Cold air at 20 F, 760 mm Hg pressure, and 70% relative humidity is conditioned by being passed through a bank of heating coils, then through a water spray, and finally through a second set of heatingcoils.Inpassingthroughthefirstcoilbank,theairisheatedto75 F.Thetemperatureofthe water supplied to the spray chamber is adjusted to the wet-bulb temperature of the air admitted to thechamber,sothatthehumidifyingunitmaybeassumedtooperateadiabatically.Itisrequiredthat the air emerging from the conditioning unit be at 70 F and 35% relative humidity. Use Figure 8.4-2 to solve the following problems. Calculatethetemperatureofthewatersuppliedtothespraychamberandtherelativehumidity and dry-bulb temperature of the air leaving the spray chamber. Calculate the mass of water evaporated (lb ) per cubic foot of air fed to the conditioning unit. Calculatetherequiredheattransferrates(Btu/ft enteringair)ineachoftheheatingcoilbanks. Sketch a psychrometric chart and show the path followed by the air in each of the three steps of this process.
Cold air at 20 F, 760 mm Hg pressure, and 70% relative humidity is conditioned by being passed through a bank of heating coils, then through a water spray, and finally through a second set of heatingcoils.Inpassingthroughthefirstcoilbank,theairisheatedto75 F.Thetemperatureofthe water supplied to the spray chamber is adjusted to the wet-bulb temperature of the air admitted to thechamber,sothatthehumidifyingunitmaybeassumedtooperateadiabatically.Itisrequiredthat the air emerging from the conditioning unit be at 70 F and 35% relative humidity. Use Figure 8.4-2 to solve the following problems. Calculatethetemperatureofthewatersuppliedtothespraychamberandtherelativehumidity and dry-bulb temperature of the air leaving the spray chamber. Calculate the mass of water evaporated (lb ) per cubic foot of air fed to the conditioning unit. Calculatetherequiredheattransferrates(Btu/ft enteringair)ineachoftheheatingcoilbanks. Sketch a psychrometric chart and show the path followed by the air in each of the three steps of this process.
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