Paper No 520 – nnovative small capacity gas driven ammonia-water absorption heat pump prototype for space heating and domestic hot water production – 14th IEA Heat Pump Conference, Chicago, USA
Gas driven absorption heat pumps are a viable alternative for efficient space heating and domestic hot water production in residential and light commercial buildings with high temperature distribution systems. This work presents a secondgeneration ammonia-water absorption heat pump prototype, with patent-pending components developed by Politecnico di Milano. The innovative design of desorber and rectifier improves the heat and mass transfer in the generator whilst reducing its height and complexity. All the heat exchangers, except for the generator, are plate heat exchanger and a specifically designed oil driven diaphragm pump is used as solution pump. The overall weight of the prototype, excluding the continuous fin-type outdoor heat exchanger, is kept below 70 kg for a unit with nominal capacity of 10 kW. Variable restrictors for both solution and refrigerant branches are used to improve part load operation and the seasonal efficiency. Laboratory tests confirm high performance over a supply water temperature range between 25 °C and 70 °C and ambient temperatures between -14 °C and 22 °C. The experimental results highlight the importance of installing a variable restrictor on the solution branch to improve performances at partial load, optimizing the generator temperature. The newly designed prototype proved to perform smoothly and to maintain stable operation under the tested steady-state and transient conditions.