scholarly journals Numerical Study on Heat Transfer of Gaseous Nitrogen Thermoregulation System in Thermal Vacuum Chamber

2019 ◽  
Vol 256 ◽  
pp. 03001
Author(s):  
Zhou Ying ◽  
He Chao ◽  
Bing Bai ◽  
Juan Ning
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Transfer Performance ◽  
Gaseous Nitrogen

Extensive numerical study on the heat transfer performance of the gaseous nitrogen (GN) thermoregulation shroud surface was conducted in this work. The average heat transfer coefficient was investigated under different shroud length and nitrogen parameters (such as velocity, temperature and mass flow rate). The result shows that the heat transfer performance is affected less by shroud length but largely by mass flow rate. When the mass flow rate is constant, the inlet temperature increases heat transfer coefficient. Finally, dimensionless correlation of the average Nusselt number over shroud surface with Reynolds number and Prandtl number was obtained.

scholarly journals Effect of Different Zigzag Channel Shapes of PCHEs on Heat Transfer Performance of Supercritical LNG

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2085 ◽  
Author(s):  
Zhongchao Zhao ◽  
Yimeng Zhou ◽  
Xiaolong Ma ◽  
Xudong Chen ◽  
Shilin Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Convective Heat Transfer Coefficient ◽  
Transfer Performance ◽  
Straight Channel

The channels of a printed circuit heat exchanger (PCHE) can have different shapes, and the zigzag channel shape is one of the most widely used because of the relatively simple manufacturing process and low cost. However, the heat transfer enhancement of a zigzag channel is at the expense of increasing the pressure drop. In this paper, new channel shapes of a PCHE, i.e., a zigzag with an inserted straight channel and a zigzag channel with radian, were numerically investigated, with the aim of improving the heat transfer and reducing the pressure drop of supercritical LNG using the SST κ-ω model. The local and total pressure drop and heat transfer performance of supercritical LNG in a zigzag channel, zigzags with 1–5 mm inserted straight channels, and a zigzag channel with radian were analyzed by varying the mass flow rate from 1.83 × 10−4 to 5.49 × 10−4 kg/s. Performance evaluation criteria (PEC) were applied to compare the overall heat transfer performance of the zigzags with 1–5 mm inserted straight channels and a zigzag channel with radian to the zigzag channel of a PCHE. The maximum pressure drop for the zigzag channel was twice the minimum pressure drop for the zigzag channel with radian, while the convective heat transfer coefficient of the zigzag with a 4 mm inserted straight channel was higher, which was 1.2 times that of the zigzag channel with radian with the smallest convective heat transfer coefficient. The maximum value of the PEC with 1.099 occurred at a mass flow rate of 1.83 × 10−4 kg/s for the zigzag with a 4 mm inserted straight channel, while the minimum value of the PEC with 1.021 occurred at a mass flow rate of 5.49 × 10−4 kg/s for the zigzag with a 1 mm inserted straight channel. The zigzag with a 4 mm inserted straight channel had the best performance, as it had a higher PEC value at lower mass flow rates.

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

2019 ◽  
Vol 16 (1) ◽  
pp. 33-44 ◽  
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.

scholarly journals Experimental Investigation Of Heat Transfer Characteristics Of Nanofluid Using Parallel Flow, Counter Flow And Shell And Tube Heat Exchanger

2015 ◽  
Vol 62 (4) ◽  
pp. 509-522 ◽  
Author(s):  
R. Dharmalingam ◽  
K.K. Sivagnanaprabhu ◽  
J. Yogaraja ◽  
S. Gunasekaran ◽  
R. Mohan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Tube Heat Exchanger ◽  
Overall Heat Transfer Coefficient ◽  
Shell And Tube

Abstract Cooling is indispensable for maintaining the desired performance and reliability over a very huge variety of products like electronic devices, computer, automobiles, high power laser system etc. Apart from the heat load amplification and heat fluxes caused by many industrial products, cooling is one of the major technical challenges encountered by the industries like manufacturing sectors, transportation, microelectronics, etc. Normally water, ethylene glycol and oil are being used as the fluid to carry away the heat in these devices. The development of nanofluid generally shows a better heat transfer characteristics than the water. This research work summarizes the experimental study of the forced convective heat transfer and flow characteristics of a nanofluid consisting of water and 1% Al2O3 (volume concentration) nanoparticle flowing in a parallel flow, counter flow and shell and tube heat exchanger under laminar flow conditions. The Al2O3 nanoparticles of about 50 nm diameter are used in this work. Three different mass flow rates have been selected and the experiments have been conducted and their results are reported. This result portrays that the overall heat transfer coefficient and dimensionless Nusselt number of nanofluid is slightly higher than that of the base liquid at same mass flow rate at same inlet temperature. From the experimental result it is clear that the overall heat transfer coefficient of the nanofluid increases with an increase in the mass flow rate. It shows that whenever mass flow rate increases, the overall heat transfer coefficient along with Nusselt number eventually increases irrespective of flow direction. It was also found that during the increase in mass flow rate LMTD value ultimately decreases irrespective of flow direction. However, shell and tube heat exchanger provides better heat transfer characteristics than parallel and counter flow heat exchanger due to multi pass flow of nanofluid. The overall heat transfer coefficient, Nusselt number and logarithmic mean temperature difference of the water and Al2O3 /water nanofluid are also studied and the results are plotted graphically.

scholarly journals Numerical Study on Regenerative Cooling Characteristics of Kerosene Scramjets

