An Experiment on a Condensing Device for a Two-Phase Flow Loop System

<div class="htmlview paragraph">The increasing need for higher electrical power levels for military and scientific space purposes has spurred development of energy conversion systems with higher efficiencies than the traditional solar array. Numerous nuclear options are currently under development. These fuels eliminate the need for large deployable solar arrays or concentrators, allow unrestricted pointing and maneuvering, and are inherently less susceptible to natural and threat environments; they are the only viable energy source for outer planetary exploration. Fission reactors are the most desirable nuclear source for electric power levels above 10 kW. Radioisotope sources have been used in conjunction with thermoelectrics up to 1 kWe for planetary exploration. However, for radioisotope systems in the 1 to 10 kWe range, a much higher conversion efficiency is required. For over 15 years, NASA and the Department of Energy (DOE) have been developing closed cycle turbo-alternator (dynamic) power conversion systems for space use. The Air Force and DOE are jointly developing such a system under the Dynamic Isotope Power System (DIPS) program.</div> <div class="htmlview paragraph">Two closed dynamic cycles are being evaluated for use as part of the DIPS system. They are the Closed Brayton Cycle (CBC) which uses an inert (single phase) gas as the working fluid. The other system is the Organic Rankine Cycle (ORC) which utilizes the phase change properties of the working fluid. Each has a significantly different effect on the design of a radiative heat rejection system, primarily because of the temperature variation of the CBC single phase heat rejection versus the nearly constant temperature two-phase (condensing) ORC heat rejection. The heat rejection system plays an important role, since the power conversion efficiency is strongly dependent on the heat rejection temperature. The lower the rejection temperature, the higher the efficiency. However, the radiator area requirement increases as the rejection temperature is reduced. On a weight optimization basis both systems are comparable, however, the ORC system requires more radiator area for the same cycle efficiency. With the design requirement that the radiator be mounted around the circumference of the vehicle, available area is limited. Therefore, the heat rejection system design may not be a clear-cut weight optimization but rather a matter of area reduction at minimum penalty to efficiency and weight.</div> <div class="htmlview paragraph">The paper presents the results of an optimization study performed on the heat rejection system for a space based ORC power system using an isotope heat source. The radiator sizing depends on the heat rejection temperature, radiator configuration, and radiator properties such as the fin effectiveness, emissivity, and absorptivity. The optimization analysis to evaluate the effect of each of these parameters on the system weight and area is presented.</div>

<div class="htmlview paragraph">The Orbiting Carbon Observatory (OCO) instrument is scheduled for launch onboard an Orbital Sciences Corporation LEOStar-2 architecture spacecraft in December 2008. The instrument will collect data to identify CO<sub>2</sub> sources and sinks and quantify their seasonal variability. OCO observations will permit the collection of spatially resolved, high resolution spectroscopic observations of CO<sub>2</sub> and O<sub>2</sub> absorption in reflected sunlight over both continents and oceans. OCO has three bore-sighted, high resolution, grating spectrometers which share a common telescope with similar optics and electronics. A 0.765 μm channel will be used for O<sub>2</sub> observations, while the weak and strong CO<sub>2</sub> bands will be observed with 1.61 μm and 2.06 μm channels, respectively. The OCO spacecraft circular polar orbit will be sun-synchronous with an inclination of 98.2 degrees, mean altitude of 705 km and 98.9 minute orbit period. The OCO mission forms part of NASA's A-Train and leads the afternoon constellation ahead of the Aqua spacecraft.</div> <div class="htmlview paragraph">The instrument thermal design provides two cryogenic temperature zones for the detectors at 120 K and 180 K, one near room temperature zone for the spectrometers at 268 K and one for the electronics and cryocooler at 290 K. It contains three focal plane arrays (FPAs) in three separate housings, two of which are cooled to 120 K, and one to 180 K by a single Northrop Grumman Space Technology (NGST) pulse tube cryocooler. The cryocooler with a coldtip at 110 K, provides refrigeration to all three detectors via a high conductance flexible thermal strap. A variable conductance heat pipe (VCHP) based heat rejection system (HRS), with space viewing radiators, provides cooling for the electronics, cryocooler and maintains the spectrometer at -5°C. The VCHPs, with closed-loop temperature control, transport waste heat from the instrument located inside the spacecraft to the outboard radiators and provide tight temperature control. In survival mode, the instrument is off and the VCHPs are shutdown to minimize survival heater power.</div> <div class="htmlview paragraph">The instrument was fully integrated in December 2007 and has undergone EMI/EMC, vibration, and two thermal vacuum (TV) tests. This paper reports on the results from the TV and thermal balance (TB) tests with an emphasis on the VCHP-based HRS and the cryogenic subsystem (CSS). A brief overview of the thermal control design is presented as well as key test results from the instrument-level thermal vacuum/balance test.</div>

