Psychrometrics – Lecture 3Lecture 1 and 2 ReviewSlide 3Slide 4Psychrometric Processes: Addition of Water at any stateSlide 6Psychrometric Processes: Animal HousingSlide 81Dr. C. L. JonesBiosystems and Ag. EngineeringPsychrometrics – Lecture 32Dr. C. L. JonesBiosystems and Ag. EngineeringLecture 1 and 2 Review •This is all about removing and adding water from materials and from air-water vapor •Knowing 2 of the properties of a state point, we can find the other 5 properties•Wet Bulb T, Dry Bulb T, Dew Point, RH, enthalpy h, humidity ratio H, specific volume v3Dr. C. L. JonesBiosystems and Ag. EngineeringLecture 1 and 2 Review •Cooling and heating without changing amount of moisture: moves along a horizontal line (humidity ratio H stays the same…everything else changes)•In a mixing process (2 air streams at different state points)…resultant state point will lay on a line between the two initial stages4Dr. C. L. JonesBiosystems and Ag. EngineeringLecture 1 and 2 Review •Product drying process using air: adiabatic…follows the enthalpy line…wet bulb stays the same, enthalpy stays the same, everything else changes5Dr. C. L. JonesBiosystems and Ag. EngineeringPsychrometric Processes: Addition of Water at any state•Changes enthalpy and humidity ratio…and everything else, Figure 9.12•Mass of water: (eqtn 9.100) •Energy balance: (eqtn 9.101) •Example 9.146Dr. C. L. JonesBiosystems and Ag. EngineeringPsychrometric Processes: Addition of Water at any state•Greenhouse plants like to be kept at 30°C and 95% rh. •To achieve this condition, steam at 160°C is injected into the ventilation air stream (20°C, 30% rh). •Mass flow rate of the air stream is 1800 kg/min and the mass flow rate of the steam is 5 kg/min. •Will this system achieve the ideal conditions for the plants?7Dr. C. L. JonesBiosystems and Ag. EngineeringPsychrometric Processes: Animal Housing •What ventilation rate is needed in a swine finishing confinement building with a solid floor and 140 head of 150 lb pigs for outside temperatures from -10F to 50F? •Assume inside conditions of 60F and 80%RN and outside RH of 80%8Dr. C. L. JonesBiosystems and Ag. EngineeringPsychrometric Processes: Animal Housing •What ventilation rate is needed in a poultry confinement building with hanging cages over pits and 690 4-lb laying hens for outside temperatues from -10 to 50F? •Assume inside conditions of 60F and 70%RN and outside RH of
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