01 Jan 1976-
About: The article was published on 1976-01-01 and is currently open access. It has received 9629 citations till now. The article focuses on the topics: Heat transfer.
TL;DR: In this article, the ability to achieve a simultaneous increase in the power factor and a decrease in the thermal conductivity of the same nanocomposite sample and for transport in the same direction is discussed.
Abstract: Many of the recent advances in enhancing the thermoelectric figure of merit are linked to nanoscale phenomena found both in bulk samples containing nanoscale constituents and in nanoscale samples themselves. Prior theoretical and experimental proof-of-principle studies on quantum-well superlattice and quantum-wire samples have now evolved into studies on bulk samples containing nanostructured constituents prepared by chemical or physical approaches. In this Review, nanostructural composites are shown to exhibit nanostructures and properties that show promise for thermoelectric applications, thus bringing together low-dimensional and bulk materials for thermoelectric applications. Particular emphasis is given in this Review to the ability to achieve 1) a simultaneous increase in the power factor and a decrease in the thermal conductivity in the same nanocomposite sample and for transport in the same direction and 2) lower values of the thermal conductivity in these nanocomposites as compared to alloy samples of the same chemical composition. The outlook for future research directions for nanocomposite thermoelectric materials is also discussed.
TL;DR: This work discusses sources of uncertainty and proposes a simple analytical model for the SWNT thermal conductivity including length and temperature dependence, which is attributed to second-order three-phonon scattering between two acoustic modes and one optical mode.
Abstract: The thermal properties of a suspended metallic single-wall carbon nanotube (SWNT) are extracted from its high-bias (I−V) electrical characteristics over the 300−800 K temperature range, achieved by Joule self-heating. The thermal conductance is approximately 2.4 nW/K, and the thermal conductivity is nearly 3500 Wm-1K-1 at room temperature for a SWNT of length 2.6 μm and diameter 1.7 nm. A subtle decrease in thermal conductivity steeper than 1/T is observed at the upper end of the temperature range, which is attributed to second-order three-phonon scattering between two acoustic modes and one optical mode. We discuss sources of uncertainty and propose a simple analytical model for the SWNT thermal conductivity including length and temperature dependence.
TL;DR: Entropy generation minimization (finite time thermodynamics, or thermodynamic optimization) is the method that combines into simple models the most basic concepts of heat transfer, fluid mechanics, and thermodynamics as mentioned in this paper.
Abstract: Entropy generation minimization (finite time thermodynamics, or thermodynamic optimization) is the method that combines into simple models the most basic concepts of heat transfer, fluid mechanics, and thermodynamics. These simple models are used in the optimization of real (irreversible) devices and processes, subject to finite‐size and finite‐time constraints. The review traces the development and adoption of the method in several sectors of mainstream thermal engineering and science: cryogenics, heat transfer, education, storage systems, solar power plants, nuclear and fossil power plants, and refrigerators. Emphasis is placed on the fundamental and technological importance of the optimization method and its results, the pedagogical merits of the method, and the chronological development of the field.
TL;DR: In this paper, a dimensionless correlation for predicting heat transfer coefficients during film condensation inside pipes is presented, which has been verified by comparison with a wide variety of experimental data.
Abstract: A simple dimensionless correlation for predicting heat-transfer coefficients during film condensation inside pipes is presented. It has been verified by comparison with a wide variety of experimental data. These include fluids water, R-11, R-12, R-22, R-113, methanol, ethanol, benzene, toluene, and trichloroethylene condensing in horizontal, vertical, and inclined pipes of diameters ranging from 7 to 40mm. One data set for condensation inside an annulus has also been analyzed. The range of parameters covered includes reduced pressures from 0.002 to 0.44, saturation temperatures from 21 to 310°C, vapor velocities from 3 to 300m/s, vapor qualities from 0 to 100%, mass flux 39000-758 000kg/m2 h, heat flux from 158 to 1 893000W/m2, all liquid Reynolds numbers from 100 to 63 000, and liquid Prandtl numbers from 1 to 13. The mean deviation for the 474 data points analyzed was found to be 15.4%.
TL;DR: Temperature in =10-microliter aqueous suspensions of 20-nanometer gold particles irradiated by a continuous wave Ar+ ion laser at 514 nm increased to a maximum equilibrium value in proportion to incident laser power and to nanoparticle content at low concentration.
Abstract: Visible radiation at resonant frequencies is transduced to thermal energy by surface plasmons on gold nanoparticles. Temperature in ≤10-microliter aqueous suspensions of 20-nanometer gold particles irradiated by a continuous wave Ar+ ion laser at 514 nm increased to a maximum equilibrium value. This value increased in proportion to incident laser power and in proportion to nanoparticle content at low concentration. Heat input to the system by nanoparticle transduction of resonant irradiation equaled heat flux outward by conduction and radiation at thermal equilibrium. The efficiency of transducing incident resonant light to heat by microvolume suspensions of gold nanoparticles was determined by applying an energy balance to obtain a microscale heat-transfer time constant from the transient temperature profile. Measured values of transduction efficiency were increased from 3.4% to 9.9% by modulating the incident continuous wave irradiation.