CFD Investigation of Hydrodynamic and Heat Transfer Phenomena around Trilobe Particles in Hydrocracking Reactor

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Mohammad Reza Bandari ◽  
Yaghoub Behjat ◽  
Shahrokh Shahhosseini
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Film ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Film Formation ◽  
Liquid Volume ◽  
Liquid Volume Fraction

In this work, computational fluid dynamics (CFD) has been employed to compute local convection heat transfer coefficient (h) that is the key parameter in calculation of heat transfer rate between the particle and fluids in packed bed reactors. In addition, the relation between Reynolds number and Nusselt number for spherical and trilobe catalyst particles have been investigated. Moreover, the parameters of Ranz-Marshall (R-M) correlation have been estimated in order to use it for trilobe catalyst particle. The heat transfer coefficients of the spherical and trilobe particles were compared and the effect of particle shape and configuration on heat transfer rate has been investigated. Eulerian-Eulerian approach was employed in order to investigate gas-liquid hydrodynamic especially liquid film formation around trilobe particles. The effects of liquid film around a trilobe particle and liquid volume fraction on heat transfer coefficient have also been studied. The CFD simulation results indicate that increasing inlet liquid volume fraction raises the liquid film thickness around the particles leading to reduction of heat transfer coefficient. In addition, the results revealed that flow field and temperature profiles around the particles became more complicated as a result of liquid film formation and gas-liquid interactions.

Investigation of Ethylene Glycol Heat Transfer Coefficient Trough Double Pipe and Coil Heat Exchanger

2021 ◽  
Vol 874 ◽  
pp. 165-170
Author(s):  
Sri Wuryanti ◽  
Tina Mulya Gantina ◽  
Indriyani
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Ethylene Glycol ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Test System ◽  
Double Pipe ◽  
The Heat Transfer Coefficient ◽  
Outer Pipe

The research objective is to assemble a convection test system which acts as a heat exchanger (HE) and test its applicability using ethylene glycol. A Double Pipe (DP)-type HE consists of an inner pipe surrounded by an outer pipe (annulus) whereas a Coil-type HE composed of a coil surrounded by an outer pipe. Water flows through the outer pipe in both types of HE, while ethylene glycol flows through the inner piper or coil. HE in combination with other components (such as) forms a convection test system. The applicability of the system was tested to determine the heat transfer coefficient of ethylene glycol in a DP-type and Coil-type HEs. After that, the heat transfer rate was calculated and compared. The results show that the heat transfer coefficient in the DP-type HE is the lowest at 12.2 W/m2 oC and the highest at 26.8 W/m2 oC; and the corresponding heat transfer rate is the lowest at 8.3 W and the highest is 56.3 W. In comparison, for Coil-type HE, the lowest heat transfer coefficient is 38.9 W/m2 oC and the highest is 66.2 W/m2 oC which correspond to the heat transfer rate 19.9 W at the lowest and 225 W at the highest.

scholarly journals Enhancement of Temperature Distribution and Heat Transfer Coefficient of Ribbed Tube by Simulation

2021 ◽  
Vol 7 (1) ◽  
pp. 21-28
Author(s):  
Rahul Kunar ◽  
Dr Sukul Lomash
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Flow Analysis ◽  
Total Heat ◽  
Total Heat Transfer ◽  
The Heat Transfer Coefficient

The heat transfer from surface may in general be enhanced by increasing the heat transfer coefficient between a surface and its surrounding or by increasing heat transfer area of the surface or by both. The main objective of the study and calculate the total heat transfer coefficient. Improve the heat transfer rate by using ANSYS CFD. During the CFD calculations of the flow in internally ribbed tubes. And calculated the temperature distribution and pressure inside the tube by using ansys. The model was created using CatiaV5 and meshed with Ansys, and the flow analysis is done with Ansys 19.2. The results showing that the heat transfer is increased. The enthalpy and temperature increase with flow is advancing when compare with normal boiler tube. In this study the total heat transfer rate of the pipe increase with the increase the rib height. Total heat transfer rate increase up to 7.7kw. The study show that the improvement in furnace heat transfer can be achieved by changing the internal rib design.

