Begell House Inc.
Heat Transfer Research
HTR
1064-2285
49
16
2018
PERFORMANCE OF AN AUTOMOTIVE CAR RADIATOR OPERATED WITH NANOFLUID-BASED COOLANT
1527-1543
10.1615/HeatTransRes.2018020810
Shiva
Kumar
Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology,
Manipal Academy of Higher Education, Manipal — 576104, India
Pijakala
Dinesha
Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology,
Manipal Academy of Higher Education, Manipal — 576104, India
Ashutosh
Gaggad
Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology,
Manipal Academy of Higher Education, Manipal — 576104, India
Kshitij
Mehrotra
Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology,
Manipal Academy of Higher Education, Manipal — 576104, India
radiator
nanofluid
thermal conductivity
heat transfer coefficient
volume fraction
Coolants such as water and ethylene glycol have been used traditionally in automotive car radiators. However, due to their low thermal conductivity a class of fluids known as nanofluids is used to enhance heat transfer characteristics. Nanofluids are suspended metallic or nonmetallic oxide nanoparticles in traditional heat transfer fluids that have bulk thermal conductivity higher than that of the base fluids. This experimental study is based on the application of an aluminum oxide (Al2O3)-based nanofluid with water as a base fluid in automotive car radiators. The effect on the overall heat transfer coefficient, heat transfer rate, and pressure drop are calculated by varying the percentage volume fraction of nanoparticles in water, volume flow rate of the nanofluid, and also the inlet temperature of the nanofluid. It is observed that as the nanoparticle concentration increased, the overall heat transfer coefficient and heat transfer rate increase, peaking at 0.8%. As the inlet temperature of the nanofluid increases, the overall heat transfer coefficient was found to be increasing. For a nanoparticle concentration of 0.8% with water, for a flow rate of 3 LPM and for inlet temperature of 80°C, the overall heat transfer coefficient and heat transfer rates were increased by 36.27% and 25.95%, respectively, when compared to pure water.
SIMULATION AND OPTIMIZATION OF HEAT-EXCHANGER PARAMETERS OF HEAT PIPES BY CHANGES OF ENTROPY
1545-1557
10.1615/HeatTransRes.2018019336
Andriy
Redko
National University of Construction and Architecture, Department of Heat, Gas Supply, Ventilation
and using Thermal Second Energy Resources, 40 Sumskaya Str., Kharkiv, 61002, Ukraine
Nataliia
Kulikova
National University of Construction and Architecture, Department of Heat, Gas Supply, Ventilation and using Thermal Second Energy Resources, 40 Sumskaya Str., Kharkiv, 61002, Ukraine
Serhii
Pavlovskiiy
National University of Construction and Architecture, Department of Heat, Gas Supply, Ventilation and using Thermal Second Energy Resources, 40 Sumskaya Str., Kharkiv, 61002, Ukraine
Alexander
Redko
National University of Construction and Architecture, Department of Heat, Gas Supply, Ventilation and using Thermal Second Energy Resources, 40 Sumskaya Str., Kharkiv, 61002, Ukraine
heat exchanger
heat utilizer
heat pipes
production of entropy
thermodynamic efficiency
irreversible losses
The results of numerical simulation and optimization of the design and operational characteristics of heat exchangers — heat utilizers of liquid-gas type are presented. Minimum production of entropy has been taken to be one of the criteria. The effect of heat-carrier rates and the change of the thermal load on the thermodynamic heat-utilizer efficiency is shown. Optimal regularities of changing heat-exchanger temperatures in the countercurrent heat exchange apparatus in different operating modes and at different design parameters have been determined. Applied solutions of heat-utilizer optimization by nonequilibrium thermodynamic methods have been analyzed.
TURBULENT DECAYING SWIRLING FLOW IN A PIPE
1559-1585
10.1615/HeatTransRes.2018021519
V.
Aghakashi
Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif University of Technology, Tehran, 11155-9567, Iran
Mohammad Hassan
Saidi
Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif
University of Technology, P.O. Box 11155-9567, Tehran, Iran
swirling flow
Nusselt number
thermal boundary layer
integral scheme
In this work, a solution is applied to investigate the heat transfer characteristics in a pipe with turbulent decaying swirling flow by using the boundary layer integral scheme. The governing equation is solved using the forth-order Runge-Kutta scheme resulting in thermal boundary-layer thickness and dimensionless heat transfer coefficient, namely, the Nusselt number. Both forced- and free-vortex profiles are considered for the tangential velocity component. A comparison of the results obtained for the Nusselt number with available experimental data shows that this scheme has good capability in predicting the heat transfer parameters of swirling flow especially in the entrance region of a pipe. The results of the present work specify that in swirling flow, the forced-vortex velocity profile is more accurate in predicting the heat transfer coefficient as compared with the free-vortex one. Also, the effects of the inlet Reynolds number, inlet swirl intensity, and of the Prandtl number on the thermal boundary-layer thickness and Nusselt number are studied, and it is realized that the variation of these two parameters depends on the inlet Reynolds number, inlet swirl intensity, and the Prandtl number. The results show that increasing the inlet swirl intensity has a strong increasing effect on the heat transfer rate.
