Double Pipe - Final Report
ChE 201, Thursday B-4
Andrew Rabeneck, Ross Giglio, Michael Hensler,
Krishna Gnanavel, Kevin Jonovich, David Forcey
2
Table of Contents
Page Number
Nomenclature ...................................................................................................................................3
1.0 Introduction and Background ....................................................................................................4
2.0 Experimental Methodology .......................................................................................................7
3.0 Results ......................................................................................................................................10
4.0 Analysis and Discussion ..........................................................................................................18
5.0 Summary and Conclusion ........................................................................................................21
6.0 References……………………………………………………………………………...…….22
Appendix A-1: Experimental Data ................................................................................................23
Appendix A-2: Example Calculations ...........................................................................................25
3
Nomenclature
Symbol
QEG
MEG
CpEG
ΔTLM
U
A
T1
T9
T2
T11
Qw
Mw
Cpw
ρEG
Ρw
Term
Heat duty of ethylene glycol
mixture
Mass flow rate of ethylene
glycol mixture
Heat capacity of ethylene
glycol mixture
Log mean temperature
difference
Heat transfer coefficient
Heat Transfer Surface Area
Ethylene glycol inlet
temperature to the heating
section
Ethylene glycol outlet
temperature from first
heating section
Ethylene glycol outlet
temperature from second
heating section
Ethylene glycol outlet
temperature from the last
heating section
Heat duty of water
Mass flow rate of water
Heat capacity of water
Density of ethylene glycol
mixture
Density of water
Units and Value (if applicable)
W (J/s)
kg/s
139.48 J/mol*K
K
W/m2K
m2
K or C, as specified
K or C, as specified
K or C, as specified
K or C, as specified
W (J/s)
kg/s
75.268 J/mol*K
1069 kg/ m3
993.1 kg/ m3
4
1.0 Introduction and Background
The transfer of heat between two fluids is an important process in the field of
engineering. A heat exchanger allows thermal energy to be transferred efficiently and
controllably. Double pipe heat exchangers are closed system heat exchangers consisting of
concentric inner and outer pipes. Two fluids of different temperatures travel through the pipes,
and heat is transferred from the hot fluid to the cold fluid without mixing or direct contact.
Double pipe heat exchangers can be used in a wide variety of industries and applications. This
setup is often used when flow rates of reacting fluids are relatively low. Simple metal piping can
be used as the framework for the system. In general, the double pipe heat exchanger is favored in
industrial applications because of its pure simplicity and cost effectiveness. Its disadvantages lie
primarily in its relatively low operation capacity, low thermal efficiencies, and the possible
requirement of a large physical space to build the system. Regardless of the minor variations,
double pipe heat exchangers remain a simple, effective method of achieving heat transfer
between fluids [1]. The system reaches steady state when the rate of change of inlet
temperatures, outlet temperatures, and pressure is approximately zero. Figure 1 shows the basic
setup of a countercurrent double pipe heat exchanger.
Figure 1: Double Pipe Layout (Source: Bengtson)
The outer fluid in the double pipe system can flow either concurrently or countercurrently to the inner fluid. In concurrent, or parallel flow, both fluids travel in the same
direction, while in countercurrent, or counter flow, the fluids flow in opposite directions.
Countercurrent flow is more efficient at transferring energy and has a higher overall heat transfer
coefficient [3]. In concurrent flow, the hot fluid temperature decreases as the cold fluid
temperature increases, which causes a decrease in temperature difference between the two fluids.
5
The decrease in temperature difference causes less heat to be transferred. In countercurrent flow,
the difference in temperature of the fluids across the heat exchanger remains close to constant,
which allows for more heat to be transferred, increasing the efficiency of the system. Figure 2
compares the inlet and outlet temperature of both fluids in concurrent and countercurrent flow
using temperature-position graphs.
