BAE4400 Topics in Processing Fall 2006 August 22 through September 21 1 hour credit Dr. C. L. Jones Biosystems and Ag. Engineering

Psychrometrics – Lectures 5, 6, & 7 Assignment: Read Chapter 9 in Henderson/Perry HW #4 Due 9/14/06 GO TO THE CAREER FAIRS!!!!! Dr. C. L. Jones Biosystems and Ag. Engineering

Psychrometric Processes: Adiabatic Process Adiabatic: a procedure whereby there is a change from one state to another without heat exchange between system and surroundings Follows the wet bulb line, H changes, h stays the same Examples: evap. cooling, dehumidification by absorption Dr. C. L. Jones Biosystems and Ag. Engineering

Psychrometric Processes: Adiabatic Process Example Moisture content of a large container of coconut must be reduced by removing moisture from the container. Air at 40°C, 25% rh will be passed through the container at 13 m^3/s. What is the maximum rate of moisture removal? Dr. C. L. Jones Biosystems and Ag. Engineering

Psychrometric Processes: Adiabatic Process Example If the original weight and moisture content of the coconut was 500 kg at 75% (wb), what will be the moisture content after 15 minutes of aeration? Dr. C. L. Jones Biosystems and Ag. Engineering

Psychrometric Processes: Addition of Water at any state Changes enthalpy and humidity ratio Mass of water: (eqtn 9.100) Energy balance: (eqtn 9.101) Dr. C. L. Jones Biosystems and Ag. Engineering

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