An Experimental Study of Heat Transfer on a Smooth U-Bend Channel Surface

2012 ◽  
Author(s):  
Lei Wang ◽  
Tareq Salameh ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Experimental Studies ◽  
Jet Impingement ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Primary Mechanism ◽  
Channel Surface ◽  
Bend Channel ◽  
Nozzle Plate

Experimental studies are carried out to investigate the tip-wall heat transfer in a U-bend channel. Liquid crystal technique is employed to measure the wall temperature and obtain the heat transfer coefficients. The Reynolds number is varied from 10,000 to 24,000. It is found that the tip-wall heat transfer in a U-bend channel is characterized by the feature of jet impingement. The local Nusselt number is scaled by a factor of Re0.5, which is close to the heat transfer scaling in the jet impingement for low nozzle-plate spacings. The result corroborates the previous studies that the jet impingement is a primary mechanism to enhance the heat transfer in a U-bend channel.

Flow and Heat Transfer of Confined Impingement Jets Cooling

2000 ◽  
Author(s):  
Ting Wang ◽  
Mingjie Lin ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Structure ◽  
Experimental Studies ◽  
Cross Flow ◽  
Jet Impingement ◽  
Target Surface ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Transfer Behavior

Experimental studies on heat transfer and flow structure in confined impingement jets were performed. The objective of this study was to investigate the detailed heat transfer coefficient distribution on the jet impingement target surface and flow structure in the confined cavity. The distribution of heat transfer coefficients on the target surface was obtained by employing the transient liquid crystal method coupled with a 3-D inverse transient conduction scheme under Reynolds number ranging from 1039 to 5175. The results show that the average heat transfer coefficients increased linearly with the Reynolds number as Nu = 0.00304 Pr0.42Re. The effects of cross flow on heat transfer were investigated. The flow structure were analyzed to gain insight into convective heat transfer behavior.

Effects of Shallow-Angle Jet Impingement and Free Stream Velocity on Heat Transfer

2010 ◽  
Author(s):  
Lei Wang ◽  
Bengt Sunde´n ◽  
Borg Andreas ◽  
Hans Abrahamsson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Velocity Ratio ◽  
Experimental Studies ◽  
Jet Impingement ◽  
Stream Velocity ◽  
Wall Jet ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Crossflow Velocity

Experimental studies are carried out to investigate the heat transfer characteristics involving an impinging jet with a shallow-angle in a crossflow. Liquid crystal technique is employed to measure the wall temperature and obtain the heat transfer coefficients. In the study, the Reynolds number for the crossflow is range from 80,000 to 160,000 and the Reynolds number for the jet varies from 20,000 to 40,000. The jet-to-crossflow velocity ratio changes from 2.4 to 4.9. For a constant velocity ratio R = 3.5, it is found that the structure of heat transfer changes in nature as both Reynolds number increases. In addition, it is observed that the heat transfer in the wall jet region is uniquely determined by the jet and is independent of the crossflow. A correlation is constructed to fit data and predict the Nusselt number in this region.

Method and tools for determining heat transfer coefficients in organic liquids and solutions

2020 ◽  
pp. 45-55
Author(s):  
Aleksandr S. MYAKOCHIN ◽  
Petr V. NIKITIN ◽  
Sergey Yu. POBEREZHSKIY ◽  
Anna A. SHKURATENKO
Keyword(s):  
Heat Transfer ◽  
Experimental Studies ◽  
Pulse Method ◽  
Organic Liquids ◽  
Transfer Coefficients ◽  
Resistance Thermometer ◽  
Film Sensor ◽  
Heat Transfer Coefficients ◽  
Aerospace Technology ◽  
New Generation

The paper presents a method, tools and a newly developed algorithm for experimentally determining heat transfer coefficients in organic liquids and solutions. This work is made relevant by the problem of development of a new generation of aerospace technology. In this connection, improvements have been made to the pulse method of determining heat transfer coefficients that is based on the use of a micron-thick film sensor. The measurement setup was modified. A math model was constructed for the measuring sensor. Algorithms were developed for conducting the experiment and processing measurement results to determine heat transfer coefficients. Experimental uncertainties were analyzed. The paper provides results of experimental studies on certain organic liquids. The authors believe that the material presented in the paper will find application in research conducted at research institutions, engineering offices and universities, among researches, postgraduates and students. Key words: thermal and physical characteristics, organic liquids and their solutions, film-type electrical resistor, thin-film temperature sensor, voltage pulse, resistance thermometer, irregular heat transfer regime.

