A Thermo-Hydraulic Investigation of the Unprecedented TMRS Upper Neutron Spallation Target

2021 ◽  
pp. 1-35
Author(s):  
Matthew Scheel ◽  
Keith Woloshun ◽  
Eric Olivas
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Flow Loop ◽  
Spallation Target ◽  
Target Station ◽  
Peak Heat Flux

Abstract The next-generation neutron spallation target station, the Target-Moderator-Reflector System (TMRS) Mk. IV, will be installed in 2021. This iteration features an unprecedented, water-cooled, third internal target aptly named the Upper Target. With the Upper Target designed completely by analysis, a complementary empirical investigation was undertaken to ascertain target conformance to those computational results which deemed the cooling efficacious. Three facets of the target were designated for verification: displacement under hydraulic load, critical fluid velocities, and the characteristic heat transfer coefficient. With the potential for flow maldistribution under excessive displacements, static pressure testing was performed. Discrepancies of an order of magnitude became evident between empirical and simulated displacements, 1.499 mm vs. 0.203 mm, respectively. A closed water flow loop reproducing the flow parameters intrinsic to the TMRS Mk. IV was constructed. Utilizing particle image velocimetry, global fluid dynamics were observed to be analogous to computer simulation. Furthermore, crucial velocities such as those at the point of beam impingement were met or exceeded, thus satisfying cooling requirements by preponderance. A graphite susceptor mirroring nominal beam geometry was coupled to a solenoid coil to replicate a prodigious peak heat flux of 169 W/cm2 via induction heating. Matching peak heat flux within 3% engendered a heat transfer coefficient 80% that of simulation. Consistent with analysis, the local heat transfer coefficient sufficiently mitigated nucleate/flow boiling. In summary, the analytically-derived Upper Target design empirically demonstrated sufficient cooling despite quixotic beam conditions and unforeseen displacements.

Flow Boiling Inside a Single Circular Minichannel: Measurement of Local Heat Transfer Coefficient

2007 ◽  
Author(s):  
Alberto Cavallini ◽  
Stefano Bortolin ◽  
Davide Del Col ◽  
Marko Matkovic ◽  
Luisa Rossetto
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Experimental Apparatus ◽  
Boiling Process

This paper describes a new experimental apparatus for the measurement of the local heat transfer coefficient during flow boiling inside a 0.96 mm internal diameter single round cross section minichannel and reports preliminary heat transfer data taken during flow boiling of R134a. As a peculiar characteristic of the present technique, the heat transfer coefficient is not measured by imposing the heat flux; instead, the boiling process is governed by controlling the inlet temperature of the heating secondary fluid. This paper also presents a methodology to determine the critical conditions during the flow boiling process when no heat flux is imposed.

Experimental and Numerical Analyses of R134a Flow Boiling Heat Transfer Characteristics in an Evaporator Tube of Refrigeration System

2019 ◽  
Vol 27 (03) ◽  
pp. 1950024
Author(s):  
Zahraa Kareem Yasser ◽  
Ahmed J. Hamad
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Refrigeration System ◽  
Heat Transfer Characteristics

The heat transfer characteristics of R134a flow boiling in a horizontal tube of an evaporator section for a refrigeration system of 310-W capacity are investigated experimentally and numerically. The experimental work was conducted using an evaporator tube test section of inner diameter 5.8[Formula: see text]mm and length 600[Formula: see text]mm. The ranges of investigated experimental data for heat flux, mass flux, saturation temperature and vapor quality were 13.8–36.6[Formula: see text]kW/m2, 52–105[Formula: see text]kg/m2[Formula: see text][Formula: see text][Formula: see text]s, [Formula: see text]–[Formula: see text]C and 0.2–1, respectively. Numerical analysis was based on two-phase flow turbulent model and this model was solved using the Ansys-18 code. The results showed that the effects of heat flux, mass velocity and saturation temperature on local heat transfer coefficient and pressure drop were greater compared to that of the refrigerant vapor quality. The enhancements in local heat transfer coefficient due to the increase in heat flux, mass and saturation temperature were 38%, 57% and 64%, respectively, within the prescribed test conditions. The influence of mass flux variation on pressure drop along the evaporator channel was higher in the range of 27% compared to the heat flux effect. The average deviations between experimental and numerical results of heat transfer coefficient and pressure gradient were 14% and 17%, respectively, while the same between the experimental and predicted results were 16% and 33%, respectively.

Flow Boiling Heat Transfer on Micro Pin Fins Entrenched in a Microchannel

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Santosh Krishnamurthy ◽  
Yoav Peles
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Fluxes ◽  
Axial Distance ◽  
Mass Fluxes ◽  
Pin Fins

Flow boiling of 1-methoxyheptafluoropropane (HFE 7000) in 222 μm hydraulic diameter channels containing a single row of 24 inline 100 μm pin fins was studied for mass fluxes from 350 kg/m2 s to 827 kg/m2 s and wall heat fluxes from 10 W/cm2 to 110 W/cm2. Flow visualization revealed the existence of isolated bubbles, bubbles interacting, multiple flow, and annular flow. The observed flow patterns were mapped as a function of the boiling number and the normalized axial distance. The local heat transfer coefficient during subcooled boiling was measured and found to be considerably higher than the corresponding single-phase flow. Furthermore, a thermal performance evaluation comparison with a plain microchannel revealed that the presence of pin fins considerably enhanced the heat transfer coefficient.

