scholarly journals Comparative Study on Thermos-Hydraulic Performance of Different Cross Section Shapes of Microchannels with Supercritical CO2 Fluid

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Yi Tu ◽  
Yu Zeng
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Supercritical Co2 ◽  
Heat Transfer Performance ◽  
Hydraulic Performance ◽  
Heat Convection ◽  
Transfer Performance ◽  
Convection Coefficient ◽  
Section Shape ◽  
Supercritical Co2 Fluid

The influence of the cross section shape of microchannels on the thermos-hydraulic performance of the supercritical CO2 fluid is an important issue in the design of industrial compact heat exchangers, but few studies have been conducted about this issue. In this paper, comparative studies of the flow and heat transfer performance of SCO2 fluid in horizontal microchannels with circular, semicircular, rectangle, and trapezoidal cross sections were conducted numerically. The comparison is based on the same hydraulic diameter and length for all channel types and is carried out under the same mass flux, outlet pressure, and wall heat flux. The fluid bulk temperature in this analysis ranges from 285 K to 375 K, which covers the pseudocritical point of SCO2. The results show that the circular channel has the highest average heat convection coefficient, while the trapezoidal channel has the worst convective heat transfer performance under the same hydraulic diameter and boundary conditions. The results also indicate that the effect of cross section shape on the heat convection coefficient is significantly greater than that on the channel pressure drop, and the existence of the corner region in the cross section, especially the acute angle, will weaken the heat transfer performance.

scholarly journals Numerical study on heat transfer and flow resistance characteristics of multi-head twisted spiral tube

2021 ◽  
pp. 206-206
Author(s):  
Zhiqun Zheng ◽  
Fayi Yan ◽  
Lei Shi
Keyword(s):  
Heat Transfer ◽  
Numerical Calculation ◽  
Cross Section ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Smooth Tube ◽  
Transfer Performance ◽  
Spiral Tube ◽  
Inside Diameter ◽  
The Cross

A numerical calculation model of multihead twisted spiral tube (MTST) was established. In the range of Reynolds number from 5000 to 35000, the influence of different twisted structure on the flow and heat transfer characteristics of the MTST was studied by numerical calculation. Numerical calculation results indicate that the Nusselt number and friction coefficient increase with the increase in the ratio of outside and inside diameter of the cross-section, the increase in the number of twisted nodes, and the increase in the number of twisted spiral tube heads. Under the condition of the same spiral structure and the same hydraulic diameter, the heat transfer performance of the MTST is better than that of the spiral smooth tube. In addition, through artificial neural network (ANN) analysis, the ratio of outside and inside diameter of the cross-section, number of twisted nodes, and the number of twisted spiral tube heads were optimized to promote the comprehensive heat transfer performance. The performance evaluation criterion is the highest when the ratio of outside and inside diameter of the cross-section is 25/22.5, the number of twisted nodes is 3, and the number of twisted spiral tube heads is 3, which is 1.849 of the spiral smooth tube.

Flow and Heat Transfer in a Ribbed Channel With Complex Structure Characters

2020 ◽  
Author(s):  
Yu chao Liu ◽  
Tao Guo ◽  
Zong yu Han ◽  
Hui ren Zhu
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Cross Section ◽  
Heat Transfer Performance ◽  
Channel Structure ◽  
Channel Cross Section ◽  
Internal Cooling ◽  
Transfer Performance ◽  
The Real ◽  
The Asymmetry

Abstract The ribbed channels are widely used in the internal cooling structure of turbine blade. Many investigations on this kind of channel were carried on in the channel with rectangle cross section and straight inlet. Nevertheless, in mid-chord region of a real blade, the channel characters are more complex and may affect the heat transfer performance in the channel. The heat transfer investigation in a channel with 3 legs was conducted by numerical simulation. Aim to get the influence of channel structure feature to heat transfer and flow characteristics, the channel was simplified from a real turbine internal cooling channel and main structure features were kept. In order to make the velocity in the first leg close to that in the real structure, the entrance is changed to the contraction entrance. The first leg of channel section is simplified as trapezoid. The legs are connected by 2 U-turns with bend angle for imitating the bend because of the airfoil in real blade. A supplement hole in the inlet of 3rd leg was kept as same as the real channel. Some coolant was supplement to the 3rd leg. Furthermore, 3 rib arrangements (45° ribs, 135° ribs and V-shape ribs) were studied for presenting the interaction between rib arrangement and channel structure character. The results show that: 1) the shape of the inlet cross section has a continuous effect on the irregular velocity in the first leg, the velocity pattern cause by inlet may interact with the secondary flow caused by ribs and lead to different heat transfer distribution compared with the channel with uniform inlet velocity and rectangle cross section. The heat transfer performance in channel with 135° ribs is different from that in the channel with 45° ribs. 2) In the second leg, the secondary flow is generated at the inlet by the bending structure of the leg connection. This secondary flow may suppress or promote the secondary flow produced by ribs. The composed secondary flow leads to the asymmetry flow pattern in the channel and causes the different heat transfer performance in two ribbed walls. 3) In the third leg, the interaction between the flow coming from the supplement hole, the secondary flow caused by ribs and the flow coming from upstream form the complex flow structure. The different rib angle affects the position of high-velocity area. 4) The heat transfer distribution is asymmetry because of the asymmetry channel cross section and bending connecting of legs. The heat transfer performance is different between that in channel with 45° ribs and 135° ribs, whereas is same in the channel with rectangle cross section. Generally speaking, the heat transfer performance is best in the channel with V-shape ribs and is worst in the channel with 45° ribs.

