Pressure drops, heat transfer coefficient, costs and power block design for direct storage parabolic trough power plants running molten salts

Thick-wall components of the thermal power unit limit maximum heating and cooling rates during start-up or shut-down of the unit. A method of monitoring the thermal stresses in thick-walled components of thermal power plants is presented. The time variations of the local heat transfer coefficient on the inner surface of the pressure component are determined based on the measurement of the wall temperature at one or six points respectively for one- and three-dimensional unsteady temperature fields in the component. The temperature sensors are located close to the internal surface of the component. A technique for measuring the fastchanging fluid temperature was developed. Thermal stresses in pressure components with complicated shapes can be computed using FEM (Finite Element Method) based on experimentally estimated fluid temperature and heat transfer coefficient

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Experimental Study of Evaporation Heat Transfer Characteristics and Pressure Drops of R410A and R134a in a Multiport Mini-Channel

ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels ◽

10.1115/icnmm2009-82209 ◽

2009 ◽

Cited By ~ 1

Author(s):

Jatuporn Kaew-On ◽

Somchai Wongwises

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Pressure Drop ◽

Transfer Coefficient ◽

Transfer Coefficients ◽

Pressure Drops ◽

Heat Transfer Coefficients ◽

Evaporation Heat ◽

Evaporation Heat Transfer ◽

R 134A

The evaporation heat transfer coefficients and pressure drops of R-410A and R-134a flowing through a horizontal-aluminium rectangular multiport mini-channel having a hydraulic diameter of 3.48 mm are experimentally investigated. The test runs are done at refrigerant mass fluxes ranging between 200 and 400 kg/m2s. The heat fluxes are between 5 and 14.25 kW/m2, and refrigerant saturation temperatures are between 10 and 30 °C. The effects of the refrigerant vapour quality, mass flux, saturation temperature and imposed heat flux on the measured heat transfer coefficient and pressure drop are investigated. The experimental data show that in the same conditions, the heat transfer coefficients of R-410A are about 20–50% higher than those of R-134a, whereas the pressure drops of R-410A are around 50–100% lower than those of R-134a. The new correlations for the evaporation heat transfer coefficient and pressure drop of R-410A and R-134a in a multiport mini-channel are proposed for practical applications.

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Effect of nanofluid properties and mass-flow rate on heat transfer of parabolic-trough concentrating solar system

Journal of Naval Architecture and Marine Engineering ◽

10.3329/jname.v16i1.30548 ◽

2019 ◽

Vol 16 (1) ◽

pp. 33-44 ◽

Cited By ~ 1

Author(s):

M.K. Islam ◽

Md. Hasanuzzaman ◽

N.A. Rahim ◽

A. Nahar

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Laminar Flow ◽

Turbulent Flow ◽

Transfer Coefficient ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Parabolic Trough ◽

Concentrated Solar Energy

Sustainable power generation, energy security, and global warming are the big challenges to the world today. These issues may be addressed through the increased usage of renewable energy resources and concentrated solar energy can play a vital role in this regard. The performance of a parabolic-trough collector’s receiver is here investigated analytically and experimentally using water based and therminol-VP1based CuO, ZnO, Al2O3, TiO2, Cu, Al, and SiC nanofluids. The receiver size has been optimized by a simulation program written in MATLAB. Thus, numerical results have been validated by experimental outcomes under same conditions using the same nanofluids. Increased volumetric concentrations of nanoparticle is found to enhance heat transfer, with heat transfer coefficient the maximum in W-Cu and VP1-SiC, the minimum in W-TiO2 and VP1-ZnO at 0.8 kg/s flow rate. Changing the mass flow rate also affects heat transfer coefficient. It has been observed that heat transfer coefficient reaches its maximum of 23.30% with SiC-water and 23.51% with VP1-SiC when mass-flow rate is increased in laminar flow. Heat transfer enhancement drops during transitions of flow from laminar to turbulent. The maximum heat transfer enhancements of 9.49% and 10.14% were achieved with Cu-water and VP1-SiC nanofluids during turbulent flow. The heat transfer enhancements of nanofluids seem to remain constant when compared with base fluids during either laminar flow or turbulent flow.

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Effects of Variation of the Overall Heat Transfer Coefficient in the Feedwater Heaters on the Thermodynamic and Economic Performance of Power Stations

10.1115/imece2000-1355 ◽

2000 ◽

Author(s):

