Transient Heat Transfer During Cryogenic Chilldown

2005 ◽  
Author(s):  
Jelliffe Jackson ◽  
Jun Liao ◽  
James F. Klausner ◽  
Renwei Mei
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Structure ◽  
Flow Boiling ◽  
Superconducting Magnets ◽  
Nucleate Boiling ◽  
Transient Heat Transfer ◽  
Boiling Regime ◽  
The Heat Transfer Coefficient

Cryogenic fluids have found many practical applications in today’s world, from cooling superconducting magnets to fueling launch vehicles. In many of these applications the cryogenic fluid is initially introduced into piping systems that are in excess of 150 degrees Kelvin higher than the fluid. This leads to voracious evaporation of the fluid and significant pressure fluctuations, which is accompanied by thermal contraction of system components. This process is known as chilldown, and although it was first investigated more than 4 decades ago, very little data are available on the momentum and energy transport during this transient process. Consequently, the development of predictive models for the pressure drop and heat transfer coefficient has been hampered. In order to address this deficiency, an experimental facility has been constructed that enables the flow structure to be observed while temperatures and pressures at various locations are measured. This study focuses on the inverse numerical procedure used to extract the transient heat transfer coefficient information from the data collected; this information is then used to evaluate the performance of various correlations for heat transfer coefficient in the flow boiling regime. The method developed utilizes flow structure information and temperature measurements, in conjunction with numerical computations for the temperature field within the tube wall, to calculate the heat transfer coefficient. This approach allows the transition point between the film boiling regime and the nucleate boiling regime to be determined, and it also elucidates the variation of the heat transfer coefficient along the circumference of a horizontal tube, with the heat transfer on upper portion being significantly smaller than that at the bottom.

Study on Flow Boiling Heat Transfer of Carbon Dioxide With PAG-Type Lubricating Oil in Pre-Dryout Region Inside Horizontal Tube

2010 ◽  
Author(s):  
Chaobin Dang ◽  
Minxia Li ◽  
Eiji Hihara
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Flow Boiling Heat Transfer ◽  
The Heat Transfer Coefficient

In this study, the boiling heat transfer coefficients of carbon dioxide with a PAG-type lubricating oil entrained from 0 to 5 wt% in a horizontally placed smooth tube with an inner diameter of 2 mm were experimentally investigated under the following operating conditions: mass fluxes from 170 to 320 kg/m2s, heat fluxes from 4.5 to 36 kW/m2, and a saturation temperature of 15 °C. The results show that for a low oil concentration of approximately 0.5% to 1%, no further deterioration of the heat transfer coefficient was observed at higher oil concentrations in spite of a significant decrement of the heat transfer coefficient compared to that under an oil-free condition. The heat flux still had a positive influence on the heat transfer coefficient in low quality regions. However, no obvious influence was observed in high quality regions, which implies that nucleate boiling dominates in the low quality region whereas it is suppressed in the high quality regions. Unlike the mass flux under an oil-free condition, mass flux has a significant influence on the heat transfer coefficient, with a maximum increase of 50% in the heat transfer. On the basis of our experimental measurements of the flow boiling heat transfer of carbon dioxide under wide experimental conditions, a flow boiling heat transfer model for horizontal tubes has been proposed for a mixture of CO2 and polyalkylene glycol (PAG oil) in the pre-dryout region, with consideration of the thermodynamic properties of the mixture. The surface tension and viscosity of the mixture were particularly taken into account. New factors were introduced into the correlation to reflect the suppressive effects of the mass flux and the oil on both the nucleate boiling. It is shown that the calculated results can depict the influence of the mass flux and the heat flux on both nucleate boiling and convection boiling.

scholarly journals Comparative study of flow condensation in conventional and small diameter tubes

2012 ◽  
Vol 33 (2) ◽  
pp. 67-83 ◽  
Author(s):  
Dariusz Mikielewicz ◽  
Rafał Andrzejczyk
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Structure ◽  
Annular Flow ◽  
Flow Boiling ◽  
Small Diameter ◽  
Bubble Generation ◽  
Flow Condensation ◽  
The Heat Transfer Coefficient

Abstract Flow boiling and flow condensation are often regarded as two opposite or symmetrical phenomena. Their description however with a single correlation has yet to be suggested. In the case of flow boiling in minichannels there is mostly encountered the annular flow structure, where the bubble generation is not present. Similar picture holds for the case of inside tube condensation, where annular flow structure predominates. In such case the heat transfer coefficient is primarily dependent on the convective mechanism. In the paper a method developed earlier by the first author is applied to calculations of heat transfer coefficient for inside tube condensation. The method has been verified using experimental data from literature on several fluids in different microchannels and compared to three well established correlations for calculations of heat transfer coefficient in flow condensation. It clearly stems from the results presented here that the flow condensation can be modeled in terms of appropriately devised pressure drop.