Single-Phase and Boiling Cooling of Small Pin Fin Arrays by Multiple Nozzle Jet Impingement

1996 ◽  
Vol 118 (1) ◽  
pp. 21-26 ◽  
Author(s):  
David Copeland
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Single Phase ◽  
Jet Impingement ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Aspect Ratios ◽  
Pin Fin Arrays

Experimental measurements of multiple nozzle submerged jet array impingement single-phase and boiling heat transfer were made using FC-72 and 1 cm square copper pin fin arrays, having equal width and spacing of 0.1 and 0.2 mm, with aspect ratios from 1 to 5. Arrays of 25 and 100 nozzles were used, with diameters of 0.25 to 1.0 mm providing nozzle area from 5 to 20 mm2 (5 to 20% of the heat source base area). Flow rates of 2.5 to 10 cm3/s (0.15 to 0.6 l/min) were studied, with nozzle velocities from 0.125 to 2 m/s. Single nozzles and smooth surfaces were also evaluated for comparison. Single-phase heat transfer coefficients (based on planform area) from 2.4 to 49.3 kW/m2 K were measured, while critical heat flux varied from 45 to 395 W/cm2. Correlations of the single-phase heat transfer coefficient and critical heat flux as functions of pin fin dimensions, number of nozzles, nozzle area and liquid flow rate are provided.

scholarly journals Experimental Heat Transfer Investigation of Stationary and Orthogonally Rotating Asymmetric and Symmetric Heated Smooth and Turbulated Channels

1992 ◽  
Author(s):  
H. A. El-Husayni ◽  
M. E. Taslim ◽  
D. M. Kercher
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Rotation Number ◽  
Symmetric Case ◽  
Wall Heat Flux ◽  
Heated Wall ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Smooth Channel

An experimental investigation was conducted to determine the effects of variations in wall thermal boundary conditions on local heat transfer coefficients in stationary and orthogonally rotating smooth wall and two opposite-wall turbulated square channels. Results were obtained for three distributions of uniform wall heat flux: asymmetric, applied to the primary wall only; symmetric, applied to two opposite walls only; and fully-symmetric, applied to all four channel walls. Measured stationary and rotating smooth channel average heat transfer coefficients at channel location L/Dh = 9.53 were not significantly sensitive to wall heat flux distributions. Trailing side heat transfer generally increased with Rotation number whereas the leading wall results showed a decreasing trend at low Rotation numbers to a minimum and then an increasing trend with further increase in Rotation number. The stationary turbulated wall heat transfer coefficients did not vary markedly with the variations in wall heat flux distributions. Rotating leading wall heat transfer decreased with Rotation number and showed little sensitivity to heat flux distributions except for the fully-symmetric heated wall case at the highest Reynolds number tested. Trailing wall heat transfer coefficients were sensitive to the thermal wall distributions generally at all Reynolds numbers tested and particularly with increasing Rotation number. While the asymmetric case showed a slight deficit in trailing wall heat transfer coefficients due to rotation, the symmetric case indicated little change whereas the fully-symmetric case exhibited an enhancement.

