Evaporative heat exchanger development
Tang, Lecheng Samuel
Date of Issue2016-05-30
School of Mechanical and Aerospace Engineering
Natural gas will one day become the main fossil fuel that the world consumes as the global source of oil continues to dwindle. Current trends have begun to show an ever- increasing demand for natural gas. With the transportation of natural gas in mind, liquefied natural gas (LNG) development has gained significance. Regasification of LNG is usually coupled with cold energy utilisation due to its economic benefits. One method of utilising cold energy is the use of combined power-cycle where low temperature waste heat can be converted to provide energy for power generation. The development of an evaporative heat exchanger comes into prominence because the efficiency of this heat exchanger would affect the overall efficiency of the power generation system. The efficiency of a heat exchanger is closely related to its convective heat transfer coefficient. In this project, a test section would be designed to be similar to the heat exchanger and several experiments was conducted to determine the relationship between convective heat transfer coefficient and heat flux in the test section. It was observed that the convective heat transfer coefficient increases linearly with heat flux, from 200 W/m2K to 400W/m2K Parameters such as: the Reynolds number, subcooling temperature, and the configuration of the test section, were varied and observed to see whether they affect the convective heat transfer coefficient. The results show that Reynolds number does not alter the relationship between the convective coefficient and heat flux. Subcooling temperature would affect the heat flux required for boiling to occur. The horizontal configuration would reduce the overall heat transfer coefficient due to the entrapment of water vapour. For future projects, similar experiments may be carried out with the use of cryogenics for more realism. Hot flow may also be introduced instead of using heaters to provide more realistic results.
Final Year Project (FYP)
Nanyang Technological University