SDCS Dehumidifier Volumetric Air Flow Effect
Figure 6.7 shows how changes in volumetric air flow effect dehumidifier performance. The volumetric air flow range investigated was 102-256 m3 h-1. Figure 6.7a shows that moisture removal rate increases as the volumetric air flow increases. Moisture removal rate increased from 0.1114 g s-1 at 102 m3 h-1 to a maximum of 0.2859 g s-1 at 256 m3 h-1. However, Fig. 6.7b shows that as the air volumetric air flow through the dehumidifier increases, the change in absolute humidity of the air across the dehumidifier decreases from 0.003511 kg/kg at 102 m3 h-1 to 0.003102 kg/kg at 256 m3 h-1 i.e. the outlet air absolute humidity is higher. This is because the mass of air passing through the dehumidifier is increasing and thus the capacity of the dehumidifier to reduce the air absolute humidity decreases.
Figure 6.7c shows that as the volumetric air flow increases, the latent (dehumidifier) effectiveness decreases from 42.48 % at 102 m3 h-1 to 34.98 % at 256 m3 h-1. Figure 6.7d shows that the dehumidifier cooling output increases as the volumetric air flow increases from 278.6 W at 102 m3 h-1 to 714.9 W at
Fig. 6.7 SDCS dehumidifier performance with inlet air volumetric flow
256 m3 h-1. The observed cooling output increases with the volumetric air flow, even though the outlet air absolute humidity is higher, because there is a greater mass of air being conditioned. Figure 6.7d also shows the COPei of the dehumidifier. The COPel increases with increasing volumetric air flow, from 3.03 at 102 m3 h-1 to 6.49 at 256 m3 h-1. However, the increase in COPel is not proportional to the increase in dehumidifier cooling output. This is because the electrical load increases with increasing air volumetric flow, from 92 W at 102 m3 h-1 to 110 W at 256 m3 h-1.
In the dehumidifier, the selection of a suitable volumetric air flow is dependent upon the desired outlet air condition and the volume of air required for the particular application. However, for maximising the cooling achieved, and thus maximising efficiency in a tri-generation system application, the volumetric air flow should be as large as possible.
