# APPENDIX 1 - PREFIXES AND CONVERSION FACTORS

## Prefixes

Units can be used as such or in multiples or fractions of ten:

 PREFIX POWER OF TEN T tera 1012 G giga 109 M mega 106 k kilo 103 h hecto 102 da deca 101 d deci 10-1 c centi 10-2 m milli 10-3 m micro 10-6 n nano 10-9 P pico 10-12 f femto 10-15 a atto 10-18

1 m = 100 cm = 1000 mm
1 m2 = 10 000 cm2 = 106 mm2
1 m3 = 106 cm3 = 109 mm3
1 Mg m-3 = 103 kg m-3 = 1 g cm-3
1 kPa = 10 mbar
1 joule = 0.2388 cal
1 watt = 1 J s-1 = 0.8598 kcal h-1
1 W m-2 = 0.8598 kcal m-2 h-1
1 W m-2 = 1.433 × 10-3 cal cm-2 min-1
1 Hp = 745.7 W
1 W = 0.001431 Hp
Water flow (m3 s-1) = 0.55 × Pump power (W)/Pressure (kPa)
Water flow (litre s-1) = 5.43 × Pump power (kilowatts)/pressure (bars)

Brake Horsepower is the horsepower for an electric motor. Do not use for fuel-powered engines.

## Conversion factors

### Temperature

Standard unit: degree Celsius (°C)

 degree Fahrenheit (°F) °C = (°F-32) 5/9 kelvin(s) (K) K = °C +273.15

### Pressure (air pressure, vapour pressure)

Standard unit: kilopascal (kPa)

 millibar (mbar) 1 mbar = 0.1 kPa Bar 1 bar = 100 kPa centimetre of water (cm) 1 cm of water = 0.09807 kPa millimetre of mercury (mm Hg) 1 mm hg = 0.1333 kPa atmosphere (atm) 1 atm =101.325 kPa pound per square inch (psi) 1 psi = 6.896 kPa

### Wind speed

Standard unit: metre per second (m s-1)

 kilometre per day (km day-1) 1 km day-1 = 0.01157 m s-1 nautical mile/hour (knot) 1 knot = 0.5144 m s-1 foot per second (ft s-1) 1 ft s-1 = 0.3048 m s-1

### Radiation

Standard unit: megajoule per square metre and per day (MJ m2 day-1) or as equivalent evaporation in mm per day (mm day-1)

 equivalent evaporation (mm/day) 1 mm day-1 = 2.45 MJ m-2 day-1 joule per cm2 per day (J cm-2 day-1) 1 J cm-2 day-1 = 0.01 MJ m-2 day-1 calorie per cm2 per day (cal cm-2 day-1) 1 cal = 4.1868 J = 4.1868 10-6 MJ 1 cal cm-2 day-1 = 4.1868 10-2 MJ m-2 day-1 watt per m2 (W m-2) 1 W = 1 J s-1 1 W m-2 = 0.0864 MJ m-2 day-1

## Physical properties

### Properties of Water

 T rw l °C Mg m-3 kJ mol-1 0 0.99987 45.0 4 1.00000 44.8 10 0.99973 44.6 20 0.99823 44.1 30 0.99568 43.7 40 0.99225 43.4

T = temperature, rw = density of water and l = latent heat of vaporization

### Properties of gases at Pb = 101.3 kPa barometric pressure

 T r °C mol m-3 0 44.6 5 43.8 10 43.0 15 42.3 20 41.6 25 40.9 30 40.2 35 39.5 40 38.9

T= temperature and r = density

### Black body emittance (W m-2) as a function of subzero temperature (°C)

 °C 0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 -0.7 -0.8 -0.9 -14 256 255 255 255 254 254 253 253 253 252 -13 260 259 259 258 258 258 257 257 257 256 -12 264 263 263 262 262 262 261 261 260 260 -11 268 267 267 267 266 266 265 265 265 264 -10 272 271 271 271 270 270 269 269 269 268 -9 276 276 275 275 274 274 274 273 273 272 -8 280 280 279 279 279 278 278 277 277 276 -7 284 284 284 283 283 282 282 282 281 281 -6 289 288 288 287 287 287 286 286 285 285 -5 293 293 292 292 291 291 291 290 290 289 -4 298 297 297 296 296 295 295 294 294 294 -3 302 302 301 301 300 300 299 299 298 298 -2 306 306 306 305 305 304 304 303 303 302 -1 311 311 310 310 309 309 308 308 307 307 0 316 315 315 314 314 313 313 312 312 311