The document describes a proposed heat exchanger design project to recover waste heat from laundry processes. Dirty wash water at 67°C is currently dumped, while clean water is heated to 70°C using an electric water heater. It is proposed to install a heat exchanger to preheat the water and reduce electricity costs. The heat exchanger design must be optimized to maximize annual savings over a 10-year period considering capital costs, operating costs, and a 10% interest rate. Several heat exchanger concepts will be analyzed and the optimal design selected.

1. Heat Exchanger Design
Savings vs Cost on Area of Design
Jorge Casellas, Israel Vélez, Giankarl Bogle, Alberto Chan
ME-4110-23-Design of Thermal Systems
10-24-16

2. ME 5930 – FA12
Problem Definition
2
In a laundry, 67ºC dirty wash water is dumped into the drain, and 70ºC clean water
is required. Presently 15ºC water is heated in an electric hot water heater, and the
electricity cost is given by AEE. The water is required at a rate of 5000 Kg/h, 12
hours per day, 312 days/yr. To conserve energy it is proposed to install a heat
exchanger to preheat the feed to the electric water heater.
The interest rate to amortize the investment over 10 years is 10% per annum. Taxes
and insure are expected to have a fixed cost of $500 per annum plus $50/yr per
square meter of heat exchanger surface. Design the heat exchanger and the
corresponding net annual savings.
HX
Water
Heater
Laundry Used water
flow
Thout= 67°C
T=70°C
Tcout
Thin= 67°C
T1= 15°C
Water Flow
Thout
Used Water

3. ME 5930 – FA12
Technology Assessment
3
• Warren M. Rohsenow, James P. Hartnett, Young I. Cho(1999). Handbook of Heat Transfer.
https://ezproxy.pupr.edu:2089/browse/handbook-of-heat-transfer/c9780070535558ch17
• BCS.(2008).Waste Heat Recovery “[PDF File]”. Retrieved
from http://www1.eere.energy.gov/manufacturing/intensiveprocesses/pdfs/waste_heat_recovery.pdf
• Sources of Green House Emissions.(October 6, 2016). Retrieved from
https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions
• Estimated U.S. Energy Use in 2009. Retrieved from
http://cdn.phys.org/newman/gfx/news/hires/2011/usenergyuse.jpg
• Gillis, J.(March 31,2014).Panel’s Warning on Climate Risk. Retrieved from http://blog.apastyle.org/files/how-
to-cite-something-you-found-on-a-website-in-apa-style---table-1.pdf
• Warrick, J. & Mooney, C.(December 12,2015). 5 things you should know about the historic Paris Climate
Agreement. Retrieved from https://www.washingtonpost.com/news/energy-
environment/wp/2015/12/12/how-the-proposed-landmark-climate-agreement-would-
work/?utm_term=.0a1589177dba
• How much energy is consumed in commercial and residential buildings in the United States.(April 6, 2016).
Retrieved from http://www.eia.gov/tools/faqs/faq.cfm?id=86&t=1
• Incropera, F.P., & DeWitt, D.P.(2002). Fundamentals of Heat and Mass Transfer.(5th. Ed.). Wiley.
• Heat recovery. (2016). Retrieved from https://www.carbontrust.com/resources/guides/energy-
efficiency/heat-recovery
• Solutions to Global Warming in North America.(2011).Retrieved from http://www.climatehotmap.org/global-
warming-solutions/north-america.html

4. ME 5930 – FA12
Technology Assessment
4
ENVIRONMENTAL IMPACT OF ENGINEERING DESIGN
• Global warming is often viewed as problem with no solution due to the constant need of natural
resources which include: petroleum, natural gas, and other types of fuels for the creation of
energy. Therefore as environmentally options various designs have been included in diverse
industries to contribute as a partial solution to this problem.
• A main factor that increases global warming is the use of fossil fuels for combustion. The
increasing rate of CO2 in the environment that we live in affects a large mass of population. The
negative effects of this increasing problems sometimes result in health issues.
• The adaptation of thermal designs, as heat exchangers help reduce, in great percent the energy
that has to be used for a processes in industries that depend on heating fluids, gases for a specific
process.

