Example Exercise Section B Topic 1 Introduction Example

Example / Exercise Section B Topic 1 - Introduction

Example B 1. 3. 1 Exercise: Example 9 -2 (pg 385) “Min pressure to avoid cavitation” In a water distribution system, the temperature of water is observed to be as high as 30’C. Determine the minimum pressure allowed in the system to avoid cavitations. *Solution: Pmin > Psat 0 r Pvapor. Ans : 4. 25 k. Pa • Refer Table A-4 based on the table, the vapor pressure of water at 30’C is 4. 25 k. Pa.

Example B 1. 3. 2 Exercise: Example 9 -3 (pg 387) “Speed of sound, c and Mach Number, Ma of air entering a diffuser” Air enters a diffuser with velocity of 200 m/s. Determine (a) the speed of sound and (b) the Mach number at the diffuser inlet when the air temperature is 30°C. Ans : (a) 349 m/s (b) 0. 573 • Refer Table A-2 a as temp 30°C. For an ideal gas ; For any fluid ; Ma = 1 Ma < 1 Ma >> 1 Sonic flow Subsonic flow Supersonic flow Hypersonic flow

Exercise: Example 9 -5 (pg 395) “The capillary rise of water in a Tube” Example B 1. 3. 3 • Refer Table 9 -3 A 0. 6 mm diameter glass tube is inserted into water at 20°C in a cup. Determine the capillary rise of water in the tube (Figure). Ans : 5. 0 cm R = radius (constant) g = standard gravitational acceleration ( 9. 81 m/s 2) Water or organic liquids ; Φ =~ 0° 1 kg m/s 2 = 1 N ρ = fluid density

1. 3. 1 Density Mass Density, ρ Specific Weight, ω Relative Density, σ The mass of substance per unit volume. The weight per unit volume. (Known as specific gravity) or The force exerted by gravity, g, upon a unit volume of the substance. The ratio of mass density of a substance to some standard mass density. This standard mass density is the max mass density for water (4°c) at atmospher pressure. Kilograms per cubic metre, kg / m 3 or kgm-3 Newton’s per cubic metre, N / m 3 or N m-3 -NANone, since a ratio is a pure number. Dimension ML-3 ML-2 T -2 1 Typical values Water = 1000, Mercury = 13, 546, Air = 1. 23, Water =9814, Mercury = Paraffin Oil = 800. 132, 943, Air =12. 07, (at pressure =1. 013 x 10 -5 Paraffin Oil =7, 851 Nm-2 and Temperature = 288. 15 K. ) Definition Units Water = 1, Mercury = 13. 5, Paraffin Oil =0. 8.

Example B 1. 3. 4 • Exercise: Example 9 -4 (pg 391) “Determining the Viscosity of a Fluid” The viscosity of a fluid is to be measured by a viscometer constructed of two 40 cm long concentric cylinders (Figure). The outer diameter of the inner cylinder is 12 cm, and the gap between the two cylinders is 0. 15 cm. The inner cylinder is rotated at 300 rpm, and the torque is measured to be 1. 8 Nm. Determine the viscosity of the fluid. Ans : 0. 158 N. s/m 2

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