Dimensionless Analysis of Pressure Drop and Heat Transfer on HTGR Coupled With Closed Brayton Cycle

2010 ◽  
Author(s):  
Zhenjia Yu ◽  
Xiaoyong Yang ◽  
Xiaoli Yu ◽  
Jie Wang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Compression Ratio ◽  
High Efficiency ◽  
Great Influence ◽  
Brayton Cycle ◽  
Local Pressure ◽  
Reynolds Analogy ◽  
Pressure Drops ◽  
Frictional Pressure Drop

High temperature gas-cooled reactor with direct helium turbine cycle is based on the closed Brayton cycle. Its outstanding feature is the high efficiency of power generation. Pervious researches showed that recuperator was the key component to promote the cycle’s efficiency. And pressure drops in components were unavoidable in actual projects and had significant influence on cycle efficiency. A dimensionless model was proposed to analyze cycle’s features of HTGR coupled with gas turbine. The parameters’ effect on cycle’s efficiency was analyzed, with full consideration of the frictional and local pressure drops respectively. Under the restriction of materials and state-of-art of technologies, it showed that the cycle’s efficiency depended on compression ratio, recuperator’s effectiveness and pressure drops of components. However the pressure drop ratios of different components were inherently connected due to the closed cycle. Furthermore pressure drops inside the recuperator were also the function of effectiveness of the heat transfer based on the Reynolds analogy. Therefore cycle’s efficiency just depended on recuperator’s effectiveness with fixed compression ratio. So there existed optimal recuperator’s effectiveness and maximum cycle’s efficiency, which varied with the pressure ratio and other parameters as temperature ratio. The calculation also indicated that the pressure drop in pipes was close to that in heat exchangers. That was, the local pressure drop and frictional pressure drop should be considered respectively, and the local pressure drop made quite large reduction of cycle’s efficiency. The result also showed that local pressure drop had great influence on parameters such as optimal compression ratio and recuperator’s effectiveness.

scholarly journals Numerical Study of Thermal-Hydraulic Performance of a New Spiral Z-Type PCHE for Supercritical CO2 Brayton Cycle

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4417
Author(s):  
Tingting Xu ◽  
Hongxia Zhao ◽  
Miao Wang ◽  
Jianhui Qi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Pressure Loss ◽  
Numerical Study ◽  
Hydraulic Performance ◽  
Optimal Structure ◽  
Original Structure ◽  
Brayton Cycle ◽  
Compact Structure ◽  
Spiral Angle

Printed circuit heat exchangers (PCHEs) have the characteristics of high temperature and high pressure resistance, as well as compact structure, so they are widely used in the supercritical carbon dioxide (S-CO2) Brayton cycle. In order to fully study the heat transfer process of the Z-type PCHE, a numerical model of traditional Z-type PCHE was established and the accuracy of the model was verified. On this basis, a new type of spiral PCHE (S-ZPCHE) is proposed in this paper. The segmental design method was used to compare the pressure changes under 5 different spiral angles, and it was found that increasing the spiral angle θ of the spiral structure will reduce the pressure drop of the fluid. The effects of different spiral angles on the thermal-hydraulic performance of S-ZPCHE were compared. The results show that the pressure loss of fluid is greatly reduced, while the heat transfer performance is slightly reduced, and it was concluded that the spiral angle of 20° is optimal. The local fluid flow states of the original structure and the optimal structure were compared to analyze the reason for the pressure drop reduction effect of the optimal structure. Finally, the performance of the optimal structure was analyzed under variable working conditions. The results show that the effect of reducing pressure loss of the new S-ZPCHE is more obvious in the low Reynolds number region.

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

2009 ◽  
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.

Shellside Waterflow Pressure Drop Distribution Measurements in an Industrial-Sized Test Heat Exchanger

1988 ◽  
Vol 110 (1) ◽  
pp. 60-67 ◽  
Author(s):  
H. Halle ◽  
J. M. Chenoweth ◽  
M. W. Wambsganss
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Operating Cost ◽  
Power Requirement ◽  
Pressure Drops ◽  
Pressure Losses ◽  
Finned Tubes ◽  
Heat Exchanger Design ◽  
Isothermal Water

Throughout the life of a heat exchanger, a significant part of the operating cost arises from pumping the heat transfer fluids through and past the tubes. The pumping power requirement is continuous and depends directly upon the magnitude of the pressure losses. Thus, in order to select an optimum heat exchanger design, it is is as important to be able to predict pressure drop accurately as it is to predict heat transfer. This paper presents experimental measurements of the shellside pressure drop for 24 different segmentally baffled bundle configurations in a 0.6-m (24-in.) diameter by 3.7-m (12-ft) long shell with single inlet and outlet nozzles. Both plain and finned tubes, nominally 19-mm (0.75-in.) outside diameter, were arranged on equilateral triangular, square, rotated triangular, and rotated square tube layouts with a tube pitch-to-diameter ratio of 1.25. Isothermal water tests for a range of Reynolds numbers from 7000 to 100,000 were run to measure overall as well as incremental pressure drops across sections of the exchanger. The experimental results are given and correlated with a pressure drop versus flowrate relationship.

