Analytical Dynamic Modeling of Line-Focus Solar Collectors

1981 ◽  
Vol 103 (3) ◽  
pp. 244-250 ◽  
Author(s):  
J. D. Wright
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Industrial Process ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Fluid Flow Rate ◽  
Digital Controllers ◽  
Dynamics Models ◽  
Line Focus

Solar thermal electric power and industrial process heat systems may require a constant outlet temperature from the collector field. This constant temperature is most efficiently maintained by adjusting the circulating fluid flow rate. Successful tuning of analog or digital controllers requires a knowledge of system dynamics. Models relating deviations in outlet temperature to changes in inlet temperature, insolation, and fluid flow rate illustrate the basic responses and the distributed-parameter nature of line-focus collectors. When plotted in dimensionless form, the frequency response of a given collector is essentially independent of the operating conditions, suggesting that feedback controller settings are directly related to such easily determined quantities as collector gain and fluid residence time.

Consideration of Uncertainties in Compact Cross-Flow Heat Exchanger Design for Gas Turbine Engine Application

2013 ◽  
Author(s):  
Randall D. Manteufel ◽  
Daniel G. Vecera
Keyword(s):  
Fluid Flow ◽  
Heat Exchanger ◽  
Gas Turbine ◽  
Flow Rate ◽  
Cross Flow ◽  
Inlet Temperature ◽  
Fluid Flow Rate ◽  
Heat Exchanger Design ◽  
Cold Fluid ◽  
Flow Heat

Recent experimental work characterized the performance of a unique cross-flow heat exchanger design for application of cooling compressor bleed air using liquid jet fuel before it is consumed in the gas turbine combustor. The proposed design has micro-channels for liquid fuel and cools air flowing in passages created using rows of intermittent fins. The design appears well suited for aircraft applications because it is compact and light-weight. A theoretical model is reported to be in good agreement with experimental measurements using air and water, thus providing a design tool to evaluate variations in the heat exchanger dimensions. This paper presents an evaluation of the heat exchanger performance with consideration of uncertainties in both model parameters and predicted results. The evaluation of the design is proposed to be reproduced by students in a thermal-fluids design class. The heat exchanger performance is reevaluated using the effectiveness–NTU approach and shown to be consistent with the method reported in the original papers. Results show that the effectiveness is low and in the range of 20 to 30% as well as the NTU which ranges from 0.25 to 0.50 when the heat capacity ratio is near unity. The thermal resistance is dominated by the hot gas convective resistance. The uncertainties attributed to fluid properties, physical dimensions, gas pressure, and cold fluid flow rate are less significant when compared to uncertainties associated with hot fluid flow rate, hot fluid inlet temperature, cold fluid inlet temperature, and convective correlation for gas over a finned surface. The model shows which heat transfer mechanisms are most important in the performance of the heat exchanger.

scholarly journals Effect of Fluid Flow Rate on Efficacy of Fluid Warmer: An In Vitro Experimental Study

2018 ◽  
Vol 2018 ◽  
pp. 1-4
Author(s):  
Vorasruang Thongsukh ◽  
Chanida Kositratana ◽  
Aree Jandonpai
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Room Temperature ◽  
Core Body Temperature ◽  
Infusion Pump ◽  
Outlet Temperature ◽  
Fluid Temperature ◽  
Fluid Flow Rate ◽  
Flow Rates ◽  
Fluid Warmer

Introduction. In patients who require a massive intraoperative transfusion, cold fluid or blood transfusion can cause hypothermia and potential adverse effects. One method by which to prevent hypothermia in these patients is to warm the intravenous fluid before infusion. The aim of this study was to determine the effect of the fluid flow rate on the efficacy of a fluid warmer. Methods. The room air temperature was controlled at 24°C. Normal saline at room temperature was used for the experiment. The fluid was connected to an infusion pump and covered with a heater line, which constantly maintained the temperature at 42°C. The fluid temperature after warming was measured by an insulated thermistor at different fluid flow rates (100, 300, 600, 900, and 1200 mL/h) and compared with the fluid temperature before warming. Effective warming was defined as an outlet fluid temperature of >32°C. Results. The room temperature was 23.6°C ± 0.9°C. The fluid temperature before warming was 24.95°C ± 0.5°C. The outlet temperature was significantly higher after warming at all flow rates (p<0.001). The increases in temperature were 10.9°C ± 0.1°C, 11.5°C ± 0.1°C, 10.2°C ± 0.1°C, 10.1°C ± 0.7°C, and 8.4°C ± 0.2°C at flow rates of 100, 300, 600, 900, and 1200 mL/h, respectively. The changes in temperature among all different flow rates were statistically significant (p<0.001). The outlet temperature was >32°C at all flow rates. Conclusions. The efficacy of fluid warming was inversely associated with the increase in flow rate. The outlet temperature was <42°C at fluid flow rates of 100 to 1200 mL/h. However, all outlet temperatures reached >32°C, indicating effective maintenance of the core body temperature by infusion of warm fluid.

