Begell House Inc.
Journal of Enhanced Heat Transfer
JEH(T)
1065-5131
22
1
2015
INVESTIGATION OF HEAT TRANSFER CHARACTERISTICS OF MGMNNI/DIW-BASED NANOFLUIDS FOR QUENCHING IN INDUSTRIAL APPLICATIONS
1-28
10.1615/JEnhHeatTransf.2015013268
Subbiah
Chitra
P K N Art's and Science College, Tirumangalam, Madurai, Tamilnadu, India
Sechasalom
Sendhilnathan
Department of Physics at University College of Engineering, Constituent College of Anna University, Chennai. Pattukkottai, Tamil Nadu in India
Sivan
Suresh
Mechanical Department, National Institute of Technology-Tiruchirappalli, Tamil Nadu, India
additives for liquids
single-phase convection
thermophysical properties
thermal conductivity
density
volumetric specific heat
rheological property of viscosity
Effective thermal conductivity of nanofluids is measured using the KD2 Pro method and the viscosity measurements obtained by the Brookfield DV-E viscometer. The tested fluids contain nanoparticles of MgMnNiFe2O4 dispersed in DIW as a base fluid. Experimental results show that the thermal conductivities of nanofluids are higher than those of the base fluids. We demonstrate that the predicted thermal conductivities of nanofluids in existing models are much lower than our measured data. A possible mechanism contributing to the enhancement of nanofluid thermal conductivity is discussed. The effects of Reynolds number, Nusselt number, Prandtl number, and nanoparticle concentration on heat transfer performance are also reported and discussed. Experimental results on thermophysical properties and convective heat transfer characteristics are compared with theoretical simulations based on assumptions regarding thermal and heat transfer enhancement for quenching in industrial applications.
EXPERIMENTAL STUDY OF PRESSURE DROP AND HEAT TRANSFER IN A U-BEND CHANNEL WITH VARIOUS GUIDE VANES AND RIBS
29-45
10.1615/JEnhHeatTransf.2015013382
Susanna
Cimina
Department of Energy, Politecnico di Milano, Via Lambruschini 4, Milano IT−20156, Italy
Chenglong
Wang
Division of Heat Transfer, Department of Energy Sciences, Lund University, Box 118, Lund,
SE-2 2 100, Sweden
Lei
Wang
Division of Heat Transfer, Department of Energy Sciences, Lund University, Box 118, Lund,
SE-2 2 100, Sweden
Alfonso
Niro
Department of Energy, Politecnico di Milano, Via Lambruschini 4, Milano IT−20156, Italy
Bengt
Sunden
BS Heat Transfer and Fluid Flow
rough surfaces
structured roughness
single-phase flow
bend duct geometry
guide vanes
liquid crystal thermography
An experimental study was conducted to investigate pressure drop and heat transfer in a U-bend section with various configurations of guide vanes and two kinds of rib shapes on the outer wall. Ten guide vane types were tested. Results highlight that the use of special guide vanes can reduce the pressure drop penalty up to a maximum of 31%. However, guide vanes are usually associated with heat transfer reduction. To further enhance heat transfer, transverse and V-shaped ribs were attached on the outer wall. Thermal performance evaluation showed that the 45° V-shaped downstream-pointing ribs coupled with guide vane configuration 5 give the best thermal performance. The results of this study can be employed to improve the internal design of modern gas turbine blade cooling systems.
FLOW BOILING HEAT TRANSFER IN R-600A FLOWS INSIDE AN ANNULAR TUBE WITH METALLIC POROUS INSERTS
47-65
10.1615/JEnhHeatTransf.2015010426
Mao-Yu
Wen
Department of Mechanical Engineering, Cheng Shiu University, Kaohsiung 833, Taiwan, ROC
Kuang-Jang
Jang
Department of Mechanical Engineering, Cheng Shiu University, Kaohsiung 833, Taiwan, ROC
Ching-Yen
Ho
Department of Mechanical Engineering, Hwa Hsia University of Technology, Taipei 235, Taiwan, ROC
displaced enhancement devices
two-phase flow
perforated copper inserts
annular tube
forced convection boiling
This investigation was undertaken to better understand the characteristics of flow boiling heat transfer (in which only the inlet is subcooled) in a hydrocarbon refrigerant, R-600a (isobutane), flowing in an annular tube with and without perforated copper porous inserts. Testing was conducted at a saturation temperature of 5° C, vapor qualities of 0.08−0.87, mass fluxes of 300−400 kg/m2s, and heat fluxes of 119.5−195.3 kW/m2. The effects of mass flux, heat flux, vapor quality, and insert geometry (porosity, mean pore diameter, and permeability) on R-600a heat transfer and pressure drop are discussed.
AN EXPERIMENTAL INVESTIGATION OF THE AIR-SIDE PERFORMANCE OF FIN-AND-TUBE HEAT EXCHANGERS HAVING SLIT FINS
67-88
10.1615/JEnhHeatTransf.2015013309
Nae-Hyun
Kim
Department of Mechanical Engineering, Incheon National University, Incheon 406-772, Republic of Korea
Honggi
Cho
Advanced R&D Team, Digital Appliances, Samsung Electronics, 129 Samsung-ro, Yeongtong-gu, Suwon, 16677, South Korea
extended surfaces
single-phase convection
heat transfer coefficient
pressure drop
predictive correlations
In this study, the heat transfer and friction characteristics of 5.3-mm outer-diameter slit-fin heat exchangers were experimentally investigated. Plain-fin heat exchangers having the same 5.3-mm outer-diameter tubes were also tested for comparison. Results revealed that slit-fin samples yielded higher j and f factors than plain-fin samples. As for the effect of number of tube rows, the j factor increased as the number of tube rows decreased, but the f factor was independent of this effect (except in the one-row configuration). The one-row samples yielded significantly higher f factors, especially at low Reynolds numbers. The j/f ratios for the slit fin samples were larger than those for the plain-fin samples at high Reynolds numbers. At low Reynolds numbers, in contrast, they were smaller. A new correlation was developed based on the present data.