Low GWP refrigerant heat pumps in Sweden

Research and MarketBjörn Palm

KTH Royal Institute of Technology

IEA HPC Annex 54 Heat pump systems with low GWP refrigerants Update from Sweden

Outline

• Introduction• Finalized research projects • Ongoing research projects• Products on the market• Challenges

IEA HPC Annex 54 Heat pump systems with low GWP refrigerants Update from Sweden

Introduction

IEA HPC Annex 54 Heat pump systems with low GWP refrigerants Update from Sweden

Some basic facts

• Low GWP refrigerants are flammable (Exception CO2)• Flammability introduces new risks• Risk is connected to the charge• Charge of refrigerant has not been an issue before• Standard systems are not designed to minimize charge

• Designs for low GWP refrigerants should be designs for low charge

IEA HPC Annex 54 Heat pump systems with low GWP refrigerants Update from Sweden

Flat tubes reduce volume

• Same heat transfer area,

• Different cross sectionalareas

Design for low charge – general considerations• Keep volume low• Maintain surface area of heat exchangers• Avoid liquid pools

PROPANE Condenser, Tsat=50C Evaporator, Tsat=-15C

Liquid density 448,9 kg/m3 548,2 kg/m3

Vapor density 38,6 kg/m3 6,50 kg/m3

Liquid to vapor density

ratio

11,6 84,3

Finalized research projectsHydrocarbon heat pumps

IEA HPC Annex 54 Heat pump systems with low GWP refrigerants Update from Sweden

Example 1, calculation example,Based on design from EU-project GreenHP

• Air to water heat pump• Heating capacity 30 kW @ -15 / +50• Propane as refrigerant• Hermetic scroll compressor• Internal heat exchanger

condensercompressor

evaporatorexpansiondevice

liquid-suctionheat exchanger

iskh ,1

h k2

h "k2

′h1

hs

Design of aluminium heat exchangers

Baffle plates

End plates

Shell plates End-cap

Heat exchanger used as evaporator and condenser in propane heat pump

Compressor

• Volumes based on existing suction gas cooled scroll• Volume of shell: 15 liters• Assume free volume 1/3, i.e. 5 liters• Assume 15% of free volume on high pressure side• Assume oil charge 1,5liter ( 1 liter less than recommended)• Assume 3% propane absorbed in the oil @ nom (-15C)

• Assume linear increase to 6% @+15C• => Mass of propane,

• in hp vapor: 30g, in lp vapor: 20g, in oil: 38g @ nom• Total mass: 88g @ nom

Connecting tubing

• Most important to keep liquid line short• Least important to keep suction line short• Select diameter so that pressure drop is less than 0,1K• Assumptions made:

• Hot gas line: 0,5m, 5/8”, => mass: 2g @ nom• Liquid line: 0,2m, 3/8”, => mass: 4g @ nom• Suction line: 1m, 1 1/8”, => mass: 3g @ nom

Distribution of volumes

Distribution of charge• Total necessary charge @ nominal

conditions, receiver gas filled: 397g

Distribution of charge• Total necessary charge @ nominal

conditions: receiver liquid filled, 643g

Distribution of charge at different evaporation temperatures, TC=50C

Example 2: Small propane heat pump at Royal Institute of Technology, Stockholm• Aim: Design a water-to-water heat pump with the heating capacity

5kW with charge less than 150g propane.

• Typical charge: 1-2 kgof HFC

http://geothermal.marin.org/GEOpresentation/sld103.htmhttp://geothermal.marin.org/GEOpresentation/sld103.htm

Schematic drawing of tested heat pump system

Compressor

Exp. Valve

DP

DP Evaporator Condenser

V3 V2

V4 V1

T1

T2

T3

T4

T5

T6

T7

T8 T9

T10

water inlet

water outlet glycol inlet

glycol outlet

refrigerant draining point

refrigerant draining point

P1

P2

Quick-closing valves

DP

DP

T4

P1

refrigerant draining point

refrigerant draining point

Evaporator

Condenser

P2

glycol outlet

glycol inlet

water outlet

water inlet

T10

T9

T8

T7

T6

T5

T3

T2

T1

V1

V4

V2

V3

Exp. Valve

Compressor

End view of multichannel aluminium heat exchanger (used as evaporator and condenser).• Length: 651 mm• Hydraulic diameter: 1,4 mm (on refrigerant side)

HEATSET 2005

System performance with new Aluminium multichannel heat exchangers

Heat source/sink temp (°C)

Refrigerant charge in compressor

Problems• Propane is highly soluble in mineral oil and in POE oils.• Oil content is normally high• Compressor internal volume is large

Solutions• Propane has low miscibility with some PAG oils.• Use compressors with lower charge of oil• Use compressors with smaller internal volume

Compact automotive compressor, with and without electric motor attached. (Sanden Corp.)

