Pressure Drop and Heat Transfer Characteristics of MWCNT/Heat Transfer Oil Nanofluid Flow inside Microfinned Helical Tubes with Constant Wall Temperature

2012 ◽  
Vol 622-623 ◽  
pp. 796-800 ◽  
Author(s):  
M.H. Kazemi ◽  
M.A. Akhavan-Behabadi ◽  
M. Fakoor Pakdaman
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Base Fluid ◽  
Weight Fraction ◽  
Constant Wall Temperature ◽  
Heat Transfer Augmentation ◽  
Helical Tube ◽  
Helical Tubes

Experiments are performed to investigate the single-phase flow heat transfer augmentation of MWCNT/HT-B oil in both smooth and microfinned helical tubes with constant wall temperature. The tests in laminar regime were carried out in helical tubes with three curvature ratios of 2R/d=25, 30 and 35. Flow Reynolds number varied from 170 to 1800 resulting in laminar flow regime. The effect of some parameters such as the nanoparticles concentration, the dimensionless curvature radius (2R/d) and the Reynolds number on heat transfer was investigated for the laminar flow regime. The weight fraction of nanoparticles in base fluid was less than 0.4%. within the applied range of Reynolds number; results indicated that for smooth helical tube the addition of nanoparticles to the base fluid enhanced heat transfer remarkably. However, compared to the smooth helical tube, the average heat transfer augmentation ratio due to nanoparticle addition for finned tube was small, about 17%. Also, by increasing the weight fraction of nanoparticles in microfinned helical tubes, no substantial changes were observed in the rate of heat transfer enhancement. For the pressure drop, the results show that the pressure drop of nanofluids was slightly higher than the base fluid and increase as the volume concentrations go up.

The Effect of Twisted-Tape Width on Heat Transfer and Pressure Drop for Fully Developed Laminar Flow

1996 ◽  
Vol 118 (3) ◽  
pp. 584-589 ◽  
Author(s):  
W. M. Chakroun ◽  
S. F. Al-Fahed
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Friction Factor ◽  
Twisted Tape ◽  
Constant Wall Temperature ◽  
Low Reynolds Number Flows ◽  
Temperature Boundary ◽  
Series Of Experiments

A series of experiments was conducted to study the effect of twisted-tape width on the heat transfer and pressure drop with laminar flow in tubes. Data for three twisted-tape wavelengths, each with five different widths, have been collected with constant wall temperature boundary condition. Correlations for the friction factor and Nusselt number are also available. The correlations predict the experimental data to within 10 to 15 percent for the heat transfer and friction factor, respectively. The presence of the twisted tape has caused the friction factor to increase by a factor of 3 to 7 depending on Reynolds number and the twisted-tape geometry. Heat transfer results have shown an increase of 1.5 to 3 times that of plain tubes depending on the flow conditions and the twisted-tape geometry. The width shows no effect on friction factor and heat transfer in the low range of Reynolds number but has a more pronounced effect on heat transfer at the higher range of Reynolds number. It is recommended to use loose-fit tapes for low Reynolds number flows instead of tight-fit in the design of heat exchangers because they are easier to install and remove for cleaning purposes.

scholarly journals The Effect of Twisted Tape Width on Heat Transfer and Pressure Drop for Fully Developed Laminar Flow

1995 ◽  
Author(s):  
Walid M. Chakroun ◽  
Sami F. Al-Fahed
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Friction Factor ◽  
Twisted Tape ◽  
Constant Wall Temperature ◽  
Low Reynolds Number Flows ◽  
Temperature Boundary ◽  
Series Of Experiments

A series of experiments was conducted to study the effect of twisted-tape width on the heat transfer and pressure drop with laminar flow in tubes. Data for three twisted-tape wave lengths each with five different widths have been collected with constant wall temperature boundary condition. Correlations for the friction factor and Nusselt number are also available. The correlations predict the experimental data to within 10 % to 15 % for the heat transfer and friction factor, respectively. The presence of the twisted tape has caused the friction factor to increase by a factor of 3 to 7 depending on Reynolds number and the twisted-tape geometry. Heat-transfer results have shown an increase of 1.5 to 3 times that of plain tubes depending on the flow conditions and the twisted-tape geometry. The width shows no effect on friction factor and heat transfer in the low range of Reynolds number but have a more pronounced effect on heat transfer at the higher range of Reynolds number. It is recommended to use a loose-fit tapes for low Reynolds number flows instead of tight-fit in the design of heat exchangers because they are easier to install and remove for cleaning purposes.

