advanced serpentine heat exchangers a)b) a) baseline b ......1.0 intellectual property (ip)...
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1U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Advanced Serpentine Heat Exchangers
Optimized Thermal Systems, Inc.
Dr. Daniel Bacellar
a) Baseline b) Design I c) Design II
a)
b)
c)
300K 350K
a) Baseline b) Design I c) Design II
a)
b)
c)
300K 350K
2U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Project Summary
Timeline:Start date: 10/2016
Planned end date: 10/2019 (04/2020)
Key Milestones
1. Develop Optimized Fin Geometry; 08/2017
2. Construct Prototype Heat Exchangers; 03/2018
3. Commercialization Plan; 10/2019
Budget:
Total Project $ to Date: $299,366
• DOE: $238,293
• Cost Share: $61,073
Total Project $: 663,397
• DOE: $509,563
• Cost Share: $153,834
Key Partners:
Project Outcome:
Conceptualize serpentine heat exchangersfor HVAC application, aiming for leakage reduction.
Design & Optimize novel “dog-bone” fin concepts that result in equivalent or better performance than current state-of-the-art tube-fin heat exchangers.
Prototype, validate and commercialize.
Optimized Thermal Systems, Inc. (OTS)
Heat Transfer Technologies, LLC (HTT)
United Technologies Research Center
(UTRC)
3U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Challenge
Problem Definition: refrigerant leakage in heat pumps and air conditioners has major
impact, directly and indirectly, on both energy consumption and environment.
Focus of this project: Brazed joints vulnerable locations; prone to leakage_______________________________________________________________________________________________________________________________1 https://www.energy.gov/energysaver/home-cooling-systems/air-conditioning (accessed on: 04/05/18)2 Impacts of Leakage from Refrigerants in Heat Pumps. Report prepared for the U.S. DOE by the London Southbank University, March 2014.3 Kim, W. Braun, J.E. Impacts of Refrigerant Charge on Air Conditioner and Heat Pump Performance. International Refrigeration and Air Conditioning Conference at Purdue,
July 10-15, 2010
Air
Conditioning
6% US electricity1
(U$29B)117M Tons CO2
1
Annual Leakage
Rate:~3.5%2
50 Tons (2018/19)2
(ref. GWPR410A= 2088)
12-19% less charge
13% less cooling
7.5% loss in efficiency3
4U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Objectives
• Eliminate 70%-85% of the joints in one, or both heat exchangers, of a 3-ton
residential AC / heat pump system
• Develop serpentine heat exchangers (SHX) with enhanced “dog-bone” fins resulting
in equivalent, or better performance than current state-of-the-art HX’s
– Overcome surface area reduction
– Reduce / eliminate contact resistance
• Develop a cost-effective
product and manufacturing
means for mass production
a) Baseline b) Design I c) Design II
a)
b)
c)
300K 350K
a) Baseline b) Design I c) Design II
a)
b)
c)
300K 350K
a) b) c)
a) b)
5U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Team
HX / System Design Optimization
(CoilDesigner®, VapCyc® CFD, MOGA)
Performance Tests (wind-tunnel / env. chamber)
Data Analysis / Post-Processing
Decision Making (Technical / Management)
Key Partners
0
0.2
0.4
0.6
0.8
1
Wo
rklo
ad
-N
orm
.
OTS HTT UTRC Brazeway SAPA
Manufacturing solutions
Larger scale manufacturing resources
Market analysis
Product dev. /commercialization
Manufacturing solutions
Small scale prototyping
Brazing / Soldering / Welding
Vendor management / POC
Market analysis
Fin tooling / Serpentines
Fin-tube Assembly
Clad aluminum tube
supplier
Key Vendors
BP01:
Baseline
Numerical Analyses
Benchtop tests BP02:
Numerical Analyses (cont’d)
Design Optimization
HX Sample
Performance / Mechanical tests
BP03:
Full Scale HX
Prototype
System Level
Analysis
Commercializat
ion Plan
BP02: NCTE
6U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Approach Framework
Develop
SHX for
HVAC&R –
Reduce
Leakage
Define
Baseline and
Target
performance
Design
Concepts
Investigation
CFD Analyses
Manufacturing
Solutions
Investigation
HX Selection, Multi-
Physics Analysis;
System
Performance
(VapCyc®)
Tooling Development
Prototyping; Validation
(wind tunnel);
System Performance
Assessment
Commer-
cialization
Plan
Design Optimization
Optimizer
CFD
CoilDesigner®
Activities
(R&D)Key
Output
Key
Output
Short-Term
Outcome
Mid/Long
-Term
Outcome
Automated Parameterization
COMPLETE
CURRENT
FUTU
RE
7U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
R410A Condenser Optimization Results
2.1%
0.6%
4.2%
3.5%
10.4%
Air Frontal Velocity (m/s)
1.085 1.121.025
Ref. Pressure Drop (kPa)
22 4015
Baseline
Design II* (Proof-of-Concept)
Optimum (Fixed Face Area)
Optimum (Fixed Air Flowrate)
8U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Design II Sample 1’x1’ Prototypes
Prototype # # FinsFinned
Length mmFPI Remarks Observation Circuit
HX1 253 320 20.0Re-flare fin
collar
~5% non brazed fins
Conventional
HX2 242 320 19.2Re-flare fin
collar
~5% non brazed fins
Split-Merge
HX3 253 320 20.0Re-flare fin
collar
~5% non brazed fins
Split-Merge
HX4 274 297 21.7 No re-flare<1% non
brazed finsModified
Split-Merge
a) b) c)
Prototypes with manifolds: a) HX1; b) HX2; c) HX3