Local Heat Transfer Coefficient of Flow Boiling in Microchannels With Artificial Reentrant Cavities

2007 ◽  
Author(s):  
Chih-Jung Kuo ◽  
Yoav Peles
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Bubble Generation ◽  
Parallel Microchannels

Flow boiling in parallel microchannels with structured reentrant cavities was experimental studied. Flow patterns, boiling inceptions and heat transfer coefficients were obtained and studied for G = 83 kg/m2-s to G = 303 kg/m2-s and heat fluxes up to 643 W/cm2. The heat transfer coefficient-mass velocity and quality relations had been analyzed to identify boiling mechanism. Comparisons of the performance of the enhanced and plain-wall microchannels had also been made. The microchannels with reentrant cavities were shown to promote nucleation of bubbles and to support significantly better reproducibility and uniformity of bubble generation.

Experimental Study on Flow Boiling of HFC134a in a Multi-Port Extruded Tube

2004 ◽  
Author(s):  
Ken Kuwahara ◽  
Shigeru Koyama ◽  
Kengo Kazari
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Rectangular Channel ◽  
Large Diameter ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Inlet Temperature

In the present study, the local heat transfer and pressure drop characteristics are investigated experimentally for the flow boiling of refrigerant HFC134a in a multi-port extruded tube of 1.06mm in hydraulic diameter. The test tube is 865mm in total length made of aluminum. The pressure drop is measured at an interval of 191 mm, and the local heat transfer coefficient is measured in every subsection of 75mm in effective heating length. Experimental ranges are as follows: the mass velocity of G = 100–700 kg/m2s, the inlet temperature of Tin = 5.9–11.4 °C and inlet pressure of about 0.5 MPa. The data of pressure drop are compared with a few previous correlations for small diameter tubes, and the correlations can predict the data relatively good agreement. The data of heat transfer coefficient is compared with the correlations of Yu et al. proposed for relatively large diameter tubes. It is found that there are some differences about two phase multiplier factor of convective heat transfer between the circular channel and rectangular channel.

The Effect of Inlet Orifice on Critical Heat Flux and Flow Boiling Heat Transfer in Single Horizontal Microtube

2013 ◽  
Author(s):  
Yanfeng Fan ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Saturation Pressure ◽  
Working Fluid ◽  
Flow Boiling Heat Transfer

Flow oscillation is a crucial issue for the development of flow boiling heat transfer in the applications. Inlet orifice has been proven be an option to eliminate the oscillation. However, the effects of inlet orifice on critical heat flux and flow boiling heat transfer coefficient are lack of study. In this work, the effects of inlet restriction on critical heat flux and heat transfer coefficient in single horizontal microtube under uniform heating condition is experimentally investigated using FC-72 as working fluid. A stainless steel microtube with an inner diameter of 889 μm is selected as main microtube. Two smaller microtubes are assembled at the inlet of main microtube to achieve the restriction configurations of 50% and 20% area ratios. The experimental measurement is carried out at mass fluxes ranging from 160–870 kg/m2·s and heat fluxes varying from 6–170 kW/m2. Two saturation pressures, 10 and 45 kPa, are tested. The experimental results of critical heat flux and two phase heat transfer coefficient obtained in the microtube without orifice are compared with the existing correlations. The addition of an orifice does not enhance the normal critical heat flux but increases the premature critical heat flux. In aspect of heat transfer, the orifice shows improvement on heat transfer coefficient at low mass flux and high saturation pressure.

Flow Boiling Heat Transfer of R-22 in Small-Diameter Horizontal Round Tubes

2003 ◽  
Author(s):  
K. S. Park ◽  
W. H. Choo ◽  
K. H. Bang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Vapor Quality ◽  
Flow Boiling Heat Transfer ◽  
Boiling Heat Transfer Coefficient

The flow boiling heat transfer coefficient of R-22 in small hydraulic diameter tubes has been experimentally studied. Both brass and aluminum round tubes of 1.66 mm inside diameter are used for the test section. The ranges of the major experimental parameters are 300∼600 kg/m2s of refrigerant mass flux, 10∼20 kW/m2 of the wall heat flux, 0.0∼0.9 of the inlet vapor quality. The experimental result showed that the flow boiling heat transfer coefficient in this small tubes are in the range of 2∼4 kW/m2K and it varies only by heat flux, independent of mass flux and vapor quality. It is also observed that the heat transfer coefficients in the aluminum tube are up to 50% higher than in the brass tube.

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