The Experts below are selected from a list of 79377 Experts worldwide ranked by ideXlab platform

Bond, Timothy A. - One of the best experts on this subject based on the ideXlab platform.

  • The International Space Station (ISS) Port 1 (P1) External Active Thermal Control System (EATCS) Ammonia Leak
    2019
    Co-Authors: Metcalf, Jordan L., Cowan, Darnell T., Bond, Timothy A.
    Abstract:

    Ammonia is used in the Starboard 1 (S1) and Port 1 (P1) External Active Thermal Control System (EATCS) to cool the pressurized modules, and some of the external electrical power distribution hardware. Leaks that develop in these critical cooling Systems that deplete in-line tanks can ultimately result in loss of cooling, which can have devastating impacts to the mission, science and crew onboard the ISS. A slow ammonia leak was initially observed from the P1 EATCS in 2011, but later in 2013 the leak rate began to accelerate. The ammonia inventory eventually began to decay exponentially, raising concerns that the inventory could drop to levels where the System would not be operational.The Robotic External Leak Locator (RELL) was built and launched to the ISS to detect and help locate ammonia leaks using the ISS Robotic Arm and remote ground operator Control without constant crew involvement. RELL pinpointed the ammonia leak to the two flexible jumper hose assemblies connecting one of two fluid loops in one of the three deployable radiators to the P1 EATCS. The ammonia inside the two hose assemblies and that radiator fluid loop was isolated and vented to space in 2017. This stopped the leak and an Extravehicular Activity was conducted to remove the two hose assemblies so they could be returned to ground for further Test, Teardown and Evaluation (TT&E). The purpose of this presentation is to discuss this leakage scenario and the TT&E efforts

  • The International Space Station (ISS) Port 1 (P1) External Active Thermal Control System (EATCS) Ammonia Leak
    2019
    Co-Authors: Bond, Timothy A., Metcalf, Jordan L., Cowan, Darnell T.
    Abstract:

    From 2011 to 2017, the crew onboard the International Space Station (ISS) was at risk of dire consequences due to an external ammonia leak. Ammonia is used in the External Active Thermal Control System (EATCS) to cool the pressurized modules and external electrical Systems. Engineers at NASA's Johnson Space Center (JSC) initially detected the leak in one of two cooling loops by monitoring the System ammonia inventory decay over time. White flakes seen on High Definition (HD) cameras were also thought to be associated with the leakage but not confirmed. Initially, the leak was small enough that the ammonia inventory and System operations were not in jeopardy. However, the leak began to accelerate to the point where troubleshooting and corrective action were vital to the sustainability of the ISS. Therefore, it became imperative that the leak be located and repaired for ISS operations to continue. No tools were readily available on the ISS to locate such a leak when it was initially detected, however NASA engineers were already in the process of developing a new device for this purpose called the Robotic External Leak Locator (RELL). The RELL is a robotic instrument package with a mass spectrometer and an ion pressure gauge. Initial checkout operations with RELL happened to coincide with the increasing leak, and ammonia vapors were measured around the P1 EATCS Radiator #3 flexible jumper hoses. The leak stopped after the radiator and its flexible hoses were remotely isolated from the loop and the ammonia from the isolated segment was vented to space. Astronauts conducted a spacewalk that successfully removed the hoses, which were returned to ground for further investigation. The purpose of this paper is to review the leak detection and isolation efforts, investigation results, lessons learned and the recovery plan

Ji Xiang Wang - One of the best experts on this subject based on the ideXlab platform.

  • a gas atomized spray cooling System integrated with an ejector loop ejector modeling and Thermal performance analysis
    Energy Conversion and Management, 2019
    Co-Authors: Ji Xiang Wang, Yi Zhang, Xianwen Ning
    Abstract:

    Abstract Spray cooling has proved to be the promising candidate for the scheme of extremely high heat flux dissipation. The largest innovation of this paper is to develop a novel fluidic organization to realize the application of an air-oriented spray cooling System, considering the operating specialty of the air vehicle. Since an easy availability of the high-pressure air, an air-activated ejector and a gas-atomized nozzle rather than the normal high-pressurized liquid-driven nozzle are adopted. The ejector functions as a pump to collect and recycle the sprayed coolant under various gravitational fields, which is critical for the durable operation of the System. Design procedures of the ejector are developed, based on which a practical ejector is fabricated to be installed in the ground-based System. Heat transfer experiments were organized since there is there is a lack of study on the gas-atomized spray cooling performance. The state of the input high-pressure air and water which is used to generate the spray flow was optimized according to the cooling performance. Basic Thermal laws regarding the gas-atomized spray cooling are attained. The highest the heat flux was 885.4 W/cm2 with a surface temperature of only 85.1 °C which justifies its future application of onboard Thermal Control System.

