Open-Cycle Cooling System Using Water Refrigerant and Membrane Exhaust
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Solution Overview
Problem
The HVAC/R industry faces challenges in using natural refrigerants that do not increase carbon emissions and eliminating per- and poly-fluoroalkyl substances (PFAS), requiring a system that effectively moves heat from a low temperature source to a high temperature sink while rejecting heat at a lower effective temperature to reduce compressor power and environmental impact.
Innovation Solution
An open cycle cooling system utilizing water as a natural refrigerant, featuring a heat exchanger, compressor, and exhaust device with a membrane that permits gaseous refrigerant to exit while preventing ambient air entry, using a multi-stage radial, mixed-flow, or axial centrifugal compressor and a polymeric membrane with pores smaller than nitrogen gas molecular size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional closed-cycle systems with synthetic refrigerants are used, then cooling performance is maintained, but carbon emissions increase and environmental harm occurs
Solution Approach 1:
The system changes the fundamental parameter of refrigerant type from synthetic refrigerants (R-410A, R-32) to natural refrigerants (water, ammonia, hydrocarbons), thereby eliminating ozone depletion and reduced GWP while maintaining cooling performance through proper system design
Solution Approach 2:
The patent extracts the refrigerant from a closed cycle and allows it to be discharged to the atmosphere after use, using the atmosphere as the final heat sink. This open-cycle approach eliminates the need for refrigerant recovery and recycling infrastructure while using environmentally benign natural refrigerants
2Productivity
If heat is rejected at outdoor ambient dry bulb temperature, then cooling capacity is maximized, but compressor head and power increase
Solution Approach 1:
The system changes the heat rejection temperature parameter from outdoor ambient dry bulb temperature to dew point temperature by utilizing the moisture in ambient air as the heat sink, thereby reducing the temperature differential and compressor work requirements
Solution Approach 2:
The patent introduces moisture (water vapor) as an intermediary medium between the refrigerant and the outdoor air, using evaporative cooling and moisture transfer to reject heat at a lower effective temperature than the ambient dry bulb temperature
3Object-affected harmful factors
If open-cycle system with natural refrigerant is used, then environmental impact is reduced, but system complexity increases due to membrane and moisture management
Solution Approach 1:
The patent employs a semi-permeable membrane in the exhaust device that allows water vapor to pass through while blocking non-condensable gases, enabling simple separation without complex mechanical separators or multiple heat exchangers
Solution Approach 2:
The system uses the natural properties of water vapor condensation and the semi-permeable membrane's selective permeability to automatically separate and manage moisture, eliminating the need for complex active moisture management systems
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 system efficiently cools indoor spaces using water as a refrigerant, reducing compressor power and environmental impact by rejecting heat at a higher temperature than the dew point, thus lowering indoor temperatures while minimizing air contamination and carbon emissions.
Implementation Method 1
the membrane includes a plurality of pores that permit the gaseous natural refrigerant to exit the exhaust device while preventing or at least minimizing the air of the external ambient environment from entering the exhaust device. the pores are sized to be less than a molecular size of nitrogen gas.
Implementation Method 2
a heat exchanger in communication with the source of liquid natural refrigerant that is configured to convert the liquid natural refrigerant into a gaseous natural refrigerant
Implementation Method 3
a compressor in communication with the heat exchanger and configured to increase a temperature and pressure of the gaseous natural refrigerant received from the heat exchanger
Implementation Method 4
an exhaust device in communication with the compressor and configured to expel the gaseous natural refrigerant received from the compressor to air of an external ambient environment
Data Source
AI summary
A cooling system that may include a source of liquid natural refrigerant, a heat exchanger in communication with the source of liquid natural refrigerant that is configured to convert the liquid natural refrigerant into a gaseous natural refrigerant, a compressor in communication with the heat exchanger and configured to increase a temperature and pressure of the gaseous natural refrigerant received from the heat exchanger, and an exhaust device in communication with the compressor and configured to expel the gaseous natural refrigerant received from the compressor to air of an external ambient environment. The exhaust device includes a membrane that permits the gaseous natural refrigerant to exit the exhaust device while preventing or at least minimizing the air of the external ambient environment from entering the exhaust device.