scholarly journals The study of spray impact on the heated sapphire plate

2021 ◽  
Vol 2119 (1) ◽  
pp. 012172
Author(s):  
T G Gigola ◽  
V V Cheverda
Keyword(s):  
Heat Transfer ◽  
Sapphire Substrate ◽  
Substrate Surface ◽  
Heated Surface ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Liquid Spray ◽  
Sapphire Plate

Abstract The process of the liquid spray impact on the heated surface is studied experimentally using the IR-transparent sapphire plate method. The spatiotemporal distribution of the temperature field on the sapphire substrate surface during impacting spray is received. The obtained experimental data are an important step in a study of the local characteristics of heat transfer in the areas of the contact lines during liquid spray impact on the heated surface. Further, the local heat fluxes and heat transfer coefficients will be determined by solving the problem of thermal conductivity in the sapphire substrate.

The Transition From Turbulent to Laminar Gas Flow in a Heated Pipe

1970 ◽  
Vol 92 (4) ◽  
pp. 569-579 ◽  
Author(s):  
C. A. Bankston
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Heat Fluxes ◽  
External Boundary ◽  
Transfer Coefficients ◽  
Adiabatic Flow ◽  
Heat Transfer Coefficients

Experimental results are reported on the heat transfer and fluid friction of heated hydrogen and helium gas flows undergoing transition from turbulent to laminar flow in a circular tube. The entering Reynolds numbers range from 2350 to 12,500 and the nondimensional heat-flux parameter ranges from 0.0021 to 0.0061. Local heat-transfer coefficients and friction factors are obtained, and the flow transition, which is evident in these results, is verified at small heat fluxes by measuring directly the turbulence intensity at the center line with a hot-wire anemometer. At large heat fluxes, laminarization is found to occur at local bulk Reynolds numbers well in excess of the minimum number for fully turbulent adiabatic flow, and the resulting heat-transfer coefficients are much lower than those associated with fully turbulent flow at the same Reynolds number. The relation between laminarization in heated tubes and in severely accelerated external boundary layers is investigated and some similarities are noted. The acceleration and pressure-gradient parameters used to predict boundary-layer laminarization are modified for tube flow and used to correlate the initiation and completion of laminarization in the heated tube.

Local Heat Transfer Coefficients Measurement Under Micro Jet Impinging Using Nitrogen Gas (N2)

2016 ◽  
Author(s):  
Jeong-Heon Shin ◽  
Tomer Rozenfeld ◽  
Ashwin Vutha ◽  
Yingying Wang ◽  
Gennady Ziskind ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Fluxes ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Nitrogen Gas ◽  
Heat Transfer Coefficients ◽  
Temperature Detector

Experimental and simulation studies were performed to reveal local heat transfer coefficients under jet impinging in micro domain with Nitrogen gas. The experimental device was made of a 500 μm thick Pyrex and 400 μm thick silicon wafers. On the Pyrex wafer, four 100 nm thick resistance temperature detector (RTD) thermistors and a heater were fabricated from titanium. Jet orifices were etched by deep reactive ion etching (DRIE) on a silicon wafer, which was attached to the Pyrex wafer through a vinyl sticker (250 μm thick). A 1.9 mm × 14.8 mm × 250 μm micro channel was formed by laser drilling into the sticker. Varying flow rates of Nitrogen gas and heat fluxes of the heater, temperatures of the four thermistors were collected and local heat transfer coefficients were inferred enabling to divulge the jet impinging cooling characteristics. Initial simulations were used to complement experiments and to obtain detailed flow patterns of the jet, temperature distribution on the heater area, and fluid temperature distribution.

Experimental Study of Flow Boiling Heat Transfer in Mini-Tube

2005 ◽  
Author(s):  
Lihong Wang ◽  
Min Chen ◽  
Manfred Groll
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Saturation Pressure ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow Boiling Heat Transfer

Flow boiling heat transfer characteristics of R134a were experimentally investigated in a horizontal stainless steel mini-tube. The inner diameter of the test tube is 1.3 mm and the tube wall thickness is 0.1 mm. Local heat transfer coefficients are obtained over a range of vapor qualities up to 0.8, mass fluxes from 310 to 860 kg/m2s, heat fluxes from 21 to 50 kW/m2, and saturation pressures from 6.5 to 7.5 bar. The mass flux, heat flux, saturation pressure, and vapor quality dependences of heat transfer coefficients are demonstrated. Based on an available model in recent literature potential heat transfer mechanisms are also analyzed.

A Parametric Study of Boiling Heat Transfer in a Horizontal Tube Bundle

1988 ◽  
Vol 110 (4a) ◽  
pp. 976-981 ◽  
Author(s):  
M. K. Jensen ◽  
J.-T. Hsu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Tube Bundle ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Boiling heat transfer outside of a section of a uniformly heated horizontal tube bundle in an upward crossflow was investigated using R-113 as the working fluid. The inline tube bundle had five columns and 27 rows with a pitch-to-diameter ratio of 1.3. Heat transfer coefficients obtained from the 14 instrumented tubes are reported for a range of fluid and flow conditions; slightly subcooled liquid inlet conditions were used. At most heat fluxes there was no significant variation in the local heat transfer coefficients throughout the tube bundle. However, at low heat fluxes and mass velocities, the heat transfer coefficient increased at positions higher in the tube bundle. As pressure and mass velocity increased so did the heat transfer coefficients. For the local heat transfer coefficient, a Chen-type correlation is compared to the data; the data tend to be overpredicted by about 20 percent. Reasons for the overprediction are suggested.

