William E. Simon

Incorporation of Flow Pattern Phenomena Into the Study of Advanced Micro Cooling Modules

The need for high-performance thermal protection and fluid management techniques for systems ranging from cryogenic reactant storage devices to primary structures and propulsion systems exposed to extreme high temperatures, and other space systems such as cooling or environmental control for advanced space suits and integrated electronic circuits, requires an effective cooling system to accommodate the compact nature and high heat fluxes associated with these applications. A two-phase forced-convection, phase-transition system can accommodate such requirements through the use of the concept of Advanced Micro Cooling Modules (AMCMs), which are essentially compact two-phase heat exchangers constructed of microchannels and designed to remove large amounts of heat rapidly from critical systems by incorporating phase transition. Realizing the significance of research in this area, this paper presents the results of experimental research on two-phase flow in microchannels with verification and identification of data using concomitant measurement systems, where based on the experimental research conducted on air-water mixture flows in the entire range of concentration and flow patterns in a horizontal square microchannel, a mathematical model based on in situ parameters is developed and presented, which describes pressure losses in two-phase flow incorporating flow pattern phenomena. Validation of the model is accomplished. A hypothetical model for the two-phase heat transfer coefficient is also presented, which incorporates the flow patterns through the use of a flow pattern coefficient.Copyright

Flow Pattern Phenomena in Two‐Phase Flow in Microchannels

Space transportation systems require high‐performance thermal protection and fluid management techniques for systems ranging from cryogenic fluid management devices to primary structures and propulsion systems exposed to extremely high temperatures, as well as for other space systems such as cooling or environment control for advanced space suits and integrated circuits. Although considerable developmental effort is being expended to bring potentially applicable technologies to a readiness level for practical use, new and innovative methods are still needed. One such method is the concept of Advanced Micro Cooling Modules (AMCMs), which are essentially compact two‐phase heat exchangers constructed of microchannels and designed to remove large amounts of heat rapidly from critical systems by incorporating phase transition. The development of AMCMs requires fundamental technological advancement in many areas, including: (1) development of measurement methods/systems for flow‐pattern measurement/identification for two‐phase mixtures in microchannels; (2) development of a phenomenological model for two‐phase flow which includes the quantitative measure of flow patterns; and (3) database development for multiphase heat transfer/fluid dynamics flows in microchannels. This paper focuses on the results of experimental research in the phenomena of two‐phase flow in microchannels. The work encompasses both an experimental and an analytical approach to incorporating flow patterns for air‐water mixtures flowing in a microchannel, which are necessary tools for the optimal design of AMCMs. Specifically, the following topics are addressed: (1) design and construction of a sensitive test system for two‐phase flow in microchannels, one which measures ac and dc components of in‐situ physical mixture parameters including spatial concentration using concomitant methods; (2) data acquisition and analysis in the amplitude, time, and frequency domains; and (3) analysis of results including evaluation of data acquisition techniques and their validity for application in flow pattern determination.

Analysis of a low-gravity reflux boiler system for lunar surface thermal management

Thermal control systems are essential to providing crew and equipment with an adequate thermal environment for space missions and outposts such as a lunar base. One concept for this is a reflux boiler system for lunar surface thermal control, in which heat is transferred from a thermal bus to vertical tubes and radiated to space. Several light-weight tube configurations have been built and tested by various manufacturers. This paper describes a mathematical model of such a device, including the performance of a single tube and a linear array of tubes. Model verification is demonstrated through correlation with NASA vacuum chamber test data. Following this, performance comparisons are made between three manufactured configurations of the tubes for similar environmental conditions and with the tube dimensions normalized with respect to one another, and conclusions are reached relative to the heat rejection capability of the three devices. Performance predictions for a linear array of tubes operating in a lunar surface environment are also presented.

System Advisor Model (SAM) simulation modelling of a concentrating solar thermal power plant with comparison to actual performance data

Abstract This paper is focused on the modelling and simulation of a 50 kW concentrated solar power (CSP) plant located in Crowley, Louisiana. The model was developed using system advisor model (SAM). The objective is to develop a predictive model (using SAM) to characterize the performance of the power plant and, thus, aid the analysis and evaluation of the plant’s performance. The power plant is a research facility of the Solar Thermal Applied Research and Testing (START) Lab. The model was validated by comparing its predictions with the actual plant data. The comparison showed a good correlation between the predicted results and the actual plant data. The validated model was then used to perform parametric analyses across different locations. The analyses showed that by operating the power plant at the optimal combination of solar multiple and hours of storage, we can achieve about 70% reduction in the cost of electrical energy.

Mathematical Model of Two‐Phase Flow in Advanced Micro Cooling Modules Incorporating Flow Pattern Phenomena

This paper presents the results of experimental research on two‐phase flow in a microchannel with verification and identification of data using concomitant measurement systems. Based on the results of the experimental research conducted on air‐water mixture flows in the full range of concentration and flow patterns in a horizontal square microchannel, a mathematical model based on in situ parameters is developed and presented. The model describes pressure losses in two‐phase flow incorporating flow pattern phenomena. A relation for the two‐phase heat transfer coefficient is also presented, which incorporates the flow patterns using a flow pattern coefficient. This model significantly reduces the difference between the experimental and calculated values typically encountered in previous efforts.

Fuel Cell Integrated Energy System for Residential and Commercial Applications

Until recently the cost of fuel cells for terrestrial applications was prohibitive. Recently, several companies have begun developing high-performance, long-life and cost-effective fuel cell systems, and commercial units are now becoming available for stationary power generation. These systems can often be operated in conjunction with other energy systems to increase overall operational efficiency. A recent technology demonstration project at the University of Louisiana at Lafayette involved the installation, operation and analysis of a fuel cell and a desiccant dehumidification system, which is considered a good combination for the hot, humid climate of the U.S. Gulf coast. The three-year project involved technology assessment, hardware selection and procurement, installation, and operation of the two systems, followed by a performance analysis. The results were reported in a regional symposium. This paper describes the project, focusing on system operation and the results obtained, and predicts future possibilities for integrated energy systems of this type.Copyright

Optimization of a low-gravity two-phase system for lunar heat rejection

A mathematical model of a low-gravity reflux boiler system for lunar-surface heat rejection, including the performance of a single tube and a linear array of tubes, is described. Model verification is demonstrated throughcorrelation with NASA vacuum chamber test data. Performance comparisons are made between three manufactured configurations of the tubes for similar environmental conditions and with the tube dimensions normalized with respect to one another. Finally, the optimization of a linear array of composite tubes for operation in a worstcase lunar surface thermal environment is presented. A pitch-to-diameter ratio of between 4 and 5 is recommended because that choice provides over 95% of the maximum heat transfer with a more logistically feasible array.

Optimization of a low-gravity reflux boiler system for lunar surface thermal control

A key element for space missions and outposts such as a lunar base is a well-designed thermal control system which provides an adequate thermal environment for both crew and equipment. One concept for accomplishing this is a reflux boiler device which operates like a heat pipe, transferring waste heat from the habitat module via a thermal bus to vertical tubes radiating to space. A previous paper by these authors describes a mathematical model of several lightweight tube configurations which had been built and tested by various manufacturers. Following model verification through correlation with NASA vacuum chamber test data, the model was used to simulate both single tubes and a linear array of tubes for lunar surface operation. After comparing the heat rejection capability of three pf the manufactured tubes under similar conditions with normalized tube dimensions, performance predictions for a linear array of tubes operating in the lunar surface environment were then developed. The subject of this paper is an extension of the simulation effort for one of these tube types, which includes the optimization of a linear array of composite tubes for operation in a worst-case lunar surface thermal environment.