The document is a lab report from a group of students at the University of California San Diego that analyzes heat transfer in a plate heat exchanger. It includes results from experiments conducted in both steady-state and batch operations. The results showed that in steady-state operations, the overall heat transfer coefficient increased with increasing mass flow rates, while in batch operations the overall heat transfer coefficient decreased as the temperature difference decreased over time.

1. February 3, 2014
University of California, San Diego
Department of NanoEngineering
La Jolla, CA 92093
To Whom It May Concern:
As requested, this “Plate Heat Exchanger” report includes the overall heat transfer coefficient by
varying hot and cold water flow rates in steady­state and batch operations.
We hope this report will satisfy the desired expectations. If you have any questions or concerns,
please contact us.
Sincerely,
Group B­4
Brandon Sanchez Janet Mok
bobbyjoedik@gmail.com janet.mok14@gmail.com
Liliana Busanez Saman Hadavand
lilianabusanez@gmail.com hada4gold@gmail.com
Department of NanoEngineering,
Chemical Engineering
1

2.
Plate Heat Exchangers
Lab 1 Report
Presented to the
University of California, San Diego
Department of Nanoengineering
CENG 176A
3 February 2015
Prepared by:
Group B­4
Lead Author Section
Janet Mok Letter of Transmittal, Abstract, Intro,
Conclusion
Liliana Busanez Theory and Background
Brandon Sanchez Results and Discussion
Saman Hadavand Tech Memo and Presentation
2

3. Abstract
The goal of the experiment was to understand the characteristics and design of a plate
heat exchanger, as well as to evaluate the effects of varying flow rates on the overall heat transfer
coefficient. The steady­state operation involved moving cold water from a source tank to a
receiving tank where the hot water stream exchanges heat with the cold water stream in the
source tank. In the batch operation, the cold water was pumped into the same tank, with constant
stirring, after exchanging heat with the hot water stream. The data and results showed that in the
steady­state operation, the overall heat transfer coefficient increased as the mass flow rates
increased. However, it was seen that in the batch operation, the overall heat transfer coefficient
decreased as the temperature difference decreased.
3

4. Table of Contents
Introduction
pp. 5
Theory Figure 1, Cocurrent Flow
Figure 2. Countercurrent Flow
pp. 6
Methods pp. 9
Results
Figure 3. Measured Flow Rate
Figure 4. LMTD vs. time
pp. 11
Discussion pp. 13
Conclusion pp. 16
References pp. 17
Appendices Table A1. Batch data
Table A2. Steady­state data
Table A3. Calibration Batch
Table A4. Calibration Steady­state
pp. 18
4

5. Introduction
The Plate Heat Exchanger (PHE) Experiment uses common equipment found in heat
exchange processes used in industries such as: power, air conditioning, and biomedical
industries. The earliest development of PHEs was in response to increasingly strict requirements
from foods, particularly dairy products in the late nineteenth century. The very first patent for a
PHE was granted to the german Albrecht Dracke, who proposed in 1878 the cooling of one
liquid by another, with each flowing in a layer on opposite sides of a series of plates¹. The
growing demand for energy conservation, while using sustainable technology and preserving the
environment, has lead to high performance, compact heat exchangers with increased energy
efficiency. The PHE design is decentralized in nature, and benefits include flexible sizing of
various plates to meet batch­processing heat load demands for sustaining hygienic conditions
common in food, and pharmaceutical product processing¹.
The PHE consists of a pack of gasketed corrugated metal plates, pressed together in a
frame, which allows fluid to flow through a series of parallel flow channels and exchange heat
through the thin metal plates³. Plate heat exchangers are used for transferring heat for any
combination of gas, liquid, and two­phase streams. The gaskets prevent leakage to the outside
and directs the fluids as desired⁴. Heat is then transferred from the warm fluid via the dividing
wall to the colder fluid in a pure counter­flow arrangement, which supplements the high
effectiveness of the PHEs.
The importance of the plate heat exchanger can be seen through the various structural
advantages that it has to offer. The plate surface corrugations promotes enhanced heat transfer by
means of promoting swirl or vortex flows and increased effective heat transfer area. The heat
5

