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Consider a carton of milk that is refrigerated at a temperature of
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Introduction to Heat Transfer
- Water is enclosed in the piston/cylinder system as shown in the figure. The initial temperature of the water is T1 = 140 °C. The mass of the enclosed water is m, = 12 kg. The piston has mass, m, = 500 kg and diameter, D, = 0.125 m. The water is heated until the specific volume is v, = 0.05 m/kg at which point the piston is fixed in position by a pin, i.e. piston can no longer move. The water is then further heated to a final temperature of T3 = 350°C. Assume that the atmospheric pressure is Po = 100.3 kPa and gravity is g = 9.81 m/s. a) What is the initial pressure of the water, P1, and specific volume v:? b) At state 2 what is the temperature, T2, and is the water a compressed liquid, saturated mixture or a superheated vapour? If the state is a saturated mixture, determine the quality. c) What is the final pressure of the water, P3? d) Draw a P - V (pressure - volume) diagram of the process. Label all state points, process lines, constant temperature line(s) and the pressure and…arrow_forwardQ = m xc x AT The iron block had a mass of 2 kg. Calculate the energy transferred by the heater to increase the temperature of the iron block by 5 °C. The specific heat capacity of iron is 450 J/ kg °C. SHOW YOUR WORKINGS OUTarrow_forwardSuppose that as a body cools, the temperature of the surrounding medium increases because it completely absorbs the heat being lost by the body. Let T(t) and Tm (t) be the temperatures of the body and the medium at time t, respectively. If the initial temperature of the body is T1 and the initial temperature of the medium is T2, then it can be shown in this case that Newton's law of cooling is dT/dt = k(T - Tm ), k 0 is a constant. (a) The foregoing DE is autonomous. Determine the limiting value of the temperature T(t) as t→ o What is the limiting value of Tm (t) as t→o? (b) Verify your answers in part (a) by actually solving the differential equation. (c) Discuss a physical interpretation of your answers in part (a).arrow_forward
- 2. A large sheet of glass 2” thick is initially at 300oF throughout. It is plunged into a stream of running water having a temperature of 60oF. How long will it take to cool the glass to an average temperature of 100oF. For glass k = 0.40BTU/ft-hroF, ρ = 155 lb/ft3 and Cp = 0.20 BTU/lboF.arrow_forwardThe diagram shows a schematic for a thermometer based on the expansion of some fluid. There is a spherical reservoir of the fluid, with radius R, which is connected via a tube to a vertical section, with a circular cross section, radius r. a. assuming r << R, show that the change in fluid level in the tube is given by: 4 BR³ AT AL = 3 p² Where AT is the change in temperature and is the volumetric expansion coefficient of the fluid b. what properties should the system have to be most sensitive?arrow_forwardThere is a piston-cylinder assembly with a mass of 50 kg and a surface area of 0.01 m2. The mass of air is 5 g. The initial volume of air is 5 liters. Atmospheric pressure is 100 kPa. As the specific internal energy of the air decreases by 260 kJ/kg the volume of air is also gradually decreasing to 0.002 m3. Ignore friction that is between the piston and the cylinder surface. Determine the heat transfer to the air. (kJ)arrow_forward
- Two vessels of different shape and sizes are connected by means of a pipe with a valve. Vessel A has a diameter of 4 ft and the length is 1.8 m at the given pressure gauge of 1476.4 in Hg and temperature of 82°F. Another vessel spherical in shape contains the same gas at 15,000 torr gauge and 18°C. The valve is opened and when the properties have been determined, it is found out that the gauge pressure is 35.7 kg;/cm² and the temperature is 21°C. If the barometric pressure is 755 mm Hg, find the following: 1. Volume of Vessel A in in3 2. Pressure at Vessel A in psia 3. Temperature at Vessel A in °R 4. Pressure at Vessel B in psia 5. Temperature at Vessel B in °R 6. Pressure of the gas when mixed in psia 7. Temperature of the gas when mixed in °R 8. Atmospheric pressure in psi Main Question: What is the diameter of the spherical tank in inches if the gas is carbon dioxide?arrow_forwardTwo vessels of different shape and sizes are connected by means of a pipe with a valve. Vessel A has a diameter of 4 ft and the length is 1.8 m at the given pressure gauge of 1476.4 in Hg and temperature of 82°F. Another vessel spherical in shape contains the same gas at 15,000 torr gauge and 18°C. The valve is opened and when the properties have been determined, it is found out that the gauge pressure is 35.7 kgf/cm2 and the temperature is 21°C. If the barometric pressure is 755 mm Hg. Question: What is the diameter of the spherical tank in inches if the gas is carbon dioxide?arrow_forwardTwo vessels of different shape and sizes are connected by means of a pipe with a valve. Vessel A has a diameter of 4 ft and the length is 1.8 m at the given pressure gauge of 1476.4 in Hg and temperature of 82°F. Another vessel spherical in shape contains the same gas at 15,000 torr gauge and 18°C. The valve is opened and when the properties have been determined, it is found out that the gauge pressure is 35.7 kgf/cm2 and the temperature is 21°C. If the barometric pressure is 755 mm Hg, find the following: Volume of Vessel A in in3 Pressure at Vessel A in psia Temperature at Vessel A in °R Pressure at Vessel B in psiaarrow_forward
- A vertical cylindrical shell storage tank of 4 m inside diameter and 6 m high is filled with three liquids having specific gravities of 3, 1 and 0.8. Each liquid has heights of 2 m inside the tank. A sharp edge orifice 120 mm diameter with C = 0.65 is located at the lowest point Determine the time to empty one half of its contents through orifice. Determine the time to empty the whole tank through the orifice.arrow_forwardA refrigerator has a coefficient of performance of 2.50, requires 150 W of electrical power to operate, and maintains a temperature of -4.00 °C within its interior compartment. How long would it take to cool a dozen 1.00 L of water in a plastic wrapper from 33.0 °C to -4.00 °C in this refrigerator? Any heat escaping the plastic should be ignored. Remember that 1.00 g/cm3 is the density of water.arrow_forwardQUESTION FIVE (a) At a certain location, wind is blowing steadily at 10 m/s. Determine the mechanical energy of air per unit mass and the power generation potential of a wind turbine with 60-m-diameter blades at that location. Take the air density to be 1.25 kg/m3. (b) Consider an alcohol and a mercury thermometer that read exactly 0°C at the ice point and 100°C at the steam point. The distance between the two points is divided into 100 equal parts in both thermometers. Do you think these thermometers will give exactly the same reading at a temperature of, say, 60°C? Explain.(c) Determine the work required to deflect a linear spring with a spring constant of 70 kN/m by 20 cm from its rest position.arrow_forward
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