Abstract
a pressure regulator is an essential equipment during delivering natural gas to consumers with the help of pipe lines at present, but the potential pressure energy of high-pressure natural gas is not recovered. So a gas expander is employed to replace some regulators to recovery pressure energy during the expansion of high-pressure natural gas as possible and transfer to mechanical work. And then a numerical model is established based on the First Law and second Law of thermodynamics to analyze the variation of gas expander outlet temperature, the variation of preheating load of natural gas and the influence of the isentropic efficiency of gas expander during the expansion of natural gas. The results show that applications of the gas expander lead to a much lower outlet temperature of natural gas than that of regulators, which aggravate the formation of natural gas hydrate and so preheating the natural gas is necessary before natural gas entering the gas expander to prevent from the formation of natural gas hydrate. The gas expander brings about a much lower specific enthalpy of natural gas than that of regulators at outlet and then the preheating load increases to 3 times of itself. For different type of gas expanders the preheating load of natural gas increases linearly with the isentropic efficiency of the gas expander while the outlet temperature of natural gas reduces linearly with the isentropic efficiency. For a determined turbine gas expander the preheating load of natural gas increases approximately linear with the increase of natural gas volume flow lower than its rated volume flow, while the influence of volume flow larger than its rated volume flow on preheating load natural gas is very low.
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