scholarly journals Fabrication of Monolithic Catalysts: Comparison of the Traditional and the Novel Green Methods

Catalysts ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 981 ◽  
Author(s):  
Zexuan Wang ◽  
Kunfeng Zhao ◽  
Bei Xiao ◽  
Peng Gao ◽  
Dannong He ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
High Efficiency ◽  
Utilization Rate ◽  
The Novel ◽  
Surface Deposition ◽  
Advantages And Disadvantages ◽  
Monolithic Catalysts ◽  
Mass And Heat Transfer ◽  
Application Prospects

Monolithic catalysts have great industrial application prospects compared to powdered catalysts due to their low pressure drop, the high efficiency of mass and heat transfer, and recyclability. Deposition of active phases on the monolithic carriers dramatically increases the utilization rate and has been attracting continuous attention. In this paper, we reviewed the traditional (impregnation, coating, and spraying) and novel (hydrothermal and electrodeposition) strategies of surface deposition integration, analyzed the advantages and disadvantages of both ways, and then prospected the possible directions for future development of integration technologies.

Numerical Evaluation of Pressure Drop Across Orifices for Different Gas-Liquid Mixtures

2018 ◽  
Author(s):  
Zurwa Khan ◽  
Reza Tafreshi ◽  
Matthew Franchek ◽  
Karolos Grigoriadis
Keyword(s):  
Numerical Model ◽  
Pressure Drop ◽  
Water Flow ◽  
Fuel Oil ◽  
Phase Flow ◽  
Empirical Correlations ◽  
Local Pressure ◽  
Two Phase ◽  
Pressure Drops ◽  
Mass Fractions

Modeling two-phase flow across orifices is critical in optimizing orifice design and fluid’s operation in countless architectures and machineries. While flow across different orifice geometries has been extensively studied for air-water flow, simulations and experiments on other two-phase flow combinations are limited. Since every fluid mixture has its own physical properties, such as densities, viscosities and surface tensions, the effect of these properties on the local pressure drops across the orifices may differ. This study aims to investigate the effect of different fluid combinations on the pressure drop across sharp-edged orifices with varying gas mass fractions, orifice thicknesses, and area ratios. A numerical model was developed and validated using experimental data for air-water flow. Then, the model was extended to include various gas-liquid flows including gasoil, argon-diesel and fuel oil. The local pressure drops were then estimated and compared with the existing empirical correlations. The developed model presents a unified approach to measure pressure drop across orifices for different fluid mixtures with different geometries and gas-liquid compositions, unlike existing empirical correlations which are applicable for specific orifice geometries. The results showed that Morris correlation, Simpson correlation, and Chisholm correlation are more appropriate for gasoil, argon-diesel and fuel oil mixtures, respectively. They also yielded that for all fluid combinations, increasing orifice thickness and area ratio led to a decrease in local pressure drop, while increasing gas mass fraction led to an increase in local pressure drop. This revealed that, despite having similar responses to changes in orifice geometries and gas fractions, unlike the assumption made by previous works on air-water flow, no empirical correlation is able to predict pressure drops for all flow mixtures, while the presented numerical model can efficiently determine the local pressure drop for all combinations of flow mixtures, orifice geometries and gas mass fractions.

Experimental Investigation of Condensation Heat Transfer and Adiabatic Pressure Drop Characteristics Inside a Microfin and Smooth Tube

2017 ◽  
Vol 25 (03) ◽  
pp. 1750027 ◽  
Author(s):  
M. Mostaqur Rahman ◽  
Keishi Kariya ◽  
Akio Miyara
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Frictional Pressure Drop

Experiments on condensation heat transfer and adiabatic pressure drop characteristics of R134a were performed inside smooth and microfin horizontal tubes. The tests were conducted in the mass flux range of 50[Formula: see text]kg/m2s to 200[Formula: see text]kg/m2s, vapor quality range of 0 to 1 and saturation temperature range of 20[Formula: see text]C to 35[Formula: see text]C. The effects of mass velocity, vapor quality, saturation temperature, and microfin on the condensation heat transfer and frictional pressure drop were analyzed. It was discovered that the local heat transfer coefficients and frictional pressure drop increases with increasing mass flux and vapor quality and decreasing with increasing saturation temperature. Higher heat transfer coefficient and frictional pressure drop in microfin tube were observed. The present experimental data were compared with the existing well-known condensation heat transfer and frictional pressure drop models available in the open literature. The condensation heat transfer coefficient and frictional pressure drop of R134a in horizontal microfin tube was predicted within an acceptable range by the existing correlation.