Józef Portacha ◽

Idris A. Elfeituri ◽

Adam Smyk ◽

Jerzy K. Fiszdon

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Power Plant ◽

Transfer Coefficient ◽

Economic Performance ◽

Power Plants ◽

Economic Effects ◽

Operating Conditions ◽

Plant Design ◽

Overall Heat Transfer Coefficient

Abstract This paper examines the effect of the variation of the overall heat transfer coefficient (U) in feedwater heaters on the thermodynamic and economic performance of a coal-fired steam power plant. The changes in the values of U are caused by the heat transfer surface fouling or by errors in the power plant design. These errors often result from the use of approximate heat transfer equations when selecting power plants elements. Low and high pressure feedwater heaters of a power plant equipped with a condensing turbine and a natural circulation steam generator with one reheat stage are considered in this work. The research was conducted using the overall heat transfer coefficients from 50% to 150% of the nominal value. The thermodynamic and economic effects on the power plant were calculated using the mathematical model of the power plant. The power plant components’ mathematical models evaluate the influence of the changes in the heaters’ overall heat transfer coefficient on the thermodynamic (especially exergetic) losses and economic effects. They take into account off-design operating conditions. The decomposition method and multi-level iterative process was used to solve the problem. The research proved that, during operation, the capacity of the power plant might change by up to 2% due to above-mentioned variations. For a 600 MW power plant that means variation of the electric power delivery of approximately 12 MW and increase of the operating costs of up to 4 million dollars per year. The obtained results are particularly useful in the decision-making process in planning renovation and feedwater heaters’ replacement periods.

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CFD Investigation of Spacer-Filled Channels for Membrane Distillation

Membranes ◽

10.3390/membranes9080091 ◽

2019 ◽

Vol 9 (8) ◽

pp. 91

Author(s):

Mariagiorgia La Cerva ◽

Andrea Cipollina ◽

Michele Ciofalo ◽

Mohammed Albeirutty ◽

Nedim Turkmen ◽

...

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Reynolds Numbers ◽

Membrane Distillation ◽

Water Desalination ◽

Process Models ◽

Process Efficiency ◽

Pressure Drops ◽

Temperature Polarization

The membrane distillation (MD) process for water desalination is affected by temperature polarization, which reduces the driving force and the efficiency of the process. To counteract this phenomenon, spacer-filled channels are used, which enhance mixing and heat transfer but also cause higher pressure drops. Therefore, in the design of MD modules, the choice of the spacer is crucial for process efficiency. In the present work, different overlapped spacers are investigated by computational fluid dynamics (CFD) and results are compared with experiments carried out with thermochromic liquid crystals (TLC). Results are reported for different flow attack angles and for Reynolds numbers (Re) ranging from ~200 to ~800. A good qualitative agreement between simulations and experiments can be observed for the areal distribution of the normalized heat transfer coefficient. Trends of the average heat transfer coefficient are reported as functions of Re for the geometries investigated, thus providing the basis for CFD-based correlations to be used in higher-scale process models.

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Experimental Heat Transfer Coefficient and Pressure Drop during Condensation of R-134a and R-410A in Horizontal Micro-fin Tubes

International Journal of Air-Conditioning and Refrigeration ◽

10.1142/s2010132518500220 ◽

2018 ◽

Vol 26 (03) ◽

pp. 1850022 ◽

Cited By ~ 4

Author(s):

Sanjeev Singh ◽

Rajeev Kukreja

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Pressure Drop ◽

Transfer Coefficient ◽

Outer Diameter ◽

Transfer Coefficients ◽

Pressure Drops ◽

Heat Transfer Coefficients ◽

R 134A ◽

Fin Tubes

Condensation heat transfer coefficients and pressure drops of HFC refrigerants R-134a and R-410A have been investigated experimentally in smooth and micro-fin tubes (helix angles 18[Formula: see text] and 15[Formula: see text]) of outer diameter 9.52[Formula: see text]mm at mass fluxes from 200 to 600[Formula: see text]kg/m[Formula: see text]s, vapor qualities between 0.1 and 0.9 and at saturation temperatures of 35[Formula: see text]C and 40[Formula: see text]C. Results showed that the heat transfer coefficients of R-134a and R-410A inside micro-fin tubes were 1.21–1.82 and 1.15–1.47 times higher and frictional pressure drops were 2.11–2.56 and 1.62–2.12 times higher than those of smooth tubes. These experimental results are compared with the existing heat transfer and frictional pressure drop correlations proposed by different researchers. The comparison showed fairly good agreement with these existing correlations within [Formula: see text]30%. A new correlation has also been proposed for predicting heat transfer coefficient in micro-fin tubes. The oil concentrations measured for refrigerants R-134a and R-410A varied in the range of 1.3–1.5%, respectively.

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Heat Transfer and Flow Resistance of a Shell and Plate-Type Evaporator

Journal of Solar Energy Engineering ◽

10.1115/1.2887897 ◽

1997 ◽

Vol 119 (2) ◽

pp. 160-164 ◽

Cited By ~ 7

Author(s):

H. Uehara ◽

E. Stuhltra¨ger ◽

A. Miyara ◽

H. Murakami ◽

K. Miyazaki

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Power Plants ◽

Performance Test ◽

Working Fluid ◽

Side Pressure ◽

Water Side ◽

Boiling Heat Transfer Coefficient ◽

Plate Type

The performance test of a shell-and-plate-type evaporator designed for OTEC plants, geothermal power plants, and heat pump systems is reported. This evaporator contains 30 plates with a unit area of 0.813 m2, coated with aluminum powder on the working fluid side. Freon 22 is used as working fluid. Results show an overall heat transfer coefficient of about 5000 W/(m2K) when the heating water velocity is 1 m/s. The mean boiling heat transfer coefficient is compared with a previous correlation proposed by Nakaoka and Uehara (1988). The water-side pressure loss is also reported.

