Results for “APPROPRIATE TECHNOLOGY” — Page 26

NASA NTRS1988

Applications of nuclear power to lunar and Mars missions

The initial elements of an ambitious program for human exploration beyond Earth have been developed and presented to NASA management for its consideration. The Outpost on the Moon and Humans to Mars are two key U.S. programs (Ride 1987). A major space goal of this magnitude can only be implemented by a series of program phases evolving from precursor robotic missions, to initial development of temporary surface stations and buildup of operational experience, through the eventual establishment of permanent and sustained surface bases. Each phase of the separate (or linked) lunar and Mars scenarios will require distinctly different levels and types of power sources to support both transportation and on-surface operations, i.e., the nuclear power reactor. Discussed are the respective types and specific amounts of power required for all major systems in a phased program of lunar and Mars exploration over the period 1990 to 2040. A comparative assessment of technology tradeoffs and special design problems is made to ascertain the most appropriate application for the different phases, as well as to identify synergistic developments across the programs.

Friedlander, Alan↗

NASA NTRS1990

Test plan pressure fed thrust chamber technology

Aerojet is developing the technology for the design of a reliable, low cost, efficient, and lightweight LOX/RP-1 pressure fed engine. This technology program is a direct result of Aerojet's liquid rocket booster (LRB) study and previous NASA studies that identified liquid engines using high bulk density hydrocarbon fuels as very attractive for a space transportation system (STS). Previous large thrust LOX/RP-1 engine development programs were characterized by costly development problems due to combustion instability damage. The combustion stability solution was typically obtained through trial and error methods of minimizing instability damage by degrading engine performance. The approach to this program was to utilize existing and newly developed combustion analysis models and design methodology to create a thrust chamber design with features having the potential of producing reliable and efficient operation. This process resulted in an engine design with a unique high thrust-per-element OFO triplet injector utilizing a low cost modular approach. Cost efficient ablative materials are baselined for the injector face and chamber. Technology demonstration will be accomplished through a hot fire test program using appropriately sized subscale hardware. This subscale testing will provide a data base to supplement the current industry data bank and to anchor and validate the applied analysis models and design methodology. Once anchored and validated, these analysis models and design methodology can be applied with greatly increased confidence to design and characterize a large scale pressure fed LOX/RP-1 thrust chamber. The objective of this test program is to generate a data base that can be used to anchor and validate existing analysis models and design methodologies and to provide early concept demonstration of a low cost, efficient LOX/RP-1 thrust chamber. Test conditions and hardware instrumentation were defined to provide data sufficient to characterize combustion stability, performance, and thermal operation over a wide thrust chamber throttling range.

Dunn, Glenn↗

NASA NTRS1997

Microgravity Science and Applications: Program Tasks and Bibliography for Fiscal Year 1996

NASA's Microgravity Science and Applications Division (MSAD) sponsors a program that expands the use of space as a laboratory for the study of important physical, chemical, and biochemical processes. The primary objective of the program is to broaden the value and capabilities of human presence in space by exploiting the unique characteristics of the space environment for research. However, since flight opportunities are rare and flight research development is expensive, a vigorous ground-based research program, from which only the best experiments evolve, is critical to the continuing strength of the program. The microgravity environment affords unique characteristics that allow the investigation of phenomena and processes that are difficult or impossible to study an Earth. The ability to control gravitational effects such as buoyancy driven convection, sedimentation, and hydrostatic pressures make it possible to isolate phenomena and make measurements that have significantly greater accuracy than can be achieved in normal gravity. Space flight gives scientists the opportunity to study the fundamental states of physical matter-solids, liquids and gasses-and the forces that affect those states. Because the orbital environment allows the treatment of gravity as a variable, research in microgravity leads to a greater fundamental understanding of the influence of gravity on the world around us. With appropriate emphasis, the results of space experiments lead to both knowledge and technological advances that have direct applications on Earth. Microgravity research also provides the practical knowledge essential to the development of future space systems. The Office of Life and Microgravity Sciences and Applications (OLMSA) is responsible for planning and executing research stimulated by the Agency's broad scientific goals. OLMSA's Microgravity Science and Applications Division (MSAD) is responsible for guiding and focusing a comprehensive program, and currently manages its research and development tasks through five major scientific areas: biotechnology, combustion science, fluid physics, fundamental physics, and materials science. FY 1996 was an important year for MSAD. NASA continued to build a solid research community for the coming space station era. During FY 1996, the NASA Microgravity Research Program continued investigations selected from the 1994 combustion science, fluid physics, and materials science NRAS. MSAD also released a NASA Research Announcement in microgravity biotechnology, with more than 130 proposals received in response. Selection of research for funding is expected in early 1997. The principal investigators chosen from these NRAs will form the core of the MSAD research program at the beginning of the space station era. The third United States Microgravity Payload (USMP-3) and the Life and Microgravity Spacelab (LMS) missions yielded a wealth of microgravity data in FY 1996. The USMP-3 mission included a fluids facility and three solidification furnaces, each designed to examine a different type of crystal growth.

