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An electrical power transformer of diameter
Assuming the maximum allowable temperature rise of the coolant to be
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Chapter 8 Solutions
Fundamentals of Heat and Mass Transfer
- Item 1 1 of 5 II Review Part A A flow-through electric water heater has a 22 kW electric heater inside an insulated 2.0-cm-diameter pipe so that water flowing through the pipe will have good thermal contact with the heater. Assume that all the heat energy is transferred to the water. Suppose the inlet water temperature is 12°C and the flow rate is 8.0 L/min (about that of a standard shower head). What is the outlet temperature? Express your answer in degrees Celsius. ? Tout = °C Submit Request Answer Provide Feedback Next >arrow_forwardSipho’s mother is making a fire in the stove inside a shack using coal. A fan is used to extract the flue gasfrom the fire via a chimney made of zinc material. The wall thickness of Chimney is L=4mm and the walltemperature of the chimney on the flue gas side is T_si=60˚C. Sipho, playing outside next to the chimneyexperiences an ambient temperature of 20˚C. The surrounding temperature is T_sur=35˚C and the emissivityis ε=0.95. Assume the convection coefficient is 20W/m2K and the chimney is grey material.Under these conditions determine the outer surface (air side) temperature T_so=? of the chimney.arrow_forwardA 10 ft length of pipe with an inner radius of 1 in and outer radius of 1.25 in has an outer surface temperature of 250 F. The heat transfer rate is 30,000 BTU/hr. Find the interior surface temperature. Assume k = 25 BTU/hr-ft-F.arrow_forward
- Ex1. A piece of chromium steel of length 7.4cm (density=8780kg/m³ ; k = 50w/mK and specific heat cp = 440j/kgK) with mass 1.27kg is rolled into a solid cylinder and heated to a temperature of 600°C and quenched in oil at 36°c. Show that the lumped capacitance system analysis is applicable and find the temperature of the cylinder after 4min. What is the total heat transfer during this period? You may take the convective heat transfer coefficient between the oil and cylinder at 280w/m2k.arrow_forward3 • A piece of chromium steel of length 7.4cm (density= 8780kg/m³, k=50 W/m K) and specific heat capacity (C,=440 J/kg K) with mass 1.27 kg is rolled into a solid cylinder and heated to a temperature of 600 °C and quenched in oil at 36 °C. Show that the lumped capacitance system analysis is applicable and find the temperature of the cylinder after 4min. What is the total heat transfer during this period? You may take the convective heat transfer coefficient between the oil and cylinder at 280 W/m2K. delete home < backsac ock 7. home F enter 4.arrow_forward1. A small metal building is to be constructed of corrugated steel sheet walls with a total wall surface area of about 300 m². The air conditioner consumes about 1 kW of electricity for every 4 kW of cooling supplied and two wall construction are to be compared on the basis of cooling costs. Assume that electricity costs S0.15/kWh. Determine the electrical energy savings per week of using 260 mm of fiberglass batt insulation to the steel sheet wall (U-0.17 W/m² "C) instead of 159 mm of fiberglass insulation (U-0.31 W/m² °C) assuming an overall temperature difference of 20 °C across the wall.arrow_forward
- In a thermal power plant, a horizontal copper pipe of "D" diameter, "L" length and thickness 1.2 cm enters into the boiler that has the thermal conductivity as 0.37 W/mK. The boiler is maintained at 113C and temperature of the water that flows inside the pipe is at 29C. If the energy transfer (Q) is 118779 kJ in 7 hours. Calculate: 4-Length of the pipe, if D = 0.017 L. 5-Pipe Diameter (in mm)arrow_forwardA Pressurized Water Reactor fuel rod is 12 ft long and 0.374 inches in diameter (outer) on a 0.496 inch square pitch. The fuel pellet diameter is 0.3225 inches. The fuel rod gap is constant with a width of 0.0065 inches. The system pressure is 2250 psia and can be assumed to be constant. The rod operates at linear heat rate of 12.1 kW/ft. At the elevation of interest, the coolant temperature is 575 °F with a convective heat transfer coefficient of 6200- For this elevation determine the temperature BTU hr ft²F margin to boiling according to Jens-Lottes. Also assume constant fluid properties given as: p=46.39 Ibm = ,c. 1.261- BTU Ibm-F BTU -,k=0.334- hr-ft-F Ibm ft-hr M=0.222- -, Tsat 652.7F =arrow_forwardAn array of 190 electrical components, each dissipating P = 35 W, are attached to the bottom surface of a square copper plate. The length of the edge of the square plate is L= 0.1 m. All of the energy dissipated in the electrical components is transferred to water flowing over the top surface of the copper plate. The water flow over the plate in a direction that is parallel to the edge of the plate. A proturbence at the leading edge of the plate acts to trip the bounary layer into turbulent flow. The plate may be assumed to be isothermal since the thermal conductivity of copper is so high. The water velocity and temperature far from the plate are u» = 2.3 m/s and To = 22 °C. The water's thermophysical properties (for application in correlations for the Nusselt number) may be approximated as v = 0.96×10-6 m2/s, kf = 0.62 W/m-K, and Pr = 5.2. What is the temperature of the copper plate in °C?arrow_forward
- n electric generator at a power plant produces energy by passing superheated steam from a high temperature container (reservoir), through a pipe connected to a series of fans, and then into a low temperature reservoir. As the steam passes across the blades of the fans some of the heat energy of the steam is transformed into mechanical energy, which turns the fans which in turn are connected to a generator, which in turn converts the mechanical energy into electrical energy. If the high temperature steam has a temperature of 412.1 K and the low temperature reservoir has a temperature of 105.4 K, what is the Carnot efficiency of this process?arrow_forwardThe steel pipe has an internal radius of 50 mm., a thickness of 5 mm. and a length of 5 m. Inside the pipe, hot fluid with temperature 80 C flows inside the pipe and cold fluid with temperature 20 C flowing outside the pipe. Let k=285 W/mC and hi= 25 W/mC, ho= 10 W/mC. Find 4.1) Heat Transfer Rate (Q) 4.2) Temperature on both inner and outer tube surfaces...arrow_forward2. For a saturated dry steam at 1,500 KPa that passes through a 100 mm (OD) steel pipe with a thickness of 5 mm and a length of 100 meters. The steam line is insulated with a 50 mm thickness and a thermal conductivity of 0.25 W/m.C. For a mass flow rate of 600 kg of steam per hour. The surface film conductance of steam is h = 5,500 W/m?.C, surface film conductance of air is h = 12 W/m?.C , thermal conductivity of pipe material is k = 153 W/m.C and the ambient air temperature is -10°C . Determine the following: a) The quality of steam after passing through the pipe b) Explain the concepts/principles that were considered and the factors that affected the condition of the above mentioned items (a & b) @ 1,500 KPa (tsat = 198.32°C) kJ 2,792.20- kg k] 844.89 kg kJ 1,947.30- kg 1 hg 2 hf hfgarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning
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