Refrigerated Container Oxygen Control Using Nitrogen-Oxygen Gas Mixing
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Solution Overview
Problem
Existing container refrigeration systems face challenges in maintaining a stable oxygen concentration, leading to respiratory disorders and deterioration of plants due to excessive variation in oxygen levels, particularly when using nitrogen gas to reduce oxygen concentration.
Innovation Solution
A container refrigeration apparatus equipped with an oxygen concentration detector and a gas mixture supplier that adjusts the oxygen levels by providing a gas mixture with a higher nitrogen and lower oxygen concentration than outside air, allowing the system to maintain target oxygen concentrations through controlled supply and respiration processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitrogen gas is supplied to reduce oxygen concentration in the container, then the oxygen concentration can be lowered to maintain plant freshness, but the magnitude of variation in oxygen concentration increases causing excessive decrease and making it difficult to maintain target concentration
Solution Approach 1:
The patent changes the parameter of gas composition by using a gas mixture containing oxygen (e.g., 2-10% oxygen) instead of pure nitrogen. This modification of the supplied gas parameters allows oxygen concentration reduction while preventing excessive decrease, as the oxygen in the mixture compensates for plant respiration and prevents large fluctuations.
Solution Approach 2:
The patent implements a feedback control system where an oxygen concentration detector continuously monitors the container's oxygen level and provides signals to a controller. The controller adjusts the gas mixture supply rate based on this feedback, ensuring the oxygen concentration remains near the target value without excessive variation.
2Duration of action of stationary object
If oxygen concentration is reduced to maintain plant freshness, then respiration rate decreases extending shelf life, but plants may develop respiratory disorders if oxygen becomes too low
Solution Approach 1:
The patent modifies the gas supply parameters by using a controlled oxygen-containing mixture rather than pure nitrogen. This allows the oxygen concentration to be reduced to levels that slow respiration and extend freshness while maintaining it above the threshold that would cause respiratory disorders.
Solution Approach 2:
The patent provides beforehand cushioning by supplying oxygen along with nitrogen in the gas mixture. This preemptive measure ensures that even as oxygen is consumed by plants, the concentration remains sufficient to prevent respiratory disorders while still achieving the desired freshness extension.
3Productivity
If high nitrogen concentration gas is supplied to quickly reduce oxygen, then oxygen concentration decreases rapidly improving freshness maintenance, but the variation in oxygen concentration becomes too large causing control difficulty
Solution Approach 1:
The patent changes the composition parameters of the supplied gas from pure nitrogen to an oxygen-containing nitrogen mixture. This allows rapid oxygen concentration reduction through nitrogen displacement while the oxygen component prevents excessive depletion, maintaining control precision.
Solution Approach 2:
The patent uses feedback control where the oxygen concentration detector and controller work together to monitor and adjust the gas mixture supply rate. This ensures rapid reduction when needed while preventing excessive variation, achieving both high productivity and precision.
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 reduces the magnitude of oxygen concentration variation, effectively maintaining the oxygen level near the target concentration, thereby preventing plant deterioration and improving freshness.
Implementation Method 1
an oxygen concentration detector (51) which detects an oxygen concentration in the interior of the container (11)
Implementation Method 2
a gas mixture supplier (30) which supplies the interior of the container (11) with a gas mixture having a higher nitrogen concentration and a lower oxygen concentration than outside air
Implementation Method 3
the oxygen concentration in the interior of the container (11) is reduced to the target concentration by respiration of the plants (15) absorbing oxygen in the air and releasing carbon dioxide into the air
Data Source
AI summary
An oxygen concentration in the interior of a container is detected by an oxygen concentration detection sensor. If the oxygen concentration detected by the oxygen concentration detection sensor is higher than that of a gas mixture, the container is supplied with the gas mixture having an oxygen concentration lower than that of the outside air and higher than a target concentration. The oxygen concentration in the interior of the container is reduced to the vicinity of the oxygen concentration of the gas mixture by supplying the interior of the container with the gas mixture, and then is further reduced to the target concentration by respiration of plants. This appropriately controls the oxygen concentration in the interior of the container, and reduces a decrease in the degree of freshness of the plants.