Refrigeration system with separate feedstreams to multiple evaporator zones
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Solution Overview
Problem
Direct expansion refrigeration systems face inefficiencies due to superheat control issues, particularly in low-temperature systems, leading to excessive inlet flashing, pressure drops, and instability, necessitating larger evaporators and compromising efficiency and capacity.
Innovation Solution
A refrigeration system with a fluid-tight circulation loop and multiple evaporator zones, where refrigerant flow is controlled based on measured conditions using sensors, allowing for continuous circulation in liquefied, gaseous, and two-phase states, and utilizing separate feed streams to optimize refrigerant distribution across zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If superheat control is used in direct expansion systems, then the evaporator can operate with dry conditions, but the evaporator must be 20% to 30% larger to provide equivalent surface area
Solution Approach 1:
The evaporator is divided into multiple zones with separate feedstreams, allowing each zone to be optimized for its specific refrigerant quality conditions. This segmentation enables more efficient use of evaporator surface area by matching refrigerant distribution to zone-specific requirements, eliminating the need for excessive overall evaporator size.
2Reliability
If superheat control is used, then evaporator dry operation is achieved, but excessive inlet flashing occurs causing pressure drop and instability
Solution Approach 1:
Different zones of the evaporator receive refrigerant with different qualities tailored to their specific requirements. Upstream zones receive refrigerant suited for flash suppression, while downstream zones receive refrigerant optimized for heat transfer. This local quality differentiation eliminates excessive inlet flashing and associated pressure drops while maintaining stable operation.
3Temperature
If superheat control is used in low-temperature systems, then refrigerant vapor is heated, but large amounts of liquid refrigerant are expelled requiring large liquid traps
Solution Approach 1:
The system performs preliminary heating of refrigerant vapor in dedicated upstream zones before the refrigerant reaches downstream zones. This preliminary action ensures complete vaporization and prevents liquid refrigerant expulsion, eliminating the need for large liquid traps while maintaining effective low-temperature operation.
4Productivity
If separate feedstreams to multiple evaporator zones are implemented, then efficiency and capacity are improved, but device complexity increases
Solution Approach 1:
The refrigeration system is segmented into multiple evaporator zones with separate feedstreams, allowing independent optimization of each zone for maximum efficiency and capacity. This segmentation, while increasing structural complexity, enables superior thermal performance that outweighs the added complexity through improved heat transfer efficiency and refrigerant utilization.
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 enhances efficiency and reduces refrigerant usage, minimizing the need for large liquid traps and improving system stability, achieving greater refrigeration system performance compared to traditional methods.
Implementation Method 1
compress refrigerant in a gaseous state within the compressor
Implementation Method 2
cool the refrigerant within the condenser to yield refrigerant in the liquefied state
Implementation Method 3
allowed to revaporize in the evaporator
Data Source
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AI summary
A refrigeration system 10 has: (a) a fluid tight circulation loop 11 including a compressor 12, a condenser 14 and an evaporator 18, the evaporator 18 having at least three evaporator zones, each evaporator zone having an inlet port 36, the circulation loop 11 being further configured to measure the condition of the refrigerant with a refrigerant condition sensor 44 disposed within the evaporator 18 upstream of the evaporator outlet port 34; and control the flow of refrigerant to the evaporator 18 based upon the measured condition of the refrigerant within the evaporator 18, and (b) a controller 40 for controlling the flow rate of refrigerant to the evaporator 18 based upon the measured condition of the refrigerant within the evaporator 18upstream of the evaporator outlet port 34.