Work, Power and Energy, on Piping System that's what we want to know today and still with Piping & Fabrication here, and here we go.
Work.
When a body is moved against a resistance, work must be done upon the body. The amount of work done is the product of the force and the distance through which it acts. The unit of work in the English system is the foot-pound, which is the amount of work done by a force of 1 lb acting through a distance of 1 ft. The following symbols are used in this section in defining the interrelation of work, power, and energy:
A = area, in2 or ft2 (mm2 or m2) as noted
F = force, lbf (newton, N)
g = local acceleration of gravity, ft/s2 (9 . 81 m/s2)
gc = conversion constant, ft . lbf/(lbm . s2) [m . kgf/(kgm . s2)]
h = vertical distance, ft (m)
H = enthalpy, Btu (gram . cal)
hp = horsepower (J/s, kW)
kW= kilowatts
KE = kinetic energy, ft . lbf (m . kgf)
PE = potential energy, ft . lbf (m . kgf)
p = pressure, psi (kPa, kg/cm2)
l = distance, ft (m)
T = time, s
v = velocity, ft/s (m/s)
V = volume, ft3 (m3)
w = weight, lb (kg)
W = work, ft . lb (m . kg)
According to the above definition of work, the following expressions may be written to represent work:
If the force is independent of distance, if the process takes place at sea level, if pressure and area are independent of distance, and if pressure is independent of volume, respectively, the above expressions reduce to
where the subscripts 2 and 1 refer to final and initial states, respectively. The above expressions contain no term involving time, since the measure of work is independent of the time interval during which it is performed.
Power.
Power.
Power is the time rate of performing work. The English unit of power is the horsepower, which is defined at 33,000 ft . lb/min or 550 ft . lb/s. Electric power is commonly expressed in watts or kilowatts, 1 kW being equivalent to 1.34 hp and 1 hp to 0.746 kW. The expressions for horsepower corresponding to those given above for work are
Electric power is the product of volts and amperes, i.e.,
The above expression for the determination of electric power is strictly true for direct current and for alternating current with a zero power factor. For the latter case, if the power factor is different from zero, the expression becomes
Energy.
Energy is the capacity for doing work possessed by a system through virtue of work having previously been done upon it. Whenever work has been done upon a system in producing a change in its motion, its position, or its molecular condition, the system has acquired the capacity for doing work. Energy may be that due to motion, termed kinetic energy; that due to position, termed potential energy; or that due to molecular activity or configuration and is manifest as a change in its internal or stored energy. These three forms of energy are mutually convertible. In the English system, the units of energy are the foot-pound and the Btu, which are related by the fact that 1 Btu is equivalent to 778 ft . lb. Some of the more common expressions for energy are as follows:
1. The potential energy of a body of weight w lb mass which has been raised h ft against gravity is PE _ (wg/gc)h.
2. The kinetic energy possessed by a body of weight w lb mass moving at a velocity v ft/s is KE _ wv2/(2gc).
3. If the body of 1, initially at rest, were to fall freely through the distance h, its potential energy would be converted to kinetic energy and it would acquire a velocity v determined as follows:
1. The potential energy of a body of weight w lb mass which has been raised h ft against gravity is PE _ (wg/gc)h.
2. The kinetic energy possessed by a body of weight w lb mass moving at a velocity v ft/s is KE _ wv2/(2gc).
3. If the body of 1, initially at rest, were to fall freely through the distance h, its potential energy would be converted to kinetic energy and it would acquire a velocity v determined as follows:
4. The energy, resulting from its temperature, of a gas in motion is measured by its specific enthalpy h with units of Btu per pound mass. This energy is available for conversion to kinetic energy, as given by
If the initial velocity v1 is negligible, there is obtained
5. Energy is measured in the English system in horsepower-hours, kilowatthours, Btu, and foot-pounds. The relations among these units are as follows:
I think is enough for today from Piping and Fabrication, but don't forget to visit back because there is so many topics here and in the next post we will talk about Heat and Temperature for Pipe, Piping System, etc. Thanks for visiting.
