TAILIEUCHUNG - Two Phase Flow Phase Change and Numerical Modeling Part 20

Tham khảo tài liệu 'two phase flow phase change and numerical modeling part 20', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 560 Two Phase Flow Phase Change and Numerical Modeling Fig. 20. Schematic diagrams of the HVAC systems used in the simulations The results are shown in Figure 21 for 100 and 400 kg of PCM. In the left-hand figure the PCM mixture was cooled to air temperature 12 c as soon as the charging operation started. During the discharging operation the stored heat was not large enough to maintain the room temperature. Consequently the room temperature was raised to 35 c. The righthand figure shows the results for 400 kg. The temperature during charging and discharging operations decreased gradually due to latent heat. The stored heat had sufficient capacity to maintain the room temperature near the set point. Fig. 21. Comparison of temperature fluctuation using 100 kg or 400 kg of PCM Room tempi 13 00 28 c 26PC 16 00 Fig. 22. Index used to evaluate the investigated effect Thermal Energy storage Tanks Using Phase Change Material PCM in HVAC Systems 561 Fig. 23. Relationship among the index the materials and the quantities Discussion The purpose of tills system was to control the temperature increase while the refrigeration machines were stopped. The evaluation of the system focused on the degree to which the temperature fluctuated. Assuming that 28 c is the allowed indoor temperature the area A shown in Figure 22 which is the difference between the room temperature and 28 c was used as an index of temperature deviation. This index increases as the temperature in the room increases. Figure 23 shows the relationship between the index the quantity of PCM and the PCM mixture. The temperature deviation decreased as the quantity of PCM mixture increased. The index or the temperature deviation was very small for 400 kg of PCM which was equivalent to kg m2 of PCM. The differences among the various materials were not significant. The index was larger for materials with higher melting temperatures MT23 MT21 . Because of its lower melting temperature the most effective material .

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