THE EXPERIENCE OF THE ITALIAN TEAM WITHIN
THE IEA-HPT ANNEX 54
Sergio BOBBO
CNR-ITC, PADOVA, ITALY

IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

THE ITALIAN TEAM

Dipartimento di Ingegneria
Politecnico di Miano

MILANOPADOVA

CNR ITC
Consiglio Nazionale delle Ricerche
Istituto per le Tecnologie della Costruzione

STETDipartimento di Ingegneria Industriale
Università degli Studi di Padova

ROMA

RECENT ACTIVITIES
Annex 54
Heat Pump Systems with Low GWP Refrigerants

IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

Construction Technologies Institute(ITC)
National Research Council (CNR)
Refrigerants and nanofluids Research group

IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

Available Experimental Data On HFOs (2021)
Thermodynamic Properties

8 fluids
5 fluids

14 fluids

6 fluids

ASHRAE
Designation

R1234ze (E)R1234yf
R1233zd(E)R1234ze(Z)R1336mzz(Z)R1224yd(Z)R1243zf
R1123
R1132aR1354mzy(E)R1225ye(Z)R1336mzz(E)RE356mzz
R1354myf(E)R1132(E)R1132(Z)R1141
R1225ye(E)R1234ye(E)CriticalpointSets
1211112211Data
1211112211SaturatedpressureSets131457725311110 data sets

Data
274
186
150
226
7746
185
56
24
1496
17PVT
Sets
1310775434131111Data
1516
989
675
653
653
162619
349
131
183
240
169
105
47

Other Properties
Speedof sound

C0, Cp, Cv
Sets
662
111Data
332
402
44
94
140
36

Sets
582111Data
551
336
290
38183

Thermalconductivity

Viscosity

Sets
211111Data
1081
790115451599112

Sets4752221Data
201306213(n.a.)206
1361421591116

Surfacetension
Sets
3231Data
3639
27132214425
1620

1 data set

IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

2 or more data sets

Measured Thermophysical Properties
VLE
binary mixtures

SATURATED PRESSURE

pure fluids
2.5

R32+R290

2000

UnivPMDENSITY
compressed liquid

CNR ITC

1.5

1.0

UNCERTAINTIES

TPX

1000

500

± 0.02 K±1kPa± 0.030.500.0

0.2

0.4

0.6

0.8

1.0x1, y10.0
220

270

320

370

Temperature (K)40R1225ye(Z)35
CNR ITC
30Pressure (MPa)

Pressure (kPa)

1500

252015105

UNCERTAINTIESTPSOLUBILITY in lubricants± 0.02 K
±1kPa

01000

1200

1400

Density (kg·m-3)

12CO2+PEB7
10

Pressure (kPa)

Saturatied Pressure (MPa)R1225ye(Z)
2.0

UNCERTAINTIES8UNCERTAINTIES

6TPX

T

4
2
00.0

0.5

x1, y11.0± 0.03 K±2kPa± 0.001-0.01

TPρ± 0.05 K± 10kPa± 0.1%

Ground Source Heat Pumps (GSHPs) Cycles Simulations•PROJECT: GEO4CIVHIC – Horizon 2020
Most Easy, Efficient and Low Cost Geothermal
Systems for Retrofitting Civil and Historical Buildings• SCOPE identify the most suitable alternatives to thepresent high GWP refrigerants used in geothermalheat pumps.
New heat pump working with selected alternativerefrigerants will be developed within the project• CONSTRAINT: Regulation (EU) No 517/20, 2014
• REFERENCE FLUIDS: R134a and R410A• METHODOLOGY Energetic and Exergetic analysis• CYCLES: basic, regenerative, interrefrigeration, …
• SIMULATION TOOLS: homemade simulation programs
developed in Matlab environment
IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

Analysed Refrigerants
 HIGH PRESSURE and INTERMEDIATE GWP (<800) refrigerants
 reference fluid R410A
Fluid

GWP

ASHRAE
Safety Class
[27]

R410A

2088

A1

R32/R125 (50/50)

343.32

4.770

0.05

221.15

R32675A2L

R32 (100)351.555.816-221.15

R454B

466

A2L

R32/R1234yf (68./31.1)