Source record↗

NASA NTRS2004

Development of an Aircraft Approach and Departure Atmospheric Profile Generation Algorithm

In support of NASA Virtual Airspace Modeling and Simulation (VAMS) project, an effort was initiated to develop and test techniques for extracting meteorological data from landing and departing aircraft, and for building altitude based profiles for key meteorological parameters from these data. The generated atmospheric profiles will be used as inputs to NASA s Aircraft Vortex Spacing System (AVOLSS) Prediction Algorithm (APA) for benefits and trade analysis. A Wake Vortex Advisory System (WakeVAS) is being developed to apply weather and wake prediction and sensing technologies with procedures to reduce current wake separation criteria when safe and appropriate to increase airport operational efficiency. The purpose of this report is to document the initial theory and design of the Aircraft Approach Departure Atmospheric Profile Generation Algorithm.

Buck, Bill K.↗

NASA NTRS2012

Coronagraph Focal-Plane Phase Masks Based on Photonic Crystal Technology: Recent Progress and Observational Strategy

Photonic crystal, an artificial periodic nanostructure of refractive indices, is one of the attractive technologies for coronagraph focal-plane masks aiming at direct imaging and characterization of terrestrial extrasolar planets. We manufactured the eight-octant phase mask (8OPM) and the vector vortex mask (VVM) very precisely using the photonic crystal technology. Fully achromatic phase-mask coronagraphs can be realized by applying appropriate polarization filters to the masks. We carried out laboratory experiments of the polarization-filtered 8OPM coronagraph using the High-Contrast Imaging Testbed (HCIT), a state-of-the-art coronagraph simulator at the Jet Propulsion Laboratory (JPL). We report the experimental results of 10-8-level contrast across several wavelengths over 10% bandwidth around 800nm. In addition, we present future prospects and observational strategy for the photonic-crystal mask coronagraphs combined with differential imaging techniques to reach higher contrast. We proposed to apply a polarization-differential imaging (PDI) technique to the VVM coronagraph, in which we built a two-channel coronagraph using polarizing beam splitters to avoid a loss of intensity due to the polarization filters. We also proposed to apply an angular-differential imaging (ADI) technique to the 8OPM coronagraph. The 8OPM/ADI mode avoids an intensity loss due to a phase transition of the mask and provides a full field of view around central stars. We present results of preliminary laboratory demonstrations of the PDI and ADI observational modes with the phase-mask coronagraphs.

coronagraphy↗

NASA NTRS2017

Towards Designing Graceful Degradation into Trajectory Based Operations: A Human-Systems Integration Approach

One of the most fundamental changes to the air traffic management system in NextGen is the concept of trajectory based operations (TBO). With the introduction of such change, system safety and resilience is a critical concern, in particular, the ability of systems to gracefully degrade. In order to design graceful degradation into a TBO envrionment, knowledge of the potential causes of degradation, and appropriate solutions, is required. In addition, previous research has predominantly explored the technological contribution to graceful degradation, frequently neglecting to consider the role of the human operator, specifically, air traffic controllers (ATCOs). This is out of step with real-world operations, and potentially limits an ecologically valid understanding of achieving graceful degradation in an air traffic control (ATC) environment. The following literature review aims to identify and summarize the literature to date on the potential causes of degradation in ATC and the solutions that may be applied within a TBO context, with a specific focus on the contribution of the air traffic controller. A framework of graceful degradation, developed from the literature, is presented. It is argued that in order to achieve graceful degradation within TBO, a human-system integration approach must be applied.

human-system integration↗

NASA NTRS2017

Towards Designing Graceful Degradation into Trajectory Based Operations: A Human-Machine System Integration Approach

