Performance analysis of an evaporation process of plate heat exchangers installed in a Kalina power plant

Highlights: • Evaporation process of NH3-H2O mixture with plate heat exchangers of existing Kalina cycle is analyzed. • Three main key parameters are introduced: pressure drops, vapor fraction and heat transmission capacity. • Trend of parameters over a period from 2012 until 2017 are analyzed. • Operation data points are published to the scientific community. In geothermal power generation, ammonia-water (NH₃H₂O) mixtures are considered as working fluids in order to improve efficiency from low enthalpy heat sources. During the evaporation process, the NH₃H₂O working pair as zeotropic working fluid has the advantage to evaporate not isothermal temperature but over a temperature glide to adapt better to the heat source temperature profile. By today, there is a lack of performance data from operational generation units available in literature that can be used for scientific works based on computational calculations to compare with. In this paper the data logs from the evaporation process of the geothermal power plant are analyzed in order to review the evaporator's performance. Data had been gathered for a period of 5 years and three key performance parameters were defined: pressure drop, vapor fraction and heat transmission capacity. The main parameters that influence the performance are the temperatures, pressures and flow rates. It turned out, that the NH₃ mass fraction plays only a minor role within the evaporation process.