Multi-Zone Refrigerant Flow Control for Transport Cooling
Find Innovative SolutionsGenerate Solutions
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, often requiring a single set point control, which can lead to inefficient operation and inadequate temperature maintenance.
Innovation Solution
A method for controlling refrigerant vapor compression systems by circulating refrigerant mass flow through a variable speed compression device, selectively dividing the flow among multiple zones based on temperature differentials, using a PI controller with anti-windup and zone volume weighted averaging, and regulating refrigerant flow through liquid control valves to meet collective cooling demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single set point control is used for the refrigerant vapor compression system, then the system structure is simple, but the temperature control precision for multiple zones deteriorates
Solution Approach 1:
The cargo space is divided into multiple temperature-controlled zones, each with its own evaporator and temperature sensor. The refrigerant flow is segmented and directed to different zones based on their specific cooling demands, allowing independent temperature control for each zone while using a single compression system.
Solution Approach 2:
The system dynamically adjusts refrigerant flow distribution to multiple evaporators based on real-time temperature feedback from each zone. The electronic expansion valves or flow control mechanisms modify refrigerant allocation dynamically to meet varying temperature requirements of different zones, transforming a static single-setpoint system into a dynamic multi-zone control system.
2Reliability
If the refrigerant vapor compression system operates at high capacity, then the cooling demand is met, but energy efficiency deteriorates during low load conditions
Solution Approach 1:
The compression device operates at variable speeds according to the actual cooling demand of the cargo space. During low load conditions, the compressor reduces its speed to match the reduced cooling requirement, maintaining energy efficiency. During high demand periods, it increases capacity to meet the cooling load, thus dynamically optimizing the balance between reliability and energy efficiency.
Solution Approach 2:
The system changes operational parameters including compressor speed, refrigerant flow rate, and expansion valve opening to adapt to varying cooling demands. By continuously adjusting these parameters based on temperature feedback and load conditions, the system maintains high energy efficiency across different operating conditions while ensuring cooling demand is always met.
3Adaptability or versatility
If multiple evaporators are used for multiple zones, then temperature control versatility improves, but device complexity increases
Solution Approach 1:
The refrigeration system is segmented into multiple evaporator units, each serving a specific temperature zone. Each evaporator can be independently controlled with its own expansion device and refrigerant flow control, allowing the system to adapt to different temperature requirements simultaneously while maintaining manageable complexity through modular architecture.
Solution Approach 2:
A single compression system serves multiple functions by providing cooling to multiple zones with different temperature requirements. The shared compression unit, condenser, and refrigerant circuit perform multiple cooling tasks simultaneously, reducing overall system complexity compared to having separate compression systems for each zone while maintaining full temperature control versatility.
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 approach allows for efficient cooling capacity distribution across multiple zones, ensuring precise temperature control and optimizing energy use by varying the compressor speed and refrigerant flow according to sensed temperatures and set points, thereby maintaining product integrity during transport.
Implementation Method 1
refrigerant vapor compression system includes a refrigerant circuit through which a refrigerant mass flow is circulated by a compression device
Implementation Method 2
controlling the refrigerant mass flow through the refrigerant circuit to provide a cooling capacity
Implementation Method 3
a plurality of liquid flow control valves with one liquid flow control valve disposed in the refrigerant circuit in operative association with each of the plurality of evaporators for regulating the mass flow of refrigerant therethrough
Implementation Method 4
a plurality of evaporators with at least one evaporator associated with each one of the plurality of temperature controlled zones, a first evaporator through which a flow of air circulated from the associated one of the plurality of temperature controlled zones is passed in heat exchange relationship with a portion of the refrigerant mass flow
Data Source
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.