Multi-Zone Refrigeration Control With Variable Compressor Speed
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Solution Overview
Problem
Refrigerant vapor compression systems in transport refrigeration face challenges in efficiently managing cooling demands across multiple temperature-controlled zones with varying set point temperatures, requiring precise control of refrigerant mass flow and compressor speed to maintain product integrity during transport.
Innovation Solution
A method involving a variable speed compression device and liquid flow control valves, controlled by a PI controller with anti-windup and zone volume weighted averaging, to dynamically adjust refrigerant mass flow distribution across multiple zones based on temperature differentials and set point temperatures, ensuring efficient cooling capacity and product temperature maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single compressor is used to serve multiple temperature zones, then device complexity is reduced, but the ability to meet diverse cooling demands of different zones deteriorates
Solution Approach 1:
The patent applies dynamics by making the compressor capacity variable rather than fixed. The compressor speed is dynamically adjusted based on the aggregate cooling demand from multiple temperature zones, allowing a single compressor to adapt its output to match the total cooling requirement while serving different zones with different temperature setpoints.
Solution Approach 2:
The patent changes the operational parameters of the single compressor by varying its speed across a wide range. This parameter change allows the compressor to deliver different cooling capacities to meet the combined demands of multiple zones, effectively replacing what would traditionally require multiple fixed-capacity compressors.
2Power
If refrigerant mass flow is increased to meet peak cooling demand, then cooling capacity is improved, but energy efficiency deteriorates during low load conditions
Solution Approach 1:
The patent implements dynamic adjustment of refrigerant mass flow by varying compressor speed. During peak cooling demand, the compressor operates at high speed to deliver maximum cooling capacity. During low load conditions, the compressor speed is reduced proportionally, maintaining energy efficiency by matching refrigerant flow to actual cooling requirements rather than operating at constant high capacity.
Solution Approach 2:
The system uses feedback from temperature sensors in multiple zones to continuously monitor the aggregate cooling demand. This feedback signals the controller to adjust compressor speed and refrigerant mass flow accordingly, ensuring the system operates at optimal efficiency points across varying load conditions while maintaining adequate cooling capacity when needed.
3Adaptability or versatility
If multiple compressors are used for each temperature zone, then adaptability to zone-specific demands is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies segmentation by dividing the refrigerant distribution system into separate circuits or controllable paths for different temperature zones. While using a single compressor, the system segments the refrigerant flow distribution to serve multiple zones independently, allowing zone-specific temperature control without requiring multiple compressors.
Solution Approach 2:
The single compressor is designed to perform multiple functions by serving different temperature zones with different cooling demands. Through variable speed operation and controlled refrigerant distribution, one compressor universally serves the entire multi-zone system, replacing what would traditionally require multiple zone-specific compressors.
4Use of energy by moving object
If compressor speed is continuously variable, then energy efficiency across load ranges is improved, but control system complexity increases
Solution Approach 1:
The control system uses feedback from temperature sensors and aggregate cooling demand calculations to automatically adjust compressor speed. This closed-loop control maintains energy efficiency by continuously optimizing compressor operation based on actual system requirements, with the complexity justified by the energy savings achieved across varying load conditions.
Solution Approach 2:
The control system automatically determines the aggregate cooling demand from multiple zones and self-adjusts the compressor speed without requiring manual intervention. The system serves itself by using its own temperature sensing and control capabilities to optimize its operation, making the added control complexity pay for itself through improved energy 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
This solution enables efficient operation across a wide range of temperatures, optimizing energy use and maintaining product quality by precisely managing refrigerant flow and compressor speed, effectively addressing the challenges of varying cooling demands in multi-zone refrigeration systems.
Implementation Method 1
a refrigerant vapor compression system including a refrigerant circuit through which a refrigerant mass flow is circulated by a compression device
Implementation Method 2
Refrigerant vapor compression systems are well known in the art and are commonly used for conditioning air
Implementation Method 3
Refrigerant vapor compression systems are commonly used for conditioning air to be supplied to a climate controlled comfort zone
Data Source
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AI summary
A refrigerant vapor compression system and a method of controlling the system are adapted for controlling the distribution of cooling capacity between two or more temperature controlled zones.