On a very Still morning, the surface temperature of a lake used to cool the condenser of a power plant is 30°C while the air temperature is 23°C with a relative humidity of 80%. Assume a surroundings temperature of 285 K. The lake is nominally circular in shape with a diameter of approximately 4 km. Determine the heat loss from the surface of the lake by radiation, free convection, and evaporation. This heat loss determines the capacity of the lake to cool the condenser. Justify why the heat transfer correlation you select is useful, even though
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- Thermal energy generated by the electrical resistance of a 5-mm-diameter and 4-m-long bare cable is dissipated to the surrounding air at 80°C. The voltage drop and the electric current across the cable in steady operation are measured to be 20.0 V and 4.5 A, respectively. Disregarding radiation, estimate the surface temperature of the cable. Evaluate air properties at a film temperature of 100°C and 1 atm pressure.arrow_forwardVolumetric thermal expansion is used in modeling natural convection heat transfer. Derive an expression for volumetric thermal expansion coefficient for an ideal gas.arrow_forwardThe free convection heat transfer coefficient on a thin hot vertical plate suspended in still air can be determined from observations of the change in plate temperature with time as it cools. Assuming the plate is isothermal and radiation exchange with its surroundings is negligible, evaluate the convection coefficient at the instant of time when the plate temperature is Tplate = 277 °C and the change in plate temperature with time (dT/dt) is −0.022 K/s. The ambient air temperature is Tinf = 28°C and the plate measures 0.7 × 0.7 m with a mass of 5.56 kg and a specific heat of 2,780 J/kg · K.arrow_forward
- Thermal energy generated by the electrical resistance of a 5-mm-diameter and 4-m- long bare cable is dissipated to the surrounding air at 80°C. The voltage drop and the electric current across the cable in steady operation are measured to be 18 V and 5 A, respectively. Disregarding radiation, estimate the surface temperature of the cable. Evaluate air properties at a film temperature of 100°C and 1 atm pressure.arrow_forwardA can of engine oil with a length of 150 mm and a diameter of 100 mm is placed vertically in the trunk of a car. In a hot summer day, the temperature in the trunk is 43°C. If the surface temperature of the can is 17°C, determine heat transfer rate from the can surface. Neglect the heat transfer from the ends of the can.arrow_forwardA double window called thermopane is one in which two layers of glass are used separated by a layer o dry stagnant air: In a given window, each of the glass layers is 6.35 mm thick separated by a 6.35 mm space of stagnant air. The thermal conductivity of the glass is 0.869 W/m K and that of air is 0.026 over the temperature range used. For temperature drop of 27.8 K over the system, calculate the heat loss for a window 0.914 m 1.83 m.arrow_forward
- EXTERNAL FORCED CONVECTION A 10-cm-diameter, 30-cm-high cylindrical bottle contains cold water at 38°C. The bottle is placed in windy air at 27°C. The water temperature is measured to be 11°C after 45 min of cooling. Disregarding radiation effects and heat transfer from the top and bottom surfaces, estimate the average wind velocity. Please, I need the solution from fundamental concepts of how the heat flow behaves in the system. That it be answered with theory of the subjectarrow_forwardThe boiling temperature of nitrogen at atmospheric pressure at sea level (1 atm) is -196°C. Therefore, nitrogen is commonly used in low temperature scientific studies since the temperature of liquid nitrogen in a tank open to the atmosphere will remain constant at -196°C until the liquid nitrogen in the tank is depleted. Any heat transfer to the tank will result in the evaporation of some liquid nitrogen, which has a heat of vaporization of 198 kJ/kg and a density of 810 kg/m3 at 1 atm. Consider a 3-m-diameter spherical tank initially filled with liquid nitrogen at 1 atm and 196°C. The tank is exposed to 22°C ambient air with a heat transfer coefficient of 22 W/m2 · °C. The temperature of the thin-shelled spherical tank is observed to be almost the same as the temperature of the nitrogen inside. Disregarding any radiation heat exchange, determine the rate of evaporation of the liquid nitrogen in the tank as a result of the heat transfer from the ambient air in kg/sec. Answer in…arrow_forwardUnder conditions for which the same room temperature is maintained by a heating or cooling system, it is not uncommon for a person to feel chilled in the winter but comfortable in the summer. Consider a room whose air temperature is maintained at 16°C throughout the year, while the walls of the room are nominally at 30°C and 14°C in the summer and winter, respectively. The exposed surface of a person in the room may be assumed to be at a temperature of 32°C throughout the year and to have an emissivity of 0.90. The coefficient associated with heat transfer by natural convection between the person and the room air is approximately 2 W/m2.K. Calculate the following. Heat flux due to convection: q'onv W/m? Heat flux due to radiation in the summer: i W/m? Heat flux due to radiation in the winter: qad W/m? i ||arrow_forward
- Estimate the rate of heat transfer (J/s) from a 50.6°C sphere which has an emissivity of 0.2 if it is suspended in a cold volume maintained at -10.7°C. The sphere has a diameter of 0.2m. Reduce your answer in to two decimal point.arrow_forwardUnder conditions for which the same room temperature is maintained by a heating or cooling system, it is not uncommon for a person to feel chilled in the winter but comfortable in the summer. Consider a room whose air temperature is maintained at 22°C throughout the year, while the walls of the room are nominally at 26°C and 16°C in the summer and winter, respectively. The exposed surface of a person in the room may be assumed to be at a temperature of 32°C throughout the year and to have an emissivity of 0.90. The coefficient associated with heat transfer by natural convection between the person and the room air is approximately 2 W/m2-K. Calculate the following. Heat flux due to convection: i W/m? Heat flux due to radiation in the summer: gad W/m2 i Heat flux due to radiation in the winter: Trad W/m? iarrow_forwardDifferentiate between free and forced convection with examples.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning