US 4,059,982 A · Apparatus for the measurement of thermal properties of biomaterials

Abstract

Appropriate heating and temperature sensing means are immersed in a medium the thermal conductivity, k, and thermal diffusivity, .alpha., of which are to be determined both in the presence of and in the absence of a flow of fluid therethrough. The method and system used for making such measurements operate in accordance with a thermal model of the heating means and the medium wherein the heating means is treated as a distributed thermal mass and wherein heat conduction occurs in a coupled thermal system which comprises both the heating means and the adjacent region of the medium which surrounds such heating means. The thermal conductivity of the medium is determined as a function of the temperature difference between the temperature of the unheated medium and the temperature of the heated medium, of the resistance of the heating means, of the power applied to the heating means, of the thermal conductivity of the heating means and of the radius of a spherical heating means having a volume equivalent to that of the actual heating means. In accordance with various embodiments of the invention the temperature difference and heating means resistance are maintained constant or are permitted to vary with time over the time period of measurement. Measurements of the thermal conductivity in the presence and in the absence of fluid flow permit a further measurement to be made of the rate of flow, .omega., of a fluid which is flowing through the medium.

Claims32

Dependent claims

A method for determining physical characteristics of a medium comprising the steps of

predetermining the thermal conductivity of a heating means as a function of temperature, said heating means having a predetermined resistance versus temperature relationship;
immersing said heating means in said medium;
determining the reference temperature of said medium when said medium is unheated;
applying power to said heating means sufficiently rapidly to heat said means to a volume mean temperature above said reference temperature so that the power necessary to maintain said volume mean temperature varies as a function of time;
determining the time varying relationship between the power required to maintain said heating means at said volume mean temperature after said temperature has been reached and the time during which said power is being applied thereto;
determining the temperature difference between said volume mean temperature and said reference temperature and determining the resistance of said heating means at said volume mean temperature;
determining the thermal conductivity of said medium as a function of said temperature difference, of the resistance of said heating means at said volume mean temperature, of said applied power in accordance with said time varying power and time relationship, of said predetermined thermal conductivity of said heating means, and of at least one characteristic dimension of said heating means in accordance with a thermal model of said heating means and said medium in which it is immersed wherein said heating means is treated as a distributed thermal mass and wherein heat conduction occurs in a coupled thermal system which comprises both the heating means and the adjacent region of said medium which surrounds said heating means.

4 more elements

Apparatus for determining physical characteristics of a medium comprising

means immersed in said medium for sensing the reference temperature of said medium when said medium is unheated;
means immersed in said medium for heating said medium, said heating means having a predetermined thermal conductivity, a predetermined thermal diffusivity and a predetermined characteristic dimension;
means for applying power to said heating means sufficiently rapidly to raise the temperature of said heating means to a volume mean temperature above said reference temperature so that the power necessary to maintain said volume mean temperature varies as a function of time;
data processing means for determining the temperature difference between said volume mean temperature and said reference temperature, for determining the resistance of said heating means at said volume mean temperature and for determining the time varying relationship between the power required to maintain said heating means at said volume mean temperature after said temperature has been reached and the time during which said power is being applied thereto;
said data processing means further being responsive to said temperature difference, said heating means resistance, said applied power in accordance with said time varying power and time relationship, said predetermined thermal conductivity of said heating means, and said predetermined characteristic dimension of said heating means for determining the thermal conductivity of said medium in accordance with a thermal model of said heating means and said medium wherein said heating means is treated as a distributed thermal mass and wherein heat conduction occurs in a coupled thermal system which comprises both the heating means and the adjacent region of said medium which surrounds said heating means.

2 more elements

Dependencies are inferred from the claim text.

Apparatus for the measurement of thermal properties of biomaterials

Life of this patent

Apparatus for the measurement of thermal properties of biomaterials

Life of this patent

Abstract

Claims32