thermal analysis of concentric heat exchanger by using

© 2021 JETIR October 2021, Volume 8, Issue 10 www.jetir.org (ISSN-2349-5162)

JETIR2110311 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org d95

Thermal Analysis of Concentric heat Exchanger

by using Titanium Carbide, Titanium Nitrate and

Zinc Oxide Nanofluids 1CH.P.Rudesh , 2G Venkata Surya Narayana

1&2Assistant Professor

1 School of Aeronautics, 2 Lakireddy Balireddy College of Engineering

1 New Delhi, India; 2 Mylavaram, India

Abstract: This paper presents the thermal characteristics of a simple concentric tube heat exchanger with three different

nanofluids. To inspect the heat transfer rate and efficiency three different nanofluids were taken i.e Titanium Carbide (TiC),

Titanium Nitride (TiN) and Zinc Oxide (ZnO). The properties of nanofluids have been teste per ASTM standards and tabulated.

This entire simulation work has been done by using Ansys workbench Multiphysics CAE software. From the results, it was

concluded that ZnO nanofluid showed the highest heat transfer rate and efficiency at given temperature limits. The overall heat

transfer coefficient of ZnO nanofluid was 83.63, 204.94 % higher than TiN and TiC nanofluids.

Keywords: Computational fluid dynamics, Heat transfer, concentric tube heat exchanger, nanofluids

I. INTRODUCTION

The heat exchangers (HE’s) are the thermal equipment which can transfer the heat between two or more fluid streams at

various temperatures while keeping them from blending in with one another. The HE’s also acts as a waste heat recovery device

for many engineering applications. These are rapidly used in different industries such as HVAC, chemical, aerospace and power

plants, process heating etc. for heating, cooling, evaporation and melting applications. The heat transfer in HE's is majorly done

by forced convection and conduction.

Saqheeb et al. [1] did thermal analysis of a double pipe heat exchanger using different solid materials. They disclosed that copper

metal was given the best heat transfer among steel and aluminum. They recommend that copper was the best metal to fabricate

heat exchangers. Mehdi et al. [2] simulated the shell and coil heat exchanger with three different fins on the coil. The V-shaped

configuration had shown maximum heat transfer rate among the circular and without fin configuration. [3] The goal of this article

is to plan a heat exchanger using ANSYS programming, with an internal width of 330mm and an exterior measurement of

350mm for the shell. The inward measurement of the tube is 21.18mm, while the exterior distance across the tube is 25.4mm.

The length of the cylinder is 1500 mm, and it comprises 36 cylinders. [4] This project has a total of five correlation plans. Using

the CFD package ANSYS 14.5, the interaction in addressing reproduction is presenting and latticing the underlying math of a

shell and tube heat exchanger. The heat exchanger has 7 cylinders, is 600mm long, and has a shell width of 90mm. [5] IVENTOR

PROFESSIONAL is used to plan the 3D display of the shell and tube heat exchanger, and ANSYS-FLUENT 14.5 is used to

examine it. The results show that the maximum heat transfer occurs in the circular fins with the water counter baffles, which

provide more opportunities for water to advance for heat transfer in a wavy structure with a large surface area for heat dissipation

for water cooling.[6] Under extreme circumstances, nanofluids such as Titanium Carbide, Titanium Nitride, and Zinc Oxide have

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different volume focuses (0.02,0.04,0.07, and 0.15) with base fluid. The characteristics of the nanofluid with varied volume

divisions are used to get results of the most severe temperature and heat radiation on the heat exchanger. [7] When using water

as the working fluid, the heat transfer characteristics of the OHP have been focused under various fluid filling rates, different

heat loads, and different tendency angles (0° and 90°). In comparison to pure water, Al2O3 nano-liquid as a working liquid

can improve heat-transport capacity. The optimum convergence of Al2O3 nano-liquid is 0.5wt percent and 0.1wt percent,

respectively, while using vertical base heat mode and flat heat mode. [8] The results also revealed that the circular finned heat

exchanger with a viral water speed of 3 m s1 entering the shell and a high temp water speed of 1 m s1 entering the tube had the

highest heat transfer size. Finally, the effects of cut round fins on helical shell and tube heat exchanger efficiency and heat

transmission are determined to be insignificant in comparison to roundabout fins. [9] The copper pipe was inserted into a

Chlorinated Polyvinyl Chloride (CPVC) pipe that served as a shell side tube because to its high warm resistance and low cost.

The results show that the warmth transfer coefficient in the nano-covered surface increased, along with an increase in the high

flow rate, with a 95 percent improvement over exposed copper pipe.

