Energy grade splitting of hot water via a double effect absorption heat transformer

• Published in: Energy conversion and management Vol. 230; p. 113821
• Main Authors: Xu, Z.Y., Gao, J.T., Mao, H.C., Liu, D.S., Wang, R.Z.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 15.02.2021; Elsevier Science Ltd
• Subjects: Absorption; Absorption heat transformer; Energy; Energy levels; Experiment; Heat; Heat recovery; Heat recovery systems; Heat transformers; High temperature; Hot water; Modeling; Modelling; Performance enhancement; Quality; Splitting; Temperature; Waste heat; Waste heat recovery; Water absorption; Absorption heat transformer; High temperature; Waste heat recovery; Modeling; Experiment
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2020.113821

•Energy grade splitting strategy is proposed for efficient local waste heat recovery.•Double effect LiBr-water absorption heat transformer is adopted in the strategy.•Experimental prototype and modeling framework were built to evaluate the strategy.•COP of 0.618 under splitting condition of 149.7 → 128.1 °C and 151.0 → 158.2 °C. Energy level mismatch between waste heat and energy users poses huge barrier for local waste heat recovery. To tackle this challenge, an energy grade splitting strategy of hot water via absorption heat transformer is proposed. In this strategy, the hot water is separated into two branches. An absorption heat transformer extracts waste heat from the colder branch, and delivers heat output to increase the temperature of hotter branch. This process could deliver high temperature output and decrease the temperature of waste heat simultaneously, which meets the local waste heat recovery demand. Both experimental and modeling researches are carried out to investigate this strategy. Firstly, double effect LiBr-water absorption heat transformer is adopted for performance enhancement, and experimental investigation was carried out. Testing results showed that 391.4 kW heat output and COP of 0.618 were achieved, under colder branch temperature of 149.7 → 128.1 °C and hotter branch temperature of 151.0 → 128.1 °C. Secondly, modeling framework was built and used to evaluate the energy grade splitting performance under different conditions. Results showed that the proposed energy grade splitting strategy is effective under waste heat source temperatures of 130.0–160.0 °C, temperature lift of 5.0–20.0 °C, mass split ratio of 0.10–1.60 and temperature split ratio of 2.00–20.00. Such an effective and flexible strategy could further be promoted to other scenarios with different heat conversion technologies, and contribute to the wide application of local waste heat recovery.