Experimental investigations and multi-objective optimization of an air-source absorption heat pump for residential district heating

The traditional single-effect absorption heat pump is an effective district heating measure, while the low ambient temperature will degrade its performance significantly. To overcome this dilemma, a novel air-source absorption heat pump (ASAHP) for district heating (DH) is proposed in this paper. This system can operate at low ambient temperature and recover the waste heat of the flue gas with higher efficiency compared with the conventional gas-fired boilers. The falling film form is adopted in the generator and absorber, which reduces the system mass flow rate and electricity consumption. The thermodynamic performance of the system is analyzed by the lumped parameter model. An experimental rig is established to study the system performance and validate the mathematical model. Results show that the proposed system is an efficient way for DH, especially in cold regions. The heating capacity and the COP of the system are 38.32 kW and 1.39 at the evaporation temperature of 10 degrees C, respectively. The system can provide 36.21 kW heating capacity and 39.21 kW heating capacityfg (heating capacity of the system with flue gas recovery) with flue gas recovery to heat water from 25 degrees C to 39.1 degrees C with the COP of 1.21 and COPfg (COP of the system with flue gas recovery) with flue gas recovery of 1.36. The maximum ratio of COPfg with flue gas recovery to simulation value and the maximum ratio of heating capacityfg with flue gas recovery to simulation value are 92.91% and 92.23%, respectively. Additionally, to obtain the optimal operating condition, the TOPSIS decision-making method and NSGA-II technology is adopted in multi-objective optimization.

Automated summary

The novel air-source absorption heat pump (ASAHP) for district heating proposed in this paper can operate efficiently at low ambient temperatures and recover waste heat effectively. With the falling film form in the generator and absorber, the system reduces mass flow rate and electricity consumption, making it suitable for cold regions and providing efficient heating capacity. Multiple-objective optimization is conducted using the TOPSIS decision-making method and NSGA-II technology to achieve optimal operating conditions.