung, M. Kleyn, P. Cornje
Keywords
packaging design, airflow resistance, carton strength, mechano-sorptive creep, cooling performance, citrus fruit
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