Begell House Inc.
Journal of Enhanced Heat Transfer
JEH(T)
1065-5131
21
1
2014
THE EXPANDING EXPRESSION OF ENHANCED HEAT AND MASS TRANSFER, FOR "THE TIMES THEY ARE A-CHANGIN'......"
v-ix
10.1615/JEnhHeatTransf.2015013835
Raj M.
Manglik
Thermal-Fluids and Thermal Processing Laboratory, Mechanical and Materials Engineering, University of Cincinnati, 2600 Clifton Ave, Cincinnati, OH 45220, USA
Enhancement taxonomy; Editorial
This submission is the lead EDITORIAL for Vol. 21, No. 1, 2014
EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER CHARACTERISTICS IN WATER SHOWER COOLING OF STEEL PLATE
1-20
10.1615/JEnhHeatTransf.2015003888
Purna Chandra
Mishra
Thermal Research Laboratory (TRL), School of Mechanical Engineering, Kalinga
Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
Swarnendu
Sen
Department of Mechanical Engineering, Jadavpur University, Kolkata 700032, India
Achintya
Mukhopadhyay
Department of Mechanical Engineering, Jadavpur University, Kolkata-700032,
West Bengal, India
jet impingement
single-phase flows
impingement density
transient temperature
mass flux
Heat transfer characteristics of shower cooling on a hot flat steel plate were investigated using the transient temperature measurement technique. Two shower cooling configurations adapted to cool the flat stationary steel surface of 4 mm thickness were directly compared for various factors such as initial plate temperature, water flow rates, average and local impingement density variation, and shower tip-to-plate space. The dimensionless initial temperature difference (ΔT*i) of the plate ranged from 6.67 to 16.67. The local and average impingement densities were measured by means of a simple mechanical patternator. A transient temperature measurement technique was applied with the help of K-type thermocouples embedded at the bottom surface of the plate. The observation revealed that optimum shower hole arrangement and design of the showerhead could achieve a higher cooling rate from a steel surface at higher temperature. For given water flow rates, local impingement density distribution decreases with increase in shower tip-to-plate distance. The mass flux profiles obtained for two different showers show quite different trends.
AN EXPERIMENTAL INVESTIGATION OF ENHANCED HEAT TRANSFER DUE TO A GAP IN A CONTINUOUS MULTIPLE V-RIB ARRANGEMENT IN A SOLAR AIR CHANNEL
21-49
10.1615/JEnhHeatTransf.2015012449
Anil
Kumar
Department of Mechanical Engineering, University of Petroleum and Energy
Studies, Dehradun, India
R. P.
Saini
Alternate Hydro Energy Centre, IIT, Roorkee, Uttarakhand-247667, India
J. S.
Saini
Mechanical and Industrial Engineering Department, IIT, Roorkee, Uttarakhand-247667, India; Department of Mechanical Engineering, DIT University, Dehradun, U.K, India
single phase convection
rough surfaces
passive enhancement
solar energy
thermo-hydraulic performance
This work is concerned with the experimental investigation of a multi V-rib with a gap of solar air channel based on thermal as well as hydraulic performance. The rib produced on the heated plate forms the wetted side of an upper broad wall of the solar air channel. Experimentation was carried out on 41 sets of roughened surfaces having different sets of values of roughness geometry parameters to collect heat transfer and friction data. The data have been presented in the form of variation of Nu/Nus and f/fs as a function of rib parameters of artificial roughness. The e/D was varied from 0.022 to 0.043, Gd/Lv was varied from 0.24 to 0.80, g/e was varied from 0.5 to 1.5, α was varied from 30° to 75°, P/e was varied from 6.0 to 12.0, and W/w was varied from 1.0 to 10.0. It has been found that the values of thermo-hydraulic performance parameter increase with increase in Re and become almost asymptotic in the higher range of Re. The absolute maximum value of thermal as well as hydraulic performance parameter has been found to be higher corresponding to e/D of 0.043, W/w of 6.0, Gd/Lv of 0.69, g/e of 1.0, α of 60°, and P/e of 8.0. Multiple V-rib with gap solar air channel with e/D of 0.043, W/w of 6.0, Gd/Lv of 0.69, g/e of 1.0, α of 60°, and P/e of 8.0 has better thermal as well as hydraulic performance as compared to other rib shapes investigated by various investigators under similar operating conditions.
