Pool Boiling Research Articles

CFD Simulations and Experimental Verification on Nucleate Pool Boiling of Liquid Nitrogen

To explore the mechanism of nucleate pool boiling of cryogenic fluids, an experimental apparatus was built to conduct a visualization study and verify the CFD boiling model. Apart from the general measurements of the super-heat and heat flux, the influences of super-heat on bubble departure diameters were specially analyzed. Based on the observations, the whole nucleate boiling process from bubble formation to departure from the heated wall can be divided into three stages: low heat flux stage; transitional stage; fully developed nucleate boiling (FDNB) stage. CFD simulations with several existing correlations and the attained values from the experiments for the bubble diameter were finally conducted, and the results fitted well with the present experimental data.

Pool Boiling of Water–Al2O3 and Water–Cu Nanofluids Outside Porous Coated Tubes

This paper deals with pool boiling of water–Al2O3 and water–Cu nanofluids on porous coated, horizontal tubes. Commercially available stainless-steel tubes having 10 mm outside diameter and 0.6 mm wall thickness were used to fabricate a test heater. Aluminum porous coatings 0.15 mm thick with porosity of about 40% were produced by plasma spraying. A smooth tube served as a reference tube. The experiments were conducted under different absolute operating pressures of 200 kPa, 100 kPa, and 10 kPa. Nanoparticles were tested at concentrations of 0.01%, 0.1%, and 1% by weight. In all cases tested, enhancement heat transfer was always observed during boiling of water–Al2O3 and water–Cu nanofluids on smooth tubes compared to boiling of distilled water. Contrary to smooth tubes, addition of even a small amount of nanoparticles resulted in deterioration of heat transfer during pool boiling of water–Al2O3 and water–Cu nanofluids on porous coated tubes in comparison with boiling of distilled water.

Numerical Study of Marangoni Convection around a Single Vapor Bubble during Pool Boiling

Boiling is known to be a very efficient mode of heat transfer in earth gravity, however, in microgravity bubble behavior is different because the buoyancy effects are replaced by surface tension effects such as Marangoni convection. The modeling of nucleate boiling with the effect of Marangoni convection in 0 g is accomplished by using Phase Field Method. Numerical simulation is carried out of single nucleating vapor bubble on a heated wall with and without Marangoni convection. The results show that the flow field consists of a major vortex that recirculates colder fluid from the upper region, pulling it toward the hot surface to the point where the bubble meets the heated surface. This type of flow pattern has been observed in various experiments.

Effect of Electric Field Distribution Generated in a Microspace on Pool Boiling Heat Transfer

This study describes the effect of an electric field on nucleate boiling and critical heat flux (CHF) in pool boiling. A dielectric liquid of AE-3000 was used as the working fluid. A heating surface was polished to a surface roughness of 0.05 μm. A microsized electrode, in which slits were provided, was designed to generate a nonuniform electric field and produce electrohydrodynamic (EHD) effects with the application of high dc voltages. The obtained results confirmed CHF enhancement as the EHD effects increased CHF to 86.2 W/cm2 with a voltage of −3000 V, which was four times greater than pool boiling in the absence of the electrode. The usual traveling wave on the bubble interface, induced by the Kelvin–Helmholtz instability, was modified by adding the EHD effects. The traveling wave model exhibits the essential features of the phenomenon and shows good agreement with the experimental data.

Experimental Study of Heat Transfer Enhancement in Pool Boiling by Using 2-Ethyl 1-Hexanol an Additive

The addition of additives to the water is known to enhance boiling heat transfer. In the present investigation, boiling heat transfer coefficients are measured for Nichrome wire, immersed in saturated water with & without additive. An additive used is 2-Ethyl 1-Hexanol with varying concentrations in the range of 10-10000 ppm. Extensive experimentation of pool boiling is carried out above the critical heat flux. Boiling behavior i.e. bubble dynamics are observed at higher heat flux for nucleate boiling of water over wide ranges of concentration of additive in water. Results are encouraging and show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient considerably higher, and that there is an optimum additive (500-1000ppm) concentration for higher heat fluxes. An optimum level of enhancement is observed up to a certain amount of additive 500-1000ppm in the tested range. Thereafter significant enhancement is not observed. This enhancement may be due to change in thermo-physical properties i.e. mainly due to a reduction in surface tension of water in the presence of additive.