Figure 2: Concurrent vs. Countercurrent Flow (Source: Peyman)
The technical objectives of this experiment were to calculate the overall heat transfer
coefficients in both the heating and cooling sections with varying ethylene glycol flow rates,
water flow rates, and steam pressure. The LabVIEW program was used to set the flow rates and
steam pressure and record the temperature of the ethylene glycol as it exited both the heating and
cooling section. Each time the flow rates of the fluids were manipulated, the system remained
untouched until it reached steady state, at which point the exit temperatures of ethylene glycol
and the steam or water (respectively) were measured. First, the ethylene glycol flow rate was
changed, and the steam pressure and water flow rate remained constant as temperatures were
measured. Next, the steam pressure was manipulated while the flow rates were held constant,
and the temperatures were once again recorded. Finally, only the water flow rate was
manipulated as steam pressure and EG flow rate remained constant to calculate the overall heat
6
transfer coefficient for the cooling section. The heat duty of the ethylene glycol was calculated
using the equation
QEG=mEG*Cp*ΔT
(1)
where QEG is the heat duty of the ethylene glycol mixture, mEG is the mass flow rate of the
ethylene glycol, Cp is the heat capacity at constant pressure, and ΔT is the change in temperature
between the ethylene glycol inlet and outlet. Using the heat duty, the overall heat transfer
coefficient was calculated with the equation
U = QEG / (A*ΔTLM)
(2)
where U is the overall heat transfer coefficient, A is the heat transfer surface area, and ΔTLM is
the log mean temperature difference.
7
2.0 Experimental Methodology
2.1 Equipment and Apparatus
Figure 3: Flowchart of the Double Pipe
Figure 3 depicts the layout of the double pipe heat exchanger, a system of eight
horizontal pipes. Each pipe in the series has a length of 2.82 meters. The inner pipe has an inner
diameter of 0.0260 meters and an outer diameter 0.0286 meters. The inner diameter of the outer
pipe in the heating section is 0.0504 meters, and the outer diameter is 0.054 meters. The inner
diameter of the outer pipe in the cooling section is 0.0382 meters, and the outer diameter is
0.0413 meters. A solution consisting of 50% ethylene glycol and 50% water enters through the
inner pipe of the top pipe on its left side, and flows through the double pipe in a snake-like
pattern. After leaving the final pipe, the ethylene glycol is pumped back into the ethylene glycol
storage container, which stores 80 liters of the mixture. The top three pipes in the series contains
steam in the outer pipe to heat the ethylene glycol. The steam enters from the left side of the pipe
and flows to the right. This means in the first and third pipes from the top of the system, the
steam is flowing concurrent with the ethylene glycol stream, while the steam is flowing
8
countercurrent to the ethylene glycol in the second pipe. The bottom five outer pipes consist of
water, which is used to cool the ethylene glycol solution. The water enters through the bottom
pipe on the left side, and moves in a snake-like pattern through the five bottom pipes, so the
water is always countercurrent to the ethylene glycol in the cooling section.
2.2 Experimental Procedures
Technical Objective 1
To begin, a data file recording was started in the LabVIEW program. Then, the ethylene
glycol flow rate was set to 10 liters per minute (LPM); the water flow rate was set to its
maximum value of 20 LPM; and the steam pressure was initially set to approximately 2 volts.
The pressure in psig corresponding to this voltage was recorded, as LabVIEW only allows for
setting the voltage. T1, the ethylene glycol inlet temperature to the heating section, T9, the
exiting temperature of the ethylene glycol from the first heating section, T2, the exiting
temperature of the ethylene glycol from the second heating section, and T11, the ethylene glycol
outlet temperature from the last heating section, were monitored and recorded in LabVIEW.
Once each of these temperatures reached steady-state values, represented by a horizontal line on
the LabVIEW graph, the ethylene glycol flow rate was increased to 20 LPM, while every other
parameter remained constant. T1, T9, T2, and T11 at a flow rate of 20 LPM changed from the
values at a flow rate of 10 LPM. As a result, each of these temperatures had to again reach
steady-state values on the LabVIEW graph before increasing the ethylene glycol flow rate two
more times to 30 LPM and then to 35 LPM.