<div class="htmlview paragraph">Since 1974, the University of Southern California’s Catalina Marine Science Center (CMSC) Hyperbaric Chamber Facility has treated 302 cases of decompression sickness and cerebral air embolism. The U.S. Navy hyperbaric oxygen treatment tables are almost universally accepted and used, and are highly successful. The method consists of administering 100% O2 by mask intermittently in a hyperbaric chamber at pressures of 2.73 and 1.82 ATA, and 50% N2/50% 02 at 6.00 ATA.</div> <div class="htmlview paragraph">This paper briefly reviews: 1) the pathophysiology of air embolism and decompression sickness, 2) the basic rationale and goals of hyperbaric oxygen therapy and 3) the specific treatment tables used at CMSC. The experience of 12 years of decompression accident management is discussed with emphasis on treatment table modification, treatment results and problem areas.</div> <div class="htmlview paragraph">Finally, the potential application of hyperbaric oxygen therapy for EVA decompression accidents in the future Space Station is discussed.</div>

<div class="htmlview paragraph">The Spacelab Life Sciences missions are intended to support Life Sciences experiments. The Spacelab Life Sciences 1 (SLS-1) mission originated with a call to the scientific community for experiments in 1978. Accepted experiments involved humans, primates, rodents, amphibians, and plants. The original payload configuration has been reduced to include human, passive rodent, and basic biology experiments and engineering evaluations.</div> <div class="htmlview paragraph">Human experiments will address effects of micro-gravity on various physiological parameters during and postflight. Investigations with nonhuman subjects will study microgravity effects on the cardiopulmonary, cardiovascular, and musculoskeletal systems, on the regulation of blood volume and erythropoiesis, and on calcium metabolism and gravity receptors.</div> <div class="htmlview paragraph">SLS-1 will serve as a stepping stone in establishing capabilities for flying nonhuman subjects and performing in-flight manipulations on these subjects without jeopardizing the crew environment. Fundamental technology incorporated in the animal holding facilities and laboratory work bench will be used in subsequent missions and in the future Space Station.</div>

