Falling Film Evaporator Level Control With Sensor-Guided Feed
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Solution Overview
Problem
Falling film evaporators in HVAC systems face challenges in maintaining an adequate refrigerant level while minimizing refrigerant usage, as they require precise control to optimize thermal energy exchange.
Innovation Solution
A system with a primary and secondary feed conduit for refrigerant flow, regulated by an auxiliary valve controlled by a sensor monitoring the refrigerant pool level, ensures optimal refrigerant distribution and level maintenance in the evaporator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a falling film evaporator is used to reduce refrigerant charge, then refrigerant consumption is reduced, but maintaining adequate refrigerant level becomes difficult
Solution Approach 1:
A level sensor detects the refrigerant pool level in the evaporator and provides feedback to an auxiliary valve. When the level drops below a threshold, the sensor signals the auxiliary valve to open, allowing additional refrigerant to flow through the secondary feed conduit to restore the level. This closed-loop feedback control maintains reliable refrigerant level while using less refrigerant overall compared to flooded evaporators.
Solution Approach 2:
The refrigerant supply system is segmented into a primary feed conduit and a secondary feed conduit with an auxiliary valve. The primary conduit handles normal refrigerant flow, while the secondary conduit with the controlled auxiliary valve provides supplemental refrigerant when needed. This segmentation allows precise control over refrigerant distribution, maintaining adequate levels without requiring excessive refrigerant charge.
2Productivity
If compressor guide vanes and system metering tools are used to control refrigerant circulation, then total rate of refrigerant circulation is controlled, but precise refrigerant level control in the evaporator is not achieved
Solution Approach 1:
The system incorporates a level sensor that continuously monitors the refrigerant pool level in the evaporator and provides feedback to an auxiliary valve. This localized feedback loop enables precise control of refrigerant level at the evaporator, complementing the overall refrigerant circulation control provided by compressor guide vanes and system metering tools. The auxiliary valve adjusts refrigerant flow based on real-time level conditions, achieving precision that cannot be obtained with system-level control alone.
Solution Approach 2:
The invention introduces local control quality to the refrigerant distribution system by placing a level sensor and auxiliary valve directly at the evaporator. This localized control mechanism independently manages refrigerant level at the evaporator, while the rest of the system maintains overall circulation control through guide vanes and metering tools. The local quality enhancement enables precise level control without disrupting system-wide refrigerant management.
3Reliability
If a secondary feed conduit with auxiliary valve is added to regulate refrigerant flow, then refrigerant level control is improved, but device complexity increases
Solution Approach 1:
The secondary feed conduit with auxiliary valve forms a simple feedback control loop where a level sensor monitors refrigerant pool level and automatically actuates the auxiliary valve to maintain the desired level. This feedback mechanism provides reliable level control through automatic operation, eliminating the need for manual intervention or complex control systems. The simplicity of the feedback loop—sensing, comparing, and actuating—achieves reliable control without proportionally increasing 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 effectively regulates refrigerant flow to maintain the desired refrigerant level, enhancing the efficiency of thermal energy transfer and reducing refrigerant consumption in falling film evaporators.
Implementation Method 1
At least one sensor senses a level of a refrigerant pool in the evaporator
Implementation Method 2
At least one auxiliary valve is located at the secondary feed conduit to regulate flow into the evaporator from the primary feed conduit
Implementation Method 3
the evaporator tubes are positioned typically below a distribution manifold from which refrigerant is urged, forming a 'falling film' on the evaporator tubes
Implementation Method 4
HVAC systems, such as chillers, use an evaporator to facilitate a thermal energy exchange between a refrigerant in the evaporator and a medium flowing in a number of evaporator tubes
Data Source
AI summary
A heating, ventilation and air-conditioning (HVAC) a falling film evaporator in flow communication with a condenser. The falling film evaporator includes a separator to separate vapor from liquid refrigerant and a plurality of evaporator tubes through which a volume of thermal energy transfer medium is flowed. A distribution system is operably connected to the separator to distribute a flow of liquid refrigerant over the plurality of evaporator tubes. A primary feed conduit delivers a flow of refrigerant to the separator, and at least one secondary feed conduit is in flow communication with the primary feed conduit. At least one auxiliary valve is located at the secondary feed conduit to regulate flow into the separator from the primary feed conduit. At least one sensor senses a level of a refrigerant pool in the evaporator. The sensor is operably connected to the at least one auxiliary valve to control operation thereof.