Experimental Study and High Speed Visualization of Flow Boiling Characteristics in Silicon Microgap Heat Sink

2012 ◽  
Author(s):  
Tamanna Alam ◽  
Poh Seng Lee ◽  
Christopher R. Yap ◽  
Liwen Jin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Heat Sink ◽  
Transfer Rate ◽  
High Speed ◽  
Flow Boiling ◽  
Gap Size

Flow boiling in microgap heat sink is very attractive for high-performance electronics cooling due to its high heat transfer rate and easy fabrication process. In absence of thermal interface material between the active electronic component and a microgap cold plate, significant reduction in interface thermal resistance and enhancement in heat transfer rate can be achieved. In earlier studies by these authors, encouraging results have been obtained using microgap heat sink as it can potentially mitigate flow instabilities, flow reversal and maintain uniform wall temperatures over the heated surface. So, more work should be carried out to advance the fundamental understanding of the two-phase flow heat transfer associated with microgap heat sink and the underlying mechanisms. In this study, local flow boiling phenomena in different microgap sizes have been investigated experimentally. Experiments are performed in silicon based microgap heat sink having microgap depth ranging from 80 μm to 500 μm, using deionized water with 10 °C subcooled inlet temperature. The effects of mass flux and heat flux on heat transfer coefficient and pressure drop characteristics are examined by using different mass fluxes ranging from 400 kg/m2s to 1000 kg/m2s and effective heat flux varying from 0 to 100 W/cm2. Apart from these experimental investigations, simultaneous high speed visualizations are conducted to observe and explore the mechanism of flow boiling in microgap. Confined slug and annular boiling are observed as the two main heat transfer mechanisms in microgap. Moreover, experimental results show that flow boiling heat transfer coefficients are dependent on gap size, and the lower the gap size, higher the heat transfer coefficient.

Turbulent Multi-Jet Air Impingement for Applications in Commercial Cooking

2018 ◽  
Author(s):  
Shantanu S. Shevade ◽  
Muhammad M. Rahman ◽  
Rasim O. Guldiken
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Convective Heat Transfer Coefficient ◽  
Diameter Ratio ◽  
Impingement Surface

Convective heat transfer coefficient and its interdependency with various key parameters is analyzed for turbulent multi-jet impingement. Air is used as the working fluid impinging on the flat surface via a three-nozzle arrangement. A thorough investigation of velocity and temperature distribution is performed by varying Nozzle Velocity, Height over Diameter ratio (H/D) and Spacing over Diameter ratio (S/D). Convective heat transfer coefficient, average impingement surface temperature, and heat transfer rate are calculated over the impingement surface. It was found that higher S/D ratios result in higher local heat transfer coefficient values near stagnation point. However, increased spacing between the neighboring jets results in less coverage of the impingement surface reducing the average heat transfer. Lower H/D ratios result in higher heat transfer coefficient peaks. The peaks for all three nozzles are more uniform for H/D ratios between 6 and 8. For a fixed nozzle velocity, heat transfer coefficient values are directly proportional to nozzle diameter. For a fixed H/D and S/D ratio, heat transfer rate and average impingement surface temperature increase as the nozzle velocity increases until it reaches a limiting value. Further increase in nozzle velocity causes drop in heat transfer rate due to ingress of large amounts of cold ambient air in the cooking space.

Heat Transfer Studies on Condensation Using Heat Pipes

2014 ◽  
Vol 592-594 ◽  
pp. 1617-1621 ◽  
Author(s):  
Punit Singh ◽  
S. Venkatachalapathy ◽  
G. Kumaresan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Condensation Heat Transfer ◽  
Vertical Position ◽  
Horizontal Position ◽  
Vertical Orientation

This experimental study finds the effect of condensation on the thermal performance of heat pipe. Condensation heat transfer rate, heat transfer coefficient and variation of temperature over the heat pipe are measured at vertical and horizontal position of HP, by varying the steam-to-surface temperature difference. It is found that the condensation heat transfer rate for vertical position of heat pipe with CuO nanofluid is 2.07 times higher than the horizontal position, whereas the increase in heat transfer coefficient is 1.94 times. Using CuO nanofluid instead of deionized water in the heat pipe enhances the heat transfer rate and heat transfer coefficient by 1.25 and 1.42 times respectively for the vertical orientation.

scholarly journals Experimental and CFD analysis of swirl, nozzle arrangement, cross-section and jets diameter on heat transfer in multi-jet air impingement cooling

