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The airwatt is a valuable measurement of vacuum cleaner motor efficiency because it represents the power carried by the fluid flow (in the case of a typical household vacuum, this fluid is air). The power of the airflow is equal to the product of pressure and volumetric flow rate. Unlike electrical power (measured in watts), which includes ...
The SI unit of power for heating and cooling systems is the watt. Btu per hour (Btu/h) is sometimes used in North America and the United Kingdom - the latter for air conditioning mainly, though "Btu/h" is sometimes abbreviated to just "Btu". [18] MBH—thousands of Btu per hour—is also common. [19] 1 W is approximately 3.412142 Btu/h [20]
Although the concept of U-value (or U-factor) is universal, U-values can be expressed in different units. In most countries, U-value is expressed in SI units, as watts per square metre-kelvin: W/(m 2 ⋅K) In the United States, U-value is expressed as British thermal units (Btu) per hour-square feet-degrees Fahrenheit: Btu/(h⋅ft 2 ⋅°F)
The HSPF is related to the non-dimensional Coefficient of Performance (COP) for a heat pump, which measures the ratio of heat delivered to work done by the compressor. The HSPF can be converted to a seasonally-averaged COP assuming a lossless compressor and no heat loss by multiplying by the heat/energy equivalence factor .29307111 watts per BTU.
For a fluid flowing in a straight circular pipe with a Reynolds number between 10,000 and 120,000 (in the turbulent pipe flow range), when the fluid's Prandtl number is between 0.7 and 120, for a location far from the pipe entrance (more than 10 pipe diameters; more than 50 diameters according to many authors [10]) or other flow disturbances ...
Flux F through a surface, dS is the differential vector area element, n is the unit normal to the surface. Left: No flux passes in the surface, the maximum amount flows normal to the surface.
Compressor characteristic is a mathematical curve that shows the behaviour of a fluid going through a dynamic compressor. It shows changes in fluid pressure, temperature, entropy, flow rate etc.) with the compressor operating at different speeds. A compressor increases the pressure of a fluid passing through it, so that the exit pressure is ...
As can be seen in the formula for maximum theoretical thermal efficiency in an ideal Brayton cycle engine, a high pressure ratio leads to higher thermal efficiency: = where PR is the pressure ratio and gamma the heat capacity ratio of the fluid, 1.4 for air.