Comparison between traditional hermetic compressor and semi-hermetic compressor developed for hybrid car. (Mass of propane is estimated)

Type of compressor Traditional For hybrid car External volume, dm3 17 5 Mass of propane, g 70-80

Borehole collector

House radiators

Warm water heat exchanger

Internal heat exchanger

Evaporator

Condenser

Example 3Low charge water/water heat pump with 100g propane.

2-10 kW capacity

From: Klas Andersson

No filter/dryerNo sight glassNo separate receiver

Sanden SHS33Scroll DC motor

Compressor

210 mm

125m

m

33 cm3/rev800-9000 rpmSemi hermetic

InverterControl

Suctionside

Dischargeside

500 cm34.6 g

260 cm36.6 g

< 50 gram PAG oil

Q2= 4.8 kWT1=40°C T2=2.5°C

Evaporator and CondenserAirec - PentaPropAsymmetric brazed plate hex.

Sub-cooler∆qv ~ 1 %/°C∆COP2 ~ 0.12 %/°C

350 mm

Evaporator 30 plates ~ 23 gCondenser 50 plates ~ 52 g

Q2= 4.8 kWT1=40°C T2=2.5°CTsup=Tsub=4 K

Finalized research projectsDevelopment of an 8 kW water/water heat pump with ammonia

IEA HPC Annex 54 Heat pump systems with low GWP refrigerants Update from Sweden

Development of an 8 kW water/water heat pump with ammonia

Challenge to find suitable components for small ammonia systems

Basic design of NH3 hp

Prototype of 8 kW water/water heat pump with 100 g of ammonia as refrigerant

Ongoing research

Ongoing projects at RI.SE on low GWP refrigerants• Participation in international standards commissions, e.g. EN378• Courses on flammable refrigerants and F-gas regulations• Development of course material and risk assessments

Ongoing projects at KTH on low GWP refrigerants• System performance of low GWP refrigerants and blends (also HFO)• Booster high temp heat pump with isobutane as refrigerant (EcoPac)• High temp industrial heat pumps with low GWP refrigerants

Ecopac for Sonority type heat pumpsJan-Erik Nowacki

R290 102 m³/h

55 °C, 71 kW

-7 °C

70 °C, 15 kW

R600a? m³/h

Low GWP hp market in Sweden

Heat pumps on the Swedish market with low GWP refrigerants• Some air /water heat pumps with propane• Very few water / water heat pumps with propane• (Water / Water heat pumps with R32)• (Air / Air heat pumps with R32)

• (May not be a complete list… )

Challenges

Challenges with low GWP refrigerants

• Flammability – new designs with low charge is required• Standardization – necessary for market implementation• Refrigerant (HFO) blends – requires new designs and may still cause

problems in practical applications. • Environment (HFO) – formation of TFA and possibly other

decomposition products not well investigated and risks not taken seriously

Thank you for your attentionBjörn Palm, bpalm@energy.kth.se

Low GWP refrigerant heat pumps in Sweden��Research and MarketOutlineIntroductionSome basic factsFlat tubes reduce volumeDesign for low charge – general considerationsFinalized research projectsExample 1, calculation example,�Based on design from EU-project GreenHPDesign of aluminium heat exchangersHeat exchanger used as evaporator and condenser in propane heat pumpCompressorConnecting tubingDistribution of volumesDistribution of chargeDistribution of chargeDistribution of charge at different evaporation temperatures, TC=50CExample 2: Small propane heat pump at Royal Institute of Technology, StockholmSchematic drawing of tested heat pump systemEnd view of multichannel aluminium heat exchanger (used as evaporator and condenser). System performance with new Aluminium multichannel heat exchangersRefrigerant charge in compressorCompact automotive compressor, �with and without electric motor attached. �(Sanden Corp.) Comparison between traditional hermetic compressor and semi-hermetic compressor developed for hybrid car. �(Mass of propane is estimated) Slide Number 24Slide Number 25Slide Number 26Evaporator and CondenserFinalized research projectsSlide Number 29Challenge to find suitable components for small ammonia systemsBasic design of NH3 hpPrototype of 8 kW water/water heat pump with 100 g of ammonia as refrigerantSlide Number 33Ongoing researchOngoing projects at RI.SE on low GWP refrigerantsOngoing projects at KTH on low GWP refrigerantsEcopac for Sonority type heat pumpsLow GWP hp market �in SwedenHeat pumps on the Swedish market with low GWP refrigerantsChallengesChallenges with low GWP refrigerantsThank you for your attention