Experimental Investigation on Heat Transfer and Pressure Drop of CNT-Base Oil Nano-Fluid Flow in Rectangular Channels under Constant Wall Temperature

2012 ◽  
Vol 622-623 ◽  
pp. 806-810
Author(s):  
M.R. Naghavi ◽  
M.A. Akhavan-Behabadi ◽  
M. Fakoor Pakdaman
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Base Fluid ◽  
Constant Wall Temperature ◽  
Base Oil ◽  
Nano Fluid ◽  
Rectangular Channels

An experimental investigation has been carried out to study the heat transfer and pressure drop characteristics of MWCNT-Base oil nano-fluid flow inside horizontal rectangular channels under constant wall temperature. The temperature of the tube wall was kept constant at around 95 °C to have isothermal boundary condition. The required data were acquired for laminar fully developed flow inside round and rectangular channels. The effect of different parameters such as mass velocity, aspect ratio of rectangular channels and nano-particles concentration on heat transfer coefficient and pressure drop of the flow is studied. Observations show that the heat transfer performance is improved as the aspect ratio is increased. Also, increasing the aspect ratio will result in the pressure drop increasing. In addition, the heat transfer coefficient as well as pressure drop is increased by using nano-fluid instead of base fluid. Furthermore, the performance evaluation of the two enhanced heat transfer techniques studied in this investigation showed that applying rectangular channels instead of the round tube is a more effective way to enhance the convective heat transfer compared to the second method which is using nano-fluids instead of the base fluid.

Heat Transfer Augmentation in 3D Inner Finned Helical Tube

Volume 3 ◽  
2004 ◽  
Author(s):  
Longjian Li ◽  
Wenzhi Cui ◽  
Quan Liao ◽  
Mingdao Xin ◽  
Tien-Chien Jen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Boiling Heat Transfer ◽  
Flow Resistance ◽  
Single Phase ◽  
Flow Boiling ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Helical Tube ◽  
Helical Tubes

Experiments were performed to investigate the performance enhancement of single-phase flow and boiling heat transfer in the 3D inner finned helical tubes. The tests for single-phase flow and heat transfer were carried out in the helical tubes with a curvature of 0.0663 and a length of 1.15m, the range of the Reynolds number examined varies from 1000 to 8500. In comparison to the smooth helical tube, the experimental results of two finned helical tubes with different inner fin geometry showed that the heat transfer and flow resistance in the 3D inner finned helical tube gains greater augmentation. Within the measured range of Reynolds number, the average augmentation ratio of heat transfer of the two finned tubes are 71% and 103%, compared with the smooth helical tube, and 90% and 140% for flow resistance, respectively. The tests for flow boiling heat transfer was carried out in the 3D inner finned helical tube with a curvature of 0.0605 and a length of 0.668m. Compared with that in the smooth helical tube, the boiling heat transfer coefficient in the 3D inner finned helical tube is increased by 40%∼120% under varied mass flow rate and wall heat flux conditions, meanwhile, the flow resistance coefficient increased by 18%∼119%.

Thermal and Hydrodynamic Performance of Aqueous CuO and Al2O3 Nanofluids in an Annular Coiled Tube Under Constant Wall Temperature and Laminar Flow Conditions

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Wael I. A. Aly
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Laminar Flow ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Base Fluid ◽  
Hydrodynamic Performance ◽  
Constant Wall Temperature ◽  
Coiled Tube ◽  
Tube Heat Exchanger

Laminar flow and heat transfer behaviors of two different metal oxide, Al2O3 (36 nm) and CuO (29 nm), nanofluids flowing through an annular coiled tube heat exchanger (ACTHE) with constant wall temperature boundary condition have been numerically studied to evaluate their superiority over the base fluid (water). Simulations covered a range of nanoparticles volume concentrations of 1.0–6.0% and mass flow rates from 0.025 to 0.125 kg/s. Numerical results indicated that a considerable heat transfer enhancement is achieved by both nanofluids. Results at the same Reynolds number for the pressure drop and heat transfer coefficient show an increase with increasing particle volumetric concentration. The maximum enhancements in heat transfer coefficient were 44.8% and 18.9% for CuO/water and Al2O3/water, respectively. On the other hand, the pressure loss was seven times in comparison to water for CuO/water and about two times for Al2O3/water nanofluid. Also, comparing to the base fluid, nanofluids at low concentrations (up to 3%) can provide the same heat transfer amount at lower pumping power. The overall performance of the enhanced heat transfer technique utilized has been evaluated using a thermohydrodynamic performance index which indicated that Al2O3/water nanofluid is a better choice than CuO/water nanofluid. Moreover, conventional correlations for helical circular tubes for predicting friction factor and average heat transfer in laminar flow regime such as the correlations of Mori and Nakayam and Manlapaz and Churcill, respectively, are also valid for water and the tested nanofluids with small nanoparticle loading in the ACTHE.