Experimental Study on Flow Boiling of HFE-7100 in Wavy Copper Microchannels

2020 ◽  
Author(s):  
Peilin Cui ◽  
Zhenyu Liu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Thin Liquid Film ◽  
Bubbly Flow ◽  
Nucleate Boiling ◽  
Inlet Temperature ◽  
The Heat Transfer Coefficient

Abstract This study experimentally investigated the flow boiling of HFE-7100 in wavy copper microchannel heat sink (20 mm × 10 mm), which was fabricated with the ultrafast laser micromachining approach, consisting of 20 wavy microchannels with wavelength of 2000 μm and wave amplitude of 100 μm with triangular cross section (200 μm × 573 μm). The experiment was conducted with the mass fluxes of 330.07–550.11 kg/(m2·s) and heat flux of 14.5–411.3 kW/m2 at an inlet temperature of 15°C. Four flow patterns including bubbly flow, slug flow, churn flow and annular flow were captured with the visualization technique. Several confined bubbles with irregular shape were observed. In the low heat flux region, the dominant flow regime of heat transfer in the microchannels is the nucleate boiling and the heat transfer coefficient increases with increasing heat flux. With the nucleate boiling suppressed gradually, the evaporation of thin liquid film begins to dominate and the heat transfer coefficient decreases with the increase of heat flux. The heat flux has a significant effect on heat transfer coefficient compared with the mass flux and vapor quality.

Experimental Study of Flow Boiling Heat Transfer Coefficient of FC-72 Over Micro-Pin-Finned Surfaces

2010 ◽  
Author(s):  
Y. F. Xue ◽  
M. Z. Yuan ◽  
J. J. Wei
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Fluid Velocity ◽  
Nucleate Boiling ◽  
Flow Boiling Heat Transfer ◽  
Nucleate Boiling Heat Transfer ◽  
Boiling Heat Transfer Coefficient

Experiments of flow boiling heat transfer coefficient of FC-72 were carried out over simulated silicon chip of 10×10×0.5 mm3 for electronic cooling. Four kinds of micro-pin-fins with the dimensions of 30×60, 30×120, 50×60, 50×120 μm2 (thickness, t × height, h) respectively, were fabricated on the chip surfaces by the dry etching technique to enhance boiling heat transfer. A smooth chip was also tested for comparison. The experiments were conducted at three different fluid velocities (0.5, 1 and 2m/s) and three different liquid subcoolings (15, 25 and 35K). All micro-pin-finned surfaces show a considerable heat transfer enhancement compared to the smooth surface. Both the forced convection and nucleate boiling heat transfer contribute to the total heat transfer performance. The contribution of each factor to the total heat transfer has been clearly presented in the flow boiling heat transfer coefficient curves. In a lower heat flux region, the heat transfer coefficient increases greatly with increasing fluid velocity, but increases slightly with increasing heat flux, indicating that the single-phase forced convection dominates the heat transfer process. With further increasing heat flux to the onset of nucleate boiling, the heat transfer coefficient increases remarkably. For a given liquid subcooling, the curves of flow boiling heat transfer coefficient at fluid velocities of 0.5 and 1 m/s almost follow one line for each surface, showing insensitivity of nucleate boiling heat transfer to fluid velocity. However, at the largest fluid velocity of 2 m/s, the slope of the flow boiling heat transfer coefficient curves for micro-pin-finned surfaces becomes smaller, indicating that the forced convection also plays an important role besides the nucleate boiling heat transfer. The curves of the flow boiling heat transfer coefficient can be used to determine the boiling incipience at different fluid velocities, which provides a basis for the suitable fluid velocity selection in designing highly efficient cooling scheme for electronic devices.