Correlation of Heat Transfer Data to Film Thickness Data of the Thin Film Found in Spray Cooling

2004 ◽  
Author(s):  
Adam G. Pautsch ◽  
Timothy A. Shedd
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Film Thickness ◽  
Heated Surface ◽  
Spray Cooling ◽  
Heat Fluxes ◽  
Experimental Measurements ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients

As electronic circuit design and packaging technology progresses, the density and power levels of electronic components is increasing at a nearly exponential rate. The higher heat loads dissipated by these devices are nearing the limits of traditional cooling techniques. One method capable of removing heat fluxes as high as 100 W/cm2 is spray cooling. This process involves the impingement of liquid droplets onto a heated surface, forming a thin two-phase film. In order to create reliable models of the heat transfer during spray cooling, the behavior of the film must be understood. This paper presents an investigation into the behavior of the thin film found in spray cooling. A study was performed to relate experimental measurements of the heat transfer coefficients to experimental measurements of film thickness as they vary spatially over a die surface. Both a single nozzle and a multi-nozzle array were investigated. Measured heat transfer coefficients ranged from 0.2 to 1.2 W/m2K and film thicknesses ranged from 90 to 300 μm.

Pool Boiling Heat Transfer Characteristics of HFO-1234yf on Plain and Microporous-Enhanced Surfaces

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Gilberto Moreno ◽  
Sreekant Narumanchi ◽  
Charles King
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Heated Surface ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Automotive Air Conditioning ◽  
Hfc 134A ◽  
Lower Heat

This study characterizes the pool boiling performance of HFO-1234yf (hydrofluoroolefin 2,3,3,3-tetrafluoropropene). HFO-1234yf is a new, environmentally friendly refrigerant likely to replace HFC-134a in automotive air-conditioning systems. Pool boiling experiments were conducted at system pressures ranging from 0.7 to 1.7 MPa using horizontally oriented 1-cm2 heated surfaces. Test results for pure (oil-free) HFO-1234yf and HFC-134a were compared. The results showed that the boiling heat transfer coefficients of HFO-1234yf and HFC-134a were nearly identical at lower heat fluxes. HFO-1234yf yielded lower heat transfer coefficients at higher heat fluxes and lower critical heat flux (CHF) values as compared with HFC-134a. To enhance boiling heat transfer, a copper microporous coating was applied to the test surfaces. The coating enhanced both the boiling heat transfer coefficients and CHF for both refrigerants at all tested pressures. Increasing pressure decreased the level of heat transfer coefficient enhancements and increased the level of CHF enhancements. The experimental data were then used to develop a correlation for predicting the CHF for a smooth/plain heated surface.

The Effect of Regulating Elements on Convective Heat Transfer along Shaped Heat Exchange Surfaces

2013 ◽  
Vol 34 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Jozef Cernecky ◽  
Jan Koniar ◽  
Zuzana Brodnianska
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Cfd Simulation ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
Heat Transfer Intensification ◽  
Heat Transfer Coefficients ◽  
Forced Air

Abstract The paper deals with a study of the effect of regulating elements on local values of heat transfer coefficients along shaped heat exchange surfaces with forced air convection. The use of combined methods of heat transfer intensification, i.e. a combination of regulating elements with appropriately shaped heat exchange areas seems to be highly effective. The study focused on the analysis of local values of heat transfer coefficients in indicated cuts, in distances expressed as a ratio x/s for 0; 0.33; 0.66 and 1. As can be seen from our findings, in given conditions the regulating elements can increase the values of local heat transfer coefficients along shaped heat exchange surfaces. An optical method of holographic interferometry was used for the experimental research into temperature fields in the vicinity of heat exchange surfaces. The obtained values correspond very well with those of local heat transfer coefficients αx, recorded in a CFD simulation.

scholarly journals Pool Boiling Heat Transfer Coefficients in Mixtures of Water and Glycerin

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 830
Author(s):  
Viktor Vajc ◽  
Radek Šulc ◽  
Martin Dostál
Keyword(s):  
Heat Transfer ◽  
Dynamic Method ◽  
Water Mass ◽  
Heat Fluxes ◽  
Static Method ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mean Relative Error ◽  
Mixture Effects ◽  
Mass Fractions

Heat transfer coefficients were investigated for saturated nucleate pool boiling of binary mixtures of water and glycerin at atmospheric pressure in a wide range of concentrations and heat fluxes. Mixtures with water mass fractions from 100% to 40% were boiled on a horizontal flat copper surface at heat fluxes from about 25 up to 270kWm−2. Experiments were carried out by static and dynamic method of measurement. Results of the static method show that the impact of mixture effects on heat transfer coefficient cannot be neglected and ideal heat transfer coefficient has to be corrected for all investigated concentrations and heat fluxes. Experimental data are correlated with the empirical correlation α=0.59q0.714+0.130ωw with mean relative error of 6%. Taking mixture effects into account, data are also successfully correlated with the combination of Stephan and Abdelsalam (1980) and Schlünder (1982) correlations with mean relative error of about 15%. Recommended coefficients of Schlünder correlation C0=1 and βL=2×10−4ms−1 were found to be acceptable for all investigated mixtures. The dynamic method was developed for fast measurement of heat transfer coefficients at continuous change of composition of boiling mixture. The dynamic method was tested for water–glycerin mixtures with water mass fractions from 70% down to 35%. Results of the dynamic method were found to be comparable with the static method. For water–glycerin mixtures with higher water mass fractions, precise temperature measurements are needed.

Sign in / Sign up

Export Citation Format

Share Document