Heat transfer enhancement Research Papers (original) (raw)

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- Heat Transfer, Heat transfer enhancement, Vortex Generators
- by Lidija Siller
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- Engineering, Mechanical Engineering, Chemical Engineering, Convection
- by Marc Medrano
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- Mechanical Engineering, Heat Transfer, Natural Convection, Heat transfer coefficient

- by Obaid Fadhil
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- Engineering, Heat Transfer, Heat transfer enhancement, Flat-plate Solar Collectors
- by Oronzio Manca
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- Applied Mathematics, Heat Transfer, Numerical Analysis, Heat transfer coefficient
- by Ephraim Sparrow
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- Engineering, Mechanical Engineering, Chemical Engineering, Aerospace Engineering
- by ALIREZA HOBBI
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- Engineering, Materials Science, Heat Transfer, Performance

This paper evaluated the performance of an envelope enhancement (EE) algorithm subjectively by children with auditory processing disorder (APD), and objectively through computational models. Speech intelligibility data was collected from children with APD, for unprocessed and envelope- enhanced speech in the presence of stationary and non-stationary background noise at different signal to noise ratios (SNRs), both with and without noise reduction (NR) algorithms as a front-end to the EE algorithm. Furthermore, intrusive and non-intrusive objective speech intelligibility metrics were derived to predict the perceptual impact of this EE algorithm. Subjective data for stationary noise conditions revealed that the combination of NR and EE algorithms significantly improved the speech intelligibility scores at poor SNRs. In contrast, the same combination was ineffective in improving speech intelligibility in non-stationary noise conditions. Taken together, subjective results suggest that exaggerating the envelope cues improves speech identification scores for children with APD. However, the benefit obtained varies depending upon the type and level of the background noise. Both intrusive and non-intrusive objective speech intelligibility estimators exhibited good correlation with the subjective data, with the intrusive metric demonstrating better generalization capabilities. Implications of these results for hearing aid applications for children with APD is discussed.

A combination of heat transfer augmentation techniques is highly necessary to enhance the performance of Thermal Energy Storage (TES) systems employed in a wide range of applications. The major issue is that many of the Phase Change Materials (PCMs) possess low thermal conductivity (k ≤ 0.2 W/m K), resulting in an inefficient melting process. Triplex Tube Heat Exchanger (TTHX) based TES system is both numerically and experimentally studied using Paraffin (RT82) with Alumina (Al 2 O 3) nanoparticles that has a charging temperature in the range of 78.15-82.15 ∘ C. The experimental findings indicate that the Paraffin is not completely melted within the required time of four hours for the inside heating method at 97 ∘ C. The Paraffin is successfully melted for both sides heating at 90 ∘ C in lesser time and average temperature than the outside heating. With different charging temperatures, the Paraffin melting was consumed a short time for the non steady state at the mass flow rate of 29.4 kg/min, compared with the 16.2 and 37.5 kg/min for inner and outer tubes. Other outcomes were that with the fins-nanoparticle combination, an improved performance for melting the Paraffin, compared with those that occurred without nanoparticle. Furthermore, in the numerical study, compared with the pure Paraffin case, the melting time was minimized for TTHX with longitudinal fins (12%) and TTHX with triangular fins (22%) for the PCM having 10% nanoparticle, respectively. Close agreement is found between the numerical and experimental findings.

- by Hakeem Niyas
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- Heat Exchanger, Phase Change Materials, Heat transfer enhancement

3-D numerical simulations are performed for heat transfer and fluid flow characteristics of the tubes fitted with twisted-tape inserts. The principle of heat transfer enhancement in the core flow of tube has been proposed to improve the temperature uniformity and reduce flow resistance. Twisted inserts widths w = 12 mm have been investigated for different inlet volume-flow rates. The simulation results show that the average overall heat transfer coefficients in circular plain tubes are enhanced with twisted tape of widths by as much as 100% at a constant tube-side temperature and the friction factor are enhanced. The twisted-tape-induced swirl flow heat transfer due to exponentially increasing heat inputs with various exponential periods and twisted-tape-induced pressure
drop were systematically measured.

