Cryogenic Dispensing System Raised Basin Liquid Head
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Solution Overview
Problem
Cryogenic liquid dispensing systems face inefficiencies due to insufficient liquid head, leading to underutilization of cryogenic fluids in tanks, as the pump's Net Positive Suction Head (NPSH) requirements are not met, especially when the liquid level drops, resulting in the inability to dispense all the liquid stored.
Innovation Solution
A cryogenic liquid dispensing system that includes a raised basin above the tank, allowing cryogenic liquid to be pumped to this basin when the tank's liquid head is insufficient, thereby increasing the liquid head available for pumping and enhancing utilization, with additional supply lines and valves managing the flow between the tank and the basin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the liquid level in the tank drops below the required height, then the pump cannot maintain adequate liquid head for reliable operation, but increasing the tank height to maintain liquid head increases the physical dimensions of the dispensing system
Solution Approach 1:
The system divides the liquid storage into two separate vessels: a primary tank and a secondary tank. The pump can draw liquid from either tank independently, allowing the primary tank to be shorter while maintaining adequate liquid head through the secondary tank when needed. This segmentation resolves the contradiction by separating the storage function from the liquid head provision function.
Solution Approach 2:
The secondary tank acts as an intermediary vessel that provides additional liquid head when the primary tank level drops. It mediates between the pump's NPSH requirements and the primary tank's reduced height, allowing the pump to maintain reliable operation without increasing the primary tank's dimensions.
2Productivity
If the liquid level in the tank is insufficient to provide required liquid head, then the pump cannot dispense liquid, but adding a raised basin or secondary tank increases device complexity
Solution Approach 1:
The second vessel serves multiple functions: it provides additional liquid head when the first vessel level drops, acts as a backup storage reservoir, and can be integrated with the existing tank structure. This multi-functionality justifies the added complexity by delivering significant productivity benefits in liquid dispensing capability.
3Temperature
If the pump is submerged in cryogenic liquid to ensure adequate cooling, then the pump requires sufficient liquid head to prime and operate, but flow obstructions in the supply line increase pressure loss and reduce available liquid head
Solution Approach 1:
The system pre-cools the pump by maintaining it submerged in cryogenic liquid during idle periods and uses recirculation lines to ensure continuous cooling. This preliminary cooling action ensures the pump is already at operating temperature before dispensing begins, reducing the immediate demand for high liquid head and pressure during startup.
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 configuration allows for greater utilization of cryogenic liquids by maintaining adequate liquid head for pump operation, even when the tank's liquid level is low, without increasing the physical dimensions of the dispensing system, thereby optimizing the use of stored cryogenic fluids.
Implementation Method 1
A pump in the dispensing system may pump cryogenic liquid from the tank to the raised basin when the liquid head provided by the level of cryogenic liquid in the tank is insufficient for reliable operation of the pump
Implementation Method 2
The liquids are often stored in double-walled bulk tanks or containers with a vacuum between the walls of inner and outer vessels as insulation to reduce heat transfer from the ambient environment into the cryogenic liquid
Implementation Method 3
The liquid head is dependent upon the relative height X of the cryogenic liquid in the tank above the pump
Data Source
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AI summary
A cryogenic liquid dispensing system having a tank that holds cryogenic liquid and a basin configured to hold cryogenic liquid at a height above a bottom portion of the tank. The system is configured to pump cryogenic liquid for dispensing from the bottom portion of the tank when the cryogenic liquid in the tank is of a sufficient level to provide an adequate liquid head to permit pump operation, and is configured to pump cryogenic liquid for dispensing from the basin when the liquid in the tank is of an insufficient level to provide an adequate liquid head to permit pump operation to dispense cryogenic liquid.