Refrigeration system with separate feedstreams to multiple evaporator zones
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Solution Overview
Problem
Direct expansion refrigeration systems face inefficiencies due to poor superheat control, especially in low-temperature systems, leading to excessive inlet flashing, pressure drops, and instability, requiring larger evaporators and liquid traps, 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 a refrigerant condition sensor, allowing for continuous circulation in liquefied, gaseous, and two-phase states, and dividing refrigerant into separate feed streams for each zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If superheat control is used in direct expansion systems, then the evaporator can operate with 20% to 30% dry condition, but this results in excessive inlet flashing, pressure drop, and instability
Solution Approach 1:
The evaporator is divided into multiple zones with separate feedstreams, allowing independent control of refrigerant flow to each zone. This segmentation enables precise control of evaporation processes in different regions, preventing excessive inlet flashing and pressure drop while maintaining stable operation.
Solution Approach 2:
Different zones of the evaporator are provided with tailored refrigerant flow rates based on local conditions. The refrigerant flow to each zone is controlled independently according to the measured condition of refrigerant within that zone, optimizing performance and preventing harmful effects in specific areas.
2Reliability
If superheat control is used, then the evaporator can maintain dry condition, but the evaporator must be 20% to 30% larger for equivalent surface area
Solution Approach 1:
By segmenting the evaporator into multiple zones with separate feedstreams, the system achieves effective superheat control without requiring excessive evaporator size. Each zone can be optimized independently, improving overall efficiency and reducing the total volume needed compared to a single-zone superheat control system.
3Ease of operation
If superheat control is used in low-temperature systems, then the system can operate, but liquid refrigerant is expelled from the evaporator requiring large liquid traps
Solution Approach 1:
In low-temperature systems, each evaporator zone receives refrigerant flow controlled according to its local conditions. This prevents excessive refrigerant expansion and liquid refrigerant expulsion from any zone, reducing the quantity of liquid refrigerant that would otherwise accumulate and require large liquid traps.
4Productivity
If separate feedstreams to multiple evaporator zones are implemented, then efficiency and capacity are improved, but device complexity increases
Solution Approach 1:
The evaporator is segmented into multiple zones with separate feedstreams, each controlled independently based on local refrigerant conditions. This segmentation improves system capacity and efficiency by optimizing refrigerant distribution, while the control system manages the complexity through automated feedback from refrigerant condition sensors.
Solution Approach 2:
Refrigerant condition sensors disposed within each evaporator zone provide feedback on the local refrigerant state. The controller uses this feedback to automatically adjust refrigerant flow to each zone, managing the complexity of multiple feedstreams through intelligent control algorithms that optimize performance without requiring manual intervention.
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 capacity with reduced refrigerant residence time and improved superheat control across all evaporator zones.
Implementation Method 1
a refrigerant which is capable of existing in a liquefied state, a gaseous state and a two-phase state comprising both refrigerant in the liquefied state and refrigerant in the gaseous state
Implementation Method 2
cool the refrigerant within the condenser to yield refrigerant in the liquefied state
Implementation Method 3
revaporize in the evaporator
Data Source
AI summary
A refrigeration system has: (a) a fluid tight circulation loop including a compressor, a condenser and an evaporator, the evaporator having at least three evaporator zones, each evaporator zone having an inlet port, the circulation loop being further configured to measure the condition of the refrigerant with a refrigerant condition sensor disposed within the evaporator upstream of the evaporator outlet port; and control the flow of refrigerant to the evaporator based upon the measured condition of the refrigerant within the evaporator, and (b) a controller for controlling the flow rate of refrigerant to the evaporator based upon the measured condition of the refrigerant within the evaporator upstream of the evaporator outlet port.