This is a continuation of Problem 21. 12. Typical heat transfer coefficients given in Table 11. 11 are used to predict the ratio of heat transfer resistances between boiling water and light oil. This ratio is estimated to be approximately 1:2. Estimate the individual resistance and heat transfer coefficient for both the oil and the boiling water.

Table 11.11

Data from problem 21.12

Operating data taken from the plant shortly following the cleaning of the reboiler tubes show that
\[
T_{\text {in }}=325^{\circ} \mathrm{C}, T_{\text {out }}=293^{\circ} \mathrm{C}, \dot{m}_{s}=1650 \mathrm{~kg} / \mathrm{h}, T_{s}=253^{\circ} \mathrm{C}
\]

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1. Fans are used to raise the pressure about 3% (12 in (30 cm) water), blowers to raise less than 2.75 barg (40 psig), and compressors to higher pressures, although the blower range is commonly included in the compressor range. 2. Theoretical reversible adiabatic power = mzRT[({P/P}" - 1)]/a where T, is inlet temperature, R= gas constant, 2, = compressibility, m = molar flow rate, a = (k-1)/k and k = C/C Values of R: 8.314 J/mol K-1.987 Btu/lbmol R = 0.7302 atm ft/lbmol R 3. Outlet temperature for reversible adiabatic process T, = T, (P-/P)". 4. Exit temperatures should not exceed 167-204C (350-400F); for diatomic gases (C/C, 1.4). This corresponds to a compression ratio of about 4. 5. Compression ratio should be about the same in each stage of a multistage unit, ratio (P/P), with stages. 6. Efficiencies of reciprocating compressors: 65% at compression ratios of 1.5, 75% at 2.0, and 80-85% at 3-6. 7. Efficiencies of large centrifugal compressors, 2.83-47.2 m/s (6000-100,000 acfm) at suction, are 76-78%. 8. For vacuum pumps use the following: Reciprocating piston type Rotary piston type Two-lobe rotary type Steam jet ejectors Down to 1 Torr Down to 0.001 Torr Down to 0.0001 Torr 1-stage down to 100 Torr 3-stage down to 1 Torr 5-stage down to 0.05 Torr 9. A three-stage ejector needs 100 kg steam/kg air to maintain a pressure of 1 Torr. 10. In-leakage of air to evacuated equipment depends on the absolute pressure, Torr, and the volume of the equipment, V in m (ft) according to W kV kg/h (lb/hr) with k = 0.98 (0.2) when P > 90 Torr, k=0.39 (0.08) between 3 and 20 Torr, and k = 0.12 (0.025) at less than 1 Torr.