5. ME 5930 – FA12
Applicable Engineering Principles
5
A heat exchanger is a device that is used for transfer of thermal energy
(enthalpy) between :
• Two or more fluids
• Solid surface and a fluid
• Solid particulates and a fluid
At differing temperatures and in thermal contact, usually without
external heat and work interactions.

6. ME 5930 – FA12
Technology Assessment
6
Design Parameter References
ASTM B395 / B395M-13, Standard Specification for U-Bend Seamless
Copper and Copper Alloy Heat Exchanger and Condenser Tubes, ASTM
International, West Conshohocken, PA, 2013, www.astm.org
Abstract
• This specification establishes the requirements for condenser, evaporator, and heat exchanger U-bends
that are manufactured from seamless copper and copper alloy tube.
• The material of manufacture shall be of such quality and purity that the finished product shall have the
properties and characteristics specified.
• The material shall conform to the chemical composition requirements specified. Tensile test, expansion
test, flattening test, mercrous nitrate test or ammonia vapor test, nondestructive examination,
hydrostatic test, and pneumatic test shall be made to conform to the requirements specified.

7. ME 5930 – FA12 7
Analysis and Synthesis

8. ME 5930 – FA12
Proposed Concepts
8
Heat Exchanger Concepts Analized
• Counter Flow Heat Exchanger
• Parallel Flow
• Cross Flow

9. ME 5930 – FA12
Proposed Concepts
9
Counter flow Heat Exchanger
http://www.heseco.com/hairpin.htm
http://www.brighthubengineering.com/hvac/62410-heat-exchanger-
flow-patterns/
http://italianfoodmaterialsandmachinery.co
m/heat-exchangers-for-the-food-industry/

10. ME 5930 – FA12
Proposed Concepts
10
Parallel Flow Heat Exchanger
http://www.xylemflowcontrol.com/healthcare/filtration
/b1-nanofiltration-modules.htm
http://www.xylemflowcontrol.com/healthcare/filtration/b1
-nanofiltration-modules.htm
http://www.real-world-physics-problems.com/heat-
exchanger.html

11. ME 5930 – FA12
Proposed Concepts
11
Cross Flow
http://www.esru.strath.ac.uk/EandE/Web_sites/12-
13/Domestic_flue_gas/technical-analysis/heat-exchanger-analysis/crossflow-air-
hx.html
http://forums.vwvortex.com/showthread.php?5548504-Trying-out-a-
new-idea-counter-current-air-water-intercooler
http://slideplayer.com/slide/6646121/

12. ME 5930 – FA12
Engineering Analysis
12
Maximum possible heat rate:
Capacity ratio: Overall heat transfer
Coefficient:
Effectiveness of heat exchanger:
Actual heat transfer rate:
Number of transfer units:

13. ME 5930 – FA12
Engineering Analysis
13

14. ME 5930 – FA12
Engineering Analysis
14

15. ME 5930 – FA12
Engineering Analysis
15

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Engineering Analysis
16

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Engineering Analysis
17

18. ME 5930 – FA12
Engineering Analysis
18
Analysis of Heat Exchangers via Interactive Program
In the analysis of a heat exchanger two different design tasks will be
specified. Two methods used in the analysis of heat exchangers are, the
log mean temperature difference (LMTD) and the effectiveness-NTU
method which is best suited for the task that will be performed by the
interactive program. For the analysis the following data is specified.
-The heat exchanger type, configuration and size,
-Fluid mass flow rate,
-Inlet temperatures.
Required:
-The program needs to predict the outlet temperatures effectiveness and
heat transfer rate.

