Independent Research Project

Effectiveness comparison of Double pipe heat exchanger

OBJECTIVE

To Design Double pipe heat exchanger with & without turbulator.

Numerical investigation of Heat exchanger Using Ansys.

To find the temperature effect of Double pipe exchanger and compare the effect with turbulator in the tube at various Reynolds number.

Reynolds number varies from 4000 to 14000 with the difference of 2000.

suggesting maximum effectiveness for appropriate heat exchanger case.

HEAT EXCHANGER:

The heat exchanger is a device in which two fluid streams, one hot & another cold are brought into ‘’ thermal contact ‘’ in order to transfer more heat from the hot fluid stream to the cold.

DOUBLE PIPE HEAT EXCHANGER:

A typical double pipe heat exchanger basically consists of a tube or pipe fixed concentrically inside a larger pipe or tube used for lower flow rate applications (less than 500 kW)

Parameter Design

Parameters	Specifications
Shell Diameter	52 mm
Tube inside Diameter	26 mm
Total length of the pipe	1.2 mm
Tube Thickness	4 mm
Shell side material	Steel
Tube side material	Copper
Shell side working fluid (Inlet)	Hot water
Tube side working fluid (Inlet)	Cold Water
Pitch length of turbulator	130 mm
Thickness of turbulator	1 mm

Design

Plain with Turbulator

comparing flow type efficiency

Counterflow give more efficiency so name selection assign as contour flow condition

Name Selection

Plain with Turbulator

Turbulator

Mesh

Plain

Element Quality statistics

Total number of element- 430659

with Turbulator

Element Quality statistics

Total number of element 309675

Boundary condition

• The energy equation is on
• K-epsilon standard wall function is chosen
• Tube material copper
• Shell material aluminium
• Water on both shell & tube side
• The temperature of hot water at tube inlet= 80c
• The temperature of cold water at shell inlet=36c
• The parameter is on to study for various velocity & temperature outlets
• Re=9000 to 40000 which as been calculated
• Area of shell & tube inlet
• at=(pi/4)*(dt^2);
• µ=0.001003;
• ρ =998.2;
• re=9000:6200:40000;
• v=(µ*re)/(ρ*dt);
• coupled solver.

Parameter input

Monitors

Residuals

Temperature hot outlet

Temperature cold outlet

the above represent the sample monitor for parameter

Contour

Minimum velocity

plain	Turbulator

Temperature

plain	Turbulator

Pressure

Plain	Tube

Overall Heat Transfer co-efficient of wall shell

Plain	Turbulator

Overall Heat Transfer co-efficient of the wall tube

Plain	Turbulator

Maximum Velocity

Plain	Turbulator

Temperature

Plain	Turbulator

Pressure

Plain	Turbulator

Overall Heat Transfer co-efficient of wall shell

Plain	Turbulator

Overall Heat Transfer co-efficient of wall tube

Plain	Turbulator

Turbulator wall

minimum velocity	maximum velocity

heat transfer at turbulator U=4.603 w/m2k at maximum velocity

Calculation

Q heat transfer rate in w

`Q=ṁcpΔT`

`Q_C`=shell side heat transfer (cold)

`Q_h`=tube side heat transfer (hot)

h can found by given below formula w/m2k

`h=Q/(AΔT)`

Where `A=πdl`

Overall Heat Transfer rate U w/m2k can be found by

`U=Q/(AΔT_(LMTD))`

Where

`ΔT_(LMTD)=(ΔT1-ΔT2)/(ln⁡(ΔT1)/(ΔT2))`

`ΔT1=T_(hin) - T_(Cout)`

`ΔT2=T_(hout)-T_(cin)`

Average heat Transfer

`Qa=Qh+Qc/2;`

maximum heat transfer w

`Qm=m*cp*(Thi-Tci)`

Non-dimension parameter as follows

Reynolds number

`Re=(ρvD)/μ`

Nusselt Number

`Nu=(hd)/k`

Prandtl Number

`Pr=(μCp)/k`

Friction Factor

`f=(2ΔPD)/(ρV ̅^2 L)`

Overall Enhancement Ratio

`OER=((Nut)/(Nu))/((ft)/(f))`

effectiveness

`eff=(Qa)/(Qm)`

MATLAB Code

clear all;
close all;
clc;
% six cases
% water shell inlet k
Tci=27+273;
% water tube inlet k
Thi=80+273;
% tube diameter m
dt=0.026;
% length of HE m
L=1.2;
% area of tube m
at=pi*(dt^2)*L;
% property of water
cp=4182;
k=387.6;
mu=0.001003;
rho=998.2;

% reynolds number
re=4000:2000:14000;

% output temperature
r=readtable('output.csv');
r1=readtable('output1.csv')
% Pressure in pascal
    % inlet tube pressure
Pti=table2array(r(1:end,3));
Ptti=table2array(r1(1:end,3));
    % outlet tube pressure atmosperic
Po=101325;