- by Anirban Roy and +1
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- Heat Transfer, Heat transfer enhancement, Heat Transfer Fluid Mechanics CFD, Twisted Tape
- by Durai Darin
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- Physics, Nanotechnology, Nanofluids, Nanoscience
- by Ravikanth Vajjha
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- Mechanical Engineering, Civil Engineering, Applied Mathematics, Convection
- by Mostafa Awad
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- Heat transfer coefficient, Heat Flux, Steady state, Heat transfer enhancement

This work presents an experimental and numerical study to investigate the heat transfer enhancement of flat plat collector (FPC) using three types of twisted tapes (single twisted tape (ST), double twisted tape (DT) and mixed twisted tape (SDT)) which are compared with plain tube with twist ratios (TR=2). The study are considered under fully developed turbulent flow with solar radiation heat gain are changing with time. The designed FPC consists of four pipes with 1.25cm in diameter and 1mm thick are placed above the plate to act as a heat removal fluid passage ways. The system consists of two collectors, each one has (40cm x 160cm x 15cm) and connected to two tanks, each one is 20 liters. The amount of heat gain from solar radiation depends on many effective parameters are used; type of twisted tape are using, type of collectors plate metal (aluminum or copper), value of Reynolds number, amount of sun rays available at the site, number of glass covers and orientation of the collectors with respect to the south direction. From the experimental results was obtained which are demonstrate that the DT are more efficient than ST and SDT, since the heat transfer enhancement which increases the output temperature of the working fluid. The experimental study also show that the temperature of outlet water from mixed twisted tape collector is higher than the other type of plain tube collector by 10°C. The outlet water temperature of collector made from cupper is more than the collector made of aluminum about 6°C. The outlet water temperature from collector which has Reynolds number of 5000 less than 5°C for copper collector and less than 4°C for aluminum collector from the other with Re number is 10000. Increasing of the temperature of the outlet water in the collector which has two glass cover is about 4°C from one glass cover. The numerical analysis was based on finite volume numerical techniques to solve the governing partial differential equations in three dimensions, using ANSYS FLUENT commercial CFD software, to study the effect of Reynolds number and twisted tape types on the heat transfer enhancement and friction factor. The comparison between the experimental and numerical results shows a high agreement, and the maximum error was 8.3% occurred with mixed twisted tape.

The present review is organized in different arrangement of finned tube bundles placed on inline arrangement
and staggered arrangement in cross flow. A large number of experimental and numerical works had been
performed for enhancement of air-side heat transfer. A brief discussion is done on the effect of local heat
transfer behaviour of circular finned tube and analysis of geometric and flow parameters included in this
paper. Different parameters like fin height, fin spacing, fin thickness, tube diameter, tube spacing, effects of
row and arrangement of tube bundles affect directly on the performance of solid circular finned tube. All
these parameters are briefly discussed in this paper. Discussions on some important points which affect the
performance of tube bundles (i.e. inline and staggered arrangement) from various authors and their problem
and related issues are presented in this paper. The flow profiles and the related heat transfer characteristics in
the complex geometries are still needed to be verified.
Keywords: Heat Transfer Augmentation, inline arrangement, staggered arrangement, cross flow

- by A. Trifirò and +1
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- Food Engineering, Heat Transfer, Heat Treatment, Heat Exchanger
- by Henk Metselaar
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- Engineering, Heat and Mass Transfer, Mathematical Sciences, Physical sciences

New experimental data are reported for water based nanofluids to enhance the heat transfer performance
of a car radiator. ZnO nanoparticles have been added into base fluid in different volumetric
concentrations (0.01%, 0.08%, 0.2% and 0.3%). The effect of these volumetric concentrations on the heat
transfer performance for car radiator is determined experimentally. Fluid flow rate has been varied in a
range of 7e11 LPM (liter per minute) (corresponding Reynolds number range was 17,500e27,600).
Nanofluids showed heat transfer enhancement compared to the base fluid for all concentrations tested.
The best heat transfer enhancement up to 46% was found compared to base fluid at 0.2% volumetric
concentration. A further increase in volumetric concentration to 0.3% has shown a decrease in heat
transfer enhancement compared to 0.2% volumetric concentration. Fluid inlet temperature was kept in a
range of 45e55 C. An increase in fluid inlet temperature from 45 C to 55 C showed increase in heat
transfer rate up to 4%.