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xuan Jin ◽  
Chibing Shen ◽  
Xianyu Wu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Fluid Velocity ◽  
Regenerative Cooling ◽  
Outlet Pressure

The use of kerosene-based regenerative cooling for scramjet has been found widespread attention due to its inherent nature of high energy utilization efficiency and good thermal protection performance. In order to provide a reference for the later design and experiments, three-dimensional turbulence simulations and sensitivity analysis were performed to determine the effects of three operating mode parameters, heat flux, mass flow rate, and outlet pressure, on the regenerative cooling characteristics of kerosene scramjets. A single rectangular-shaped channel for regenerative cooling was assumed. The RNG k-ε turbulence model and kerosene cracking mechanism with single-step global reaction were applied for the supercritical-pressure heat transfer of kerosene flows in the channel. Conclusions can be drawn that as the kerosene temperature rises along the channel, the decrease of fluid density and viscosity contributes to increasing the fluid velocity and heat transfer. When the kerosene temperature is close to the pseudocritical temperature, the pyrolysis reaction results into the rapid increase of fluid velocity. However, the heat transfer deterioration occurs as the specific heat and thermal conductivity experience their turning points. The higher heat flux leads to lower heat transfer coefficient, and the latter stops rising when the wall temperature reaches the pseudocritical temperature. The same rising trend of the heat transfer coefficient is observed under different outlet pressures, but the heat transfer deterioration occurs earlier at smaller outlet pressure for the reason that the corresponding pseudocritical temperature decreases. The heat transfer coefficient increases significantly along with the rise of the mass flow rate, which is mainly attributable to the increase of Reynolds number. Quantitative results indicate that as the main influence factors, the heat flux and mass flow rate are respectively negatively and positively relative to the intensification of heat transfer, but outlet pressure always has little effects on cooling performance.

The Simulation of Boiling Heat Transfer in Metal Foam Tube

2013 ◽  
Vol 448-453 ◽  
pp. 3312-3315
Author(s):  
Bin Sun ◽  
Bin Bin Cui ◽  
Chao Liang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Boiling Heat Transfer ◽  
Metal Foam ◽  
Vapor Quality ◽  
The Heat Transfer Coefficient

A three-dimensional physical mode of metal foam tube was built by CFD software. The Brinkman-Forchheimer extended Darcy equation and user-defined function (UFD) of the mass transfer and energy transfer between vapor phase and liquid phase compiled by C language were used in the simulation of boiling heat transfer in metal foam tube. The results show that, at a given mass flow rate, the pressure drop nonlinearly increases as the vapor quality rises; At the low mass flow rate, with the increasing of vapor quality, the flow pattern is transferred to wavy flow from stratified flow and then transfer to stratified wavy flow, while the heat transfer coefficient decreases with the increasing of vapor quality. At the high mass flow rate, with the increasing of vapor quality, the flow pattern is transferred to annular flow from slug flow, while the heat transfer coefficient increases with the increasing of vapor quality. The simulation results agree well with the experimental data.

scholarly journals Numerical investigation on the cooling performance of a novel jet cooler design for a supercritical CO2 turbine rotor shaft cooling

2021 ◽  
Vol 22 ◽  
pp. 51
Author(s):  
Jun Li ◽  
Hal Gurgenci ◽  
Jishun Li ◽  
Zhiqiang Guan ◽  
Lun Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Negative Impact ◽  
Dominant Factor ◽  
Transfer Performance ◽  
Fluid Density

Numerical investigation was carried out to study the heat transfer performance for a high-speed rotating cylindrical surface subjected to single row array round jets impingement, under a very small gap spacing. Various parameters that affect heat transfer, such as the fluid density, flow velocity and Nusselt number distributions of the radius clearance were studied based on varied nozzle to target surface spacing H and mass flow rate. It has been found that the fluid density was a dominant factor and the velocity was the secondary factor for the gas jet heat transfer performances. The overall heat transfer was improved with a reduction in the number of nozzles, for given inlet mass flow rate boundary conditions. The decrease of H/di (di, nozzle diameter) may have positive or negative effects on the heat transfer performance from the impingement surface. Reducing the radius gap H, for a certainty, increases the average density of the fluid in the clearance, which is desirable in applications that enhance heat transfer performance. But when the radius gap (H) is small enough, increasing di may have a negative impact on heat transfer.

Investigations on the Effect of Blade Angle on Ventilated Brake Disc Using CFD

2005 ◽  
Author(s):  
Kannan M. Munisamy ◽  
Hanan Mokhtar ◽  
Hasril Hasini ◽  
Mohd Zamri Yusof ◽  
Mohd Azree Idris
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Linear Trend ◽  
Brake Disc ◽  
Blade Angle ◽  
Flow And Heat Transfer

This paper presents the investigation on the effect of blade angle to the mass flow and heat transfer coefficient of a ventilated brake disc. Six different blade angle configurations are simulated using commercial computational fluid dynamics code, FLUENT. Important parameters such as mass flow rate of air through the ventilated blade and surface heat transfer coefficient are predicted and analyzed. Prediction shows reasonable estimation of mass flow rate and heat transfer coefficient on the disc brake. Linear trend is achieved on the mass flow and heat transfer coefficient as the vehicle speed increases. It is also concluded that the optimum mass flow and heat transfer coefficient are predicted at blade angle of 15°. The prediction provides an insight into the behavior of the air flow through the restricted passage of the brake disc design.

Sign in / Sign up

Export Citation Format

Share Document