Container Freezer Air Control Using Staged Nitrogen Supply
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Solution Overview
Problem
The existing inside air control system for container refrigeration apparatuses produces nitrogen-enriched air with a high oxygen concentration initially, which gradually decreases, resulting in an average oxygen concentration that cannot be effectively controlled to be lower than the produced nitrogen-enriched air, leading to inadequate oxygen reduction in the container.
Innovation Solution
The system alternates between adsorption and desorption operations in adsorption columns to produce nitrogen-enriched air with a lower oxygen concentration, and performs a partial supply operation where nitrogen-enriched air produced after the initial high-oxygen phase is discharged, ensuring only air with a lower oxygen concentration is supplied to the container, and adjusts the supply based on oxygen concentration and amount to achieve the desired reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the whole nitrogen-enriched air produced during desorption operation is supplied into the container, then the supply operation is simple and continuous, but the oxygen concentration of the supplied air averages to a medium level, preventing effective oxygen reduction in the container
Solution Approach 1:
The nitrogen-enriched air supply is segmented into two distinct phases: a first period where air is discharged to the outside, and a second period where air is supplied to the container. This segmentation allows the system to exclude the high-oxygen portion of the air stream while capturing the low-oxygen portion, thereby resolving the contradiction between operational simplicity and oxygen concentration control.
Solution Approach 2:
The system performs a preliminary discharge action before the supply action. By discharging the nitrogen-enriched air to the outside during the first period, the system preliminarily removes the high-oxygen air that would otherwise contaminate the container air, enabling subsequent supply of lower-oxygen air during the second period.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise control of oxygen concentration in the container, ensuring it remains lower than the average oxygen concentration of the produced nitrogen-enriched air, effectively maintaining a desired level of freshness for stored plants.
Implementation Method 1
an adsorbent which adsorbs a nitrogen component in the air when pressurized is used to produce nitrogen-enriched air having a lower oxygen concentration and a higher nitrogen concentration than the air
Implementation Method 2
performs a desorption operation of sucking the air using the air pump from the adsorption column to allow the adsorbent to desorb the nitrogen component adsorbed
Data Source
AI summary
Disclosed herein is a CA system which allows first and second adsorption columns to alternately perform an adsorption operation and a desorption operation so that nitrogen-enriched air having a higher nitrogen concentration and a lower oxygen concentration than the air is produced and supplied into the container. The CA system executes a second operation mode in which the nitrogen-enriched air produced for a predetermined time since the desorption operation was started is discharged to the outside of the container, and the nitrogen-enriched air produced until the end of the desorption operation since the predetermined time passed is supplied into the container.