II. MATERIALS AND METHODS

The concentric tube heat exchanger also known as tube-in-tube heat exchanger which consists of two concentric tubes with

two different diameters. The outer boundary of inner tube and inner boundary of outer tube acts as heat transfer medium. The

Outer tube was insulated to prevent heat loss to the atmosphere and the inner tube was allowed to transfer heat. In this work, the

hot fluid (water) was allowed to flow through the inner tube at a constant velocity i.e., 0.5 m/s. The cold fluid (nanofluids) was

allowed to flow through the outer tube. In this case, the hot fluid had lost the heat while cold fluid had gained the heat. The flow

is laminar in nature as it has Reynolds number less than 2300.

The fluids used in this simulation work and their respective thermal properties have listed in Table 1. These are the vital

parameters which have capability to influence the heat transfer rate significantly.

Nano fluid Density

𝜌 (kg/m3)

Specific heat Cp

(J/kg-K)

Thermal conductivity

k (W/m-K)

Viscosity

µ (kg/m-s)

Water 998.5 4187 0.52 1.61 x 10-3

Water-TiC 1587.97 1098.8511 1.04597 1.37 x 10-3

Water-TiN 1744.27 2460.27 1.005 1.37 x 10-3

Water-ZnO 2550.97 2334.98 54.091 1.37 x 10-3

Table 1 Properties of nanofluids

1. Experimental setup

3.1. Problem statement

A tube-in- tube heat exchanger is designed to extract heat from water which is available at 323K. Three different nanofluids

are taken into consideration for this experiment at room temperature (300K). The flow is laminar in nature as it has Reynolds

number less than 2300.

a. Governing equations

This simulation work was carried out by the steady-state, single-phase forced convection heat transfer model. The

governing equations of 3-Dimensional flow have been displayed below. The governing equations are solved by the solver over

a finite computation volume.

𝜕𝜌

𝜕𝑡+ 𝑑𝑖𝑣 (𝜌𝑈) = 0 – (1)




𝜕(𝜌𝑢)

𝜕𝑡+ 𝑑𝑖𝑣 (𝜌𝑢𝑈) = −

𝜕𝑃

𝜕𝑥+ 𝑑𝑖𝑣 (µ 𝑔𝑟𝑎𝑑 𝑢) + 𝑆𝑀𝑥 – (2 a)

𝜕(𝜌𝑣)

𝜕𝑡+ 𝑑𝑖𝑣 (𝜌𝑣𝑈) = −

𝜕𝑃

𝜕𝑦+ 𝑑𝑖𝑣 (µ 𝑔𝑟𝑎𝑑 𝑣) + 𝑆𝑀𝑦 – (2 b)

𝜕(𝜌𝑤)

𝜕𝑡+ 𝑑𝑖𝑣 (𝜌𝑤𝑈) = −

𝜕𝑃

𝜕𝑧+ 𝑑𝑖𝑣 (µ 𝑔𝑟𝑎𝑑 𝑤) + 𝑆𝑀𝑧 – (2 c)

𝜕(𝜌𝑖)

𝜕𝑡 + 𝑑𝑖𝑣 (𝜌𝑖𝑈) = -P div U + div (k grad T) + φ + 𝑆𝑖 – (3)

The equations 1, 2 and 3 are known as continuity, momentum, and energy equations, respectively. Since these are nonlinear

partial differential equations (PDE’s) we cannot solve these equations directly. So, the solver can solve these PDE’s by numerical

techniques after converting these equations to linear form.

b. Geometric Modelling

The geometry model was designed by using Ansys Design modeler. The dimensions of the geometric model are tabulated in

Table 2. All the necessary fluid domains have been created and named as per proposed design. The Fig 1 displays the geometric

model of concentric tube heat exchanger.

Specifications Dimensions(mm)

Length (l) 600

Inner tube diameter (d) 20

Outer tube diameter 40

Shell inlet diameter (D) 20

Table 2 Geometric specification of tube-in-tube HE

Fig 1. Geometric model of concentric tube HE

c. Grid generation

In meshing the fluid domain can be discretized into small control volumes by using finite volume method (FVM). Later, the

governing equations are solved numerically on control volumes. The generation of the grid is one of the important steps in CFD

case study. Because the grid size and shape directly affect the computation accuracy and results are purely dependent on the grid.

The meshing model was displayed in Fig 2. The mesh consists of hexahedral and tetrahedral cells. Inlet and outlet boundaries

have quadrilateral and triangular faces. Near the interference region elevated temperature gradient are expected hence fine mesh

is given.




Fig 2 Grid generation

d. Solving

i. Boundary conditions

The SIMPLE pressure-velocity coupling algorithm has been selected to solve the PDE’s. The boundary conditions are listed in

Table 2 and displayed in Fig 3.

