PREFIXES , CONVERSION ,FACTORS

Prefixes

prefixes--conversion-factors-mbsm-dot-pro

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

-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

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