Browsing by Author "Hansen, Scott"
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Item Continued Laser Processed Condensing Heat Exchanger Technology Development(48th International Conference on Environmental Systems, 2018-07-08) Hansen, Scott; Castro-Wallace, Sarah; Hamilton, Tanner; Zuhlke, Craig; Alexander, Dennis; Fischer, BillThe reliance on non-permanent coatings in Condensing Heat Exchanger (CHX) designs is a significant technical issue to be solved before long-duration spaceflight can occur. Therefore, high reliability CHXs have been identified by the Evolvable Mars Campaign (EMC) as critical technologies needed to move beyond low earth orbit. In continued pursuit of Laser Processed Condensing Heat Exchanger (LP-CHX) development, a sub-scale LP-CHX coupon was designed and constructed. For construction of this coupon, numerous manufacturing methods were developed. These include development of unique laser processing methods of silver finned surfaces of various thicknesses, laser welding of silver, and unique brazing operations. Additionally, microbial growth testing and long duration condensing is reported in this paper. These studies conclude that silver laser processed surfaces significantly reduce microbial growth and increase the number silver ions found in condensate water.Item Laser Processed Condensing Heat Exchanger (LP-CHX) Test Article Design, Manufacturing, and Testing(50th International Conference on Environmental Systems, 7/12/2021) Hansen, Scott; Wallace, Sarah; Zuhlke, Craig | Alexander, Dennis; Roth, Nick; Ediger, Aaron; Sanders, John; Izenson, Mike; Hamilton, TannerCurrent state-of-the-art Condensing Heat Exchangers (CHXs) require non-permanent coatings which have a history of degrading over time, becoming hydrophobic, and potentially contributing to dimethylsilanediol (DMSD) production on a spacecraft. Ultimately, this type of heat exchanger must be uninstalled and sent back to earth for refurbishment, which is not an option for spaceflight beyond low earth orbit. These significant technical issues must be solved for deep-space spaceflight. In continued pursuit of a high reliability CHX, a silver, dimpled sub-scale Laser Processed CHX (LP-CHX) was designed and manufactured. The LP-CHX does not require a coating, but rather relies only on a femtosecond laser processed silver surface for condensing. This paper highlights the design, development, manufacturing, and testing of the LP-CHX as well as the laser processing of the silver surfaces. Additionally, further microbial growth testing and long duration laser processed condensing tests are reported. These studies conclude that silver laser processed surfaces significantly minimize microbial growth and fungal growth when compared to plain silver and stainless steel metals.Item Laser Processed Condensing Heat Exchanger Technology Development(47th International Conference on Environmental Systems, 2017-07-16) Hansen, Scott; Wright, Sarah; Wallace, Sarah; Hamilton, Tanner; Alexander, Dennis; Zuhlke, Craig; Sanders, JohnThe reliance on non-permanent coatings in Condensing Heat Exchanger (CHX) designs is a significant technical issue to be solved before long-duration spaceflight can occur. Therefore, high reliability CHXs have been identified by the Evolvable Mars Campaign (EMC) as critical technologies needed to move beyond low earth orbit. The Functionalized Condensing Heat Exchanger project aims to solve these problems through the use of femtosecond laser processed surfaces, which have unique wetting properties and potentially anti-microbial growth properties. These surfaces were investigated to identify if they would be suitable candidates for a replacement CHX surface. Among the areas researched in this project include microbial growth testing, siloxane testing in which functionalized surfaces were exposed to an air stream of siloxanes, and condensation testing in which functionalized surfaces were condensed upon.Item Membrane Microgravity Air Conditioner(48th International Conference on Environmental Systems, 2018-07-08) Noyes, Gary; Hansen, Scott; Fricker, JohnMembrane Microgravity Air Conditioner (MMAC) is a microgravity-compatible machine that removes particulates, heat, and humidity from air, and produces very clean humidity condensate. MMAC comprises, in pneumatic series, Particulate Filter (PF), Sensible Heat Exchanger (SHX), Latent Heat Exchanger (LHX), and air fan. MMAC cools and dries air with separate heat exchangers: a plate fin hydrophobic SHX using cool (13 °C) coolant, and a nanoporous-hydrophilic-membrane LHX using cold (4.4 °C) water in a pumped circuit at lower pressure than air flow through LHX. Humidity condenses into the LHX membrane pores, with condensate convecting through the membrane into the cold water circuit flow, driven by the air-to-water pressure difference (deltaP). Bubble-point deltaP of the LHX membrane is higher than its air-to-water deltaP, so air is excluded from the membrane pores. These pores are smaller (0.1-0.2 m diameter) than airborne microbiota, preventing biofilm growth in