Nature of dynamic errors in measuring pulsating temperatures of a gas flow with a pulsating speed

Abstract

1. The displacement of the mean level in the synchronous oscillations of temperature with respect to heat-exchange is due to the thermal inertia of the body. The displacement increases with rising thermal inertia. As a working hypothesis it can be assumed that, in the same manner as the quenching of the amplitude of temperature oscillations is determined by the product of∈ω, the nature of the displacement also depends on the value of this product. 2. If the value of∈ω remains in the range of 0.003〈∈ω〈 0.5, the relative displacement of the mean level of temperature oscillations in heat collectors increases monotonically with frequency. For values of∈ω〈 0.003 the value of the relative displacement M/A1 is, it would appear, so small that it need not be considered in working out the results of the recorded variable temperatures. 3. For values of∈ ω〈 0.5 the value of M/A1 becomes independent of frequency. A certain rise observed in all the curves at frequencies of 0.1 and 0.2 cps is due, it would appear, to omitted systematic errors whose values, however, do not exceed the above-mentioned quadratic mean error. 4. The absolute displacement value not only depends on the oscillation amplitude of temperature and heat exchange (and the value of∈ω) but also on the shape of their curves. For a sinusoidal shape of the heat-exchange variations curve, the observed displacement values were smaller than those recorded on the PITT equipment. It follows from the above that the experimental determination of the error in measuring the mean level of temperature oscillations in a gas flow should be carried out with an equipment capable of reproducing even approximately the shape of the curve of temperature and heat-exchange oscillations which occur in the operating conditions of the heat collector.