Thermal measuring and testing – Determination of inherent thermal property – Thermal conductivity
Patent
1980-11-13
1982-12-21
Goldstein, Herbert
Thermal measuring and testing
Determination of inherent thermal property
Thermal conductivity
364557, G01N 2518
Patent
active
043646760
DESCRIPTION:
BRIEF SUMMARY
The invention provides a meter for measuring a heat transmission coefficient of a structure such as a wall separating media having different temperatures.
BACKGROUND OF THE INVENTION
In recent years it has been more and more important to dimension the insulation of buildings in an economical manner. With increasing costs of heating it has been necessary to check and to improve such an insulation. For this purpose various techniques and arrangements for measuring heat transmission through walls have come into use. One such technique utilizes a heat camera to sense heat transfer through portions of a wall. Such techniques have been useful in establishing the existence of heat leakages in walls, which leakages one has not been earlier indentifiable. However, using that technique has the disadvantage that it requires a considerable amount of equipment and is relatively expensive.
It is therefore desirable to be able to measure heat transmission in a simple manner and to be able to survey the heat transmission in whole wall areas, windows or doors. For that purpose a meter for such a measuring task should be portable, simple to operate and it should rapidly give measuring results. The invention relates to a device for making this possible.
SUMMARY OF THE INVENTION
The present invention provides a meter for measuring a heat transmission coefficient of a wall separating media having different temperatures. The meter is highly portable, easy to operate and provides measured results rapidly. Specifically, it provides a device for measuring a heat transmission coefficient for a wall portion separating an inner media having a temperature t.sub.i and an outer median having a temperature t.sub.u, comprising, an amplifier having an input and an output, an indicator coupled to said output for indicating the measured heat transfer coefficient, first thermal sensor means adapted for sensing a temperature tv of said wall portion at a surface thereof on its inner media side, a second thermal sensor means for sensing said temperature ti of said inner media, said first and second thermal sensors being connected in an input circuit coupled to said amplifier input to provide a signal proportional to (t.sub.i -t.sub.v); and feedback circuit means coupled at least in part from said output to said input, said circuit being adjustable to provide a feedback signal to said input for causing the gain of said amplifier to be proportional to 1/(t.sub.i - t.sub.u), whereby there is developed at said output a signal proportional to A(t.sub.i -t.sub.v)/(t.sub.i -t.sub.u) indicative of said heat transmission coefficient, where A is a constant selected for calibrating said indicator to a predetermined scale.
According to the invention an electronic amplifier is used which forms the quotient between two quantities. The first quantity is the inner temperature minus the inner wall temperature and the second quantity is the inner temperature minus the outer temperature, the temperature values of the first quantity being obtained by means of thermal elements, which are connected to the device, and the second quantity being settable by adjusting a feed-back circuit of the amplifier. An output of the amplifier is supplied to an indicator graduated in units of heat transfer coefficient k.
The invention thereby starts from the following relation between the heat transmission coefficient k and the temperature which influences the measuring: radiation and for convection as well as apparatus parameters and where t.sub.i is the inner temperature in a room where the measuring is performed, t.sub.v is the inner wall temperature in said room and t.sub.u is the outer temperature outside the wall inside which the measuring is made.
Equation (1) is derived from a combination of two basic formulas describing heat flow as follows:
______________________________________ where t.sub.v
= inner wall temperature
= heat transfer coefficient (fairly
constant for the particular medium,
in this case air)
______________________________________
int
REFERENCES:
patent: 2878669 (1959-03-01), Knudson et al.
patent: 3229499 (1966-01-01), Shayeson et al
patent: 3436534 (1969-04-01), Wallace
patent: 3552185 (1971-01-01), Goode et al.
patent: 3979952 (1976-09-01), Bornstein
patent: 4236403 (1980-12-01), Poppendiek
Oja Viktor
Wikstrom Sigvard
Goldstein Herbert
Memoteknik AB
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