The effect of using tubes filled with phase change materials in the air conditioning system of a residential building

This paper analyses an air conditioning system (ACS) of a building using phase change materials (PCMs) numerically. PCMs of CaCl2.6H2O are placed inside the tubes in the ACS. The tubes are linearly arranged in 10 rows, with 17 tubes in each row. The freezing time of PCM is estimated by changing the diameter of the tubes in the range of 1–3 cm, the inlet temperature (Tinlet) of 285–295 K, and Re of 100–1000. The main focus is on the PCM discharging process at night on hot days of the year to damp additional heat entering the building. Therefore, the natural ACS's contribution to the total energy required for cooling a residential unit in cold and dry weather is studied. ANSYS-FLUENT 19 software is employed for the simulations and Carrier software is used to estimate the heat load of the residential unit. The results showed that an increment in the diameter of PCM tubes enhances the freezing time of PCM so that increasing the diameter of the tube from 1 to 3 cm more than doubles the freezing time. In addition, it was found that increasing the Re reduces the freezing time, especially at low Re. The use of a thicker tube enhances the energy supply from the ACS. In the hottest month of the year, it is possible to provide up to 34% of the required energy of cooling from this system by using a 3 cm tube at Re of 1000.