Gravity-Driven Two-Phase Fluid Loop Compatibility Test
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Solution Overview
Problem
The compatibility between the ammonia working medium and the material of the gravity-driven two-phase fluid loop in spacecraft thermal control systems is challenging due to the generation of non-condensable gases like nitrogen and hydrogen, which increases system pressure and reduces heat transfer efficiency, especially under high-temperature conditions.
Innovation Solution
A test device and method that simulate the decomposition process of ammonia under high-temperature conditions using a sealed and hollow gravity heat pipe, filled with ammonia, to measure the amount of non-condensable gases generated, and determine compatibility by comparing temperature increments after filling highly-pure nitrogen into the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If ammonia is used as working medium in gravity-driven two-phase fluid loop, then heat transfer efficiency is improved, but non-condensable gases are generated that increase system pressure and reduce performance
Solution Approach 1:
The patent applies preliminary action by pre-filling the test device with highly-pure nitrogen before conducting compatibility tests. This allows the system to simulate the presence of non-condensable gases in advance, enabling researchers to evaluate their impact on heat transfer performance before actual ammonia decomposition occurs in the operational system. The nitrogen filling creates a controlled environment to study harmful gas effects without waiting for natural decomposition.
Solution Approach 2:
The patent uses highly-pure nitrogen as an intermediary substance to represent non-condensable gases. Instead of directly measuring decomposition products from ammonia, the nitrogen acts as a substitute that mimics the behavior of non-condensable gases in terms of pressure contribution and heat transfer interference. This intermediary approach allows safe and controlled study of harmful gas effects without the complexity of actual decomposition reactions.
2Measurement precision
If high-temperature testing is performed to obtain evaporator conditions, then decomposition process can be observed, but direct testing in gravity-driven two-phase fluid loop is difficult
Solution Approach 1:
The patent applies segmentation by dividing the testing function into a separate, dedicated test device rather than attempting to modify the complex gravity-driven two-phase fluid loop system. The test device is segmented into distinct components: a test chamber for ammonia decomposition, temperature control systems, pressure measurement devices, and nitrogen filling mechanisms. This segmentation allows high-temperature decomposition testing to be performed in isolation from the operational thermal control system, simplifying the testing process while maintaining measurement precision.
Solution Approach 2:
The patent uses copying by creating a simplified replica test device that mimics the key characteristics of the evaporator environment without requiring the full complexity of the gravity-driven two-phase fluid loop. The test device copies essential features such as temperature ranges, pressure conditions, and material compositions, allowing decomposition processes to be studied in a controlled, simplified environment that accurately represents operational conditions without the complexity of the complete system.
3Productivity
If nickel catalyst is used at 250-260°C, then ammonia decomposition is accelerated, but compatibility problems arise between ammonia and loop material
Solution Approach 1:
The patent applies parameter changes by systematically varying temperature, pressure, and ammonia concentration parameters in the test device to simulate different operational conditions. By controlling these parameters, the study examines how nickel catalyst performance and material compatibility change under different thermal and pressure conditions. This allows identification of safe operating ranges where decomposition efficiency is maintained without excessive material degradation or incompatible reactions.
Solution Approach 2:
The patent uses disposable or replaceable test chambers and material samples in the test device. Instead of subjecting the entire gravity-driven two-phase fluid loop system to harsh decomposition conditions, small, inexpensive test components are used that can be easily replaced after testing. This approach allows aggressive decomposition testing with nickel catalyst at high temperatures without risking damage to the valuable operational system, enabling thorough compatibility studies with minimal risk.
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 test device effectively simulates the decomposition process, allowing for easy determination of compatibility between the ammonia working medium and the material of the gravity-driven two-phase fluid loop, ensuring efficient heat transfer and preventing errors from gas mixtures.
Implementation Method 1
ammonia generates non-condensable gases that are insoluble in liquid ammonia such as nitrogen and hydrogen
Implementation Method 2
Under the condition that the nickel element is used as a catalyst, and the temperature is up to 250°C to 260°C, ammonia generates non-condensable gases
Implementation Method 3
the ammonia working medium in the evaporator 1 absorbs heat of an isotopic heat source and performs phase change to get gas
Implementation Method 4
after transferring heat to a moon surface probe device through the condenser pipeline 3, the gaseous ammonia working medium is condensed into liquid
Implementation Method 5
under the effect of gravity, the liquid ammonia working medium flows into the evaporator along the liquid pipeline 6
Data Source
Figure 1~2
AI summary
Provided are a device and a method for testing the compatibility of a gravity-driven two-phase fluid loop. The test device and method can effectively simulate the decomposition process of an ammonia working substance in the gravity-driven two-phase fluid loop in the case of a high temperature with nickel as a catalyst to judge the compatibility of the gravity-driven two-phase fluid loop. Firstly, a test device for simulating the decomposition process of the ammonia working substance in the gravity-driven two-phase fluid loop during a moon day is designed, then the amount of non-condensable gases produced during a moon day from the ammonia working substance in the test device is measured using a method for testing a non-condensable gas in a gravity assisted heat pipe, and then a high-purity nitrogen in the same substance amount as that of the non-condensable gases is filled into the gravity-driven two-phase fluid loop to achieve the determination of the compatibility of the gravity-driven two-phase fluid loop. The test device is simple, and the test method is rapid, convenient and effective.