Open-Circuit Refrigeration With Refrigerant Recirculation for Mobile Cooling
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Solution Overview
Problem
Conventional closed-circuit refrigeration systems are heavy, power-intensive, and unsuitable for mobile platforms due to size and weight constraints, and struggle with maintaining precise temperature control for high heat flux, temperature-sensitive loads.
Innovation Solution
The implementation of open circuit refrigeration systems (OCRSs) with a pump that recirculates non-evaporated refrigerant, overfeeds the evaporator, and uses a heat exchanger to reduce pump cavitation, allowing for efficient heat transfer and reduced system size and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional closed-circuit refrigeration systems are used, then reliable cooling function is achieved, but system weight and power consumption increase significantly
Solution Approach 1:
The patent extracts and removes the compressor and condenser components from the refrigeration system, transitioning from a closed-circuit to an open-circuit configuration. This extraction eliminates the heavy mechanical compression equipment while maintaining cooling functionality through direct liquid refrigerant application to the evaporator, thereby significantly reducing system weight.
Solution Approach 2:
The patent replaces the mechanical compression system with a thermodynamic approach using liquid refrigerant direct expansion. Instead of using a mechanical compressor to circulate and compress refrigerant, the system uses direct liquid expansion at the evaporator inlet, substituting mechanical energy with a phase-change-based thermal management approach.
2Productivity
If conventional closed-circuit refrigeration systems are used, then cooling capacity is achieved, but power consumption increases
Solution Approach 1:
The patent removes the power-intensive compressor and condenser components from the system. By extracting these high-power mechanical elements and replacing them with a direct-expansion open-circuit configuration, the system achieves comparable cooling capacity with dramatically reduced power consumption.
Solution Approach 2:
The patent utilizes the phase transition of refrigerant from liquid to vapor directly at the evaporator inlet. This phase change process absorbs heat efficiently without requiring mechanical compression, leveraging thermodynamic principles to achieve cooling capacity with minimal energy input.
3Duration of action of moving object
If receiver size is increased to extend operation period, then operational duration is improved, but system volume and weight increase
Solution Approach 1:
The patent implements continuous recirculation of non-evaporated liquid refrigerant from the evaporator outlet back to the inlet through a pump. This continuous action ensures that unevaporated refrigerant is repeatedly utilized for heat absorption, extending the effective operation period without requiring a larger receiver storage volume.
Solution Approach 2:
The patent recovers and recirculates non-evaporated liquid refrigerant that would otherwise be wasted or require additional storage. By capturing the liquid refrigerant at the evaporator outlet and returning it to the inlet, the system maximizes the utilization of each unit of refrigerant, extending operational duration without increasing receiver size.
4Volume of moving object
If evaporator surface area is reduced, then system size is decreased, but heat transfer efficiency deteriorates
Solution Approach 1:
The patent changes the physical state and flow parameters of the refrigerant by recirculating non-evaporated liquid back to the evaporator inlet. This parameter change ensures that the refrigerant enters the evaporator in a consistent liquid state with optimized temperature and pressure, enhancing heat transfer efficiency per unit surface area and allowing for smaller evaporator dimensions.
Solution Approach 2:
The continuous recirculation of liquid refrigerant ensures that the evaporator surface is continuously supplied with cold liquid refrigerant at optimal conditions. This continuous action maintains high heat transfer coefficients throughout operation, enabling efficient heat transfer even with reduced evaporator surface area.
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 results in a more compact, lightweight, and energy-efficient thermal management system capable of maintaining precise temperature control for high heat flux loads, suitable for mobile platforms and applications where size and power constraints are significant.
Implementation Method 1
an evaporator configured to extract heat from a heat load that contacts the evaporator
Implementation Method 2
a heat exchanger having first and second inlets and first and second outlets, the first inlet coupled to the liquid side outlet of the liquid separator and the first outlet coupled to the inlet of the pump
Data Source
AI summary
A thermal management system includes an open circuit refrigeration circuit that has a refrigerant fluid flow path, with the refrigerant fluid flow path including a receiver configured to store a refrigerant fluid, a first control device configured to receive refrigerant from the receiver, a liquid separator, and an evaporator configured to extract heat from a heat load that contacts the evaporator, with the evaporator coupled to the first control device and the liquid separator. The system includes a pump having an inlet and an outlet, with the outlet of the pump coupled to the liquid side outlet of the liquid separator and a second control device that is coupled to an exhaust line, that is coupled to the vapor side outlet of the liquid separator through the second control device. In operation, the evaporator in the open circuit refrigeration circuit would be coupled to a heat load.