On Calculating Heat Transfer and Pressure Drop of Supercritical-Pressure Coolants

2016 ◽  
Vol 2 (3) ◽  
Author(s):  
Vladimir A. Kurganov ◽  
Yuri A. Zeigarnik ◽  
Irina V. Maslakova
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Thermophysical Properties ◽  
High Heat ◽  
Supercritical Pressure ◽  
Heat Transfer Deterioration ◽  
Normal Heat ◽  
Turbulent Flow Structure ◽  
Heat Loads

Specific features of thermophysical properties of single-phase supercritical-pressure (SCP) coolants and typical ranges of their thermodynamic state that determine heat-transfer regularities are presented. A brief analysis of the existing concepts on SCP-coolants heat transfer under turbulent flow in tube is given. Typical features of normal and deteriorated heat-transfer regimes are described. The simple classification of deteriorated heat-transfer regimes at high heat loads that make it possible to distinguish the causes and appraise a degree of heat-transfer deterioration danger is proposed. The results from the studies of the hydraulic-resistance structure under the regimes of normal and deteriorated heat transfer are considered and the conditions, when a one-dimensional (1-D) (homogeneous) flow model can be used in hydraulic calculations, are revealed. Using sounding measurements data, the interrelation between heat-transfer deterioration and radical changes in the averaged turbulent flow structure due to fluid thermal acceleration and Archimedes forces effects is analyzed. The recommendations on calculating normal heat transfer with an account of refined standards on thermophysical properties of water and carbon dioxide are presented. The review and analysis of the existing criteria for forecasting heat-transfer deterioration and assessing the boundaries of the normal heat-transfer range are given, and the correlations for describing deteriorated heat transfer are presented.

Normal and Deteriorated Heat Transfer Under Heating Turbulent Supercritical Pressure Coolants Flows in Round Tubes

2021 ◽  
pp. 494-532
Author(s):  
Vladimir A. Kurganov ◽  
Yury A. Zeigarnik ◽  
Irina V. Maslakova
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Thermophysical Properties ◽  
High Heat ◽  
Supercritical Pressure ◽  
Drop Method ◽  
New Correlation ◽  
Normal Heat ◽  
Heat Loads

Heat transfer to a turbulent flow of supercritical pressure (SCP) fluids under intense heating conditions is considered. The problem of heat transfer deteriorating under high heat loads and the reasons of its origination are analyzed. The results of hydraulic measurements in a flow and its structure using “two pressure drop” method and sounding technique in the regimes of normal and deteriorated heat transfer are presented. The existed correlations on normal heat transfer are analyzed and assessed as to their accuracy. It is pointed out that all the correlations developed using “old” thermophysical properties existed before implementing IAWPS-97 must be corrected. Respective recommendations on this problem and the new correlation for normal heat transfer are presented.

Effect of Buoyancy on the Mechanism of Heat Transfer Deterioration of Supercritical Water in Horizontal Tubes

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Xianliang Lei ◽  
Huixiong Li ◽  
Yifan Zhang ◽  
Weiqiang Zhang
Keyword(s):  
Heat Transfer ◽  
Supercritical Water ◽  
Wall Temperature ◽  
Thermophysical Properties ◽  
Supercritical Pressure ◽  
Axial Position ◽  
Bulk Fluid ◽  
Heat Transfer Deterioration ◽  
Horizontal Tubes ◽  
Pressure Water

In order to get insights into the mechanisms governing the heat transfer deterioration (HTD) of supercritical water, systematical numerical simulations were carried out in the present study for the flow and heat transfer of supercritical pressure water in horizontal smooth tubes. The numerical results were found in very good agreement with the corresponding experimental data, validating the reliability and accuracy of the numerical model and the computational method. It was found that from these profiles along the top generatrix of the wall of the horizontal tube, there exists a thin fluid layer in which the thermo-physical properties of the fluid, including the specific heat capacity, thermal conductivity, density and viscosity, all approach its minimum at a roughly identical axial position of the tube with the increasing of the bulk fluid enthalpy along the flow direction. The maximum wall temperature of the top generatrix, obviously show the occurrence of HTD. It was especially interesting that the axial position of the maximum top generatrix wall temperature (HTD position) just coincided with the axial positions of the minimum of the above-mentioned thermophysical properties in the near top generatrix layer, which reveals the inherent connection between the HTD and the minimum value of the above-mentioned thermophysical properties of the supercritical water. It was concluded that the HTD of supercritical water in horizontal tubes was evidently due to the vertical stratification and the accumulation of light supercritical pressure fluid (very high enthalpy but low density) in the near top generatrix region. Also, the HTD phenomena under supercritical condition was similar to that of the film boiling of the subcritical pressure water. This result clearly reveals why the axial position of the HTD occurred on the top wall of horizontal tubes (with bulk fluid enthalpy of roughly 1750 kJ/kg) is axially far ahead of the position corresponding to the critical point of the supercritical water (with bulk fluid enthalpy of roughly 2150 kJ/kg) in terms of the bulk fluid enthalpy.