- by Hafiz Muhammad Ali
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- Heat Transfer, Heat and Mass Transfer, Nanofluids, Nanofluid (Heat Transfer)
- by Oronzio Manca
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- Heat Transfer, Nanofluids, Nanoscience, Heat transfer enhancement

The continuous increase in the level of greenhouse gas emissions and the climb in fuel prices are the main driving forces behind efforts to more effectively utilise various sources of renewable energy. In many parts of the world, direct solar radiation is considered to be one of the most prospective sources of energy. However, the large-scale utilisation of this form of energy is possible only if the effective technology for its storage can be developed with acceptable capital and running costs. One of prospective techniques of storing solar energy is the application of phase change materials (PCMs). Unfortunately, prior to the large-scale practical application of this technology, it is necessary to resolve numerous problems at the research and development stage. This paper looks at the current state of research in this particular field, with the main focus being on the assessment of the thermal properties of various PCMs, methods of heat transfer enhancement and design configurations of heat storage facilities to be used as a part of solar passive and active space heating systems, greenhouses and solar cooking.

- by Muhammad Nadjib
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- Engineering, Renewable Energy, Heat Transfer, Solar Energy

Thermal management requirements for aerospace
applications continue to grow while weight and volume
allotments remain constant or shrink. Compact, high
performance and lightweight heat transfer equipment is
needed to meet these high heat flux removal
requirements. Several innovative heat transfer
enhancement techniques are being considered for
development of thermal management components that
will meet these challenging demands. Honeywell, under
an AFRL funded program, is developing two new heat
exchanger technologies; microchannel and advanced
heat transfer surfaces to improve thermal management
systems for a fuel-to-air heat exchanger.
Heat transfer systems in military aircraft are increasingly
using fuel as a heat sink. Heat transport loops containing
several fuel-to-liquid heat exchangers are used to cool
electronics, engine oil, hydraulic oil, and elements of the
thermal management system. Microchannel heat
exchangers are especially suitable for these and other
high heat flux removal applications due to their good
thermal performance and extremely compact size.
Traditionally, they have been used for thermal
management of microelectronic devices. Recently,
Honeywell conducted heat exchanger design trade
studies, which highlights potential benefits of
microchannels. The results from this study suggest that
for liquid-air heat exchange applications, microchannel
based metallic heat exchangers can offer potential 20-
30% volume and/or weight reduction over state-of-theart
compact plate-fin design.
In the present study, use of microchannel and advanced
heat transfer surfaces for a fuel-to-air compact heat
exchanger for a fighter aircraft application is explored.
Preliminary results from heat exchanger performance
tradeoff and testing of prototype /subscale
microchannels heat exchangers are reported. Finally,
future development needs are summarized for their
successful insertion for full-scale production.

- by Arun Muley
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- Microchannels, Heat transfer enhancement, Compact heat exchangers

The objective of this paper is to review on the investigation made by different researchers for heat transfer enhancement in shell & tube heat exchanger by using Al2O3 nanofluid and the design modification with twisted tapes. The twisted tape insert is incorporated in tubes within the system. The use of the twisted tapes causes the swirl flow that enhances the heat transfer coefficient considerably. Basically heat exchanger is equipment which transfers the energy from hot fluid to a cold fluid, with maximum rate, minimum investment and running cost. Now due to the limitation of fossil fuels, subject to energy consumption optimization in various industrial processes becomes very important. The authors found that variously developed twisted tape inserts are popular researched and used to strengthen the heat transfer efficiency for heat exchangers.

