Thermodynamic analysis of marine steam power plant pressure reduction valves

The paper presents a thermodynamic analysis of pressure reduction valves from a marine steam power plant that operates on conventional LNG carriers. The analysis refers to six condensate and superheated steam pressure reduction valves. Based on the exploitation data, the calculation involves the energy/exergy flow streams as well as the exergy efficiency and exergy destruction of each pressure reduction valve. The analysis also included the influence of changes in the ambient temperature on the efficiency and destruction of each valve. Total energy and exergy fluid flow streams through each valve showed the same trends. The superheated steam pressure reduction valves showed a lower average exergy destruction rate and higher average exergy efficiency compared with the water/condensate ones. Increase in the ambient temperature resulted in a continuous increase in the exergy destruction rate and a continuous decrease in exergy efficiency in all the observed pressure reduction valves. Pressure reduction valves of high exergy destruction rate and low exergy efficiency are notably influenced by changes in the ambient temperature.