fundamentals of engineering supplied-reference handbook - Ventech!

Steam Trap
Junction
Pump
See also THERMODYNAMICS section.
Combustion and Combustion Products
See THERMODYNAMICS section
Energy Storage
Energy storage comes in several forms, including chemical,
electrical, mechanical, and thermal. Thermal storage can
be either hot or cool storage. There are numerous
applications in the HVAC industry where cool storage is
utilized. The cool storage applications include both ice and
chilled water storage. A typical chilled water storage
system can be utilized to defer high electric demand rates,
while taking advantage of cheaper off-peak power. A
typical facility load profile is shown below.
DEMAND POWER, kW
WITH THERMAL STORAGE
∆P on-peak
WITHOUT THERMAL STORAGE
MIDNIGHT 6 AM NOON 6 PM MIDNIGHT
TIME OF DAY
214
MECHANICAL ENGINEERING (continued)
The thermal storage tank is sized to defer most or all of the
chilled water requirements during the electric utility’s peak
demand period, thus reducing electrical demand charges.
The figure above shows a utility demand window of 8
hours (noon to 8 pm), but the actual on-peak period will
vary from utility to utility. The Monthly Demand
Reduction (MDR), in dollars per month, is
MDR =∆Pon- peak R , where
∆ Pon-
peak =
Reduced on-peak power, kW
R = On-peak demand rate, $/kW/month
The MDR is also the difference between the demand charge
without energy storage and that when energy storage is in
operation.
A typical utility rate structure might be four months of peak
demand rates (June – September) and eight months of offpeak
demand rates (October – May). The customer’s utility
obligation will be the sum of the demand charge and the
kWh energy charge.
FLUID MECHANICS AND FLUID MACHINERY
Fluid Statics
See FLUID MECHANICS section.
Incompressible Flow
See FLUID MECHANICS section.
Fluid Machines (Incompressible)
See FLUID MECHANICS section and Performance of
Components above.
Compressible Flow
Mach Number
The local speed of sound in an ideal gas is given by:
c = kRT , where
c ≡ local speed of sound
C
k ≡ ratio of specific heats =
C
R ≡ gas constant
T ≡ absolute temperature
This shows that the acoustic velocity in an ideal gas
depends only on its temperature. The Mach number (Ma)
is the ratio of the fluid velocity to the speed of sound.
V
Ma ≡
c
V
≡ mean fluid velocity
p
v