Enhancement of Nusselt number by using Al2O3 and TiO2 Nanofluids in Heat Exchangers

2021 ◽  
Vol 47 ◽  
pp. 6515-6521
Author(s):  
Nitesh Singh Rajput ◽  
Dipesh Dilipbhai Shukla ◽  
Lav Ishan ◽  
Kanumalla Seshu Madhav
Keyword(s):  
Nusselt Number ◽  
Heat Exchangers ◽  
Tio2 Nanofluids

scholarly journals Heat transfer studies in compact heat exchanger using ZnO and TiO2 nanofluids in ethylene glycol/water

2018 ◽  
Vol 24 (4) ◽  
pp. 309-318
Author(s):  
Srinivasan Manikandan ◽  
Rajoo Baskar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Ethylene Glycol ◽  
Volume Fraction ◽  
Inlet Temperature ◽  
Percentage Increase ◽  
Cold Side ◽  
Volume Fractions ◽  
Experimental Values ◽  
Tio2 Nanofluids

This paper reports an experimental study on the heat transfer characteristics of a nanofluid consisting of ZnO/water/ethylene glycol (EG) and TiO2/water/ /ethylene glycol. In this study, the base fluids of ethylene glycol (EG):water (W) with volume fractions of 30:70, 40:60, and 50:50 were prepared, and 0.2 to 1.0 volume fractions of ZnO and TiO2 nanofluids were used as a cold side fluid. The prime objective of this study is to identify the effects of nanofluid concentration and three different hot fluid inlet temperatures viz., 55, 65 and 75?C C on the heat transfer enhancement of cold side fluid. The results are compared with base fluids and the percentage increase of the Nusselt number because of nanoparticle addition is noted both experimentally and theoretically. The results showed that at the hot fluid inlet temperature of 75?C, the increase in the Nusselt number is maximum with volume concentrations of 0.6 and 0.8% for ZnO and TiO2 nanofluids, respectively. The corresponding maximum Nusselt number enhancements are about 11.5 and 21.4%, respectively, for the base fluid volume fraction of 30:70 (EG:W). There is good agreement between the results calculated from experimental values and the correlation.

Experimental Investigation of Coil Curvature Effect on Heat Transfer and Pressure Drop Characteristics of Shell and Coil Heat Exchanger

2014 ◽  
Vol 7 (1) ◽  
Author(s):  
M. R. Salem ◽  
K. M. Elshazly ◽  
R. Y. Sakr ◽  
R. K. Ali
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Average Nusselt Number ◽  
Transfer Coefficients ◽  
Nusselt Numbers ◽  
Fanning Friction Factor ◽  
Coil Heat

The present work experimentally investigates the characteristics of convective heat transfer in horizontal shell and coil heat exchangers in addition to friction factor for fully developed flow through the helically coiled tube (HCT). The majority of previous studies were performed on HCTs with isothermal and isoflux boundary conditions or shell and coil heat exchangers with small ranges of HCT configurations and fluid operating conditions. Here, five heat exchangers of counter-flow configuration were constructed with different HCT-curvature ratios (δ) and tested at different mass flow rates and inlet temperatures of the two sides of the heat exchangers. Totally, 295 test runs were performed from which the HCT-side and shell-side heat transfer coefficients were calculated. Results showed that the average Nusselt numbers of the two sides of the heat exchangers and the overall heat transfer coefficients increased by increasing coil curvature ratio. The average increase in the average Nusselt number is of 160.3–80.6% for the HCT side and of 224.3–92.6% for the shell side when δ increases from 0.0392 to 0.1194 within the investigated ranges of different parameters. Also, for the same flow rate in both heat exchanger sides, the effect of coil pitch and number of turns with the same coil torsion and tube length is remarkable on shell average Nusselt number while it is insignificant on HCT-average Nusselt number. In addition, a significant increase of 33.2–7.7% is obtained in the HCT-Fanning friction factor (fc) when δ increases from 0.0392 to 0.1194. Correlations for the average Nusselt numbers for both heat exchanger sides and the HCT Fanning friction factor as a function of the investigated parameters are obtained.

scholarly journals Graphing Behaviour of Heat Transfer In Terms of Nusselt and Reynolds

2021 ◽  
Vol 6 (2) ◽  
pp. 41-52
Author(s):  
Mohd Rahimie Md Noor ◽  
Nur Syafiqah Hidayah Mohd Fauzi ◽  
Siti Nur Fadhilah Masrom ◽  
Mohd Azry Abdul Malek ◽  
Muhammad Firdaus Mustapha ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Volume Flow Rate ◽  
Convection Heat Transfer ◽  
Heat Transfer Process ◽  
Two Fluids ◽  
The Relationship

