Method and apparatus for isothermal cooling
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Solution Overview
Problem
Existing cooling systems face challenges in achieving isothermal heat rejection at specified temperatures, particularly due to poor liquid distribution in evaporator channels, leading to sub-optimal performance and non-ideal isothermality.
Innovation Solution
A cooling apparatus that includes a subcooler, flow control valve, primary evaporator assembly, and pressure regulator, which controls saturation pressure to maintain isothermal evaporation conditions, ensuring optimal liquid distribution and isothermality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If two-phase distributors are used to distribute liquid-vapor mixtures amongst parallel channels, then cooling capacity is increased, but liquid distribution becomes unbalanced causing channels with excess liquid and channels with too little liquid
Solution Approach 1:
The invention extracts and removes the vapor phase from the liquid-vapor mixture before distribution to evaporator channels. By separating the vapor (flash gas) from the liquid refrigerant and routing it directly to the compressor inlet, only saturated liquid is distributed to the evaporators, eliminating the maldistribution problem caused by two-phase flow
Solution Approach 2:
The system segments the refrigerant flow path into separate liquid and vapor routes after expansion. The liquid phase is directed to evaporators through dedicated liquid lines with flow distributors, while the vapor phase is routed separately to the compressor, allowing independent optimization of each flow path
2Productivity
If microchannel evaporators with excessive numbers of channels are used, then heat transfer efficiency is improved, but liquid distribution becomes unwieldy and difficult to control
Solution Approach 1:
The invention introduces an intermediary device (flash gas tank and liquid flow distributor) between the expansion device and the microchannel evaporators. This intermediary system provides a controlled liquid-only supply to each channel inlet, acting as a mediator that simplifies the distribution task despite the large number of channels
3Manufacturing precision
If flash gas bypass systems are used to distribute nearly pure saturated liquid, then liquid distribution is improved, but any pressure drop causes vapor formation and increases maldistribution
Solution Approach 1:
The system performs preliminary separation of vapor and liquid phases immediately after expansion, before the refrigerant enters the distribution network. By removing flash gas upfront and maintaining positive pressure in the liquid lines, the system prevents vapor formation during distribution, ensuring reliable liquid-only flow to all channels
4Temperature
If two-phase pumped loops are used to circulate liquid to evaporators, then isothermal conditions are maintained, but substantial liquid head is required at pump inlet to avoid cavitation
Solution Approach 1:
The invention replaces the mechanical two-phase pump system with a passive thermodynamic system using flash gas bypass. Instead of mechanically circulating two-phase mixture requiring high inlet head, the system uses pressure differential and phase separation to achieve circulation, eliminating cavitation risks while maintaining isothermal evaporation
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 apparatus effectively maintains isothermal evaporation conditions, optimizing liquid distribution and enhancing the performance of evaporators, thereby achieving efficient isothermal cooling.
Implementation Method 1
a subcooler having a first side in fluid communication with the first fluid flowpath and a second side configured to be disposed in thermal communication with a source of cooling fluid
Implementation Method 2
passing the first stream of the refrigerant through a flow control valve to expand it to a lower pressure as a liquid
Implementation Method 3
passing the first stream of the refrigerant through a primary evaporator assembly, and absorbing heat from a primary heat load at a predetermined temperature
Implementation Method 4
absorbing heat from a primary heat load at a predetermined temperature
Implementation Method 5
a pressure regulator operable to maintain a refrigerant saturation pressure within the primary evaporator at a predetermined set point
Data Source
AI summary
A cooling apparatus includes a first fluid flowpath and a second fluid flowpath. The first fluid flowpath includes a subcooler having a first side in fluid communication with the first fluid flowpath; a flow control valve; a primary evaporator assembly including at least one evaporator configured to be disposed in thermal communication with a heat load; and a pressure regulator operable to control a saturation pressure within the at least one evaporator. The second fluid flowpath is in fluid communication with a second side of the subcooler.