Method and device for cooling products
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Solution Overview
Problem
The cooling efficiency of carbon dioxide snow is limited by its sublimation temperature of -78.9°C, leading to reduced effectiveness due to the Leidenfrost effect and inefficient heat transfer, and existing alternatives like liquid nitrogen suspensions are difficult to atomize and not suitable for all applications.
Innovation Solution
Mixing the carbon dioxide snow and gas stream with a cold gas stream at a temperature below -78.9°C after expansion, and recycling the cold gas to further cool and transport the carbon dioxide snow, enhancing cooling efficiency and reducing gas usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid carbon dioxide is expanded at the expansion nozzle to form carbon dioxide snow, then cooling effect is achieved, but the cooling efficiency is limited due to the sublimation temperature of -78.9°C and the Leidenfrost effect
Solution Approach 1:
The patent applies preliminary action by pre-cooling the liquid carbon dioxide to temperatures below -78.9°C before expansion. This preliminary cooling ensures that when the liquid expands and forms snow, the snow particles start at a lower temperature, delaying sublimation and improving cooling efficiency. The pre-cooling step prepares the cooling medium in advance to overcome the inherent temperature limitation of standard carbon dioxide expansion.
Solution Approach 2:
The patent changes the temperature parameter of the liquid carbon dioxide from ambient temperature to sub-zero temperatures (below -78.9°C) before expansion. This parameter change transforms the physical state and thermal properties of the carbon dioxide, enabling the formation of colder snow particles that resist immediate sublimation and provide more effective cooling.
2Productivity
If the proportion of carbon dioxide snow is increased by cooling the liquid carbon dioxide before expansion, then cooling efficiency improves, but the complexity of the system increases
Solution Approach 1:
The patent applies self-service by using the cold gas stream generated during the expansion process itself to pre-cool the incoming liquid carbon dioxide. The expansion nozzle produces a cold gas stream that is redirected to cool the liquid carbon dioxide in the supply line before it reaches the expansion nozzle. This self-cooling mechanism eliminates the need for external cooling systems, maintaining high cooling efficiency while avoiding increased system complexity.
Solution Approach 2:
The patent recovers the cold gas stream that would otherwise be wasted during the expansion process. Instead of discarding this cold gas, it is redirected to pre-cool the liquid carbon dioxide supply. This recovery approach transforms a byproduct into a useful resource, improving cooling efficiency without requiring additional cooling equipment or increasing system complexity.
3Temperature
If a suspension of liquid nitrogen and dry ice particles is used as cooling medium, then temperatures below -78.9°C can be achieved, but the suspension is difficult to atomize and not suitable for many cooling applications
Solution Approach 1:
The patent inverts the conventional approach by first expanding liquid carbon dioxide to form snow and gas, then using the resulting cold gas stream to cool the liquid carbon dioxide supply. Instead of mixing liquid nitrogen with dry ice particles and attempting to atomize the suspension, the patent works backwards: it creates the snow-gas mixture first, then uses that mixture to pre-cool the liquid supply, achieving below -78.9°C temperatures with easily atomizable liquid carbon dioxide.
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
Supercooling the carbon dioxide snow to temperatures below -100°C increases cooling efficiency by delaying the Leidenfrost effect and improving heat transfer, while recycling the cold gas reduces overall consumption and enhances the proportion of solid carbon dioxide, leading to more effective and efficient cooling processes.
Implementation Method 1
the liquid carbon dioxide under a pressure of 5.18 bar abs. and usually introduced at ambient temperature and relaxed at the relaxation nozzle. As the carbon dioxide expands to atmospheric pressure, it cools to a temperature of -78.9°C (194 K), forming a mixture of carbon dioxide snow and cold carbon dioxide gas.
Implementation Method 2
Since the carbon dioxide snow produced during the expansion of liquid carbon dioxide moves along the sublimation curve when heat is input, i.e. in the energy exchange with a warmer product, part of the solid carbon dioxide sublimates immediately after application to a product to be cooled.
Implementation Method 3
the stream of carbon dioxide snow and carbon dioxide gas emerging from the carbon dioxide expansion nozzle is mixed with a cold gas stream after it has been produced and is thereby cooled
Data Source
Figure 1~2
AI summary
The method involves mixing stream of carbon dioxide snow and carbon dioxide gas emerging from a carbon dioxide relief nozzle (5) after generation with a cold gas stream and cooling the mixed stream. The cold gas stream provided for cooling the stream of the carbon dioxide snow and the carbon dioxide gas is used for precooling liquid carbon dioxide before supply to the carbon dioxide relief nozzle. A partial stream of the cold gas stream is recirculated and used for cooling the stream of the carbon dioxide snow and the carbon dioxide gas from the nozzle. The cold gas stream is a cold cryogenic gas such as nitrogen, oxygen, argon and helium. An independent claim is also included for a device for cooling of products with dry ice particles.