Presented by

Poovanna Thimmaiah

Co-authors

Wendell Huttema and Majid Bahrami (PI)

International Sorption Heat Pump Conference

ISHPC2017

Tokyo, Japan

August 08th, 2017

2

Introduction

LAEC

SIMON FRASER UNIVERSITY

Sustainable Water,

Greenhouse Crops &

A/C

Laboratory of Alternative Energy Conversion (LAEC),

Canada

Projects at LAEC

Natural Sciences and Engineering Research Council of Canada (NSERC)

The Canadian Queen Elizabeth Advanced Scholarship (QES-AS) Program

3

Reducing Greenhouse Gases

[1] U.S. Energy Information Administration (EIA)

CFC

HCFC

HFC

• Montreal Protocol, 1989

• Still specified as GHG under Kyoto protocol

Water Use water

as refrigerant

Utilize low grade waste heat

Evaporation at sub-atmospheric

low-pressures

Paris Agreement, 2016 <2°C above pre-industrial levels

4

Low Pressure Evaporation

0.14 PSI/ 1 kPa

5oC

13oC

Vacuum chamber

5 cm

-300

-250

-200

-150

-100

-50

0

0 5 10 15 20 25 30 35

Z (

mm

)

Tsat (oC)

Effective low pressure evaporation is a challenge

Thus, water static pressure should be minimized inside the low operating pressure evaporators

The cooling power reduces drastically

5

Available solutions

• Falling film evaporation

Side view Front view

Limitations:

Equal distribution of refrigerant

Internal pump (active pumping)

Complex

Higher weight

Capillary water

Pooled water

Fins

Advantages:

Uniform evaporation rate along

the circumference of the tube

No parasitic energy consumption

Lower weight

No complexity

6

Previous studies

Dr. Schnabel Fraunhofer Institute for Solar Energy Systems ISE , Germany

Dr. Wang Shanghai Jiao Tong University of China

Uncoated plain Coated plain

Uncoated finned Coated finned

Dr. André Bardow RWTH Aachen University, Germany

7

Tested tubes and fin structures

Industrial partners

Wolverine Tube Inc., USA

Wieland Thermal Solutions., Germany

Plain tube

Turbo Chil 26 FPI (Wolverine Tube Inc.)

Turbo Chil- 40 FPI (Wolverine Tube Inc.)

Turbo ELP (Wolverine Tube Inc.)

Turbo CLF 40 FPI (Wolverine Tube Inc.)

GEWA-KS 40 FPI (Wieland Thermal Solutions)

Confidential-NDA (Wieland Thermal Solutions)

OD: 3/4″ (19 mm)

8

Low pressure evaporator experimental setup

TCS

To

Ti

T1

T1T

F

T

Camera & LED

P

Makeup water Control

valve Vacuum pump

Cold trap dry ice and IPA, -78°C

Temperature Control System

Href

9

Low pressure evaporator experimental setup

Evaporator

Chilled water inlet

Chilled water outlet

Makeup water

Flow meter

Variable speed pump

Cold traps

To vacuum pump

10

Low pressure evaporator experimental setup

Evaporator

Chilled water inlet

Chilled water outlet

Makeup water

Flow meter

Variable speed pump

Cold traps

To vacuum pump

11

Comparison of tested tubes

The main features to be considered are

i) continuous parallel fins

ii) high fin density

200

300

400

500

600

700

800

900

8 10 12 14 16 18 20 22

Evapora

tor

heat tr

anfe

r coeffic

ient, U

evap,

(W/m

2K

)

Chilled water inlet temperature, T chilled, i ( C)

