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Feasible Working Domains – Decision Support for Heat Pump Projects

Ommen, Torben Schmidt

Publication date:2015

Document VersionPeer reviewed version

Link back to DTU Orbit

Citation (APA):Ommen, T. S. (Author). (2015). Feasible Working Domains – Decision Support for Heat Pump Projects.Sound/Visual production (digital)

https://orbit.dtu.dk/en/publications/49f3a193-52c2-4912-a9a3-9cbbf08e79c1

Feasible Working Domains – Decision Support for Heat Pump Projects

4th International Symposium on Advances in Refrigeration and Heat Pump Technology

November 19th 2015

Torben Ommen

Section of Thermal Energy, Technical University of Denmark

Introduction

Motivation

Potential for energy and economic optimisation in industrial plants and district heating systems by usinglarge scale heat pumps.

� Complex systems: economic optimum depends on both heat pump performance, investment, expectedoperation hours, taxation and fuel cost.

� Pinch- or plant optimisation specialists are not necessarily experts on best available heat pumptechnology, and may thus be assisted by decision support tools.

2 DTU Mechanical Engineering 4th International Symposium on Advances in Refrigeration and Heat Pump Technology 19.11.2015

Introduction

Motivation

Potential for energy and economic optimisation in industrial plants and district heating systems by usinglarge scale heat pumps.

� Complex systems: economic optimum depends on both heat pump performance, investment, expectedoperation hours, taxation and fuel cost.

� Pinch- or plant optimisation specialists are not necessarily experts on best available heat pumptechnology, and may thus be assisted by decision support tools.

Working domains

� Introduced in ”Comparison of the working domains of some compression heat pumps and acompression-absorption heat pump” by Brunin et al. (1997)

� Economic feasibility integrated by including two physical constraints� Technical constraints are similar to operating envelope for individual components

� Technical and economical working domains for single stage industrial heat pumps.� R134a, R290, R600a, R717-LP, R717-HP and R744 in Ommen et al. (2015a)� Ammonia-water hybrid absorption compression HP in Jensen et al. (2015)� R600a and R717-HP in series in Ommen et al. (2015b)


Introduction

Working domains in literature

Max

. p

ress

ure

, ( )

()

Working Domain

(a) Example of working domain with VHC and COP torepresent economic feasibility (Brunin et al., 1997)

, ( )

()

<

, < 0

Max

. p

ress

ure

Working Domain

(b) Example of working domain with economic andtechnical constraints (Ommen et al., 2015a).


Method

Outline for Presentation

• Introduction• Motivation

• Working domains in literature

• Method• Vapour compression heat pump

• Economic assumptions

• Heat exchanger design and calculation

• Influence of key economic assumptions on NPV

• Examples of working domains• Single stage vapour compression HP

• Ammonia-Water Hybrid Compression-Absorption HP

• Vapour compression HPs in series• Vapour compression HPs in series

• COP and NPV

• Comparison with working domain for single stage VCHP

• Further steps• A second economic case

• Two stage VCHP configurations

• Discussion


Method

Vapour compression heat pump

Expansion

valve

Evaporator

Condenser

Tcond

Tevap

Tlift

Gross

Temp.

lift

Compressor

sink

Tsource

Tsink

Tsource

1

2

4

3

(a) Principle sketch of VCHP

0 0.5 1

0

20

40

60

80

100

Relative heat transfer (-)T

(oC)

RefrigerantSink mediaSource media

Temperaturevariation ofsink stream

∆Tpinch

∆Tpinch

Temperaturevariation ofsource stream

∆Tpinch

(b) Temperature - heat load diagram of VCHP


Method

Vapour compression heat pump in finite reservoirs

Typically used operational parameters for heat pump performance:

Type of data Value Unit DesignationEfficiency 0.8 / Compressor isentropic efficiency

0.8 / Compressor volumetric efficiency0.95 / Electric motor efficiency

Temperature 5 K Evaporator superheat5 K Minimum pinch point in heat exchangers


Method

Economic assumptions

� Heat pump load: 1000 (kW)

� Operating time 3500 (h/year)

� Lifetime 15 (years)

� Natural gas burner efficiency 0.9 (-)

� Interest rate of 7 (%)

