Bulk Tank Baffle for Subcooled CO2 Dispensing
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Solution Overview
Problem
Existing systems for storing and dispensing cryogenic liquids like liquid CO2 are inefficient as they require 'off-hours' operation for refills and allow migration of chilled liquid, leading to increased CO2 usage and compressor size.
Innovation Solution
A vertically oriented bulk tank with a stainless steel inner tank and a baffle to create stratification, combined with a heat exchanger and pressure builder system, allows continuous operation and reduces liquid migration, maintaining subcooled CO2 at 300 psig for efficient dispensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If liquid CO2 is subcooled to increase snow yield and refrigeration efficiency, then the percentage of CO2 snow increases and vapor decreases, but the chilled liquid migrates from the bottom portion to the warmer liquid in the top portion of the tank
Solution Approach 1:
The tank is divided into two distinct zones using a baffle: a bottom portion for storing subcooled liquid CO2 and a top portion for warmer liquid CO2. This segmentation prevents mixing and migration between the two temperature zones, allowing the system to maintain subcooled liquid CO2 for efficient dispensing without loss to the warmer upper region.
Solution Approach 2:
A baffle acts as an intermediary physical barrier between the subcooled liquid CO2 in the bottom portion and the warmer liquid CO2 in the top portion. This intermediary structure prevents direct thermal contact and liquid migration, maintaining the temperature stratification necessary for high snow yield while preventing unnecessary CO2 consumption.
2Productivity
If the system operates continuously between refills, then productivity increases, but the existing system requires off hours operation and cannot maintain continuous subcooled liquid supply
Solution Approach 1:
The system preliminarily subcools liquid CO2 in the bottom portion of the tank before dispensing operations begin. By maintaining a reservoir of subcooled liquid CO2 in advance within the bottom portion, the system is prepared for continuous dispensing operations without requiring shutdowns for re-subcooling, enabling uninterrupted operation during refills and between refills.
Solution Approach 2:
The system maintains continuous subcooled liquid CO2 supply in the bottom portion through the baffle-separated stratification structure. This allows the dispensing operation to continue uninterrupted during refills of the top portion, as the bottom portion's subcooled liquid remains available. The useful action of providing cold CO2 for snow generation continues without interruption.
3Power
If a larger compressor is used to maintain subcooled liquid CO2, then refrigeration capacity increases, but system complexity and cost increase
Solution Approach 1:
By segmenting the tank into two temperature zones with a baffle, the system creates a larger effective volume for subcooled liquid CO2 storage in the bottom portion. This segmentation allows the existing compressor to maintain subcooled liquid more effectively, as the stratified structure prevents warm liquid from the top portion from mixing with and warming the subcooled liquid, thereby maintaining refrigeration capacity without requiring a larger compressor.
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
The system achieves higher snow yield and refrigeration capacity, reducing CO2 consumption and enabling smaller, more efficient compressors, while allowing uninterrupted operation during refills.
Implementation Method 1
Liquid CO2 is subcooled outside of the tank by a heat exchanger of an external refrigeration system
Implementation Method 2
a thermocline region is created within the bottom portion of the tank
Implementation Method 3
A pressure of approximately 300 psig is maintained in the head space of the tank via condensation of vapor therein
Implementation Method 4
expanded at atmospheric pressure where it transforms into solid phase CO2 'snow' or dry ice and CO2 vapor
Data Source
AI summary
A system and method for dispensing subcooled CO2 liquid includes a vacuum insulated bulk tank containing a supply of the liquid CO2. A pressure builder having an inlet in communication with a bottom portion of the bulk tank and an outlet in communication with a top portion of the bulk tank vaporizes liquid from the bulk tank and delivers the resulting gas to the top portion of the tank so as to pressurize it. A baffle is positioned within the bulk tank. Below the baffle, a refrigeration system is connected to the heat exchanger coil so that a refrigerant fluid is supplied to and received from the heat exchanger coil so that the liquid below the baffle is subcooled and the liquid above the baffle is stratified. A liquid fill line is in communication with the interior of the bulk tank via a fill line opening that is positioned above the baffle. A liquid feed line is in communication with a bottom portion of the interior of the bulk tank so that subcooled liquid may be dispensed.