Psychrometer chart: Range can be changed, Mouse move point calculation; Calculate once recycle and twice recycle air flow, summer and winter state, process line shown in chart, press UpDown button to see process changing; Export wmf format file, can be opened and printed by image browser as ACDSee, IE, smoothly zoomed. Duct calculator: Air and liquid duct; Calculate duct flow resistance, environmental heat exchange, and adiabatic