Plain tube surface area, Aevap = 9.22 x 10-2 m2

Plain tube

Turbo CLF-40 FPI

Turbo ELP-42 FPI

Turbo Chil-40 FPI

Turbo Chil-26 FPI

GEWA-KS-40 FPI

2.5 times

12

Performance of finned tubes

0

0.003

0.006

0.009

0.012

0.015

0.018

0.021

0.024

Ext. convectionresistance

Conductiveresistance

Int. convectionresistance

Overall thermalresistance

Th

erm

al re

sis

tan

ce

, [

K/W

]Turbo Chil-40 FPI

Turbo Chil-26 FPI

GEWA KS-40 FPI

Plain tube

Plain tube-

2.7E-05 K/W

Chilled water mass flow rate : 2.5 LPM Chilled water inlet temperature: 15oC

Bottleneck Internal resistance

90%

13

Low pressure evaporator experimental setup

15 mm 40 FPI, 0.6 mm

fin spacing 7.9 mm 26 FPI, 1 mm

fin spacing

14

Thermal spray deposition

Electric heater

Powder feeder

Gas

Nozzle

deposit

Uncoated Coated

15

Porous copper coated evaporator

The porous copper coating from thermal spray deposition technology

SEM images of the porous coatings

Deposition is compatible with the material of evaporator

Substrate (copper fin)

coatings

Scale: 200 µm Scale: 5 µm Scale: 200 µm

16

How porous coatings help?

Water vapor

Water vapor Small liquid menisci in

pores of coating

In region 2, the highest heat transfer and evaporation rate occur.

In an uncoated evaporator, the area of zone 2 is limited

17

Performance of coated evaporator

0

500

1000

1500

2000

650 1200 1750 2300 2850 3400 3950 4500 5050 5600

Ove

rall

he

at tr

an

sfe

r co

effcie

nt

[W/(

m2.K

)]

Time [s]

Uncoated

Coated

The evaporation of the same volume of water is nearly twice as fast as compared to its uncoated counterpart.

18

Comparison between uncoated and coated evaporator

0.0E+00

1.0E-03

2.0E-03

3.0E-03

4.0E-03

5.0E-03

6.0E-03

Uncoated Coated

Overall resistance (K/W)

Uncoated

Coated

Coated

Uncoated

0

200

400

600

800

1000

1200

5 10 15 20 25

Co

olin

g P

ow

er

[W]

Chilled water inlet temperature [oC]

Coated Uncoated

500

1000

1500

2000

2500

5 10 15 20 25

Ove

rall

he

at tr

an

sfe

r co

effic

ien

t [W

/m2•K

]

Chilled water inlet temperature [oC]

Coated Uncoated

30%

2 times

30%

19

A new generation design

Direct Metal Laser

Sintering (DMLS)

And 3D Printing

Following the detailed evaluation of low pressure evaporators, A new micro evaporator is designed and built in the lab

20

Variation of U with water height

21

Variation of U with water height

22

Evaluation of evaporator/condenser

Thermostat

Control valve

Secondary Chamber

T P

P Thermostat

Measurement Chamber

T F

T

T F

T

vacuum pump T

Makeup water

23

Acknowledgements

Natural Sciences and Engineering Research Council of Canada (NSERC)

Dr. Karine Brand, Dr. Achim Gotterbarm, Director Global R&D

Dr. Evraam Gorgy, Director of R&D Mr. Bill Korpi Wolverine Tube, Inc.

The Canadian Queen Elizabeth Advanced Scholarship (QES-AS) Program

24

Thanks for your attention Questions/Comments

Black bear poses next to SFU sign in best advertising photo ever

25

Tevap,2 Tevap,1

Ttube,1

Ttube,2

Tchilled,i

Tchilled,o

Chilled,i

Chilled,o

Tube1,2

evap1,2

o All thermocouples have same reading at the beginning (Equilibrium State)

o Evaporator pressure reduces when the control value is opened and remains constant until evaporator runs out of water

o For all calculations, data were extracted from demarcated region (Steady state)

26

Quantifying the evaporator performance

26

,

1 1 1o finned tube

o o i i

RUA h A h A

External Resistance

External Resistance

Internal Resistance

Internal Resistance

Material Resistance Material Resistance

,o finned tube fin wallR R R

27

Future work

27