Technical comparison between two steam generation connections using high temperature heat pumps

Abstract

The purpose of this thesis was to compare two steam generation connections in terms of steam generation capacity per unit and overall system performance (COP). In the first connection, a closed-cycle compression heat pump was connected to a separate flash vessel, where steam was generated at 85 °C and then further compressed to three different pressure levels: 1,43, 3,62 and 6,18 bar(a), utilizing mechanical vapour recompression (MVR) technology. In the second connection, steam was generated directly in a plate & shell heat exchanger operating as the condenser of the heat pump at 110 °C. Similarly, the steam was further compressed by radial MVR compressors to 3,62 and 6,18 bar(a). Three different closed-cycle compression heat pump configurations were used, and three refrigerants were selected for the comparison: R1234ze(E), R1233zd(E), and R600a (isobutane). The results demonstrate that generating steam in a flash tank operating under vacuum conditions can have a significant advantage over the direct steam generation connection, achieving a 0,20 to 0,75 unit higher COP, depending on the evaporation temperature, refrigerant, and heat pump configuration.The comparison was carried out as a theoretical calculation. However, the heat pump compressor performance values were obtained from two compressor manufacturers’ software tools, and the MVR performance values were provided by a technology supplier. In addition to the technical comparison, this thesis also presents information on high-temperature heat pumps, potential refrigerants, and the market potential of the technology in question.