Heat exchangers are tools used to transfer thermal energy between two fluids (liquid or gas) by convection and conduction at different level of temperatures. Heat exchangers are the common equipment and employed in many different applications because of ability to withstand high temperatures and compactness. There are no intermixing or leakage occurred between two fluids during the heat transfer process as fluids are separated by walls of heat exchanger. The main objective of this project is to determine the heat exchanger effectiveness in heat transfer performance. This will be done by investigating the performance of five different angles of heat exchanger which are 150,300, 450, 600 and 750. The effectiveness of heat exchanger depends on the convection heat transfer coefficient of the fluid. Besides that, this project also aims to develop some parameters such as Nusselt number, Reynolds number and Prandtl number for evaluating the heat transfer. It is found that the Nusselt Number at angle of 150 is lower compared to angle of 750. Meanwhile, Reynolds number for angle 150 is higher than angle 750 which means that the type of flow produced by angle 150 is turbulent flow while for 750 angle is laminar flow. Hence, the overall result of this project proved that 150 is the best angle for heat exchanger in chimney because of higher velocity, higher volume flow rate, higher density of gas and higher LMTD. The relationship between Nusselt number and Reynolds number between different angles can be observed by plotting the graph using Maple Software.

scholarly journals Optimization of heat transfer at the surface of parabolic fins by genetic Algorithm

2017 ◽  
Vol 52 (4) ◽  
pp. 325-330
Author(s):  
A Gholami ◽  
H Mehrjou
Keyword(s):  
Heat Transfer ◽  
Genetic Algorithm ◽  
Nusselt Number ◽  
Hydraulic Resistance ◽  
Economic Efficiency ◽  
Heat Exchangers ◽  
Air Conditioning ◽  
Energy Exchanges ◽  
Extended Surfaces ◽  
Library Method

Thermal fins are extended surfaces like longitudinal, radial, and cylindrical fins. They are used for the improvement of heat transfer between an object and fluid. Fins can be applied in many processes of objects cooling such as electrical appliances, many types of engines, transformers, chemical industry, air conditioning, heat exchangers and the industries of energy exchanges. This matter is one of the main results of paying attention to this issue. Therefore, this study examined the optimization of fin heat transfer by using a genetic algorithm and consideration of Nusselt number and hydraulic resistance as the objective function. In this paper, we investigated the optimization of the fin to maximize the heat transfer and also to minimize the hydraulic resistance. The results of this study can be effective in term of technical and economic efficiency in the industry of fin transformer. The stimulation and library method has been used to collect data. The results indicated that if the hydraulic resistance was limited to a specific value, using wavy fins will not improve the device heat.Bangladesh J. Sci. Ind. Res. 52(4), 325-330, 2017

Transient Natural Convection Heat Transfer Correlations for Tube Bundles Immersed in a Thermal Storage

2005 ◽  
Vol 129 (2) ◽  
pp. 210-214 ◽  
Author(s):  
Yan Su ◽  
Jane H. Davidson
Keyword(s):  
Nusselt Number ◽  
Natural Convection ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Tube Bundle ◽  
Single Tube ◽  
Tube Heat Exchanger ◽  
Storage Vessel ◽  
Transient Natural Convection ◽  
Nusselt Numbers

A scale analysis of the transient discharge of a fully mixed thermal storage vessel with an immersed single-tube heat exchanger is extended to provide a generalized expression for the transient natural convection Nusselt number for heat exchangers comprising many tubes. The transient Nusselt number is expressed in terms of the Rayleigh number at the initiation of the discharge (or charge) process and easily measured geometric parameters. Nusselt numbers measured for a 240-tube heat exchanger immersed in a fully mixed 126L storage vessel are well correlated in the proposed form. The applicability of the approach to thermally stratified storage fluids is evaluated for both a single-tube and the 240-tube bundle. For heat exchangers of practical size for solar systems, for example the 240-tube bundle, buoyancy driven flow within the storage is sufficient to mix an initially stratified fluid. In this case, Nusselt numbers during the discharge process are predicted accurately by the proposed transient formulation. However, if the storage fluid remains stratified during discharge, as is the case for an initially stratified vessel with a single-tube heat exchanger, the transient formulation is not recommended.

The Correlation of Heat Transfer Coefficients for the Laminar Natural Convection in a Circular Finned-Tube Heat Exchanger

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Hie Chan Kang ◽  
Se-Myong Chang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Natural Convection ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Finned Tube ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Laminar Natural Convection

This study proposes an empirical correlation for laminar natural convection applicable to external circular finned-tube heat exchangers with wide range of configuration parameters. The transient temperature response of the heat exchangers was used to obtain the heat transfer coefficient, and the experimental data with their characteristic lengths are discussed. The data lie in the range from 1 to 1000 for Rayleigh numbers based on the fin spacing: the ratio of fin height to tube diameter ranges from 0.1 to 0.9, and the ratio of fin pitch to height ranges from 0.13 to 2.6. Sixteen sets of finned-tube electroplated with nickel–chrome were tested. The convective heat transfer coefficients on the heat exchangers were measured by elimination of the thermal radiation effect from the heat exchanger surfaces. The Nusselt number was correlated with a newly suggested composite curve formula, which converges to the quarter power of the Rayleigh number for a single cylinder case. The proposed characteristic length for the Rayleigh number is the fin pitch while that for the Nusselt number is mean flow length, defined as half the perimeter of the mean radial position inside the flow region bounded by the tube surface and two adjacent fins. The flow is regarded as laminar, which covers heat exchangers from a single horizontal cylinder to infinite parallel disks. Consequently, the result of curve fitting for the experimental data shows the reasonable physical interpretation as well as the good quantitative agreement with the correction factors.