� Inflation rate of 2 (%)

� NPV and PBT based on gas boiler replacement

� Component investment cost based on Danishprices

� Danish electricity and gas prices were used

� Natural gas burner investment and O&M notconsidered

Correlations for component cost of the type: PECY = PECW

(

XY

XW

)α

:

Component type PECW (e) XW α(−) Source

Compressor R600a 19850 279.8 (m3 h−1) 0.73 trade business 1 2

R717-HP NDA NDA NDA manufacturer 4

Electrical motor R600a 0 0 0 incl. in compressor 1 2

R717-HP 10710 250 (kW) 0.65 trade business 1

Receiver R600a 1444 0.089 (m3) 0.63 trade business 1

R717-HP 1934 0.089 (m3) 0.66 trade business 1

Plate heat exchanger R600a 15526 42 (m2) 0.8 trade business 1 2 3

R717-HP NDA NDA NDA manufacturer 5

1 (H. Jessen Jorgensen A/S (2013)) 2 (FK Teknik A/S (2013)) 3 (Ahlsell Danmark ApS (2013))4 (Johnson Controls, Inc. (2013)) 5 (SWEP International AB (2013))


Method

Heat exchanger design and calculation

� All HEX are plate type with chevron corrugation

� Commercial plate sizes were applied

� Mass and liquid/vapour maldistribution was neglected

� Counter flow arrangement

� Heat transfer and pressure drop correlations from literaturewas applied

Component Media Zone Heat transfer Pressure dropCondenser H2O Martin (1996) Martin (1996)Condenser Rxxx vapour only: Martin (1996) Martin (1996)

two-phase: Yan et al. (1999) Yan et al. (1999)transcritical: Martin (1996) Martin (1996)liquid only: Martin (1996) Martin (1996)

Evaporator H2O Martin (1996) Martin (1996)Evaporator Rxxx two-phase: Yan and Lin (1999) Yan and Lin (1999)

vapour only: Martin (1996) Martin (1996)


Method

Influence of key economic assumptions on NPV

100 200 300 400 500 600 700 800 900 1000500

1500

2500

3500

4500

5500

6500

7500

8500

Q (kW)

Operatinghours

(h)

NPV=0 EUR

PBP=4 years

PBP=8 years

NPV

(106·EUR)

−0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

(a) NPV of HP system with variations in size and yearlyoperation hours

−50 −40 −30 −20 −10 0 10 20 30 40 50−50

−40

−30

−20

−10

0

10

20

30

40

50

Difference in celec (%)Difference

incgas(%

)

NPV=0 EUR

↑celec<cgas

NPV

(106·EUR)

−0.6

−0.3

0

0.3

0.6

0.9

1.2

1.5

(b) NPV of HP system with variations in fuel cost

Figure: R717-HP heat pump operating at Tsink,out = 60°C, Tlift = 20°C, ∆Tsink=20 K, ∆Tsource=10 K


Examples of working domains











• COP and NPV




• Discussion



Examples of working domains for single stage vapour compression HP

Four different sink andsource temperature glidesinvestigated

∆Tsink/∆Tsource

10K/10K

20K/10K

20K/20K

40K/10K

0

0

10

20

30

40

50

60

70

→ pH > pH,max

↑ TH > TH,max

↑ PBP > 4

↑ PBP > 8

↑ NPV < 0

Tsource,out<0◦C

Tsink,in < Tsource,in (c) LP R717∆Tlift(K

)

→ pH > pH,max

↑ TH > TH,max

↑ PBP > 4

↑ PBP > 8

↑ NPV < 0Tsource,out<0◦C

Tsink,in < Tsource,in (d) HP R717

40 50 60 70 80 90 100 110 1200

10

20

30

40

50

60

70

↓pH>

pH,m

ax

↑ PBP > 8

↑ NPV< 0

Tsource,out<0◦C

∀Tsink,out ∧∆Tlift : PBP > 4

∀Tsink,out ∧∆Tlift : TH < TH,max(e) R600a

Tsink,out (◦C)

∆Tlift(K

)

40 50 60 70 80 90 100 110 120

↓pH>

pH,m

ax

↑ PBP > 8

↑ NPV < 0

Tsource,out<0◦C

∀Tsink,out ∧∆Tlift : PBP > 4

∀Tsink,out ∧∆Tlift : TH < TH,max(f) R134a

Tsink,out (◦C)



