Abstract
The inverse problem of determining time-variable surface heat flux in a plane wall, with constant or temperature dependent thermal properties, is numerically studied. Different kinds of incident heat flux, including rectangular waveform, are assumed. The solution is numerically solved as a function estimation problem, so that no a priori information for the functional waveforms of the unknown heat flux is needed. In all cases, a solution in the form of a piece-wise function is used to approach the incident flux. Transient temperature measurements at the boundary, from the solution of the direct problem, served as the simulated experimental data needed as input for the inverse analysis. Both direct and inverse heat conduction problems are solved using the network simulation method. The solution is obtained step-by-step by minimising the classical functional that compares the above input data with those obtained from the solution of the inverse problem. A straight line of variable slope and length is used for each one of the stretches of the desired solution. The influence of random error, number of functional terms and the effect of sensor location are studied. In all cases, the results closely agree with the solution.
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Abbreviations
- a, b:
-
constant in Eq. 19
- c e :
-
specific heat, J kg−1 C−1
- C :
-
capacitor, F
- e :
-
average relative error in Eq. 24
- F :
-
functional defined in Eq. 18
- G :
-
voltage-control current source
- h :
-
heat transfer coefficient, W m−2 C−1
- J :
-
electric current variable, A
- j :
-
heat flux rate, W m−2
- j1, j2:
-
constants
- k :
-
thermal conductivity, W m−1 C−1
- K :
-
constant in computational procedure
- L :
-
thickness of the slab
- n :
-
first value of temperature within the functional
- N :
-
number of volume elements
- r :
-
regularisation parameter
- R :
-
resistor
- t :
-
time, s
- t 1 :
-
constant
- T :
-
temperature, C
- V :
-
voltage, V
- x :
-
spatial co-ordinate
- δ:
-
convergence criteria
- ε:
-
random error value
- σ:
-
standard deviation
- μ:
-
random variable
- ρ:
-
density, kg m−3
- ω:
-
angular frequency
- Δx:
-
thickness of the control volume
- Δt:
-
time interval temperature measurement
- sur:
-
surrounding medium
- C:
-
referred to the capacitor
- d :
-
number of iterations
- f :
-
referred to particular location at the slab
- est:
-
values estimated of fluxes
- exact:
-
values exacts of fluxes
- i :
-
connected to the volume element i, 1≤ i≤ N; also, centre of the volume element
- i±Δ:
-
right and left ends of the volume element
- in:
-
incident
- inv:
-
refers to the solution of the inverse problem
- s :
-
1, 2, ..., m
- m :
-
natural number (total number of temperature measurements)
- n :
-
refers to the first temperature with the stretch
- o:
-
associated to the initial condition
- z :
-
1, 2,... Z, in Eq. 18
- Z :
-
number of stretches of the piece-wise function in the IHCP
- ∞:
-
value infinite
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Zueco, J., Alhama, F. & González Fernández, C.F. Numerical nonlinear inverse problem of determining wall heat flux. Heat Mass Transfer 41, 411–418 (2005). https://doi.org/10.1007/s00231-004-0553-1
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DOI: https://doi.org/10.1007/s00231-004-0553-1