Thermal Transport Phenomena in Buoyancy-Driven Nanofluids

2004 ◽  
Author(s):  
A. G. Agwu Nnanna ◽  
Tom Fistrovich ◽  
Kurt Malinski ◽  
S. U. S. Choi
Keyword(s):  
Thermal Transport ◽  
Buoyancy Force ◽  
Transport Phenomena ◽  
Temperature Response ◽  
Temperature Data ◽  
Steady State Temperature ◽  
Vertical Walls ◽  
Circulatory Motion ◽  
Heat Loads ◽  
Transient And Steady State

This paper presents an experimental investigation of the thermal transport phenomena in buoyancy-driven nanofluids. The experimental model for this study is a rectangular enclosure with differentially heated vertical walls and adiabatic horizontal walls. The nanofluids were confined within the enclosure. Simulations were performed to measure the transient and steady-state temperature response of the nanofluids to applied load. Experimental observation shows settling of the nanoparticle at low heat loads and a remixing of the nanofluid at higher loads. At high loads, the buoyancy force increased hence increasing the re-circulatory motion of the nanofluid. This may be one method of addressing the settling of nanoparticles in nanofluid. For natural convection in an enclosure, this paper shows that the thermal behavior of nanofluids is identical to pure fluids. Temperature data collected during the experiment were used to study the variation of Nusselt number with Rayleigh number.

scholarly journals Mechanical Fault Detection on Electrical Machine: Thermal Analysis of Small Brushed DC Motor with Faulty Bearing

2018 ◽  
Vol 225 ◽  
pp. 05012
Author(s):  
Abbas A. Wahab ◽  
N. Fatimah Abdullah ◽  
M.A.H. Rasid
Keyword(s):  
Thermal Analysis ◽  
Steady State ◽  
Direct Current ◽  
Dc Motor ◽  
Temperature Data ◽  
Electrical Machine ◽  
Financial Loss ◽  
Data Logger ◽  
Steady State Temperature ◽  
Using Data

Direct current motors (DC motor) are used in the small electric devices commonly. DC motor are cheap and easy to install, thus their popularity. Despite the popularity, faults occur which make diagnosis and detection of faults very important. It avoids financial loss and unexpected shutdown operation causes by these faults. This paper presents an analysis of temperature profile of the much famous small Brushed DC motor with a faulty bearing. The temperature data of healthy DC motor and DC motor with faulty bearing were measured by thermocouple and recorded using data logger in real time until steady state temperature, under different load. The analysis on the steady state temperature allow to conclude that bearing fault can clearly be recognised through characteristics temperature difference with a healthy motor.

Thermal Modeling of Absolute Cryogenic Radiometers

1994 ◽  
Vol 116 (4) ◽  
pp. 993-998 ◽  
Author(s):  
Z. M. Zhang ◽  
R. U. Datla ◽  
S. R. Lorentz ◽  
H. C. Tang
Keyword(s):  
Thermal Modeling ◽  
Random Noise ◽  
Electrical Power ◽  
Kinetic Inductance ◽  
Thermal Impedance ◽  
The Finite Element Method ◽  
Resistance Thermometer ◽  
Steady State Temperature ◽  
Radiant Power ◽  
Transient And Steady State

This work consists of a detailed thermal modeling of two different radiometers operated at cryogenic temperatures. Both employ a temperature sensor and an electrical-substitution technique to determine the absolute radiant power entering the aperture of a receiver. Their sensing elements are different: One is a germanium resistance thermometer, and the other is a superconducting kinetic-inductance thermometer. The finite element method is used to predict the transient and steady-state temperature distribution in the receiver. The nonequivalence between the radiant power and the electrical power due to the temperature gradient in the receiver is shown to be small and is minimized by placing the thermometer near the thermal impedance. In the radiometer with a germanium resistance thermometer, the random noise dominates the uncertainty for small incident powers and limits the ultimate sensitivity. At high power levels, the measurement accuracy is limited by the uncertainty of the absorptance of the cavity. Recommendations are given based on the modeling for future improvement of the dynamic response of both radiometers.

