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, [email protected]
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