2019 ◽  
Vol 23 (3 Part B) ◽  
pp. 2025-2035
Author(s):  
Palaniappan Chandramohan ◽  
Suruli Nagarajan ◽  
Sundaraganesan Arivazhagan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Cross Section ◽  
Transfer Rate ◽  
Cfd Analysis ◽  
Impingement Cooling ◽  
Line Arrangement ◽  
Air Impingement

Experimental investigation and CFD analysis were performed to study the effects of swirl, nozzle arrangement, cross section of nozzle, number of jets and jet diameter on heat transfer coefficient in multi-jet air impingement cooling for a target surface of 100 ?150 mm size supplied with a constant heat flux of 7666 W/m2. The normalized heat transfer coefficient based on unit volume of air is evaluated through measurement of temperature for flow Reynolds numbersin the range of 8000-22000 with H/D ratiosof 1, 2, 4, and 6. Investigations with and without swirl reveal that among the tested conditions, for 8 mm jets, introducing swirl reduces the heat transfer where as for 10 mm and 12 mm jets, swirl improves the average heat transfer rate. For sets of 12 nozzles configurations, the staggered arrangement for 6 mm and 8 mm nozzles results in higher heat transfer rate than in-line arrangement unlike in 4 mm nozzles where in-line arrangement is better. Heat transfer coefficients for circular, square and triangular cross-sections of same flow area have been compared. Circular cross-section offers better heat transfer coefficient for all the tested conditions. For a given number of nozzles, there is an optimum diameter corresponding to maximum value of normalized heat transfer coefficient. The results are corroborated with CFD analysis for a few representative conditions tested.

Heat Transfer Studies in Coiled Agitated Vessel with Varying Heat Input

2011 ◽  
Vol 7 (4) ◽  
Author(s):  
V T Perarasu ◽  
M Arivazhagan ◽  
P Sivashanmugam
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Heat Input ◽  
Transfer Rate ◽  
Empirical Correlations ◽  
Agitated Vessel ◽  
Experimental Values ◽  
The Heat Transfer Coefficient

Heat transfer studies in a coiled agitated vessel with varying heat input is presented using two agitators namely propeller and disk turbine. Heat transfer rate increases with agitator speed for both the agitators for a given heat input. The heat transfer coefficient also increases with heat input for a given agitator speed for turbine agitator for all the heat inputs, whereas for propeller it is increasing up to a certain value and then decreases. The heat transfer coefficient (heat transfer rate) for turbine agitator is higher than that for propeller for all heat inputs. Empirical correlations separately were formed for each agitator and found to fit the experimental values within range of ±15% for both the agitators.

scholarly journals ANALISIS PERPINDAHAN PANAS GLAND STEAM CONDENSOR DI PT PJB UBJOM PULANG PISAU KALTENG

JTAM ROTARY ◽  
2020 ◽  
Vol 2 (2) ◽  
pp. 207
Author(s):  
Muhammad Rizky Hidayat ◽  
Aqli Mursadin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Shaft Seal ◽  
Maximum Heat ◽  
Condensate Pump ◽  
Maximum Heat Transfer ◽  
Turbine Shaft

