scholarly journals Effect of spray cooling on heat transfer in a two-phase helium flow

Cryogenics ◽  
2013 ◽  
Vol 57 ◽  
pp. 74-87 ◽  
Author(s):  
S. Perraud ◽  
L. Puech ◽  
P. Thibault ◽  
B. Rousset ◽  
P.E. Wolf
Keyword(s):  
Heat Transfer ◽  
Spray Cooling ◽  
Helium Flow ◽  
Two Phase

scholarly journals Experimental Investigation on Heat Transfer Mechanism of Air-Blast-Spray-Cooling System with a Two-Phase Ejector Loop for Aeronautical Application

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3963 ◽  
Author(s):  
Jia-Xin Li ◽  
Yun-Ze Li ◽  
Ben-Yuan Cai ◽  
En-Hui Li
Keyword(s):  
Heat Transfer ◽  
Droplet Size ◽  
Cooling System ◽  
Volumetric Flow Rate ◽  
Least Square Method ◽  
Spray Cooling ◽  
Cooling Capacity ◽  
Least Square ◽  
Two Phase ◽  
Air Blast

This paper presents an air-oriented spray cooling system (SCS) integrated with a two-phase ejector for the thermal management system. Considering its aeronautical application, the spray nozzle in the SCS is an air-blast one. Heat transfer performance (HTP) of air-water spray cooling was studied experimentally on the basis of the ground-based test. Factors including pressure difference between water-inlet-pressure (WIP) and spray cavity one (PDWIC) and the spray volumetric flow rate (SVFR) were investigated and discussed. Under a constant operating condition, the cooling capacity can be promoted by the growth factors of the PDWIC and SVFR with the values from 51.90 kPa to 235.35 kPa and 3.91 L ⋅ h − 1 to 14.53 L ⋅ h − 1 , respectively. Under the same heating power, HTP is proportional to the two dimensionless parameters Reynolds number and Weber number due to the growth of droplet-impacting velocity and droplet size as the increasing of PDWIC or SVFR. Additionally, compared with the factor of the droplet size, the HTP is more sensitive to the variation in the droplet-impacting velocity. Based on the experimental data, an empirical experimental correlation for the prediction of the dimensionless parameter Nusselt number in the non-boiling region with the relative error of only ± 10 % was obtained based on the least square method.

Spray Cooling Heat Transfer Enhancement and Degradation Using Fractal-Like Micro-Structured Surfaces

2011 ◽  
Author(s):  
Alex Tulchinsky ◽  
Deborah V. Pence ◽  
James A. Liburdy
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Smooth Surface ◽  
Single Phase ◽  
High Volume ◽  
Spray Cooling ◽  
Volume Flux ◽  
Two Phase ◽  
Structured Surfaces

In the present study, spray cooling curves are presented for two micro-structured surfaces and are compared to smooth surface results. The micro-structured surfaces consisted of bio-inspired fractal-like geometries, denoted as grooves or fins, extending in a radial direction from the center to the periphery of a 37.8 mm circular disc. Depending on the location on the surface, dimensions of groove widths and heights varied from 100 to 500 μm, and 30 to 60 μm, respectively. Fin width and height dimensions remained constant over the surface at 127 and 60 μm, respectively. Results are presented as heat flux versus the surface-to-exit spray temperature difference at each of five volume flux conditions ranging from 0.54 to 2.04 × 10−3 m3/m2-s. Convection heat transfer coefficients are also presented for each case as a function of heat flux. Results indicate that at low and high volume fluxes, an improvement in heat transfer occurs in the single phase regime for the fin geometry. Enhancement in the single phase regime does not occur at the intermediate volume flux condition. In the two phase regime for the fin structure significant enhancements, up to 50%, are observed. Whereas the groove structure performs similarly to the smooth surface in the single phase regime and exhibits large degradation in the two phase and critical heat flux regimes, up to 50%. Critical heat flux for the fin surface compares well to that of the flat surface, with a slightly increase at high volume flux conditions.

Molecular-to-Large-Scale Heat Transfer With Multiphase Interfaces: Current Status and New Directions

2009 ◽  
Vol 131 (12) ◽  
Author(s):  
Raj M. Manglik ◽  
Milind A. Jog
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Film Coating ◽  
Spray Cooling ◽  
Current Status ◽  
Experimental Investigations ◽  
Interfacial Behavior ◽  
Two Phase ◽  
New Directions ◽  
Momentum And Heat Transfer

The scientific understanding of multiphase interfaces and the associated convective mass, momentum, and heat transport across and along their boundaries, provide the fundamental underpinnings of the advancement of boiling heat transfer, two-phase flows, heat pipes, spray cooling, and droplet-film coating, among many other engineering applications. Numerous studies have tried to characterize the interfacial behavior and model their mechanistic influences either directly or implicitly via parametric experimental investigations and/or simulations. The goal of advancing our understanding as well as developing generalized, perhaps “universal,” and more accurate phenomenological or mechanistic correlations, for predicting mass, momentum, and heat transfer, continues to engage the worldwide research community. A collection of some such current investigations that are representative of both basic and applied issues in the field is presented in this special issue of the Journal of Heat Transfer.

