Regeneration of a turbogas plant: compact heat exchanger’s design

The social and political contest sensitize the entire community about the environmental pollution: the actual society lives the fight between advantages of progress and drawbacks due to exploitation of non-reusable resources. During last years lots of industries decide to develop and use different types of ‘emission free’ energy sources, to reduce as much as possible gas emission, especially CO2 ones. Over 65% of the world’s electrical energy is produced by fossil fuels, as gas turbines TG do; all these installations have the same aim: to produce electric power; and are commonly called “heavy-duty”. The aim of this thesis is to evaluate the turbogas cycle of the TG16 machine (an Ethos’ machine) and to design a compact heat exchanger to turn the cycle into a regenerative one. Thanks to regeneration it’s possible to increase the plant efficiency by adopting inter-refrigerated re-compression, by exploiting the re-combustion technique and by taking advantage of regeneration: the mass flow rate out of the compressor is re-heated, before the inlet of the combustor using the exhausted gases at the outlet of the turbine, so combusted gases pass in the heat exchanger and then dumped into the environment.. Regeneration takes different advantages: Less energy is consumed thanks to the higher efficiency; Less emission of pollution in the atmosphere; Less risks of interruption of the system. The CW4145 software is used to verify the expected performances of an industrial single shaft gas turbine and to obtain the characteristic diagram both of the TG16 and of the TG16R. Then output data has been compared with the one previous reported to validate that the model fits with the reality. For the regenerated one the physical model doesn’t exist yet, so it’s used the Westinghouse Canada’s study of the 1976 as reference. Once that both the models are verified it’s possible to choose the right heat exchangers: using Aspen a compact heat exchanger of the plate type is choose. Plate Heat Exchangers (PHEs) are exchangers which uses metal plates to transfer heat between two fluids. The flux of the two fluids (hot and cold) are separated and exposed to a large surface area because they are spread out over the plates: heat’s transfer is facilitated and the speed of the temperature change is increased The thickness of the plate is very small (~ 1 mm) and they are usually spaced by rubber sealing gaskets, cemented into a section around the edge of the plates; so, the PHEs are usually quite thin: the plates are compressed together in a rigid frame to form an arrangement of parallel flow channels with alternating hot and cold fluids. Making the chamber thin ensures the majority of the volume of the liquid contacts the plate; moreover, the flow is turbulent thanks to troughs, and this maximize heat transfer. Even if the PHE is a small exchanger it isn’t enough for the dimensional constraints that EthosEnergy has: the solution with a regenerative efficiency of 87% needs Length = 20,33 m; Wideness = 2,154 m; Height = 2,603 m. While the dimensional constraints are: Length = 7,1 m; Wideness = 2,9 m; Height = 2,9 m. So, the PHE solution is not sufficient. The advice is to solve the problem of the regeneration of the TG16 is to consider a Plate-Fin Heat Exchangers.