After the four temperatures at an ethylene glycol flow rate of 35 LPM stabilized, the
steam pressure was varied at the 35 LPM flow rate for ethylene glycol. The first steam pressure
was set at approximately 5 volts. The four heating section temperatures for ethylene glycol
changed and were allowed to reach steady-state values. When these values stabilized, the steam
pressure was increased to about 8 volts. After the four temperatures stabilized, the data file
recording was stopped.
Technical Objective 2
For this technical objective, the ethylene glycol flow rate was set to 30 LPM; the water
flow rate was initially set to 5 LPM; and the steam pressure was set to approximately 2 volts. As
9
in the first technical objective, the pressure in psig corresponding to this voltage was recorded.
The ethylene glycol inlet and outlet temperatures in the cooling section, denoted by T11 and T7
in Figure 3, respectively, as well as T8 and T10 from Figure 3, the water inlet and outlet
temperatures in the cooling section, were monitored in LabVIEW. When each of these
temperatures reached steady-state, the process was repeated at water flow rates of 10 LPM, 15
LPM, and 20 LPM. After the temperatures stabilized at the final water flow rate of 20 LPM, the
data file recording was stopped.
10
3.0 Results
The first technical objective was to analyze the heat duty (Q) and heat transfer coefficient
(U) of all three heating sections. In order to calculate these, the inlet and outlet temperatures of
the ethylene glycol mixture as well as the inlet steam temperature needed to be collected during
the experiment; these values were all obtained when the system reached steady state. Table 1 in
the Appendix A-1 shows the system at steady state at the various EG flow rates and steam
pressures needed to calculate Q and U.
The equation for heat duty for ethylene glycol is
QEG = mEG*Cp*∆T.
(1)
The heat capacity of EG was determined at 56.55°C, the average temperature of the mixture
throughout the experiment. At this temperature, the heat capacity was 139.5 J/mol*K (this was
divided by the molar mass in order to give the units J/kg*K) [4]. The mass flow of the EG
mixture and the difference in temperature from the inlet to the outlet were calculated. The mass
flow rate of the ethylene glycol mixture was calculated using the volumetric flow rate and the
density at the average temperature. The volumetric flow rate varied during the experiment, and
the density at 56.55°C was 1069 kg/m3 [5]. Using these values and Equation (1), QEG was
calculated, and the values are presented in Table 1. For further illustration, QEG versus EG flow
rate is shown graphically in Figure 4 while QEG versus steam pressure is shown in Figure 5. The
steam pressure was originally in volts, but the manual readings were recorded in Table 7 of
Appendix A-1.
Table 1: Heat Duty for Three Heating Sections
Steam Pressure
(psig)
EG Flow Rate
(L/min)
1st Section Heat
Duty (W)
2nd Section Heat
Duty (W)
3rd Section Heat
Duty (W)
1.6
10
6,666.62
5,884.26
5,718.09
1.6
20
11,079.02
9,967.90
9,579.75
1.6
30
13,791.72
12,819.90
12,380.08
1.6
35
15,865.49
14,276.55
13,680.97
4.5
35
17,806.56
15,674.21
14,774.32
8.0
35
19,475.93
16,778.42
16,778.42
11
Figure 4: EG Heat Duty in the Heating Sections v. EG Flow Rate (Steam Pressure 1.6 psig)
Heat Duty for Three Heating Sections
17,500.00
Heat Duty (W)
15,000.00
12,500.00
10,000.00
7,500.00
5,000.00
2,500.00
0.00
10
20
30
35
EG Flow Rate (L/min)
Heating Section 1
Heating Section 2
Heating Section 3
Figure 5: EG Heat Duty in the Heating Sections v. Steam Pressure (EG Flow Rate 35 L/min)
Heat Duty for Three Heating Sections
25,000.00
Heat Duty (W)
20,000.00
15,000.00
10,000.00
5,000.00
0.00
1.6
4.5
8
Steam Pressure (psig)
Heating Section 1
Heating Section 2
Heating Section 3
12
As noted earlier, the equation for the overall heat transfer coefficient for ethylene glycol
is given by
U = QEG/(A*ΔTLM).