  • experimental investigation of the Thermal Control effects of phase change material based packaging strategy for on board permanent magnet synchronous motors
    Energy Conversion and Management, 2016
    Co-Authors: Ji Xiang Wang, Yun Ze Li, Sheng-nan Wang, Hong-sheng Zhang, Xianwen Ning
    Abstract:

    Abstract An evolution from traditional hydraulic, pneumatic and mechanic components into general electrical System in the airplane featuring an extensive usage of electro-mechanical actuator has been in the spotlight for the last decade. The widespread availability of such actuators which are commonly driven by permanent magnet synchronous motors will, on the one hand, enhance an overall operating economy, yet on the other hand, it will post a newly generated challenge for the current on-board Thermal Control System since a large amount of waste heat will produce accompanied with the operation of these motors. An ineffective heat rejection path will cause an overheating inside the motors which will lead to a permanent damage easily. It is intolerable for an air-oriented complexity where the reliability, longevity and robustness are the top three priorities. Based on the operating characteristics of the on-board motors, a novel phase change material based motor packaging technology exploiting its huge latent heat is proposed in this paper. Thermal experiments were conducted to analyse the superiority of the proposed strategy quantitatively compared with the conventional fin-based packaging scheme in both constant and intermittent heat generation modes. Systematic design criteria, optimization, performance prediction, etc. were attained via dimensionless studies that aims to acquire a high applicability for more extensive occasions, which is remarked by the discovery of two critical dimensionless factors.

  • A highly self-adaptive cold plate for the single-phase mechanically pumped fluid loop for spacecraft Thermal management
    Energy Conversion and Management, 2016
    Co-Authors: Ji Xiang Wang, Yun Ze Li, Yi Hao Liang, Sheng-nan Wang, Hong-sheng Zhang, Wei Guo, Shao Ping Tian
    Abstract:

    Aiming to improve the conventional single-phase mechanically pumped fluid loop applied in spacecraft Thermal Control System, a novel actively-pumped loop using distributed Thermal Control strategy was proposed. The flow Control System for each branch consists primarily of a Thermal Control valve integrated with a paraffin-based actuator residing in the front part of each corresponding cold plate, where both coolant's flow rate and the cold plate's heat removal capability are well Controlled sensitively according to the heat loaded upon the cold plate due to a conversion between Thermal and mechanical energies. The operating economy enhances remarkably owing to no energy consumption in flow Control process. Additionally, realizing the integration of the sensor, Controller and actuator Systems, it simplifies structure of the traditional mechanically pumped fluid loop as well. Revolving this novel scheme, mathematical model regarding design process of the highly specialized cold plate was entrenched theoretically. A validating System as a prototype was established on the basis of the design method and the scheduled objective of the Controlled temperature (43°C). Then temperature Control performances of the highly self-adaptive cold plate under various operating conditions were tested experimentally. During almost all experiments, the Controlled temperature remains within a range of ±2°C around the set-point. Conclusions can be drawn that this self-driven Control System is stable with sufficient fast transient responses and sufficient small steady-state errors.

Alejandro Torres - One of the best experts on this subject based on the ideXlab platform.

  • numerical simulation of transient operation of loop heat pipes
    Applied Thermal Engineering, 2008
    Co-Authors: Tarik Kaya, Ramon Perez Perez, C Gregori, Alejandro Torres
    Abstract:

    A numerical model is developed to simulate the transient performance characteristics of loop heat pipes (LHP). The model satisfactorily simulates the overall dynamic behavior of an LHP unit tested under ambient and vacuum environments. The startup phase is also reproduced using the experimentally obtained incipient wall superheat. The accurate heat leak predictions at low powers remain problematic and experimental correlation is necessary. The model can be used to analyze the dynamic behavior of an LHP based Thermal Control System exposed to transient Thermal loads.

Yang Yu - One of the best experts on this subject based on the ideXlab platform.