These are the first version of my presentation for the course advanced heat transfer (Transferencia de Calor Avanzada)

- by Kambiz Vafai and +1
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- Engineering, Heat Transfer, Heat and Mass Transfer, Mathematical Sciences
- by Soheil Shahidinejad
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- Applied Mathematics, Heat Transfer, Pipe Flow, Heat Flux

This paper presents the performance tests carried out on a lab-scale latent heat storage (LHS) prototype during charging and discharging processes. The storage unit is a shell-and-tube type heat exchanger with embedded finned tubes, designed for an LHS capacity of 10 MJ. A ternary mixture comprising of potassium nitrate, sodium nitrate and sodium nitrite in the weight proportion of 53:7:40 is used as the phase change material (PCM). Hi-Tech Therm 60 is used as the heat transfer fluid (HTF). Performance parameters viz., melt fraction, charging/discharging time and energy storage/discharge rate were evaluated at different operating conditions. The effects of HTF inlet temperature and flow rate on the storage characteristics of LHS prototype were analyzed. It is observed that the temperature variation in the angular direction of the prototype during charging process is significant. This is due to the natural convection heat transfer that occurred around the molten layer of PCM while melting. During the discharging process, the angular temperature variation is negligible as the solidification phenomenon is controlled mainly by the conduction heat transfer. It took about 124 min/131 min for charging/discharging of the LHS prototype.

- by Hakeem Niyas and +1
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- Solar thermal, Phase Change Materials, Thermal Energy Storage, Heat transfer enhancement
- by Editor IJRET
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- Heat Transfer, Heat transfer enhancement

Keywords: Heat transfer enhancement Cross-flow jet SST k–x turbulence model Al 2 O 3 –water nanofluid a b s t r a c t In the present paper, the heat transfer performances of a nanofluid jet impinged normal to a protruded surface have been studied numerically in a three-dimensional computational domain. The water soluble Al 2 O 3 nanofluid has been employed as the working fluid both for the nozzle and the duct. A finite volume technique has been used to solve the conservation equations for mass, momentum, and turbulence (SST k–x turbulence). The duct and the nozzle Reynolds numbers based on the hydraulic diameters are varied in the range of 6000–20,000. The nanofluid volume fraction has been varied in the range of 0% 6 / 6 5%. For a particular volume fraction of nanofluid, it has been observed that the heat transfer augmentation is increased with the duct (Re Dh,duct) as well as the nozzle (Re Dh,nz) Reynolds number. For a particular volume fraction (/ = 5), when the duct and the nozzle Reynolds numbers have been increased from 6000 to 20,000, the area-weighted average Nusselt numbers (Nu Dh;duct) increases by 72.7% and 68.57%, respectively. Moreover, the addition of the solid nanoparticles to the base fluid enhances the heat transfer rate significantly. However, the pumping power requirement has also been increased with the volume fraction of nanofluid. The effects of the conductive/non-conductive protrusions and the temperature dependent properties on the heat transfer enhancement have also been discussed. The flow recir-culation in inter-protrusion gaps in the context of heat transfer augmentation has also been discussed.

- by Ashok Kumar Barik
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- Electronics Cooling, Heat transfer enhancement, Cross-flow
- by Ammar Alsairafi
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- Chemical Engineering, Computational Fluid Dynamics, Modeling, Heat Transfer

The aim of this study is to improve the heat transfer in a double tube heat exchanger by using four samples of the inner tube (smooth tube, half circular finned tube, circular finned tube and circular helical finned tube). The experiments were carried out by using the four kinds of fluids flow, namely, (a parallel flow of cold water inside the inner tube, a parallel flow of hot water inside the inner tube, the counter flow of cold water inside the inner tube and the counter flow of hot water inside the inner tube). The comparative results of the finned tubes with respect to the smooth tube showed the highest values of heat transfer coefficient obtained at the circular helical finned tube instate of hot water flow inside the tube. The convection heat transfer coefficient increased by (250 and 165)% for both flows (parallel and counter), respectively in case of turbulent flow, while in state of the hot water flow on the outer surface of the inner tube, the heat transfer coefficient increased by 230 % for parallel flow and in the case of the counter flow increased by 260 %. The fanning friction factor was affected by a condition of the working fluids where in the case of hot fluid flows outside surface of the inner tubes, the min. values of fanning friction factors was obtained from smooth tube sample which is ranged from 0.01 to 0.05 and other samples are ranged from 0.008 to 0.05. A: Cross section area m 2 cp : specific heat J/kg. ℃ D: Diameter m f: Fanning friction factor h: heat transfer coefficient W/m 2 .℃

