Influence of Secondary Flow Generation on Heat Transfer inside the Fin Type Spiral Sub-Cooled Condenser by Experimental and CFD Analysis

2018 ◽  
Author(s):  
Hardeep Singh ◽  
Takashi Suzuki ◽  
Junya Washiashi ◽  
Mitsuhisa Ichiyanagi ◽  
Jun Liu
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Cfd Analysis ◽  
Flow Generation

scholarly journals An Experimental Analysis of Microchannel Heat Sink using Novel Geometry with Nano Fluid and Water

2019 ◽  
pp. 49-66
Author(s):  
Tushar Singare ◽  
Mohd. Shahnawaz Ansari
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Pressure Drop ◽  
Secondary Flow ◽  
Wavy Channel ◽  
Dean Vortices ◽  
Nano Fluid ◽  
Flow Generation ◽  
Wavy Structure ◽  
Discrete Phase

Oblique fins with sectional cuts are used in place of continuous straight fins to better mix the fluid because of secondary flow in tilted cut oblique channels. The other factor is the re initialization of thermal as well as hydrodynamic boundary layer at the noted line of each fin which decline the density of boundary layer. These breakages of continuous fins resulted in secondary flow generation which enhances the heat transfer rate with reasonable pressure drop. Wavy channel novel geometry is also studied which utilises the length wise blend due to curvy geometry. For laminar region, the amount of convective heat transfer is a function of span wise fluidic mixing. Dean vortices which are cajoled due to centrifugal fluctuation increases the heat transfer capabilities. By clubbing the benefits of both novel geometries i.e. Dean vortices with secondary channel mixing a further better novel geometry branched wavy structure is developed whose fluid movement and heat transfer behaviors were examined numerically. Secondary branches are combined in an alter manner at 45^0 at the trough of the wavy channel to provide cross channel mixing. All the 3 geometries are studied at different range of Reynolds number which ranges from 240 to 600. An increase in heat transfer coefficient as compared to oblique and wavy channel was observed after the addition of secondary branches with decrease in pressure drop penalty. For simulating different geometries in ANSYS 2 methods are implemented which resulted in discrete phase modelling being the better method. The temperature, pressure, velocity contours from simulations were obtained to explain different behaviours.

Local Heat Transfer Measurements in Turbulent Flow Around a 180-deg Pipe Bend

1987 ◽  
Vol 109 (1) ◽  
pp. 43-48 ◽  
Author(s):  
J. W. Baughn ◽  
H. Iacovides ◽  
D. C. Jackson ◽  
B. E. Launder
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Secondary Flow ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Pipe Bend ◽  
Streamline Curvature

The paper reports extensive connective heat transfer data for turbulent flow of air around a U-bend with a ratio of bend radius:pipe diameter of 3.375:1. Experiments cover Reynolds numbers from 2 × 104 to 1.1 × 105. Measurements of local heat transfer coefficient are made at six stations and at five circumferential positions at each station. At Re = 6 × 104 a detailed mapping of the temperature field within the air is made at the same stations. The experiment duplicates the flow configuration for which Azzola and Humphrey [3] have recently reported laser-Doppler measurements of the mean and turbulent velocity field. The measurements show a strong augmentation of heat transfer coefficient on the outside of the bend and relatively low levels on the inside associated with the combined effects of secondary flow and the amplification/suppression of turbulent mixing by streamline curvature. The peak level of Nu occurs halfway around the bend at which position the heat transfer coefficient on the outside is about three times that on the inside. Another feature of interest is that a strongly nonuniform Nu persists six diameters downstream of the bend even though secondary flow and streamline curvature are negligible there. At the entry to the bend there are signs of partial laminarization on the inside of the bend, an effect that is more pronounced at lower Reynolds numbers.

