Tham khảo tài liệu 'handbook of lubrication episode 1 part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Volume II 297 FIGURE 4. Generalized reduced viscosity of gases. From Hougen O. A. Watson K. M. and Ragatz R. A. . Charts 2nd ed. John Wiley Sons New York 1960. With permission. Table 4 COMPARISON OF ESTIMATED NITROGEN VISCOSITIES AT 1 BAR T Tr Hr from Figure 4 X based on X at 300 K based on pi r X 10- fl actual Reference 1 200 300 400 500 If no viscosities are known the critical viscosity may be estimated from the values of Pcr Tcr and molecular weight M as follows Mrr X io-7M0-5P r6 S7Ti -167 6 VI VI VI z Table 4 illustrates the application of the two methods to the calculation of the viscosity of nitrogen. For each temperature Tr is calculated from Tcr K. Next are listed the Copyright 1983 CRC Press LLC 298 CRC Handbook of Lubrication values of Lir estimated from Figure 4 from the low density limit curve. Assuming we know the viscosity is X 10 6Pirsec at 300 K where Lir is estimated to be the value of Lcr is the same and the viscosities at the other temperatures are directly calculated as shown. If no viscosities are known Equation 6 is used Lcr X 10 7 0-5 0-667 - -167 X 10-6 Values for the other temperatures are calculated directly from the estimated values of Lr. The final column shows the actual viscosities indicating a reasonable check. For convenience the following are conversions to the SI system 1 reyn X 10-10 Pa sec and 1 P Pa sec. Specific Volume The specific volumes listed in Table 1 indicate the degree of perfection of a gas. At K and I bar pressure 1 g-mol of a perfect gas occupies a volume of . Adjusting this to 300 K gives . If the specific volumes in Table 1 are multiplied by the molecular weight for each gas the result is liters per gram mole g-mol and also cubic meters per kilogram-mole m3 kg-mol . Values for air nitrogen and oxygen are . Freon 21 Freon 11 and .
