4-Valve Pulse Tube Cryocooler Flow Balancing Against Secondary Flow
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Solution Overview
Problem
4-valve pulse tube cryocoolers experience secondary flow and cooling efficiency deterioration due to unbalanced coolant gas flow and bidirectional flow resistance, leading to heat loss and precision issues in flow control valves from accumulated valve dust.
Innovation Solution
The implementation of a 4-valve pulse tube cryocooler design with bidirectional coolant gas flow through flow control valves and the use of a flow resistance member in the third coolant recovery channel to balance gas flow and reduce valve dust accumulation, maintaining cooling efficiency over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a flow control valve is used to control coolant gas flow in a conventional 4-valve pulse tube cryocooler, then cooling efficiency is improved, but bidirectional flow resistance causes unbalanced gas flow and secondary flow that deteriorates cooling performance
Solution Approach 1:
A flow resistance member is introduced as an intermediary element in the coolant gas supply channel to balance the bidirectional flow resistance. This mediator component compensates for the resistance imbalance caused by the flow control valve, preventing secondary flow and maintaining balanced gas flow during both supply and recovery processes.
Solution Approach 2:
The flow resistance of the supply channel is modified by adding a flow resistance member, changing the resistance parameter to match the recovery channel resistance. This parameter adjustment balances the flow characteristics in both directions, eliminating the unbalanced flow and secondary flow that occur with the flow control valve alone.
2Measurement precision
If a flow control valve controls coolant gas flow unidirectionally, then flow control precision is improved, but valve dust accumulates on the valve surface deteriorating control precision over time
Solution Approach 1:
The flow direction through the flow control valve is inverted from unidirectional to bidirectional by placing it in the supply channel where gas flows both toward and away from the pulse tube. This inversion prevents valve dust accumulation on one side of the valve, maintaining control precision stability over time.
Solution Approach 2:
The bidirectional flow through the flow control valve enables self-cleaning of the valve surface. The alternating flow directions prevent dust accumulation by continuously clearing the valve surface, allowing the system to maintain its own precision without external intervention.
3Power
If coolant gas flow is increased to improve cooling performance, then cooling capacity is improved, but unbalanced flow causes secondary circulation that reduces cooling efficiency
Solution Approach 1:
The flow resistance member acts as a counterweight to the flow control valve's resistance, balancing the forces in the supply and recovery channels. This counterbalancing allows high coolant gas flow rates to be used for improved cooling capacity without creating the unbalanced flow that causes secondary circulation and efficiency loss.
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 design significantly reduces secondary flow and valve dust accumulation, maintaining high cooling performance and efficiency for extended periods by ensuring bidirectional coolant gas flow and precise control of coolant gas amounts.
Implementation Method 1
a flow resistance member interposed between the flow control valve and the high-temperature end of the pulse tube
Implementation Method 2
a first on-off valve provided thereon, and a common pipe including a flow control valve provided thereon
Implementation Method 3
The pulse tube cryocooler repeats an operation of flowing a coolant gas (for example, helium gas) that has been compressed by a compressor to a regenerator and a pulse tube
Data Source
AI summary
A 4-valve pulse tube cryocooler has, on a high-pressure end of a compressor, first and second coolant supply channels respectively connected to high-temperature ends of a regenerator and a pulse tube. The cryocooler further has, on a low-pressure end of the compressor, a first coolant recovery channel connected to the high-temperature end of the regenerator, a second coolant recovery channel connected to the high-temperature end of the pulse tube, and a third coolant recovery channel connected to the high-temperature end of the pulse tube via a common pipe and including a flow resistance member interposed between a flow control valve and the high-temperature end of the pulse tube.