Two-Phase Refrigerant Flow Control for Stable Temperature Shifts
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Solution Overview
Problem
Existing thermal control systems using the Transfer Direct of Saturated Fluid (TDSF) technology face instability and overshoot when rapidly shifting between temperature levels due to delays in flow rate variations and system demands, necessitating improved control mechanisms to ensure precise and stable temperature changes.
Innovation Solution
The implementation of a TDSF system with separate flow paths for high-temperature two-phase refrigerant and condensed refrigerant, where the rate of change and final setting of the hot gas flow are selectively varied using stored control algorithms, and the introduction of a fast-acting control valve for rapid cooling, allowing for precise control through a stepper motor or analog signal control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the proportional valve setting is changed rapidly to shift between temperature levels, then the response time is improved, but instability and overshoot occur due to delays in flow rate variations
Solution Approach 1:
The control algorithm predicts the required valve positioning in advance and implements it before the temperature deviation occurs. By anticipating the needed adjustment based on the temperature control objective and system dynamics, the algorithm positions the proportional valve optimally ahead of time, enabling rapid response without overshoot or instability.
Solution Approach 2:
The control algorithm dynamically adjusts the proportional valve positioning based on real-time system conditions, including current temperature, rate of change, and predicted future states. This dynamic adaptation allows the system to optimize response speed while maintaining stability across varying operating conditions, rather than using fixed control parameters.
2Productivity
If the flow rate is increased to achieve faster temperature changes, then the productivity is improved, but the control precision deteriorates due to system delays
Solution Approach 1:
The control algorithm calculates and implements the optimal valve position in advance, before the temperature change is initiated. This preliminary positioning accounts for system delays and ensures that the flow rate increases smoothly and precisely, achieving fast temperature changes without sacrificing control precision.
Solution Approach 2:
The control algorithm continuously monitors actual temperature measurements and compares them with predicted values, using this feedback to adjust subsequent valve positioning decisions. This closed-loop control ensures that even at high productivity rates, the temperature control precision is maintained by correcting any deviations caused by system delays.
3Speed
If a fast-acting control valve is introduced for rapid cooling, then the response speed is improved, but the device complexity increases
Solution Approach 1:
The control algorithm acts as an intelligent intermediary between the temperature control objective and the fast-acting valve, coordinating their interaction to achieve rapid cooling without requiring complex hardware modifications. The algorithm manages the timing and magnitude of valve actions, simplifying the overall control architecture while leveraging the speed advantage of the fast-acting valve.
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 enables stable and precise control of temperature changes, reducing overshoot and instability, and allowing for rapid transitions to desired temperature levels, enhancing the responsiveness and efficiency of thermal control systems.
Implementation Method 1
a proportioning valve (42) having a setting controlled by a stepper control circuit (44) to provide a variable flow of pressurized hot gas to the mixing circuits (22)
Implementation Method 2
the flow remainder in the high temperature path is controlled with a proportional valve and the temperature of the flow in the second path is controlled with a thermal expansion valve
Implementation Method 3
a compressor (12) discharging pressurized two-phase refrigerant
Implementation Method 4
a condenser (14) receiving a flow of the refrigerant from the compressor and condensing the refrigerant to a liquid flow
Implementation Method 5
The mixed flows are applied to a thermal load (54) for direct thermal exchange
Implementation Method 6
the proportioning valve is driven at a selectively variable frequency by a stepper motor that is responsive to the control algorithms
Implementation Method 7
a bypass line (60) starting at between the hot gas flow path after the proportioning valve (42) and extending to the return line (57) (the input to the compressor (12)), the junction being made at a point prior to the input to the COR regulator valve (70). This bypass line (60) includes a solenoid expansion valve (62)
Data Source
AI summary
In a thermal control system of the type employing a two phase refrigerant that is first compressed and then is divided into a variable mass flow of refrigerant into a hot pressurized gas form and a differential remainder flow of cooled vapor derived from condensation and then thermal expansion, transitions between different temperature levels are enhanced by incremental variations of the mass flow at different control rates.