<div class="htmlview paragraph">The aim of this paper is to present the Hermes Thermal Control Concept which constitutes the reference baseline for the phase 2 of the Hermes program.</div> <div class="htmlview paragraph">The technical solutions based on active and passive means, are dictated by a variety of requirements including temperature and heat flux limits, mass & power minimization, availability of space for accommodation of TCS devices.</div> <div class="htmlview paragraph">Furthermore thecomplex mission profile (including atmospheric flight and several modes of operation o002d;orbit) and the configuration of the space-vehicle, require the adoption of a particularly flexible thermal control.</div> <div class="htmlview paragraph">The <b>ATCS (Active Thermal Control Section)</b> is based on a dual loop concept, using both water and Freon R114 cooling loops for heat collection from the various sources, heat transportation and heat rejection through dedicated devices.</div> <div class="htmlview paragraph">The main heat sources to be considered are those extracted from the cabin air loop, the electronics, the power generation items (fuel cells and lithium batteries) and the environmental loads during ascent and re-entry.</div> <div class="htmlview paragraph">The major heat rejection devices are the Ground Support Equipment Heat Exchangers (on ground, before launch and after landing), the Ammonia Boilers during ascent or re-entry (low altitude), the Hermes Radiators on orbit, the Water Evaporators during ascent and re-entry (high altitudes) and to complement the radiator rejection capability.</div> <div class="htmlview paragraph">The <b>PTCS (Passive Thermal Control Section)</b> relies on different concepts of insulations together with a system of temperature sensors and heaters, to control the thermal excursions of the space-plane components and structural parts, within the specified limits.</div> <div class="htmlview paragraph">Thermal insulation blankets (foams, thermal control coatings, multi layer insulations) involve an extensive material research and testing activity, since they are subjected to quite different conditions: vacuum, atmospheric, internal, external and very different level of temperatures depending on the location.</div> <div class="htmlview paragraph">The present design of the Thermal Control Subsystem is oriented to the minimization of mass and power budgets and to respect the quantitative and qualitative safety and reliability requirements.</div>

<div class="htmlview paragraph"> </div> <div class="htmlview paragraph"> </div> <div class="htmlview paragraph">A computer simulation of a high performance two-stroke engine has been validated by a transient test method. The simulation included unsteady gas dynamics, together with detailed mechanical models for the reed valve, etc. The combustion model used Vibe coefficients derived directly from measured cylinder pressures. Cylinder scavenging characteristics which were measured on The Queen's University of Belfast (QUB) single-cycle rig were also incorporated in the simulation.</div> <div class="htmlview paragraph"> </div> <div class="htmlview paragraph">Validation of the model involved use of an inertial dynamometer and data acquisition system which has been developed at QUB. This dynamometer incorporates a flywheel which is directly coupled to the engine. During a test, the engine is accelerated, and the torque and power are calculated from the flywheel speed characteristics. Further, at pre-determined engine speed intervals, the cylinder and exhaust pressures may be recorded. This testing system provided a convenient and rapid experimental method to acquire data.</div> <div class="htmlview paragraph"> </div> <div class="htmlview paragraph">Measurement of power, pressures and temperatures during transient testing are discussed. Also presented are methods which reduce the errors arising from the slow response of thermocouples. The measured results are compared with the computer predictions for power and exhaust pressure. Excellent correlation was achieved.</div> <div class="htmlview paragraph"> </div>

<div class="section abstract"><div class="htmlview paragraph">The design and testing of innovative components and control logics for future vehicular platform represents a challenging task in the automotive field. The use of scale model vehicles constitutes an interesting alternative for testing assessment by decreasing time and cost efforts with a potential benefit in terms of safety.</div><div class="htmlview paragraph">The target of this research work is the development of a customized scale vehicle platform for verifying and validating innovative control strategies in safe conditions and with cost reduction. Consequently, the electrification of a radio-controlled 1:5 scale vehicle is carried out and a customized remote real-time controller is installed onboard. One of the main features of this commercial product is its modular characteristics that allows the modification of some component properties, such as the viscous coefficient of the shock absorbers, the stiffness of the springs and the suspension geometry. The original vehicle is equipped with a 2-stroke internal combustion engine, whose throttle command is provided by a common radio transceiver/receiver unit. The original configuration is commonly adopted for radio-controlled race car competitions, but the presence of a noisy combustion engine is not well suited for implementing a precise and accurate control logic based on onboard sensor measurements; hence, the conversion into an electric vehicle represents the adopted solution in this research activity.</div><div class="htmlview paragraph">In particular, the electrification process accounts for the replacement of the internal combustion engine and fuel tank with a brushless DC motor, a battery pack, and a planetary gearbox. CAD tools are exploited for the selection of the replacement components and the design of the mounting systems. Additionally, a Speedgoat Baseline Real-Time Target Machine is installed for implementing the customized control logic, developed in MATLAB/Simulink environment, for controlling the traction electric motor and the steering servomotor.</div><div class="htmlview paragraph">After a preliminary bench testing phase, a remote control is implemented for the validation of the system through maneuvers typically carried out for vehicle handling analysis.</div></div>