Thermal Performance Analysis of the Stationary Reflector/Tracking Absorber (SRTA) Solar Concentrator

1975 ◽  
Vol 97 (3) ◽  
pp. 451-456 ◽  
Author(s):  
J. F. Kreider
Keyword(s):  
Fluid Flow ◽  
High Temperature ◽  
Flow Rate ◽  
Thermal Performance ◽  
Concentration Ratio ◽  
Heat Energy ◽  
Operating Conditions ◽  
Fluid Flow Rate ◽  
Wide Range ◽  
Temperature Heat

The performance of a novel solar energy concentrating system consisting of a fixed, concave spherical mirror and a sun-tracking, cylindrical absorber is analyzed in detail. This concentrating system takes advantage of the spherical symmetry of the mirror and its linear image which, when taken together, form a tracking, solar-concentrating system in which only the small cylindrical absorber need move. The effects of mirror reflectance, concentration ratio, heat transfer fluid flow rate, radiative surface properties, incidence angle, an evacuated absorber envelope, and insolation level upon thermal performance of the concentrator are studied by means of a mathematical model. The simulation includes first order radiation and convection processes between the absorber and its concentric glass envelope and between the envelope and the environment; radiation processes are described by a dual-band, gray approximation. The energy equations are solved in finite difference form in order that heat flux and temperature distributions along the absorber may be computed accurately. The results of the study show that high-temperature heat energy can be collected efficiently over a wide range of useful operating conditions. The analysis indicates that mirror surface reflectance is the single most important of the principal governing parameters in determining system performance. Efficiency always increases with concentration ratio although the rate of increase is quite small for concentration ratios above 50. High fluid flow rate (i.e., lower operating temperature), an evacuated envelope, or a highly selective surface can enhance performance under some conditions. The conclusion of the study is that high-temperature heat energy can be generated at high efficiency by the present concentrator with present technology in sunny regions of the world.

Temperature Control of Line-Focus Solar Collectors

1983 ◽  
Vol 105 (2) ◽  
pp. 194-199
Author(s):  
J. D. Wright ◽  
M. Masterson
Keyword(s):  
Flow Rate ◽  
Rate Control ◽  
Industrial Process ◽  
Low Flow ◽  
Outlet Temperature ◽  
Fluid Flow Rate ◽  
Controller Tuning ◽  
Flow Rates ◽  
Rules Of Thumb ◽  
Flow Rate Control

Solar thermal electric power and industrial process heat systems may require a constant outlet temperature from the collector. This temperature may be efficiently maintained by adjusting the circulating fluid flow rate. Using frequency response techniques, simple relations are developed which relate controller tuning constants to collector construction and field layout. Successful controller tuning is shown to be a compromise between good response at high flow rates and stability at low flow rates. The rules of thumb are then tested by performing dynamic numerical simulations of a collector row with flow rate control.

Buoyancy Effects on Thermal Behavior of a Flat-Plate Solar Collector

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Jianhua Fan ◽  
Simon Furbo
Keyword(s):  
Fluid Flow ◽  
Temperature Distribution ◽  
Flow Rate ◽  
Solar Collector ◽  
Reverse Flow ◽  
Flow Distribution ◽  
Experimental Investigations ◽  
Inlet Temperature ◽  
Fluid Flow Rate ◽  
Cfd Model

Theoretical and experimental investigations of the flow and temperature distribution in a 12.53m2 solar collector panel with an absorber consisting of two vertical manifolds interconnected by 16 parallel horizontal fins have been carried out. The investigations are focused on overheating and boiling problems in the collector panel. Single-phase liquid flow and heat transfer in the collector panel are studied by means of computational fluid dynamics (CFD) calculations. Differently designed collectors are investigated with different collector fluid volume flow rates. The effect of friction and the influence of the buoyancy effects are considered in the investigations. Further, experimental investigations of the solar collector panel are carried out. The flow distribution through the absorber is evaluated by means of temperature measurements on the back of the absorber tubes. The measured temperatures are compared to the temperatures determined by the CFD model and there is a good agreement between the measured and calculated temperatures. Calculations with the CFD model elucidate the flow and temperature distribution in the collector. The influences of collector fluid flow rate and inlet temperature on the flow and temperature distribution are shown. The flow distribution through the absorber tubes is uniform if a high flow rate of 10.0l∕min is used. By decreased collector fluid flow rate and by increased collector fluid inlet temperature, the flow distribution gets less uniform due to the influence of buoyancy force. If the collector fluid flow rate is small and the collector fluid inlet temperature is high enough, severe nonuniform flow distribution may happen with a small flow rate or even zero or reverse flow in the upper horizontal strips, resulting in overheating or boiling problems in the strips. The CFD calculations elucidate the flow and temperature distribution in the collector panels of different designs. Based on the investigations, recommendations are given in order to avoid overheating or boiling problems in the solar collector panel.