(2)
The heat duty for EG values presented in Table 1 were used to calculate U. In addition, the
logarithmic mean temperature difference and the surface area of the inner pipe were needed;
these values are directly related to heat transfer. The surface area was calculated using the basis
that the outer diameter of the inner pipe was 0.0286 m and the length of one section was 2.82
m. The outer diameter of the inner pipe was used because that was where the heat transfer took
place as it was in contact with the heating and cooling agents. Thus, the surface area of one pipe
section was 0.2533 m2. The log mean temperature difference, a logarithmic average of the
temperature differences at each end of the pipe, was calculated separately for each section. The
equation for the logarithmic mean temperature difference is
∆TLM = (∆T2-∆T1)/ln(∆T2/∆T1)
(3)
where
∆T2 = T(steam) - T(EG, in)
(4)
and
∆T1 = T(steam) – T(EG, out).
(5)
Using these values, U was calculated, and the data is presented in Table 2. U versus EG flow rate
is shown in Figure 6 while U versus steam pressure is shown in Figure 7.
13
Table 2: Heat Transfer Coefficient for Three Heating Sections
Steam
Pressure
(psig)
EG
Flow
Rate
(L/min)
1st Section Heat
Transfer
Coefficient (W/m²K)
2nd Section Heat
Transfer
Coefficient (W/m²K)
3rd Section Heat
Transfer
Coefficient (W/m²K)
1.6
10
420.25
442.34
523.28
1.6
20
746.54
785.33
895.84
1.6
30
970.28
1,035.87
1,161.18
1.6
35
1,135.54
1,168.59
1,292.25
4.5
35
1,202.30
1,218.61
1,334.08
8.0
35
1,252.49
1,248.27
1,452.55
Figure 6: EG Heat Transfer Coefficient in the Heating Sections v. EG Flow Rate (Steam
Pressure 1.6 psig)
Heat Duty for Three Heating Sections
17,500.00
Heat Duty (W)
15,000.00
12,500.00
10,000.00
7,500.00
5,000.00
2,500.00
0.00
10
20
30
EG Flow Rate (L/min)
Heating Section 1
Heating Section 2
Heating Section 3
35
14
Figure 7: Heat Transfer Coefficient of EG in the Heating Sections v. Steam Pressure
(EG Flow Rate 35 L/min)
Heat Duty for Three Heating Sections
25,000.00
Heat Duty (W)
20,000.00
15,000.00
10,000.00
5,000.00
0.00
1.6
4.5
8
Steam Pressure (psig)
Heating Section 1
Heating Section 2
Heating Section 3
The second technical objective was to analyze the heat duty (Q) of the EG mixture as
well as the cooling water and heat transfer coefficient (U) of the EG mixture in the cooling
section. The cooling section treated all five pipe sections as one continuous system and the
calculations accounted for this. The inlet temperatures of the EG was the outlet EG temperature
from the last heating section. The inlet and outlet temperatures for the ethylene glycol mixture
and the cooling water at steady state used for calculations are presented in Table 6 found in
Appendix A-1.
The mass flow rate of ethylene glycol was calculated the same way as before using the
volumetric flow rate and the density at the average temperature. However, the volumetric flow
rate of EG was not changed during the second technical objective, so the mass flow rate of EG
stayed constant at 0.535 kg/s. The heat duty for EG was found using Equation (1). The
volumetric flow rate of the countercurrent water stream was varied. In order to calculate the
volumetric flow rate of the cooling water, the density at 37.67°C (the average temperature of
water in this experiment) was found. The density was 993.1 kg/m3 at 37.67°C [6]. The heat
capacity of water varied at different temperatures, but at the average temperature, the heat
capacity of water was 4.178 kJ/kg*K [7]. More specifically, using its molar mass, the heat
15
capacity of water is 75.268 J/mol*K. Therefore, the variables needed to calculate the heat duty
for the cooling water were found and used in the equation
QW = mW*Cpw*∆T
(6)
where QW is the water heat duty, mW is the mass flow rate of water, Cpw is the heat capacity of
water, and ∆T is the change in temperature between the water inlet and outlet. The heat duties of
both the EG mixture and the cooling water are presented in Table 3 below. QEG versus water
flow rate is shown in Figure 8.
