Development, Validation, and Application of a Refrigerator Simulation Model

This report describes the further development and validation of the Refrigerator/Freezer Simulation (RFSIM) model. The reports also describes the first major application of the model as an analysis tool for new refrigerator designs; several aspects of multi-speed compressor operation were examined with the model. Several improvements were made to the model that facilitated the validation process and the examination of multi-speed compressors: the model was made more general so that it could operate in numerous configurations in addition to the original design and simulation modes; many improvements were made in the modeling logic and robustness of the capillary tube-suction line heat exchanger model; and the equation-of-statebased property routines that calculated the thermodynamic properties were replaced with interpolation routines that were much faster. The RFSIM model, in design and simulation mode, was validated with data from two refrigerators. In both modes, the average model errors were less than ??5% for several important variables such as evaporator capacity and coefficient of performance. The errors of the simulation mode were reduced from the previous model validation primarily by using a different void fraction correlation in the refrigerant charge equations. The results from the validated RFSIM model indicate that a two-speed compressor could yield energy savings of 4% to 14% due to the increased steady-state efficiency at the low speed and an additional 0.5 to 4% savings due to the decreased cycling frequency. The results also showed that the capillary tube-suction line heat exchanger, when designed for the low speed, did not adversely affect the pull-down capacity when the compressor operated at the high speed. Lastly, it was found that a refrigerator operating at low ambient temperatures could actually benefit from a decrease in the condenser fan speed. This change in fan speed increased the evaporator capacity by reallocating charge to the evaporator and subsequently reducing the superheat at the evaporator exit.Air Conditioning and Refrigeration Project 6

Evaluation and characterization of the methane-carbon dioxide decomposition reaction

A program was conducted to evaluate and characterize the carbon dioxide-methane (CO2-CH4) decomposition reaction, i.e., CO2 + CH4 = 2C + 2H2O. The primary objective was to determine the feasibility of applying this reaction at low temperatures as a technique for recovering the oxygen (O2) remaining in the CO2 which exits mixed with CH4 from a Sabatier CO2 reduction subsystem (as part of an air revitalization system of a manned spacecraft). A test unit was designed, fabricated, and assembled for characterizing the performance of various catalysts for the reaction and ultraviolet activation of the CH4 and CO2. The reactor included in the test unit was designed to have sufficient capacity to evaluate catalyst charges of up to 76 g (0.17 lb). The test stand contained the necessary instrumentation and controls to obtain the data required to characterize the performance of the catalysts and sensitizers tested: flow control and measurement, temperature control and measurement, product and inlet gas analysis, and pressure measurement. A product assurance program was performed implementing the concepts of quality control and safety into the program effort

A survey of gas-side fouling in industrial heat-transfer equipment

Gas-side fouling and corrosion problems occur in all of the energy intensive industries including the chemical, petroleum, primary metals, pulp and paper, glass, cement, foodstuffs, and textile industries. Topics of major interest include: (1) heat exchanger design procedures for gas-side fouling service; (2) gas-side fouling factors which are presently available; (3) startup and shutdown procedures used to minimize the effects of gas-side fouling; (4) gas-side fouling prevention, mitigation, and accommodation techniques; (5) economic impact of gas-side fouling on capital costs, maintenance costs, loss of production, and energy losses; and (6) miscellaneous considerations related to gas-side fouling. The present state-of-the-art for industrial gas-side fouling is summarized by a list of recommendations for further work in this area

Workshop on an Assessment of Gas-Side Fouling in Fossil Fuel Exhaust Environments

The state of the art of gas side fouling in fossil fuel exhaust environments was assessed. Heat recovery applications were emphasized. The deleterious effects of gas side fouling including increased energy consumption, increased material losses, and loss of production were identified

FAULT DETECTION AND CONTROLLING OF SHELL AND TUBE HEAT EXCHANGER USING ANN

Fault Detection and controlling is important in many industries to provide safe operation of a process. Heat Exchangers are generally used in process industries. Shell and Tube Heat Exchanger  is a common type of heat exchanger used in oil refineries, chemical processes .It is suited for higher-pressure applications. Actuator faults, sensor faults and process faults are the common faults occurring in chemical processes. To identify and remove these type of faults in the system fault detection and controlling techniques are proposed.  In this present work Sensor and Process faults of Shell and Tube Heat Exchanger is detected and controlled using Artificial Neural Network(ANN).NARX network (Nonlinear Auto regressive with External input) is used as ANN network structure. Network is trained using Levenberg Marquardt and Bayesian Regularization algorithms. The performance parameters such as Mean Square Error, Integral Absolute Error (IAE), Integral Time Absolute Error (ITAE) and Integral Square Error (ISE) are obtained for the above said methods which are shown in simulation results. Tabulated results shows the comparison between the three algorithms. Simulation results also shows the comparison between the controlled response obtained from ANN with and without PID Controller.Â

