Densities of canola, jatropha and soapnut biodiesel at elevated temperatures and pressures

► A capacitance type densitometer was used to measure the densities of fuels. ► Densities of three biodiesel fuels and diesel were measured at elevated temperatures and pressures. ► Densities of jatropha and soapnut biodiesel fuels were measured for the first time at elevated temperatures and pressures. ► The densities of diesel and biodiesel showed a linear relationship. A capacitance type densitometer was used to measure the densities of canola, jatropha and soapnut biodiesel and their blends at elevated temperatures and pressures. This densitometer is based on the principle that the capacitance of the liquid is proportional to the dielectric constant, which, in turn, is proportional to the density. Densities were measured from room temperature up to 523K and from atmospheric pressure up to 7MPa. The frequency output from the densitometer was found to have a linear relationship with temperature. It was found that density showed a linear relationship with temperature and pressure over the measured range. The measured data were regressed and the regression models were developed to represent densities as a function of temperature as well as pressure. The errors between measured and regressed densities of diesel and canola, jatropha, soapnut biodiesel were found to be less than 3%.