Advanced Solar-propelled Cargo Spacecraft for Mars Missions

Three concepts for an unmanned, solar powered, cargo spacecraft for Mars support missions were investigated. These spacecraft are designed to carry a 50,000 kg payload from a low Earth orbit to a low Mars orbit. Each design uses a distinctly different propulsion system: A Solar Radiation Absorption (SRA) system, a Solar-Pumped Laser (SPL) system and a solar powered magnetoplasmadynamic (MPD) arc system. The SRA directly converts solar energy to thermal energy in the propellant through a novel process. In the SPL system, a pair of solar-pumped, multi-megawatt, CO2 lasers in sunsynchronous Earth orbit converts solar energy to laser energy. The MPD system used indium phosphide solar cells to convert sunlight to electricity, which powers the propulsion system. Various orbital transfer options are examined for these concepts. In the SRA system, the mother ship transfers the payload into a very high Earth orbit and a small auxiliary propulsion system boosts the payload into a Hohmann transfer to Mars. The SPL spacecraft and the SPL powered spacecraft return to Earth for subsequent missions. The MPD propelled spacecraft, however, remains at Mars as an orbiting space station. A patched conic approximation was used to determine a heliocentric interplanetary transfer orbit for the MPD propelled spacecraft. All three solar-powered spacecraft use an aerobrake procedure to place the payload into a low Mars parking orbit. The payload delivery times range from 160 days to 873 days (2.39 years)

Liquid meniscus friction on a wet plate: Bubbles, lamellae and foams

Many microfluidics devices, coating processes or diphasic flows involve the motion of a liquid meniscus on a wet wall. This motion induces a specific viscous force, that exhibits a non-linear dependency in the meniscus velocity. We propose a review of the theoretical and experimental work made on this viscous force, for simple interfacial properties. The interface is indeed assumed either perfectly compressible (mobile interface) or perfectly incompressible (rigid interface). We show that, in the second case, the viscous force exerted by the wall on the meniscus is a combination of two power laws, scaling like $Ca^{1/3}$ and $Ca^{2/3}$, with $Ca$ the capillary number. We provide a prediction for the stress exerted on a foam sliding on a wet solid and compare it with experimental data, for the incompressible case

The motion of a deforming capsule through a corner

A three-dimensional deformable capsule convected through a square duct with a corner is studied via numerical simulations. We develop an accelerated boundary integral implementation adapted to general geometries and boundary conditions. A global spectral method is adopted to resolve the dynamics of the capsule membrane developing elastic tension according to the neo-Hookean constitutive law and bending moments in an inertialess flow. The simulations show that the trajectory of the capsule closely follows the underlying streamlines independently of the capillary number. The membrane deformability, on the other hand, significantly influences the relative area variations, the advection velocity and the principal tensions observed during the capsule motion. The evolution of the capsule velocity displays a loss of the time-reversal symmetry of Stokes flow due to the elasticity of the membrane. The velocity decreases while the capsule is approaching the corner as the background flow does, reaches a minimum at the corner and displays an overshoot past the corner due to the streamwise elongation induced by the flow acceleration in the downstream branch. This velocity overshoot increases with confinement while the maxima of the major principal tension increase linearly with the inverse of the duct width. Finally, the deformation and tension of the capsule are shown to decrease in a curved corner

Conceptual Design of an In-Space Cryogenic Fluid Management Facility

The conceptual design of a Spacelab experiment to develop the technology associated with low gravity propellant management is presented. The proposed facility consisting of a supply tank, receiver tank, pressurization system, instrumentation, and supporting hardware, is described. The experimental objectives, the receiver tank to be modeled, and constraints imposed on the design by the space shuttle, Spacelab, and scaling requirements, are described. The conceptual design, including the general configurations, flow schematics, insulation systems, instrumentation requirements, and internal tank configurations for the supply tank and the receiver tank, is described. Thermal, structural, fluid, and safety and reliability aspects of the facility are analyzed. The facility development plan, including schedule and cost estimates for the facility, is presented. A program work breakdown structure and master program schedule for a seven year program are included