Examples of working domains for single stage vapour compression HP


∆Tsink/∆Tsource

10K/10K

20K/10K

20K/20K

40K/10K

0

10

20

30

40

50

60

70

∆Tlift(K

)

Tsource,out<0◦C

Tsink,in < Tsource,in (a)∆Tsink = 10K∆Tsource = 10K

R134a

R600a

R290

R744

R717 LP

R717 HP

Tsource,out<0◦C

Tsink,in < Tsource,in

Low pressure R717

High pressure R717

R600a

(b)∆Tsink = 10K∆Tsource = 10K

40 50 60 70 80 90 100 110 1200

10

20

30

40

50

60

70

Tsink,out (◦C)

∆Tlift(K

)

Tsource,out<0◦C

Tsink,in < Tsource,in (c)∆Tsink = 20K∆Tsource = 20K

R134a

R600a

R290

R744

R717 LP

R717 HP

40 50 60 70 80 90 100 110 120

Tsource,out<0◦C

Low pressure R717

High pressure R717

R600a

(d)∆Tsink = 20K∆Tsource = 20K

Tsink,out (◦C)



Ammonia-Water Hybrid Compression-Absorption HP

Rich xrLean xlVapour xv

Waterj Stream

k Component

1

Compressor

Liquid-vapourseparator

7

Mixer

2

Pump

Sink Sink

3Absorber

Th

rott

lin

gval

ve

Source Source

6Desorber

5

Internal HEXRec

iever

4

8

9

10

2

345

6

7 1

11 12

13 14

(a)(a) Principle sketch of the HACHP

Tem

per

atu

re(◦

C)

Heat Load (kW)

QAbsorber

QDesorber W

T3

T4

Tsink,out

T5

Tsink,in

Tsource,in

T1

Tsource,out

T7

∆Tlift

∆Tsink

∆Tsource

Mixing (adiabatic absorption)

Absorption curve

Heat sink

Heat source

Desorptioncurve

(b) Temperature - heat load diagram of the HACHP



Examples of working domains for Ammonia-Water HybridCompression-Absorption HP


∆Tsink/∆Tsource

10K/10K

20K/10K

20K/20K

40K/10K

0

10

20

30

40

50

60

70

Tsource,out<0◦C LP HACHP

VS.

LP R717

HP R717

HP HACHP

VS.

HP R717

R600a

∆Tsink = 10K∆Tsource = 10K

(a)

-3.0%<

r PV<8.0%

-0.5%<

r PV<16%

-0.5%<

r PV<14%

23%<

r PV<45%∆Tlift(K

)

Tsource,out<0◦C

LP HACHP

VS.

LP R717

HP R717

HP HACHP

VS.

HP R717

R600a∆Tsink = 20K∆Tsource = 20K

(b)

-0.5%< rPV <6.0%

3.0%< rPV <16%

4.0%< rPV <13%

35% < rPV <52%

40 60 80 100 120 1400

10

20

30

40

50

60

70

Tsource,out<0◦C

LP HACHP

VS.

LP R717

HP R717

HP HACHP

VS.

HP R717

R600a∆Tsink = 20K∆Tsource = 10K

(c)

-2.0%<

r PV<9%

1.0%<

r PV<19%

0.5%<

r PV<17%

37%<

r PV<78%

Tsink,out (◦C)

∆Tlift(K

)

40 60 80 100 120 140

Tsource,out<0◦C

LP HACHP

VS.

LP R717

HP R717

HP HACHP

VS.

HP R717

R600a

R744

∆Tsink = 40K∆Tsource = 10K

(d)

43%< rPV <56%

-1.0%< rPV <6.0%

-1.0%< rPV <8.0%

-5.0%< rPV <7.0%

9.0%< rPV <18%

Tsink,out (◦C)



Differences in investment cost for VCHP and HACHP

40 60 80 100 120 1400

10

20

30

40

50

60

70

pH>

pcrit

Tsink,out (◦C)

∆Tlift(K

)

Tsource,out<0◦C

Tsink,in < Tsource,inInvestem

ent(103EUR)

300

320

340

360

380

400

420

440

460

480

500

(a) VCHP (R717-HP)

40 60 80 100 120 1400

10

20

30

40

50

60

70

Tsink,out (◦C)

∆Tlift(K

)

Investement

Tsink,out <0◦C


Investem

ent(103EUR)

300

350

400

450

500

(b) HACHP (R717-HP)

Figure: Investment cost for VCHP and HACHP at ∆Tsink=10 K / ∆Tsource=10 K.


