COOLING | THERMAL STORAGE (a) Charging phase inlet velocity 2.86 m/s Figure 4. CFD simulation and measurement temperatures for PCM heat exchanger charging and discharging processes (b) Discharging phase inlet velocity 2.86 m/s Time (seconds) (b) Discharging PCM temperatures at varied velocities PCM temperature (kelvin) (a) Charging PCM temperatures at varied velocities PCM temperature (kelvin) Figure 5: PCM temperature simulated in PCM heat exchanger Time (seconds) Time (seconds) Time (seconds) Experimental investigations were carried out at design operating conditions of night-time PCM charging and daytime PCM discharging processes. A 3D CFD model for the PCM heat exchanger was developed and validated by comparing it with the respective measurement results. The validated CFD model evaluates and compares the PCM heat exchanger performance at different design and operating conditions. Based on the simulation results, for either the PCM charging or discharging process, the PCM undergoes sensible heat, phase change, and sensible heat stages. It verifies that significant cold energy can be stored or released in the PCM with a two-phase state. The phase change periods, however, are affected greatly by some important operating parameters, such as external heat transfer fluid (airflow) flow velocity. When the airflow velocity increases from 1.3m/s to 6m/s, the phase change periods decrease by 25% and 23% for PCM charging and discharging processes. CJ References: 1 V Butala and U Stritih, Experimental investigation of PCM cold storage, Energy and Buildings, vol 41, no 3, pp354359, 2009. 2 R Baetens, B P Jelle and A Gustavsen, Phase change materials for building applications: a state-of-the-art review, Energy and Buildings, vol 42, pp1361-1368, 2010. 3 G Fang, S Wu and X Liu, Experimental study on cool storage air conditioning system with spherical capsules packed bed, Energy and Buildings, vol 42, pp1056-1062, 2011. The paper was presented at the 2023 Technical Symposium. The 2024 event is on 11-12 April ww.cibse.org/symposium Professor YUNTING GE is director of the Centre for Civil and Building Services Engineering at LSBU. Co-authors were ARTON MEROVICI, research associate, and DR XINYU ZHANG, postdoctoral research associate, both at LSBU www.jung-pumps.co.uk 0118 9821 555 Every time you specify a DrainMajor Tank, we will donate 5 to the Rainforest Trust. Tank Construction Polyethylene DrainMajor Wastewater Pumping System Email davidj@pumptechnology.co.uk so that we can donate on your behalf Specify pumping systems with recyclable tanks to support the environment! 38 February 2024 www.cibsejournal.com CIBSE Feb 24 pp36-38 PCM cooling Edit.indd 38 26/01/2024 15:39