A water-ammonia heat transformer to upgrade low-temperature waste heat

A prototype water-ammonia absorption heat transformer has been built and thoroughly tested. Compared to water-salts mixtures, water-ammonia allows operating the machine in a lower temperature range, fostering recover of low-grade heat. Driving temperatures between 60 °C and 64 °C were tested, with condenser temperatures of 8-16 °C. The unit proved able to operate in a stable, reliable and repeatable way in this working range, achieving gross temperature lifts up to 25 °C and thermal COPs in the range 0.400-0.475. Useful effect up to 4.5 kW was achieved, with electric consumption always below 100 W.