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MAE 320 HW 1 Assignment Due on Friday, January 23, 2015

(1). Multiple choice (25 points) (1a). (5p) If the units of a quantity x are )/( skgkJ and the units of t are s, what are the units of q in the equation below?

(A) kJ (B) kJ/kg (C) )/( skgkJ (D) kW (1b). (5p) In order for a system to be in thermal equilibrium, which of the following properties must be the same throughout the system (A) mass (B) pressure (C) temperature (D) density (1c). (5p) A specific property is also (A) an extensive property (B) the product of two extensive properties (C) an amount of mass dependent property (D) an intensive property (1d). (5p) The atmospheric pressures at the top and the bottom of a building are read by a barometer to be 0.96 and 0.98 bar. If the density of air is 1.0 kg/m3, the height of the building is (A) 17 m (B) 252 m (C) 170 m (D) 204 m (1e). (5p) For a control volume (or an open) system, (A) The volume of an open system must be constant with prolonging of time (B) Both mass and energy can across the boundary of a control volume. (C) The amount of mass is fixed, but energy can transfer in or out of the system. (D) The boundary of system is fixed (cannot be moved). (1f). (5p) During a heating process, the temperature of an object rises by 20C. This temperature rise is equivalent to a temperature rise of (A) 20F (B) 52F (C) 36 K (D) 36 R (E) 293 K

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2. Simple calculation question (10 points). 2a. Please demonstrate the unit of VP is Joule, where units of P and V is Pa and m3, respectively. 2b. The mass of air in a room 3520 m is 350 kg. Determine the density, specific volume, and specific weight of the air 3. As shown in the figure, a cylinder of compacted scrap metal with height of L=2 m and diameter of 0.5 m is suspended from a spring scale at a location where the acceleration of gravity is 9.78 m/s2. If the scrap metal density, in kg/m3, varies with the position z according to the law =7800 360(z/L)2, please determine the reading of the scale, in N. (10 points) 4. Determine the total force, in kN, produced by pressure acting on 1 m-diameter horizontal hatch of a submarine submerged 600 m below the sea surface. Assume the atmospheric pressure on the sea surface being 100 kPa, the ambient temperature being 300 K, and the density of sea water being 1 g/cm3. (10 points) 5. As shown in the figure on the right, the local atmosphere pressure is 758 mm Hg. The specific gravity (SG) of Fluid A is 0.10194. The specific weight of fluid B is 8 kN/m3. Calculate the absolute pressure, P1, of the manometer in kPa. (10 points) 6. Pressure transducers are used to measure the pressure by generating the analogue signals, usually in the range of 4 mA to 20 mA, or 0 V-dc to 10 V-dc, in response to the applied pressure. The system is schematically shown in the figure below. A rigid container is filled with the pressurized air; and the pressure is measured by the manometer attached. A valve is used to regulate the pressure in the container. Both the pressure and the electrical signals are measured simultaneously for various settings. The measurement results are tabulated. For the given sets of measurement, the calibration curve is expressed in the form of a liner equation P=aI+b, where a and b are the constants. (6a) Calculate a and b in the equation showing the gage pressure (in kPa) as a function of the electrical current. Provide the equation and a graphical representation of the curve fit; determine the gage pressure that corresponds to the current of 10 mA.

SG = 0.10194

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(6b) Go to www.omega.com and find two different pressure transducers that could be used for this experiment. Provide the model number, accuracy, and cost for the models selected on the homework solution sheet. Do NOT submit the Omega web page or catalog pages. (6c) When would a transducer be used in place of a manometer? (6d) When would a manometer be used in place of a transducer? (6e) Find two different transducers that are commonly used to measure temperature. Provide the model number, accuracy, and cost for the models selected on the homework solution sheet. Do NOT submit the Omega web page or catalog pages. (6f) Comment on the cost of these transducers relative to the accuracy level. (15 points)

7. Write an essay on different temperature measurement devices. Explain the operational principle of each type of device, its advantages and disadvantages, its costs and its range of applicability. Go to www.omega.com or other venders websites and find the device with the lowest price, which is suitable for use in the following cases: (i) monitoring the surface of car engine at different locations. (ii) checking the temperature of the flame in a combustor. (iii) measuring the temperature inside an industrial furnace with the maximum operating temperature of 1500 oC. List the costs, the accuracy and the temperature range of the devices that you have chosen for each case. (15 points) 8. Explain why international standards are important. How were these standards developed? What importance do units play in solving a problem involving international team or designing a product to be globally sold? (5 points)