The Use of Air Cooled Heat Exchangers in Mechanical Seal Piping Plans - Snyder
The Use of Air Cooled Heat Exchangers in Mechanical Seal Piping Plans - Snyder
The Use of Air Cooled Heat Exchangers in Mechanical Seal Piping Plans - Snyder
The Use of Air Cooled Heat Exchangers in Mechanical Seal Piping Plans
Kyle Snyder
Staff Engineer
Flowserve Corporation - Seals
Temecula, CA, United States
Kyle R. Snyder is a Staff Engineer in the convection occurs on any geometry as long as a temperature
Flow Solutions Division of Flowserve differential occurs between the fin and ambient air. The
Corporation, in Temecula, California. He gravitational component is that acting normal to the cooling
joined Flowserve in 2011 as an Applied surface. Optimal performance would occur when the plate is
Technical Solutions Engineer supporting vertical however this affects the size and required space of the
mechanical seals in the Texas Gulf Coast exchanger. Fin and cooler orientation may have a special
region. Kyle received his B.S degree in orientation to manage both cooler size and performance. Refer
Mechanical Engineering from Western to the coolers manufacturers’ installation instructions to ensure
New England University and his Master’s optimum performance.
degree in Aerospace Engineering from the University of Forced convection provides a more effective means of heat
California, Los Angeles. removal over natural convection. Air is driven over a bank of
finned tubing typically provided by a fan. The airs high velocity
ABSTRACT over the fins is capable of removing thermal energy at a higher
rate as hot air is continually removed. Performance of a forced
Piping plans provide a formalized approach to enhancing convection exchanger can also be enhanced by the fan design.
the environment of the mechanical seal. One of the most Several variables can be considered when applying a fan
frequent methods of modifying the seal environment is to including increased rotational speed, the number of blades,
reduce the temperature of fluids in the sealing systems. This has blade pitch and shrouding. Unlike natural convection
the effect of increasing viscosity, reducing vapor pressures, and exchangers that may require a specific orientation, forced draft
removing seal generated heat. coolers can be mounted anywhere. The air velocity should be
Not all seal applications have a viable water source to orientated parallel with the fin geometry. This provides high
apply a water cooled exchanger. In place, air cooled exchangers velocity across both surfaces of the fin without obstruction.
provide a low cost, low maintenance solution for mechanical Figure 1 is a shrouded fan that is directing flow parallel to the
seal piping plans. Natural and forced convection coolers can fin orientation for the most efficient cooling.
prove very effective but require several considerations
including material selection and environmental conditions.
Properly selecting and sizing the coolers can contribute to the
success of a mechanical seal.
212
freezing. Wide ambient temperature swings may also cause a 200
large variation in fluid viscosity. The change in viscosity may
affect the seals dynamic lubrication which may contribute to
leakage variation. Ensure the fluid and selected cooler are
correctly applied given the conditions. Copper
Steel
consideration when initially designing the exchanger and later 1 Radial 2.75
evaluating its performance. Together these variables define the Radial Location (inches)
fin efficiency of a specific design. Figure 3. Radial Temperature Profile of an Annular Fin
Composed of Various Materials
Q Exchanger = 500*GPM*Cp*SG*(Tin-Tout)
Figure 7. API Plan 23 Piping Arrangement Figure 9. API Plan 41 Piping Arrangement
A plan 23 continually cools the seal chamber process fluid. A plan 41 is similar to a plan 21 with the exception of a
To isolate the seal, a close clearance bushing is commonly used cyclone separator is utilized upstream of the exchanger. This is
in the box bore to isolate the hot process and the plan 23 loop. applied in applications where solids in the flush may be a
There is minimal fluid exchange between the plan 23 and the concern. The cyclone separator will split the flush flow into two
process fluid because there is minimal pressure differential streams. The dirty stream will be routed back to the suction line
driving flow. Any fluid exchange will be driven by thermal and the clean flush will be cooled through the exchanger back
gradients causing convection and mixing. The exchanger in a to the seal. The split flow will result in a lower flush flow for
plan 23 must remove the seal generated heat and heat soak from the seal and a larger temperature differential across the air
the hot equipment at equilibrium conditions. cooled exchanger.
API 684 4th edition includes a designated section for air API Standard 682, 2004. “Pumps-Shaft Sealing Systems for
coolers. Previously, air coolers were incorporated into various Centrifugal and Rotary Pumps,” Third Edition, American
piping plans in the 3rd edition. The increasing use and Petroleum Institute, Washington, D.C.
application of the air coolers warrants a section dedicated to
their use. The minimum piping requirements for auxiliary Incropera, F., Dewitt, D., Bergman, T., Lavine, A., 2007,
tubing apply to air cooler designs. Specifics for air coolers “Fundamentals of Heat and Mass Transfer,” Sixth Edition,
include the following: John Wiley & Sons, Danvers, MA.