An Experimental Investigation of Wavy and Straight Minichannel Heat Sinks Using Water and Nanofluids

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
A. Dominic ◽  
J. Sarangan ◽  
S. Suresh ◽  
V. S. Devah Dhanush
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Heat Transfer Performance ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Transfer Performance ◽  
Temperature Distributions

An experimental investigation on the heat transfer performance and pressure drop characteristics of thermally developing and hydrodynamically developed laminar flow of de-ionized (DI) water and 0.1%, 0.5%, and 0.8% concentrations of Al2O3/water nanofluid in wavy and straight minichannels was conducted. Reynolds number was varied from 700 to 1900 and two different heat fluxes of 45 kW/m2 and 65 kW/m2 were applied. The performance factor (PF) of water in wavy minichannels over their straight counterparts was higher than the nanofluids. Temperature distributions and general correlations of these minichannels are also presented.

scholarly journals Experimental Investigation of the Heat Transfer and Pressure Drop inside Tubes and the Shell of a Minichannel Shell and Tube Type Heat Exchanger

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8563
Author(s):  
Mateusz Prończuk ◽  
Anna Krzanowska
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Inner Diameter ◽  
Shell And Tube

This paper presents an experimental study on a shell and tube mini heat exchanger (STMHE). The STMHE consisted of seven tubes in a triangular arrangement, with an 0.8 mm inner diameter and 1.0 mm outer diameter. The heat exchanger shell had an inner diameter of 11 mm, and the heat exchanger had no baffles. For the adopted operating conditions, the Reynolds number on the tube side varied in the range of 300–3000, and 2000–12,000 on the shell side. The aim of this study was to determine pressure drop values during fluid flow and Nusselt number correlations for the heat transfer. A new method based on optimisation was used to derive the equations for calculating the heat transfer coefficients. It allowed the determine of the correlation equations for the heat transfer coefficients simultaneously for both sides of the heat exchanger. The obtained correlations yielded overall heat transfer coefficient values that, in most cases, did not differ by more than from those determined experimentally. The experimentally determined critical Reynolds number value for the flow inside the tubes was equal to . The Darcy friction factors correlated well with the classical laminar flow correlation and with the Blasius correlation for turbulent flow. The derived correlations for the Nusselt number were best aligned with the Sieder–Tate, Gnielinski, and Kozioł correlations for tube side laminar flow, turbulent flow, and shell flow, respectively. Good agreement between the results obtained using the experimentally derived correlations and the correlations available in the literature confirms the effectiveness of the used optimisation–based method.

scholarly journals Heat Transfer in Hairpin Heat Exchanger using Magnetite/Water Nanofluid

2019 ◽  
Vol 8 (4) ◽  
pp. 7163-7166
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Magnetite Nanoparticles ◽  
Pure Water ◽  
Number Range ◽  
Heat Transfer Augmentation

The present work deals with heat transfer augmentation in a Hair-Pin heat exchanger using magnetite/water nanofluid at volume concentrations of 0.004%, 0.006% and 0.008% under turbulent flow, the effect of different concentration of magnetite nanoparticles are added in pure water as basefluid on heat transfer coefficient and pressure drop in a hair-pin heat exchanger for counteract flow arrangement are investigated. The magnetite/water nanofluid is flowing through the inner tube and Reynolds number considered is in the range of 16000 to 30000. The results showed that there is 25-33% enhancement in heat transfer coefficient at 0.008% to the water at Reynolds number range of 16000 to 30000.

MODELING OF A HELICALLY COILED HFC134a EVAPORATOR

2014 ◽  
Vol 22 (03) ◽  
pp. 1450016 ◽  
Author(s):  
J. K. DABAS ◽  
SUDHIR KUMAR ◽  
A. K. DODEJA ◽  
K. S. KASANA
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Design Optimization ◽  
Performance Optimization ◽  
Computer Simulation Model ◽  
Analysis And Design ◽  
Hfc 134A ◽  
Helical Tube ◽  
Performance Analysis And Design ◽  
Helical Tubes

A computer simulation model has been developed for the performance analysis and design optimization of a helical coil and cylindrical shell type evaporator working with HFC-134a by using the appropriate empirical correlations of heat transfer coefficient and pressure drop in the helical tubes as available in the literature. This model is based on a numerical method of cell discretization of shell side and tube side of the evaporator. The local values of variables are calculated and the mass, momentum and energy balance is applied to each small cell. The whole sequential and iterative procedure to satisfy the boundary conditions has been transformed in the computer codes. The model has been validated by comparing with the actual results of an experimental study which is also a part of this work. A detailed analysis of the effects of varying input parameters of both fluids on the performance of evaporator was carried out with the help of this model. It also gives the optimum values of mass velocity of refrigerant and the helical tube diameter against the available flow conditions of refrigerant and of external fluid and the required degree of vapor superheat at the exit of evaporator. Thus it provides an easy solution in both the cases of either the performance optimization of an existing evaporator or the design optimization of a new evaporator. The inherent errors in the outcome of correlations for heat transfer, pressure drop and refrigerant properties are the limitations of this model.

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