6. transfer coefficients obtained are significantly higher than other heat exchangers for comparable
fluid conditions, which leads to a much smaller thermal size¹. Because of their high heat transfer
coefficients and true counter­flow arrangement, PHEs are able to operate under very close
approach temperature conditions which results in up to 90% heat recovery¹. Another advantage
of PHEs is due to the thin channels created between the two adjacent plates, where the volume of
fluid contained in the heat exchanger is small. Therefore, it reacts to the process condition
changes in a rather short time transient and is easier to control¹. Because plates with different
surface patterns can be combined in a single PHE, different multi­pass arrangements can be
configured which enables better optimization of operating conditions¹.
In this experiment, in order to evaluate the overall heat transfer coefficient, we analyzed
different transient heat operating conditions for plate heat exchangers at varying hot and cold
flow rates. The heat exchanger transfer coefficient from batch heat operations, and under
continuous operations was used to evaluate results that can be applied to scale­up calculations as
in industry to transfer thermal energy in between mediums. The Data logging VI was used to run
the experiment, and the flow rates and approach temperature difference were adjusted to set
operating conditions.
Background & Theory
Plate Heat Exchangers (PHE) promote well mixed flows along the plate with high
convective heat transfer coefficients that result from the inter­corrugation flow path. The plates
themselves confine fluid stream within the inter­plate flow channels. This enhances heat transfer
6

7. and the resultant heat transfer coefficient is significantly higher for PHE than the traditional
shell­and tube heat exchangers¹.
The plate­pack in gasketed PHEs is easily disassembled and reassembled. The thin
rectangular sheet metals plates are in between gaskets, assembled in a pack, and bolted in a
frame. Heat is transferred from the hot fluid via the plate wall to the colder fluid in counter flow
arrangement. The advantage of PHE compared to other highly compact exchangers include
thermal flexible sizing of plates, easy cleaning necessary for the food industry as mentioned, and
close approach temperature pure countercurrent­flow operations (~ ) that lead to highC1°
effectiveness of PHEs¹.
For PHE, there are three primary design flow arrangements for hot and cold fluid
arrangements that of parallel­flow, counter­flow, and multi­pass arrangement. Most common, is
cocurrent and countercurrent configurations:
Figure 1:​ Cocurrent Figure 2:​ Countercurrent
Energy moves from hot fluid to a surface by convection, through the wall by thermal
conduction, and then by convection from the surface to the cold fluid. Heat convection is forced
within a heat exchanger and it is the convective transfer that governs its performances₅⁵. The
7

8. overall heat transfer (or rate) equation in heat exchangers is given by the energy balance across
the separating wall:
(1)C (T ) C (T ) AΔTQ = m c c h
out
− T c
in
= m h h h
in
− T c
out
= U LMTD
Q= Rate of heat transfer (duty), U= Overall heat transfer Coefficient, A= cross­sectionalhere,w
Area for heat transfer, = Log Mean Temperature DifferenceTΔ LMTD
The Log Mean Temperature Difference (LMTD) is used to determine the temperature
driving force for ​heat transfer​ in flow systems. LMTD is constant along the length, and used
most notably with heat exchangers.
(2)
, are the bulk temperatures, or thehere, △T T )w 1 = ( h
out
− T c
in
T T )△ 2 = ( h
in
− T c
out
temperature difference for countercurrent as demonstrated in Figure 2.
The overall heat transfer coefficient is determined for steady state and batch operations.
Heat losses or gains of a whole exchanger with the environment can be neglected. The steady
state operation equation to analyze the performance of the heat exchanger is
(3)C dT dx AΔTm c / = U LMTD
Overall Heat Transfer Coefficient can be estimated for different fluids as well as the type
of heat exchanger system involved (PHE). Where the heat transfer coefficient, U, for water to
water heat exchangers, can be a typical transfer coefficient of about 2000 ².W m K][ / 2
8