Numerical and Experimental Analysis of Air-Cooled Condensers

The scope of this project is to numerically and experimentally dry cooling process in air-cooled condensers (ACCs) designed for concentrated solar power (CSP) applications. This effort is driven by the growing economic and political pressure to reduce water consumption during power generation due to limited water resources in the arid geographic climate of the southwestern United States. A computational approach is used in conjunction with experimental validation to gain a more complete understanding of these systems. Traditionally research into ACCs have been largely limited to air-side heat transfer modelling as it accounts for a large portion of the total thermal resistance. Recent studies, however, indicate that impact of steam-side thermal resistances is often more significant than previously reported. Additionally, as the thermal performance of the air-side heat transfer is improved, the heat and mass transfer characteristics of the steam-side must be considered in greater detail. To improve the mathematical model of the steam-side phenomena, the impact of both rotation and divergence of the nonconservative Nusselt velocity vector field on film growth and mass conservation are investigated and a new film thickness equation is introduced. Nusselt thin film assumptions are implemented to derive the governing differential equations for mass, and energy and momentum. A transformation for effective peripheral angle during stratification is derived based on the assumed linear interface between liquid and vapor of Chato at the lower part of the tube. An expression for entrance length, L_e^* is introduced as a function of inclination angle. The results for heat transfer ratio have been compared with experimental data and an empirical correlation from literature and a good agreement was obtained and shown between them. An analysis of filmwise condensation of a pure vapor in inclined non-circular tubes using cubic Bezier curves is presented. Nusselt thin film theory is modified to derive the governing differential equations for momentum, mass, and energy for a generalized surface contour. Elliptical and ovoid tube profiles are investigated and the film thickness and Nusselt number are compared to that of a circular tube on the basis of equivalent surface area. It was found that for a given surface area, the pressure drop in a circular tube is the lowest, however, entropy generation due to heat transfer can reduced by increasing |Y_2 |/X_2. Ovoid tubes can achieve superior heat transfer performance over elliptical tubes on the basis of equivalent aspect ratio, |Y2|/X2 however, this enhancement diminishes with increased inclination angle. The pareto dominant solutions are correlated to inclination angle and heat transfer enhancement and a new relation is proposed. To relax the standard isothermal condition applied to the wall, the air-side heat transfer coefficient is coupled with the film thickness equation to investigate the impact on the condensate film growth and the HTC of the condenser. The air-side fluid flow is modeled using ANSYS Fluent and the Nusselt thin film theory was used to describe the film thickness in the upper part of the tube interior and a pool condensation model is used to define the axial flow in the lower part. The analysis was successful in showing that air-side transport phenomena can have a measurable impact on the condensate film distribution. Finally, A full-sized ACC test apparatus was constructed to investigate dry cooling performance and potential modifications. 608 data points were experimentally obtained over a wide range of ambient temperature and compared with 8 commonly used correlations from the available literatures. The ambient temperature changes from 3° to 45°C, the steam mass flux varies from 3 to 18 kg/(m2·s), vapor quality ranges from 0.51 to 0.86. An improved two-phase frictional pressure drop correlation based on the Wallis correlation is proposed. The new correlation agrees well with the experimental database and outperforms all other tested correlations with a MAPE of 16.84% and a NRMSE of 20.45% while being able to predict 91.41% of the experimental data within 30%

Performance analysis of heat transfer processes from wet and dry surfaces : cooling towers and heat exchangers

The objective of this work is to study the thermal and hydraulic performance of evaporatively cooled heat exchangers, including closed wet cooling towers, and dry tube heat exchangers with various geometries. Applications utilising such equipment exist in almost every thermal process. The investigation includes theoretical analysis, computational approaches, and experimental measurements. In this work, a computational model is presented for the thermal performance of closed wet cooling towers intended for use in conjunction with chilled ceilings in cooling of buildings. A variable spray water temperature inside the tower is assumed. A prototype tower was subjected to experimental measurements to find its characteristics. Optimisation of the tower geometry and flow rates for specified design conditions is carried out in order to achieve a high value of the coefficient of performance (COP). Results from a global simulation program (including the tower model, a transient building model, a chilled ceiling model, system control etc.) show that closed wet cooling towers can be used with chilled ceilings to achieve acceptable indoor air temperatures in locations having suitable climatic conditions. This is supported by published results from a performance test of an office building using this method of cooling. Simplification of the model is obtained by assuming a constant temperature for the spray water. The tower performance predicted by the simplified model and the computational model shows comparable results. The results of the simplified model are then incorporated with Computational Fluid Dynamics (CFD) to assess the temperature distribution inside the tower. It is shown that CFD can be implemented to study the effect of air distribution inside the tower on its performance. The effect of introducing plate fins in evaporatively cooled plain circular tubes is experimentally studied. The measurement results show a 92% to 140% increase in the amount of heat transfer for the finned tubes. This is accompanied by an increase in the pressure drop, so that an indication of the combined thermal hydraulic performance is found to be close for the two geometries. However, it shows higher heat transfer rates per volume for the finned tubes. The performance of oval tubes in the evaporatively cooled heat exchanger is then experimentally investigated. The measurement results for the oval tubes show good heat and mass transfer characteristics; its average mass transfer Colburn factor is 89% of that for the circular tubes. Furthermore, it shows low friction factor for the air flow, which is 46% of that for the circular tubes. It is concluded that the tested oval tube is better than the circular tubes in combined thermal hydraulic performance. The features of oval tubes appear clearer in a dry heat transfer process. Five shapes of dry oval tubes are experimentally investigated in a cross-flow of air. The measurement results for the oval tubes are compared with those for an equivalent circular tube. It is found that the Nusselt numbers NuD for the studied tubes are close for Reynolds numbers ReD < 4000. While for higher ReD, the NuD decreases with the increase of the oval tube axis ratio. The drag measurements indicate lower drag coefficients Cd avg for the oval tubes. It is revealed that the investigated oval tubes have favourable combined thermal-hydraulic performance, which is expressed in terms of (NuD / Cd avg). The ratio of (NuD / Cd avg) for the oval tubes to that for the circular tube is from 1.3 to 2.5.reviewe

