Bellows Pump Cryogenic Cooling With Stable Heat Exchanger Level
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Solution Overview
Problem
Existing cooling systems that use liquid nitrogen as a coolant face inefficiencies and temperature limitations due to the need for pressurization, which disrupts the cooling effect and requires frequent refilling, limiting the duration of experiments.
Innovation Solution
A thermal analysis cooling system using a positive displacement pump submerged in the cryogenic liquid to provide a continuous flow of liquid nitrogen to a heat exchanger without pressurization, allowing for continuous cooling by vaporization and returning vapor and excess liquid to the dewar for reuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If pressurization is used to transfer liquid nitrogen to the heat exchanger, then the cooling effect is enhanced, but the liquid level becomes unstable and frequent refilling is required
Solution Approach 1:
The system divides the cooling function into two independent parts: a pressurized section for efficient heat transfer and an unpressurized section for stable liquid level maintenance. The heat exchanger is isolated from the pump chamber, allowing the pump to operate in an unpressurized environment while still delivering pressurized coolant to the heat exchange surface.
Solution Approach 2:
The patent introduces an intermediary chamber that acts as a buffer between the unpressurized pump and the heat exchanger. This chamber receives liquid from the pump and provides a controlled environment for phase change, mediating the transition from unpressurized storage to pressurized heat transfer without direct connection between the pump and atmospheric pressure zones.
2Reliability
If liquid flow rate is increased to maintain liquid level, then critical heat flux is prevented, but cooling efficiency decreases due to excessive vapor generation
Solution Approach 1:
The system changes the pressure parameter within the heat exchanger chamber to optimize the boiling process. By maintaining a controlled pressure environment that is higher than atmospheric but lower than full pump pressure, the system achieves more efficient heat transfer at lower flow rates, preventing critical heat flux while minimizing excessive vapor generation and energy loss.
3Ease of operation
If convection cooling is used instead of boiling heat transfer, then temperature control is easier, but cooling efficiency and achievable temperature are significantly reduced
Solution Approach 1:
The system dynamically controls the liquid flow to the heat exchanger to maintain optimal boiling conditions. By adjusting the flow rate to match the heat load and maintaining a constant liquid level in the heat exchanger chamber, the system achieves stable temperature control through boiling heat transfer, combining the efficiency of phase change with the controllability of dynamic flow regulation.
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
Enables continuous sample cooling without interruptions, maintaining stable temperature control and preventing the critical heat flux point, thus allowing experiments to be conducted for any desired length of time without the need for dewar refilling during operation.
Implementation Method 1
a positive displacement pump configured to pump the cryogenic liquid in the dewar through a transfer line as a continuous flow
Implementation Method 2
to provide a cryogenic liquid that cools an experimental sample by vaporization of the cryogenic liquid within the heat exchanger
Implementation Method 3
those that use liquid nitrogen to cool the apparatus by boiling heat transfer
Implementation Method 4
configured to return vapor generated in the heat exchanger and excess liquid to the dewar
Data Source
AI summary
A cooling system employs a single-acting positive displacement bellows pump to transfer a cryogenic liquid such as liquid nitrogen from a storage dewar to a heat exchanger coupled to a measurement chamber of an instrument, wherein cooling takes place by vaporizing the liquid. Preferably, the capacity of the pump is greater than the maximum cooling requirement of the instrument, wherein both vapor resulting from vaporizing of the cryogenic liquid circulated through the heat exchanger and liquid that does not vaporize when circulated through the heat exchanger are returned to the storage dewar, wherein the vapor is subsequently vented from the dewar. Preferably, with the aid of a weir in a return line, the level of liquid in the heat exchanger is maintained full and constant, and the cooling demands are automatically met without the need for other control of the flow rate or level of the liquid. Also, unlike conventional systems, liquid transfer from the dewar does not require dewar pressurization, so that the dewar may be refilled whenever necessary without interrupting the experiment in progress.