350.155.041

1

222.15

R452B

698

A2L

R32/R125/R1234yf(67/7/26)

350.255.200

0.9

222.15Composition (wt %)

Tcrit
(K)

Pcrit
(MPa)

T Glide(K)

NPB(K)IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

Analysed Refrigerants
 LOW PRESSURE and INTERMEDIATE GWP (<800) refrigerants
 reference fluid R134a
FLUID

REFERENCE

POTENTIAL
ALTERNATIVES

GWP

NBP
(°C)

Safetyclass(ASHRAE)

Components

Compositio(wt%)

T glide(K)

R134a

1300 -26.1

A1

R32/R125

50/50

0

R513A

631-29.2

A1

R1234yf/R134a

56.0/44.0

0

R515A

393-18.0

A1

R1234ze(E)/R227ea88/120

R515B

293-19.1

A1R1234ze(E)/R227ea

91.1/8.9

0R516A

142-29.4

A2L

R134a/R1234yf/R152a8.5/77.5/14

0

IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

Operative Conditions
Base cycle•••••

Regenerative cycle• Thermal power 7 kW

Thermal power 7 kW
Ideal heat exchangers
Countercurrent heat exchangers
Evaporator: ∆Tpinch-point = 6°CCondenser: ∆Tpinch-point = 3°C• Ideal heat exchangers• Countercurrent heat exchangers• Condenser/evaporator ∆Tpinch-point = 3°C

GROUND SOURCEUTILITY

T inletT outletT inletT outlet

[°C]

[°C]

[°C]

[°C]

0-325303030357440451075055

IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

Preliminary Results
HIGH PRESSURE Refrigerants – reference R410A• R454B is the most promising substitute for R410A with all the analyzed
cyclesLOW PRESSURE Refrigerants – reference R134a• R516A is the MOST EFFICIENT refrigerant (COP +10% with reference to R134a)• The BEST CYCLE looks to be the one with FLASH TANK+AUXILIARY COMPRESSOR•NEXT STEP identify VERY LOW GWP REFRIGERANTS (GWP<150) with equal or
increased energy efficiency with respect to traditional refrigerants, goodvolumetric properties and acceptable flammability.

•Not only pure compounds (e.g. R1233zd(E)) will be considered but also new MIXTURES

IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

Ground Source Heat Pumps (GSHPs) Monitoring System•

PROJECT: GEO4CIVHIC – Horizon 2020
Most Easy, Efficient and Low Cost Geothermal Systems forRetrofitting Civil and Historical Buildings• SCOPE:•evaluate energetic performance of GSHPS withintermediate GWP refrigerant and different controlsystems

GHPSs: 2 different reversible water/glycol to water HPs− CONTROL SYSTEM:− HEAT SOURCE:− HEAT SINK:• REFRIGERANT:

1 ON/OFF; 1 INVERTER
3 different types of geothermal probes
heating and SHW in small commercialbuilding
R454B• MONITORING SYSTEM:
33 temperature sensors 16 pressure sensors
2 mass flowmeters
3 volumetric flowmeters
6 electric energy meters•ACQUISITION PROGRAM: at least 12 months acquisitionacquisition time step: 15 s

• STATUS: due to the COVID-19 restrictions, the beginning of themonitoring has been postponed and will start in the next weeks

Department of Energy
Politecnico di Milano

IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

Luca Molinaroli

Purpose of the activities
 Experimentally compare the performance of• R134a• R1234yf• R1234ze(E)• R450A• R513A

in a water-to-water heat pump in a drop-in application.
 Tests are carried out setting:• (i) the vapour superheating at the evaporator outlet,• (ii) the secondary fluids flow rates• (iii) the temperatures of the secondary fluids at heat exchangers outlets.
The system finds its own operating point (evaporating and condensing pressures, subcooling atcondenser outlet) depending on the refrigerant used.
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Experimental set-up – Layout

IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

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Experimental set-up – testing conditions• Reference conditions: conditions
used to identify secondary fluid mass
flow rates. ΔT across heat exchanger
fixed to 5 °C.
• Testing conditions: the mass flowrate and the outlet temperature arekept constant.