Experimental Study of Effect of Nucleation Site Size on Bubble Dynamics during Nucleate Pool Boiling Heat Transfer

In this paper, effect of nucleation site size on bubble dynamics during nucleate pool boiling heat transfer in saturated water is studied experimentally. Single bubble was generated using right angle tip of a hypodermic needle as a nucleation site. The hypodermic needles were used of inner diameters 0.413mm, 0.514mm, and 0.603 mm with a constant depth of 25mm. The bubble dynamics was studied using SONY Cyber-shot DSC-H100 camera operating at 30 frames per second at atmospheric pressure and at a wall superheat of 5K. The results show that, bubble diameter, bubble height and bubble volume increases with increase in diameter of nucleation site. The bubble growth period is found to be dependent on nucleation site size, and it decreases with increase in diameter of nucleation site. This happens because as volume of vapor bubble increases, buoyancy force starts dominates the capillary force and bubble detaches earlier. Effect of nucleation site size on bubble departure diameter and bubble release frequency is also discussed.

Observations of the Critical Heat Flux Process During Pool Boiling of FC-72

Experimental work was undertaken to investigate the process by which pool-boiling critical heat flux (CHF) occurs using an IR camera to measure the local temperature and heat transfer coefficients on a heated silicon surface. The wetted area fraction (WF), the contact line length density (CLD), the frequency between dryout events, the lifetime of the dry patches, the speed of the advancing and receding contact lines, the dry patch size distribution on the surface, and the heat transfer from the liquid-covered areas were measured throughout the boiling curve. Quantitative analysis of this data at high heat flux and transition through CHF revealed that the boiling curve can simply be obtained by weighting the heat flux from the liquid-covered areas by WF. CHF mechanisms proposed in the literature were evaluated against the observations.

Quench Pool Boiling with Temporary Crystalline Enhancers

AbstractIn some industrial activities, the use of permanent heat transfer enhancements such as metal coating, pins, and grooves in cryogenic treatment is quite problematic. Such permanent heat transfer enhancers were replaced with temporary enhancers made of different crystalline materials, here focusing on NaCl, MgSO4·7H2O, CaCl2·2H2O, and C6H5Na3O7·2H2O, which were used during quenching of the sample in the cryogenic liquid, i.e., nitrogen. The time required for sample cooling until the liquid nitrogen saturation temperature is reached decreases significantly when a crystalline coating is applied. The dependence of the cooling time on temporary coating creation parameters such as solution concentration, initial temperature of the sample, and solution spreading time is discussed.

Application of Neural Networks to Predict Changing the Diameters of Bubbles in Pool Boiling Distilled Water

Application of Neural Networks to Predict Changing the Diameters of Bubbles in Pool Boiling Distilled Water

1003 Subcooled Pool Boiling CHF on Horizontal Cylinders with Different Surfaces in a Pool of Water at Pressures due to Pre-pressurization and Exponentially Increasing Heat Inputs

1003 Subcooled Pool Boiling CHF on Horizontal Cylinders with Different Surfaces in a Pool of Water at Pressures due to Pre-pressurization and Exponentially Increasing Heat Inputs

Effect of Electric Field Generated by Microsized Electrode on Pool Boiling

This paper describes the results from an experimental study of the effect of an electrohydrodynamic (EHD) and an electrostatic force on the critical heat flux in pool boiling. The dielectric liquid of HFE-7100 (3M Ltd.), which has a boiling point of 59.8 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C, was selected as a working fluid. In order to generate high electric fields with the application of low voltages, a micropatterned electrode with an array of planar comb fingers was made by microelectromechanical systems technology. The electrode had ten slits whose width was 400 μm between electrode pairs so as to remove vapor bubbles from a heat transfer surface by the EHD effect. A cooling device fabricated with the electrode was evaluated by different applied voltages. As a result, the application of voltage enhanced heat transfer.