9. For the Batch Heating balance equations, the heat balance in a well­mixed tank can be
based on the cold side transfer, hot side transfer, heated by an external heat exchanger so the tank
temperature is the cold side inlet, . The process conditions and heat load are varyingT c
in
throughout the batch.
In batch heating, the required duty is a function of the changing batch temperature
as a function of time. where and are result of hot and cold mass flowTΔ LMTD △T 1 △T 2
rates, and differentiation of , in consideration to the batch heat balance. Substituting in batchT c
in
heating, , to Eq.(1), the temperature time derivative cancels out. The equation for batchTΔ LMTD
as a function of time is given by:
(4)n| | ]t− l
T −T (t)h
in
c
in
T −T (0)h
in
c
in = [
(K−1)ω ωc h
m(Kω −ω )h c
The constant, K, is graphed in a semi­log plot, where from the slope K can be determined to
obtain the overall heat transfer coefficient using the following to determine U:
(5)xp( ( ))K = e Cp
UA 1
mc
−
1
mh
Methods
This experiment involved using a plate heat exchanger and the PHE99_MAIN.vi for both
steady­state and batch operations. Three water tanks were used to test the plate heat exchanger in
order to determine the overall heat transfer coefficient. Two cold water tanks were filled with tap
water at about near room temperature. The lengths and widths were measured for both the cold
water tanks as well as the initial water level. Both operations involved cycling hot and cold water
throughout the system until a stable temperature has been reached. The Labview program
9

10. PHE99_MAIN.vi was used to automatically turn on the pumps and record the Hot­in, Cold­in,
Hot­out, and Cold­out temperatures measured by the thermocouples positioned in the pipes.
While the procedure to execute the experiment for each operation was similar, there were some
differences in methods and use of equipment.
For the steady­state operation, two trials were performed by keeping the hot water flow
rate constant while varying the cold water flow rates. The cold water from one tank was moved
to the other in order to produce a steady group of data during a certain time interval, in which
there were minimal temperature fluctuations from a set thermocouple temperature reading. A
“From” tank and a “To” tank were first determined from the two cold water tanks. The valves
from the Cold­out stream and Cold­in stream were opened and closed respectively depending on
the labeled tank. Lastly, the hot and cold flow rate valves were both adjusted to the desired level.
The VI was then run and both hot water and cold water pumps were turned on and the
temperature data was recorded. Once the plate heat exchanger has reached steady­state, the VI
was stopped after 60 seconds of stable data. Between each trial, the water heater had to warm the
tank up to nearly fully hot.
Similar procedures were used for the batch operation, but this operation instead would be
circulating the cold water back into the same tank it was pumped from. Only one cold water tank
would be used whose level of water was not too high or too low. The depth of the water tank
would be recorded and the Cold­out and Cold­in stream valves were adjusted accordingly. The
rest of the procedure was the same as the steady­state operation except there had to be a
motorized consistent stirring in the cold water tank to allow the water temperature to achieve
10

11. equilibrium before passing through the heat exchanger. The flow rates for both hot and cold
water should not be adjusted so that there is as little human input as possible.
Lastly the inline flow meter was calibrated to result in a good calibration curve. Error
could increase with increasing temperatures resulting in an inaccurate reading. A temperature
was established to run the calibration, and the “From tank was set to this particular temperature.
The temperatures of both tanks were recorded as well as the initial water level in the chosen
“To” tank. The cold water pump was switched on for one minute at a certain flow rate, and then
the time elapsed and new water level was then recorded.
After the experiment was finished, the water heater was turned down to the low setting
and the labview program was closed and shut down, accordingly.The data from the steady­state
and batch operations were then used to determine the overall heat transfer coefficient for this
particular plate heat exchanger.
Results
The cold stream flow rate was measured and varied over different time intervals. A
calibration graph was developed as shown in Figure 3. The hot stream was not used for
calibration as it was assumed that information on one of the flow streams would provide
identical information on the other. A slope of 1 on the calibration curve would indicate an ideal
flow meter. A slope of 1.0792 indicates an error in the calculated flow rate of being
approximately 8% higher than the flow rate displayed by the flow meter.
11

12.
Figure 3​: Cold stream calibration for calculated flow rate vs. measured flow rate
Temperature data from the batch operations were used to solve for the log­mean
temperature differences according to Eqn. 2. T​H​
In​
values were averaged over the duration of the
trials due to minor fluctuations in boiler temperature. The negative values of the LMTD’s for the
trials were plotted against time as shown in Figure 4. The slopes of the curves for each trial were
extracted and used to solve for the value of K according to Eqn. 3. These K values were then
used to solve for the overall heat transfer coefficient according to Eqn. 4. These results along
with the parameters used in each equation are displayed in Table A1. The area of the heat
exchanger plate used is .0321 m​2​
. This value is multiplied by 7 to account for the 7 plates in the
heat exchanger. Note that the flow streams were adjusted by 7.92% due to calibration.
12

