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.

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.

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.

Distribution of local heat transfer coefficient values in the wall region of an agitated vessel

2008 ◽  
Vol 62 (1) ◽  
Author(s):  
Magdalena Cudak ◽  
Joanna Karcz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Regime ◽  
Transfer Coefficients ◽  
Measuring Point ◽  
Agitated Vessel ◽  
Heat Transfer Coefficients

AbstractExperimentally found local heat transfer coefficients are analyzed as a function of the measuring point on the heat transfer surface area of the agitated vessel wall and of the impeller eccentricity. Eccentric Rushton turbine and A 315 impeller are considered. Local heat transfer coefficients were measured by means of the computer-aided electrochemical method. The measurements were performed in an agitated vessel with inner diameter 0.3 m, filled with liquid up to the height equal to the vessel diameter. The experiments were carried out within the turbulent regime of the Newtonian liquid flow in the agitated vessel. The results were compared with the data obtained for the agitated vessel equipped with an eccentrically located axial flow propeller or an HE 3 impeller. Experimental studies show that the distributions of the heat transfer coefficient values depend on the impeller eccentricity, impeller type and the direction of the liquid circulation in the agitated vessel.

scholarly journals To the determination of heat exchange conditions near the inner surface of walls with reflective thermal insulation from aluminium foil

2018 ◽  
Vol 196 ◽  
pp. 02035 ◽  
Author(s):  
Nina Umnyakova ◽  
Mikhail Gandzhuntsev
Keyword(s):  
Heat Transfer ◽  
Thermal Insulation ◽  
Experimental Studies ◽  
Building Envelope ◽  
Surface Radiation ◽  
Thermal Engineering ◽  
Transfer Coefficients ◽  
Concrete Wall ◽  
Heat Transfer Coefficients ◽  
Inner Surface

Materials with a low coefficient of surface radiation intensively reflect the radiant component of the heat flux and reduce heat losses through the building envelope. When designing building structures with reflective thermal insulation it is necessary to evaluate the efficiency of its application. However, at present there are no methods for calculating the value of thermal losses through external walls in the presence of reflective thermal insulation on internal surface of the wall, as well as there are no data on the values of heat transfer coefficients at the inner surface of building envelope with reflective thermal insulation. In this regard, in the climatic chambers of NIISF RAABS, complex thermal engineering studies were carried out. For this a cellular concrete wall 2,8 x1,2 m was put up into the chamber with reflective thermal insulation on the inner surface and without it. The obtained results of experimental studies, presented in the work, allowed obtaining numerical values of heat transfer coefficients at the inner surface of walls with reflective thermal insulation, and use the obtained data in further calculations.

scholarly journals Modeling of the heat transfer process in an air heat pump fanless evaporator

2018 ◽  
Vol 240 ◽  
pp. 05012
Author(s):  
Piotr Kopeć ◽  
Beata Niezgoda-Żelasko
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Mixed Convection ◽  
Heat Pump ◽  
Transfer Process ◽  
Experimental Studies ◽  
Heat Transfer Process ◽  
Cfd Modeling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

This paper analyses the mixed convection process in a fanless evaporator of an air heat pump. The text of the paper shows the authors’ experimental studies results of the temperature distribution and the local values of heat transfer coefficients on the outer surface of vertical tubes with longitudinal fins for the case of mixed convection and fins of a specific shape of their cross-section (prismatic, wavy fins). The experimental studies include the air velocities wa=2,3 m/s and the temperature differences between air and the refrigerant inside the heat exchanger tubes which is ΔT=24-40K. The results obtained were used for verification of CFD modeling of the heat transfer process for the discussed case of heat transfer and the geometry of the finned surface. The numerical analysis was performed for: the temperature distribution along the fin height, the tube perimeter and height, the distribution of local heat transfer coefficients on the finned tube perimeter and along its height. The simulated calculations were used to verify the method of determination of fin efficiency.

Computational and Experimental Studies of Midpassage Gap Leakage and Misalignment for a Non-Axisymmetric Contoured Turbine Blade Endwall

2016 ◽  
Author(s):  
Eric Lange ◽  
Stephen Lynch ◽  
Scott Lewis
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Computational Study ◽  
Experimental Studies ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Recirculation Region ◽  
Leakage Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Turbine vanes and blades are generally manufactured as single or double airfoil sections that must each be installed onto a turbine disk. Between each section, a gap at the endwalls through the blade passage is present, through which high pressure coolant is leaked. Furthermore, sections can become misaligned due to thermal expansion or centrifugal forces. Flow and heat transfer around the gap is complicated due to the interaction of the mainstream and the leakage flow. An experimental and computational study was undertaken to determine the physics of the leakage flow interaction for a realistic turbine blade endwall, and assess whether steady RANS CFD, commonly used for non-axisymmetric endwall design, can be used to accurately model this interaction. Computational models were compared against experimental observations of endwall heat transfer on a contoured endwall with a midpassage gap. Endwall heat transfer coefficients were determined experimentally by using infrared thermography to capture spatially-resolved surface temperatures on a uniform heat flux surface (heater) attached to the endwall. Predictions and measurements both indicated an increase in endwall heat transfer with increasing gap leakage flow, although the distribution of heat transfer coefficients along the gap was not well captured by CFD. A misalignment of the blade endwall causing a forward-facing step for the near-endwall flow resulted in a large highly turbulent recirculation region downstream of the step and high local heat transfer that was overpredicted by CFD. Conversely, a backward-facing step reduced turbulence and local heat transfer. The misprediction of local heat transfer around the gap is thought to be caused by unsteady interaction of the passage secondary flow and gap leakage flow, which cannot be well-captured by a steady RANS approach.

scholarly journals EXPERIMENTAL STUDIES OF THERMAL TRANSMISSION THROUGH A MOBILE HEAT EXCHANGE SURFACE

2020 ◽  
Vol 2018 (1) ◽  
pp. 28-31
Author(s):  
Borislav Kustov ◽  
Mihail Gerasimchuk
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Flow Rate ◽  
Experimental Studies ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heat Exchange Surface ◽  
Thermal Transmission ◽  
Exchange Surface

Experimental studies of heat transfer in a heat exchanger of the "pipe-in-pipe" type with a rotating tube have been performed. It is established that in the investigated range of hot coolant flow rate, the rotation of the pipe makes it possible to increase the values of the heat transfer coefficients by 19-28%.

scholarly journals Modeling of the Two-Dimensional Thawing of Logs in an Air Environment

2020 ◽  
Author(s):  
Nencho Deliiski ◽  
Ladislav Dzurenda ◽  
Natalia Tumbarkova
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Experimental Studies ◽  
Longitudinal Section ◽  
Nonstationary Temperature ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Finite Difference Method

A two-dimensional mathematical model has been created, solved, and verified for the transient nonlinear heat conduction in logs during their thawing in an air environment. For the numerical solution of the model, an explicit form of the finite-difference method in the computing medium of Visual FORTRAN Professional has been used. The chapter presents solutions of the model and its validation towards own experimental studies. During the validation of the model, the inverse task of the heat transfer has been solved for the determination of the logs’ heat transfer coefficients in radial and longitudinal directions. This task has been solved also in regard to the logs’ surface temperature, which depends on the mentioned coefficients. The results from the experimental and simulative investigation of 2D nonstationary temperature distribution in the longitudinal section of poplar logs with a diameter of 0.24 m, length of 0.48 m, and an initial temperature of approximately –30°C during their many hours thawing in an air environment at room temperature are presented, visualized, and analyzed.

Sign in / Sign up

Export Citation Format

Share Document