- by Ehsan Fadhil
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- Heat transfer enhancement
- by Eiyad Abu-Nada
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- Mechanical Engineering, Civil Engineering, Applied Mathematics, Heat Transfer

This paper reports the heat transfer enhancement and corresponding pressure drop over a flat surface equipped with circular cross section perforated pin fins in a rectangular channel. The channel had a cross section area of 100–250 mm2. The experiments covered the following ranges: Reynolds number 13500–42,000, clearance ratio (C/H) 0, 0.33 and 1 and interfin spacing ratio (Sy/D) 1.208, 1.524, 1.944 and 3.417. Correlation equations were developed for the heat transfer, friction factor and enhancement efficiency. The experimental results showed that the use of circular cross section pin fins may lead to heat transfer enhancement. Enhancement efficiencies varied between 1.4 and 2.6 depending on clearance ratio and interfin spacing ratio. Using a Taguchi experimental design method, optimum design parameters and their levels were investigated. Nusselt number and friction factor were considered as performance parameters. An L9(33) orthogonal array was selected as an experimental plan. First of all, each goal was optimized separately. Then, all the goals were optimized together, considering the priority of the goals, and the optimum results were found to be Reynolds number of 42,000, fin height of 50 mm and streamwise distance between fins of 51 mm.

- by Alparslan Demir
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- Heat Transfer, Heat Exchanger, Experimental Design, Performance Analysis

The focus of this research paper is on the application of water based MgO
nanofluids for thermal management of a car radiator. Nanofluids of different volumetric
concentrations (i. e. 0.06%, 0.09%, and 0.12%) were prepared and then experimentally
tested for their heat transfer performance in a car radiator. All concentrations
showed enhancement in heat transfer compared to the pure base fluid.
A peak heat transfer enhancement of 31% was obtained at 0.12% volumetric concentration
of MgO in basefluid. The fluid flow rate was kept in a range of 8-16 liter
per minute. Lower flow rates resulted in greater heat transfer rates as compared to
heat transfer rates at higher flow rates for the same volumetric concentration. Heat
transfer rates were found weakly dependent on the inlet fluid temperature. An increase
of 8 °C in inlet temperature showed only a 6%increase in heat transfer rate.

- by Hafiz Muhammad Ali
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- Thermal Engineering, Heat Transfer, Heat and Mass Transfer, Nanofluids

The heat transfer phenomena inside a horizontal channel with an open trapezoidal enclosure subjected to a heat source of different lengths was investigated numerically in the present work. The heat source is considered as a local heating element of varying length, which is embedded at the bottom wall of the enclosure and maintained at a constant temperature. The air flow enters the channel horizontally at a constant cold temperature and a fixed velocity. The other walls of the enclosure and the channel are kept thermally insulated. The flow is assumed laminar, incompressible, and two-dimensional, whereas the fluid is considered Newtonian. The results are presented in the form of the contours of velocity, isotherms, and Nusselt numbers profiles for various values of the dimensionless heat source lengths (0.16 ≤ ε ≤ 1). while, both Prandtl and Reynolds numbers are kept constant at (Pr = 0.71) and (Re = 100), respectively. The results indicated that the distribution of the isotherms depends significantly on the length of the heat source. Also, it

- by Danesh Tafti
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- Engineering, Modeling, Heat Transfer, Large Eddy Simulation

This paper elaborates on the findings of study on the effect of Fe2O3/Kerosene nanofluid to the copper closed-loop oscillating heat pipe under the magnetic field for inclination angles ranging from 0° to 90°, under different heat inputs (10–90 W). The heat pipe’s heat transfer coefficient was measured without and with the magnetic field. Moreover, the vapor temperature was assessed directly at the center of the oscillating heat pipe by exposing the ferro-nano particles to a magnetic field. It was shown that Fe2O3 nanoparticles could improve the thermal resistance and subsequently thermal performance as well as the pipe’s heat transfer coefficient, especially under the magnetic field. The heat pipe’s heat transfer coefficient increased as the input heat flux increased. The results also demonstrated that the heat pipe’s inclination angle had a significant effect on performance of heat pipe. The critical angle was 75° as the heat transfer coefficient increased due to higher inclination angle.