Vapour compression HPs in series











• COP and NPV




• Discussion 0 0.5 1−10

0

10

20

30

40

50

60

70

80

90

100

Heat load (MW)

T(oC)

Refrigerant

Sink media

Source media


Counter−CurrentConfiguration


Qevap,2

Qevap,1

W2

W1

Qcond,2

Qcond,1




0 0.5 1−10

0

10

20

30

40

50

60

70

80

90

100

Heat load (MW)

T(oC)

Refrigerant

Sink media

Source media


Counter−CurrentConfiguration


Qevap,2

Qevap,1

W2

W1

Qcond,2

Qcond,1

0 1

10

20

30

40

50

60

Heat load (MW)

T(oC)


Co−CurrentConfiguration


0 1

10

20

30

40

50

60

Heat load (MW)

T(oC)


ParallelEvaporator


0 1

10

20

30

40

50

60

Heat load (MW)

T(oC)


ParallelCondenser




COP and NPV of VCHPs in series

No Series 2 3−50

−40

−30

−20

−10

0

10

20

Number of HP in series

Dev

iation

from

reference

system

(%)

Counter−current

Co−current

Parallel Evap.

Parallel Cond.

COPNPV

(a) ∆Tsink/∆Tsource =20K/20K

No Series 2 3−50

−40

−30

−20

−10

0

10

20

Number of HP in seriesDev

iation

from

reference

system

(%)

Counter−current

Co−current

Parallel Evap.

Parallel Cond.

COPNPV

(b) ∆Tsink/∆Tsource =40K/10K

Figure: Changes to COP and NPV for four serial connected HP schemes with even heat load for serialconnected units. COP and NPV are calculated for R717-HP units in series.



Load sharing for two vapour compression HPs in series

0.3 0.4 0.5 0.6 0.720

25

30

35

40

45

50

Heat load distribution for HP1 (-)

Tlift(K

)

CO

P (

−)

3.5

4

4.5

5

5.5

(a) COP

0.3 0.4 0.5 0.6 0.720

25

30

35

40

45

50

Heat load distribution for HP1 (-)

Tlift(K

)

34(bar)35

(bar)

36(bar)

180 (o C)

NP

V (

EU

R)

0

0.5

1

1.5

2

2.5

3

3.5

4

x 105

(b) NPV

Figure: COP and NPV variations with variation of the heat load fraction and temperature lift. Results arecalculated for Tsink = 70 (°C) and ∆Tsink/∆Tsource =20K/20K.



Comparison with working domain for single stage VCHP

Two different serialconnected VCHPinvestigated

HP1 HP2

#1 R717-HP R717-HP#2 R600a R717-HP

Tsink,out (◦C)∆T

lift

(K)

Tsource,out<0◦C

Tsink,in < Tsource,in∆Tsink = 20K∆Tsource = 20K

(a)

40 50 60 70 80 90 100 110 1200

10

20

30

40

50

60

70

Tsink,out (◦C)

∆T

lift

(K)

Tsource,out<0◦C


∆Tsink = 40K

∆Tsource = 10K

R600a

R744

R717 LP

R717 HP

Series 1

Series 2

#1#2 (b)

40 50 60 70 80 90 100 110 1200

10

20

30

40

50

60

70

Tsource,out<0◦C

Low pressure R717High pressure R717R600a

Series #1Series #2

( )∆Tsink = 20K∆Tsource = 20K

Tsink,out (◦C)

∆T

lift

(K)

40 50 60 70 80 90 100 110 1200

10

20

30

40

50

60

70

Tsource,out<0◦C


Low pressure R717High pressure R717R600aR744

Series #1Series #2

( )∆Tsink = 40K∆Tsource = 10K

Tsink,out (◦C)∆T

lift

(K)