<div class="htmlview paragraph">In June 1975, the Forest Service Equipment Development Center at San Dimas, Calif., conducted tests to determine exhaust system temperatures on late-model vehicles. For normal operation, test results showed only small temperature differences at any point on a vehicle's exhaust system between those equipped with catalytic converters and those without catalytic converters. Also, test results indicate that the direct forest fire hazard from catalytic converter-equipped vehicles is essentially the same as with other exhaust systems, except when the vehicle engine malfunctions.</div> <div class="htmlview paragraph">NOTE: The term “vehicle,” as used in this report, refers to motor vehicles generally. “Automobile” or “car” implies a sedan, sedan delivery, or station wagon. A “pickup” is a pickup truck of less than 6,000 lb (2,721.6 kg) GVW.</div>

<div class="htmlview paragraph">Evaluations were made of the short-term (5 minute) durability at high temperatures of 85 mm outer diameter ceramic radial turbine rotors made of silicon nitride using an improved hot gas spin test rig.</div> <div class="htmlview paragraph">Under no load conditions, the rotors withstood a maximum turbine tip speed (Ut) of 550 m/s without bursting at a turbine inlet gas temperature (TIT) of 1240°C.</div> <div class="htmlview paragraph">Under partially loaded conditions, they withstood up to Ut of 500 m/s at TIT of 1280°C without bursting.</div> <div class="htmlview paragraph">The test results indicated that the knee point temperature in terms of TIT at which the failure tip speed decreased sharply was about 40°C higher under partially loaded condition than under no load condition.</div> <div class="htmlview paragraph">The temperature and stress distribution in the turbine in the hot gas spin test were calculated by the finite element analysis, which supported the dependence of the knee point temperature in terms of TIT at spin test on load condition.</div>

<div class="section abstract"><div class="htmlview paragraph">The use of CNG in modern spark ignition turbocharged engine offers many advantages such as high knocking resistance, low CO₂ emissions and high specific power outputs. On the other hand, compared to gasoline, the volumetric efficiency is significantly decreased when CNG is port-injected due to its low energy density. In order to address this issue, recent studies have successfully highlighted the advantages on port-injection engines of the CIGAL™ concept (Concomitant Injection of Gas And Liquid fuels) from IFP Energies Nouvelles.</div><div class="htmlview paragraph">However, the combination of port-injection of CNG with direct injection of gasoline remains unexplored. This paper investigates this novel injection concept on the four-cylinder 1.6L turbocharged GDI engine with inlet variable valve timing resulting from the cooperation between PSA Peugeot-Citroen and the BMW Group. This engine was fitted with an independent CNG port-injection system and a specific engine management system was implemented in order to allow concomitant injection operation.</div><div class="htmlview paragraph">The first part of the study investigates the potential of concomitant injection compared to gasoline and methane operation. On the stock configuration, 29 bar BMEP (370 N.m) were reached at 2500 rpm with 30% gasoline and 70% methane in stoichiometric conditions. Also, significant reductions of fuel consumption and HC emissions were observed. Full load tests carried out with a smaller turbocharger enhanced the synergy effect between the two fuels at lower speeds.</div><div class="htmlview paragraph">The second part of this work focuses on the reliability of the gasoline direct injectors during CNG operation. Temperature measurements on the gasoline injector nozzles were carried out in gasoline, CNG and concomitant injection modes. Finally, the results of gasoline direct injectors durability tests under CNG and gasoline operation are discussed.</div></div>