Oil Effects on In-Tube Evaporation of CO2 by Altering Flow Regime and Properties

2013 ◽  
Author(s):  
Pega Hrnjak ◽  
Seongho Kim
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Circulation Rate ◽  
Convective Boiling ◽  
Mass Fluxes

Flow boiling heat transfer characteristics of CO2 with and without oil were investigated experimentally in horizontal smooth and enhanced tubes with an inner diameter of 11.2 mm. The visualization of flow pattern provides a detailed attributes of the nucleate and the convective boiling heat transfer. In order to investigate the effect of the miscible oil on the heat transfer of CO2, POE (polyolester) RENSIO C85E oil is added to give an oil circulation rate (OCR) between 0.5% and 2%. Results are compared with those of pure CO2. The experimental conditions include evaporation temperatures of −15 °C, mass fluxes from 40 to 200 kg/m2 s, heat fluxes from 0.5 to 10 kW/m2, and vapor qualities from 0.1 to 0.8. Oil generally deteriorates the heat transfer coefficient of pure CO2. The reduction in heat transfer coefficient is most apparent at low vapor qualities, 0.1 to 0.4, and at low mass fluxes, 100 and 200 kg/m2. It is caused by the suppression of nucleate boiling due to increased surface tension. At conditions where the convective boiling contribution is dominant, vapor qualities above 0.5, oil increases heat transfer coefficients. Through visualization, it is shown that the wetted area on the perimeter of inner tube is enhanced due to formation of foaming in the smooth tube. However, such enhancement of heat transfer due to forming is negligible in the enhanced tube, because the enhanced factor due to micro-finned structures is dominant.

scholarly journals Experimental Investigation of Flow Condensation in Microgravity

2013 ◽  
Author(s):  
Hyoungsoon Lee ◽  
Ilchung Park ◽  
Christopher Konishi ◽  
Issam Mudawar ◽  
Rochelle I. May ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Dissipation ◽  
Flow Boiling ◽  
Condensation Heat Transfer ◽  
Interfacial Structure ◽  
Sensible Heat ◽  
Two Phase ◽  
The Heat Transfer Coefficient

Future manned missions to Mars are expected to greatly increase the space vehicle’s size, weight, and heat dissipation requirements. An effective means to reducing both size and weight is to replace single-phase thermal management systems with two-phase counterparts that capitalize upon both latent and sensible heat of the coolant rather than sensible heat alone. This shift is expected to yield orders of magnitude enhancements in flow boiling and condensation heat transfer coefficients. A major challenge to this shift is a lack of reliable tools for accurate prediction of two-phase pressure drop and heat transfer coefficient in reduced gravity. Developing such tools will require a sophisticated experimental facility to enable investigators to perform both flow boiling and condensation experiments in microgravity in pursuit of reliable databases. This study will discuss the development of the Flow Boiling and Condensation Experiment (FBCE) for the International Space Station (ISS), which was initiated in 2012 in collaboration between Purdue University and NASA Glenn Research Center. This facility was recently tested in parabolic flight to acquire condensation data for FC-72 in microgravity, aided by high-speed video analysis of interfacial structure of the condensation film. The condensation is achieved by rejecting heat to a counter flow of water, and experiments were performed at different mass velocities of FC-72 and water and different FC-72 inlet qualities. It is shown that the film flow varies from smooth-laminar to wavy-laminar and ultimately turbulent with increasing FC-72 mass velocity. The heat transfer coefficient is highest near the inlet of the condensation tube, where the film is thinnest, and decreases monotonically along the tube, except for high FC-72 mass velocities, where the heat transfer coefficient is enhanced downstream. This enhancement is attributed to both turbulence and increased interfacial waviness. One-ge correlations are shown to predict the average condensation heat transfer coefficient with varying degrees of success, and a recent correlation is identified for its superior predictive capability, evidenced by a mean absolute error of 21.7%.

Flow Boiling Heat Transfer Coefficient of DI-Water/SiO2 Nanofluid Inside a 1.1 mm Round Microchannel

2015 ◽  
Author(s):  
Tiago A. Moreira ◽  
Francisco J. do Nascimento ◽  
Gherhardt Ribatski
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Single Phase ◽  
Flow Boiling ◽  
Volumetric Concentration ◽  
Nanoparticle Layer ◽  
Flow Boiling Heat Transfer ◽  
Before And After ◽  
The Heat Transfer Coefficient