Further steps











• COP and NPV




• Discussion

35

4


Further steps

Two economic cases (industrial and DH)

No Series 2 3−30

−20

−10

0

10

20


Deviationfrom

reference

system

(%)

COP Industrial

NPV Industrial

COP District Heating

NPV District Heating

(a) ∆Tsink / ∆Tsource = 20 K / 20 K

No Series 2 3−30

−20

−10

0

10

20


Deviationfrom

reference

system

(%)

COP Industrial

NPV Industrial

COP District Heating

NPV District Heating

(b) ∆Tsink / ∆Tsource = 40 K / 10 K


Further steps

Two stage HP configurations

� Individual models for each component

- A high amount of configurationspossible.

- Generic solutions to optimalconfigurations are needed.

- High amount of free variables, eg.oil integration only constrained tointervals.

M

(a) Heat exchangers not fixed connection to heat sink


Further steps

HP configurations in series

M M

(a) Possibilities for creating various two stage HP cycle layouts


Discussion











• COP and NPV




• Discussion


Discussion

Important findings from analysis

The analysis of working domains shows, that sink temperatures of up to 120 - 140 °C and temperature lifts40 - 60 K may be obtained using VCHP and HACHP technologies.

� The NPV is favourable for the technologies utilising R717, but a technical constraint (the dischargetemperature) limited the applicability in terms of temperature lift.

� Serial connection of VCHP increases the COP, but at decreased NPV. If more than one heat pump isneeded due to capacity constriants, the increase in COP from serial connection of the considered unitsshould be included.

� VCHP in series increases the working domain of current technical and economic constraints. Either dueto reduction in resulting discharge temperature of compressor or mixed working fluids selection toobtain combination of certain characteristics.

Further work and analysis is required to obtain generic tool, as a high amount of configurations are possible.

� Input are welcome for other HP configurations, changed temperature sets or economic cases.


Discussion

Thank you for your attention

� If questions, new ideas or interest in new projects: [email protected]

Work funded by:

� Copenhagen Cleantech Cluster

� Dong Energy

� DTI

� DTU

� EUDP


DiscussionReferences I

Ahlsell Danmark ApS (2013). Priskatalog 2013. [accessed 26.09.13].

Brunin, O., Feidt, M., and Hivet, B. (1997). Comparison of the working domains of somecompression heat pumps and a compression-absorption heat pump. International Journal of

Refrigeration, 20(5):308.

FK Teknik A/S (2013). Priskatalog 2013. [accessed 26.09.13].

H. Jessen Jorgensen A/S (2013). Priskatalog 2013. [accessed 26.09.13].

Jensen, J., Ommen, T., Markussen, W., Reinholdt, L., and Elmegaard, B. (2015). Technical andeconomic working domains of industrial heat pumps: Part 2 - ammonia-water hybridabsorption-compression heat pumps. International Journal of Refrigeration.

Johnson Controls, Inc. (2013). HPO R717 compressor cost - non-disclosure agreement. privatecommunication.

Martin, H. (1996). A theoretical approach to predict the performance of chevron-type plate heatexchangers. Chemical Engineering and Processing: Process Intensification, 35(4):301–310.

Ommen, T., Jensen, J., Markussen, W., Reinholdt, L., and Elmegaard, B. (2015a). Technical andeconomic working domains of industrial heat pumps: Part 1 - single stage vapour compressionheat pumps. International Journal of Refrigeration.

Ommen, T., Jensen, J., Markussen, W., and Elmegaard, B. (2015b). Enhanced technical and

economic working domains of industrial heat pumps operated in series. The InternationalInstitute of Refrigeration.

SWEP International AB (2013). SWEP - products and solutions - non-disclosure agreement.private communication.


DiscussionReferences II

Yan, Y. Y. and Lin, T. F. (1999). Evaporation heat transfer and pressure drop of refrigerantr-134a in a plate heat exchanger. Journal of Heat Transfer, 121(1):118–127.

Yan, Y. Y., Lio, H. C., and Lin, T. F. (1999). Condensation heat transfer and pressure drop ofrefrigerant r-134a in a plate heat exchanger. International Journal of Heat and Mass Transfer,42(6):993–1006.


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