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, r_w = density of water and l = latent heat of vaporization

Properties of gases at P_b = 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

table of the types of oils suitable for the appropriate refrigeration and liquefied media and compressors for each type of compressor