scholarly journals Numerical simulation of heat transfer augmentation in fin-and-tube heat exchanger with various number of rows of concave rectangular winglet vortex generator

2018 ◽  
Vol 159 ◽  
pp. 02012 ◽  
Author(s):  
Syaiful ◽  
Imam Syarifudin ◽  
Maria F. Soetanto ◽  
Myung-whan Bae
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Convection Heat Transfer ◽  
Vortex Generator ◽  
Convection Coefficient ◽  
Convection Heat ◽  
Convection Heat Transfer Coefficient ◽  
Tube Heat Exchanger

The passive method by using a vortex generator (VG) is an effective method for the improvement of convective heat transfer. This study is focused on usage of concave rectangular winglet vortex generator (CRW VG) for improving convective heat transfer in a fin-and-tube heat exchanger using numerical simulation. Concave rectangular winglet pairs (CRWP) and rectangular winglet pairs (RWP) VGs were mounted inside the gap between fins (gas side) with variations of the number of VG pairs of rows. Inlet air velocity variations expressed by the Reynolds numbers were ranged from 364 to 689. Augmentation of heat transfer is indicated by the ratio value of heat transfer convection coefficient between cases using VG and that without using VG (baseline). The results show that the convection heat transfer coefficient for cases using CRWP VG is higher than that using RWP VG. Convection heat transfer coefficient increases up to 102% by mounting CRWP VG at Re = 364. However, the increase in convection coefficient is accompanied by a rise in pressure drop to 216.8%.

scholarly journals Experimental and Theoretical Investigation of the Natural Convection Heat Transfer Coefficient in Phase Change Material (PCM) Based Fin-and-Tube Heat Exchanger

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 716
Author(s):  
Saulius Pakalka ◽  
Kęstutis Valančius ◽  
Giedrė Streckienė
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Energy Storage ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Convection Heat Transfer Coefficient

Latent heat thermal energy storage systems allow storing large amounts of energy in relatively small volumes. Phase change materials (PCMs) are used as a latent heat storage medium. However, low thermal conductivity of most PCMs results in long melting (charging) and solidification (discharging) processes. This study focuses on the PCM melting process in a fin-and-tube type copper heat exchanger. The aim of this study is to define analytically natural convection heat transfer coefficient and compare the results with experimental data. The study shows how the local heat transfer coefficient changes in different areas of the heat exchanger and how it is affected by the choice of characteristic length and boundary conditions. It has been determined that applying the calculation method of the natural convection occurring in the channel leads to results that are closer to the experiment. Using this method, the average values of the heat transfer coefficient (have) during the entire charging process was obtained 68 W/m2K, compared to the experimental result have = 61 W/m2K. This is beneficial in the predesign stage of PCM-based thermal energy storage units.

scholarly journals Effect of perforated concave delta winglet vortex generators on heat transfer augmentation of fluid flow inside a rectangular channel: An experimental study

2018 ◽  
Vol 204 ◽  
pp. 04015
Author(s):  
Syaiful ◽  
MSK Tony SU ◽  
Nazaruddin Sinaga ◽  
Retno Wulandari ◽  
Myung-whan Bae
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Convection Heat Transfer ◽  
Vortex Generator ◽  
Longitudinal Vortex ◽  
Convection Heat ◽  
Convection Heat Transfer Coefficient ◽  
Delta Winglet

Compact heat exchanger with gas as a heat exchange medium is widely used in power plants, automotive, air conditioning, and others. However, the gas has a low thermal conductivity resulting in high thermal resistance causing a low rate of heat transfer. Therefore an improvement to the convection heat transfer coefficient is necessary. One way to enhance the convection heat transfer coefficient is to use a longitudinal vortex generator. However, the increase in convection heat transfer coefficient is followed by an increase in pressure drop. Therefore, this work aims to improve the convection heat transfer coefficient with a low pressure drop. To achieve this goal, experiments were carried out by perforating a longitudinal vortex generator with a diameter of 5 mm with variations in holes number one, two and three. Two types of longitudinal vortex generators are compared. The experimental results show that the convection heat transfer coefficient for the case of perforated concave delta winglet vortex generator is only decreased by 1% from that without a hole, while the pressure drop is decreased by 11.6%.

Estimation of the convection heat transfer coefficient of coolant within the grinding zone

2003 ◽  
Vol 217 (3) ◽  
pp. 397-407 ◽  
Author(s):  
T Jin ◽  
D J Stephenson ◽  
W B Rowe
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Film Thickness ◽  
Convection Heat Transfer ◽  
Wheel Speed ◽  
Convection Coefficient ◽  
Convection Heat ◽  
Convection Heat Transfer Coefficient ◽  
Creep Feed ◽  
Fluid Film Thickness

The convection heat transfer coefficient of the coolant within the grinding zone has been estimated using hydrodynamic and thermal modelling. The convection coefficient within the grinding zone can be very high, much higher than the values previously reported. The value is determined by the grinding wheel speed and the fluid film thickness within the contact zone. The film thickness in turn can be determined by wheel speed, porosity, grain size, coolant type and flowrate, nozzle size, etc. For deep grinding conditions [creep feed and high-efficiency deep grinding (HEDG)], the upper bound value of fluid film thickness can be easily achieved by a high coolant supply pressure and flowrate. Predicted values of the convection coefficient from hydrodynamic and thermal modelling show good agreement with experimental estimations obtained by matching measured and theoretical grinding temperatures for a wide range of grinding regimes when using a water-based grinding fluid. This includes HEDG and creep feed grinding for large contact lengths and conventional shallow cut grinding for short contact lengths.

Thermal Response Characteristics of Flat Plate Heated by High Temperature and High Speed Flow

2013 ◽  
Vol 448-453 ◽  
pp. 3316-3319
Author(s):  
Chuang Sun ◽  
Yang Zhao ◽  
De Fu Li ◽  
Qing Ai ◽  
Xin Lin Xia
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flat Plate ◽  
High Speed ◽  
Convection Heat Transfer ◽  
Thermal Response ◽  
Convection Heat ◽  
Convection Heat Transfer Coefficient

According to the view of heat transfer, the process of the fluid flow with high temperature and high speed over a flat plate may be considered as the heat transfer process within a compressible thermal boundary layer. Based on the numerical results of thermal isolation assumption, combining the temperature comparison with modification method, a coupled method of convection heat transfer coefficient with temperature field of the plate is established, and the characteristics of the thermal response for the flat plate is dominated. Take some ribbed plates as instances, the convection heat transfer coefficient and temperature field of the plate are simulated through the provided coupled method. The results show that, not only the position and materials of the plate influence the convection heat transfer coefficient, but also the time.

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