Design considerations for high-temperature heat pump centrifugal compressors

Authors

Ahti Jaatinen-Värri  - LUT University, Finland
Jonna Tiainen - LUT University, Finland
Juha Honkatukia - LUT University, Finland
Antti Uusitalo - LUT University, Finland
Teemu Turunen-Saaresti - LUT University, Finland

Abstract

Ever increasing demand for more energy efficient and less carbon-intensive energy systems has brought heat pumps into the limelight. Low-temperature heat pumps are common practice e.g. in space and domestic water heating. However, in terms of high-temperature heat pumps with the heat pump temperature lifts of up to 100°C, more research is needed to fulfil their potential in process industry. Centrifugal compressors are generally considered as the best option for high-power and high-temperature heat pumps in industrial scale. When the heat pump temperature lift increase from the commonly used values, the overall cycle pressure ratio increases resulting in higher heat pump compressor pressure ratios. In high-temperature heat pumps, the compressor pressure ratios are higher than what commonly are used for centrifugal compressor, even if the two-stage heat pump compressors are used. In this study, the effect of high-temperature heat pump process requirements for the compressor design work is considered. The effect of evaporating temperature and heat pump temperature lift are studied in terms of centrifugal compressor design values. A two-stage high temperature heat pump process is used as an example process, and the heat pump process is modelled with varying evaporating temperatures and heat pump temperature lifts and different working fluids to study how it affects the compressor design values.