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Psychrometrics – Lecture 3

Psychrometrics – Lecture 3. Dr. C. L. Jones Biosystems and Ag. Engineering . Lecture 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

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Psychrometrics – Lecture 3

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  1. Psychrometrics – Lecture 3 Dr. C. L. Jones Biosystems and Ag. Engineering

  2. Lecture 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 v Dr. C. L. Jones Biosystems and Ag. Engineering

  3. Lecture 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 stages Dr. C. L. Jones Biosystems and Ag. Engineering

  4. Lecture 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 changes Dr. C. L. Jones Biosystems and Ag. Engineering

  5. Psychrometric 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 9.14 Dr. C. L. Jones Biosystems and Ag. Engineering

  6. Psychrometric 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? Dr. C. L. Jones Biosystems and Ag. Engineering

  7. Psychrometric 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% Dr. C. L. Jones Biosystems and Ag. Engineering

  8. Psychrometric 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 80%. Dr. C. L. Jones Biosystems and Ag. Engineering

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