Subcooled Cryogenic Liquid Supply via Submerged Heat Exchanger
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Solution Overview
Problem
Existing solutions for supplying subcooled cryogenic liquids to machining stations from high-pressure storage tanks face challenges such as pressure variations leading to flow rate disturbances, gas creation at the nozzle, and inefficiencies in heat exchange, as well as high costs and thermal bridging due to venting mechanisms, making it difficult to supply multiple stations simultaneously at different pressures.
Innovation Solution
A system featuring a heat exchanger immersed in a cryogenic liquid bath with controlled level and pressure regulation, combined with a purger to reduce gaseous volume and optimize pipe dimensions, allows for stable subcooled liquid supply to machining stations without the need for additional pumps or tanks, enabling simultaneous supply to multiple stations at varying pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If cryogenic liquid is supplied from high-pressure storage tank, then liquid can reach machining station without pump, but pressure varies with liquid level causing flow rate disturbances
Solution Approach 1:
An intermediary pressure regulation system is introduced between the storage tank and machining station. This system includes a pressure regulator and accumulator that decouple the variable tank pressure from the machining station, maintaining stable flow rate despite pressure variations in the storage tank.
Solution Approach 2:
The system actively regulates pressure parameters through a pressure control mechanism. By monitoring and adjusting pressure dynamically, the system compensates for pressure variations caused by changing liquid levels in the storage tank, ensuring consistent flow delivery to the machining station.
2Use of energy by moving object
If cryogenic liquid is pressurized for better heat exchange, then heat exchange coefficient improves, but gas creation at nozzle increases reducing efficiency
Solution Approach 1:
The system utilizes controlled phase transition by maintaining liquid cryogen in a subcooled state (below its normal boiling point) through heat exchange with colder liquid from the tank bottom. This prevents unwanted gas formation at the nozzle while preserving the liquid phase for effective heat exchange and cooling.
Solution Approach 2:
Different regions of the cryogenic system are assigned different temperatures and phases. The bottom of the tank contains colder liquid for subcooling, the heat exchanger facilitates controlled phase transition, and the nozzle delivers subcooled liquid. This spatial differentiation of thermal properties optimizes both heat exchange and prevents excessive gas creation.
3Stress or pressure
If venting mechanism is used to depressurize tank, then storage pressure can be reduced, but non-recoverable nitrogen vaporization occurs increasing costs
Solution Approach 1:
Instead of discarding vaporized nitrogen through venting, the system recovers it by utilizing the cold liquid at the bottom of the tank to subcool the liquid being supplied. This internal heat exchange recovers the cooling potential that would otherwise be lost, eliminating the need for costly venting while maintaining pressure control.
4Temperature
If heat exchanger is used to subcool liquid, then cryogenic quality improves, but thermal bridging and heat loss occur
Solution Approach 1:
The system converts the potential harm of thermal bridging into a benefit by using the necessary heat exchange pathway to transfer cold from the subcooled liquid at the tank bottom to the liquid being supplied. The heat exchanger, while creating a thermal bridge, is utilized to redistribute cold within the system, turning an energy loss into a useful cooling mechanism.
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 solution stabilizes the pressure and flow rate of cryogenic liquids, enhances heat exchange efficiency, reduces gas creation, and minimizes costs by eliminating non-recoverable nitrogen vaporization, while ensuring consistent cold quality and efficient operation across multiple machining stations.
Implementation Method 1
at least one heat exchanger, immersed in at least one bath of said cryogenic liquid
Implementation Method 2
the said heat exchanger being able to cool the liquid to be supplied
Implementation Method 3
gas is created—due to its expansion—at the outlet of the spray nozzle. The amount of gas generated is directly proportional to the temperature of the liquid nitrogen and its pressure upstream of the nozzle
Implementation Method 4
the pressure of the cryogenic liquid coming from the or each submerged heat exchanger being regulated before it arrives at said machining station
Implementation Method 5
supplying these user stations with frank or substantially frank liquid or subcooled liquid, ie in liquid at lowered pressure, and at lower temperature
Data Source
Figure 1~2
Figure 3
AI summary
A method for supplying subcooled cryogenic liquid to at least one station (P, P1, P2...) carrying out machining operations, from a storage tank (10), said tank containing, under a storage pressure higher than atmospheric pressure, the cryogenic fluid in the liquid phase at the bottom of the tank and in the gaseous phase at the top of the tank, said tank being suitable for supplying said station (P) with liquid drawn from the bottom of the tank (10), and for being provided with fluid from the outside, characterised in that it involves: providing at least one heat exchanger, submerged in at least one bath of said cryogenic liquid (20), controlling (3, 4) the level of the or each bath at a predefined level; passing the cryogenic liquid coming from the storage tank (10) through the or each heat exchanger before said liquid arrives at said machining station(s); regulating (1, 6, 12,13, 61, 62...) the pressure of the cryogenic liquid from the or each submerged exchanger before said liquid arrives at said corresponding machining station.