Experimental evaluation of thermal mass smart meters influence factors

New static thermal mass principle is a very promising technology for gas flow-metering since it offers very significant potential such as digital output, absence of moving parts, direct mass measurement. Unfortunately, gas quality is expected to affect metrological performance of thermal mass flow-meters (TMFs), as far as flow disturbances and such conditions often occur in modern networks. In this paper the authors investigate the sensitivity of TMFs with natural gas quality changes and different flow disturbances. To this end, a metrological test campaign has been carried out through specifically designed laboratory test bench and facilities. The results of the tests with gas quality changes show the capillary TMFs are able to recognize the natural gas flowing strictly included in the EN 437 group H and to consequently apply specific correction factors. On the other hand, capillary TMFs have been found sensitive to high contents of CO2 and N2, like in biogas and natural gases at the borders of group H. Finally, flow disturbances tests show the accuracy of full bore insertion in line TMFs is affected by the interaction between sensor and piping both for double out-of plane bend and single 90° bend disturbances