Spray Cooling of High Aspect Ratio Open Microchannels

2007 ◽  
Vol 129 (8) ◽  
pp. 1052-1059 ◽  
Author(s):  
Johnathan S. Coursey ◽  
Jungho Kim ◽  
Kenneth T. Kiger
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Thermal Performance ◽  
High Aspect Ratio ◽  
Flat Surface ◽  
Spray Cooling ◽  
Heat Sinks ◽  
Projected Area ◽  
Two Phase ◽  
Flux Flow

Direct spraying of dielectric liquids has been shown to be an effective method of cooling high-power electronics. Recent studies have illustrated that even higher heat transfer can be obtained by adding extended structures, particularly straight fins, to the heated surface. In the current work, spray cooling of high-aspect-ratio open microchannels was explored, which substantially increases the total surface area and allows more residence time for the incoming liquid to be heated by the wall. Five such heat sinks were constructed, and their thermal performance was investigated. These heat sinks featured a projected area of 1.41×1.41cm2, channel width of 360μm, a fin width of 500μm, and fin lengths of 0.25mm, 0.50mm, 1.0mm, 3.0mm, and 5.0mm. The five enhanced surfaces and a flat surface with the same projected area were sprayed with a full cone nozzle using PF-5060 at 30°C and nozzle pressure differences from 1.36–4.08atm(69–121ml∕min). In all cases, the enhanced surfaces improved thermal performance compared to the flat surface. Longer fins were found to outperform shorter ones in the single-phase regime. Adding fins also resulted in the onset of two-phase effects (and higher-heat transfer) at lower wall temperatures than the flat surface. The two-phase regime was characterized by a balance between added area, changing flow flux, flow channeling, and added conduction resistance. Spray efficiency calculations indicated that a much larger percentage of the liquid sprayed onto the enhanced surface evaporated than with the flat surface. Fin lengths between 1mm and 3mm appeared to be optimum for heat fluxes as high as 124W∕cm2 (based on projected area) and the range of conditions studied.

Two-Phase Spray Cooling With Water/2-Propanol Binary Mixture: Investigation of Mass Diffusion Resistance

2016 ◽  
Author(s):  
Sai Sujith Obuladinne ◽  
Huseyin Bostanci
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Performance ◽  
Pure Water ◽  
Spray Cooling ◽  
High Heat ◽  
Working Fluid ◽  
High Heat Flux ◽  
Two Phase ◽  
High Heat Transfer

Two-phase spray cooling has been an emerging thermal management technique offering high heat transfer coefficients (HTCs) and critical heat flux (CHF) levels, near-uniform surface temperatures, and efficient coolant usage that enables to design of compact and lightweight systems. Due to these capabilities, spray cooling is a promising approach for high heat flux applications in computing, power electronics, and optics. The two-phase spray cooling inherently depends on saturation temperature-pressure relationships of the working fluid to take advantage of high heat transfer rates associated with liquid-vapor phase change. When a certain application requires strict temperature and/or pressure conditions, thermophysical properties of the working fluid play a critical role in attaining proper efficiency, reliability, or packaging structure. However, some of the commonly used working fluids today, including refrigerants and dielectric liquids, have relatively poor properties and heat transfer performance. In such cases, utilizing binary mixtures to tune working fluid properties becomes an alternative approach. This study aimed to conduct an initial investigation on the spray cooling characteristics of practically important binary mixtures and demonstrate their capability for challenging high heat flux applications. The working fluid, water/2-propanol binary mixture at various concentration levels, specifically at x1 (liquid mass fraction of 2-proponal in water) of 0.0 (pure water), 0.25, 0.50, 0.879 (azeotropic mixture) and 1.0, represented both non-azeotropic and azeotropic cases. Tests were performed on a closed loop spray cooling system using a pressure atomized spray nozzle with a constant liquid flow rate at corresponding 20°C subcooling conditions and 1 Atm pressure. A copper test section measuring 10 mm × 10 mm × 2 mm with a plain, smooth surface simulated high heat flux source. Experimental procedure involved controlling the heat flux in increasing steps, and recording the steady-state temperatures to obtain cooling curves in the form of surface superheat vs heat flux. The obtained results showed that pure water (x1 = 0.0) and 2-propanol (x1 = 1.0) provide the highest and lowest heat transfer performance, respectively. At a given heat flux level, the HTC values indicated strong dependence on x1, where the HTCs depress proportional to the concentration difference between the liquid and vapor phases. The CHF values sharply decreased at x1≥ 0.25.

