Concept explainers
An electrical heater capable of generating 10,000 W is to be designed. The heating element is to be a stainless steel wire having an electrical resistivity of
Want to see the full answer?
Check out a sample textbook solutionChapter 2 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
- Calculate the overall heat transfer coefficient of the steel pipe based on the inner surface. The inner diameter of the pipe is 12.7 cm, and the thickness of the pipe is 2.4 cm. The convective heat transfer coefficient in the pipe is 350 W / (m² °C), the convective heat transfer coefficient outside the pipe is 25 W / (m² °C), the thermal conductivity of the steel pipe is 15 W / (m °C) . If a pipe is used to deliver steam at 110 °C and the ambient temperature is 30 °C, determine the rate of heat transfer from the pipe per meter. q = AnswerWatts/marrow_forwardThe walls of the refrigerated storage room are 10 m long and 3 m high and constructed with 90 mm concrete blocks (k = 0.935 W / [m ° C]) and 12 cm fiber insulation board (k = 0.048 W). / [m ° C]). The temperature of the cold room is -10 ° C and the convective hot coupling is 40 W / (m² K); The outside air temperature is 30 ° C with a convection heat transfer coefficient of 10 W / (m² K). Calculate the total heat wave. Total heat transfer coefficient = Answer W / (m² K).arrow_forwardQuestion 2 Consider a 1.5-m-high electric hot-water heater that has a diameter of 40 cm and maintains the hot water at 60 °C. The tank is located in a small room whose average temperature is 27 °C, and the heat transfer coefficients on the inner and outer surfaces of the heater are 50 and 12 W/m2⋅K, respectively. The tank is placed in another 46-cm-diameter sheet metal tank of negligible thickness, and the space between the two tanks is filled with foam insulation (k = 0.03 W/m⋅K). The thermal resistances of the water tank and the outer thin sheet metal shell are very small and can be neglected. The price of electricity is $0.08/kWh, and the homeowner pays $280 a year for water heating. Determine the fraction of the hot-water energy cost (in %) of this household that is due to the heat loss from the tank. Heat transfers through the top and bottom of the tank are negligible. In continuation of Question 2, hot-water tank insulation kits consisting of 3-cm-thick fiberglass insulation…arrow_forward
- Electric heater wires are installed in a solid wall having a thickness of 8 cm and k=2.5W/m- °C. The right face is exposed to an environment with h=50W/m^ 2 . C and T infty =30^ C , while the left face is exposed to h=75 W/m^ 2 C T infty =50^ C . What is the maximum allowable heat-generation rate such that the maximum tem perature in the solid does not exceed 300 degrees * C ?arrow_forwardThe walls of the refrigerated storage room are 10 m long and 3 m high and constructed with 90 mm concrete blocks (k = 0.935 W / [m ° C]) and 8 cm fiber insulation board (k = 0.048 W). / [m ° C]). The cold room temperature is -10 ° C and the convective heat transfer coefficient is 40 W / (m² K); the outside air temperature is 30 ° C with the outer wall surface convection heat transfer coefficient of 10 W / (m² K). Calculate the overall heat transfer coefficient. Overall heat transfer coefficient = Answer W / (m² K).arrow_forwardQuestion No. 17(a) A steel tube k=43.26 W/mK of 5.08 cm 10 and 7.62 cm 00 is covered with 2.54 cm of asbestos insulation k=0.208 W/Mk. The inside surface of the tube receives heat by convection from a hotgas at a -temperature of 316°C with heat transfer coefficient ha=284 W/m2K while the outer surface of Insulation is exposed to atmosphere air at 38°C with heat transfer coefficient of 17 W/m2 K Calculate heat loss to atmosphere for 3 m length of the tube and temperature drop across each layer. (b) Explain with neat sketch about pulverized fuel furnaces and its types.arrow_forward