Fundamental Issues of Critical Heat Flux Phenomena During Flow Boiling in Microscale-Channels and Nucleate Pool Boiling in Confined Spaces

This article presents a comprehensive literature review on the fundamental issues of critical heat flux (CHF) during flow boiling and nucleate pool boiling in microscale channels and confined spaces. First, distinction between macro- and micro-scale channels is discussed. Then the CHF mechanisms are discussed. Next, experimental and theoretical studies of subcooled flow boiling CHF in microscale channels together with the prediction methods are reviewed and analyzed. Following this, experimental and theoretical studies on saturated flow boiling CHF together with the prediction methods are summarized and discussed. Furthermore, experimental and theoretical studies on nucleate pool boiling CHF in confined spaces together with the relevant prediction methods are reviewed as well. So far, limited studies on CHF microscale channels and confined spaces are available in the literature. There are numerous discrepancies in the existing studies on CHF results, mechanisms, and prediction methods. Furthermore, there are no generalized prediction methods for CHF in microscale channels and confined spaces. According to this review, future research needs for the experiments, mechanisms, and prediction methods of CHF phenomena in microscale channels and confined spaces have been addressed.

Pool Boiling of Nanofluids in Vertical Porous Media

The development of electronic components such as microprocessor requires a better thermal management system to overcome the high heat flux produce by the component. The method to absorb the heat produce by the microprocessor is still use the conduction or either natural or free convection which still in a single phase heat transfer. One of heat transfer method that suitable for a high heat flux application is pool boiling which has a two order of magnitude higher than of a single phase heat transfer and does not require a pump to move the fluid. In this study has been conducted the pool boiling experiment with four different porous media surface which are sintered copper 300 µm and 400 µm, copper screen mesh and stainless steel screen mesh with four different fluid which are Al2O3-Water 1%, 3% and 5%. The sintered copper 400 µm has shown a better heat transfer performance compared to the other porous media. The Water, Al2O3-Water 5% has shown a performance no better than Al2O3-Water 1% and 3%.

Impact of Thermal Shock on Fouling of Various Structured Tubes During Pool Boiling of CaSO4 Solutions

Crystallization fouling during nucleate pool boiling is characterized with relatively rapid formation of a hard and brittle deposit layer. In this study, the impact of thermal shock is experimentally investigated on cleaning of various tubes when subjected to fouling of CaSO4 solutions. The heat transfer tubes included stainless-steel plain and finned tubes with fin densities of 19 and 40 fins per inch. The tubes were used during pool boiling for heat fluxes ranging from 80 to 300 kW/m2. The thermal shock is applied by the sudden decrease or increase in heat flux for approximately 30 s after the fouling layer is formed. In terms of cleaning, the experimental results showed far better performance for the plain tube. During the sudden change in heat flux the whole fouling layer cracked and peeled off, receiving again almost initial clean heat transfer performance. Contrariwise, the results for the finned tubes showed that the fouling layer was only affected marginally by the thermal shock.

Migration Properties of TiO2 Nanoparticles during the Pool Boiling of Nanorefrigerants

Nanofluid is a promising fluid due to its enhanced heat transfer properties. Nanorefrigerant is a kind of nanofluid that uses a refrigerant as the base fluid. It can enhance the energy and cooling performance of refrigeration and air-conditioning systems. The objective of this paper is to study the migration properties of nanoparticles during the pool boiling of the nanorefrigerant. The effects of different parameters including heat flux, liquid level height, vessel size, insulation, and lubricating oil on the migration of nanosized particles have been investigated. TiO2 particles with average diameters of 40 nm were used with R141b refrigerant. The experimental results show that the migrated mass of nanoparticles increases with augmenting the initial mass of nanoparticles as well as the applied heat flux. Besides, particle departure from the liquid to vapor augments by increasing the lubricating oil concentration and adding insulation to the container. However, the migration of nanoparticles decreases wi...