Table 3: Heat Duty of Ethylene Glycol Mixture and Water in the Cooling Section
EG Flow Rate (L/min)
Water Flow Rate (L/min)
EG Heat Duty (W)
Water Heat Duty (W)
30
5
-28,748.33
21,593.12
30
10
-31,869.91
38,945.13
30
15
-36,323.98
44,932.89
30
20
-39,557.37
41,468.27
16
Figure 8: Heat Duty of EG in the Cooling Section v. Water Flow Rate (EG Flow Rate 30 L/min)
Heat Duty of EG (Absolute Value) in the Cooling Section
45,000.00
Heat Duty (Q)
40,000.00
35,000.00
30,000.00
25,000.00
20,000.00
15,000.00
10,000.00
5
10
15
20
Water Flow Rate (L/min)
Cooling Section
The equation for the heat transfer coefficient is the same as for the first technical
objective. However, there are differences in calculating the values used in Equation (2). The
first difference is in the surface area of the pipe. The outer diameter of the inner pipe in the
cooling section was again 0.0286 m. The length of each pipe was the same at 2.82 m, but all five
were added together because the experiment assumed one continuous cooling section. Using this
data, the surface area was calculated to be 1.267 m2. Next, the logarithmic mean temperature
difference for the cooling section was calculated. While Equation (3) stays consistent, Equations
(4) and (5) change in the cooling section. In this section of the system, ∆T2 and ∆T1 are
calculated using different inlet and outlet temperatures, where
∆T2 = T(EG, in) - T(water, out)
(7)
and
∆T1 = T(EG, out) - T(water, in).
(8)
Therefore, the logarithmic mean temperature difference varied with the volumetric flow rate of
water. With these values, the heat transfer coefficient was calculated, and these values are
presented in Table 4. U versus water flow rate is shown in in Figure 9.
17
Table 4: Heat Transfer Coefficient for the Cooling Section
EG Flow Rate (L/min) Water Flow Rate (L/min) Heat Transfer Coefficient (W/m K)
2
30
5
-1,008.90
30
10
-1,036.59
30
15
-934.07
30
20
-1,035.43
Figure 9: Heat Transfer Coefficient of EG in the Cooling Section v. Water Flow Rate
(EG Flow Rate 30 L/min)
Heat Transfer Coefficient (W/m²K)
Heat Transfer Coefficient of EG (Absolute Value) in the Cooling
Section
2,000.00
1,800.00
1,600.00
1,400.00
1,200.00
1,000.00
800.00
600.00
400.00
200.00
0.00
5
10
15
20
Water Flow Rate (L/min)
Cooling Section
Sample calculations can be found in Appendix A-2 for any data presented in this section.
18
4.0 Analysis and Discussion
The main variables calculated in this experiment were heat duty (Q) and the heat transfer
coefficient (U). Calculating these variables utilizes the quantitative data that was collected and
transforms them into meaningful trends presented in the tables above. The fundamental goal of
both of the experiment was to calculate the heat duty and the heat transfer coefficients for both
the heating section and the cooling section of the double pipe system at different flow rates and
steam pressures.
The first major component of this experiment involved increasing the ethylene glycol
flow rate while holding the steam pressure constant and examining the heat duty and heat
transfer coefficient in the heating section. It was found that the amount of heat that was
transferred increased as the flow rate of the ethylene glycol increased. For example, with a
steam pressure constant at 1.6 psig, the heat duty increased from 6667 W at an ethylene glycol
flow rate of 10 L/min to 11079 W at 20 L/min, and 15865 W at 35 L/min. This trend is shown in
Figure 4 and Figure 6 as well with each heating section heat duty and heat transfer coefficient
showing increasing activity.
The next major component of this experiment involved investigating the effect of
changing the pressure of the steam while keeping the flow rate of the ethylene glycol constant.
As the steam pressure was increased, the heat duty also increased. As seen in Table 1, keeping
the ethylene glycol flow rate constant at 35 L/min, the heat duty increased from 15865 W at 1.6
psig to 19476 W at 8.0 psig. It is worth noting that the heat duty increased at a decreasing rate in
this part of the experiment. This trend is shown in Figure 5 and Figure 7 where trends for both
heat duty and heat transfer coefficient show increasing values at increasing steam pressures.