Enhancement of heat transfer in a square channel by roughened surfaces in rib-elements and turbulent flow manipulation

2017 ◽  
Vol 27 (7) ◽  
pp. 1571-1595 ◽  
Author(s):  
Jian Liu ◽  
Gongnan Xie ◽  
Bengt Ake Sunden ◽  
Lei Wang ◽  
Martin Andersson
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Research Work ◽  
Flow Characteristics ◽  
High Heat ◽  
The Novel ◽  
Content Type ◽  
Flat Surfaces ◽  
Square Channel ◽  
High Heat Transfer

Purpose The purpose of this paper is to augment heat transfer rates of traditional rib-elements with minimal pressure drop penalties. Design/methodology/approach The novel geometries in the present research are conventional cylindrical ribs with rounded transitions to the adjacent flat surfaces and with modifications at their bases. All turbulent fluid flow and heat transfer results are presented using computation fluid dynamics with a validated v2f turbulence closure model. Turbulent flow characteristics and heat transfer performances in square channels with improved ribbed structures are numerically analyzed in this research work. Findings Based on the results, it is found that rounded transition cylindrical ribs have a large advantage over the conventional ribs in both enhancing heat transfer and reducing pressure loss penalty. In addition, cylindrical ribs increase the flow impingement at the upstream of the ribs, which will effectively increase the high heat transfer areas. The design of rounded transition cylindrical ribs and grooves will be an effective way to improve heat transfer enhancement and overall thermal performance of internal channels within blade cooling. Originality/value The novel geometries in this research are conventional cylindrical ribs with rounded transitions to the adjacent flat surfaces and with modifications at their bases. The combination of cylindrical ribs and grooves to manipulate the turbulent flow.

scholarly journals Deterioration in Heat Transfer to Fluids at Supercritical Pressure and High Heat Fluxes

1969 ◽  
Vol 91 (1) ◽  
pp. 27-36 ◽  
Author(s):  
B. S. Shiralkar ◽  
Peter Griffith
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Heat ◽  
Supercritical Pressure ◽  
Heat Fluxes ◽  
Bulk Temperature ◽  
Operating Pressure ◽  
The Heat Transfer Coefficient

At slightly supercritical pressure and in the neighborhood of the pseudocritical temperature (which corresponds to the peak in the specific heat at the operating pressure), the heat transfer coefficient between fluid and tube wall is strongly dependent on the heat flux. For large heat fluxes, a marked deterioration takes place in the heat transfer coefficient in the region where the bulk temperature is below the pseudocritical temperature and the wall temperature above the pseudocritical temperature. Equations have been developed to predict the deterioration in heat transfer at high heat fluxes and the results compared with previously available results for steam. Experiments have been performed with carbon dioxide for additional comparison. Limits of safe operation for a supercritical pressure heat exchanger in terms of the allowable heat flux for a particular flow rate have been determined theoretically and experimentally.

Turbulent flow structure and heat transfer in an inclined bubbly flow. Experimental and numerical investigation

2017 ◽  
Vol 52 (1) ◽  
pp. 115-127 ◽  
Author(s):  
A. E. Gorelikova ◽  
O. N. Kashinskii ◽  
M. A. Pakhomov ◽  
V. V. Randin ◽  
V. I. Terekhov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Numerical Investigation ◽  
Flow Structure ◽  
Bubbly Flow ◽  
Turbulent Flow Structure

Experimental Investigation of Heat Transfer Augmentation by Different Jet Impingement Hole Shapes Under Maximum Crossflow

2016 ◽  
Author(s):  
Prashant Singh ◽  
Bharath Viswanath Ravi ◽  
Srinath Ekkad
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Jet Impingement ◽  
High Heat ◽  
Absolute Pressure ◽  
Target Plate ◽  
Heat Transfer Augmentation ◽  
Plate Spacing ◽  
High Heat Transfer ◽  
Heat Loads

To achieve higher overall efficiency in gas turbine engines, hot gas path components are subjected to high heat transfer loads due to higher turbine inlet temperatures. Jet impingement has been extensively used especially as an internal cooling technique in the leading edge and mid-chord region of first stage vanes, which are subjected to highest heat loads. With the advent of additive manufacturing methods such as Direct Metal Laser Sintering (DMLS), designers are not limited to designing round or race track holes for impingement. The present study is focused on exploring new jet hole shapes, in an arrangement, typical of mid-chord region in a double wall cooling configuration. Transient liquid crystal experiments are carried out to study heat transfer augmentation by jet impingement on smooth target where the spent air is allowed to exit in one direction, thus imposing maximum crossflow condition. The averaged Reynolds number (based on jet hydraulic diameter) is varied from 2500 to 10000. The jet plate has a square array of jets with 7 jets in one row (total number of jets = 49), featuring hole shapes — Racetrack and V, where the baseline case is the round hole. The non-dimensional streamwise (x/dj) and spanwise (y/dj) spacing is 6 and the normalized jet-to-target-plate spacing (z/dj) is 4 and the nozzle aspect ratio (L/dj) is also 4. The criteria for the hole shape design was to keep the effective area of different hole shapes to be the same, which resulted in slightly different hydraulic diameters. The jet-to-target plate spacing (z) has been adjusted accordingly so as to maintain a uniform z/dj of 4, across all three configurations studied. Heat transfer coefficients are measured using a transient Liquid Crystal technique employing a one-dimensional semi-infinite model. Flow experiments are carried out to measure static pressures in the plenum chamber, to calculate the discharge coefficient, for a range of plenum absolute pressure-to-ambient pressure ratios. Detailed normalized Nusselt number contours have been presented, to identify the regions of high heat transfer augmentation locally, so as to help the designers in the organization of jet hole shapes and their patterns in an airfoil depending upon the active heat loads.

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