Assignment 1 Solutions
.pdf
School
McGill University**We aren't endorsed by this school
Course
CIVE 290
Subject
Civil Engineering
Date
Dec 17, 2024
Pages
4
Uploaded by MajorInternet15662
1 Department of Civil Engineering & Applied Mechanics McGill University, Montreal, Quebec Canada CIVE 290 THERMODYNAMICS & HEAT TRANSFER Assignment #1 SOLUTIONS 1.A mercury manometer (ρ= 13,600 kg/m3) is connected to an air duct to measure the pressure inside. The difference in the manometer levels is 15 mm, and the atmospheric pressure is 100 kPa. (a) judging from the figure, determine if the pressure in the duct is above or below the atmospheric pressure, and (b) determine the absolution pressure of the duct. 2.A water pipe is connected to a double-U manometer as shown in the figure at a location where the local atmospheric pressure is 14.2 psia. Determine the absolute pressure at the centre of the pipe. The density of water is ρw = 62.4 lbm/ft3, and the specific gravities of mercury and oil are 13.6 and 0.80, respectively.
2 A water pipe is connected to a double-U manometer whose free arm is open to the atmosphere. The absolute pressure at the center of the pipe is to be determined. Assumptions1 All the liquids are incompressible. 2 The solubility of the liquids in each other is negligible. Properties The specific gravities of mercury and oil are given to be 13.6 and 0.80, respectively. We take the density of water to be ρw = 62.4 lbm/ft3. AnalysisStarting with the pressure at the center of the water pipe, and moving along the tube by adding (as we go down) or subtracting (as we go up) the ghρterms until we reach the free surface of oil where the oil tube is exposed to the atmosphere, and setting the result equal to Patmgives atmPghghghghP=−−+−2oil,oilHgHg1oil,oilwaterwaterpipewater ρρρρSolving for Pwater pipe, )(oil,2oilHgHg1oil,oilwaterwaterpipewater hSGhSGhSGhgPPatm++−+=ρSubstituting, psia3.22in144ft1ft/slbm32.2lbf1ft)](40/128.0ft)(15/126.13ft)(60/1280.0ft))[(35/12ft/s2.32()lbm/ft(62.4psia14.222223water pipe=⋅×++−+=PTherefore, the absolute pressure in the water pipe is 22.3 psia. Discussion Note that jumping horizontally from one tube to the next and realizing that pressure remains the same in the same fluid simplifies the analysis greatly. 3.Consider a U-tube whose arms are open to the atmosphere. Now equal volumes of water and light oil (ρ = 49.3 lbm/ft3) are poured from different arms. A person blows from the oil side of the U-tube until the contact surface of the two fluids moves to the bottom of the U-tube, and thus the liquid levels in the two arms are the same. If the fluid height in each arm is 30 in, determine the gage pressure the person exerts on the oil by blowing.
3 Equal volumes of water and oil are poured into a U-tube from different arms, and the oil side is pressurized until the contact surface of the two fluids moves to the bottom and the liquid levels in both arms become the same. The excess pressure applied on the oil side is to be determined 4.A cylinder contains a layer of water covered by a layer of hydraulic fluid, as shown below. The bottom of the cylinder is connected to an inclined tube that is partially filled with water. The densities of the hydraulic fluid and water are 52.75 and 62.2 lbm/ft3, respectively. Determine the gage pressure at the bottom of the tank in psig, mm Hg, and atm. What is the distance d ? What is the advantage in using inclined manometers compared to traditional U-tube manometers?
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