| 摘要 |
The apparatus comprises a chamber 4 to which a gas in question, for example natural gas is supplied through inlet 6 and leaves through outlet 8. The speed of sound SoS at ambient temperature is measured using any suitable method such as electronic control and calculating means 14 and an ultra-sound emitter 10 and an ultra-sound receiver 12. The ambient temperatures T a is observed by temperature sensor 22, and a thermal conductivity sensor measures the thermal conductivity of the gas at two different temperatures above ambient temperature. One value ThC H of the thermal conductivity is measured at 70‹C above ambient and the other value ThC L of the thermal conductivity is measured at 50‹C above ambient. The control means 14 calculates the calorific value CV of the gas according to the formula CV= a.ThC H + b.ThC L + c.SoS + d.T a + e.T a <SP>2</SP>+ f. where a,b,c,d,e and fare constants. |
