heat transfer calculation

1. The 9th International Chemical Engineering Congress & Exhibition (IChEC 2015)
Shiraz, Iran, 26-28 December, 2015
Heat transfer investigation in a plate heat exchanger by using
water-based TiO2 nanofluids
Meisam Ansarpour, Ahmad Azari*
, Hamed Mohammaddoost
Department of Chemical Engineering, Faculty of Oil, Gas and Petrochemical Engineering, Persian Gulf
University, Bushehr, Iran
*Azari.ahmad@pgu.ac.ir
Abstract
The prior researches showed enhancement by using various nanofluid in comparison with water or
another base fluid. In this study, we experimentally investigated the enhancement of the overall
heat transfer coefficient in a plate heat exchanger against Reynolds number for water / TiO2
nanofluids. Two different weight fraction of nanofluids were studied. The results clearly explain
that 0.5 %wt nanofluids has significant enhancement at higher Reynolds numbers against water.
Keywords: Heat transfer, plate heat exchanger, TiO2 nanofluids
Introduction
Nanofluids are colloidal suspensions of nanoparticles with range size 1-100 nm in a base fluid
that can be water, oil or other conventional base fluid. Nanotechnology are widely used in
prior studies such as heat transfer, mass transfer, wastewater treatment and etc. [1-3].
Convective heat transfer development has a significant impact on some industry products such
as air conditioner, power generator, chemical products etc. that can enhanced by enhancing
flow thermal conductivity [4]. So many researchers focus on this process and try to enhance
the heat transfer and conductivity coefficient. Choi and Eastman [5] were the first researchers
who did experiment on heat transfer of nanofuids and after them many others investigators
conduct some experiments on the nanofluids heat transfer.
Among the various heat exchangers Plate heat exchangers (PHEs) are one of most useful heat
exchangers due to theirs features in the industries and engineering such as high heat transfer
efficiency, ease of maintenance, compactness, durability etc. but the results depend on
experiment’s condition, flow arrangement, plate configurations etc. [6]. Compactness is a
most useful feature for this type of heat exchangers due to make them energy efficient, cost
effective and adaptable for industrial applications [7].
This study investigate the effect of TiO2 nanofluids in heat transfer phenomena by using PHE
and the enhancement of that in comparison with water will discussed.
Experimentation
In this study nanofluids were prepared by sonication of 25 nm TiO2 nanoparticles in deionized
water for 20 min processes at 40 W and also 75 W power. 0.1 %wt and 0.5 %wt TiO2
nanofluids were prepared in 40 and 75 W processes, respectively. A circulation process
contain the heating section, liquids reservoir and plate heat exchanger were used as shown in

2. The 9th International Chemical Engineering Congress & Exhibition (IChEC 2015)
Shiraz, Iran, 26-28 December, 2015
figure (1). We used hepaco PHE (HP-40 model) and nano particles that purchased from
Neotrino Nanotechnology Company. The nanofluids pumped from their reservoir to PHE and
after that flows to heating section to increase the temperature. In another side of PHE, cooling
water flows from cooling section. Counter current flows used in this study.
PHE and nanoparticle specifications were listed in tables 1 & 2.
Table 1. Parameters for PHE Table 2. TiO2 specifications
Plate length 0.194 m
Plate width 0.08 m
Plate height 0.042 m
Number of plates 15
Thermal Power 20000 Kcal/h
Chemical formula
Average particle size
Density
Thermal Conductivity
Specific Heat
TiO2
25 nm
0.4 g/cc
6 W/m.K
0.69 KJ/Kg.K
Figure 1: schematic diagram of the experimental rig
The overall heat transfer coefficient and properties for nanofluids calculate from following
equations:
U
.∆
1
∆
, , , ,
ln , ,
, ,
2
μ 1 2.5∅ μ 3
ρ ∅ρ 1 ∅ ρ 4

3. The 9th International Chemical Engineering Congress & Exhibition (IChEC 2015)
Shiraz, Iran, 26-28 December, 2015
where A is the total heat transfer area, U is overall heat transfer coefficient (W/m2
.K), is
viscosity and ρ referes to density. Also Q equals to ( Qcold + Qhot ) / 2 and ∅ is volume fraction
for nanofluid. nf, p and f referes to nanofluid, nanoparticle and fluid, respectively.
Re
ρuD
μ
5
Re is Reynolds number and u is velocity (m/s). D (m) is hydraulic diameter that calculate
from the following correlation:
D
4 ∗
6
Results and discussion
It’s common for prior studies to determine heat transfer coeffient, Nusslet number and
pressure drop against velocity or Reynolds number [8, 9]. However, here we calculate overall
heat transfer coeffient and the results were shown in figure (2). In this figure U versus
Reynolds numbers of 0.1 %wt nanofluids ploted. Reynold’s number has about ±1 difference
for water and 0.5 %wt TiO2 nanofluid due to the alteration of density and viscosity by the
addition of nanoarticles according to equations (3) & (4) even at the same velocities for each
fluid. The results showed enhancement in overall heat transfer coefficient for 0.5 %wt
nanofluids at higher Reynolds numbers. However water has higher overall heat transfer
coefficient in comparison with 0.1 %wt nanofluid. The results obviously show that at lower
Re number the use of nanofluids can decrease the overall heat transfer coefficient and at
higher Re number has the higher performance. This may be due to the heat loss from the PHE.
Since the heat loss from the PHE is higher at low Re number with respect to the high Re
number.
Figure 2: Overall heat transfer coefficient versus Re.

4. The 9th International Chemical Engineering Congress & Exhibition (IChEC 2015)
Shiraz, Iran, 26-28 December, 2015
Conclusions
TiO2 nanofluids and deionized water used in this paper to determine overall heat transfer
coefficient in the plate heat exchanger. The nanofluids are in 0.1 and 0.5 %wt water-based.
We expect by addition nanoparticle to water, the overall heat transfer coefficient increases,
but for 0.1 %wt nanofluids, we observed decrease against water. After that for 0.5% wt, at
higher Reyolds numbers, enhancement observed and for lower that, water has higher total heat
transfer coefficient.
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