A 2-cm-high cylindrical ice block
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HEAT+MASS TRANSFER:FUND.+APPL.
- 1.60 Two electric resistance heaters with a 20 cm length and a 2 cm diameter are inserted into a well-insulated 40-L tank of water that is initially at 300 K. If each heater dissipates 500 W, what is the time required for bringing the water temperature in the tank to 340 K? State your assumption for your analysis.arrow_forward2.38 The addition of aluminum fins has been suggested to increase the rate of heat dissipation from one side of an electronic device 1 m wide and 1 m tall. The fins are to be rectangular in cross section, 2.5 cm long and 0.25 cm thick, as shown in the figure. There are to be 100 fins per meter. The convection heat transfer coefficient, both for the wall and the fins, is estimated to be K. With this information determine the percent increase in the rate of heat transfer of the finned wall compared to the bare wall.arrow_forward3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on one side is and on the other side is . If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it takes for the copper plate to reach a temperature of 82°C.arrow_forward
- Q2/ A 4-m-internal-diameter spherical tank made of 1.75-cm-thick stainless steel (k 15 W/m °C) is used to store iced water at 0°C. The tank is located in a room whose temperature is 35°C. The walls of the room are also at 35°C. The outer surface of the tank is black, and heat transfer between the outer surface of the tank and the surroundings is by natural convection and radiation. The convection heat transfer coefficients at the inner and the outer surfaces of the tank are 80 W/m2 °C and 10 W/m2· °C, respectively. Determine (a) the rate of heat transfer to the iced water in the tank and (b) the amount of ice at 0°C that melts during a l-h period. The heat of fusion of water at atmospheric pressure is hif 334 kJ/kg.arrow_forwardA glass window in a storefront has an are of 12m2 and a thickness of 1 cm. The thermal conductivity of the glass is 0.8 W/m-oC. On the cold day, outside surface temperature of the glass is -1oC and the inside surface temperature is 3 oC. Determine the temperature at a plane midway between the inside and outside glass surfaces.arrow_forwardThe hot water pipe of a heating system, 20 m long and 8 cm in diameter, was buried 80 cm below the soil surface. The outer surface temperature of the pipe is 60 °C. Find the heat loss rate in the pipe by taking the surface temperature of the soil as 5°C and the thermal conductivity of the soil at that location as 0.9 W/m°C.arrow_forward
- Q2/ A 3-m internal diameter spherical tank made of 2-cm-thick stataless steel (k= 15 W/m 0°C. The tank is located in a room whose %3D C) is used to store iced water at Te temperature is T-22°C. The walls of the room are also at 22°C. The outer surface of the tank is black and heat transfer between the outer surface of the tank and the surroundings is by natural convection and radiation. The convection heat transfer coefficients at the inner and the outer surfaces of the tank are h-80 W/m2 C and h 10 W/m2 C, respectively. Determine (a) the rate of heat transfer to the iced water in the tank and (b) the amount of ice at 0°C that melts during a 24-h period.arrow_forwardA glass window inside storefront has an are of 12m2 and a thickness of 1 cm. The thermal conductivity of the glass is 0.8 W/m-oC. On the cold day, outside surface temperature of the glass is -1oC and the inside surface temperature is 3 oC. Determine the temperature at a plane midway between the inside and outside glass surfaces.arrow_forward. A hot surface at 100°C is to be cooled by attach- ing 3-cm-long, 0.25-cm-diameter aluminum pin fins (k = 237 W/m - °C) to it, with a center-to-center distance of 0.6 cm. The temperature of the surrounding medium is 30°C, and the heat transfer coefficient on the surfaces is 35 W/m² . °C. Determine the rate of heat transfer from the surface for a 1-m x 1-m section of the plate. Also determine the overall effectiveness of the fins. 3 cm. 0.6 cm dn 0.25 cmarrow_forward
- A spherical container is made of plastic (k=2 W/mK, ρ=5000 kg/m) and has inner and outer radii of 10 cm and 11 cm, respectively. Hot oil (c=3000 J/kgK, ρ=800 kg/m3) at 80 0C is stored within the container and the heat transfer coefficient between the oil and the inner surface of the container h=5 W/m2K. The outer surface of the container is perfectly insulated. Solve the differential equation under the boundary conditions for steady one dimensional heat conduction through the plastic material. h (W/m2K)=? a) Obtain an equation for the variation of temperature within the plastic material b) Calculate the temperature of the plastic material at the inner surface c) Calculate the temperature of the plastic material at the inner surfacearrow_forward10 m long pipe is being used to deliver steam through a processing plant. The inner radius of the pipe is ri = 6 cm and the thickness of the pipe is 2 cm. Thermal conductivity k = 8 W/m-K and the average temperature steam flowing through the pipe is 160°C, the average convection heat transfer coefficient on the inner surface is given to be h = 20 W/m2-K. If the average temperature on the outer surfaces of the pipe is T2 = 70°C, (a) express the differential equation and the boundary conditions for steady operating conditions, (b) determine a relation for the variation of temperature in the pipe, and (c) evaluate the rate of heat loss (heat of conduction) from the steam through the pipe.arrow_forwardA 5-cm-external-diameter, 10-m-long hot-water pipe at 80 deg C is losing heat to the surrounding air at 5 deg C by natural convection with a heat transfer coefficient of 25 W/m^2.K. Determine the rate of heat loss from the pipe by natural convection (6m)arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning