Glossary
to accompany
Thermodynamics: An Engineering Approach, 5th edition
by Yunus A. Çengel and Michael A. Boles34Octane rating of a fuel is a measure of the engine knock resistance of a fuel.
Open (or direct-contact) feedwater heater is basically a mixing chamber, where the
steam extracted from the turbine mixes with the feedwater exiting the pump. Ideally, the
mixture leaves the heater as a saturated liquid at the heater pressure.
Open system is any arbitrary region in space through which mass and energy can pass
across the boundary.
Orsat gas analyzer is a commonly used device to analyze the composition of
combustion gases. The amounts of carbon dioxide, carbon monoxide, and oxygen are
measured on a percent by volume and are based on a dry analysis.
Osmotic pressure is the pressure difference across a semipermeable membrane that
separates fresh water from the saline water under equilibrium conditions.
Osmotic rise is the vertical distance saline water would rise when separated from the
fresh water by a membrane that is permeable to water molecules alone at equilibrium.
Otto cycle is the ideal cycle for spark-ignition reciprocating engines. It is named after
Nikolaus A. Otto, who built a successful four-stroke engine in 1876 in Germany using the
cycle proposed by Frenchman Beau de Rochas in 1862. The ideal Otto cycle, which
closely resembles the actual operating conditions, utilizes the air-standard assumptions.
It consists of four internally reversible processes:
1-2 Isentropic compression,
2-3 Constant volume heat addition,
3-4 Isentropic expansion,
4-1 Constant volume heat rejection.Overall efficiency (combined efficiency) for a power plant is defined as the ratio of the
net electrical power output to the rate of fuel energy input and is expressed as the product
of the combustion efficiency, thermal efficiency and generator efficiency.
Package icing is the practice of using ice in product packages to remove heat and keep
the products cool during transit by taking advantage of the large latent heat of fusion of
water commonly, but its use is limited to products that are not harmed by contact with ice
and the moisture provided by the ice.
Partial derivative is the change in a function that depends on two (or more) variables,
such as z = z (x, y), when allowing one variable to change while holding the others
constant and observing the change in the function as another variable is held constant.
The variation of z(x, y) with x when y is held constant is called the partial derivative of z
with respect to x.