Regenerator performance using freezing concentration for heat source tower heat pump system

• Published in: Applied thermal engineering 2023-09, Vol.232, p.121053, Article 121053
• Main Authors: Han, Chong, Yu, Muyang, Hou, Chongchong, Jiang, Huimin, Chen, Chuanbao, Yao, Yang, Ni, Long
• Format: Article
• Language: English
• Subjects: Freeze concentration; Freezing process; Heat source tower heat pump; Heat transfer; Refrigeration
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2023.121053

•Freeze concentration is applied for solution regeneration in heat pump system.•Regenerations at different OEEV (100%, 80%, 65% and 50%) were test.•Peak velocities appeared in the early stages of freezing process.•High thickness growth rates make it easier to retain solutes in ice.•Decreasing ice thickness uniformity values are beneficial to separation process. Freeze concentration has a good regeneration effect and is easy for latent heat utilization. The electronic expansion valve opening has a great impact on the icing process. Hence, to investigate variations in the freezing process and gain the optimum regeneration effect, a solution regenerator was tested under different system-side control strategies. The solution volume flow was 5 m3/h and the electronic expansion valve opening degree (OEEV) was from 100% to 50%. For ice-covering growth, ice in low opening degree spent a long time to cover the plate. The area of ice under 100% to 65% OEEV was 1.43 times that under 50% OEEV. Peak velocities from 100% to 50% OEEV all appeared in the early stage of icing development. Moreover, the low opening degree made the ice distribute unevenness. The percentage slope of 100% OEEV was 1.23% and that of 50% OEEV was 3.46%. In addition, decreasing ice thickness uniformity was beneficial to the separation process. The separation ratio from 100% to 50% OEEV was 49.51%, 51.67%, 57.88%, and 74.54%, respectively. Both the low average thickness growth rate and high separation ratio were beneficial to increase the regeneration concentration. The effective specific ice production rate was from 100% to 50% OEEV was 5.99 kg/kWh, 6.18 kg/kWh, 6.94 kg/kWh, and 6.88 kg/kWh, respectively. Results showed that 65% OEEV operation was optimum for the solution regenerator unit using freeze concentration.