Supply air discharge for a refrigerated container
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Solution Overview
Problem
Refrigeration systems in cargo containers face significant temperature fluctuations due to the on/off cycling of compressors, which can damage temperature-sensitive cargo and are inefficient, as they often rely on costly variable speed or digital compressors to maintain precise temperatures.
Innovation Solution
A refrigeration system that utilizes a mixing chamber to blend return airflow with supply airflow, reducing temperature fluctuations by injecting return airflow into the mixing chamber synchronously with compressor operation, and using a compressor cycled only in 'on' or 'off' positions to maintain consistent temperatures without variable speeds or modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a variable speed compressor is used to control supply air temperature, then temperature control precision is improved, but device complexity and cost increase
Solution Approach 1:
A mixing chamber is introduced as an intermediary component between the compressor and the cargo hold. The mixing chamber blends cooled air from the evaporator with warmer air from the cargo hold, allowing precise temperature control without requiring complex variable speed compressor control systems. This mediator approach simplifies the overall system while achieving the desired temperature precision.
2Device complexity
If compressor cycling is used to operate the refrigeration system, then device complexity is reduced, but temperature stability deteriorates
Solution Approach 1:
The mixing chamber is pre-configured with air mixing capabilities and return air pathways are established before temperature fluctuations occur. When the compressor cycles on or off, the mixing chamber immediately blends the discharged air with return air to compensate for temperature variations, preventing temperature instability before it affects the cargo hold.
3Stability of the object's composition
If return airflow is injected into the mixing chamber synchronously with compressor operation, then temperature fluctuation is reduced, but energy consumption increases
Solution Approach 1:
The return air injection is implemented as a periodic action synchronized with the compressor cycle. The fan operates intermittently, injecting return air only during specific phases of the compressor cycle when temperature stabilization is most needed. This periodic operation reduces overall energy consumption compared to continuous fan operation, while still achieving temperature fluctuation reduction.
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 temperature fluctuations within the container, protecting sensitive cargo and improving efficiency by eliminating the need for costly compressor modulation, thereby ensuring consistent and stable temperatures while reducing operational costs.
Implementation Method 1
A refrigeration system that utilizes a mixing chamber to blend return airflow with supply airflow
Data Source
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AI summary
A transportation cargo refrigeration system includes a refrigeration unit to provide a flow of supply air for a refrigerated cargo container. A refrigeration system outlet allows the flow of supply air into the cargo container. A mixing chamber is located between the refrigeration unit and the refrigeration system outlet for mixing of the flow of supply air thereby reducing supply air temperature fluctuation at the refrigeration system outlet. A method of operating a refrigeration system for a refrigerated cargo container includes flowing supply air through a refrigeration unit thereby reducing a temperature of the supply air. The supply air is directed into a mixing chamber and mixed in the mixing chamber until a selected supply air temperature is achieved. The supply air is directed through a refrigeration system outlet and into an interior of a cargo container.