The talk with present the key results of the IPCC Working Group III 5th assessment report. Concluding four years of intense scientific collaboration by hundreds of authors from around the world, the report responds to the request of the world's governments for a comprehensive, objective and policy neutral assessment of the current scientific knowledge on mitigating climate change. The report has been extensively reviewed by experts and governments to ensure quality and comprehensiveness.

Climate change 2014 - Mitigation of climate change

This chapter discusses leading problems linked to energy that the world is now confronting and to propose some ideas concerning possible solutions. Oil deserves special attention among all energy sources. Since the beginning of 1981, it has merely been continuing and enhancing the downward movement in consumption and prices caused by excessive rises, especially for light crudes such as those from Africa, and the slowing down of worldwide economic growth. Densely-populated oil-producing countries need to produce to live, to pay for their food and their equipment. If the economic growth of the industrialized countries were to be 4%, even if investment in the rational use of energy were pushed to the limit and the development of nonpetroleum energy sources were also pursued actively, it would be extremely difficult to prevent a sharp rise in prices. It is evident that it is absolutely necessary to pursue actively the development of coal, natural gas, and nuclear power if a physical shortage of energy is not to block economic growth.

World energy outlook

An introduction to heat transfer

Boundary-layer flow of a nanofluid past a stretching sheet

Nanofluids, the fluid suspensions of nanomaterials, have shown many interesting properties, and the distinctive features offer unprecedented potential for many applications. This paper summarizes the recent progress on the study of nanofluids, such as the preparation methods, the evaluation methods for the stability of nanofluids, and the ways to enhance the stability for nanofluids, the stability mechanisms of nanofluids, and presents the broad range of current and future applications in various fields including energy and mechanical and biomedical fields. At last, the paper identifies the opportunities for future research.

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A review on nanofluids: preparation, stability mechanisms, and applications

The effects of hydrophilic/hydrophobic surface patterning on critical heat flux (CHF) and heat transfer coefficient (HTC) were studied using custom-engineered testing surfaces. Patterning was created over a sapphire substrate and tested in a pool boiling facility in MITs Reactor Hydraulics Laboratory. The hydrophilic and hydrophobic matrices were created using layer by layer deposition of 50 nm thick SiO2 nanoparticles and monolayer thickness fluorosilane, respectively. Ultraviolet ozone patterning was then used with chrome-printed masks to create the desired geometric features. Hexagon, ring, star, and mixed patterns were tested to determine their abilities to affect CHF and HTC through prevention of bubble pinning at high heat fluxes. During testing, an infrared camera was used to measure the surface temperature distribution as well as locate nucleation sites for data analysis. It was found that CHF values were enhanced over the bare sapphire values by approximately 90% for hexagons, 60% for stars, 65% for rings, and 50% for mixed patterns. Contrary to expectations, patterning did not seem to affect the HTC values significantly. Although patterning did improve CHF performance over bare heaters, both CHF and HTC were found to be statistically similar to those for unpatterned, uniformly hydrophilic surfaces.Copyright © 2013 by ASME

Effects of Hydrophobic Surface Patterning on Boiling Heat Transfer and Critical Heat Flux of Water at Atmospheric Pressure

The nanofluid literature contains many claims of anomalous convective heat transfer enhancement in both turbulent and laminar flow. To put such claims to the test, we have performed a critical detailed analysis of the database reported in 12 nanofluid papers (8 on laminar flow and 4 on turbulent flow). The methodology accounted for both modeling and experimental uncertainties in the following way. The heat transfer coefficient for any given data set was calculated according to the established correlations (Dittus-Boelter’s for turbulent flow and Shah’s for laminar flow). The uncertainty in the correlation input parameters (i.e. nanofluid thermo-physical properties and flow rate) was propagated to get the uncertainty on the predicted heat transfer coefficient. The predicted and measured heat transfer coefficient values were then compared to each other. If they differed by more than their respective uncertainties, we judged the deviation anomalous. According to this methodology, it was found that in nanofluid laminar flow in fact there seems to be anomalous heat transfer enhancement in the entrance region, while the data are in agreement (within uncertainties) with the Shah’s correlation in the fully developed region. On the other hand, the turbulent flow data could be reconciled (within uncertainties) with the Dittus-Boelter’s correlation, once the temperature dependence of viscosity was included in the prediction of the Reynolds number. While this finding is plausible, it could not be conclusively confirmed, because most papers do not report information about the temperature dependence of the viscosity for their nanofluids.Copyright © 2011 by ASME

Convective Heat Transfer Enhancement in Nanofluids: Real Anomaly or Analysis Artifact?

