Nihon Kikai Gakkai ronbunshu (Jan 2022)
Development of a low-temperature driven absorption chiller with vapour exchange double-lift absorption cooling cycle (Experimental proof of 7 ℃ chilled water output driven by 60 ℃ hot water with a prototype)
Abstract
Conventional single-effect absorption chillers require an 80~90 ℃ heat source to supply 7~8 ℃ chilled water for air conditioning applications. However, it is difficult to recover lower temperature heat sources such as 60 ℃ hot water with single-effect chillers. To improve the low-temperature waste heat recovery, we develop a low-temperature-driven absorption chiller that adopts a vapour exchange (VX) double-lift absorption cooling cycle. We developed a proof-of-concept prototype for this cycle and conducted its performance tests in this study. As a result, it delivered chilled water at 7 ℃ when driven by approximately 60 ℃ heat source hot water inlet and 30 ℃ cooling water. We also confirmed the reliability of this result based on the heat balance of the experimental data, according to the AHRI standard. However, the cooling heat quantity (QEw) was approximately 12% lower than the calculation. So, this report also discusses a potential cause of the performance decrease under the assumption that there was internal heat loss in the prototype, considering its external heat balance was less than 2.0%. We compared QEw with the heat discharge from the absorber (QAw) and the condenser (QCw), and found the internal heat loss from the absorber to the evaporator. Its heat transfer mechanism was confirmed by possibility estimating calculation. Then we assimilated this internal heat loss as a part of the cycle simulation program and computed the chilled water temperature characteristics of the prototype. The simulation results well agreed with the experimental results by considering the internal heat loss. This result proved the above assumption of the internal heat loss and thus the reliability of the experimental results.
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