Helpful Hints, Formulas And Conversion Factors - Xylem Bell & Gossett Hoffman Speciality Series Engineering Data Manual

Helpful Hints,
Formulas and
Conversion
Factors
12
Helpful Hints
Approximating Condensate Loads
Heating Water with Steam
lbs./hr. Condensate = GPM
x Temperature Rise °F.
Heating Fuel Oil with Steam
lbs./hr. Condensate = GPM
x Temperature Rise °F.
Heating Air with Steam Coils
lbs./hr. Condensate = CFM
x Temperature Rise °F.
SHEMA Ratings
Thermostatic traps and F & T traps for low
pressures may be rated in accordance with
the Steam Heating Equipment Manufacturers
Association (SHEMA). SHEMA ratings have a
built-in safety factor.
Formulas
1. Steam heats a liquid indirectly through
a metallic wall.
—Cooking coils, storage tanks, jacketed
—kettles, stills.
Lbs./hr. condensate =
Q x 500 x S x S x (T -T
l g h 2
L
When:
Q = Quantity of liquid being
l
heated in gal/min
S = Specific gravity
g
S = Specific heat
h
L = Latent heat in Btu/lb
500 = Constant for converting
gallons per minute to
pounds per hour.
T = Final temperature
2
T = Initial temperature
1
2. Steam heats air or a gas indirectly
through a metallic wall.
—Plain or finned heating coils,
—unit space heaters.
Lbs./hr. condensate =
Q x D x S x (T -T ) x 60
g h 2 1
L
When:
Q = Quantity of air or gas in ft
g
D = Density in Ib/ft 3
S = Specific heat of gas being heated.
h
T = Initial temp.
1
T = Final temp.
2
L = Latent heat in Btu/lb
60 = Minutes in hour
3. Steam heats a solid or slurry indirectly
2
4
900
4. Steam heats a solid through direct
)
1
Conversion Factors
One Boiler Horsepower = 140 sq. ft. EDR or
33,475 Btu/hr. or 34.5 Ibs./hr. steam at 212° F.
1,000 sq. ft. EDR yields .5 gpm condensate.
To convert sq. ft. EDR to Ibs. of condensate—
divide sq. ft. by 4.
.25 Ibs./hr. condensate = 1 sq. ft. EDR.
One sq. ft. EDR (Steam) = 240 Btu/hr. with
215°F. steam filling radiator and 70°F. air
surrounding radiator.
To convert Btu/hr. to Ibs./hr.—
divide Btu/hr. by 960.
One psi = 2.307 feet water column (cold).
3 /min.
One psi = 2.41 feet water column (hot).
One psi = 2.036 inches mercury.
One inch mercury = 13.6 inches water column.
Size condensate receivers for 1 min. net
storage capacity based on return rate.
Size condensate pumps at 2 to 3 times
condensate return rate.
through a metallic wall.
—Clothing press, cylinder driers, platen
—press.
Lbs./hr. condensate =
970 x (W -W ) + W x (T -T
1 2 1 2 1
L x T
When:
W = Initial weight of product
1
W = Final weight of product
2
T = Initial temp.
1
T = Final temp.
2
L = Latent heat in Btu/lb.
T = Time required for drying (hours).
Note: 970 is the latent heat of vaporization
at atmospheric pressure. It is included
because the drying process requires that
all moisture in the product be evaporated.
contact.
—Sterilizer, autoclave
W x S
Lbs./hr. condensate =
W = Weight of material being
heated in Ibs.
S = Specific heat of material
h
being heated.
T = Initial temp.
1
T = Final temp.
2
L = Latent heat Btu/lb.
T = Time to reach final temp. (hours)
)
x (T -T )
h 2 1
L x T