ELECTROHYDRODYNAMIC (EHD) ENHANCEMENT OF NATURAL CONVECTION HEAT TRANSFER FROM A HEATED INCLINED PLATE
51-61
10.1615/JEnhHeatTransf.2015010366
Mahdi
Sahebi
Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156, IR Iran
Ali Akbar
Alemrajabi
Isfahan University of Technology
Isfahan 8415683111
I.R. Iran
single-phase convection
electrostatic fields
active enhancement
buoyancy-driven convection
The effect of applying an electric field on natural convective heat transfer enhancement from an inclined heated plate was investigated experimentally. The effect of parameters such as applied voltage, heat flux, angle of inclination, and spacing of electrodes on heat transfer enhancement was studied. It was found that by increasing the applied voltage, increasing the angle of inclination, and decreasing electrode spacing, the enhancement ratio increases. The maximum enhancement was obtained for the bottom surface of the horizontal plate, as for this case the enhancement ratio of 4.5 was obtained by applying 17.5 kV voltage.
EXPERIMENTAL STUDY OF BUBBLE GROWTH AND FLOW IN SMALL-DIAMETER THERMOSYPHON LOOPS WITH FILLING RATIOS OF 90% AND 95%
63-73
10.1615/JEnhHeatTransf.2015012617
Lingjiao
Wei
Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China
Dazhong
Yuan
Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China
Ya
Feng
Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
Dawei
Tang
Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190, China
surface tension device
two-phase flow
closed-loop thermosyphon
vapor bubbles
heat transfer
slug flow
Taylor bubble
In order to improve the understanding of the heat transfer mechanism in a two-phase closed thermosyphon loop with a liquid heat transfer agent (TPCTLL), a visualization experiment has been conducted to investigate the hydrodynamic flow in two loops with filling ratios of 90% and 95%, respectively. In this experiment, the bubble growth at the startup stage and the slug flow patterns at the steady stage have been observed by a digital high-speed camera. It is shown that the first generated bubble grew to the maximum size within 35 ms in tested loops; and the bubble rising velocity in the loop with the filling ratio of 90% was 0.35±0.05 m/s. In comparison with single-phase closed thermosyphon loops (SPCTLs), the liquid circulation in TPCTLLs is accelerated by vapor bubbles. Thus TPCTLLs can achieve a better thermal performance than SPCTLs.
EFFECT OF CORRUGATION ANGLE ON THE MOISTURE TRANSFER AND PRESSURE DROP FOR HUMIDIFYING ELEMENT MADE OF CELLULOSE AND PET
75-88
10.1615/JEnhHeatTransf.2015012471
Nae-Hyun
Kim
Department of Mechanical Engineering, Incheon National University, Incheon 406-772, Republic of Korea
swirl flow devices
single phase flow
mass transfer
plate heat/mass exchanger
In this study, new humidifying element samples were made, and the moisture transfer and pressure drop characteristics were investigated. Results show that the new sample (cellulose 50% and PET 50%) yielded superior moisture transfer and pressure drop performance than the currently widely used GLASdek (glass wool) and CELdek (cellulose). The jm factors of the new sample are 33%−39% larger than those of GLASdek and 3.2%−13% larger than those of CELdek. On the other hand, f factors of the new sample are 0%−44% smaller than those of GLASdek, and 4.0%−35% larger than CELdek. In general, the jm or f factor increased as corrugation angle increased. The moisture transfer efficiency index (jm/f1/3) was the largest for a 15°/15° sample, followed by 30°/30°, 45°/45°, 15°/45°, and 60°/60° samples. Correlations are developed to predict jm and f factors of the samples having different corrugation angles.