Inverse problem of estimating space and time dependent hot surface heat flux in transient transpiration cooling process

2009 ◽  
Vol 48 (7) ◽  
pp. 1398-1404 ◽  
Author(s):  
Junxiang Shi ◽  
Jianhua Wang
Keyword(s):  
Heat Flux ◽  
Inverse Problem ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Time Dependent ◽  
Transpiration Cooling ◽  
Cooling Process ◽  
Space And Time ◽  
Hot Surface

scholarly journals Thermally Forced Transients in the Thermohaline Circulation

2015 ◽  
Vol 45 (11) ◽  
pp. 2820-2835 ◽  
Author(s):  
Michael A. Spall
Keyword(s):  
Heat Flux ◽  
Surface Heat Flux ◽  
Thermohaline Circulation ◽  
Numerical Models ◽  
Ocean Basin ◽  
Surface Heat ◽  
Meridional Overturning Circulation ◽  
Time Dependent ◽  
Boundary Current ◽  
Model Calculations

AbstractThe response of a convective ocean basin to variations in atmospheric temperature is explored using numerical models and theory. The results indicate that the general behavior depends strongly on the frequency at which the atmosphere changes relative to the local response time to air–sea heat flux. For high-frequency forcing, the convective region in the basin interior is essentially one-dimensional and responds to the integrated local surface heat flux anomalies. For low-frequency forcing, eddy fluxes from the boundary current into the basin interior become important and act to suppress variability forced by the atmosphere. A theory is developed to quantify this time-dependent response and its influence on various oceanic quantities. The amplitude and phase of the temperature and salinity of the convective water mass, the meridional overturning circulation, the meridional heat flux, and the air–sea heat flux predicted by the theory compare well with that diagnosed from a series of numerical model calculations in both strongly eddying and weakly eddying regimes. Linearized analytic solutions provide direct estimates of each of these quantities and demonstrate their dependence on the nondimensional numbers that characterize the domain and atmospheric forcing. These results highlight the importance of mesoscale eddies in modulating the mean and time-dependent ocean response to atmospheric variability and provide a dynamical framework with which to connect ocean observations with changes in the atmosphere and surface heat flux.

Heat Transfer During Liquid Contact on Superheated Surfaces

1995 ◽  
Vol 117 (3) ◽  
pp. 693-697 ◽  
Author(s):  
J. C. Chen ◽  
K. K. Hsu
Keyword(s):  
Heat Flux ◽  
Atmospheric Pressure ◽  
Surface Heat Flux ◽  
Temperature Data ◽  
Surface Heat ◽  
Transient Temperature ◽  
Time Varying ◽  
Wall Superheat ◽  
Hot Surface ◽  
Better Than

Several boiling regimes are characterized by intermittent contacts of vapor and liquid at the superheated wall surface. A microthermocouple probe was developed capable of detecting transient surface temperatures with a response time better than 1 ms. The transient temperature data were utilized to determine the time-varying heat flux under liquid contacts. The instantaneous surface heat flux was found to vary by orders of magnitude during the milliseconds of liquid residence at the hot surface. The average heat flux during liquid contact was found to range from 105 to 107 W/m2 for water at atmospheric pressure, as wall superheat was varied from 50 to 450°C.

Surface heat transfer coefficient measurement by immersed temperature sensor and inverse modelling

2016 ◽  
Vol 83 (11) ◽  
Author(s):  
Mirko Javurek ◽  
Andreas Mittermair
Keyword(s):  
Heat Flux ◽  
Inverse Problem ◽  
Flux Density ◽  
Temperature Sensor ◽  
Surface Heat Flux ◽  
Heat Flux Density ◽  
Surface Heat ◽  
Problem Solution ◽  
Inverse Problem Solution

AbstractA transient surface heating or cooling process of a solid is considered. A procedure for the determination of surface temperature and surface heat flux density during such a process is presented using a submersed temperature sensor in the solid. From this measured temperature the surface temperature and surface heat flux density are calculated by inverse process modelling. This method is prone to errors since measurement errors are amplified in the inverse process modelling and can thus easily become unacceptably large. The LSQR regularisation algorithm is optimised for fast performance as well as less memory requirement and applied to the inverse problem solution. The proposed method allows to simulate an experimental setup and to determine the accuracy of the results gained from the simulated experiment. This is essential for the determination of the accuracy of a planned or existing test facility. The influence of process parameters like sensor depth, sensor noise level, sampling rate, heat flux density amplitude and cooling/heating process duration is investigated. In most cases it is very important to carefully adjust the process parameters in order to obtain reliable and accurate results. Additionally the proper selection of the regularisation parameter required for the inverse problem solution is analysed.

