Maximum heat-transfer coefficient for an immersed body in a bubbling fluidized bed

This paper presents the results of an experimental study of the external heat-exchange with a tube bundle in a bidisperse fluidized bed with marked bimodality of particle size distribution. The dependence of the maximum heat-transfer coefficient on the rate of air filtration was determined. The influence of the mass fraction of large particles on the heat-transfer coefficient in a mixture has been established. An interpolation dependence for calculating the optimal filtration rate of the investigated mixtures has been obtained. It is recommended to use the average surface diameter of the polydisperse particles mixture as the equivalent diameter when calculating the heat-exchange. A method for calculating the maximum heat-transfer coefficient and the optimal filtration rate for a quasi-bidisperse fluidized bed has been developed. The method is based on the use of heat transfer coefficients and optimal filtration rates of individual components of the bidisperse mixture. The equations for calculating the maximum heat-transfer coefficient and the optimal filtration rate in the bidisperse mixture has been obtained.

Maximum heat transfer coefficient between a horizontal tube and a gas-solid fluidized bed

Industrial & Engineering Chemistry Process Design and Development ◽

10.1021/i200012a017 ◽

1981 ◽

Vol 20 (1) ◽

pp. 108-116 ◽

Cited By ~ 35

Author(s):

Nanak S. Grewal ◽

Satish C. Saxena

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Fluidized Bed ◽

Horizontal Tube ◽

Maximum Heat ◽

Maximum Heat Transfer

Enhancement of Nucleate Pool Boiling Heat Transfer with Sodium Oleate

Journal of Chemical Engineering ◽

10.3329/jce.v29i1.33819 ◽

2017 ◽

Vol 29 (1) ◽

pp. 44-48

Author(s):

KM Tanvir Ahmmed ◽

Sultana Razia Syeda

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Sodium Oleate ◽

Surfactant Concentration ◽

Chemical Engineering ◽

Pool Boiling ◽

Nucleate Pool Boiling ◽

Maximum Heat ◽

Maximum Heat Transfer

In this study saturated nucleate pool boiling of water with sodium oleate surfactant on a horizontal cylindrical heater surface has been investigated experimentally and compared with that of demineralized water. The concentration of sodium oleate in water was 100-300 ppm. The experimental results show that a small amount of surfactant enhances the heat transfer coefficient significantly. At low surfactant concentrations, heat transfer coefficient increases with increasing surfactant concentration in water. The maximum heat transfer enhancement is found to be at 250 ppm of sodium oleate solution. By adding more surfactant to water, heat transfer coefficient is found to be lowered. Surface tension of different concentration of sodium oleate solutions is measured. It is observed that the maximum heat transfer coefficient is obtained at a surfactant concentration that corresponds to the critical micelle concentration (cmc) of the sodium oleate solution.Journal of Chemical Engineering, Vol. 29, No. 1, 2017: 44-48

Comparison of heat transfer performance of ZnO-PG, α-Al2O3-PG, and γ-Al2O3-PG nanofluids in car radiator

Nanomaterials and Nanotechnology ◽

10.1177/1847980419876465 ◽

2019 ◽

Vol 9 ◽

pp. 184798041987646 ◽

Cited By ~ 3

Author(s):

XiaoRong Zhou ◽

Yi Wang ◽

Kai Zheng ◽

Haozhong Huang

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Propylene Glycol ◽

Flow Rate ◽

Volume Concentration ◽

Maximum Heat ◽

Cooling Performance ◽

Maximum Heat Transfer ◽

The Heat Transfer Coefficient

In this study, the cooling performance of nanofluids in car radiators was investigated. A car radiator, temperature measuring instrument, and other components were used to set up the experimental device, and the temperature of nanofluids passing through the radiator was measured by this device. Three kinds of nanoparticles, γ-Al2O3, α-Al2O3, and ZnO, were added to propylene glycol to prepared nanofluids, and the effects of nanoparticle size and type, volume concentration, initial temperature, and flow rate were tested. The results indicated that the heat transfer coefficients of all nanofluids first increased and then decreased with an increase in volume concentration. The ZnO-propylene glycol nanofluid reached a maximum heat transfer coefficient at 0.3 vol%, and the coefficient decreased by 25.6% with an increase in volume concentration from 0.3 vol% to 0.5 vol%. Smaller particles provided a better cooling performance, and the 0.1 vol% γ-Al2O3-propylene glycol nanofluid had a 19.9% increase in heat transfer coefficient compared with that of α-Al2O3-propylene glycol. An increase in flow rate resulted in a 10.5% increase in the heat transfer coefficient of the 0.5 vol% α-Al2O3-propylene glycol nanofluid. In addition, the experimental temperature range of 40–60°C improved the heat transfer coefficient of the 0.2 vol% ZnO-propylene glycol nanofluid by 46.4%.

