Ionic liquid-based absorption cooling system with high coefficient of performance
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Solution Overview
Problem
Absorption refrigeration systems (ARS) face limitations in performance due to the energy required for desorbing refrigerant from working fluids, with traditional systems relying on phase change processes that have not significantly improved since their introduction, and there is a need for a sorbent-refrigerant pair that enables efficient liquid-liquid phase separation at moderate temperatures.
Innovation Solution
Employing an ionic liquid as the sorbent that phase separates from the refrigerant at a lower critical solution temperature (LCST) in a liquid-liquid separator, reducing energy input by avoiding vaporization and promoting phase separation upon heating, with specific molecular structures of ionic liquids and refrigerants allowing for efficient miscibility and separation within a desired temperature window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional phase change desorption is used to separate refrigerant from sorbent, then separation is achieved, but energy consumption is high due to vaporization requirements
Solution Approach 1:
The invention changes the fundamental parameter of separation mechanism from phase change (vaporization) to liquid-liquid phase separation. By selecting specific ionic liquid-sorbent and refrigerant pairs that exhibit LCST or UCST behavior, the system achieves separation through temperature-induced solubility changes rather than vaporization, dramatically reducing energy consumption while maintaining effective separation.
Solution Approach 2:
The invention utilizes liquid-liquid phase separation transitions instead of liquid-gas phase transitions. By exploiting the critical solution temperature behavior of ionic liquid-refrigerant pairs, the system transitions from a homogeneous liquid phase to separated liquid phases through moderate heating, avoiding the high energy costs of vaporization while achieving complete refrigerant separation.
2Stability of the object's composition
If ionic liquid is used as sorbent with traditional vaporization desorption, then crystallization suppression is achieved, but energy consumption remains high
Solution Approach 1:
The invention changes the desorption mechanism parameter from thermal vaporization to temperature-induced liquid-liquid phase separation. By operating at temperatures below the refrigerant's boiling point but above the LCST/UCST of the ionic liquid-refrigerant pair, the system achieves both crystallization suppression (maintaining ionic liquid stability) and low-energy separation through solubility-driven phase separation.
3Loss of energy
If moderate temperature separation is used, then energy input is reduced, but a specific sorbent-refrigerant pair with LCST/UCST behavior is required
Solution Approach 1:
The invention applies local quality by selecting ionic liquids with specific molecular structures (cation and anion combinations) that create localized interactions with particular refrigerants. This molecular-level tailoring enables precise control over LCST/UCST temperatures, allowing the system to be optimized for specific refrigerant pairs while maintaining moderate operating temperatures for energy efficiency.
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 drastically reduces energy consumption, achieving a coefficient of performance (COP) of up to 5.8, allowing for a significant reduction in primary energy consumption for air-conditioning and enabling high-efficiency compact ARS designs.
Implementation Method 1
a sorbent, or absorbent) is an ionic liquid (IL) that phase separates from a refrigerant, or absorbate, in a liquid-liquid separator at a lower critical solution temperature (LCST)
Implementation Method 2
the refrigerant, also referred to as the absorbate, is a compound or mixture of compounds that undergoes phase changes between a liquid and gaseous state upon heating and cooling. The sorbent, also referred to as the absorbent, is a non-volatile IL or a mixture of an IL with other non-volatile components that absorbs the absorbate in the absorber portion of an ARS
Data Source
AI summary
An absorption refrigeration system (ARS), includes a sorbent-refrigerant pair that has an ionic liquid (IL) sorbent and a refrigerant that displays a lower critical lower critical solution temperature (LCST) at a temperature of 50 to 100° C., wherein the separation of the sorbent from the refrigerant occurs upon heating the sorbent-refrigerant pair to a temperature above the LCST. This liquid-liquid phase separation requires significantly less energy to desorb the refrigerant from the sorbent than vapor-liquid phase separation in traditional ABSs.