Egypt-Japan University of Science and Technology (E-JUST) ERE 221 Thermofluids Due time March 23, 2023 Sheet 1 Fluid Density 1. The density of a substance is 800 kg/m3. What is its specific gravity, specific weight and specific volume? Ideal Gas Law 2. Determine the mass of air in a 2 m3 tank if the air is at room temperature, 20 °C, and the absolute pressure within the tank is 200 kPa (abs). 3. A compressed air tank contains 5 kg of air at a temperature of 80 °C. A gage on the tank reads 300 kPa. Determine the volume of the tank. Fluid Compressibility 4. It was wanted to test a pipe 1 km long and 20 cm diameter. Water (Ev=2×109 Pa) is pumped to fill the pipe at 1 bar. Then an extra amount of water is added to reach a test pressure of 20 bar. Find the amount of the extra water. Surface Tension 5. Estimate the excess pressure inside a raindrop having a diameter of 3 mm. Assume water surface tension to be 7.34 x 10-2 N/m. 6. An open, clean glass tube, having a diameter of 3 mm, is inserted vertically into a dish of mercury at how far will the column of mercury in the tube, be depressed? Assume mercury surface tension to be 0.466 N/m, Ɵ=130°. 7. To measure the water depth in a large open tank with opaque walls, an open vertical glass tube is attached to the side of the tank. The height of the water column in the tube is then used as a measure of the depth of water in the tank. For a true waterdepth in the tank of 1 m, what is the smallest tube diameter allowed to have a less than 1% error? Assume Ɵ=0°. Consider water surface tension as 7.34 x 10 -2N/m. Viscosity 8. Three large plates are separated by thin layers of ethylene glycol (μeg= 0.0199 Page 1 of 2 Egypt-Japan University of Science and Technology (E-JUST) ERE 221 Thermofluids Due time March 23, 2023 N.s/m2) and water (μw = 0.001 N.s/m2). The top plate moves to the right at 2 m/s. At what speed and in what direction must the bottom plate be moved to hold the center plate stationary? 9. A cylinder of 0.12-m radius rotates concentrically inside of a fixed cylinder of 0.13m radius. Both cylinders are 0.3-m long. Determine the viscosity of the liquid which fills the space between the cylinders if a torque of 0.88 N.m is required to maintain an angular velocity, ω, of 2π rad/s. For the small space between cylinders, the velocity gradient may be assumed constant. 10.Determine the constant speed with which the disk shown in Figure will move down on the inclined surface if the 0.02-cm gap between the disk and the surface contains oil having viscosity of 0.5 poise. The disk is 50 cm diameter and weighs 120 N. Page 2 of 2
