Mechanically pumped system for direct control of two-phase isothermal evaporation
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Solution Overview
Problem
Current methods for maintaining isothermal heat rejection in systems with large heat loads face challenges such as poor isothermality, low evaporator performance, and excessive equipment requirements, particularly due to issues with fluid distribution and cavitation in multi-channel evaporators.
Innovation Solution
A thermal system comprising a reservoir, a cooling loop, and a heat rejection loop with specific components like sub-coolers, pre-heaters, evaporators, pressure regulators, and vapor compressors, which manage fluid flow and pressure to achieve consistent temperature and efficient heat transfer by sub-cooling, pre-heating, and regulating pressure to maintain saturation conditions within the evaporator channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If standard heat rejection methods are used, then heat transfer occurs, but isothermal temperature control deteriorates
Solution Approach 1:
The system changes the pressure parameter of the working fluid using a pressure regulator to maintain constant saturation temperature during evaporation, achieving isothermal heat rejection. By controlling pressure to correspond to a specific saturation temperature, the system ensures consistent temperature control throughout the evaporator channels.
Solution Approach 2:
The system performs preliminary sub-cooling of the working fluid before it enters the evaporator channels. This pre-cooling action ensures the fluid enters the evaporator at a controlled temperature and pressure state, enabling subsequent isothermal evaporation and improving temperature consistency during heat rejection.
2Area of stationary object
If multi-channel evaporators are used, then heat transfer area increases, but fluid distribution uniformity deteriorates
Solution Approach 1:
The system applies local quality by providing sub-cooling specifically at the inlet regions of the evaporator channels before fluid distribution. This localized pre-cooling ensures uniform fluid properties across all channels at the point of distribution, improving flow uniformity while maintaining large heat transfer area through multi-channel configuration.
3Productivity
If evaporation rate increases, then heat rejection efficiency improves, but cavitation risk increases
Solution Approach 1:
The system performs preliminary sub-cooling of the working fluid before it reaches the evaporator and pump inlet. This pre-cooling action increases the margin between the fluid temperature and its saturation temperature, preventing cavitation during high-rate evaporation by ensuring liquid remains in a stable state throughout the system.
Solution Approach 2:
The sub-cooling process creates a temperature buffer or cushion before the fluid enters the evaporator channels. This buffer protects against cavitation by maintaining a larger temperature difference between the actual fluid temperature and saturation temperature, even during high evaporation rates, thereby preventing vapor bubble formation that would cause cavitation.
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 ensures stable, consistent temperature maintenance for heat loads while optimizing evaporator performance and reducing the need for excessive space and equipment, thereby enhancing isothermal heat rejection and system efficiency.
Implementation Method 1
a liquid pump, a first side of a pre-heater
Implementation Method 2
sub-cooling the fluid drawn from the reservoir
Implementation Method 3
pre-heating the pumped fluid prior to the inlet of the evaporator
Implementation Method 4
evaporating a portion of the fluid in the evaporator
Implementation Method 5
Two-Phase Isothermal Evaporation
Implementation Method 6
regulating the pressure of the fluid at the outlet of the evaporator to thereby maintain a substantially constant fluid temperature
Implementation Method 7
compressing the fluid drawn from the reservoir
Implementation Method 8
condensing the compressed fluid
Implementation Method 9
expanding the condensed fluid
Data Source
AI summary
A thermal system may comprise a reservoir, a first fluid flowpath, and a second fluid flowpath. The first fluid flowpath may start at the reservoir and return to the reservoir. The first fluid flowpath may comprise, in a direction of the fluid flow, a first side of a sub-cooler, a liquid pump, a first side of a pre-heater, and a first side of an evaporator. The second fluid flowpath may start at the reservoir and return to the reservoir. The second fluid flowpath may comprise, in a direction of a fluid flow, a pressure regulator, a vapor compressor, a first side of a condenser, and an expansion value.