Prediction of the Maximum Heat Transfer Coefficient Between a Horizontal Tube and Gas–Solid Fluidized Beds

Heat Transfer Engineering ◽

10.1080/01457630903550275 ◽

2010 ◽

Vol 31 (10) ◽

pp. 870-879 ◽

Cited By ~ 7

Author(s):

Nima Masoumifard ◽

Navid Mostoufi ◽

Rahmat Sotudeh-Gharebagh

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Fluidized Beds ◽

Horizontal Tube ◽

Maximum Heat ◽

Maximum Heat Transfer

Thermal performance prediction of heat pipe with TiO2 nanofluids using RSM

Thermal Science ◽

10.2298/tsci201229199r ◽

2021 ◽

pp. 199-199

Author(s):

Lakshmi Reddy ◽

Srinivasa Bayyapureddy Reddy ◽

Kakumani Govindarajulu

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Thermal Resistance ◽

Transfer Coefficient ◽

Heat Pipe ◽

Thermal Performance ◽

Tilt Angle ◽

Heat Load ◽

Maximum Heat ◽

Maximum Heat Transfer

Heat pipe is a two phase heat transfer device with high effective thermal conductivity and transfer huge amount of heat with minimum temperature gradient in between evaporator and condenser section. This paper objective is to predict the thermal performance in terms of thermal resistance (R) and heat transfer coefficient (h) of screen mesh wick heat pipe with DI water-TiO2 as working fluid. The input process parameters of heat pipe such as heat load (Q), tilt angle (?) and concentration of nanofluid (?) were modeled and optimized by utilizing Response Surface Methodology (RSM) with MiniTab-17 software to attain minimum thermal resistance and maximum heat transfer coefficient. The minimum thermal resistance of 0.1764 0C/W and maximum heat transfer coefficient of 1411.52 W/m2 0C was obtained under the optimized conditions of 200 W heat load, 57.20 tilt angle and 0.159 vol. % concentration of nano-fluid.

Heat transfer characterization under radial jet and falling film induced rewetting

Kerntechnik ◽

10.1515/kern-2021-0013 ◽

2021 ◽

Vol 86 (5) ◽

pp. 325-337

Author(s):

M. Kumar ◽

D. Mukhopadhyay

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Mass Flow Rate ◽

Flow Rate ◽

Jet Impingement ◽

Falling Film ◽

Maximum Heat ◽

Maximum Heat Transfer ◽

Fuel Pin

Abstract Empirical correlations are developed for rewetting velocity and maximum heat transfer coefficient during rewetting phase of single hot vertical Fuel Pin Simulator (FPS) by using radial jet impingement and falling film. Emergency Core Cooling System (ECCS) has been designed for Advance Heavy water Reactor (AHWR) to rewet the hot fuel pin under the loss of coolant accident. Coolant injection takes place from a water rod which is located at the center of the fuel bundle in form of jets to rewet hot surface of fuel pin under loss of coolant accident. This kind of design to reflood the fuel bundle is different than bottom and top spray reflooding practiced in PWR and BWR type of nuclear reactors. There are two different kinds of rewetting found during radial jet induced cooling. The first one is due to radial jet impingement and the second one is due to falling film which is below the jet impingement point. Rewetting velocity has been predicted along the length of fuel pin due to radial jet impingement cooling. Temperature of FPS has been varied from 400°C to 700°C with help of different powers supply, simulating decay heat of reactor. A variation of coolant radial jet mass flow rate is from 0.5 lpm to 1.8 lpm. It is considered during ECCS injection. It has been observed from the experiments that rewetting velocity decreases with increasing the clad surface temperature and increases with increasing the coolant mass flow rate. The rewetting velocity in falling film is found to be nearly 1.8 times higher than rewetting velocity predicted in circumferential direction. Further, it is found that maximum heat transfer coefficient increases with increasing the radial jet coolant mass flow rate. The maximum heat transfer coefficient in case of radial jet impingement is found to be nearly 1.5 times the falling film rewetting. Developed correlation predicts the maximum heat transfer coefficient with experimental data well within the error band of ±10%.

Heat Transfer between an Individual Carbon Nanotube and Gas Environment in a Wide Knudsen Number Regime

Journal of Nanomaterials ◽

10.1155/2013/181543 ◽

2013 ◽

Vol 2013 ◽

pp. 1-7 ◽

Cited By ~ 4

Author(s):

Hai-Dong Wang ◽

Jin-Hui Liu ◽

Xing Zhang ◽

Tian-Yi Li ◽

Ru-Fan Zhang ◽

...

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Carbon Nanotube ◽

Transfer Coefficient ◽

Heat Dissipation ◽

Critical Diameter ◽

Maximum Heat ◽

Maximum Heat Transfer ◽

Efficient Prediction ◽

Gas Environment

Applications of carbon nanotube (CNT) and graphene in thermal management have recently attracted significant attention. However, the lack of efficient prediction formula for heat transfer coefficient between nanomaterials and gas environment limits the further development of this technique. In this work, a kinetic model has been established to predict the heat transfer coefficient of an individual CNT in gas environment. The heat dissipation around the CNT is governed by molecular collisions, and outside the collision layer, the heat conduction is dominant. At nanoscales, the natural convection can be neglected. In order to describe the intermolecular collisions around the CNT quantitatively, a correction factor 1/24 is introduced and agrees well with the experimental observation. The prediction of the present model is in good agreement with our experimental results in free molecular regime. Further, a maximum heat transfer coefficient occurs at a critical diameter of several nanometers, providing guidelines on the practical design of CNT-based heat spreaders.