A Study on Liquified Petroleum Gas(LPG) Fuel Quantitative Method using Coriolis Mass Flowmeter

코리올리 질량유량계를 이용한 액화석유가스(LPG) 정량 측정 방법 연구

Abstract

Domestic LPG meters are being tested for LPG quantification in accordance with the "Measures Act". The LPG meter is re-tested every three years in accordance with the "Enforcement Decree of the Measures Act". The maximum permissible error within the test is within ${\pm}1.0%$, and the tolerance is within ${\pm}1.5%$. For the quantitative measurement of LPG, a hydrometer for LPG, a balance, and a pressure vessel are used. The volume of LPG varies in depending on the temperature and pressure. The current quantitative measurement method of LPG requires the measurement of temperature, pressure and density in order to determine the volume of LPG, respectively, and some equipments are needed accordingly. Coriolis mass flowmeter, on the other hand, measure the mass flow, density and temperature at the same time, and can be converted and calculated to the required values using a computer program, also it is widely applied in the industrial field. In this study, the volume of LPG was measured using a Coriolis mass flowmeter as a basic study of LPG quantitative measurement. In addition, it is shown that it is possible to apply for the LPG quantitative measurement using the Coriolis mass flowmeter by comparing it with the conventional LPG quantitative measurement method.

국내 LPG 미터는 "계량에 관한 법률"에 의거 LPG 정량에 대한 검사가 실시되고 있다. LPG 미터는 "계량에 관한 법률 시행령"에 따라 3년마다 재검정이 실시된다. 검사 시 최대허용오차는 ${\pm}1.0%$ 이내, 사용오차는 ${\pm}1.5%$ 이내이다. 정량 측정 시에는 밀도부액계, 저울, 압력용기를 사용한다. LPG는 온도와 압력에 따라 부피 변화의 정도가 매우 심하다. 현행 정량 측정 방법은 LPG의 부피를 구하기 위해 온도 및 압력, 밀도를 측정해야 하며, 이에 따른 장비들이 필요하다. 반면에 코리올리 질량유량계는 질량유량, 밀도, 온도를 동시에 측정하며, 컴퓨터 프로그램을 사용하여 측정값을 필요한 값으로 변환 및 산출 할 수 있어, 산업현장에서 널리 적용되고 있다. 본 연구에서는 LPG 정량 측정에 대한 기초연구로서, 코리올리 질량유량계를 이용하여 LPG 충전기에서 나온 LPG 부피를 측정했다. 또한, 기존 LPG 충전기 검사방법과의 비교를 통해 코리올리 질량유량계를 이용한 LPG 충전기 검사도 가능하다는 결론을 얻었다.

Fig. 1. Examples of LPG quantitative measuring equipment in Australia(A) and Turkey(B).

Fig. 2. Examples of LPG quantitative measuring vehicle in Australia(A) and Turkey(B).

Fig. 3. Example of LPG meter with recovery line.

Fig. 4. Principle of Coriolis mass flowmeter.

Fig. 5. LPG hydrometer(A) and cylinder(B).

Fig. 6. Electric balance(A) and pressure vessel(B).

Fig. 7. Equipment(A) and program(B) for measuring amount of LPG in Hizen Inc..

Fig. 8. LPG mass equipment of Endress+Hauser.

Fig. 9. Procedure of current method for measuring LPG

Fig. 10. Procedure of new method for measuring LPG

Fig. 11. Comparison of the measurement error between two methods.

Table 1. Examples of general Coriolis mass flowmeter applications

Table 2. Specifications of LPG mass

Table 3. Results of density(15 ℃) using the new and current method

Table 4. Result of LPG weight using the new and current method

Table 5. Result of volume(20 L) using the new and current method

Table 6. The coincidence rate between two methods

Table 7. The volume of measurement and standard deviation of the measurement error using new method

Table 8. The volume of measurement and standard deviation of the measurement error using current method