Vapor Compression Cold Plate Control for Pulsed High-Heat-Flux Loads
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Solution Overview
Problem
Existing vapor compression systems are inadequate in maintaining uniform cold plate surface temperatures during highly transient pulsed heat loads, as they lack stability in supply and return process streams, are unable to handle variable thermal loads from 0% to 100%, and rely on temperature feedback methods that are slow and prone to instability.
Innovation Solution
Implementing a control system for vapor compression systems that includes electronically-actuated valves, electronic pressure regulators, and a bypass mechanism to adjust refrigerant flow and pressure, allowing for precise control of cold plate temperature through the use of a compressor, expansion valves, and thermal energy storage devices to maintain uniformity across a wide range of thermal loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional vapor compression systems are used for pulsed heat load applications, then the system can provide cooling capacity, but the cold plate surface temperature becomes non-uniform and fluctuates widely during pulsing cycles
Solution Approach 1:
The system pre-charges the cold plate with refrigerant liquid before the heat pulse occurs and pre-cools the refrigerant in the liquid line using the evaporator return line. This preliminary action ensures that when the pulse occurs, cooling capacity is immediately available, preventing temperature excursions and maintaining uniformity across the cold plate surface.
Solution Approach 2:
The system dynamically adjusts refrigerant flow rates, compressor speed, and expansion valve positioning in real-time based on the pulsing cycle phase. During the pulse, refrigerant flow is increased and compressor speed is elevated to match the elevated cooling demand, while during off-periods, the system reduces flow and pre-charges the cold plate, creating a dynamic response that maintains temperature uniformity throughout the cycle.
2Adaptability or versatility
If the vapor compression system responds to pulsed heat loads, then cooling capacity can be adjusted, but the supply and return process streams become unstable
Solution Approach 1:
The system employs multiple sensors to continuously monitor cold plate temperature, refrigerant pressures, and compressor operating conditions. This feedback is fed to the controller which adjusts expansion valve positioning, compressor speed, and refrigerant flow rates in real-time. The feedback mechanism allows the system to adapt to variable thermal loads while maintaining process stream stability through continuous correction of deviations from target operating parameters.
Solution Approach 2:
The system changes multiple operating parameters simultaneously including compressor speed, expansion valve positioning, refrigerant flow rates, and timing sequences to adapt to different pulse conditions. By coordinating changes in these parameters, the system achieves adaptability to variable thermal loads while maintaining stability of the refrigeration cycle through balanced adjustment of all critical parameters.
3Extent of automation
If temperature feedback control is used, then the system can regulate cooling output, but the control response is slow and prone to instability during rapid transients
Solution Approach 1:
Instead of waiting for temperature deviations to occur before responding, the system uses the controller to anticipate pulse events and pre-position the expansion valve, pre-charge the cold plate with refrigerant, and pre-adjust compressor speed before the heat load pulse occurs. This preliminary automated action eliminates the lag inherent in traditional temperature feedback control and provides immediate cooling response when the pulse begins.
Solution Approach 2:
The system replaces traditional mechanical temperature-based feedback control with an electronically-controlled system that uses the controller to directly actuate electronic expansion valves and variable speed compressors. This substitution of electronic control for mechanical feedback enables much faster response times and more precise regulation during rapid thermal transients, as electronic actuators respond instantaneously compared to mechanical thermal expansion mechanisms.
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
The system achieves stable and uniform cold plate surface temperatures during transient conditions, including no-load idle states and high-frequency pulsed thermal loads, without prior knowledge of heat load occurrence or pattern, by dynamically adjusting refrigerant supply and suction conditions.
Implementation Method 1
Subcooled liquid, saturated liquid, or nearly saturated two-phase refrigerant enters the cold plate assembly, accepts heat from the cold plate by removing heat from the heat generating components, and this heat evaporates the refrigerant
Implementation Method 2
a refrigerant-cooled cold plate assembly serves as the evaporator... a compressor to compress the refrigerant
Implementation Method 3
a condenser to condense the refrigerant coming from the compressor discharge outlet
Data Source
AI summary
A vapor compression system control implementations that maintain surface temperature uniformity of at least one cold plate throughout pulsed thermal loads from a minimal or zero load state suddenly to a high or 100% of design capacity state where the heat pulse occurrence, frequency, and durations are not known a priori. Vapor compression system control implementations that maintain surface temperature uniformity of at least one cold plate throughout pulsed thermal loads from a minimal or zero load state suddenly to a high or 100% of design capacity state where the heat pulse occurrence, frequency, and durations are not known a priori. Rapid thermal pulse applications require a robust control strategy of the cold plate assembly to maintain cold plate surface temperature uniformity. In one implementation, a control system for the cold plate assembly that maintains a uniform cold plate temperature given controlled supply and suction conditions is contemplated.