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Nước cất là nước tinh khiết, nguyên chất, được điều chế bằng cách chưng cất và thường được sử dụng trong y tế như pha chế thuốc tiêm, thuốc uống, biệt dược, rửa dụng cụ y tế, rửa vết thương. | New Trend in the Development of ME-TVC Desalination System 199 Fig. 5. The effect of motive steam on the distillate production from the effects. Top brine temperature oC Fig. 6. The effect of top brine temperature on the distillate production and gain output ratio. because more amount of sensible heating is required to increase the feed seawater temperature to higher boiling temperatures. Additionally the latent heat of the vapor decreases at higher temperatures. The direct dependence of the top brine temperature on the specific heat consumption and the specific exergy consumption are shown in Fig. 7. Both of them increase linearly as the top brine temperature increases because higher top brine temperature leads to higher vapor pressure and consequently larger amount of motive steam is needed to compress the vapor at higher pressures. Fig.8. demonstrates the variations of the specific heat transfer area as a function of temperature difference per effect at different top brine temperatures. The increase in the specific heat transfer area is more pronounced at lower temperature difference per effect than at lower top brine temperatures. So a high overall heat transfer coefficient is needed to give a small temperature difference at reasonable heat transfer area. 200 Desalination Trends and Technologies Top brine temperature C Fig. 7. The effect of top brine temperature on the specific heat consumption and specific exergy consumption. Fig. 8. The effect of temperature drop per effect on the specific heat transfer area. The exergy analysis is also used to identify the impact of the top brine temperature on the specific exergy destruction for different ME-TVC units as shown in Fig.9. It shows that as the top brine temperature increases the specific exergy destruction of ALBA Umm Al-Nar and Al-Jubail plants are increased. It shows also that Al-jubail unit has the lowest values compared to other units. Fig. 10 gives detail values of exergy destruction in different .