These two trends -- the increase of the heat duty as both the steam pressure and the
volumetric flow are increased -- can be explained by the fact that as the flow rate of the ethylene
glycol or steam is increased, more mass of either steam or ethylene glycol can be in the
exchanger, allowing for greater heat transfer to occur. But as the volumetric flow rate of
ethylene glycol increases, it also causes a decrease in contact time between the fluids. This
ultimately results in decreased temperature changes of the inner ethylene glycol fluid. With an
increased mass flow rate, the quantitative heat duty is increased because mass and heat duty are
related through the relationship described in Equation (1):
QEG = mEG*Cp*∆T
(1)
19
Although the temperature changes (∆T) decrease with the increase of ethylene glycol flow, the
overall quantitative heat transfer increases due to the increase in mass flow rate. These
conclusions are supported by the data in Appendix A1.
After the heat duty was calculated, the heat transfer coefficient was also calculated for the
heating section. The trend in the heat transfer coefficient followed a similar pattern to that of the
heat duty. The heat transfer coefficient increased as both the ethylene glycol flow rate and the
steam pressure increased.
After the heating section was analyzed, the cooling section was also examined. The
central ideas in the cooling section are similar to that of the heating section, except instead of
using steam, the cooling section utilizes liquid water to cool the ethylene glycol. The magnitude
of the heat duty for ethylene glycol and water increased as the water flow rate increased. The
heat duty of ethylene glycol started at -28,748 W for an ethylene glycol flow rate of 30 L/min
and a water flow rate of 5 L/min. When the water flow rate was increased to 20 L/min, the heat
duty for ethylene glycol increased to -39,557 W. At a constant ethylene glycol flow rate of 30
L/min and a water flow rate of 5 L/min, the heat duty for the water started at 21593 W. The heat
duty of water increased to 41,468 W when the water flow rate was changed to 20 L/min. The
magnitude of the heat shows increasing trends, as shown in Figure 8. This increase in the
amount of heat transferred from the ethylene glycol to the cooling water can be explained by the
same ideas utilized in the heating section. As the volumetric flow rate of the water increased, the
mass flow rate of the water also increased. This essentially allowed more mass to be in the
exchanger over a given time and allowed more heat to be exchanged between the ethylene glycol
and the water. Theoretically, the heat duty for the ethylene glycol and the heat duty for the water
should be equivalent. These differences can be explained by the fact that not all of the heat is
being transferred since perfect efficiency is not possible -- some of the heat was lost to the
surrounding environment.
In addition to the heat duty for the cooling section, the heat transfer coefficient was also
calculated. There was no significant upwards or downwards trend in the data for the heat
transfer coefficient. The heat transfer coefficient with the highest magnitude occurred at 10
L/min with a value of -1037 W/(m2K) and the heat transfer coefficient with the lowest magnitude
occurred at 15 L/min with a value of -934. W/(m2K). The remaining data fell between these
20
values with no specific trend. These values are found in Table 4, and the stagnant trend is better
illustrated in Figure 9 of the Results section.
21
5.0 Summary and Conclusions
The purpose behind the double pipe heat exchanger experiment was to study the effects
of flow direction and rate of flow on a fluid of interest that is being heated or cooled by external
fluids. In this experiment, a mixture of 50% Ethylene Glycol and 50% water was analyzed. Two
trials were performed to examine the changes of inlet and outlet temperatures. The first trial
focused on the heating section, while the second session focused on the cooling section.
After steady state was reached for all fluids, recording and variation of flow rates began.
This is the core of the experiment. By varying the flow rates of the liquids and gases involved,
the engineer can tweak the system to produce the desired results.
