Heat Transfer Enhancements: Tube Inserts
Heat Transfer Enhancements: Tube Inserts
Heat Transfer Enhancements: Tube Inserts
• Bare Core tube inserts reduce the flow area resulting in higher tube-side velocity.
It can be used to meet minimum velocity requirements and provide equalization of
pressure to solve maldistribution issues, particularly commonly seen in air cooled
heat exchangers.
• MALDISTRIBUTION
At Koch Heat Transfer, we pride ourselves on innovation and discovery. With our
state of the art R&D facility, we are able to turn ideas into reality.
KHT offers an array of tube insert technology that provides tested and proven
enhancement of tube side heat transfer coefficient. This means smaller, more
efficient heat exchangers reducing weight and cost. For existing equipment, this
is the most cost effective way to improve performance.
In this case study, we discuss a few applications and the impact that the various
inserts have on new and existing equipment.
The following graphs represent the impact the tube inserts have on the tube HELI-CORE™
Inserts provide a greater impact on tubeside heat transfer coefficient in the lam- Twisted Tape
Turbulators
inar to transitional flow regime while still providing benefit in the turbulent flow
regime (figure 1). This translates to either increased duty in a fixed exchanger
Plain Round Tube -
size or a smaller, more economical new design. No Inserts
remains the same throughout, only changing nominal tube length and quantity
of exchangers, to better compare the impact. HELI-CORE™
Tube Inserts
Each insert provides a benefit as compared to a plain tube design. The impact
Twisted Tape
each insert has is due to the type of improvement it brings to the tube side Turbulators
heat transfer coefficient. Twisted tape induces a swirl flow, rather than dis-
placing the fluid. The HELI-CORE™ Tube inserts induce a swirl flow while also Plain Round Tube -
No Inserts
displacing fluid to increase velocity. Wire Wrapped Core primarily displaces fluid Laminar Transitional Turburlent
while slightly inducing a swirl flow.
100 1000 10000
Reynolds Number
Hairpin (Table 1)
Base Case (No Inserts) With Twisted Tape With HELI-CORE™ Tube Inserts With Wire Wrapped Core
Cost Base 54% of Base 55% of Base 28% of Base
Number of Shells 4 2 2 1
Size 24-inch diameter shell 24-inch diameter shell 24-inch diameter shell 24-inch diameter shell
Nominal Length 20 Ft 18 Ft 16 Ft 15 Ft
Number of Tubes 559 559 559 559
Total Weight 95,100 lbs. 49,500 lbs. 45,200 lbs. 22,000 lbs.
Tube Side dP 1.2 psig 2.0 psig 4.8 psig 2.8 psig
Base Case (No Inserts) With Twisted Tape With HELI-CORE™ Tube Inserts With Wire Wrapped Core
Overdesign -44% 5% 15% -5%
Pressure Drop 3.0 psig 4.0 psig 4.5 psig 7.0 psig
The existing exchanger was under performing and an insert retrofit was the most economical direction to proceed. Twisted Tape provides
more benefit relative to the wire wrapped core due to the minimal impact on pressure drop and inducing greater swirl flow. The swirl flow
component forces the liquid to stay in contact with the tube wall ensuring constant vaporization.
Although Twisted Tape is a good choice for many cases, some applications require a more rigid and robust design. HELI-CORE™ Tube In-
serts were selected for this application due to their rigid design, durability through maintenance, and improvement in swirl flow.
Summary
Twisted Tape provides a great benefit for vaporizing cases as well as higher velocity / higher viscosity applications. They will usually have
the lowest cost on a per length basis relative to the other inserts.
HELI-CORE™ Tube Inserts combine the swirl flow benefits of Twisted Tape and the rigidity and displacement benefits of the Wire Wrapped
Core. This insert is also ideal in a vaporizing case, as well as higher velocity / higher viscosity applications. An additional advantage of this
insert is the capability to vary thickness and twist pitch that can fit various applications.
Wire Wrapped Core Tube Inserts are primarily intended to be displacement devices that increase the velocity, while also providing a small
swirl profile. They may be ideal with low velocity cases in combination with higher allowable pressure drop.
The cases discussed are only a few of many possibilities of the advantage inserts can provide. Koch Heat Transfer will provide a customized
solution utilizing expertise and experience that best fits the needs.