1. Enhancement in Heat Transfer on Nano-
Engineered Horizontal Tubes
Qamar uz Zaman (11-ME-10) Mueen Ahmad (11-ME-19)
Waleed Azhar (11-ME-91) M. Ubaidullah (11-ME-106)
ABSTRACT
Plain, Integral and Pin-Fin copper tubes
were tested for effective & increased heat
transfer. Nano-scaled structures are
imposed on tubes for enhanced heat
transfer. Heat transfer rate comparison is
done on tubes with different geometry as
well as different surface structures.
INTRODUCTION
Condensation is a ubiquitous phase-
change process important in both
emerging & traditional power generation,
thermal management technologies.
Super-hydrophobic nanostructured
surfaces have unique condensation
properties that may enhance heat
transfer by a mechanism driven by
surface tension. The increased droplet
removal rate and reduced size of
departing droplets facilities
improvements over traditional film-wise
& drop-wise.
EXPERIMENTAL SETUP
METHODOLOGY
Experimentation was performed on
horizontal plain tubes at atmospheric
pressure and steam velocity was
maintained at 0.48 m/s at saturated
temperature. Instrumented tube results
were in accordance with the Nusselt
theory for free convection. Nusselt
theory is stated as:
𝑞 = 0.729
𝑔𝜌𝑙(𝜌𝑙−𝜌 𝑣)ℎ 𝑓𝑔 𝑘 𝑙
3
µ 𝑙(𝑇𝑠𝑎𝑡−𝑇𝑠)𝐷
1 4
Δ𝑇
OPEN HOUSE 2015, SESSION 2K11, MECHANICAL ENGINEERING DEPARTMENT
UNIVERSITY OF ENGINEERING & TECHNOLOGY, TAXILA.
RESULTS
CONCLUSIONS
Heat transfer rate is directly proportional
to the surface area of the heat exchanging
surface as seen from the experimental
results. The pin fin tubes have the highest
heat transfer rate. The condensate
retention also increases with the increase
in surface area, but its effect is less
significant. The fluid flooding can be
decreased by super-hydrophobic nano-
structuring, which causes drop-wise
condensation. This can be a huge step in
the field of Heat transfer & can increase
the efficiency of Heat Exchangers up to 30-
35%.
Supervisor: Dr. Hafiz Muhammad Ali
Fig 1: 3D Schematic Diagram of Experimental
Setup
The Nusselt theory was successfully
validated. The results were 7% offset
from the actual Nusselt line as the steam
was approaching with a velocity of
approximately 0.48 ms-1. It has been
observed that with the change of surface
geometry of copper tube, the heat
transfer rate is significantly increased.
The highest heat transfer rate is observed
for pin fin tubes due to increased surface
area. The integral fin tube has lesser heat
transfer rate than pin fin but has higher
heat flux than simple tube.
Fig 8: Nusselt’s Theory Validation
Fig 9: Variation of Heat Flux with
Vapour Side Temperature Difference
Fig 3: Film-wise Condensation on
Plain tube
Fig 2: Different Tube geometries used
Fig 4: Drop-wise Condensation on
Plain tube
Fig 6: Condensate Retention Angle
on Integral Fin Tube
Fig 7: Condensate Retention
Angle on Pin Fin Tube
Fig 5: Super-hydrophobic Condensation on
Plain tube
Pictures Courtesy: Droplet-Enhanced Condensation on
Scalable Super-hydrophobic Nanostructured Surfaces, MIT
Open Articles.
Condensate retention angle on integral fin
tube is found to be less than that of pin fin
tube. Lower retention angle means less
heat transfer rate.