OBLIQUE STAGNATION-POINT FLOW OF NON-NEWTONIAN FLUID WITH VARIABLE VISCOSITY
1587-1603
10.1615/HeatTransRes.2018018569
R.
Mehmood
Department of Mathematics, Faculty of Natural Sciences, HITEC University, Taxila Cantt, Pakistan
Rabil
Tabassum
Department of Mathematics, Faculty of Natural Sciences, HITEC University, Taxila Cantt, Pakistan
Noreen Sher
Akbar
DBS&H, CEME, National University of Sciences and Technology, Islamabad, Pakistan
oblique flow
heat transfer
variable viscosity
non-Newtonian fluid
Casson fluid
numerical solution
The present analysis deals with steady two-dimensional oblique stagnation-point flow of an incompressible Casson fluid with variable viscosity. The variation of viscosity is expressed as an exponential function of temperature. Using the scaling group of transformations, the governing partial differential equations are transformed into a set of nonlinear coupled ordinary differential equations which are solved numerically via the fourth-order Runge-Kutta-Fehlberg scheme coupled with a shooting technique. Variations of diverse parameters on normal, tangential velocity profiles, and temperature are expressed by graphs. The physical quantities of interest such as skin friction coefficients and local heat flux are investigated numerically. Streamline patterns are portrayed to visualize the actual flow behavior against various parameters. It is found that the viscosity variation parameter has increasing effects on the tangential velocity profile (near the wall), temperature distribution, and normal skin friction coefficient, while the normal velocity profile and tangential skin friction coefficient decrease with viscosity parameter.
NUMERICAL AND EXPERIMENTAL STUDY OF FLOW AND HEAT TRANSFER IN OUTWARDLY CONVEX CORRUGATED TUBES WITH A TWISTED TAPE INSERT
1605-1628
10.1615/HeatTransRes.2018020644
Huaizhi
Han
School of Chemical Engineering, Sichuan University, Chengdu 610064, China; College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China
Longbin
Yang
Harbin Engineering University
Xin
Chen
School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Bingxi
Li
School of Energy Science and Engineering, 1Harbin Institute of Technology, 92 West Dazhi Street, Nangang District, Harbin 150001, China
corrugated tube
twisted tape insert
heat transfer enhancement
numerical simulation
This study involves numerical and experimental investigations on flow and heat transfer in an outwardly convex corrugated tube with various structural twisted tape inserts (CT) by using computational fluid dynamics (CFD) methods. The numerical mode is validated by comparing it with experimental data for a smooth tube and corrugated tubes in a developed experimental apparatus. The study also includes a comparison of thermodynamic performances of a CT, a smooth tube with a twisted tape insert (ST), and of a smooth tube to determine their differences. The influence of a twist ratio is considered to analyze thermodynamic regulation and reveal the mechanism operating in CT. The numerical results also agree well with the experimental results on the Nusselt number and friction factor of the corrugated and smooth tubes. The maximum deviations are controlled within ± 6% for Nuc and ± 7.6% for fc. The Nu in the CT exceeds those in the ST and smooth tube by 120-136% and 171-317%, respectively. The friction factor in the CT exceeds those in the ST and plain tube by 148-153% and 476-514%, respectively. The effect of twist ratio in a CT is considered, and the results indicate that the best overall thermal performance (η = 1.97) is obtained with a high twist ratio (y/w = 5). However, the highest thermal performance (Nuc/Nus = 4.78) is obtained with the lowest twist ratio (y/w = 1.25). The contour plots indicate that a potential reason for this can be attributed to the coexistence of the corrugated tubes and tapes that provide a synergetic swirling effect, which efficiently reduces the thermal and velocity boundary layer developments and thus effectively increases the heat transfer performance.
THE METHODOLOGY OF HEAT RELEASE CHARACTERISTICS DETERMINATION ON THE BASIS OF THE REAL INDICATOR DIAGRAM
1629-1644
10.1615/HeatTransRes.2016010176
Tomasz
Ambrozik
Kielce University of Technology, Department of Automotive Vehicles and Transportation, Kielce,
Poland
combustion
diesel engine
heat release
multiple injection
The article presentes a methodology for determining the characteristics of heat release in a self-ignition internal combustion engine based on real indicator diagrams. The proposed algorithm enables determining the total relative released heat quantity, the indicated relative released heat quantity, heat losses, and the indicated relative released heat quantity rate. The article reports the results of experimental tests of a self-ignition FIAT MultiJet 1.3 SDE 90 KM engine operating under full load conditions. During the operation of the engine, a single-, two-, and three-stage fuel injections were done. On the basis of the investigation carried out, the engine heat release characteristics have been determined and analyzed. The obtained investigation results indicate the possibility of using the multistage fuel injection for both shaping the characteristics of an internal combustion engine and reducing the emissions of harmful components in exhaust gases.