Investigation of the Effect of Cross Section on the Convective Heat Transfer Performance of Nanoemulsion in Microchannel Heat Exchanger

2021 ◽  
Author(s):  
Takele Gameda ◽  
M. Mehdi Kabir ◽  
Jiajun Xu
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Cross Section ◽  
Cross Sections ◽  
Heat Transfer Performance ◽  
Operating Conditions ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Microchannel Heat Exchanger ◽  
Transfer Characteristics

Abstract The present study aims to numerically investigate the effect of cross section on the heat transfer performance of single-phase flow of Ethanol/Polyalphaolefin nanoemulsion fluid with ethanol concentrations of 8 wt.% in a microchannel heat exchanger. While the exterior geometry of the microchannels’ solid structure remains the same, four different cross sections of channels including: circular, upward semi-circular, rectangular, and trapezoidal, are designed with keeping the channels’ wetted perimeters, mass flow rate, and Reynolds number constant for comparison purposes. In the present study, the hydrodynamic and heat transfer characteristics, including local Nusselt number, heat transfer coefficient, and velocity profile, were investigated under a uniform wall heat flux boundary conditions within the laminar flow regime. The channel models of different cross sections were developed by the COMSOL-Multiphysics for numerical analysis. The heat transfer characteristics were then compared for different cross sections under the same operating conditions, and the effect of aspect ratio for rectangular and trapezoidal cross sections were also studied.

scholarly journals The Influence of Pipe Types on The Thermal Performance of Flat-plat Closed Loop Pulsating Heat Pipe

2020 ◽  
Vol 194 ◽  
pp. 01014
Author(s):  
Qingping Wu ◽  
Rongji Xu ◽  
Ruixiang Wang ◽  
Yanzhong Li
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Closed Loop ◽  
Heat Transfer Performance ◽  
Heat Pipes ◽  
Electronic Cooling ◽  
Transfer Performance ◽  
Space Application ◽  
Pulsating Heat Pipe ◽  
Start Up

Flat-plat pulsating heat pipes (FCLPHPs) have a great potentiality in electronic cooling field and space application. In this investigation, three FCLPHPs (L1, L2, and L3) were built to study the influence of cross section shapes on the heat transfer performance of FCLPHP. One (L1) of them has asymmetric pipe, the others (L2, L3) have symmetric pipes. The results indicate that the FCLPHP L1 has the best heat transfer performance. Compared with the FCLPHPs L2 and L3, the start-up time reduces by 64% and the thermal resistance reduces by at most half respectively.

scholarly journals Numerical Study on Thermal Hydraulic Performance of Supercritical LNG in Zigzag-Type Channel PCHEs

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 548 ◽  
Author(s):  
Zhongchao Zhao ◽  
Yimeng Zhou ◽  
Xiaolong Ma ◽  
Xudong Chen ◽  
Shilin Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Mass Flux ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Hydraulic Performance ◽  
Operating Conditions ◽  
Bend Angle ◽  
Transfer Performance

In this paper, we study a promising plate-type heat exchanger, the printed circuit heat exchanger (PCHE), which has high compactness and is suitable for high-pressure conditions as a vaporizer during vaporization. The thermal hydraulic performance of supercritical produce liquefied natural gas (LNG) in the zigzag channel of PCHE is numerically investigated using the SST κ-ω turbulence model. The thermo-physical properties of supercritical LNG from 6.5 MPa to 10MPa were calculated using piecewise-polynomial approximations of the temperature. The effect of the channel bend angle, mass flux and inlet pressure on local convection heat transfer coefficient, and pressure drop are discussed. The heat transfer and pressure loss performance are evaluated using the Nusselt and Euler numbers. Nu/Eu is proposed to evaluate the comprehensive heat transfer performance of PCHE by considering the heat transfer and pressure drop characteristics to find better bend angle and operating conditions. The supercritical LNG has a better heat transfer performance when bend angle is less than 15° with the mass flux ranging from 207.2 kg/(m2·s) to 621.6 kg/(m2·s), which improves at bend angle of 10° and lower compared to 15° at mass flux above 414.4 kg/(m2·s). The heat transfer performance is better at larger mass flux and lower operating pressures.

scholarly journals Towards experimental and modeling study of heat transfer performance of water- SiO2 nanofluid in quadrangular cross-section channels

2019 ◽  
Vol 13 (1) ◽  
pp. 453-469 ◽  
Author(s):  
Alireza Baghban ◽  
Jafar Sasanipour ◽  
Fathollah Pourfayaz ◽  
Mohammad Hossein Ahmadi ◽  
Alibakhsh Kasaeian ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Modeling Study
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