Reefer Container Airflow Control for Chilled Cargo Temperature

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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 while ensuring cargo freshness and safety.

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 efficiency degradation from ice buildup.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If conventional refrigeration systems continuously operate the compressor and evaporator fan to maintain cargo temperature, then the cargo temperature is maintained within acceptable range, but energy consumption increases significantly

Engineering Contradiction:

Improvecargo temperatureVSAvoidenergy consumption

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

The system dynamically adjusts the operational state of the evaporator fan and compressor based on real-time temperature monitoring. The evaporator fan operates at variable speeds (high, medium, low) rather than continuous full-speed operation, and the compressor cycles on and off based on temperature thresholds, creating a dynamic control system that adapts to changing thermal conditions to minimize energy consumption while maintaining cargo temperature

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes operational parameters (fan speed levels, compressor on/off state) based on temperature conditions. The evaporator fan has multiple speed settings that are selected based on the temperature difference between cargo and ambient air, allowing the system to optimize energy usage by using lower fan speeds when less cooling is required

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the evaporator fan speed is increased to improve air circulation and prevent ice buildup, then cargo freshness is maintained, but energy consumption increases

Engineering Contradiction:

Improvecargo freshnessVSAvoidfan energy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The evaporator fan operates dynamically with variable speeds rather than continuous high-speed operation. The system monitors temperature conditions and adjusts fan speed accordingly, using high speed only when necessary to prevent ice buildup or when temperature differentials require enhanced air circulation, thereby maintaining cargo freshness while minimizing energy consumption

Inventive Principle:

Principle #15Dynamics

3Speed

If the compressor power is increased to rapidly cool cargo, then the cargo reaches the acceptable temperature range faster, but energy consumption increases

Engineering Contradiction:

Improvecooling speedVSAvoidcompressor energy consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The compressor operates in periodic cycles rather than continuous operation. It turns on when the cargo temperature approaches the upper threshold of the acceptable range and turns off when the temperature reaches the lower threshold, creating a periodic on-off pattern that maintains cargo temperature within the acceptable range while minimizing energy consumption by avoiding continuous high-power operation

Inventive Principle:

Principle #19Periodic action

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 heating or cooling demands, thereby reducing energy waste and maintaining cargo integrity.

Implementation Method 1

proper use of forced air circulation

Methodology Applied

Scientific EffectForced convection: Forced Convection

Implementation Method 2

refrigeration is the process of removing heat from an enclosed space, or from a substance, and moving it to a place where it is unobjectionable

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentUS8607582B2Controlling chilled state of a cargo

Publication Date: 2013.12.17 JOHNSON CONTROLS TYCO IP HLDG LLP

AI summary

A refrigeration system for a container for refrigerating chilled cargo includes a compressor, a condenser, and an evaporator connected in series. The system further includes a heater and sensors configured to sense the temperature of the supply air and the temperature of the return air. A controller is programmed to determine 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 controller is programmed to activate the evaporator fan when a requirement for heating is determined and to increase the speed of the evaporator fan when increased heating is determined. The controller is also programmed to activate the compressor and the evaporator fan when a requirement for cooling is determined and to increase the power supplied to the compressor and maintain the evaporator fan at a first speed when increased cooling is determined.