Kopal, Ivan

Kučerová, Jana

Mokryšová, Martina

Ružiak, Ivan

English

DSpace at VSB Technical University of Ostrava

TIN LIB} - Sborník vědeckých prací Vysoké školy.báňské-Technické univerzity Ostrava, číslo 1, rok 2009, ročník Lil, řada hutnická článek č. 1440 NORMALITY TEST OF COOLED SOLID TIME CONSTANT I. KOPAL*, I. RUŽIAK, M. MOKRYŠOVÁ, J. KUč;EROVÁInstitute o/ Materlal and Technological Research, Faculty o/ lndllstrial Technologies, Alexander Dublek University o/ Trentin; Púchov, Slovak Republic, contact author: kopal@fpt.tn unLsk ABSTRACT: The article deals with the practical identification of the thermal time constant of a first­order thennal system of a solid cooled in the fluid. The nocmality test for an empirical data set produced by calculations of the thermal time constant from a linearized time history of the coole·d solid surface temperature in the process of its cooling is discussed. Article also introduces an algorithm of identification of an optimal time interval for reliable most probable value of time constant estimation. 11 KEY WORDS: first-order exponential model, thermal time constant, Lilliefors test for normality 1. INTRODUCTIONIn the beat transfer analysis some solids are observed to behave li.ke a "lump" whose entire temperature remains esseritially uniformed at all times during a beat transfer process. The temperature of such solids can be taken to be a function of time only. It can be represented by a solid surface temperature time history. H_eat transfer analysis which utilizes this idealization is very well known as lumped system analysis. It is applicable only when the Biot number (the ratio of intemal thermal resistance within the solid to extemal thennal resistance at the sfilface of the solid) is less than or equal to 0.1.In the case of moveless solid which is cooled without heat sources or absorbents in a stagnant incompressible fluid with negligible volume of extensibility, the solid surface temperature time history can be described by a first-order exponential model in the form of (1) with the thennal time constant of cooled solid thennal system -r, fluid temperature T00 and maximum solid temperature To. Thermal time constant, which represents very notable characteristic of a cooling process kinetics frequently exploited in various ranges of material engineering [1, 2], can be computed from a linearized temperature time history (1) by using equation [3, 4] r (2) However, the time constant computation from an experimental temperature time history of the cooled solid usually produces a time series of time constant values with unknown mean and variance instead of one constant value, because of presence of a noise. Time window in which this time series comes from a normal probability distribution can be used for practical time constant estimation. A Lilliefors test is a suitable parametric statistical test for finding out in which time window does the time constant have a norma! distribution. 66 

Normality test of cooled solid time constant

http://dspace.vsb.cz/bitstream/10084/71380/2/VSB%20HUF%202009-1_18_Kopal.pdf

Normality test of cooled solid time constant

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