Variable-Frequency Refrigeration Unit for Cargo Temperature Control
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Solution Overview
Problem
Traditional transportation refrigeration units in vehicles have fixed speed operation for components like compressors and evaporator fans, leading to inefficient temperature control and increased fuel consumption, as they cannot adjust power delivery based on changing cargo compartment conditions.
Innovation Solution
A drive unit that provides variable frequency electrical power to the compressor motor and evaporator fan, ranging from 35 Hz to 65 Hz, based on sensed parameters such as cargo compartment temperature and door position, allowing for continuous adjustment of power delivery to maintain optimal cooling conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed speed operation is used for compressor and evaporator fan, then device complexity is reduced, but temperature control efficiency deteriorates and fuel consumption increases
Solution Approach 1:
The patent applies dynamics by transitioning from fixed speed operation to variable speed operation of the compressor and evaporator fan. The compressor motor and fan motor speeds are continuously adjusted based on sensed cargo compartment temperature and other operating parameters, allowing the system to adapt to changing conditions and optimize temperature control efficiency without requiring complex mechanical variable speed components.
Solution Approach 2:
The patent changes the operational parameters of the compressor and fan motors by controlling their speed through electrical power frequency adjustment (35-65 Hz range). This parameter change enables continuous optimization of cooling performance and fuel efficiency by matching compressor and fan speeds to actual cargo compartment cooling requirements rather than operating at constant fixed speeds.
2Device complexity
If fixed speed operation is used for compressor and evaporator fan, then device complexity is reduced, but fuel consumption increases
Solution Approach 1:
The system dynamically adjusts compressor and fan motor speeds based on actual cooling requirements, preventing energy waste from operating at constant high speeds when full cooling capacity is not needed. This dynamic adaptation reduces fuel consumption by matching power delivery to actual cargo compartment temperature conditions.
Solution Approach 2:
By changing the electrical power frequency delivered to motors (35-65 Hz range), the system optimizes motor operating parameters to reduce energy consumption. The variable frequency control allows motors to operate at optimal efficiency points across different loading conditions, significantly reducing overall fuel consumption compared to fixed speed operation.
3Productivity
If variable frequency electrical power is provided to compressor motor and evaporator fan, then temperature control efficiency is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical variable speed drive systems with electrical frequency control of motor operation. Instead of using mechanical transmissions, belts, or clutches to vary speeds, the system uses electronic frequency control of the electrical power supplied to motors, achieving variable speed operation with simpler electrical control components rather than complex mechanical variable speed mechanisms.
Solution Approach 2:
The drive unit serves multiple functions: it generates electrical power from the vehicle engine, converts it to variable frequency AC power, and distributes it to multiple motors (compressor motor, fan motor) simultaneously. This multi-functional approach consolidates what would otherwise require separate speed control systems for each motor, reducing overall device complexity while maintaining temperature control efficiency.
4Use of energy by moving object
If variable frequency electrical power is provided to compressor motor and evaporator fan, then fuel efficiency is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical power transmission and speed control systems with an electrical generation and frequency control system. The drive unit converts mechanical power from the vehicle engine directly to variable frequency electrical power, eliminating the need for mechanical variable speed transmissions and reducing overall system complexity while improving fuel efficiency through optimized motor operation.
Solution Approach 2:
The drive unit consolidates multiple functions into a single system: electrical power generation, frequency conversion, and distribution to multiple motors. This multi-functional integration achieves fuel efficiency improvements through variable speed control without requiring separate complex control systems for each motor, thereby limiting the increase in overall device complexity.
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 refrigeration unit efficiency, and enhances fuel efficiency and reduces CO2 emissions by allowing precise power adjustments, eliminating the need for complex variable speed components.
Implementation Method 1
an electrical generator operably connected to a vehicle engine
Implementation Method 2
a compressor motor configured to drive the compressor
Implementation Method 3
an evaporator fan configured to provide return airflow from a return air intake and flow the return airflow over the evaporator heat exchanger
Implementation Method 4
an evaporator heat exchanger operatively coupled to the compressor
Data Source
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.