Container Refrigeration Control During Dehumidification
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Solution Overview
Problem
Container refrigeration devices face issues with non-uniform temperature distribution during dehumidification operations, leading to potential low temperature damage to freight due to temperature sensors detecting average temperatures that may not accurately represent the actual conditions inside the container.
Innovation Solution
The system implements a control mechanism that switches between first and second temperature controls based on the difference between suction air and blown air temperatures, adjusting the target temperature settings to prevent excessive cooling by using correction values calculated from various factors such as outside air temperature and pre-dehumidification air temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If temperature control is based on blown air temperature detected by the temperature sensor, then the temperature control system can maintain simple control logic, but the temperature distribution inside the container becomes non-uniform causing low temperature damage to freight
Solution Approach 1:
The patent divides the temperature control into two independent control loops: one for blown air temperature (using blown air temperature sensor) and one for container internal temperature (using internal temperature sensor). This segmentation allows each sensor to serve its specific purpose without interference, resolving the contradiction between simple control logic and accurate temperature control.
Solution Approach 2:
The patent introduces an intermediary control mechanism that uses the difference between blown air temperature and internal temperature to adjust the heat exchanger operation. This intermediary approach allows the system to compensate for the non-uniform temperature distribution caused by direct blown air heating, thereby preventing low temperature damage while maintaining relatively simple control logic.
2Productivity
If the heat exchanger heats the blown air during dehumidifying operation, then dehumidification effectiveness is improved, but temperature non-uniformity increases causing some areas to become too cold
Solution Approach 1:
The patent applies local quality control by using separate temperature sensors positioned at different locations (blown air path and container interior) to detect temperature conditions in different zones. This allows the control system to account for local temperature variations and adjust heating accordingly, maintaining dehumidification effectiveness while preventing excessive cold in specific areas.
Solution Approach 2:
The patent implements feedback control by continuously monitoring both blown air temperature and internal container temperature, then using this feedback to dynamically adjust the heat exchanger operation. The control system responds to temperature differences in real-time, correcting non-uniform temperature distribution while maintaining effective dehumidification.
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 ensures more accurate temperature control within the container, preventing excessive cooling and subsequent low temperature damage to freight by utilizing the suction air temperature as a more reliable indicator of internal conditions, thereby maintaining a stable environment.
Implementation Method 1
In the evaporator (33), the refrigerant flowing through the evaporator (33) exchange heat with the inside air of the container (C), and accordingly, the inside air is cooled
Implementation Method 2
Thereafter, the refrigerant expands in the expansion mechanism (32), and evaporates in the evaporator (33)
Implementation Method 3
the refrigerant discharged from the compressor (30) condenses in the condenser (31)
Implementation Method 4
the air subjected to the cooling dehumidification in the evaporator (33) exchanges heat with the part of the refrigerant discharged from the compressor (30) and is heated in the reheat heat exchanger (83)
Data Source
Figure 1
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Figure 3
AI summary
A container refrigeration device aims to prevent low temperature damage to freight in a container. The container refrigeration device includes: a temperature controlling section (101) configured to perform, in a switchable manner, first temperature control under which a temperature inside the container (C) is controlled based on a blown air temperature (Tss) and second temperature control under which the temperature inside the container (C) is controlled based on a suction air temperature (Trs) during dehumidification operation; and a control switching section (103) configured to switch the first temperature control to the second temperature control when the blown air temperature (Tss) is higher than the suction air temperature (Trs) during the dehumidification operation in which part of a refrigerant discharged from a compressor (30) is allowed to flow into a reheat heat exchanger (83).