Study on measurement technology of thermal gas flow based on effective velocity

摘要

At low gas velocity, the effect of natural convection on the measurement of thermal gas flow is studied by theoretical-experimental method. In this paper, taking the horizontal thermal probe as the study object, natural convection heat transfer from the thermal probe is analyzed and the velocity corresponding to natural convection (VCNC) is solved. According to the method of vector synthesis, the effective velocity corresponding to forced convection is obtained. A new correction formula based on the effective velocity, for the measurement of the gas mass flow, is presented. Experimental investigation is carried out in the medium pressure closed-loop gas flow device in Tianjin University. The gas velocity is varied from 0.1 to 3.5m/s, resulting in VCNC in the ranges of 1.755m/s to 2.372m/s. The reference error of gas mass flow is controlled within 2.49%.