The first set of data focused on the heating of ethylene glycol. A larger heat transfer
coefficient and heat duty was achieved by either increasing the flow rate of ethylene glycol or
increasing the steam pressure surrounding it. However, the temperature of the EG mix would rise
only with the increasing of the steam pressure. The temperature of the EG mix decreased with
the increasing of EG flow rate, even though a greater heat transfer was shown. This can be
explained through a greater mass flow rate of EG being able to absorb more heat from the steam
with lesser changes in temperature.
The next set of data focused on the cooling of the ethylene glycol mix. The trends found
are similar to those found for the heating section. The heat exchange between fluids increased as
their mass flow rates increased, but a different trend was discovered with the behavior the heat
transfer coefficient. In the cooling section, there was no significant increasing or decreasing in
the value of the heat transfer coefficient as flow rates were varied. This trend may have been
observed partially because of energy loss to the surroundings, as the cooling sections were not
insulated as well as the heating sections. It may also be that this is the correct observed trend for
the cooling section due to the mathematical calculations involving the use of log mean
temperature differences.
22
6.0 References
[1] K. Bartecki, “Transfer function-based analysis of the frequency-domain properties of a
double pipe heat exchanger,” vol. 51, issue 2, July, 2013. [Online serial]. [Accessed Mar.
21, 2016].
[2] H. Bengtson, “Double Pipe Heat Exchanger Design,” Bright Hub Engineering, para. 3,
February 21, 2010. [Online], Available:
http://www.brighthubengineering.com/hvac/64548-double-pipe-heat-exchanger-design/
[Accessed Mar. 21, 2016].
[3] J. Peyman, “Double Pipe Heat Exchanger Design, part 1,” Scope We, para. 3, July 10, 2013.
[Online], Available: http://scopewe.com/double-pipe-heat-exchanger-design-part-1/.
[Accessed Mar. 21, 2016].
[4] “Ethylene Glycol Heat-Transfer Fluid,” The Engineering Toolbox. (2015). [Online].
Available:http://www.engineeringtoolbox.com/ethylene-glycol-d_146.html
[Accessed March 21, 2016]
[5] T. Sun & A.S. Teja, “Density, Viscosity, and Thermal Conductivity of Aqueous Ethylene,
Diethylene, and Triethylene Glycol Mixtures between 290 K and 450 K,” School of
Chemical Engineering, Georgia Institute of Technology. (2003). [Online]. Available:
http://pubs.acs.org/doi/pdf/10.1021/je025610o [Accessed March 21, 2016]
[6] M. Garcia, “Density and Viscosity of Water 0°C-40°C” ASCE. 2008. [Online], Available:
http://ascelibrary.org/doi/pdf/10.1061/9780784408230.ap02 [Accessed March 21, 2016]
[7] “Heat Capacity of Liquid Water from 0°C-1000°C,” Vaxa Software. (2016). [Online].
Available: http://www.vaxasoftware.com/doc_eduen/qui/caloresph2o.pdf
[Accessed March 21, 2016]
23
Appendix A-1: Experimental Data
Table 5: Steady State Data of the Heating Section
Steam
Pressure
(psig)
Steam
Temperature
(°C)
EG
Flow
Rate
(L/min)
1st
Section
Inlet
(°C)
1st
Section
Outlet
(°C)
2nd
Section
Inlet
(°C)
2nd
Section
Outlet
(°C)
3rd
Section
Inlet
(°C)
3rd
Section
Outlet
(°C)
1.6
102.903
10
34.746
45.498
45.498
54.988
54.988
64.210
1.6
101.596
20
38.427
47.361
47.361
55.399
55.399
63.124
1.6
100.508
30
40.482
48.129
48.129
55.008
55.008
61.651
1.6
100.190
35
41.301
48.600
48.600
55.168
55.168
61.462
4.5
106.407
35
43.745
51.937
51.937
59.148
59.148
65.945
8.0
111.770
35
45.792
54.752
54.752
62.471
62.471
69.675
Table 6: Steady State Data for the Continuous Cooling Section
EG Flow Rate
(L/min)
Water Flow Rate
(L/min)
EG Inlet
(°C)
EG Outlet
(°C)
Water Inlet
(°C)
Water Outlet
(°C)
30
5
75.526
60.100
6.446
68.895
30
10
72.713
55.612
6.669
62.992
30
15
67.009
47.518
6.543
49.856
30
20
62.258
41.032
6.287
36.273
Table 7, The Original vs. Manually Read Steam Pressures for Experiment Sessions 1 and 2
LabView Steam Pressure (V)
Actual Steam Pressure (psig)
2
1.6
5
4.5
8
8.0
2 (Second Experiment)
1.75
24
Note: The data exported from LabView includes temperatures when the system has not reached
steady state. The date found in Tables 5 and 6 only show the temperatures of the relevant inlet
and outlet streams at steady state, not data on its way to steady state.