<div class="htmlview paragraph">Selection of working fluid is one of the main criterions for designing of heat pipes thermal control systems (TCS) for space application. In this paper we will describe how we solved the task of development of the TCS with working fluid of high thermal physical properties.</div> <div class="htmlview paragraph">In 2004-2006 we developed the Engineering model of Deployable Radiator based on Loop Heat Pipe by CAST purchase order. It was developed for qualification tests.</div> <div class="htmlview paragraph">Ammonia application as LHP working fluid is stipulated by its high thermal physical properties. However Ammonia freezing temperature is of minus 77ºC. Such fact impedes Ammonia application when operation temperatures of LHP Radiator are lower than this value, for example, It takes several tens of hours to orbit a spacecraft and prepare it for work (at that moment the spacecraft is out of power supply) and the working fluid can be frozen in a condenser-radiator when the spacecraft being in the shadow over a long period of time. While working fluid de-freezing in the radiator the condenser tube can be destroyed. To avoid this problem it is better to use the working fluid with lower freezing point. However use of lower freezing point fluids will cause decreasing of thermal control system parameters, in particular, maximum heat transfer power and increasing of LHP thermal resistance, mass, overall dimensions as well as the spacecraft mass.</div> <div class="htmlview paragraph">An important task that shall be solved during ammonia LHP application is recovery of LHP operation ability after working fluid freezing in radiator-condenser. To recover working fluid circulation in LHP it is necessary to defreeze the whole LHP. During multiple freezing/melting cycles of LHP working fluid LHP depressurization may occur. This paper is dedicated to solving aspects of Radiator operation ability recovery after its freezing. Aspects of passive temperature control of LHP evaporator using pressure regulator and aspects of LHP active temperature control using heaters and Peltier elements mounted to compensation chamber are also considered in this paper.</div> <div class="htmlview paragraph">Development of new key components made it possible to design Deployable Radiator with specific mass of less than 10 kg/kW. The Deployable Radiator parameters are described in the paper.</div>

<div class="section abstract"><div class="htmlview paragraph">This report proposes a rheological model and a thermal analysis model for oil films, which transmit power through a variator, as a prediction method for the maximum traction coefficient, and then describes the application and verification of this method.</div><div class="htmlview paragraph">The rheological model expresses the conditions inside the contact ellipse using a combination of viscosity and plasticity.</div><div class="htmlview paragraph">The thermal analysis model for oil films was confirmed by comparison of previously obtained temperatures directly measured from the traction contact area of the four-roller experimental apparatus [<span class="xref">1</span>]. The measurement used a thin-film temperature sensor and the consistency between the calculated and measured values was verified in the estimation model by reflecting the precise thermal properties of the thin film. Most values were consistent with the calculated values for the middle plane local shear heating model inside the oil film. However, under some conditions, the values were closer to those calculated for homogeneous shear. Based on these results, this paper proposes a calculation method that combines both heating models within the contact ellipse.</div><div class="htmlview paragraph">In addition, the variator in a continuously variable transmission (CVT) was verified for the first time by using a test box to take direct temperature measurements from the transmission contact area in the CVT. This test verified the precision of the thermal analysis model, including the spin motion.</div><div class="htmlview paragraph">Finally, the maximum traction coefficient was estimated using these calculation models and compared with measured values.</div></div>

