Ordinary Thermodynamics provides reliable results for problems with fairly smooth and slowly varying fields. For rapidly changing fields or steep gradients Extended Thermodynamics (ET) [1] provides better results. The new version of ET, the so-called Consistently Ordered Extended Thermodynamics [2], assigns an order of magnitude in steepness to the variables. In [2] the authors use as variables the moments G, constructed from the irreducible parts of Hermite polynomials in the components c i of the atomic velocity. With this choice of variables the closure is automatic once an order is assigned to a process. But, in terms of the G's, the equations look complicated and it is quite difficult to derive them. In this paper we consider the equations in terms of the usual F-moments, constructed with simple polynomials in c i . By assigning an order to the variables, we derive the field equations appropriate to two different one-dimensional processes: heat conduction in a gas at rest and heat conduction with one-dimensional motion. Comparison with [2] shows that the sets of the field equations coincide, but, in terms of the F's, the equations are less complicated and they may be obtained easily.

### Consistently ordered extended thermodynamics - a proposal for an alternative method

#### Abstract

Ordinary Thermodynamics provides reliable results for problems with fairly smooth and slowly varying fields. For rapidly changing fields or steep gradients Extended Thermodynamics (ET) [1] provides better results. The new version of ET, the so-called Consistently Ordered Extended Thermodynamics [2], assigns an order of magnitude in steepness to the variables. In [2] the authors use as variables the moments G, constructed from the irreducible parts of Hermite polynomials in the components c i of the atomic velocity. With this choice of variables the closure is automatic once an order is assigned to a process. But, in terms of the G's, the equations look complicated and it is quite difficult to derive them. In this paper we consider the equations in terms of the usual F-moments, constructed with simple polynomials in c i . By assigning an order to the variables, we derive the field equations appropriate to two different one-dimensional processes: heat conduction in a gas at rest and heat conduction with one-dimensional motion. Comparison with [2] shows that the sets of the field equations coincide, but, in terms of the F's, the equations are less complicated and they may be obtained easily.
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2005
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Utilizza questo identificativo per citare o creare un link a questo documento: `https://hdl.handle.net/11570/1432953`
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