One of the most fundamental changes to the air traffic management system in NextGen is the concept of trajectory based operations (TBO). With the introduction of such change, system safety and resilience is a critical concern, in particular, the ability of systems to gracefully degrade. In order to design graceful degradation into a TBO envrionment, knowledge of the potential causes of degradation, and appropriate solutions, is required. In addition, previous research has predominantly explored the technological contribution to graceful degradation, frequently neglecting to consider the role of the human operator, specifically, air traffic controllers (ATCOs). This is out of step with real-world operations, and potentially limits an ecologically valid understanding of achieving graceful degradation in an air traffic control (ATC) environment. The following literature review aims to identify and summarize the literature to date on the potential causes of degradation in ATC and the solutions that may be applied within a TBO context, with a specific focus on the contribution of the air traffic controller. A framework of graceful degradation, developed from the literature, is presented. It is argued that in order to achieve graceful degradation within TBO, a human-system integration approach must be applied.

human-system integration↗

NASA NTRS2017

Towards Designing Graceful Degradation into Trajectory Based Operations: A Human-Machine System Integration Approach

One of the most fundamental changes to the air traffic management system in NextGen is the concept of trajectory based operations (TBO). With the introduction of such change, system safety and resilience is a critical concern, in particular, the ability of systems to gracefully degrade. In order to design graceful degradation into a TBO envrionment, knowledge of the potential causes of degradation, and appropriate solutions, is required. In addition, previous research has predominantly explored the technological contribution to graceful degradation, frequently neglecting to consider the role of the human operator, specifically, air traffic controllers (ATCOs). This is out of step with real-world operations, and potentially limits an ecologically valid understanding of achieving graceful degradation in an air traffic control (ATC) environment. The following literature review aims to identify and summarize the literature to date on the potential causes of degradation in ATC and the solutions that may be applied within a TBO context, with a specific focus on the contribution of the air traffic controller. A framework of graceful degradation, developed from the literature, is presented. It is argued that in order to achieve graceful degradation within TBO, a human-system integration approach must be applied.

trajectory based operations↗

NASA NTRS1995

Preparation of Thermoelectric Materials From Melts

A review of melt preparation techniques is presented covering necessary phase relationships, synthesis/alloying and crystal growth of thermoelectric materials. The processes described require the knowledge of composition-temperature or composition- temperature-pressure phase diagrams. This knowledge enables the selection of the appropriate method of preparation, apparatus design and processing. The materials, from a technological point of view, will be roughly divided into three categories: low temperature materials (group V chalcogenides based on Bi2Te3), middle temperature materials (group IV chalcogenides based on PbTe) and high temperature materials (Si-Ge solid solutions). All known methods of preparation from melts are described, and a comparative analysis is given. (complete abstract)

thermoelectrics↗

NASA NTRSDate not supplied

Navigation Sensor Technology Assessment Capability for Data-Driven Systems Analysis

The capability to assess the mission performance of novel navigation technologies from a systems-level approach and to provide quantitative results is crucial. With growing interest and innovations from NASA’s commercial partners, data-driven results that quantify the technological impact will guide research developments and facilitate stakeholder decision-making while requiring less time and resources. This paper presents a method to evaluate various sensor combinations and their impact on the overall system performance using an existing six degrees-of-freedom, physics-based engineering simulation for a government reference lunar lander as a testbed. Selected navigation technologies over various technology readiness levels, including Inertial Measurement Units, Navigation Doppler Lidar, and radar altimeter-radar velocimeter, were studied in this paper. Results using this testbed to perform sensitivity studies and to provide quantitative assessments are reported. One key finding is that there are diminishing returns for reducing sensor errors. The most influential sensor parameter to landing success are vehicle configuration and mission dependent. Results from this method could be used by stakeholders to make data-driven systems-based decisions and by technology developers as guidance for the specific parameter improvements that will have the most significant impact on mission success. This capability could be further used to assess alternative scenarios should one type of technology become unavailable or to re-assess initial assumptions and identify appropriate requirements from a system perspective.

Esther Lee↗

DOE OSTI2023

Wind RD&T: On Site Wind for Rural Load Centers

This presentation will provide an overview of the "On Site Wind for Rural Load Center" project for an FY23 research, development, and technology review with other Wind Energy Technologies Office researchers and DOE program managers. This copy of slides is appropriate for public release.