Rotating Effect on Fluid Flow in a Smooth Duct With a 180-Deg Sharp Turn

2000 ◽  
Author(s):  
Chung-Chu Chen ◽  
Tong-Miin Liou
Keyword(s):  
Heat Transfer ◽  
Kinetic Energy ◽  
Secondary Flow ◽  
Turbulent Kinetic Energy ◽  
Turbine Blades ◽  
Outer Part ◽  
Intensity Level ◽  
Mean Velocity ◽  
High Heat Transfer ◽  
Sharp Turn

Laser-Doppler velocimetry (LDV) measurements are presented of turbulent flow in a two-pass square-sectioned duct simulating the coolant passages employed in gas turbine blades under rotating and non-rotating conditions. For all cases studied, the Reynolds number characterized by duct hydraulic diameter (Dh) and bulk mean velocity (Ub) was fixed at 1 × 104. The rotating case had a range of rotation number (Ro = ΩDh/Ub) from 0 to 0.2. It is found that both the skewness of streamwise mean velocity and magnitude of secondary-flow velocity increase linearly, and the magnitude of turbulence intensity level increases non-linearly with increasing Ro. As Ro is increased, the curvature induced symmetric Dean vortices in the turn for Ro = 0 is gradually dominated by a single vortex most of which impinges directly on the outer part of leading wall. The high turbulent kinetic energy is closely related to the dominant vortex prevailing inside the 180-deg sharp turn. For the first time, the measured flow characteristics account for the reported spanwise heat transfer distributions in the rotating channels, especially the high heat transfer enhancement on the leading wall in the turn. For both rotating and non-rotating cases, the direction and strength of the secondary flow with respect to the wall are the most important fluid dynamic factors affecting local heat transfer distributions inside a 180-deg sharp turn. The role of the turbulent kinetic energy in affecting the overall enhancement of heat transfer is well addressed.

Effects of Rib Arrangements on Pressure Drop and Heat Transfer in a Rib-Roughened Channel With a Sharp 180 deg Turn

1997 ◽  
Vol 119 (3) ◽  
pp. 610-616 ◽  
Author(s):  
S. Mochizuki ◽  
A. Murata ◽  
M. Fukunaga
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Secondary Flow ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Diameter Ratio ◽  
Equivalent Diameter ◽  
Before And After ◽  
Rib Roughened

The objective of this study was to investigate, through experiments, the combined effects of a sharp 180 deg turn and rib patterns on the pressure drop performance and distributions of the local heat transfer coefficient in an entire two-pass rib-roughened channel with a 180 deg turn. The rib pitch-to-equivalent diameter ratio P/de was 1.0, the rib-height-to-equivalent diameter ratio e/de was 0.09, and the rib angle relative to the main flow direction was varied from 30 ∼ 90 deg with an interval of 15 deg. Experiments were conducted for Reynolds numbers in the range 4000 ∼ 30,000. It was disclosed that, due to the interactions between the bend-induced secondary flow and the rib-induced secondary flow, the combination of rib patterns in the channel before and after the turn causes considerable differences in the pressure drop and heat transfer performance of the entire channel.

Numerical Investigation on a High Endwall Angle Turbine With Swept-Curved Vanes

2018 ◽  
Author(s):  
Fusheng Meng ◽  
Jie Gao ◽  
Weiliang Fu ◽  
Xuezheng Liu ◽  
Qun Zheng
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Heat Load ◽  
Leading Edge ◽  
Field Calculation ◽  
Prediction Ability ◽  
Expansion Turbine ◽  
Sst Turbulence Model ◽  
Flow Loss ◽  
Lp Turbine

In a high endwall angle turbine, large meridional expansion can cause the strong secondary flow at the endwall, which results in a larger endwall flow loss than the small meridional expansion turbine. The endwall heat transfer is strongly affected by secondary flow effect. In order to optimize the endwall flow to reduce the flow loss and optimize the distribution of heat load, the swept-curved method was used in this study. The swept-curved method was investigated on a transonic second stator (S2) with large meridional expansion in a Low-Pressure (LP) Turbine. Validation studies were performed to investigate the aerodynamic and the heat transfer prediction ability of shear stress transport (SST) turbulence model. The influence of different shapes of the stacking line, including forward-swept, backward-swept, positive-curved and negative-curved, were investigated through numerical simulation. The parameterized control of swept-curved height and angle were adopted to optimize the performance of the aerodynamic and heat transfer. 3D flow field calculation captured the relatively accurate flow structures in the parts of endwall and near endwall. Heat transfer behaviors were explored by means of isothermal wall temperature and Nusselt number (Nu) distribution. The results show that the maximal heat transfer coefficient at the leading edge, for the formation of horseshoe vortexes that cause the high velocity towards the endwall. The swept vane can improve the static pressure and heat load distribution at the endwall region, which decreases the area-averaged shroud heat flux by 2.6 percent and the loss coefficient 1.3 percent.

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