Technological Design Of The Absorption Heat Pump Operated In Bimodal Modes

In the present absorption heat pump heating system, the single effect absorption heat pump was widely used while the double effect absorption heat pump was just used in some low temperature situations. In order to increase the utilization ratio of the resource and equipments, the absorption heat pump operated in bimodal modes was proposed. When the temperature required is lower, the bimodal unit will work in the double effect mode, and when the temperature required is higher, the bimodal unit will work in the single effect mode. Technological flow and switch of the bimodal unit were designed for different modes. And the evaluation of the bimodal unit about the energy efficiency and economic benefit were also carried out. The LiBr/H2O absorption cycles of single effect and double effect absorption heat pump were analyzed in detail. The optimization relationships between the specific heating load (SHL) and coefficient of performance (COP) were reasoned out using the Finite-time Thermodynamics method according to the characteristic of investment and capacity. And the optimal operating conditions of the bimodal unit were put forward. Based on the simulation and optimization, the thermal calculation and heat transfer calculation were accomplished, and then the structure of the heat exchangers in the bimodal unit was designed. The software of the bimodal unit was developed. The process simulation, thermodynamic optimization and structure design were realized in the software. Finally, economic and technical analysis of the bimodal unit was made using some technical economic indicators. Compared with the traditional single effect absorption heat pump, the primary energy ratio of the bimodal unit increased by 25% and its COP can reach 2.0 or more. Although the primary cost of the bimodal unit is much higher than the traditional single effect unit, the dynamic annual cost of the bimodal unit is smaller, and the payback period is shorter. In conclusion, the results obtained in the present paper are of general significance and can provide some theoretical bases for the optical design and operation of absorption system.