13.
Figure 4:​ Plots of ­LMTD vs. time for batch trials
Temperature data from the steady state operation was averaged during the duration of the
trials due to minor fluctuations in temperature readings. The overall heat transfer coefficient was
determined by Eqn 1. Because Eqn. U was calculated using both hot and cold stream
information, which gives 2 values of U for each trial. This data along with temperature data is
displayed in Table A2.
Discussion
Data for the overall heat transfer coefficient was produced using flow rates that had not
been calibrated. Upon adjusting the flow rates, it was found that the overall heat transfer
coefficient increased for steady state results and decreased for batch results. These values along
with percent differences are displayed in Table A3 and A4, respectively. Noting that the flow
rate calibration is only correcting error in the flow meter readings of our data, it was found that
calibrating the mass flow rate will increase the value of U. This can be seen by analyzing Eq. 1.
13

14. The area, temperature differences and heat capacities are the same values as before, therefore an
increase in the flow rate can only increase U. Hence, the overall heat transfer coefficient and the
mass flow rate are directly proportional for this system.
The batch results require more analysis due to the solution technique for calculating U.
When utilizing Eqn. 4, the values of the LHS are the same. The RHS has increased flow rates,
therefore the value of K decreases after calibration. When using Eqn. 5, the calculated U value is
smaller. This may be less intuitive than the steady state results because a misleading assumption
may lead one to conclude that increasing flow rates increases the heat transfer rate. The
temperature dynamics of the batch system may account for the results for increased hot and cold
inlet flow rates. A higher hot stream inlet flow rate would increase the cold stream outlet
temperature at a faster rate. This would also increase the cold stream inlet temperature at a faster
rate, which is also flowing faster into the heat exchanger. Because all streams are approaching
steady state temperatures at a faster rate, the overall heat transfer coefficient decreases as the
temperature differences between the hot and cold streams decreases.
The procedure for the flow rate calibration may have introduced error when developing
the calibration. The container used to fill the water from the cold stream hose had approximate
volume measurements and were not completely accurate. Although the volumes were
approximate on the container, our group agreed that measurement of the original water tub
intended for the procedure would introduce more error. This was concluded because the tub is
rounded and warped and doesn’t accurately represent a rectangular prism. Thus, the dimensions
of the tubs would introduce significant error in volume calculations. Calibration of the hot stream
may introduce error if the hot stream equipment contains more fouling due to high temperature
14

15. streams. The thermal energy from the hot streams may loosen and distribute more particles
through the pipes than the cold streams, however it was assumed that the cold and hot stream
equipment was identical.
The results for U for the batch and steady state operations were not precise and ranged
from about 300 to 1900 W/m​2​
K. The largest source of error may be from assuming that U is a
constant and not a function of temperature. This may be detrimental in calculations because
depending on the temperature of the heat exchanger plates, U may be a higher or lower value.
The values of U​c​ and U​H ​for the steady state operation should theoretically be equal
values in a closed system. Sources of error are limited due to the simplicity of the system.
Temperatures read from the thermocouples may have introduced significant error because the
thermocouples were not calibrated with manual thermometer readings of the water tanks. By not
calibrating the thermocouples, temperature differences may actually be higher or lower, and will
definitely affect the values of U. The small amount of data analyzed for the steady state system
may not be enough to accurately represent the heat exchanger dynamics, and more trials would
need to be conducted to get more accurate results.
The batch operation results produced inconsistent U values of 1507, 298, 470 and 755
W/m​2​
K. After taking a look at Table A1 and noting the differences in H​2​O mass for each trial, it
may be concluded that the mass of H​2​O that went through the system had the greatest effect on
calculating U. This can be seen by Eqn. 4, as mass of water in the denominator will affect the
value of K, which will in turn affect the calculation of U in Eqn. 5. More trials would need to be
conducted with more variance in flow rates to extract consistent K values, and hence calculate a
better value of U.
15