17 WIND ENERGY↗

NASA NTRSDate not supplied

An Analysis of Exploration Capability Gaps for Future Habitation Systems to Inform Risk Assessment and Development Priorities

Within NASA, exploration capability gaps are defined as the difference between the current state-of-the-art in capabilities and the anticipated needs of future human spaceflight architectures. As NASA and its partners’ capabilities for human exploration of deep space continue to mature, it is necessary to understand the capability gaps that require closure to support future habitation systems, such as the Lunar Surface Habitat (SH) and Mars Transit Habitat (TH) currently in concept development. This paper will identify high-priority capability gaps for exploration habitation and show potential options for gap closure through investment in technology, development, and testing. High-priority capability gaps are divided into the following general taxonomy areas: human health/life support/habitation systems, flight computing and avionics, power and energy storage, communications and navigation, thermal management systems, human exploration destination systems, autonomous systems, sensors and instruments, GNC (guidance, navigation, and control), robotic systems, ground and uncrewed surface systems, and materials/structures/mechanical systems/manufacturing. In the gap identification process, teams of discipline experts from across NASA reviewed the latest habitation architecture needs against current capabilities to understand where gaps may exist. The results of the assessment established a basis for the current state-of-the-art within each gap and identified the capability needs of the proposed exploration missions the gap links to. An assessment of how each test platform (e.g., Ground, International Space Station (ISS), Commercial Low Earth Orbit (LEO) Destinations, Gateway) may be leveraged to mature capabilities and potentially provide a route to gap closure will be discussed. The notional timeline for gap closure to support reference missions and impacts to overall schedule are also assessed where appropriate. Based on the capability gap analysis described above, the paper summarizes important technology maturation considerations for human exploration architectures, with a focus on the Mars TH. The previously published NASA habitation ground rules and assumptions document is used as the basis to classify gaps as enabling, enhancing, or “push” opportunities for a particular architecture. Stepwise technology maturation plans/considerations are presented for some selected critical gaps. Overall, the analysis in this paper is intended to help influence development priorities for habitation systems, where high-priority, critical gaps are those currently assessed as having a low probability of closure by the anticipated need date. Capability gap analysis also informs the risk register for exploration habitation systems and mitigation strategies to ensure readiness of key technologies to support future mission timelines. Linkage between capability gaps for Moon and Mars is noted, as closure of a gap at a Lunar destination may subsequently enable or enhance Mars TH architectures.

technology development↗

NASA NTRSDate not supplied

An Analysis of Exploration Capability Gaps for Future Habitation Systems to Inform Risk Assessment and Development Priorities

Within NASA, exploration capability gaps are defined as the difference between the current state-of-the-art in capabilities and the anticipated needs of future human spaceflight architectures. As NASA and its partners’ capabilities for human exploration of deep space continue to mature, it is necessary to understand the capability gaps that require closure to support future habitation systems, such as the Lunar Surface Habitat (SH) and Mars Transit Habitat (TH) currently in concept development. This paper will identify high-priority capability gaps for exploration habitation and show potential options for gap closure through investment in technology, development, and testing. High-priority capability gaps are divided into the following general taxonomy areas: human health/life support/habitation systems, flight computing and avionics, power and energy storage, communications and navigation, thermal management systems, human exploration destination systems, autonomous systems, sensors and instruments, GNC (guidance, navigation, and control), robotic systems, ground and uncrewed surface systems, and materials/structures/mechanical systems/manufacturing. In the gap identification process, teams of discipline experts from across NASA reviewed the latest habitation architecture needs against current capabilities to understand where gaps may exist. The results of the assessment established a basis for the current state-of-the-art within each gap and identified the capability needs of the proposed exploration missions the gap links to. An assessment of how each test platform (e.g., Ground, International Space Station (ISS), Commercial Low Earth Orbit (LEO) Destinations, Gateway) may be leveraged to mature capabilities and potentially provide a route to gap closure will be discussed. The notional timeline for gap closure to support reference missions and impacts to overall schedule are also assessed where appropriate. Based on the capability gap analysis described above, the paper summarizes important technology maturation considerations for human exploration architectures, with a focus on the Mars TH. The previously published NASA habitation ground rules and assumptions document is used as the basis to classify gaps as enabling, enhancing, or “push” opportunities for a particular architecture. Stepwise technology maturation plans/considerations are presented for some selected critical gaps. Overall, the analysis in this paper is intended to help influence development priorities for habitation systems, where high-priority, critical gaps are those currently assessed as having a low probability of closure by the anticipated need date. Capability gap analysis also informs the risk register for exploration habitation systems and mitigation strategies to ensure readiness of key technologies to support future mission timelines. Linkage between capability gaps for Moon and Mars is noted, as closure of a gap at a Lunar destination may subsequently enable or enhance Mars TH architectures.

technology development↗

NASA NTRS2007

Metabolic Heat Regenerated Temperature Swing Adsorption for CO(sub 2) and Heat Removal/Rejection in a Martian PLSS

