Page 19 - SESSION 1 (Graduation e-BOOK)(3 October 2023)

School of Engineering and The Built Environment
FACULTY OF AGRICULTURE,
ENGINEERING & NATURAL SCIENCES

DOCTOR OF PHILOSOPHY IN
ENGINEERING (MECHANICAL
ENGINEERING)
CANDIDATE: ANGULA Ester

CANDIDATE’S DISSERTATION
MODELLING OF CONVENTIONAL AND
MICROCHANNEL DELUGEABLE TUBE BUNDLE FOR A
DIRECT AIR-COOLED STEAM CONDENSER.
The study was carried out under the supervision of Prof Paul Chisale
(Main Supervisor) from The Copperbelt University, Zambia, and Dr.
Fillemon N. Nangolo (Co-Supervisor) from Namibia University of Science
and Technology.

This study presents the thermal performance modelling of conventional
and microchannel delugeable tube bundle which incorporated into
a second stage of the induced Hybrid (Dry/Wet)) Dephlegmator
(HDWD). Hybrid dry/wet dephlegmator was proposed to replace a
Conventional Dephlegmator (CD) of a direct Air-Cooled Condenser
(ACC) system, coupled to 30 MW steam turbine of a generating
unit. The Conventional Delugeable Tube Bundle (CDTB) thermal
performance was modelled and configured using one- and two-
dimensional models by employing heat and mass transfer approach.
When the tube pitch varied from 25 mm to 38 mm, the DRTB’s heat
transfer rate and air-side pressure drop were in the range of 1.4 to 2
times and 1.3 to 2.2 times that of CDTB, respectively.

The Microchannel Delugeable Tube Bundle (MDTB) thermal
performance was analysed using semi-empirical model, which
comprises of microchannel heat transfer and flow correlations. The
size and geometric parameters of MDTB was equivalent to that of
CDTB, and the only difference was that the MDTB has microchannels
on the steam-sideAt bundle, component and system levels, the MDTB
thermal performance was higher than that of CDTB. However, this
higher performance came at expense of higher steam-side pressure
drop. Furthermore, the thermal performance of HDWD incorporated
with either CDTB or MDTB was compared to that of CD at component
and system levels. At system level, and as the ambient air temperature
increased from 32 to 44 , the heat transfer rate of the CD was
found to be 27 % to 31 % less than that of HDWD incorporated with
either CDTB or MDTB.

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