16. Conclusion
In conclusion, plate heat exchangers are used throughout a wide range of industries, such
as dairy and other hygienic industries, as well as in sustainable energy conservation and
biomedical industries. The purpose of this experiment was to determine the overall heat transfer
coefficient under both the steady­state and batch operations while varying hot and cold water
flow rates. It was found that for the steady­state operation, the overall heat transfer coefficient
increased with increasing flow rates, which shows that the overall heat transfer coefficient and
the mass flow rates are directly proportional. However for the batch operation, since all the
streams were approaching steady state temperatures at a faster rate, the overall heat transfer
coefficient decreases as the temperature differences between the hot and cold streams decreases.
Furthermore, the flow rate calibration of the plate heat exchanger indicated an 8% discrepancy
between the measured flow rate and the calculated flow rate. This indicates an error in the
calibration of the flow meter.
16

17. References
[1] Wang, L; Bengt, S; Manglik, R.M., Plate Heat Exchangers: Design, Applications and
Performance: Southampton: WIT, 2002.
[2] ​Perry, R. H., Green, D. W. (Eds.): Perry's Chemical Engineers' Handbook, 7th edition,
McGraw­Hill, 1997 , Section 11.
[3] Pinto, M. J.; Gut, J.A.W “A Screening Method For the Optimal Selection Of Plate Heat
Exchanger Configurations” ​Brazilian Journal of Chemical Engineering​ 27 May 2002: 433­439.
Print.
[4] Kakac, Sadik, and Hongtan Liu. ​Heat Exchangers Selection, Rating, and Thermal Design​.
Boca Raton: CRC Press, 2002. Print.
[5] Martinez, I; Heat Exchangers. ​Webserver.dmt​ [Online] ​1995­2015​, pp1­16
http://webserver.dmt.upm.es/~isidoro/bk3/c12/Heat%20exchangers.pdf​ (accesssed January 28,
2015).
17

18. Appendices
Trial T​H​
In​
(K)
T​C​
In​
(K) C​p​ (J/kg
K)
W​c
(kg/s)
W​h
(kg/s)
Mass
H​2​O
(kg)
K U
(W/m​2
K)
1 339.5 301.4 4184 .2045 .2052 27.63 1.0013 1507
2 334.8 293.41 4184 .2454 .0954 15.90 .9027 297.7
3 334.5 302.4 4184 .2045 .2052 8.327 1.0004 470.2
4 332.7 300.3 4184 .1363 .2045 14.76 1.104 755.2
Table A1:​ Batch data for determining overall heat transfer coefficient
Trial T​H​
In
(K)
T​C​
In
(K)
T​H​
Out
(K)
T​C​
Out
(K)
W​c
(kg/s)
W​h
(kg/s)
U​H
(W/m​2​
K)
U​C
(W/m​2​
K)
U
% Diff.
1 327.7 292.
4
317.7 307.3 .1023 .2045 1557 1159 29.3
2 335.9 291.
7
323.0 310.0 .1363 .2045 1568 1761 11.6
Table A2: ​Steady state data for determining overall heat transfer coefficient
Overall Heat Transfer Coefficient (W/m​2​
K)
U​C U​H
Trial Uncalibrated Calibrated Uncalibrated Calibrated
1 1159 1251 1557 1680
2 1761 1900 1568 1692
Table A3:​ Calibrated steady state values of overall heat transfer coefficient
18

19. Overall Heat Transfer Coefficient (W/m​2​
K)
Trial Uncalibrated Calibrated % Difference
1 1556 1507 3.2
2 300.5 297.7 .936
3 474.9 470.3 .973
4 1008 755.2 28.68
Table A4:​ Calibrated batch values of overall heat transfer coefficient
19

20. TO: NanoEngineering Department Faculty
FROM: Brandon Sanchez, Saman Hadavand, Janet Mok, Liliana Busanez
DATE: January 30, 2015
SUBJECT: CVD
We propose to design a Chemical Vapor Deposition (CVD) reactor using the
COMSOL simulation. CVD is a chemical process essential to micro­electronic device
manufacturing. In this experiment we will conduct a simulation of a CVD reactor to understand
the kinetics of silane deposition. To do this, multiple variables will be adjusted including:
temperature, wafer packing density, pressure, inlet velocity, and mole fraction of hydrogen
present in the inlet. We expect to see an increase in the rate of silane deposition as temperature
increases. Furthermore, we believe that an increase in hydrogen mole fraction and inlet velocity
will increase the rate of silane production and thus its deposition in the reactor. If you have any
concerns, please contact Saman Hadavand at (760) 884­9484.
20