Equivalent Coils
9U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Split-Merge Connections
Split-Merge
Modified
Split-Merge
_ _
mod_ _
_ mod_ mod_
_ _
orig sm orig sm
sm orig sm
cs sm sm
cs orig sm
b a
a a a
A b
A a
2 Restrictions:
1 contraction,
1 expansionModified SM:
Cross-section Areas:1 Restriction:
single expansion
L
Original Split-Merge (SM):
2a
2b
10U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Hot-Water Performance Tests (Validation Purposes)
Air Inlet Temp. Air Flow Rate Water Inlet Temp. Water Flow Rate
°C cfm °C g/s
16 500, 1000, 1500 50 100, 150, 200
Wind Tunnel # 2
Coil Frame Template
Coil Assembled inWind-Tunnel
Inside view of the Wind-Tunnel
11U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Test Results & Validation
-1.5%
-1.0%
-0.5%
0.0%
0.5%
1.0%
1.5%
#1 #2 #3 #4 #5 #6 #7 #8 #9
En
erg
y B
ala
nce
De
via
tio
n
Test Point
HX1 HX2 HX3 HX4
Equivalent coils (airside)
Split-Merge original and
modified, respectively1air
water
QEB
Q
0
1
2
3
4
5
6
100 150 200
He
at
Lo
ad
(k
W)
Water Flowrate (g/s)
HX1 HX3
1.93%1.33% 0.54%
0
50
100
150
200
250
100 150 200
Air
Pre
ssu
re D
rop
(P
a)
Water Flowrate (g/s)
HX1 HX3
3.51% 3.37% 3.28%
12U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Verification & Validation
20%
20%
5%
5%
3000
3500
4000
4500
5000
5500
6000
3000 3500 4000 4500 5000 5500 6000
Sim
ula
tio
n (
W)
Experimental (W)
HX4
HX1 / HX3
13U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Verification & Validation
0
50
100
150
200
250
0 1.5 3 4.5 6 7.5 9
Air
Pre
ssu
re D
rop
(P
a)
Air Frontal Velocity (Pa)
Exp CFD
0
50
100
150
200
250
0 1.5 3 4.5 6 7.5 9
Air
Pre
ssu
re D
rop
(P
a)
Air Frontal Velocity (Pa)
Exp CFD
HX1
HX430
40
50
60
70
80
90
100
110
0 1.5 3 4.5 6 7.5 9
Eff
ecti
ve H
ea
t Tr
an
sfe
r C
oe
ffic
ien
t (W
/m
².K
)
Air Frontal Velocity (Pa)
Exp HX1 CFD HX1
Exp HX4 CFD HX4
20%
14U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Water-Side Pressure Drop
0
20
40
60
80
100
120
140
50 150 250
Wa
ter
Pre
ssu
re D
rop
(k
Pa
)
Water Flow Rate (g/s)
HX1
HX3
HX4
Out of
sensor’s
range
2x
15U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
FEA Analysis – Max Load Until Yield
F =3.77N F =27.0N
16U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Conclusions
• Optimization suggests max. 2% more capacity or
10% pumping power over baseline
• Fin tooling and brazing used to successfully build 4
prototypes
• Performance tests
– HX1 and HX3 demonstrated good repeatability
– Air pressure drop prediction within 10%
– Model consistently overpredicted thermal performance for
HX3, resulting in more than 30% deviation in heat transfer
coefficient (HTC)
17U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Conclusions (cont’d)
• Performance tests (cont’d)
– HX4 matched model within 5% in capacity, with HTC overpredicted by
10-15%
– Given good pressure drop prediction, numerical issues are less likely
to be the main cause for the deviations found
– Unaccounted thermal resistances play a major role in the deviation
– Non-brazed fins add considerable contact resistance
– Tolerance differences should improve successful brazing joints, thus
reducing considerably the contact resistance
– Original Split-Merge joint added a factor of two in pressure drop,
however the modified version is equivalent to conventional circuiting
• Mechanical tests
– The remaining task in BP02 will be finalized in 04/2019 and 05/2019
coinciding with the end of budget period
– Accurate assessment of number of non-brazed joints
18U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Thank You
Optimized Thermal Systems, Inc.
Dr. Daniel Bacellar
19U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
• Under budget due to reduced need for subcontractors
• Budget reductions have enabled modest changes in prototype approach
for additional development
• No other funding sources
Budget History
BP1: Completed
10/2016 – 08/2017
BP2: To Date
08/2017 – 05/2019
BP3: Planned
05/2019 – 04/2020
DOE Cost-share DOE Cost-share DOE Cost-share
Budget $100,432 $25,297 $253,488 $68,230 $155,643 $60,307
Actual $69,992 $18,825 $168,301 $42,248 - -
Project Budget
20U.S. DEPARTMENT OF ENERGY OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY
Project Plan and Schedule
Project Start: 10/2016
Projected End: 10/2019 (04/2020)
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1.0 Intellectual Property (IP) Management Plan
2.1 Baseline Selection
2.2 Initial Performance Simulations
2.3 Material Simulation and Selection
2.4 Benchtop Testing of Brazing Methods
3.1 Optimization Definition and Manufacturing Considerations
3.2 Develop Optimized Fin Geometry
4.1 Design Fin Tooling
4.2 Construct Prototype Heat Exchangers
5.1 Heat Exchanger Performance Testing
5.2 Mechanical / Cyclic Testing
6.1 Improve Manufacturing Techniques in Preparation for Commercialization
6.2 System Level Integration
6.3 System Level Testing
7.0 Develop Technology to Market Commercialization Plan
Project Schedule
Current/Future Work
Past Work
FY2020
Completed Work
Active Task (in progress work)
Milestone/Deliverable (Originally Planned) use for missed
Milestone/Deliverable (Actual)
FY2017 FY2018 FY2019
NCTE