Two of the fundamental problems facing the development of a Portable Life Support System (PLSS) for use on Mars, are (i) heat rejection (because traditional technologies use sublimation of water, which wastes a scarce resource and contaminates the premises), and (ii) rejection of CO2 in an environment with a ppCO2 of 0.4-0.9 kPa. Patent-pending Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed to address both these challenges. The technology utilizes an adsorbent that when cooled with liquid CO2 to near sublimation temperatures (~195K) removes metabolically-produced CO2 in the vent loop. Once fully loaded, the adsorbent is then warmed externally by the vent loop (approx. 300K), rejecting the captured CO2 to Mars ambient. Two beds are used to effect a continuous cycle of CO2 removal/rejection as well as facilitate heat exchange out of the vent loop. Any cryogenic fluid can be used in the application; however, since CO2 is readily available at Mars and can be easily produced and stored on the Martian surface, the solution is rather elegant and less complicated when employing liquid CO2. As some metabolic heat will need to be rejected anyway, finding a practical use for metabolic heat is also an overall benefit to the PLSS. To investigate the feasibility of the technology, a series of experiments was conducted which lead to the selection and partial characterization of an appropriate adsorbent. The adsorbent NaX successfully removed CO2 from a simulated vent loop at the prescribed temperature swing anticipated during PLSS operating conditions on Mars using a cryogenic fluid. Thermal conductivity of the adsorbent was also measured to eventually aid in a demonstrator design of the technology. These results provide no show stoppers to the development of MTSA technology and allow its development to focus on other design challenges as listed in the conclusions.

Iacomini, Christine↗

DOE OSTI2022

Modeling and Simulation of Air-Source CO2 Heat Pump Water Heater

Carbon dioxide (CO2) has been widely used as working fluid for the vapor-compression refrigeration systems in large marine device. Due to the potential energy efficiency and the favorable environmental properties of CO2 as a working fluid, CO2 heat pump water heater (HPWH) systems are regarded a promising technology for centralized domestic hot water (DHW) heating in residential and commercial buildings. However, there is still at the early stage of appropriately optimizing and improving the energy performance of CO2 HPWH. This requires CO2 HPWH simulation tools capable of capturing the accurate impact of the emerging compressor, throttle device, and heat exchanger technology on CO2 heat transfer and energy efficiency. In this study, high efficiency components (compressors, pumps, fans, heat exchangers) were identified and applied to the state-of-art CO2 HPWH designs and analyzed their performance by using numerical simulation. This was done by simulating the performance of CO2 HPWH using ACMODEL design model combined with the component models developed at Oak Ridge National Laboratory (ORNL) for orifice tube, map-based compressor, and tube-in-tube gas cooler. ACMODEL is an equipment design model for CO2-based air conditioners and heat pumps developed by Purdue University to account for the details of each component. The simulated CO2 HPWH performance was then compared with the heat pump water heater using conventional refrigerants.

Gao, Zhiming↗

NASA NTRS2007

Metabolic Heat Regenerated Temperature Swing Adsorption for CO2 and Heat Removal/Rejection in a Martian PLSS

Two of the fundamental problems facing the development of a Portable Life Support System (PLSS) for use on Mars, are (i) heat rejection (because traditional technologies use sublimation of water, which wastes a scarce resource and contaminates the premises), and (ii) rejection of carbon dioxide (CO2) in an environment with a CO2 partial pressure (ppCO2) of 0.4-0.9 kPa. Patent-pending Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed to address both these challenges. The technology utilizes an adsorbent that when cooled with liquid CO2 to near sublimation temperatures (~195K) removes metabolically-produced CO2 in the ventilation loop. Once fully loaded, the adsorbent is then warmed externally by the ventilation loop (~300K), rejecting the captured CO2 to Mars ambient. Two beds are used to provide a continuous cycle of CO2 removal/rejection as well as facilitate heat exchange out of the ventilation loop. Any cryogenic fluid can be used in the application; however, since CO2 is readily available on Mars and can be easily produced and stored on the Martian surface, the solution is rather elegant and less complicated when employing liquid CO2. As some metabolic heat will need to be rejected anyway, finding a practical use for metabolic heat is also an overall benefit to the PLSS. To investigate the feasibility of the technology, a series of experiments were conducted which lead to the selection and partial characterization of an appropriate adsorbent. The Molsiv Adsorbents 13X 8x12 (also known as NaX zeolite) successfully removed CO2 from a simulated ventilation loop at the prescribed temperature swing anticipated during PLSS operating conditions on Mars using a cryogenic fluid. Thermal conductivity of the adsorbent was also measured to eventually aid in a demonstrator design of the technology. These results provide no show stoppers to the development of MTSA technology and allow its development to focus on other design challenges as listed in the conclusions section of this paper.