- In the context of a Spark Ignition (SI) engine, consider a moment during combustion when there is a heat flux through the wall of the combustion chamber at a specific location, measured at 219 kW/m2. The gas temperature within the cylinder at this time is 2300 K, and the convection heat transfer coefficient within the cylinder is 120 W/m2⋅K. The coolant temperature is 80 °C. The thickness of the cylinder wall is 10mm with a thermal conductivity of 200 W/m⋅K. (a) Determine the temperature of the inner surface of the cylinder wall. (b) Find the temperature on the side of the cylinder wall facing the coolant. (c) Calculate the heat transfer coefficient on the coolant side of the cylinder wallarrow_forwardThe inside of a hollow cylinder is maintained at a temperature ??, and the outside is at a lower temperature, ??. The wall of the cylinder has a thermal conductivity ?. Ignoring end effects, show that the rate of energy conduction from the inner surface to the outer surface in the radial direction is ??/?? = 2??? [?? − ??/ ln(?/?)]The passenger section of a jet airliner is in the shape of a cylindrical tube with a length of 35.0 m and an inner radius of 2.50 m. Its walls are lined with an insulating material 6.00cm in thickness and having a thermal conductivity of 4.00 × 10−5cal/s ⋅ cm ⋅ °C. A heater must maintain the interior temperature at 25.0°C while the outside temperature is −35.0°C. What power must be supplied to the heater?arrow_forwardConvective heat transfer coefficient is 15 W/(m*K), surface area of the fin is 2 m^2, the temperature at the base is 70 C and the ambient temperature is 20 C. Determine the fin efficiency if the actual heat transfer rate from the fin is 500 W?arrow_forward
- Hot water at an average temperature of 70°C is flowing over a 15-m section of a cast iron pipe (k = 52 W/m·K) whose inner and outer diameters are 4 cm and 4.6 cm, respectively. The inner surface of the pipe exchanges heat by convection and radiation to the cold air at 10°C inside the pipe, with a convective heat transfer coefficient of 15 W/m2·K and heat transfer coefficient for radiation is 6.157 W/m2·K. The heat transfer coefficient at the outer surface of the pipe in the hot water side is 120 W/m2·K, Draw the thermal resistance network and determine the rate of heat loss from the hot water.arrow_forwardA 2-m x 1.8-m section of wall of an industrial furnace burning natural gas is not insulated, and the temperature at the outer surface of this section is measured to be 80°C. The temperature of the furnace room is 30°C, and the combined convection and radiation heat transfer coefficient at the surface of the outer furnace is 10 W/m² • °C. It is proposed to insulate this section of the furnace wall with expanded perlite insulation (k = 0.052 W/m • °C) in order to reduce the heat loss by 90%. Assuming the outer surface temperature of the metal section still remains at about 80°C, determine the thickness of the insulation that needs to be used. ANSWER:_______cmarrow_forwardA heater plate measures 40 cm x 40 cm in the tank and is kept at a constant temperature of 70 oC.Show the calculations in which case it can heat the oil at a temperature of 30 oC in the tank. For oil: ν=0.00026 m2 / s, k=0.15 W / mK, Pr=2900arrow_forward
- Elements Of ElectromagneticsMechanical EngineeringISBN:9780190698614Author:Sadiku, Matthew N. O.Publisher:Oxford University PressMechanics of Materials (10th Edition)Mechanical EngineeringISBN:9780134319650Author:Russell C. HibbelerPublisher:PEARSONThermodynamics: An Engineering ApproachMechanical EngineeringISBN:9781259822674Author:Yunus A. Cengel Dr., Michael A. BolesPublisher:McGraw-Hill Education
- Control Systems EngineeringMechanical EngineeringISBN:9781118170519Author:Norman S. NisePublisher:WILEYMechanics of Materials (MindTap Course List)Mechanical EngineeringISBN:9781337093347Author:Barry J. Goodno, James M. GerePublisher:Cengage LearningEngineering Mechanics: StaticsMechanical EngineeringISBN:9781118807330Author:James L. Meriam, L. G. Kraige, J. N. BoltonPublisher:WILEY