% outlet shell temperature (cold outlet)
Tco=table2array(r(1:end,1));
% outlet shell temperature turbulator (cold outlet)
Tcto=table2array(r1(1:end,1));
% outlet tube temperature (hot outlet)
Tho=table2array(r(1:end,2));
% outlet tube temperature with turbulator (hot outlet)
Thto=table2array(r1(1:end,2));

%% calculations
for i=1:length(re)
% flow calculation    
v(i)=(mu*re(i))/(rho*dt); 
m(i)=(rho*at)*v(i);
% heat transfer shell w
Qc(i)=m(i)*cp*(Tco(i)-Tci);
Qtc(i)=m(i)*cp*(Tcto(i)-Tci);
% heat transfer tube w
Qh(i)=m(i)*cp*(Thi-Tho(i));
Qth(i)=m(i)*cp*(Thi-Thto(i));
% average heat transfer w
Qa(i)=Qh(i)+Qc(i)/2;
Qat(i)=Qth(i)+Qtc(i)/2;

% maximum heat transfer w
Qm(i)=m(i)*cp*(Thi-Tci);

% Lograthamic Mean Temperature Difference
LMTD(i)=((Thi-Tco(i))-(Tho(i)-Tci))/(log((Thi-Tco(i))/(Tho(i)-Tci)));
LMTDt(i)=((Thi-Tcto(i))-(Thto(i)-Tci))/(log((Thi-Tcto(i))/(Thto(i)-Tci)));
% over all heat transfer rate w/m2k
U(i)=Qa(i)/(at*LMTD(i));
% turbulator
Ut(i)=Qat(i)/(at*LMTDt(i));
% heat transfer co-efficient w/m2k
h(i)=Qa(i)/(at*(Thi-Tho(i)));
ht(i)=Qat(i)/(at*(Thi-Thto(i)));
% Nusset number
Nu(i)=h(i)*dt/k;
Nut(i)=ht(i)*dt/k;
% Frictional factor
f(i)=(2*(Po-Pti(i))*dt)/(rho*v(i)^2*L);
ft(i)=(2*(Po-Ptti(i))*dt)/(rho*v(i)^2*L);

% Qh(i)/Qm(i);
% Number of tranfer unit
NTU(i)=U(i)*dt/cp;
NTUt(i)=Ut(i)*dt/cp;

% effectiveness
eff(i)=Qa(i)/Qm(i);
efft(i)=Qat(i)/Qm(i);
% Over all Enhancement Ratio
OER(i)=(Nut(i)/Nu(i))/(ft(i)/ft(i));
end
% prandel number
pr=mu*cp/k;

%% Graph

figure(1)
plot(re,Nu,'b');
hold on
plot(re,Nut,'b*');
title('Reynolds number Vs Nusset Number');
xlabel('Re');
ylabel('Nu');
legend('with out','with');

figure(2)
plot(re,f,'r');
hold on
plot(re,ft,'r--');
title('Reynolds number vs friction factor');
xlabel('Re');
ylabel('f');
legend('with out','with');

figure (3)
plot(re,eff,'m');
hold on
plot(re,efft,'m--');
title('Re vs Effectiveness');
xlabel('reynolds number');
ylabel('Effectiveness');
legend('with out','with');


figure(4)
plot(re,OER);
title('Re vs OER');
xlabel('reynolds number');
ylabel('Over all Enhancement Ratio');

Comparison graph

Reynolds Vs Nusset number

Reynolds number Vs Friction factor

Reynolds number vs Effectiveness

Reynolds number vs Overall Enhancement raatio

Conclusion

• Effectiveness is maximum in Maximum Reynolds number in the plain.
• From the observation this study state the maximum effectiveness is at minimum Re with turbulator.
• the friction factor is lesser at lowe Reynolds number.
• Maximum Heat transfer coefficient in the tube at maximum Reynolds number as h= 4676 w/m^2k but does not evenly increase only at the outlet of the tube.
• Maximum Heat transfer coefficient in the shell at maximum Reynolds number as h= 7.410 w/m^2k but is not evenly increasing at inlet & outlet.

Reference Journals

• https://www.tandfonline.com/doi/abs/10.1080/08916152.2014.915271?scroll=top&needAccess=true&journalCode=ueht20
  • Numerical analysis on a double pipe heat exchanger with twisted tape induced swirl flow on both sides
    • Author Ranjitha , Shaji K
  • https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwi886iU09_pAhXQyDgGHUYABaMQFjAMegQIChAB&url=https%3A%2F%2Fcyberleninka.org%2Farticle%2Fn%2F659169.pdf&usg=AOvVaw3oF7EwRojYjatsELDyHufz

Further Scope

• Our objective use technic to increase the effectiveness
• Adding nano material injected in shell inlet and find the heat transfer effect of Heat exchanger.
• turbulator add with different geometry & pitch finding effect of heat transfer inside Heat exchanger .

Acknowledgement

• Skill Lync team.
• Sarang Iyer for excellent knowledge sharing on Topic on CFD technics in MATLAB & Ansys.
• Pritam Goel, wonderful response & support in Ansys to clear all doubts.
• Bharath Kumar For support to learn Design software (solid works).