Alkaline static feed electrolyzer based oxygen generation system

In preparation for the future deployment of the Space Station, an R and D program was established to demonstrate integrated operation of an alkaline Water Electrolysis System and a fuel cell as an energy storage device. The program's scope was revised when the Space Station Control Board changed the energy storage baseline for the Space Station. The new scope was aimed at the development of an alkaline Static Feed Electrolyzer for use in an Environmental Control/Life Support System as an oxygen generation system. As a result, the program was divided into two phases. The phase 1 effort was directed at the development of the Static Feed Electrolyzer for application in a Regenerative Fuel Cell System. During this phase, the program emphasized incorporation of the Regenerative Fuel Cell System design requirements into the Static Feed Electrolyzer electrochemical module design and the mechanical components design. The mechanical components included a Pressure Control Assembly, a Water Supply Assembly and a Thermal Control Assembly. These designs were completed through manufacturing drawing during Phase 1. The Phase 2 effort was directed at advancing the Alkaline Static Feed Electrolyzer database for an oxygen generation system. This development was aimed at extending the Static Feed Electrolyzer database in areas which may be encountered from initial fabrication through transportation, storage, launch and eventual Space Station startup. During this Phase, the Program emphasized three major areas: materials evaluation, electrochemical module scaling and performance repeatability and Static Feed Electrolyzer operational definition and characterization

Condition monitoring for a neutral beam heating system

This thesis presents the design of a condition monitoring scheme for the neutral beam cryogenic pumping system deployed in the Joint European Torus. The performance of the scheme is demonstrated by analysing its response to a range of fault scenarios. Condition monitoring has been successfully used in a diverse range of industries, from rail transport, to commercial power generation, to semiconductor manufacturing, among others. The application of model based condition monitoring to fusion applications has, however, been very limited. Given the importance of improving the availability of fusion devices, it was hypothesised that model based condition monitoring techniques could be used to good effect for this application. This provided the motivation for this research, which had the ultimate objective of demonstrating the usefulness of model based condition monitoring for fusion devices. The cryogenic pumping system used in the neutral beam heating devices operated by the project sponsor, the Culham Centre for Fusion Energy, was selected as the target for a demonstration condition monitoring scheme. This choice of target system was made and justified by the author through an analysis of its role in the neutral beam devices. The relative merits of several model based approaches were investigated. An observer based residual generation scheme, utilising a Kalman filter bank and residual thresholding arrangement was determined to be most suitable. A novel, accurate non-linear simulation model of the cryogenic pumping system was developed to act as a surrogate plant during the research, to facilitate the design and test procedure. This model was validated using historical process data. Two system identification techniques were used to obtain a set of linear models of the system for use in the Kalman filter bank. The scheme was tested by using the non-linear model to simulate ten different faults, all with unique failure modes. Two residual thresholding arrangements were tested and their performance was analysed to find the arrangement with the best performance. It was found that both variations of the scheme could detect all ten faults. The scheme using dual thresholds to check both the direction and magnitude of the residual signals was, however, better at isolating specific faults. The non-linear simulation model developed during the research was proven to be a genuine representation of the plant, by validating its response using historical process data. As such, it could be used in the future as the basis for a model based control system design procedure. The effectiveness of the scheme at detecting a range of faults which can arise in neutral beam heating systems supports the case for the future use of model based condition monitoring in nuclear fusion research

Prototype Bosch CO2 reduction subsystem for the RLSE experiment

Requirements for the Bosch carbon dioxide reduction subsystem were established in a study of regenerative life support evaluation experiments. A detailed design is presented including a schematic, components list and characteristics, requirements summaries, and complete definition of life systems' advanced control/monitor instrumentation applied to the Bosch subsystem. Design information needed to proceed with the final design and fabrication of a preprototype system is presented

A novel qualitative prospective methodology to assess human error during accident sequences

Numerous theoretical models and techniques to assess human error were developed since the 60's. Most of these models were developed for the nuclear, military, and aviation sectors. These methods have the following weaknesses that limit their use in industry: the lack of analysis of underlying causal cognitive mechanisms, need of retrospective data for implementation, strong dependence on expert judgment, focus on a particular type of error, and/or analysis of operator behaviour and decision-making without considering the role of the system in such decisions. The purpose of the present research is to develop a qualitative prospective methodology that does not depend exclusively on retrospective information, that does not require expert judgment for implementation and that allows predicting potential sequences of accidents before they occur. It has been proposed for new (or existent) small and medium- scale facilities, whose processes are simple. To the best of our knowledge, a methodology that meets these requirements has not been reported in literature thus far. The methodology proposed in this study was applied to the methanol storage area of a biodiesel facility. It could predict potential sequences of accidents, through the analysis of information provided by different system devices and the study of the possible deviations of operators in decision-making. It also enabled the identification of the shortcomings in the human-machine interface and proposed an optimization of the current configuration.Fil: Calvo Olivares, Romina Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cuyo. Facultad de Ingenieria. Instituto de Capacitación Especial y Desarrollo de Ingeniería Asistida por Computadora; ArgentinaFil: Rivera, Selva Soledad. Universidad Nacional de Cuyo. Facultad de Ingenieria. Instituto de Capacitación Especial y Desarrollo de Ingeniería Asistida por Computadora; ArgentinaFil: Núñez Mc Leod, Jorge Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cuyo. Facultad de Ingenieria. Instituto de Capacitación Especial y Desarrollo de Ingeniería Asistida por Computadora; Argentin