A facility to Search for Hidden Particles (SHiP) at the CERN SPS

A new general purpose fixed target facility is proposed at the CERN SPS accelerator which is aimed at exploring the domain of hidden particles and make measurements with tau neutrinos. Hidden particles are predicted by a large number of models beyond the Standard Model. The high intensity of the SPS 400~GeV beam allows probing a wide variety of models containing light long-lived exotic particles with masses below ${\cal O}$(10)~GeV/c$^2$, including very weakly interacting low-energy SUSY states. The experimental programme of the proposed facility is capable of being extended in the future, e.g. to include direct searches for Dark Matter and Lepton Flavour Violation.Comment: Technical Proposa

Gas-Liquid Stratified Flow in Pipeline with Phase Change

When the natural gas with vapor is flowing in production pipeline, condensation occurs and leads to serious problems such as condensed liquid accumulation, pressure and flow rate fluctuations, and pipeline blockage. This chapter aims at studying phase change of vapor and liquid-level change during the condensing process of water-bearing natural gas characterized by coupled hydrothermal transition and phase change process. A hydrothermal mass transfer coupling model is established. The bipolar coordinate system is utilized to obtain a rectangular calculation domain. An adaptive meshing method is developed to automatically refine the grid near the gas-liquid interface. During phase change process, the temperature drop along the pipe leads to the reduction of gas mass flow rate and the rise of liquid level, which results in further pressure drop. Latent heat is released during the vapor condensing process which slows down the temperature drop. Larger temperature drop results in bigger liquid holdup while larger pressure drop causes smaller liquid holdup. The value of velocity with phase change is smaller than that without phase change while the temperature with phase change is bigger. The highest temperature locates in gas phase. But near the pipe wall the temperature of liquid region is higher than gas region

Condensed Droplet Experiment for NASA in Sub-Orbital Spaceflight

Purdue’s Condensed Droplet Experiment for NASA in Sub-Orbital Spaceflight (ConDENSS) experiment was chosen by NASA’s Flight Opportunities Program for sub-orbital flight testing on a future Blue Origin New Shepard sub-orbital mission. ConDENSS seeks to test several predictions of existence and stability of static capillary droplets, plugs, and annular sleeves predicted by computational modeling. Application of the results includes advancing zero-gravity condenser technology and several possible applications on Earth. The payload is designed to form droplets, plugs, and sleeves of liquid by pumping pre-determined volumes of the liquid onto the walls of elliptical cone test sections. Four test sections with a static gas and four test sections with flowing gas are to be flown in one mission. The gas flow simulates conditions in the condenser Section of a phase-change heat transfer loop in spaceflight. Observations, collected by cameras throughout the payload, are to be compared with predictions from zero-gravity numerical modeling to validate or refute the zero-gravity fluids simulations This work is partially supported by NASA Grant NNX16AP69G from the Flight Opportunities Program in STMD

Solar pond powered liquid desiccant evaporative cooling

Liquid desiccant cooling systems (LDCS) are energy efficient means of providing cooling, especially when powered by low-grade thermal sources. In this paper, the underlying principles of operation of desiccant cooling systems are examined, and the main components (dehumidifier, evaporative cooler and regenerator) of the LDCS are reviewed. The evaporative cooler can take the form of direct, indirect or semi-indirect. Relative to the direct type, the indirect type is generally less effective. Nonetheless, a certain variant of the indirect type - namely dew-point evaporative cooler - is found to be the most effective amongst all. The dehumidifier and the regenerator can be of the same type of equipment: packed tower and falling film are popular choices, especially when fitted with an internal heat exchanger. The energy requirement of the regenerator can be supplied from solar thermal collectors, of which a solar pond is an interesting option especially when a large scale or storage capability is desired