Generalized Models for Laminar Developing Flows in Heat Sinks and Heat Exchangers

2011 ◽  
Author(s):  
Y. S. Muzychka
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchangers ◽  
Heat Sinks ◽  
Length Scale ◽  
Square Root ◽  
Sectional Area ◽  
Cross Sectional

Recent models for laminar friction and heat transfer in non-circular ducts and channels are reviewed. Models for both hydrodynamically and thermally developing flows are presented. These models are based on the superposition of asymptotic characteristics for short and long ducts. The non-dimensional mean wall shear stress (or fRe) and non-dimensional heat transfer coefficient (or Nusselt number) are shown to be only functions the dimensionless hydrodynamic or thermal duct length, respectively, and the duct aspect ratio. This is achieved by means of using a new transversal length scale, the square root of cross-sectional area, rather than the hydraulic diameter. Additional definitions more appropriate to single fluid devices such as heat sinks are also discussed.

Heat Transfer in Thin, Compact Heat Exchangers With Circular, Rectangular, or Pin-Fin Flow Passages

1992 ◽  
Vol 114 (2) ◽  
pp. 373-382 ◽  
Author(s):  
D. A. Olson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Rectangular Channel ◽  
Fluid Temperature ◽  
Compact Heat Exchangers ◽  
Pin Fin

We have measured heat transfer and pressure drop of three thin, compact heat exchangers in helium gas at 3.5 MPa and higher, with Reynolds numbers of 450 to 36,000. The flow geometries for the three heat exchanger specimens were: circular tube, rectangular channel, and staggered pin fin with tapered pins. The specimens were heated radiatively at heat fluxes up to 77 W/cm2. Correlations were developed for the isothermal friction factor as a function of Reynolds number, and for the Nusselt number as a function of Reynolds number and the ratio of wall temperature to fluid temperature. The specimen with the pin fin internal geometry had significantly better heat transfer than the other specimens, but it also had higher pressure drop. For certain conditions of helium flow and heating, the temperature more than doubled from the inlet to the outlet of the specimens, producing large changes in gas velocity, density, viscosity, and thermal conductivity. These changes in properties did not affect the correlations for friction factor and Nusselt number in turbulent flow.

scholarly journals Comparative study of the thermal performance of four different parallel flow shell and tube heat exchangers with different performance indicators

Open Physics ◽  
2020 ◽  
Vol 18 (1) ◽  
pp. 1121-1135
Author(s):  
Chulin Yu ◽  
Haiqing Zhang ◽  
Youqiang Wang ◽  
Jin Wang ◽  
Bingjun Gao ◽  
...  
Keyword(s):  
Nusselt Number ◽  
Comparative Study ◽  
Friction Factor ◽  
Entropy Generation ◽  
Performance Indicators ◽  
Heat Exchangers ◽  
Parallel Flow ◽  
Turbulent Regime ◽  
Entransy Dissipation ◽  
Shell And Tube

Abstract Round rod baffle (RRB), plain plate baffle (PPB), wavy-shaped plate baffle (WSB) and polygonal-shaped plate baffle (PSB) are four commonly used baffles in parallel flow shell and tube heat exchangers (STHXs). Comparative study of these four different baffles are numerically carried out using different performance indicators including Nusselt number, friction factor, performance evaluation criterion, entropy generation ratio, and entransy dissipation ratio for flow in full turbulent regime. Heat transfer mechanism has also been discussed. Correlations for Nusselt number and friction factor are fitted and the cost estimation using Hall’s method is compared. It is found that the Nusselt number of STHX-PPB, STHX-WSB, and STHX-PSB increased by 20.9%, 15.2%, and 23.9% averagely compared with STHX-RRB, respectively. The friction factor can be increased on average by 142.0%, 154.5%, and 242.4%, respectively. However, the overall performance of them is only 90.1%, 84.4%, and 82.3% that of STHX-RRB, respectively. The sequence of entropy generation and entransy dissipation is STHX-RRB > STHX-WSB > STHX-PPB > STHX-PSB. The inlet Re and baffle distance have significant effects on different performance indicators while the baffle width does not. Finally, the results show that the STHX-PSB can reduce the total cost as it has better ability on heat enhancement.

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