MEMS Impinging-Jet Cooling

2000 ◽  
Author(s):  
Qiao Lin ◽  
Shuyun Wu ◽  
Yin Yuen ◽  
Yu-Chong Tai ◽  
Chin-Ming Ho
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Measured Temperature ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Jet Cooling

Abstract This paper presents an experimental investigation on MEMS impinging jets as applied to micro heat exchangers. We have fabricated MEMS single and array jet nozzles using DRIE technology, as well as a MEMS quartz chip providing a simulated hot surface for jet impingement. The quartz chip, with an integrated polysilicon thin-film heater and distributed temperature sensors, offers high spatial resolution in temperature measurement due to the low thermal conductivity of quartz. From measured temperature distributions, heat transfer coefficients are computed for single and array micro impinging jets using finite element analysis. The results from this study for the first time provide extensive data on spatial distributions of micro impinging-jet heat transfer coefficients, and demonstrate the viability of MEMS heat exchangers that use micro impinging jets.

scholarly journals Heat transfer in fluidized and fixed beds of adsorption chillers

2019 ◽  
Vol 128 ◽  
pp. 01003 ◽  
Author(s):  
Jaroslaw Krzywanski ◽  
Karolina Grabowska ◽  
Marcin Sosnowski ◽  
Anna Zylka ◽  
Anna Kulakowska ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Fluidized Bed ◽  
Fluidized Beds ◽  
Fixed Bed ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Innovative Idea ◽  
Fixed Beds

An innovative idea, shown in the paper constitutes in the use of the fluidized bed of sorbent, instead of the conventional, fixed-bed, commonly used in the adsorption chillers. Bed–to–wall heat transfer coefficients for fixed and fluidized beds of adsorbent are determined. Sorbent particles diameters and velocities of fluidizing gas are discussed in the study. The calculations confirmed, that the bed–to–wall heat transfer coefficient in the fluidized bed of adsorbent is muchhigher than that in a conventional bed.

Experimental studies of helical coils in laminar regime for mechanically agitated vessel

2020 ◽  
Vol 234 (2) ◽  
pp. 173-181 ◽  
Author(s):  
Ansar Ali SK ◽  
Pardeep Kumar ◽  
Sandeep Kumar
Keyword(s):  
Heat Transfer ◽  
Experimental Studies ◽  
Methyl Cellulose ◽  
Newtonian Fluids ◽  
Laminar Regime ◽  
Transfer Coefficients ◽  
Dean Number ◽  
Agitated Vessel ◽  
Heat Transfer Coefficients ◽  
Helical Coils

The aim of this experimental study is to determine the heat transfer coefficients in laminar regime of mechanically agitated vessel for Newtonian (water) and non-Newtonian fluids, i.e. CMC (carboxy methyl cellulose) solutions in mechanically agitated vessel. It is found that Dean number and Prandtl number play an important role with Nusselt number while determining heat transfer coefficients. Modified Wilson plot is used to find heat transfer. The effect of friction factor on Reynolds number is also studied. The laminar flow heat transfer results have been successfully correlated in the following form with 15% standard deviation and this equation is suitable for the correlation for both Newtonian and non-Newtonian fluids to find heat transfer coefficients in helical coils in mechanically agitated stirred vessel.

Hole Staggering Effect on the Cooling Performance of Narrow Impingement Channels Using the Transient Liquid Crystal Technique

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Alexandros Terzis ◽  
Guillaume Wagner ◽  
Jens von Wolfersdorf ◽  
Peter Ott ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Jet Impingement ◽  
Transfer Coefficients ◽  
Noticeable Effect ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Cooling Hole ◽  
Turbine Airfoils ◽  
Transient Liquid Crystal Technique

This study examines experimentally the cooling performance of narrow impingement channels as could be cast-in in modern turbine airfoils. Full surface heat transfer coefficients are evaluated for the target plate and the sidewalls of the channels using the transient liquid crystal technique. Several narrow impingement channel geometries, consisting of a single row of five cooling holes, have been investigated composing a test matrix of nine different models. The experimental data are analyzed by means of various post-processing procedures aiming to clarify and quantify the effect of cooling hole offset position from the channel centerline on the local and average heat transfer coefficients and over a range of Reynolds numbers (11,100–86,000). The results indicated a noticeable effect of the jet pattern on the distribution of convection coefficients as well as similarities with conventional multi-jet impingement cooling systems.

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