Air at 30 oC flowing over a flat plate 0.5 m long and 0.6 m wide, is to be maintained at 70 oC . Determine the velocity of air which must flow over a side of 0.5m. The rate of energy dissipation from the plate is .3 KW
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- Air with dby bulb temperature of 25C PSAT = 3.169kpa and wet bulb temperature of 15C PSAT=1.7051 kpa flows in round duct of diameter 800m with velocity of 7m/S Determine Mass flow rate (answer. 249kg/min) Mass flow rate of dry air (answer 247 kg/min)The effective surface temperature of the coil is 5°C. The surface area of the coil is such as would give 4.6 TR with the given entering air state of 40 m3/min of a mixture of recirculated room air and outdoor air enters cooling coil at 27°C dry bulb temperature and 15°C wet bulb temperature.. Determine the conditions of the air leaving the coil and the by-pass factor.air at a dry ball temperature of 80 degrees C and 4% RH is passed over the cooling coil so that the temperature of the air dry ball becomes 35 degrees Celsius. how much heat is released from the air in the process? (answer in kj / kg)
- In a geothermal power plant, the used geothermal water at 80°C enters a 15-cm-diameter and 400-m-long uninsulated pipe at a rate of 8.5 kg/s and leaves at 70°C before being reinjected back to the ground. Windy air at 15°C flows normal to the pipe. Disregarding radiation, determine the average wind velocity in km/h.One house owner with a pond on his property has decided to use the pond water to cool his house. His idea is to flow air through a thin smooth 10-cm-diameter copper tube that could be submerged into the pond. The water in the pond, at few meters below the surface is typically maintained at a constant temperature of 15°C. If he assumes the air (~1 atm) entering the copper tube at a mean temperature of 30°C with an average velocity of 2.5 m/s, determine the necessary copper tube length that would be needed so that the outlet mean temperature of the air is 20°C. You may consider the convection heat transfer coefficient of 1000 W/m2·K on the outer surface of the copper tube, between the pond water and copper tube. Since the copper tube is thin, the conduction resistance of the tube wall may be neglected.Consider an air solar collector that is 1 m wide and 5 m longand has a constant spacing of 3 cm between the glass cover andthe collector plate. Air enters the collector at 30°C at a rate of0.15 m3/s through the 1-m-wide edge and flows along the 5-mlong passage way. If the average temperatures of the glasscover and the collector plate are 20°C and 60°C, respectively,determine (a) the net rate of heat transfer to the air in thecollector and (b) the temperature rise of air as it flows throughthe collector.
- Air enters a 25-cm-diameter 12-m-long underwater duct at 50°C and 1 atm at a mean velocity of 7 m/s, and is cooled by the water outside. If the average heat transfer coefficient is 85 W/m2?K and the tube temperature is nearly equal to the water temperature of 10°C, determine the exit temperature of air and the rate of heat transfer. Evaluate air properties at a bulk mean temperature of 30°C. Is this a good assumption?The effective surface temperature of the coil is 5°C. The surface area of the coil is such as would give 4.6 TR with the given entering air state of 40 m¾/min of a mixture of re- circulated room air and outdoor air enters cooling coil at 27°C dry bulb temperature and 15°C wet bulb temperature.. Determine the conditions of the air leaving the coil and the by-pass factor.During air cooling of oranges, grapefruit, andtangelos, the heat transfer coefficient for combined convection,radiation, and evaporation for air velocities of0.11 < V < 0.33 m/s is determined experimentally and isexpressed as h = 5.05 kair Re1/3/D, where the diameter Dis the characteristic length. Oranges are cooled by refrigeratedair at 5°C and 1 atm at a velocity of 0.3 m/s. Determine(a) the initial rate of heat transfer from a 7-cm-diameterorange initially at 15°C with a thermal conductivity of0.50 W/m·K, (b) the value of the initial temperature gradientinside the orange at the surface, and (c) the value of theNusselt number.
- In the effort to increase the removal of heat from a hot surface at 120°C, a cylindrical pin fin (kf = 237 W/m.K) with diameter of 5 mm is attached to the hot surface. Air at 20°C (1 atm) is flowing across the pin fin with a velocity of 10 m/s. Determine the maximum possible rate of heat transfer from the pin fin. Evaluate the air properties at 70°C.Agas at 0°C and avelocity of 2.5 m/s, flows over a 1.2 m long, 2m wide plate that is maintained at 80°C. If the gas properties are: Density = 1.142 kg/m3 , cp = 1.04 kJ/kg.K, ν= 15.63×10 -6m2 /s, k = 0.0262 W/m.K,and Pr= 0.708,determine: (a)The critical length of the flow[m] (b)The average heat transfer coefficient[W/m2 .K] (c)Total rate of heat transfer from the plate[W]A 4-m x 4-m flat plate maintained at a constant temperature of 80°C is subjected to parallel flow of air at 1 atm, 20°C, and 10 m/s. The total drag force acting on the upper surface of the plate is measured to be 2.4 N. Using momentum heat transfer analogy, determine the average convection heat transfer coefficient, and the rate of heat transfer between the upper surface of the plate and the air