Fig 3 Boundary conditions

Fluids Temperature T (K) Velocity u

(m/s)

Reynolds number

(Re)

Water 300 0.1 1121

TiN nanofluid 323 0.05 1158

TiC nanofluid 323 0.05 1294

ZnO nanofluid 323 0.05 1861

Table 3 Boundary conditions




III. RESULTS AND DISCUSSION

The effect of various nanofluids on tube-in-tube HE’s hot and cold fluid outlet temperature, the amount of heat transfer and

the thermal efficiency of HE was tested numerically using ANSYS FLUENT solver.

a. Observations

After solving the set of PDE’s numerically by iterations the outlet temperatures have been tabulated in Table 4.

Nano

Fluids

Hot water inlet

temperature Thi

K

Hot water outlet

temperature Tho

K

cold water inlet

temperature Tci

K

Cold water outlet

temperature Tco

K

TiC 323 313.9 300 306.6

TiN 323 317 300 305.4

ZiO 323 312.5 300 306.5

Table 4 Experimental observations

Fig 4 (a) Temperature contour of HE with Water-TiC nanofluid




Fig 4 (b) Temperature contour of HE with Water-TiN nanofluid

Fig 4 (c) Temperature contour of HE with Water-Zno nanofluid

b. Total heat transfer (Q)

The total heat transfer (Q) can be calculated using equation 4.

Q = mh x Cp, h x (Th,i -Th,o) = mc x Cc,h x (Tc,i -Tc,o) W – (4)




Fig 5

Total heat transfer plot for different nanofluids

The total tube side heat transfer of concentric tube heat exchanger is 7810.898 W, 3163.45 W and 5547.89 W for TiC,

TiN and ZnO nanofluids respectively. The total shell side heat transfer of concentric tube heat exchanger is 1445.89 W, 2907.06

W and 4889.74 W for TiC, TiN and ZnO nanofluids respectively. The water-ZnO nanofluid is showing the highest heat transfer

among water-TiC and water-TiN.

c. Overall heat transfer coefficient (U)

Q = U. A. (∆T) 𝐿𝐿𝐿𝐿 - (5)

Fig 6 Overall heat transfer coefficient for different nanofluids




The overall heat transfer coefficient can be calculated by energy balance between cold fluid and hot fluid. The overall

heat transfer coefficient of concentric tube heat exchanger is 14018.02 W/㎡.K, 7554.47 W//㎡.K and 12521.41W//㎡.K for TiC,

TiN and ZnO nanofluids respectively. The overall heat transfer coefficient of concentric tube heat exchanger is 4272.10 W/㎡

.K, 6942.27 W/㎡.K and 15442.53 W//㎡.K for TiC, TiN and ZnO nanofluids respectively. The water-ZnO nanofluid is showing

the highest overall heat transfer coefficient among water-TiC and water-TiN.

d. Effectiveness (ε)

ε = 𝑇ℎ𝑖−𝑇ℎ𝑜

𝑇ℎ𝑖− 𝑇𝑐𝑜- (6)

Fig 7 Effectiveness for different nanofluids

The effectiveness values of concentric tube heat exchangers are 0.30, 0.91 and 0.88 for Water-TiC,

Water-TiN and Water-Zno, respectively. The Water-TiN nanofluid has the highest effectiveness value at

given temperature conditions.

IV. REFERENCES

[1] Sk M.Z.M Saqheeb Ali, K Mohan Krishna, D.V.V.S.Bhimesh Reddy, SK R.S.M.Ali. 2015. Thermal

Analysis of Double Pipe Heat Exchanger by Changing the Materials Using CFD. International Journal of

Engineering Trends and Technology (IJETT) – Volume 26 Number 2- August 2015

[2] B. Farajollahi, S.Gh. Etemad, M. Hojjat. 2010. Heat transfer of nanofluids in a shell and tube heat

exchanger. International Journal of Heat and Mass Transfer:53 ;12–17.

[3] Mr.Santosh K Katarki et.at.al. “CFD Analysis of Shell and Tube Heat Exchanger for Heat Transfer

Capabilities”.

[4]. Mohammed Irshad et.at.al.” Design and CFD Analysis of Shell and Tube Heat Exchanger”.




[5]. Rahul Singh et.at.al.” CFD analysys of shell and tube heat exchanger”.

[6].Hema sundar Banka et.at.al.” Thermal Analysis of Shell and Tube Heat Exchanger using

TitaniumCarbide, Titanium Nitride and Zinc Oxide Nanofluids”.

[7]. Shuangfeng WANG et.at.al.” Heat Transport Characteristics of an Oscillating Heat Pipe with Al2O3

Nano-fluid”.

[8]. Mehdi Miansari et.at.al.” Thermal performance of a helical shell and tube heat exchanger without fins,

with circular fins, and with V‑shaped circular fins applying on the coil”.

[9] M.Armstrong.et.at.al.” Experimental investigation on the heat transfer performance analysis in silver

nano-coated double pipe heat exchanger using displacement reaction”.


thermal analysis of concentric heat exchanger by using

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