Gasification of LNG using a Brayton cycle associated to a heat transfer fluid loop and a heat pump

The market of liquefied natural gas (LNG) is growing and presents the advantage of diversifying supplies. The LNG is fed at a temperature of -162 deg. C and at atmospheric pressure. The main objective of the thesis aims at the valorization of the LNG exergy during its gasification and heating before being delivered through the network. The thesis investigates a new concept of gasification that differs from the current developments by the use of ambient air as the only heat source and by partial valorization of the LNG exergy in mechanical energy. An energy and exergy analysis helped to the definition of engine-cycle architectures using the air heating capacity as a heat source (recovered by an intermediate fluid, here propane) and LNG as a cold sink. The use of ambient air led to manage frosting and defrosting cycles on the evaporators of intermediate fluid recovering heat from the air. This requires understanding the coupled heat and mass-transfer phenomena. A test bench was built to characterize Circular Finned-Tube Heat Exchangers in frosting conditions and to validate a numerical model simulating the behavior of such heat exchangers in presence of frost. As a result, a logic for the design and operation of air heat exchangers is proposed taking into account the frosting effect. A seasonal study showed that the output power generated by the new concept of gasification is superior to its energy consumption throughout the year. (author)