scholarly journals Experimental study on forced convective heat transfer of supercritical carbon dioxide in a horizontal circular tube under high heat flux and low mass flux conditions

2019 ◽  
Vol 11 (3) ◽  
pp. 168781401983080 ◽  
Author(s):  
Junhui Wang ◽  
Pengcheng Guo ◽  
Jianguo Yan ◽  
Fengling Zhu ◽  
Xingqi Luo
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Heat Flux ◽  
Supercritical Carbon Dioxide ◽  
Mass Flux ◽  
High Heat ◽  
High Heat Flux ◽  
Buoyancy Effect ◽  
Low Mass ◽  
Supercritical Carbon

This study focuses on the convective heat transfer characteristics of supercritical carbon dioxide flowing in a horizontal circular tube under high heat flux and low mass flux conditions. The influences of thermophysical property, buoyancy effect, and thermal acceleration on the heat transfer characteristics are discussed. The parameters are as follows: system pressure is 7.6–8.4 MPa, mass flux is 400–500 kg/m2 s, heat flux is 30–200 kW/m2, fluid temperature is 20°C −62°C, and Reynolds number is 1.23 × 104 to 4.3 × 104. The wall temperature and heat transfer coefficient of supercritical carbon dioxide are obtained. The results show that, under the condition of high heat flux and low mass flux, heat transfer deterioration would happen, in which thermophysical property and buoyancy effect are the main factors. When the pressure is 7.6 MPa, the buoyancy factor is greater than 10−3 in the whole heat transfer area, and the buoyancy effect cannot be ignored, while the thermal acceleration factor is 9.5 × 10−8 to 4 × 10−6 and the effect of thermal acceleration can be negligible. The experimental data are compared with the predictions using seven empirical correlations, in which the Liao–Zhao correlation shows the best performance.

Numerical Investigation of Buoyancy Effect on Forced Convective Heat Transfer to Supercritical Carbon Dioxide Flowing in a Heated Tube

2018 ◽  
Author(s):  
Liu Sheng-hui ◽  
Huang Yan-ping ◽  
Liu Guang-xu ◽  
Wang Jun-feng
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Heat Flux ◽  
Supercritical Carbon Dioxide ◽  
Convective Heat Transfer ◽  
Numerical Investigation ◽  
Convective Heat ◽  
Mass Flux ◽  
Buoyancy Effect ◽  
Forced Convective Heat Transfer

Numerical investigation of buoyancy effect on forced convective heat transfer to supercritical carbon dioxide flowing in a vertical tube was carried out. When the mass flux is low and wall heat flux high, it shows that the buoyancy effect is obvious, which might redistribute the radial and axial velocity, even M shaped distribution in the radial direction. When the zero-velocity-gradient region corresponding to the M shaped velocity distribution appears in the edge of viscous layer, the production and diffusion of eddy will be weakened, resulting in heat transfer deterioration. According to the extended simulations based on experimental data, reducing the wall heat flux, adding the mass flux or raising the inlet temperature can relieve the deterioration of heat transfer caused by buoyancy effect.

scholarly journals Design Optimization of Plate-Fin Heat Exchanger in a Gas Turbine and Supercritical Carbon Dioxide Combined Cycle with Thermal Oil Loop

2021 ◽  
Vol 12 (1) ◽  
pp. 42
Author(s):  
Yue Cao ◽  
Jun Zhan ◽  
Jianxin Zhou ◽  
Fengqi Si
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Genetic Algorithm ◽  
Heat Flux ◽  
Supercritical Carbon Dioxide ◽  
Pareto Frontier ◽  
Combined Cycle ◽  
Nsga Ii ◽  
Thermal Oil ◽  
Supercritical Carbon

This paper presents an investigation on the optimum design for a plate-fin heat exchanger (PFHE) of a gas and supercritical carbon dioxide combined cycle which uses thermal oil as intermediate heat-transfer fluid. This may promote the heat transfer from low heat-flux exhaust to a high heat-flux supercritical carbon dioxide stream. The number of fin layers, plate width and geometrical parameters of fins on both sides of PFHE are selected as variables to be optimized by a non-dominated sorting genetic algorithm-II (NSGA-II), which is a multi-objective genetic algorithm. For the confliction of heat transfer area and pressure drop on the exhaust side, which are the objective indexes, the result of NSGA-II is a Pareto frontier. The technique for order of preference by similarity to ideal solution (TOPSIS) approach is applied to choose the optimum solution from the Pareto frontier. Finally, further simulation is performed to analyze the effect of each parameter to objective indexes and confirm the rationality of optimization results.

High Flux Microscale Solar Thermal Receiver for Supercritical Carbon Dioxide Cycles

2015 ◽  
Author(s):  
Thomas L’Estrange ◽  
Eric Truong ◽  
Charles Rymal ◽  
Erfan Rasouli ◽  
Vinod Narayanan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Heat Flux ◽  
Supercritical Carbon Dioxide ◽  
Surface Temperature ◽  
Thermal Efficiency ◽  
Solar Thermal ◽  
Fluid Temperature ◽  
Thermal Receiver ◽  
Supercritical Carbon

Characterization of a microchannel solar thermal receiver for a supercritical carbon dioxide (sCO2) is presented. The receiver design is based on conjugate computational fluid dynamics and heat transfer simulations as well as thermo-mechanical stress analysis. Two receivers are fabricated and experimentally characterized — a parallel microchannel design and a microscale pin fin array design. Lab-scale experiments have been used to demonstrate the receiver integrity at the design pressure of 125 bar at 750°C surface temperature. A concentrated solar simulator was designed and assembled to characterize the thermal performance of the lab scale receiver test articles. Results indicate that, for a fixed exit fluid temperature of 650°C, increase in incident heat flux results in an increase in receiver and thermal efficiency. At a fixed heat flux, efficiency decreased with an increase in receiver surface temperature. The ability to absorb flux of up to 100 W/cm2 at thermal efficiency in excess of 90 percent and exit fluid temperature of 650°C using the microchannel receiver is demonstrated. Pressure drop for the pin array at the maximum flow rate for heat transfer experiments is less than 0.64 percent of line pressure.

Sign in / Sign up

Export Citation Format

Share Document