Variable-Frequency Refrigeration Drive for Faster Set Point Recovery
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Solution Overview
Problem
Traditional transportation refrigeration units have fixed speed operations for components like compressors and fans, leading to inefficient power consumption and longer recovery times for temperature set points, especially when dealing with varying cargo compartment conditions.
Innovation Solution
A drive unit that delivers electrical power in a variable frequency range of 35 Hz to 65 Hz, controlled by a unit connected to sensed parameters such as cargo compartment temperature and door position, allowing continuous adjustment of power to match cooling demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If fixed speed operation is used for compressors and fans, then system simplicity is maintained, but power consumption efficiency deteriorates and set point recovery time increases
Solution Approach 1:
The patent applies the dynamics principle by transforming the fixed speed operation into variable speed operation. The drive unit receives variable frequency electrical power (35 Hz to 65 Hz) that continuously adjusts the operating speed of the compressor and condenser fan based on real-time cooling demands. This dynamic adjustment allows the system to optimize power consumption efficiency while reducing set point recovery time by increasing speed when rapid cooling is needed.
Solution Approach 2:
The patent implements parameter changes by varying the operating frequency parameter of the compressor and fan motors. The drive unit changes the frequency of electrical power from a fixed value to a variable range (35 Hz to 65 Hz), allowing continuous optimization of both power consumption efficiency and cooling response time based on cargo compartment temperature conditions.
2Productivity
If variable speed operation is implemented, then power consumption efficiency and set point recovery time improve, but system complexity increases
Solution Approach 1:
The patent applies the merging principle by integrating the variable speed control functionality into a single drive unit that receives electrical power from the vehicle's powertrain. Instead of adding separate complex control systems for the compressor and fan, the invention combines their speed control through one unified drive unit responsive to frequency-varying electrical power, thereby improving cooling efficiency while minimizing the increase in system complexity.
Solution Approach 2:
The drive unit serves multiple functions: it controls both the compressor and condenser fan speeds, responds to varying cooling demands, and interfaces with the vehicle's existing electrical power system. This multi-functionality allows the system to achieve variable speed operation and improved productivity without requiring separate dedicated control systems for each component.
3Loss of energy
If fixed power delivery is used, then system simplicity is maintained, but fuel efficiency and CO2 emissions deteriorate
Solution Approach 1:
The patent implements feedback by making the drive unit responsive to varying electrical power frequency that reflects real-time cooling demands. The system continuously adjusts power delivery based on cargo compartment temperature conditions, ensuring optimal fuel efficiency and reducing CO2 emissions by avoiding unnecessary energy consumption while maintaining relatively simple power delivery system architecture.
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 solution reduces set point recovery times, improves efficiency and fuel efficiency of the vehicle engine, and decreases CO2 emissions by optimizing power delivery based on real-time conditions, while simplifying the system by avoiding the need for complex variable speed components.
Implementation Method 1
The drive unit 30 is connected to the vehicle engine 28 such that the drive unit 30 converts rotational energy from the vehicle engine 28 into electrical power
Data Source
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Figure 2
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AI summary
A transportation refrigeration unit for cooling a cargo compartment includes a compressor configured to compress a refrigerant, a compressor motor configured to drive the compressor, an evaporator heat exchanger operatively coupled to the compressor and an evaporator fan configured to provide return airflow from a return air intake and flow the return airflow over the evaporator heat exchanger. A drive unit is configured to deliver variable frequency electrical power between a minimum frequency and a maximum frequency to the compressor motor and the evaporator fan. A frequency of the electrical power is based on one or more sensed parameters of the transportation refrigeration unit.