LHX pores and from entering the condensate circuit. MMAC has no two-phase air-water mixtures, hence is inherently microgravity compatible. A Proof-of-Concept (POC) MMAC produced condensate from humidity in unfiltered room air at undiminished rates continuously for over two months, indicating no performance decrease due to biofilm growth on the LHX membrane. Condensate production rates were positively correlated with air humidity levels; in a crewed spacecraft, this negative feedback keeps air humidity in a narrow range, with minimal engineering control required. Produced condensate was very clean, with total dissolved organic and inorganic contaminant concentrations in the single-digit part-per-million range. Conceptual design was performed of a full-scale spaceflight MMAC with a unique spatial configuration that minimizes air ducting for air conditioner functions. Based on POC MMAC test performance, it is estimated that a full-scale spaceflight MMAC will be significantly smaller and lighter than the International Space Station Condensing Heat Exchanger for the same sensible and latent heat transfer performance.Item Membrane Microgravity Air Conditioner Conceptual Design Progress and Long Duration Test Results(49th International Conference on Environmental Systems, 2019-07-07) Fricker, John; Lottridge, Roger; Hansen, ScottThe Membrane Microgravity Air Conditioner (MMAC) is a microgravity compatible condensing heat exchanger for removal of particulates, humidity, and heat from air, with production of clean condensate, leading to possible applications for Exploration Vehicles as a potential alternative to the current state of the art condensing heat exchangers and centrifugal water separators utilized on the International Space Station (ISS). The MMAC condenses water onto a cold nanoporous-hydrophilic-membrane where the condensate is drawn through the membrane by a negative air-to-water pressure differential into a cold water loop and delivered to a water purification system. A subscale MMAC was designed and tested, and the results were used to develop an ISS Technology Demonstration MMAC Concept and an Exploration MMAC Concept. These concepts addressed volume, mass, power, interfaces, operation and control, maintenance, specifications, redundancy, and reliability. Testing evaluated condensate production rates and the effects of hydrogen peroxide as a biocide under a variety of conditions for six months of continuous testing. The outside of the subscale MMAC condensing membrane was inoculated weekly with three specific skin and environmental microbes as well as a fungus, but they were not observed within the condensate loop fluid during weekly testing. Testing demonstrated the robustness of the MMAC after it experienced two inadvertent shutdowns which resulted in growth of existing condensate loop microbes which did not change the condensation production rate. It was concluded that the weekly hydrogen peroxide protocol was not an effective means of microbial control within the condensate loop as persisting strains of bacterium and fungus developed a resistance to hydrogen peroxide over the six month test. The test hardware and resulting data did not reveal any concerns with proceeding to an ISS Technology Demonstration MMAC. Additional short and long duration MMAC testing with siloxanes at Johnson Space Center is also reported.Item Water Phase Change Heat Exchanger System Level Analysis for Low Lunar Orbit(46th International Conference on Environmental Systems, 2016-07-10) Ungar, Eugene; Navarro, Moses; Hansen, Scott; Sheth, RubikIn low Lunar orbit (LLO) the thermal environment is cyclic – extremely cold in the eclipse and warmer than room temperature near the subsolar point. Phase change material heat exchangers (PCM HXs) are the best option for long term missions in these environments. The Orion spacecraft will use n pentadecane wax PCM HX for its envisioned mission to low Lunar orbit. Using water as a phase change material is attractive because its higher heat of fusion and greater density result in a lighter, more compact PCM HX. To assess the use of a water PCM HX for a human spacecraft in a circular LLO, a system level analysis was performed for the Orion spacecraft. Three cases were evaluated: a) A direct replacement of the wax PCM HX on the internal thermal control loop with a water PCM HX (including control modifications), b) a water PCM HX on the internal thermal control loop with a reduced radiator return setpoint temperature, c) locating the water PCM HX on the external loop with a controlled bypass. The model showed that the water PCM HX could not be used as a drop-in replacement for the wax PCM HX. It did not freeze fully during the eclipse owing to its lower freezing point. Even in the most advantageous location – on the external loop - at least 15% more radiator area than the Orion baseline was required to obtain equivalent performance. The study shows that, although water PCM HXs are attractive at a component level, system level effects mean that they are not a good choice for LLO.