Progress in thermal transport modeling of carbonate-based reacting systems

2017 ◽  
Vol 27 (5) ◽  
pp. 1098-1107 ◽  
Author(s):  
Lindsey Yue ◽  
Leanne Reich ◽  
Terrence Simon ◽  
Roman Bader ◽  
Wojciech Lipiński
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Chemical Kinetics ◽  
Calcium Oxide ◽  
Thermal Transport ◽  
Transport Phenomena ◽  
Chemical Energy ◽  
Packed Bed Reactor ◽  
Content Type ◽  
Reacting Systems

Purpose Carbonate-based heterogeneous reacting systems are investigated for the applications of thermochemical carbon dioxide capture and energy storage. This paper aims to review recent progress in numerical modeling of thermal transport phenomena in such systems. Design/methodology/approach Calcium oxide looping is selected as the model carbonate-based reacting system. Numerical models coupling heat and mass transfer to chemical kinetics are reviewed for solar-driven calcium oxide looping on the sorbent particle, particle bed, and reactor levels. Findings At the sorbent particle level, a transient numerical model of heat and mass transfer coupled to chemical kinetics has been developed for a single particle undergoing cyclic calcination and carbonation driven by time-periodic boundary conditions. Modeling results show cycle times impact the maximum sorbent utilization and solar-to-chemical energy efficiency. At the reactor level, a model of heat and mass transfer coupled to chemical kinetics of calcination of a packed-bed reactor concept has been developed to estimate the reactor’s performance. The model was used to finalize reactor geometry by evaluating pressure drops, temperature distributions, and heat transfer in the reactor. Originality/value Successful solar thermochemical reactor designs maximize solar-to-chemical energy conversion by matching chemical kinetics to reactor heat and mass transfer processes. Modeling furthers the understanding of thermal transport phenomena and chemical kinetics interactions and guides the design of solar chemical reactors.

scholarly journals Divers as Citizen Scientists: Response Time, Accuracy and Precision of Water Temperature Measurement Using Dive Computers

2021 ◽  
Vol 8 ◽  
Author(s):  
Celia Marlowe ◽  
Kieran Hyder ◽  
Martin D. J. Sayer ◽  
Jan Kaiser
Keyword(s):  
Response Time ◽  
Water Temperature ◽  
Temperature Measurement ◽  
Response Times ◽  
Temperature Response ◽  
Temperature Data ◽  
Global Ocean ◽  
Quality Data ◽  
Accuracy And Precision ◽  
Time Accuracy

There is a lack of depth-resolved temperature data, especially in coastal areas, which are often commonly dived by SCUBA divers. Many case studies have demonstrated that citizen science can provide high quality data, although users require more confidence in the accuracy of these data. This study examined the response time, accuracy and precision of water temperature measurement in 28 dive computers plus three underwater cameras, from 12 models. A total of 239 temperature response times (τ) were collected from 29 devices over 11 chamber dives. Mean τ by device ranged from (17 ± 6) to (341 ± 69) s, with significant between-model differences found for τ across all models. Clear differences were found in τ by pressure sensor location and material, but not by size. Two models had comparable τ to designed-for-purpose aquatic temperature loggers. 337 mean data points were collected from equilibrated temperatures in hyperbaric chamber (n = 185) and sea (n = 152) dives, compared with baseline mean temperature from Castaway CTDs over the same time period. Mean bias, defined as mean device temperature minus baseline temperature, by model ranged from (0.0 ± 0.5) to (−1.4 ± 2.1) °C and by device from (0.0 ± 0.6) to (−3.4 ± 1.0) °C. Nine of the twelve models were found to have “good” accuracy (≤0.5 °C) overall. Irrespective of model, the overall mean bias of (−0.2 ± 1.1) °C is comparable with existing commonly used coastal temperature data sets, and within global ocean observing system accuracy requirements for in situ temperature. Our research shows that the quality of temperature data in dive computers could be improved, but, with collection of appropriate metadata to allow assessment of data quality, some models of dive computers have a role in future oceanographic monitoring.

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