Browsing by Subject "Solar radiation simulation"
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Item An experimental simulation of asymmetric radiant heating for the FMDF receiver(Texas Tech University, 1978-12) Shinn, Kim ENot availableItem Design and analysis of a distributed control system for a multi-bowl solar power plant(Texas Tech University, 1985-05) Bryans, Mark AdrianThe Cnosbyton Solar Power Project has proposed a design for a solar-fossil hybrid electric power plant. The proposed plant will utilize ten hemispherical solar collections and a fossil boiler to produce 5 MWe on a steady basis. Before the final design for this plant can be made, detailed operational procedures must be defined. This study investigates the development of a control algorithm for the multi-bowl plant by the use of a computer simulation. The first objective was to develop a one bowl simulation model. The one bowl model simulates the exit temperature given the solar insolation, the temperature setpoint, and the pressure setpoint. The one bowl simulation model was tested with data from July 5, 1980. The rms error between the simulated exit temperature and the actual exit temperature was 6.2% of the temperature setpoint. The one bowl model was then incorporated into a multi-bowl model. For an N-bowl system there is one master controller and N-1 slave controllers. The master controller consists of the one bowl model, the economic model, and the master communication software. The economic model is used to determine the appropriate temperature and pressure setpoints for each bowl based on economic and environmental conditions. The slave controllers each consist of the one bowl model integrated with the appropriate slave communication software. A three bowl system was simulated, but the results can be extrapolated to a system with any number of bowls. Three computers were used, instead of one, so that the simulation could be executed in parallel. The multi-bowl simulation showed that a distributed control system would be ideal for the proposed power plant. Also, the simulation showed that this type of control strategy is flexible and can be easily expanded on modified.Item Development and use of a duststorm simulation chamber to evaluate solar concentrator degradation as characterized by loss in reflectivity(Texas Tech University, 1980-12) Collier, Elwin GreggNot availableItem Forced convection heat transfer to a single and two-phase steam/water mixture in a helical coil with radiant heating(Texas Tech University, 1981-12) Vafaie, Foad NThe purpose of this study has been to perform an analytical and experimental investigation into the heat transfer characteristics for a once-through steam generator with a helical flow geometry. The application is the receiver for a fixed hemispherical mirror solar concentrator on the Crosbyton Solar Power Project. In this design, the working fluid, water, goes successively through the single-phase liquid, two-phase and super-heated vapor regimes in a once-through, helically wrapped tube bundle subjected to nonuniform, asymmetrical radiant heating. Individual segments of the radiation profile for the receiver were simulated using high intensity, line source quartz lamps providing concentrations of up to 240 suns. A segment of the helical coil was instrumented and mounted in the radiation field. Test section instrumentation included inlet fluid flow rate, inlet and exit fluid pressure and temperature, and 42 type K thermocouples welded to the surface of the coil. The incident radiation field was mapped using a Gordon type heat flux transducer calibrated for the quartz lamp spectrum. An upstream hot oil heat exchanger provided inlet fluid conditions to the test section consistent with the segment of the receiver being simulated e.g., single-phase or two-phase. The range of test conditions included an incident radiation flux of 6,000 to 27,000 Btu/hr-ft , a flow rate of 100 to 500 Ibm/hr, an inlet pressure of 100 to 500 psia, and an inlet quality of 0 to 70 percent. A numerical analysis was developed to predict the local internal heat transfer coefficients and fluid state based on the measurements obtained in the test procedure discussed above. The analysis included consideration of the externally applied radiation field, convective and radiative heat losses, two-dimensional conduction through the tube wall, and.convection to the internal fluid. The results show that there is a significant change in the angtilar variation of the internal heat transfer coefficient at low quality when compared with values for high quality. At low quality, the highest internal heat transfer coefficients are obtained on the tube surface farthest from the axis of the coil. At high qualities, this changes to yield the highest coefficients on the tube surface closest to the coil axis. Factors contributing to this phenomena include radial acceleration, induced secondary flow, flow acceleration along the flow axis, and the onset of film boiling. The integrated average values of the heat transfer coefficient for the subcooled liquid and two-phase were correlated against dimensionless parameters of the flow such as the Reynolds number, Prandtl number, boiling number and tube-to-coil diameter ratio.Item Reflection characteristics at large incident angles with reference to solar bowl(Texas Tech University, 1988-05) Trahan, Markham RayA computer code was developed for the Crosbyton Solar Power Project to calculate the optical concentration along the receiver of the Crosbyton Solar Bowl. The predicted values have been in agreement with the observed data during the middle period of the solar day. However, optical flux distributions along the receiver in the mornings and afternoons have been found to be approximately 8 percent below what was predicted for the system. The purpose for this investigation is to identify the cause(s) for this discrepancy. To account for these discrepancies, a set of simple experiments were performed in the lab using the same kind of mirrors which are mounted on the solar bowl. The data analysis and calculations show that a significant quantity of this discrepancy is due to the focusing defect caused by two properties of back surface reflecting mirrors. They are surface defects introduced during the manufacturing process, and internal reflections between the glass/air interface and the back reflecting surface. These properties have significant effect at large incidence angles.Item Simulation of the Crosbyton receiver(Texas Tech University, 1986-12) Subramanyam, SavithriA thermal-fluid model was developed to describe the collector/ receiver for a fixed-mirror distributed-focus (FMDF) spherical arc reflector. The performance of the system is predicted using a mechanistic model solving an enthalpy balance with the appropriate heat-transfer and pressure-drop correlations. The model includes a rigorous package for predicting the thermodynamic and transport properties for the water/steam system. The steady-state model predicts the exit conditions of the steam, and the radiation and convection losses from the receiver for a given set of Inlet conditions. A correlation based on dimensionless numbers predicts the overall efficiency of the receiver, the exit enthalpy, and the pressure drop for a given heat-flux profile. These predictions compare favorably with the rigorous model results over the ranges tested. The model also predicts the transient response of the collector/ receiver system to disturbances in the input variables. The results of the transient analysis provide insight to the type of control system required to handle start-up, shut-down, intermittent cloudy periods, and failure modes. Thermlnol 55 and molten salt were also used as transport fluids in the case studies. The feasibility of a new type of receiver called the "gun-barrel” design was explored.Item Simulation of the Receiver in a Fixed-Mirror Distributed Focus Solar Power System(Texas Tech University, 1981-08) Shankar, HariharanNot Available.