25
Appendix A-2: Example Calculations
Average temperature EG (for looking up density): (45.79 + 67.303)/2 = 56.5465 C = 329.55 K
Average temperature Water (for looking up density): (6.45 + 68.897)/2 = 37.6735 C = 310.67 K
Density Water (@ 37.67 C) = 0.9931 g/cm^3 = 993.1 kg/m^3
Density Ethylene Glycol (mixture) (@ 329.55 K = 56.55 C) = 1069 kg/m^3
Heat Capacity (Cp) Water (@ 37.67 C) = 4.178 kJ/kg*K * 1 kg/1000g * 1000J/kJ * 18.02 g/mol
= 75.268 J/mol*K
Heat Capacity (Cp) Ethylene Glycol (@56.55 C) = 3.48 kJ/kg*K * 1kg/1000g * 1000J/kJ *
40.042 g/mol = 139.48 J/mol*K
Molar Weight of 1:1 EG/Water Mixture = 0.5(62.07) + 0.5(18.02) = 40.042 g/mol
Technical Objective 1
m = V * density
@ 10 L/min
m = 10L/min * 1069 kg/m^3 * 1m^3/1000L * 1min/60sec
= 0.178 kg/sec
EG
EG
A = 2 * pi * Diameter/2 * Length
pi = 3.1415
Diameter = 0.0286 m
Length = 2.82 m
A = 0.2533 m^2
∆Tlm = log mean temperature difference = (∆T2-∆T1)/ln(∆T2/∆T1)
∆T2 = T(steam) - T(EG, in)
∆T1 = T(steam) – T(EG, out)
@ 10 L/min
1. ∆T = 45.498 - 34.746 = 10.752 K
QEG = .178 kg/sec * 1000g/kg * 1/40.042 g/mol * 139.48 J/mol*K * 10.752 K
QEG = 6666.62 W
2.
∆T2 = T16 - T1 = 102.903 - 34.746 = 68.157 K
∆T1 = T16 - T9 = 102.903 - 45.498 = 57.405 K
∆Tlm = (68.157 - 57.405)/ln(68.157/57.405) = 62.627 K
U = 6666.62 J/s * 1/0.2533 m^2 * 1/62.627K = 420.251 W/m²K
Technical Objective 2
m = V * density
5 L/min
m = 5 L/min * 993.1 kg/m^3 * 1m^3/1000L * 1min/60sec
=0.08276 kg/sec
W
W
A = 2 * pi * Diameter/2 * Length
pi = 3.1415
Diameter = 0.0286 m
Length = 2.82 m * 5 pipes = 14.1 m
26
A = 1.267 m^2
∆Tlm = log mean temperature difference = (∆T2-∆T1)/ln(∆T2/∆T1)
∆T2 = T(EG, in) - T(water, out)
∆T1 = T(EG, out) - T(water, in)
@ 5 L/min Water
1. ∆T = T10 - T8 = 68.895 - 6.446 = 62.449 K
QW = 0.08276 kg/sec * 1000g/kg * 1/18.01528 g/mol * 75.268 J/mol*K * 62.449K
QW = 21593.12 W = 21.59312 kW
2.
∆T2 = T11 - T10 = 75.526 - 68.895 = 6.631
∆T1 = T7 - T8 =60.1 - 6.446 = 53.654
∆Tlm = (6.631-53.654)/ln(6.631/53.654) = 22.490K
U = -28748.33 J/s * 1/1.267 m^2 * 1/22.490K = -1008.896 W/m²K