Controlling chilled state of a cargo
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Solution Overview
Problem
Existing refrigeration systems in cargo containers face challenges in efficiently maintaining temperature-sensitive cargo within precise temperature ranges, particularly in balancing heating and cooling requirements to minimize energy consumption and prevent cargo degradation.
Innovation Solution
A refrigeration system with a compressor, condenser, evaporator, and evaporator fan, controlled by sensors to determine and adjust heating or cooling needs based on air temperature differences, using variable fan speeds and power adjustments to optimize energy use and prevent ice buildup, which degrades efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the evaporator fan speed is increased to improve air circulation and cooling efficiency, then the refrigeration effectiveness is improved, but the energy consumption increases and ice buildup risk increases
Solution Approach 1:
The evaporator fan operates at variable speeds rather than a fixed speed, allowing the system to dynamically adjust fan rotation based on actual refrigeration needs. The controller modulates fan speed to match the cooling demand, improving efficiency while preventing excessive energy consumption and ice buildup.
Solution Approach 2:
The system uses temperature sensors to continuously monitor conditions and provide feedback to the controller, which then adjusts the evaporator fan speed accordingly. This closed-loop control ensures the fan operates at the optimal speed for current conditions, balancing refrigeration effectiveness with energy efficiency.
2Power
If the compressor power is increased to meet higher cooling demands, then the refrigeration capacity is improved, but the energy consumption increases
Solution Approach 1:
The compressor operates at variable power levels rather than a fixed high power setting. The controller dynamically adjusts compressor power based on actual cooling demands detected by temperature sensors, allowing the system to provide high refrigeration capacity when needed while consuming minimal energy during lower demand periods.
Solution Approach 2:
The system changes the operating parameters of the compressor (power level, rotation speed) based on detected temperature conditions. By modulating these parameters rather than operating at constant high power, the system achieves high refrigeration capacity when required while minimizing energy consumption during milder conditions.
3Manufacturing precision
If the evaporator fan speed is increased to prevent temperature rise, then the temperature control is improved, but ice buildup occurs which degrades efficiency
Solution Approach 1:
The evaporator fan speed is dynamically adjusted based on temperature sensor feedback rather than operating at maximum speed continuously. This dynamic control maintains precise temperature control when needed while reducing fan speed during periods when lower cooling is required, thereby preventing ice buildup that would degrade efficiency.
Solution Approach 2:
Temperature sensors provide continuous feedback to the controller, which adjusts the evaporator fan speed to maintain the desired temperature range. This feedback control prevents both temperature rise and excessive cooling that would cause ice buildup, maintaining both temperature precision and system efficiency.
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
The system effectively maintains cargo at set-point temperatures with minimal energy consumption, ensuring the freshness of chilled commodities by dynamically adjusting fan speeds and compressor power to meet varying refrigeration and heating demands.
Implementation Method 1
an evaporator fan associated with the evaporator... The evaporator fan is operable to discharge supply air to the container and to receive return air from the container
Implementation Method 2
The vapor-compression cycle is used in most household refrigerators as well as in many large commercial and industrial refrigeration systems
Implementation Method 3
a condenser, and an evaporator connected in series
Implementation Method 4
an evaporator connected in series... sensors configured to sense the temperature of the supply air and the temperature of the return air
Data Source
AI summary
A method for operating a refrigeration system for a container for refrigerating chilled cargo includes providing a refrigeration system including a compressor and an evaporator fan associated with an evaporator. The method also includes determining the temperature of supply air and the temperature of return air. The method further includes determining one of a requirement for heating and a requirement for cooling based on the temperature of the return air and the temperature of the supply air. The method additionally includes activating the evaporator fan when a requirement for heating is determined and increasing the speed of the evaporator fan when increased heating is determined. The method also includes activating the compressor and the evaporator fan when a requirement for cooling is determined and increasing the power supplied to the compressor and maintaining the evaporator fan at a first speed when increased cooling is determined.