This paper presents an investigation of transient heat transfer, which may occur in nuclear reactors with plate-type fuel during a reactivity initiated accident. Analytical solutions of the heat transfer equation were developed to describe the behavior of plate-type fuel and the MIT pool boiling facility during exponential power excursions governed by conduction heat transfer. Experimental results for non-boiling transient heat transfer tests are also presented and compared to the analytical solutions. Infrared thermometry was used to measure the temperature on the heater surface. The test matrix included exponential power escalations with periods τ as short as 5 milliseconds and water subcoolings ranging from 0 to 78 K. Heat transfer curves and effective heat transfer coefficients to water were measured. The experimental data confirm that the effective heat transfer coefficient decreases monotonically as 1/√τ, as expected from the analytical solutions.

Experimental and Analytical Study of Exponential Power Excursion in Plate-Type Fuel

A new Offshore Floating Nuclear Plant (OFNP) concept with high potential for attractive economics and an unprecedented level of safety is presented, along with an overview of work done in the area of security. The OFNP creatively combines state-of-the-art Light Water Reactors (LWRs) with floating platforms such as those used in offshore oil/gas operations, both of which are well-established technologies which can allow implementation on a time scale consistent with combating climate change in the near future. OFNP is a plant that can be entirely built within a floating platform in a shipyard, transferred to the site. OFNP eliminates earthquakes and tsunamis as accident precursors; its ocean-based passive safety systems eliminate the loss of ultimate heat sink accident by design. The defense of an OFNP poses new security opportunities and challenges compared to land-based plants. Such a plant can be more easily defended by virtue of the clear 360 degree lines of sight and the relative ease of identifying surface threats. Conversely the offshore plant is potentially vulnerable to underwater approaches by mini-submarines and divers. We investigate security considerations of the OFNP applicable to two potential plant options, an OFNP-300 with a 300 MWe reactor, and an OFNP-1100 with an 1100 MWe reactor. Three innovative security system approaches could be combined for the offshore plant. The first is a comprehensive detection system which integrates radar, sonar and unmanned vehicles for a long distance overview of the vicinity ∗Address all correspondence to this author. of the plant. The second approach is the use of passive physical barriers about 100 meters from the plant, which will force a fastmoving power boat to lose speed or stop at the barrier allowing the plant security force more time to respond. The third approach takes advantage of the offshore plant siting and the monthly or biweekly rotation of crew to reduce the total on-plant and onshore security force by using the off-duty security force on the plant as a reserve force. Through the use of these approaches, the OFNP-300 should be able to achieve a similar security cost (on a per Megawatt basis) as land-based plants of similar or somewhat larger power rating. Due to non-linear scaling of cost, the security cost of the OFNP-1100 has the potential to be reduced significantly compared to its land-based equivalents.

Overview of Security Plan for Offshore Floating Nuclear Plant

Nanofluids are engineered colloidal dispersions of nano-sized particle in common base fluids. Previous pool boiling studies have shown that nanofluids can improve critical heat flux (CHF) up to 200% for pool boiling and up to 50% for subcooled flow boiling due to the boiling induced nanoparticle deposition on the heated surface. Motivated by the significant CHF enhancement of nanoparticle deposited surface, this study investigated experimentally the subcooled flow boiling heat transfer of pre-coated test sections in water. Using a separate coating loop, stainless steel test sections were treated via flow boiling of alumina nanofluids at constant heat flux and mass flow rate. The pre-coated test sections were then used in another loop to measure subcooled flow boiling heat transfer coefficient and CHF with water. The CHF values for the pre-coated tubing were found on average to be 28% higher than bare tubing at high mass flux G = 2500 kg/m2 s. However, no enhancement was found at lower mass flux G = 1500 kg/m2 s. The heat transfer coefficients did not differ much between experiments when the bare or coated tubes were used. SEM images of the test sections confirm the presence of a nanoparticle coating layer. The nanoparticle deposition is sporadic and no relationship between the coating pattern and the amount of CHF enhancement is observed.Copyright © 2009 by ASME

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Jacopo Buongiorno

Papers

Effects of Hydrophobic Surface Patterning on Boiling Heat Transfer and Critical Heat Flux of Water at Atmospheric Pressure

Convective Heat Transfer Enhancement in Nanofluids: Real Anomaly or Analysis Artifact?

Experimental and Analytical Study of Exponential Power Excursion in Plate-Type Fuel

Overview of Security Plan for Offshore Floating Nuclear Plant

Alumina Nanoparticle Pre-Coated Tubing Enhancing Subcooled Flow Boiling Critical Heat Flux