Optimal design and analysis of a cascade LiBr/H_2O absorption refrigeration/ transcritical CO_2 process for low-grade waste heat recovery

摘要

In this paper, a cascade LiBr/H(2)Oabsorption refrigeration/transcritical CO2 process is proposed to recover 90-150 degrees C low-grade waste heat. The proposed system consists of two subsystems: LiBr/H2O cycle and transcritical CO2 cycle. The low-grade waste heat is utilized by LiBr/H2O cycle and transcritical CO2 cycle in a cascade approach. Two optimization strategies, following efficiency of performance (FCP) and following net electricity generation (FNG), are proposed to design the cascade LiBr/H2O absorption refrigeration/transcritical CO2 process. A series processes on various refrigeration temperature (i.e., 2 degrees C, 3 degrees C, 4 degrees C, 5 degrees C, 7 degrees C, and 10 degrees C) are designed following the two optimization strategies. Key parameters in terms of refrigeration temperature, segment temperature, and high pressure are analyzed. In addition, the performance of the designed processed are compared based on the simulation results. Results show that the proposed system shows a better performance at the lower refrigeration temperature of the LiBr/H2O cycle. The high pressure under FCP is larger than that under FNG. The investment and profit of the optimal design under FCP are both more than that under FNG. This work provides a potential way to generate electricity using low-grade waste heat.