Liquid CO2 Passive Refrigeration for Controlled Snow-Based Cooling
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Solution Overview
Problem
Existing passive refrigeration systems using dry ice struggle with temperature control accuracy and waste due to uncontrollable sublimation rates, leading to high CO2 concentrations that can damage products and inefficiencies.
Innovation Solution
A passive refrigeration system using liquid CO2 (LCO2) that converts to carbon dioxide snow and gas within an expansion chamber, controlled by a valve and sensor, to maintain uniform temperature without flooding the cargo space, utilizing turbulence and accumulation features for efficient heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If dry ice is used in passive refrigeration systems, then cooling effect is achieved, but temperature control accuracy deteriorates due to uncontrollable sublimation rates
Solution Approach 1:
The system changes the physical state parameter of CO2 from solid (dry ice) to liquid, enabling controlled phase transition. Liquid CO2 is injected into the cargo space where it undergoes controlled evaporation, allowing precise temperature regulation through controllable vaporization rates rather than uncontrollable sublimation.
Solution Approach 2:
Liquid CO2 serves as an intermediary substance between the cooling system and the cargo. It is injected in liquid form and then evaporates to provide cooling, acting as a controllable medium that can be precisely dosed and regulated, unlike direct dry ice placement which cannot be easily controlled.
2Loss of energy
If dry ice is used for refrigeration, then cooling is provided, but CO2 waste increases due to uncontrollable sublimation
Solution Approach 1:
The system incorporates temperature sensors and control mechanisms that monitor the cargo space temperature and regulate liquid CO2 injection accordingly. This feedback control ensures CO2 is only introduced when needed and at precise amounts, preventing waste from uncontrollable sublimation while maintaining effective cooling.
Solution Approach 2:
Instead of continuous or predetermined dry ice placement, the system uses periodic liquid CO2 injection based on temperature monitoring. The injection occurs in controlled cycles only when temperature thresholds are exceeded, reducing overall CO2 consumption while maintaining cooling effectiveness.
3Power
If high concentrations of CO2 are introduced into cargo space, then cooling capacity is enhanced, but product damage occurs due to CO2 exposure
Solution Approach 1:
The system creates localized cooling zones through targeted liquid CO2 injection rather than uniformly flooding the entire cargo space with high CO2 concentrations. The liquid CO2 evaporates in specific areas near the cargo, providing intense local cooling while the overall CO2 concentration in the cargo space remains lower and less harmful to products.
4Productivity
If liquid CO2 is injected directly into cargo space, then cooling efficiency is improved, but system complexity increases due to control requirements
Solution Approach 1:
The system uses the natural evaporation properties of liquid CO2 to provide self-regulating cooling. When liquid CO2 is injected, it automatically evaporates and absorbs heat without requiring active control mechanisms during the evaporation process itself, simplifying the system while maintaining high cooling 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
Achieves precise temperature control, reduces CO2 waste, and protects products by maintaining uniform cooling without direct CO2 exposure, optimizing load capacity and system size.
Implementation Method 1
The expansion section is adapted to allow the vaporization of the liquid CO2 into the expansion chamber to create a mixture of carbon dioxide snow and CO2 gas within the expansion chamber, thereby cooling the cargo space via the heat transfer surface
Implementation Method 2
cooling the cargo space via the heat transfer surface
Implementation Method 3
the at least one bluff body facilitates generation of turbulence within the expansion chamber, in order to facilitate creation and accumulation of carbon dioxide snow
Data Source
AI summary
A passive refrigeration apparatus comprising: (i) a container defining a cargo space; (ii) a liquid carbon dioxide cylinder; (iii) a control valve, in fluid communication with the cylinder; (iv) a controller for activating the control valve to control the flow of liquid CO2; and (v) a heat transfer assembly within the container, in fluid communication with the control valve; wherein the heat transfer assembly has (a) an expansion section for receiving the flow of liquid CO2; and (b) an expansion chamber bounded by a heat transfer surface in thermal contact with the cargo space; wherein the expansion section allows the vaporization of the liquid CO2 into the expansion chamber to create a mixture of carbon dioxide snow and CO2, thereby cooling the cargo space via the heat transfer surface.