Numerical Investigation in the Factors on the Pool Boiling

A numerical investigation is conducted to understand the factors of influence on a pool boiling in a micro system. The nucleation activities within microlayer were captured clearly to provide details of phase change process. Boiling curve of water under ambient pressure at 1atm is obtained, numerically, which makes good agreements with several experimental results. The effects of ambient pressure, contact angle and surface roughness on heat transfer were also studied, systematically

Effects of Acidity and Method of Preparation on Nucleate Pool Boiling of Nanofluids

Past research has shown contradicting trends in the rate of heat transfer during pool boiling of nanofluids, which could be attributed either to their stability or to their method of preparation or to both. An experimental study has been conducted to investigate the effects of electrostatic stabilization and preparation method of nanofluids on their pool boiling rate of heat transfer. Nanofluids made from water and alumina nanoparticles at 0.1 vol% concentration were used. The effect of electrostatic stabilization was investigated by changing the pH value from 6.5, neutral, to 5, acidic. The effect of preparation method has been investigated by using nanofluids prepared from dry particles and from ready-made suspensions. Compared with water, all nanofluids investigated resulted in deterioration in the rate of heat transfer during pool boiling. Neutral nanofluids made from ready-made suspensions and from dry particles resulted into almost the same deterioration in the rate of heat transfer of 49% and 45%, respectively, with respect to that of pure water. The most significant effect of electrostatic stabilization was found in the case of acidic nanofluids made from dry particles, which resulted in deterioration in the rate of heat transfer of 31%. However, acidic nanofluids made from ready-made suspensions resulted in a deterioration of 46%, which is almost the same as that of suspension-made and dry particles-made nanofluids. These results indicate that electrostatic stabilization using acid addition is most effective with nanofluids made from dry particles.

Comparison of Deionized Water and FC-72 in Pool and Jet Impingement Boiling Thermal Management

High heat fluxes and stringent constraints on surface temperature and its uniformity during thermal management of electrical and electronic components often necessitate use of boiling heat transfer. This paper compares the pool and jet impingement boiling heat transfer characteristics of deionized water and FC-72 at an equivalent fluid saturation temperature of 57°C and for identical experimental conditions. To lower the saturation temperature of water down to 57°C, experiments with water are performed at a reduced absolute system pressure of 0.176 bar. Despite the reduction in pressure, pool boiling critical heat flux with deionized water is found to be 3.6 times larger than with FC-72. Furthermore, jet impingement is seen to enhance boiling heat transport more significantly for water than for FC-72. Consequently, heat transfer coefficients during jet impingement boiling are as much as 3.9 times larger for water compared to FC-72 at identical Reynolds numbers and surface temperatures. The heat transfer advantage of using water is mainly associated with the superior thermophysical properties of this fluid. However, in addition to the large fluid saturation temperature at atmospheric conditions, direct cooling of electronics is frequently not possible using water due to the incompatibility of the fluid with electrical components. To assess the practical utility of subatmospheric deionized water through indirect cooling of electronics, a 1-D heat sink analysis is performed on a multichip module geometry. The overall thermal resistance of the heat sink using water is determined to be around two times lower than that of direct cooling of FC-72 on a silicon substrate. Under saturation condition of the working fluids, dissipation of heat fluxes in excess of ~45 W/cm2 with the multichip module using water is constrained by the chip surface temperature limit.

Introducing Nanotechnology into the Thermal and Fluids Curricula: Pool Boiling Heat Transfer in Nanofluids

Nanotechnology has generated a large amount of interest in recent years, especially among engineering educators. Our institution continues to be among the leading universities to offer undergraduate courses that involve students in experiential learning of nanoscience topics. This paper describes a new thermo-fluids laboratory module where engineering students undertake problem-based experiments with nanofluids. The equipment, process and student work and feedback for the laboratory module are presented.

Erratum: “Water-Heated Pool Boiling of Different Refrigerants on the Outside Surface of a Horizontal Smooth Tube” [ASME Journal of Heat Transfer, 2012, 134, 021502

Erratum: “Water-Heated Pool Boiling of Different Refrigerants on the Outside Surface of a Horizontal Smooth Tube” [ASME Journal of Heat Transfer, 2012, 134, 021502