Inch of water
Inches of wateris a non-SIunit forpressure.It is also given asinches of water gauge(iwgorin.w.g.),inches water column(inch wc,in. WC,"wc,etc. or justwcorWC),inAq,Aq,orinH2O.The units are conventionally used for measurement of certain pressure differentials such as small pressure differences across an orifice, or in apipelineor shaft,[1]or before and after a coil in anHVACunit.
It is defined as the pressure exerted by a column ofwaterof 1inchinheightat defined conditions. At a temperature of 4°C(39.2 °F) pure water has its highest density (1000 kg/m3). At that temperature and assuming thestandard acceleration of gravity,1 inAq is approximately 249.082pascals(0.0361263psi).[2]
Alternative standard in uncommon usage are 60 °F (15,6 °C), or 68 °F (20 °C), and depends on industry standards rather than on international standards.
Feet of wateris an alternative way to specify pressure as height of a water column; it is conventionally equated to 2,989.067 pascals (0.4335275 psi).[3]
InNorth America,air and other industrial gases are often measured in inches of water when at low pressure. This is in contrast toinches of mercuryorpounds per square inch(psi, lbf/in2) for larger pressures. One usage is in the measurement of air ( "wind" ) that supplies apipe organand is referred simply asinches.It is also used innatural gasdistribution for measuring utilization pressure (U.P.,i.e. the residential point of use) which is typically between 6 and 7 inches WC or about 0.25 lbf/in2.
1 inAq ≈ 0.036 lbf/in2,or 27.7 inAq ≈ 1 lbf/in2.
1 inH2O = 249.0889pascals[3] = 2.490889mbarorhectopascals = 2.54cmH2O ≈ 0.002458316atm ≈ 1.868320TorrormmHg ≈ 0.0735559inHg ≈ 0.03612729lbf/in2
See also
[edit]References
[edit]- ^"My pressure gauge is scaled in 'inches' - what does this mean?" http:// npl.co.uk/science-technology/mass-and-force/faqs/
- ^"The International System of Units (SI) – Conversion Factors for General Use"(PDF).2006. p. 12. Archived fromthe original(PDF)on 2017-10-05.Retrieved2017-10-05.
- ^abGuide for the Use of the International System of Units (SI)(PDF).2008. p. 50.