The heat rate kinetics on the liquefied hydrocarbon gases sensing and food quality control detecting strategy

Abstract

The sensing and monitoring of liquefied hydrocarbon gases, in the petroleum industries, is central to hazard prevention. Many sensors have been fabricated to detect these flammable petroleum gases, such as the liquefied petroleum gas (LPG). It has been shown that the sensor's operating temperature is a key in determining its sensitivity. In many instances, this temperature is kept as a fixed parameter during the gas sensing measurements. That is the optimal operating temperature where sensors performances are significantly high. However, this parameter becomes unstable on exposure of the sensor to liquefied petroleum gas, depending largely on the gas concentrations. This fluctuation in operating temperature results in the sensor's electric current or resistance oscillating indefinitely for as long as gas is present. Herein, a new simple mathematical expression following the Fourier's conduction law is devised to explain this anomaly. The relation between the heat transfer kinetics and the semiconducting metal oxide (SMO) sensor's electrical conduction is also established. In addition, this SMO sensor was tested at 200 °C with plant hormone odours of vegetables and fruit to evaluate their off-shelf freshness as they undergo ripening processes. These plants showed a dramatic increase in respiration rate during their maturation or ripening process over several days. The SMO sensor based on magnesium ferrite doped with cerium (MgCexFe2-xO4) proved to be very stable over a period of 18 months.