DEVELOPMENT OF VOLUME TO MASS CONVERSION MODEL FOR NGV DISPENSING UNIT USING THERMODYNAMIC PROPERTIES

This research project is initiated as one of the sub studies in the implementation of natural
gas vehicle usage in Malaysia. Developing a natural gas refueling station at lower cost is
a challenge that needs to be handled by the university. One of the areas of interest is in
the metering system. Regulatory requirement states that natural gas must be measured in
mass flow rate. Coriolis meter is the only available mass flow meter in the market. But
this meter is too costly. Thus a study to develop a cheaper metering system is required.
The best alternative is by measuring the flow rate of natural gas and then converts it to
mass flow rate. This conversion can be done in various ways of calculations. Manual
calculation using Equation of State, combination of several Equations of State and
Activity Coefficient Method are the most commonly used method of calculation for
natural gas component. The author used several equations of state in order to complete
this research. But first, the properties of the natural gas such as its composition, vapor
pressure and critical properties need to be determined first.
The calculation starts with the study to find the variation in mass as pressure of the
natural gas is changed. For this calculation purpose, the tank is considered as an
isothermal system with temperature maintained at 30°C. The system that been studied is
theNGV's tank which volume is constant (55 liters). The calculation is done using Soave
Redlich Kwong EOS and Peng Robinson EOS. To compare the data with the ideal
condition, a plot using ideal gas equation is done as well. The calculation is repeated at
different composition to see how the variations in composition affect the behavior of the
graph.
Finally, the variation in mass as a function of temperature and pressure is done. At this
stage, HYSIS is used to determine the data for the plot. The equations that been
considered in the calculation are Soave Redlich Kwong EOS, Peng Robinson EOS and
LeeKesler Plocker EOS. The graphs areplotted to seethe relationship.