scholarly journals The Effect of Periodic Ribs on the Local Aerodynamic and Heat Transfer Performance of a Straight Cooling Channel

1996 ◽  
Author(s):  
G. Rau ◽  
M. Çakan ◽  
D. Moeller ◽  
T. Arts
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Heat Transfer Performance ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Diameter ◽  
Transfer Performance ◽  
Local Pressure ◽  
Reynolds Analogy ◽  
Law Of The Wall

The local aerodynamic and heat transfer performance were measured in a rib-roughened square duct as a function of the rib pitch to beight ratio. The blockage ratio of these square obstacles was 10% or 20% depending on whether they were placed on one single (1s) or on two opposite walls (2s). The Reynolds number, based on the channel mean velocity and hydraulic diameter, was fixed at 30000. The aerodynamic description of the flow field was based on local pressure distributions along the ribbed and adjacent smooth walls as well as on 2D LDV explorations in the channel symmetry plane and in two planes parallel to the ribbed wall(s). Local heat transfer distributions were obtained on the floor, between the ribs, and on the adjacent smooth side wall. Averaged parameters, such as friction factor and averaged heat transfer enhancement factor, were calculated from the local results and compared to correlations given in literature. This contribution showed that simple correlations derived from the law of the wall similarity and from the Reynolds analogy could not be applied for the present rib height-to-channel hydraulic diameter ratio (e/Dh=0.1). The strong secondary flows resulted in a three-dimensional flow field with high gradients in the local heat transfer distributions on the smooth side walls.

Effect of Pressure Drop and Reheating on Thermal and Exergetic Performance of Supercritical Carbon Dioxide Brayton Cycles Integrated With a Solar Central Receiver

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Ricardo Vasquez Padilla ◽  
Yen Chean Soo Too ◽  
Andrew Beath ◽  
Robbie McNaughton ◽  
Wes Stein
Keyword(s):  
Carbon Dioxide ◽  
Pressure Drop ◽  
Supercritical Carbon Dioxide ◽  
Surface Temperature ◽  
Brayton Cycle ◽  
Pressure Drops ◽  
Central Receiver ◽  
Maximum Value ◽  
Solar Receiver ◽  
Exergy Performance

Concentrated solar power using supercritical carbon dioxide (S-CO2) Brayton cycles offers advantages of similar or higher overall thermal efficiencies than conventional Rankine cycles using superheated or supercritical steam. The high efficiency and compactness of S-CO2, as compared with steam Rankine cycles operating at the same temperature, make this cycle attractive for solar central receiver applications. In this paper, S-CO2 Brayton cycle is integrated with a solar central receiver that provides heat input to the power cycle. Three configurations were analyzed: simple, recompression (RC), and recompression with main intercooling (MC). The effect of pressure drop in heat exchangers and solar receiver and solar receiver surface temperature on the thermal and exergetic performance of the CO2 Brayton cycle with and without reheat condition was studied. Energy, exergy, and mass balance were carried out for each component and the cycle first law and exergy efficiencies were calculated. In order to obtain optimal operating conditions, optimum pressure ratios were obtained by maximizing the cycle thermal efficiency under different pressure drops and solar receiver temperature conditions. Optimization of the cycle first law efficiency was carried out in python 2.7 by using sequential least squares programing (SLSQP). The results showed that under low pressure drops, adding reheat to the S-CO2 Brayton cycle has a favorable effect on the thermal and exergy efficiencies. Increasing pressure drop reduces the gap between efficiencies for reheat and no reheat configuration, and for pressure drop factors in the solar receiver above 2.5%, reheat has a negligible or detrimental effect on thermal and exergy performance of S-CO2 Brayton cycles. Additionally, the results showed that the overall exergy efficiency has a bell shape, reaching a maximum value between 18.3% and 25.1% at turbine inlet temperatures in the range of 666–827 °C for different configurations. This maximum value is highly dependent on the solar receiver surface temperature, the thermal performance of the solar receiver, and the solar field efficiency. As the solar receiver surface temperature increases, more exergy destruction associated with heat transfer losses to the environment takes place in the solar receiver and therefore the overall exergy efficiency decreases. Recompression with main intercooling (MC) showed the best thermal (ηI,cycle > 47% at Tin,turbine > 700 °C) and exergy performance followed by RC configuration.

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