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.

A Low Profile Thermal Management Device for High Power Processors Using Enhanced Flow Boiling Techniques and Perfluorocarbon Fluids

2005 ◽  
Author(s):  
John D. Schwarzkopf ◽  
Charles L. Tilton ◽  
Clayton T. Crowe ◽  
Ben Q. Li
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Flow Boiling ◽  
Numerical Models ◽  
Spray Cooling ◽  
Two Phase ◽  
Low Profile ◽  
Present Solution ◽  
Mini Channels ◽  
The Heat Transfer Coefficient

It is advantageous to the electronic industry to remove in excess of 150W from a processor die with a case-to-ambient thermal resistance < 0.2 ° C/W. Although this is achievable with air cooled thermal solutions, the form factor is unwieldy and as the ambient temperature rises, the processor throttles the performance. Alternatively, thermal solutions containing water are trivial to implement but potential leaks can pose a threat to the electronic suite. The present solution is non-trivial; it utilizes a dielectric perfluorocarbon fluid (PF5050) and a combination of spray cooling and mini-channel flow boiling techniques with a particular focus on superficial quality at the onset of the channels. The idea behind mixing the two techniques is to augment the heat transfer coefficient by driving the fluid into an annular state upon entry of the mini-channels while retaining a low profile package. A macro-channel boiling heat transfer correlation was used and results show that it predicts the average surface temperature to within 10% of the experimental data. Quasi-one-dimensional numerical models were developed to predict vapor entrainment and two-phase pressure drop. Experimental results show that in excess of 250W can be removed from a 1.24cm × 1.24cm die without removing the integrated heat sink (IHS), with a case-to-ambient thermal resistance of <0.2° C/W at 150W. The packaged size is 5.6cm long by 3.1cm wide by 1.6cm tall, thus allowing the end user to adapt the technology into blade style or 1U style servers with low risk.

Device for measuring pressure drop and heat transfer in two-phase helium flow

Cryogenics ◽  
1969 ◽  
Vol 9 (1) ◽  
pp. 36-38 ◽  
Author(s):  
V.E. Keilin ◽  
E.Yu. Klimenko ◽  
I.A. Kovalev
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Helium Flow ◽  
Two Phase

THE MECHANISM OF RAISING AND QUANTIFICATION OF SPECIFIC HEAT FLUX AT BOILING OF NANOFLUIDS IN FREE CONVECTION CONDITIONS

2017 ◽  
pp. 25-34
Author(s):  
V.N. Moraru
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Capacity ◽  
Specific Heat ◽  
Chemical Properties ◽  
Heating Surface ◽  
Physical Models ◽  
Superheated Liquid ◽  
Two Phase ◽  
Boiling Process

The results of our work and a number of foreign studies indicate that the sharp increase in the heat transfer parameters (specific heat flux q and heat transfer coefficient _) at the boiling of nanofluids as compared to the base liquid (water) is due not only and not so much to the increase of the thermal conductivity of the nanofluids, but an intensification of the boiling process caused by a change in the state of the heating surface, its topological and chemical properties (porosity, roughness, wettability). The latter leads to a change in the internal characteristics of the boiling process and the average temperature of the superheated liquid layer. This circumstance makes it possible, on the basis of physical models of the liquids boiling and taking into account the parameters of the surface state (temperature, pressure) and properties of the coolant (the density and heat capacity of the liquid, the specific heat of vaporization and the heat capacity of the vapor), and also the internal characteristics of the boiling of liquids, to calculate the value of specific heat flux q. In this paper, the difference in the mechanisms of heat transfer during the boiling of single-phase (water) and two-phase nanofluids has been studied and a quantitative estimate of the q values for the boiling of the nanofluid is carried out based on the internal characteristics of the boiling process. The satisfactory agreement of the calculated values with the experimental data is a confirmation that the key factor in the growth of the heat transfer intensity at the boiling of nanofluids is indeed a change in the nature and microrelief of the heating surface. Bibl. 20, Fig. 9, Tab. 2.

Sign in / Sign up

Export Citation Format

Share Document