Iacomini, Christine↗

NASA NTRS2003

Scale Model Experiments on Sound Propagation From a Mach 2.5 Cold Nitrogen Jet Flowing Through a Rigid-Walled Duct With a J-Deflector

The Launch Systems Testbed (LST) represents the evolution of vibroacoustics research and development work performed at NASA John F. Kennedy Space Center (KSC) over the last 15 years. The LST is located at the Launch Equipment Test Facility (LETF) in the KSC industrial complex. The LETF is operated by Sierra Lobo, Inc., as a member of University-Affiliated Technology Development Contract (USTDC) to KSC Spaceport and Engineering and Technology Directorate (YA), with ASRC Aerospace Corporation as a the prime contractor. Trajectory Simulation Mechanism (TSM) is a major component of the LST, developed specifically to simulate nonstationary acoustic loads on launch pad structures, vehicles, and payloads. TSM enhances the capabilities within LST for simulating launch environments of future vehicles. The scaled launch environments will be used to predict the full-scale launch environment via an appropriate scaling procedure. Air Force Research Laboratory (AFRL) has tasked NASA KSC to perform a basic technology test program in support of developing a low-cost clean pad (incorporating passive mitigation techniques) for future launch vehicles. The overall goal of the program is to develop innovative launch exhaust management systems, which effectively reduce launch acoustic environment with innovative duct designs, while eliminating traditional sound suppression water systems. Passive techniques, such as nontraditional duct geometries, resonators, and diffusers, etc., will be investigated. The overall goals are to advance innovative concepts for a clean pad while developing ideas to reduce transmitted sound via investigation and modeling of jet exhaust acoustic and flow field characteristics. The series of tests outlined in this report represent baseline tests and are geared towards defining the acoustic load environment on the TSM pad for open and closed duct configurations. This report summarizes the cold jet acoustic testing for Mach 2.5 supersonic nitrogen jet issuing from a nozzle with 1-inch exit diameter. Acoustic data, including spectral sound power and Overall Sound Pressure Level (OASPL), are obtained both for a free jet and with the jet flowing through a rigid-walled duct with a J-deflector. The relative performance of closed duct and open duct is evaluated. The results show that the closed duct is superior to the partially open duct, and results in about 3-decibel (dB) noise reduction (near the duct axis) relative to the free jet. The location of the nozzle exit plane (NEP) relative to the duct inlet plane (DIP) has a significant effect on the acoustic field. The results suggest that the location of NEP at 10 inches above the DIP results in reduced acoustic loads relative to 5 inches above the duct inlet and 1 inch into the duct inlet.

Kandula, Max↗

DOE OSTI2022

Characteristics and mathematical modeling of apple slice drying in an electrohydrodynamic system with a needle‐plate electrode

Abstract The drying of apple slices in an electrohydrodynamic (EHD) system with a needle‐plate electrode was characterized and mathematically modeled at voltages of 30, 40, and 50 kV and with distances between needles of 5, 6, and 7 cm. The results showed that the drying rate, effective water diffusion coefficient, and rehydration ratio of the apple slices, and specific energy consumption of drying, all increased with increasing voltage. Initially, there was a period when the drying rate was approximately constant in the low‐voltage EHD, but not in the high voltage conditions. At the same voltage, the drying rate was highest when the distance between needles was 6 cm. The voltage and distance between needles had a significant ( p < .05) interactive effect on the effective water diffusion coefficient and specific energy consumption, but not on the rehydration ratio. General mathematical models for drying can be used to represent the drying behavior of apple slices. The Midilli and Kucuk model and the Logarithmic model had the best fits, with correlation coefficients of 0.998803 and 0.998267, respectively. Predictive functions for the moisture ratio of apple slices based on voltage and distance between needles were established and verified. The results indicated that the Logarithmic model could more accurately predict the moisture ratio of apple slices dried using the EHD method. Practical Applications As a new drying technology, electrohydrodynamic (EHD) drying has unequaled advantages. According to the results, using the appropriate voltage and distance between needles improves not only drying efficiency, but also the rehydration ratio of apple slices, which reflects the quality of dried products. The Logarithmic model can accurately predict the EHD drying behavior of apple slices, which is of great significance in optimizing actual production.

Li, Bowen↗