scholarly journals Process Simulation for Crude Oil Stabilization by Using Aspen Hysys

2020 ◽  
pp. 14-28
Author(s):  
Hussein Al- Ali
Keyword(s):  
Fluid Flow ◽  
Vapor Pressure ◽  
Crude Oil ◽  
Flow Rate ◽  
Water Flow Rate ◽  
Inlet Temperature ◽  
Fluid Temperature ◽  
Fluid Flow Rate ◽  
Aspen Hysys ◽  
True Vapor

A light fluid from different reservoir formation started recently to associate the production of the crude oil stabilization plant which is unfortunately not enough to release off all light components and as a results the true vapor pressure increased in the storage tanks more than 12 psi. From the results in Aspen Hysys, it was found that manipulating of working parameters for the existing plant likewise the inlet temperature, dry fluid flow rate, water flow rate and the temperature of the outlet fluid from Fired heater have no great effect on the true vapor pressure (TVP). The TVP at normal feed conditions of 50.5 C and for the plant with third and fourth stages are 14.96 Kg/Cm2. a and 10.23 Kg/Cm2. a, respectively. It was found that for the third stage, the changing in feed flow rates for both dry and water have no effect on the reducing TVP, while to stabilized the TVP for the exported crude oil within range of (68947.6 – 82737.1) Pa/(10 – 12) psia when the the fourth separator used in the process plant, the feed dry fluid flow rate (26.4 – 105.6) KBD, the minimum base sediment and water cut in the feed stream 4 Vol%, the inlet fluid temperature (43-51.5)⁰C and the differential temperature across the fired heater in range of (16-24)⁰C with feed temperature range (40-55)⁰C.

scholarly journals Assessment of the Influence of Graphene Nanoparticles on Thermal Conductivity of Graphene/Water Nanofluids Using Factorial Design of Experiments

2018 ◽  
Vol 62 (3) ◽  
pp. 317-322 ◽  
Author(s):  
Srinivasan Manikandan Periasamy ◽  
Rajoo Baskar
Keyword(s):  
Thermal Conductivity ◽  
Fluid Flow ◽  
Factorial Design ◽  
Flow Rate ◽  
Inlet Temperature ◽  
Fluid Temperature ◽  
Fluid Flow Rate ◽  
23 Factorial Design ◽  
Contour Plots ◽  
Factorial Design Of Experiments

In this study, 23 factorial design of experiment was employed to evaluate the effect of parameters of hot fluid inlet temperature, graphene nanofluid concentration and hot fluid flow rate on thermal conductivity of graphene/water nanofluid. The levels of  hot fluid inlet temperature are kept at 35°C and 85°C, nanofluid concentration is kept at 0.1 and 1.0 volume% (vol.%) and the hot fluid flow rate are kept at 2 lpm and 10 lpm. Experiments were conducted with 16 runs as per MINITAB design software using graphene/water nanofluids in the corrugated plate type heat exchanger.  The nanofluid thermal conductivity was determined using the mixing rule for different nanofluid concentrations ranging from 0.1 to 1.0%. Normal, Pareto, Residual, Main and Interaction effects, Contour Plots were drawn. The Analysis of Variance (ANOVA) of test results depict that the hot fluid temperature and nanofluid concentration have significant effect on the thermal conductivity of graphene/water nanofluid (response variable).

Application of Cross-correlation Analysis Method for Measurement of the Fluid Flow Rate Based on X-ray Radiation

2019 ◽  
Vol 11 (1) ◽  
pp. 01025-1-01025-5 ◽  
Author(s):  
N. A. Borodulya ◽  
◽  
R. O. Rezaev ◽  
S. G. Chistyakov ◽  
E. I. Smirnova ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Correlation Analysis ◽  
Flow Rate ◽  
Cross Correlation ◽  
Fluid Flow Rate ◽  
Analysis Method ◽  
X Ray ◽  
Cross Correlation Analysis ◽  
Correlation Analysis Method

Flow Features Analysis of Throttle Notches of Proportional Direct Valve

2011 ◽  
Vol 189-193 ◽  
pp. 2285-2288
Author(s):  
Wen Hua Jia ◽  
Chen Bo Yin ◽  
Guo Jin Jiang
Keyword(s):  
Fluid Flow ◽  
Dynamic Behavior ◽  
Flow Rate ◽  
Discharge Coefficient ◽  
3D Models ◽  
Operating Conditions ◽  
Flow Models ◽  
Flow Features ◽  
Rate Discharge ◽  
Spool Valve

Flow features, specially, flow rate, discharge coefficient and efflux angle under different operating conditions are numerically simulated, and the effects of shapes and the number of notches on them are analyzed. To simulate flow features, 3D models are developed as commercially available fluid flow models. Most construction machineries in different conditions require different actions. Thus, in order to be capable of different actions and exhibit good dynamic behavior, flow features should be achieved in designing an optimized proportional directional spool valve.

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