19. ME 5930 – FA12
Engineering Analysis
19

20. ME 5930 – FA12
Engineering Analysis
20
Example
PolitecnicaHeat Transfer 2Proyecto Heat 2proyect
matlabHeatExchangerFinallast.m

21. ME 5930 – FA12
Engineering Analysis
21
Analysis of Heat Exchanger Concepts
PolitecnicaTermalesProyect Thermal DesingDIVERSE HEAT
EXCHANGER CALCULATIONS CHANGE V6 (Autosaved).xlsx

22. ME 5930 – FA12
Engineering Analysis
22
 Line 3COUNTER FLOW
BEST AREA FOR DESIGN COST OF HX MAX SAVINGS 10 YRS SAVINGS
140 SQM 63,300.00$ 1,857,264.01$ 664.3%
COST TO BUY 10YEARS 61,650.00$
PARALLEL FLOW
BEST AREA FOR DESIGN COST OF HX MAX SAVINGS 10 YRS SAVINGS %
17 SQM 1,143,480.0$ 993,353.6$ 86.9%
COST TO BUY 10YEARS 27,550.0$
CROSS FLOW: UNMIXED
BEST AREA FOR DESIGN COST OF HX MAX SAVINGS 10 YRS SAVINGS %
123 SQM 532,788.2$ 1,604,045.4$ 301.1%
COST TO BUY 10YEARS 77,000.0$

23. ME 5930 – FA12
Concept Selection
23
Use Pugh’s Decision Making Process to select best concept).
Pugh's Decision Matrix Tool
ProblemStatement
Choose a wheel configuration for detailed design.
Weighting
Baseline
CounterflowHX
CrossFlow:unmixed
Shell&Tube:singlepass
ParallelFlow
Criteria
LONG TERM SAVINGS (10 YEARS) 15
Datum
4 3 2 1
TOTAL COST OF HEAT EXCHANGER (with reheat) 15 4 3 2 1
COMERCIAL AREA COMODITY 20 2 1 3 4
ENVIRONMENTAL FACTOR 15 4 3 2 1
MANUFACTURING COMODITY 20 4 3 1 2
COST TO BUY 15 3 1 3 4
Engineering Requirement 7
Engineering Requirement 8
Total: 100 345 230 215 225

24. ME 5930 – FA12
Final Design
24
Sollid works partsHeat ExchangerHeat Exchanger.SLDASM
Design Calculations
Area desired for Counter Flow dHX 145
Di 0.03 m
Do 0.08 m
L 576.9372 m
COUNTER FLOW CONCENTRIC HEAT EXCHANGER

25. ME 5930 – FA12
Conclusions
25
• The target of the final project, Thermal Design of a Heat Exchanger, is to design
a proper Heat exchanger, which can proportion a cost effective solution to
recycling the heat that was being dissipated after the laundry processes are
realized.
• The result was successful, in determining the proper design of the heat
exchanger that is most convenient for the needs of the customer.
• The final decisions were taken consciously, including the benefits of the design
to the environmental aspect of the world that we live in.

26. ME 5930 – FA12
Recommendations
26
• To invest in a Heat Exchanger, performance calculations must be
realized, taking account the acquisition capacity of each client.
• Choosing maximum capacity will render maximum benefits economically
and environmentally.
• If maximum capacity is not attainable, the parallel flow heat exchanger is
an alternative for low initial investment capability due to the fact it
renders a lower cost.
• All types of Heat exchangers are beneficial because it will always result
in economical return on the initial investment.

27. ME 5930 – FA12
Alternative Concepts
28
Shell and Tube: Single Pass
http://www.china-
gpe.com/buyingguide_content/Shell_and_tube_heat_exchanger__1274.html
http://www.shell-tube.com/Materials-and-Construction.html
http://www.standard-
xchange.com/Tools/Portfolio/frontend/item.asp?type=9&size=0&lngDisplay=4&jPageNumber=8&s
trMetaTag=