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Predicting Performance of a Condenser With Plugged Tubes

ASME 2005 Power Conference ◽

10.1115/pwr2005-50057 ◽

2005 ◽

Author(s):

Gene L. Minner ◽

Gerald Weber

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Flow Rate ◽

Water Pressure ◽

Water Flow Rate ◽

Plant Performance ◽

Hydraulic Pressure ◽

Pressure Drops ◽

Circulating Water

The electric power generated in a steam-power plant depends on condenser pressure. Plant performance personnel are frequently called upon to predict effects on megawatts generated and plant heat rate as condenser circumstances vary. The flow rate of circulating water to the condenser is one of the factors that impact the results when doing such predictions. This paper utilizes the PEPSE modeling program to evaluate the effect on the condenser back-pressure and power generation of plugging condenser tubes. The circulating water flow rate is the focal point of this analysis because it influences the heat transfer coefficient inside of the tubes of the condenser. This inside-tube convection heat transfer coefficient is an important contributor to the calculated overall condensing heat transfer coefficient and the resulting condenser pressure. Calculation of the condenser’s shell side pressure is based on the Heat Exchange Institute’s (HEI) methods that are standard in the industry. In operation the circulating water’s flow rate occurs at the point where the head of the circulating water pump balances the hydraulic pressure drops in the circuit. Equations are presented to account for circulating water pressure drops, as foundation for calculations of the hydraulic balancing. The equation methodology is then applied to an actual condenser design.

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Improving the compact heat exchangers with profiled tubes for marine power plants

Journal of Physics Conference Series ◽

10.1088/1742-6596/2150/1/012007 ◽

2022 ◽

Vol 2150 (1) ◽

pp. 012007

Author(s):

A V Naumenko ◽

V D Lychakov ◽

M Yu Egorov ◽

A A Shcheglov ◽

A S Matyash ◽

...

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Heat Exchangers ◽

Power Plants ◽

Good Convergence ◽

Average Value ◽

Flat Tubes ◽

Oil Flow ◽

Cooling Media

Abstract The design features of heat exchangers with flat tubes are considered. The stages of creating a new flat tube and its prototypes are analyzed. An oil refrigerator is chosen as a prototype of the heat exchanger because of the previous use of flat tubes with wells, now replaced with new flat profiled tubes. Thermal and hydraulic tests of a refrigerator made of such tubes are carried out at the stand. During the testing, the hydraulic resistance of the cavities of the cooled and cooling media and thermal parameters are determined: heat power, heat transfer coefficient and heat transfer coefficient from the cooled medium in the inter-tube cavity with the transverse flow of tubes to the tube wall. A satisfactory correspondence of the actual power values determined for both working environments has been established. The discrepancy does not exceed (-7.6%)-(+5%) with an average value of +0.2%. A satisfactory correspondence of the actual and calculated values of the refrigerator power has been obtained. The discrepancy does not exceed (-15%)-(+9%) with an average value of -2.8%. The calculation of the capacity of the refrigerator during its operation in the design mode of oil cooling is carried out. The oil flow is considered both through the pipe and through the inter-pipe space. A good convergence of the calculations with the experimental results has been revealed.

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Numerical Analysis of Heat Transfer Enhancement in a Parabolic Trough Collector Based on Geometry Modifications and Working Fluid Usage

Journal of Solar Energy Engineering ◽

10.1115/1.4040076 ◽

2018 ◽

Vol 140 (5) ◽

Cited By ~ 19

Author(s):

Eric C. Okonkwo ◽

Muhammad Abid ◽

Tahir A. H. Ratlamwala

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Convective Heat Transfer Coefficient ◽

Working Fluid ◽

Al2o3 Nanoparticles ◽

Parabolic Trough ◽

Pressurized Water ◽

Parabolic Trough Collector ◽

Factors Affecting

The parabolic trough collector (PTC) is one of the most widely deployed concentrating solar power technology in the world. This study aims at improving the operational efficiency of the commercially available LS-2 solar collector by increasing the convective heat transfer coefficient inside the receiver tube. The two main factors affecting this parameter are the properties of the working fluid and the inner geometry of the receiver tube. An investigation was carried out on six different working fluids: pressurized water, supercritical CO2, Therminol VP-1, and the addition of CuO, Fe3O4, and Al2O3 nanoparticles to Therminol VP-1. Furthermore, the influence of a converging-diverging tube with sine geometry is investigated because this geometry increases the heat transfer surface and enhances turbulent flow within the receiver. The results showed that of all the fluids investigated, the Al2O3/Oil nanofluid provides the best improvement of 0.22% to thermal efficiency, while the modified geometry accounted for a 1.13% increase in efficiency. Other parameters investigated include the exergy efficiency, heat transfer coefficient, outlet temperatures, and pressure drop. The analysis and modeling of a parabolic trough receiver are implemented in engineering equation solver (EES).

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