<div class="section abstract"><div class="htmlview paragraph">With an objective of improving the range as well as other safety and comfort aspects, thermal management becomes increasingly important in the development of electrified vehicles both at the component as well as system level. The considerable increase in complexity of the thermal management system and its tighter interactions with the complete vehicle is driving an increasing trend towards system simulation compared to expensive testing.</div><div class="htmlview paragraph">At the system level, different sub-systems interact with each other at varying extents. An example of one such strong interaction is between the coolant and AC circuits using battery chillers. Thermal management system simulation models must be capable of simulating such interactive systems.</div><div class="htmlview paragraph">At the component level, ensuring the efficacy of the several components used in these intricately linked systems becomes increasingly important. An accurate prediction of temperature distribution inside the battery pack is essential to avoid damaging situations such as thermal runaway. An integrated approach of 1D-flow inside the cooling plates combined with 3D-thermal analysis of battery cells and cooling plates in GT-SUITE is described in this study.</div><div class="htmlview paragraph">Also, a new predictive electrochemical and thermal battery models to analyze and optimize both component and system level behavior is described. This allows selection of cell chemistry and design in addition to providing heat rejection values for design of the cooling system. Aging predictions at both the cycle and calendar time scales are described that consider effects of varying environmental and operating conditions.</div><div class="htmlview paragraph">After the e-powertrain, the HVAC compressor is the largest consumer of electrical energy. For optimizing compressor power consumption without compromising on human thermal comfort attention is focused on localized cooling inside the cabin. This paper outlines an integrated co-simulation approach, that allows an investigation of the trade-off between passenger comfort and driving range, or to develop smart controls of the HVAC system.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The aim of this work is to investigate the possibility of heat insulation by “Temperature Swing”, that is temperature fluctuation, on combustion chamber walls coated with low-heat-conductivity and low-heat-capacity materials.</div><div class="htmlview paragraph">Adiabatic engines studied in the 1980s, such as ceramic coated engines, caused constantly high temperature on combustion wall surface during the whole cycle including the intake stroke, even if it employed ceramic thermal barrier coating methods. This resulted in increase in NOx and Soot, decrease in volumetric efficiency and combustion efficiency, and facilitated the occurrence of engine knock.</div><div class="htmlview paragraph">On the other hand, “Temperature Swing” coat on the combustion chamber walls leads to a large change in surface temperature. In this case, the surface temperature with this insulation coat follows the transient gas temperature, which decreases heat loss with the prevention of intake air heating, and also which is expected to prevent NOx and Soot from increasing. In our calculations, the increase of the surface temperature fluctuation, “Temperature Swing” results from the coat of lower heat conductivity and lower heat capacity. Particularly in Gasoline engines, the coat with the appropriate thickness can reduce the heat flux from the wall to the working gas during intake stroke and can avoid engine knock.</div><div class="htmlview paragraph">Based on our calculations, it is clarified that both the prevention of intake air heating and the low heat rejection were successfully possible with the material of appropriate thermo-physical properties.</div><div class="htmlview paragraph">In addition to the calculations, a preliminary test-piece experiment was executed. It was demonstrated that the surface temperature of a porous coat, that is a candidate of “Temperature Swing” coat, immediately follows the transient gas temperature, and also the proposed insulation coat can exactly reduce the heat flux in the single-cylinder engine.</div></div>

<div class="section abstract"><div class="htmlview paragraph">An Automotive vehicle is subjected to run in various ambient conditions at different load conditions. For an SUV with off-roading capability, it becomes more important to size the cooling module for optimal performance.</div><div class="htmlview paragraph">The heat exchangers like AC condenser and radiator dimensions majorly defines the heat rejection capacity suitable for the respective powertrain configuration of a vehicle. Subsequently, the air flown over the heat exchangers will be dependent on the radiator fan capacity along with the vehicle speed.</div><div class="htmlview paragraph">However, being an SUV with off-roading capability, the need arises to simulate the combination of various speed ranges, in addition to the different loading conditions involved. Considering the various conditions, the ram air required for efficient cooling should be adequate for the heat exchangers to attain optimal performance. Hence, radiator & fan motor sizing plays an important role in the Powertrain as well as Cabin cooling performance.</div><div class="htmlview paragraph">The present study was conducted to check the adequacy of the radiator & fan motor sizing, and their effects to improve the powertrain and cabin cooling performance of the vehicle.</div><div class="htmlview paragraph">Also, this paper covers the experiments conducted and their respective findings on optimization of cooling performance and methodology for same.</div></div>