Gland Steam Condensor (GSC) adalah alat penukar panas yang mengembunkan uap dari segel poros turbin. Steam bekas ini akan memanaskan air kondensat dari pompa kondensat yang dialirkan melintasi kondensor Gland Steam. Karena panas diserap oleh air kondensat, maka steam bekas dari seal poros akan mengembun kemudian dialirkan ke hotwell hingga bercampur dengan air hotwell. Dari hasil penelitian koefisien perpindahan kalor tertinggi pada tabung adalah 80.491,93 btu/hr ft2 pada hari Rabu jam 14.00. Diketahui bahwa koefisien perpindahan panas pada tabung terendah adalah 79.011,94 btu/hr ft2 pada hari Senin jam 16.00. Koefisien perpindahan panas tertinggi pada cangkang adalah 5.294.695 btu/jam ft2 pada hari Jumat pukul 14.00, koefisien perpindahan panas cangkang terendah adalah 2.762.553 btu/jam ft2 pada hari Selasa pukul 11.00. Perpindahan panas aktual tertinggi adalah 1.528.694.1 btu/jam hari Jumat jam 14.00, perpindahan panas aktual terendah adalah 713.159.522 btu/jam pada hari Kamis jam 8.00. Diketahui laju perpindahan kalor maksimum sebesar 1.797.918 btu/jam pada pukul 14.00, laju perpindahan kalor maksimum sebesar 790.348 btu/jam pada hari Kamis pukul 08.00. Diketahui efisiensi tertinggi sebesar 90,25% pada hari Kamis pukul 08.00. Dengan efisiensi rata-rata antara kisaran 86,29%. Gland Steam Condensor (GSC) is a heat exchanger it condenses steam from a turbine shaft seal. This used steam will heat condensate water from a condensate pump which is flowed across Gland Steam condensor. Because the heat is absorbed by condensate water, used steam from the shaft seal will condense and then flow to hotwell until it mixes with hotwell water.  From the results of the study the highest heat transfer coefficient on the tube is 80,491.93 btu/hr  on Wednesday at 2:00 p.m. It is known that the heat transfer coefficient on the lowest tube is 79,011.94  btu/hr on Monday at 4:00 p.m. The highest heat transfer coefficient on the shell is 5,294,695 btu/hr on Friday at 14:00, the lowest shell heat transfer coefficient is 2,762,553 btu/hr on Tuesdayat 11: 00. The highest actual heat transfer is 1,528,694.1 btu/hr on Friday at 2:00 p.m., the lowest actual heat transfer is 713,159,522 btu/hr on Thursday at 8:00. It is known that the maximum heat transfer rate is 1,797,918 btu/hr at 2:00 p.m., the maximum heat transfer rate is 790,348 btu/hr on Thursday at 8:00. It is known that the highest efficiency is 90.25% on Thursday at 8:00. With average efficiency between the range of 86.29%.

scholarly journals THERMAL PERFORMANCE EVALUATION OF ROOM AIR CONDITIONERS EVAPORATORS

2005 ◽  
Vol 4 (1) ◽  
Author(s):  
A. C. Piske ◽  
L. M. Moura ◽  
N. Mendes
Keyword(s):  
Heat Transfer ◽  
Performance Evaluation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Condensation Process ◽  
Physical Parameters ◽  
Overall Heat Transfer Coefficient

This work presents a thermal performance evaluation of a fin-and-tube evaporator - that is widely used in packaged air conditioning equipment - using a balanced calorimeter developed to simulate similar running conditions. The calorimeter determines the heat rate absorbed by the evaporator, providing qualitative analysis of performance for a given geometry. The calorimeter inside air is dried out due to the condensation process on the evaporator under test during the transient period. By this way it is possible to preview the humidity of the calorimeter domain and its influence with the instrumentation measurement. The heat transfer rate absorbed by the evaporator is obtained by a lumped approach using the energy conservation that is applied to the calorimeter domain, and is taken on the boundaries of the equipment. Physical parameters such as overall heat transfer coefficient for several types of fins can then be predicted in order to provide information for improving the energy-efficiency-oriented design. The uncertainties are estimated by the propagation of relative effects. Uncertainties are evaluated taking into account the systematic effects. Results are shown in terms of evaporator overall heat transfer coefficient and heat transfer rate as a function of inlet air temperature.

scholarly journals A Review on Heat Transfer Enhancement of Solar Air Heater Using Various Artificial Roughed Geometries

2021 ◽  
Vol 89 (1) ◽  
pp. 92-133
Author(s):  
Sudharani Panda ◽  
Rakesh Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heated Surface ◽  
Cost Effective ◽  
Solar Air Heater ◽  
Artificial Roughness ◽  
Air Heater

Solar air heater acts as one of the important components in utilization of solar energy. The air heater absorbs the irradiance and converts it into heat energy at the absorbing surface. The thermal energy is further use in heating flowing air through the duct. Solar air heaters are cost effective as well as simple in design. Solar air heater can be used in space heating, timber seasoning and agricultural drying. In spite of all these advantages the solar air heater has certain challenges such as the air has low heat transfer coefficient. The heat transfer rate from the heated absorber surface to the air is low. Hence in order to enhance the heat transfer coefficient the surface area either increases or the flow made to be turbulent. In order to do so the artificial roughened element must be incorporated on the heated surface. The use of artificial roughness is considered as an effective technique to enhance the heat transfer rate of fluid flowing through the duct of solar air heater. The heat transfer and friction characteristics of number of roughness geometries incorporated solar air heater have been investigated. In this paper an attempt has been made to review on element geometries used as artificial roughness in solar air heater in order to improve thermal and thermo hydraulic performance of solar air heater ducts.

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