The scope of the present paper is the evaluation of the heat transfer coefficient during flow boiling of DI-water/silica nanofluid inside a 1.1 mm ID tube. The experiments were performed for nanoparticles and DI-water with both having thermal conductivities of the same order of magnitude (kDI-water = 0.6 W/mK, ksilica = 1.4 W/mK). So, it was possible investigating the effect of the nanoparticles on the heat transfer coefficient under condition of negligible thermal conductivity enhancement. Experiments were carried out for mass velocities of 200, 400 and 600 kg/m2s, heat fluxes from 60 kW/m2 to 350 kW/m2 and nanoparticles volumetric concentration of 0.001%, 0.01% and 0.1%. Moreover, flow boiling heat transfer data under similar experimental conditions were obtained for DI-water without nanoparticles before and after performing each nanofluid test. The experiments were performed at the same test section according to the following sequence: i) DI-water, ii) 0.001% vol. nanofluid, iii) DI-water, iv) 0.01% vol. nanofluid, v) DI-water, vi) 0.1% vol. nanofluid, and vii) DI-water. Such procedure was adopted in order to evaluate the influence of the deposition of nanoparticles at each concentration on the heat transfer coefficient. For single-phase flow the HTC decreases as the experiments were performed. The thermal resistance due to deposition of nanoparticles is relevant to the heat transfer coefficient for single-phase flow of nanofluids inside microchannels. The flow boiling HTC decreases with increasing the nanoparticle volumetric concentration from a concentration of 0.001%. Based on the flow boiling HTC behaviors for tests with pure DI-water before and after the nanofluid tests, the fact that the HTC decreases with increasing the nanoparticle volumetric concentration is not explained only by the deposition on the surface of a nanoparticle layer. Tests for pure DI-water before the tests of nanofluids (BBN condition) and after all the nanofluids tests (ABN 0.1% condition) presents similar heat transfer coefficients, despite the deposition of a nanoparticle layer on the surface.

Prediction of the Heat Transfer Coefficient in a Small Channel with the Superposition and Asymptotic Correlations

2018 ◽  
Vol 26 (01) ◽  
pp. 1850001
Author(s):  
Yushazaziah Mohd-Yunos ◽  
Normah Mohd-Ghazali ◽  
Maziah Mohamad ◽  
Agus Sunjarianto Pamitran ◽  
Jong-Taek Oh
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Experimental Work ◽  
Nucleate Boiling ◽  
Vapor Quality ◽  
Two Phase ◽  
Forced Convective Heat Transfer ◽  
Small Channel ◽  
The Heat Transfer Coefficient

Heat transfer coefficient as an important characteristic in heat exchanger design is determined by the correlation developed from previous experimental work or accumulation of published data. Although discrepancies still exist between the existing correlations and practical data, several researchers claimed theirs as a generalized heat transfer correlation. Through optimization method, this study predicts the heat transfer coefficient of two-phase flow of propane in a small channel at the saturation temperature of 10[Formula: see text]C using two categories of correlation — superposition and asymptotic. Both methods consist of the contribution of nucleate boiling and forced convective heat transfer, the mechanisms that contribute to the total two-phase heat transfer coefficient, which become as two objective functions to be maximized. The optimization of experimental parameters of heat flux, mass flux, channel diameter and vapor quality is done by using genetic algorithm within a range of 5–20[Formula: see text]kW/m2, 100–250[Formula: see text]kg/m2[Formula: see text]s, 1.5–3[Formula: see text]mm and 0.009–0.99, respectively. In the result, the selected correlations under optimized condition agreed on the dominant mechanism at low and high vapor qualities are caused by the nucleate boiling and forced convective heat transfer, respectively. The optimization work served as an alternative approach in identifying optimized parameters from different correlations to achieve high heat transfer coefficient by giving a fast prediction of parameter range, particularly for the investigation of any new refrigerant. In parallel with some experimental works, a quick prediction is possible to reduce time and cost. From the four selected generalized correlations, Bertsch et al. show the closer trend with the reference experimental work until vapor quality of 0.6.

Nucleate Boiling Performance of Refrigerants and Refrigerant-Oil Mixtures

1980 ◽  
Vol 102 (4) ◽  
pp. 701-705 ◽  
Author(s):  
S. Chongrungreong ◽  
H. J. Sauer
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Significant Influence ◽  
Correlation Equation ◽  
Nucleate Boiling ◽  
Experimental Results ◽  
General Correlation ◽  
Oil Mixtures ◽  
The Heat Transfer Coefficient

Current and previous studies by the authors and others have shown shown that the carryover of oil in refrigeration systems can have a significant influence on the boiling performance in the evaporator of refrigeration systems. This investigation was conducted primarily to develop a general correlation equation for predicting the heat transfer coefficient for refrigerants and refrigerant-oil mixtures under pool boiling conditions. Experimental results were obtained to establish the validity of the correlation equation.

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