- by Mohammad Reza Safaei and +1
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- Heat Transfer, Nanoparticle, Nanoparticles, Nanoscale heat transfer
- by Sanjay Rawat
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- Renewable Energy, Friction Correction Factor, Heat transfer enhancement
- by Eiyad Abu-Nada
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- Mechanical Engineering, Applied Mathematics, Natural Convection, Nanofluid
- by Mahmoud Khaled
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- Engineering, Economics, Heat Exchanger, Air flow
- by Eiyad Abu-Nada
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- Mechanical Engineering, Aerospace Engineering, Modeling, Heat Transfer

The main objective of this experimental study is to quantify and compare the forced convection heat transfer enhancement of pin fin with using different materials. In this study, the steady state heat transfer from the pin fin is measured. The increase in the heat transfer coefficient was achieved with copper pin fin at 100 watt heat input considerably in comparison with that of the other materials pin–fin over the whole range of Reynolds numbers. Pin fin made of steel material had less heat transfer coefficient as compared to other materials.

Laminar counter and parallel flows in a double pipe heat exchanger is studied experimentally using two types of nanofluids as a cooling medium. The nanofluids consist of Al 2 O 3 and TiO 2 nanoparticles, which were added to the base fluid (deionized water). The average diameter of nanoparticles is approximately 20 nm for both Al 2 O 3 and TiO 2 nanoparticles. The volume concentrations of nanofluid was varied with a range of (0.05-0.3) percentage and the flow rates of the base and nanofluids were varied with a range of (0.5-2) L/min. Hot fluid (water) is flowing in the inner tube of heat exchanger with constant inlet temperature and the cold fluid (nanofluid) is introduced in the outer tube with constant inlet temperature. Compared to the base fluid, the results showed that the nanofluid containing Al 2 O 3 and TiO 2 nanoparticle exhibits enhanced heat transfer, and this enhancing is clearly reflected by the increase in the inside and outside heat transfer coefficients, thus the overall heat transfer coefficient, where the percentage enhancement in heat transfer coefficient of nanofluid per base fluid is (18.25 and 15.5) % for Al 2 O 3-water and TiO 2-water nanofluid respectively. The enhanced performance of heat exchanger is due to high value of thermo physical properties of fluid when dispersing nanoparticles in the base fluid. 2 Keywords: Nanofluid; The performance of double pipe heat exchanger; laminar parallel and counter flows.

- by Prof.Dr.Mushtaq I. Hasan
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- Heat Transfer, Heat Exchanger, Nanofluids, Heat transfer enhancement

Minichannel heat sink geometries with varying fin spacing were tested with
de-ionized water and MWCNT (1 wt %) nanofluid to evaluate their performance with
flow components of a liquid cooling kit. Four heat sinks with fin spacing of 0.2 mm,
0.5 mm, 1.0 mm, and 1.5 mm were used in this investigation. Heat sink base
temperature was analogous to processor operating temperature which was the prime
parameter of interest in this investigation. The base temperature decreased by reducing
the fin spacing and using multiwalled carbon nanotube (MWCNT) nanofluid. The
lowest value of heat sink base temperature recorded was 49.7 °C at a heater power of
255 W by using a heat sink of 0.2 mm fin spacing and MWCNT nanofluid as a coolant.
Moreover, as a result of reduced fin spacing and using MWCNT nanofluid as a coolant
the value of overall heat transfer coefficient increased from 1200 W/m2K to 1498
W/m2K, translating to about a 15% increase. The value of thermal resistance also
dropped by reducing the fin spacing and using MWCNT nanofluid. The most
important aspect of the study is that the heat sinks and MWCNT nanofluid proved
to be compatible with the pump and radiator of the commercial CPU liquid cooling
kit. The pump was capable to handle the pressure drop which resulted by reducing
the heat sink fin spacing and by using MWCNT nanofluid. © 2013 Wiley
Periodicals, Inc. Heat Trans Asian Res
11 November 2013 in Wiley Online Library (wileyonlineli-brary.com/journal/
htj). DOI 10.1002/htj.21107

- by Hafiz Muhammad Ali
- •
- Heat Transfer, Heat and Mass Transfer, Nanofluids, Nanofluid (Heat Transfer)