  • solid sorption heat pipe coupled with direct air cooling technology for Thermal Control of rack level in internet data centers design and numerical simulation
    International Journal of Heat and Mass Transfer, 2019
    Co-Authors: Yang Yu
    Abstract:

    Abstract The utilization of direct/indirect free cooling (natural cold source) method for data center (DC) cooling and Thermal management System has great potential in reducing electric energy consumption. Integrating heat pipe indirect and passive heat transfer method with active vapor-compression refrigeration technique is considered as a promising and alternative solution. The proposal of solid sorption heat pipe is expected to alleviate the drawbacks of heat transfer limits in both conventional heat pipe and thermosyphon. Here, a novel dual-mode Thermal Control System coupled solid sorption heat pipe with direct air convection scheme for rack level cooling of DC is designed and three-dimensional calculation models are set up to simulate the flow and temperature fields for DC room level and rack level, respectively. Experimental results of solid sorption heat pipe with NaBr show that the maximum axial heat flux with different filing amount and different inclination angle are 913.3 kW/m2 and 559.7 kW/m2, respectively. The parameterized simulation results for rack level cooling of DC illustrate that when flow rate of supply air is 2 m/s and heat dissipation of single server reaches 1000 W, this novel dual-mode Thermal management scheme could reduce the peak temperature of server from 75.8 °C to 68.8 °C. A case study based on typical DC scale further elaborates that the dual-mode Thermal Control oriented to rack level is feasible for energy-saving of DC cooling System.

Cowan, Darnell T. - One of the best experts on this subject based on the ideXlab platform.

  • The International Space Station (ISS) Port 1 (P1) External Active Thermal Control System (EATCS) Ammonia Leak
    2019
    Co-Authors: Metcalf, Jordan L., Cowan, Darnell T., Bond, Timothy A.
    Abstract:

    Ammonia is used in the Starboard 1 (S1) and Port 1 (P1) External Active Thermal Control System (EATCS) to cool the pressurized modules, and some of the external electrical power distribution hardware. Leaks that develop in these critical cooling Systems that deplete in-line tanks can ultimately result in loss of cooling, which can have devastating impacts to the mission, science and crew onboard the ISS. A slow ammonia leak was initially observed from the P1 EATCS in 2011, but later in 2013 the leak rate began to accelerate. The ammonia inventory eventually began to decay exponentially, raising concerns that the inventory could drop to levels where the System would not be operational.The Robotic External Leak Locator (RELL) was built and launched to the ISS to detect and help locate ammonia leaks using the ISS Robotic Arm and remote ground operator Control without constant crew involvement. RELL pinpointed the ammonia leak to the two flexible jumper hose assemblies connecting one of two fluid loops in one of the three deployable radiators to the P1 EATCS. The ammonia inside the two hose assemblies and that radiator fluid loop was isolated and vented to space in 2017. This stopped the leak and an Extravehicular Activity was conducted to remove the two hose assemblies so they could be returned to ground for further Test, Teardown and Evaluation (TT&E). The purpose of this presentation is to discuss this leakage scenario and the TT&E efforts

  • The International Space Station (ISS) Port 1 (P1) External Active Thermal Control System (EATCS) Ammonia Leak
    2019
    Co-Authors: Bond, Timothy A., Metcalf, Jordan L., Cowan, Darnell T.
    Abstract:

    From 2011 to 2017, the crew onboard the International Space Station (ISS) was at risk of dire consequences due to an external ammonia leak. Ammonia is used in the External Active Thermal Control System (EATCS) to cool the pressurized modules and external electrical Systems. Engineers at NASA's Johnson Space Center (JSC) initially detected the leak in one of two cooling loops by monitoring the System ammonia inventory decay over time. White flakes seen on High Definition (HD) cameras were also thought to be associated with the leakage but not confirmed. Initially, the leak was small enough that the ammonia inventory and System operations were not in jeopardy. However, the leak began to accelerate to the point where troubleshooting and corrective action were vital to the sustainability of the ISS. Therefore, it became imperative that the leak be located and repaired for ISS operations to continue. No tools were readily available on the ISS to locate such a leak when it was initially detected, however NASA engineers were already in the process of developing a new device for this purpose called the Robotic External Leak Locator (RELL). The RELL is a robotic instrument package with a mass spectrometer and an ion pressure gauge. Initial checkout operations with RELL happened to coincide with the increasing leak, and ammonia vapors were measured around the P1 EATCS Radiator #3 flexible jumper hoses. The leak stopped after the radiator and its flexible hoses were remotely isolated from the loop and the ammonia from the isolated segment was vented to space. Astronauts conducted a spacewalk that successfully removed the hoses, which were returned to ground for further investigation. The purpose of this paper is to review the leak detection and isolation efforts, investigation results, lessons learned and the recovery plan