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Experimental set-up – Components• Water-glycol temperature at evaporator outlet equal to 5 °C.
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Department of Industrial Engineering (DII)
University of Padova
STET Research group

Drop-in analysis of R134a, R1234yf, R1234ze(E), R450A
and R513A in a small water-to-water heat pump
IT Workshop for IEA-HPT
ExCoMeeting - November 11th, 2021
LucaMolinaroli

Department of Industrial Engineering - UNIPDInvolvement in Annex 54

The Department of Industrial Engineering (DII) - University of Padova - participates in Annex 54
activities starting from 2019.
The research activity is focused on:• heat transfer measurements with low-GWP refrigerant mixtures;• experimental investigation of a solar assisted heat pump working with CO2.
The activity is performed at the Sustainable Thermal Energy Technologies (STET) research group- Prof. Davide Del Col- Dr. Stefano Bortolin

IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

http://stet.dii.unipd.it/

Heat transfer measurements with low-GWP mixtures

Heat Transfer Coefficients (HTC) Measurements Set-Up•

The availability of reliable tools for heat exchangers design is important for the project of heat pumps
operating with new low-GWP fluids.

•

In some cases, new refrigerants are non-azeotropic mixtures and thus, during phase-change at constantpressure, they present a temperature glide.

•Two experimental test rigs are available for the study of heat transfer during condensation and flow boiling.

•One experimental apparatus is designed for conventional channels (8 mm internal diameter) while the othertest rig allows to measure heat transfer coefficients (HTC) inside small diameter channels (from 3 mm downto 1 mm).

Test rig for HTC measurements in
1 mm and 3 mm diameterchannels.

Test rig for HTC
measurements in a 8 mm
diameter channel.

Heat transfer measurements with low-GWP mixtures

Measurements on HFO+HFC mixtures

 Condensation heat transfer coefficients, flow boiling heat transfer coefficients, pressure drop andtwo-phase flow regimes have been investigated with refrigerants blends obtained mixing HFC andHFO fluids.
The following mixtures have been considered:•binary R32/R1234ze(E) non-azeotropic A2L blends at three different mass compositions;•

R452B (R32/R1234yf/R125 at 67/26/7% by mass composition), GWP100= 676 , A2L class,possible substitute for R410A;•

R455A (R32/R1234yf/R744 at 21.5/75.5/3% by mass), GWP100= 146, A2L class;•R450A (R1234ze(E)/R134a 58.0/42.0% by mass), GWP100= 547, A1 class, possible substitutefor R134a;•R515B (R1234ze(E)/R227ea 91.1/8.9% by mass), GWP100= 299, A1 class, possible substitutefor R134a.

 Correlations for condensation and flow boiling heat transfer coefficients have been validated against thepresent experimental database.

Solar assisted heat pump working with CO2

Activity on solar assisted Heat Pumps (SAHPs)

 Solar Assisted Heat Pumps (SAHPs) consist in heat pump systems that work with the solar source as low
temperature thermal source.
 There are two types of SAHPs:••

indirect solar assisted heat pumps (IDX-SAHPs) where a secondary fluid is heated up in solar collector and then it issent to the evaporator;
direct solar assisted heat pumps (DX-SAHPs), where the solar collector acts itself as the evaporator.

 A novel direct expansion solar assisted heat pump prototype working with CO2 as refrigerant has been
installed at UNIPD.
 The prototype is a 4 kW heat pump that can produce hot water. The heat pump can work alternatively with afinned coil evaporator or with a PV-T solar evaporator.
 The study has been realized in the framework of Solair-HP CSEA project.

Overall Experience
Annex 54
Heat Pump Systems with Low GWP Refrigerants

IT Workshop for IEA-HPT ExCo Meeting - November 11th, 2021

Overall experience First ever participation in an IEA HPT Annex for all groups (since 2019)
 Pros• networking with many research groups from all over the world.
• large exchange of ideas and information about research activities and last developments on heatpumps with low-GWP fluids.
• Update on R&D activities both at academic and industrial level.
• disseminate the results during workshops hosted in international conferences Cons• the Annex activity is on low-GWP refrigerants and each member contributes to the general themewith his/her usual R&D work. Our general impression is that there are many "spot contributions" tothe general topic rather than some clear research lines.
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THANK YOU!
IIR/IEA Annex 54 workshop – September 1st, 2021