Numerical Solutions to an Inverse Problem of Heat Conduction for Simple Shapes

1960 ◽  
Vol 82 (1) ◽  
pp. 20-25 ◽  
Author(s):  
G. Stolz
Keyword(s):  
Heat Flux ◽  
Inverse Problem ◽  
Heat Conduction ◽  
Numerical Methods ◽  
Surface Heat Flux ◽  
Direct Problem ◽  
Numerical Solutions ◽  
Superposition Principle ◽  
Surface Heat ◽  
Numerical Inversion

Numerical methods are presented for solving an inverse problem of heat conduction: Given an interior temperature versus time, find the surface heat flux versus time. The analysis is developed specifically for spheres; it applies to other simple shapes. The system is treated as linear, permitting use of the superposition principle. The essence of the method is the numerical inversion of a suitable direct problem: Given a surface heat flux versus time, find an interior temperature versus time. Care is required in selecting a time spacing for, if it is chosen too small in relation to the conditions, undesirable oscillation results. Simplifying suggestions are presented, and the use of the methods are illustrated by examples.

MAXIMUM SURFACE HEAT FLUX DURING JET IMPINGEMENT QUENCHING OF VERTICAL HOT SURFACE

2015 ◽  
Vol 22 (3) ◽  
pp. 199-219 ◽  
Author(s):  
C. Agarwal ◽  
Ravi Kumar ◽  
Akhilesh Gupta ◽  
Barun Chatterjee
Keyword(s):  
Heat Flux ◽  
Surface Heat Flux ◽  
Jet Impingement ◽  
Surface Heat ◽  
Maximum Surface ◽  
Hot Surface

The Effect of Dissolving Salts in Water Sprays Used for Quenching a Hot Surface: Part 2—Spray Cooling

2003 ◽  
Vol 125 (2) ◽  
pp. 333-338 ◽  
Author(s):  
Qiang Cui ◽  
Sanjeev Chandra ◽  
Susan McCahan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Spray Cooling ◽  
Surface Heat ◽  
Water Sprays ◽  
Nucleate Boiling Heat Transfer ◽  
Hot Surface

The effect of adding one of three salts (NaCl, Na2SO4 or MgSO4) to water sprayed on a hot surface was studied experimentally. A copper test surface was heated to 240°C and quenched with a water spray. The variation of surface temperature during cooling was recorded, and the surface heat flux calculated from these measurements. Surface heat flux during cooling with pure water sprays was compared with that obtained using salt solutions. Dissolved NaCl or Na2SO4 increased nucleate boiling heat transfer, but had little effect on transition boiling during spray cooling. MgSO4 increased both nucleate and transition boiling heat flux. Enhanced nucleate boiling was attributed to foaming in the liquid film generated by the dissolved salts. MgSO4 produced the largest increase in nucleate boiling heat transfer, Na2SO4 somewhat less and NaCl the least. A concentration of 0.2 mol/l of MgSO4 produced the greatest heat flux enhancement; higher salt concentrations did not result in further improvements. During transition boiling particles of MgSO4 adhered to the heated surface, raising surface roughness and increasing heat transfer. Addition of MgSO4 reduced the time required to cool a hot surface from 240°C to 120°C by an order of magnitude.

Effect of jet diameter on the maximum surface heat flux during quenching of hot surface

2013 ◽  
Vol 265 ◽  
pp. 727-736 ◽  
Author(s):  
Chitranjan Agrawal ◽  
Ravi Kumar ◽  
Akhilesh Gupta ◽  
Barun Chatterjee
Keyword(s):  
Heat Flux ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Maximum Surface ◽  
Hot Surface
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