Joule-Thomson Cryocooler Heat Conduction Path to Reduce Cool-Down Time
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Solution Overview
Problem
Existing Joule-Thomson (JT) cryocoolers require a lengthy cool-down time to reach cryogenic temperatures due to inefficient pre-cooling mechanisms, particularly when using fixed orifices, which hinder rapid refrigerant gas cooling to inversion temperatures.
Innovation Solution
Incorporation of a heat conduction path connecting pre-cooling stages to heat exchangers in the refrigerant circuit, enabling conductive cooling and reducing the cool-down time by leveraging the thermal conductivity of materials like copper and aluminum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a pre-cooling cryocooler is used to cool refrigerant gas to inversion temperature, then JT expansion cooling can be achieved, but the cool-down time becomes excessively long (approximately 24 hours)
Solution Approach 1:
The cooling system is divided into two independent cooling paths: (1) refrigerant pipe cooling where pre-cooled refrigerant gas cools subsequent refrigerant, and (2) heat conduction path cooling where the pre-cooling stage directly conducts heat to the heat exchanger. This segmentation allows both paths to operate simultaneously, dramatically reducing cool-down time while achieving the required inversion temperature for JT expansion
Solution Approach 2:
The heat conduction path acts as an intermediary thermal bridge between the pre-cooling stage and the heat exchanger. This intermediary path provides an additional heat transfer route that bypasses the limitations of refrigerant-only cooling, enabling faster heat extraction from the heat exchanger during the cool-down phase
2Temperature
If refrigerant gas is cooled through JT expansion in a JT valve, then cryogenic temperatures can be achieved, but the refrigerant gas must first be pre-cooled to inversion temperature which extends the cool-down period
Solution Approach 1:
The pre-cooling function is segmented into two parallel mechanisms: refrigerant-based cooling and direct heat conduction cooling. This allows the system to achieve inversion temperature faster by operating both mechanisms simultaneously, reducing the bottleneck in preparing refrigerant gas for JT expansion
Solution Approach 2:
The pre-cooling stage performs preliminary cooling action on both the refrigerant gas and the heat exchanger structure itself through the heat conduction path. This preliminary action on the heat exchanger reduces its thermal mass that needs to be cooled later, thereby accelerating the overall cool-down process before JT expansion begins
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 implementation of a heat conduction path significantly shortens the cool-down time from approximately 24 hours to around 12 hours, enhancing the efficiency and speed of JT cryocooler operation.
Implementation Method 1
a JT valve that enables cooling of a refrigerant gas using JT expansion
Implementation Method 2
a heat conduction path that is provided separately from the refrigerant pipe and connects the pre-cooling stage to the heat exchanger to enable conductive cooling of the heat exchanger through the pre-cooling stage
Data Source
AI summary
A Joule-Thomson cryocooler includes a pre-cooling cryocooler that includes a pre-cooling stage, a refrigerant circuit that includes a heat exchanger and a refrigerant pipe extending from the heat exchanger and cooled by the pre-cooling stage, and a heat conduction path that is provided separately from the refrigerant pipe and connects the pre-cooling stage to the heat exchanger to enable conductive cooling of the heat exchanger through the pre-cooling stage.