20. CONVERSION FACTORS


Metric and British Units
Metric, British and SI Units


Metric and British Units

 

To obtain

from

multiply by the following

3.281

metres

Feet

0.3048

10.76

square metres

square feet

0.0929

35.32

cubic metres

cubic feet

0.0283

0.22

litres

UK gallons

4.546

0.264

litres

US gallons

3.785

2.205

kilogrammes

pounds

0.454

1.016

metric ton

ton

0.984

0.00142

kilogrammes per square metre

pounds per square inch

703

3.97

kilocalories

British thermal units

0.252

1.341

kiloWatts

horsepower

0.746

0.00156

kilocalories per hour

horsepower

642

0.001163

kilocalories per hour

kiloWatts

860

0.0003307

kilocalories per hour

tons of refrigeration (U. S.)

3.024

Multiply by the above

to convert

to

 

Metric, British and SI Units

The International systems of Units (SI Units) is now widely used and some conversions relating to the above units are given below:

Mass

1 metric ton = 1 tonne = 0.984 tons (UK)

Pressure

1kg/m2 = 1 kgf/m2 1 Kp/m2 = 9.807 Pascal (Pa) = 9.807 Newton/m2 (N/m2)

Energy

1 cal

= 4.187 Joules (J)

1kWh

= 3.6 Megajoules (MJ)

1 Btu

= 1.055 kilojoules (kJ)

Power

1 hp (U.K. or U. S.)

= 0.746 kW

= 0.746 Joules/second (J/s)

1 hp (metric)

= 0.736 kW

= 0.736 J/s

1 Watt (W)

= 1 J/s

 

Heat flow rate

1 kcal/h

= 1. 163 J/s

= 1. 163 W

1 Btu/h

= 0.293 J/s

= 0.293 W

The units of measurement used throughout the text are the conventional metric units supplemented on a few occasions by the British units. However, for the convenience of the readers who are familiar with the new International System of Units, their conversion factors into the conventional units, and vice versa, are given below for all the units that are not identical in the systems and that have been used in the text.

1. SELECTED CONVENTIONAL UNITS

Length

1 metre (m) = 3.28 ft; 1 foot (ft) = 0.305 m

Area

1 square metre (m2) = 10.76 ft2; 1 square foot (ft2) = 0.093 m2

Volume

1 cubic metre (m3)=35.314 ft3; 1 cubic foot (ft3) = 0.028 m3

Weight

1 kilogramme (kg) 2.205 lb; 1 pound (lb) = 0.454 kg

1 tonne (t) = 1000 kg = 2205 1b = 0.984 UK ton = 1.102 short ton

Density

1 kilogramme per cubic metre (kg/m3) = 0.0624 1b/ft3

1 pound per cubic foot (1b/ft3) = 16.03 kg/m3

Velocity

1 metre/second (m/s) = 196.8 ft/min;

1 foot/minute (ft/min) = 0.00508 m/s

Energy (work, heat)

1 kilocalorie (kcal) = 3.968 Btu = 0.001163 kWh

1 British thermal unit = 0.252 kcal = 0.000289 kWh

Power (heat flow rate)

1 horsepower (hp) = 0.7457 kW

1 kilocalorie per hour (kcal/h) = 3.968 Btu/h = 1. 163 W

1 British thermal unit per hour (btu/h) =0.252 kcal/h = 0.2931 W

1 ton of refrigeration = 3024 kcal/h = 288000 Btu/24h

Specific heat capacity, mass basis

1 kilocalorie per kilogramme, degree Celsius (kcal/kg C) = 1 Btu/ lbF = 4.187 kJ/g C

1 British thermal unit per pound, degree Fahrenheit )Btu/lbF 1 kcal/kgC = 4.187 kJ/gC

Heat transfer coefficient:

1 kilocalorie per square metre, hour, degree Celsius (kcal/m2hC) = 0.205 Btu/ft2hF = 1.163 W/m2C

1 British thermal unit per square foot, hour, degree Fahrenheit

(Btu/ft2)h F = 4.882 kcal/m2hC = 5.678 W/m2C

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2. SELECTED INTERNATIONAL SYSTEM UNITS

Energy (work, heat)

1 kilowatt hour (kWh) = 860 kcal = 3412 Btu

Power (heat flow rate)

1 kilowatt (kW) = 1.34 hp

 

1 watt (W) = 0.860 kcal/h = 3.412 Btu/h

Specific heat capacity, mass basis  
  1 joule per gramme degree Celsius (Jg/C) =
  0.239 kcal/kgC = 0.239 Btu/IbF
Heat transfer coefficient  
  1 watt per square metre degree Celsius (W/m2C) =
  0.860 kcal/m2hC = 0.176 Btu/ft2hF