Abstract
Previous investigations of building free cooling using PCM were conducted at moderate/high temperature differences during PCM charging and discharging. This is not the case in fresh air free cooling where the PCM melting temperature should be low and close to the fresh air cooling temperature. The present study experimentally investigates fresh air free cooling with small temperature difference between air and the PCM melting temperature. The PCM plates’ behaviors in transient scenarios are examined during the charging and discharging process. The results showed that a complete solidification cannot be achieved during night in case of minimal temperatures difference. The effects of fresh air flow rate and outdoor temperatures on the discharging and charging processes, energy saving and the number of the PCM plates needed to satisfy the fresh air requirements are investigated. The results show the decrease of the discharge time and the increase of the number of the PCM plates with increasing the fresh air flow rate and the outdoor air temperature. The discharge time decreases by 17 and 25% by increasing the air temperature from 32 to 36 °C and increasing the air flow rate from 89 to 134 L/s, respectively. The energy saving decreases with increasing the time from the start of the discharging processes. The numbers of the needed PCM plates are studied, determined and correlated in terms of the air flow rates and the outdoor air temperature.
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