US Workshop for IEA-HPT ExCo @ NIST, Gaithersburg, MD

Improving Vapor Compression System Efficiency throughAdvanced Vapor Compression Technologies
Prof. Eckhard A. Groll
Reilly Professor of Mechanical Engineering
William E. and Florence E. Perry Head of Mechanical Engineering

Dr. Davide Ziviani
Research Assistant Professor
Associate Director of the Center for High Performance Buildings

November 12, 2019
© E.A. Groll & D. Ziviani

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Outline• Advanced Heat Pump Systems:• Hybrid Drive Variable-Speed Compression• Refrigerant Injected Compression with Economization• Liquid Flooded Compression with Internal Regeneration• Cold-Climate Heat Pump
• Quasi-Isothermal Compression with Cylinder Cooling and Internal Regeneration• Chemical Looping Heat Pump

• Summary and Perspectives© E.A. Groll & D. Ziviani

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Outline

Advanced Heat Pump Systems
Hybrid-Drive Variable-Speed Compression© E.A. Groll & D. Ziviani

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Hybrid-Drive Variable Speed Compression
Overview• Variable Speed PSC Compressor• Uses a standard PSC motor that can run without the electronic drive at full load
• Adds a low power variable speed drive for part load operation• Full load operation• The PSC motor operates off of 60 Hz line power with no losses due to power electronics.

• Part load operation• The low power inverter is used to enable variable speed operation and provide frequencies of 45 Hz and below tothe PSC motor.

Separation of line electronic drive
circuitry using a relay. [Chretien et al.]Electronic Drive Control [Chretien et al.]

© E.A. Groll & D. Ziviani

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Hybrid-Drive Variable Speed Compression
Compressor Testing• Chretien et al. tested the variable speed control of PSC compressors on multiple residential heat pumpsystems in a laboratory setting for improvements in SEER
• 7% - 12% improvement in SEER reported for systems with PSC scroll compressors• 25% – 40% improvement in SEER reported for systems with PSC rotary compressors• Further investigation of compressors motivated by heat pump system testing• Part load performances of rotary and scroll compressor varied significantly in heat pump tests

Overall Isentropic
Efficiency of a Scroll andRotary Compressor eachtested in an Air-Source
Heat Pump.

© E.A. Groll & D. Ziviani

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Hybrid-Drive Variable Speed CompressionCompressor Testing (cont’d)• Preliminary results show stronger correlation between compressor speed and compressor efficiency forscroll than for rotary• Degradation of performance• Full speed efficiency of scroll compressor at 60 Hz line power and identical operating point was 8% lower incalorimeter testing after heat pump testing.

Volumetric and Overall Isentropic
Efficiency of a Scroll and Rotary
Compressor each tested in theCalorimeter.

© E.A. Groll & D. Ziviani

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Hybrid-Drive Variable Speed Compression
System Testing

ANSI/AHRI Heat Pump Tests for fixed-speed
compressor and constant volume indoor fanAir entering outdoor unit°F/°C

Air entering outdoor unit°F/°C

Dry–bulb

Wet–bulb

Dry–bulb

Wet–bulbAirvolumerate

A (required)95.0 / 35.0

75.0 / 23.9

80.0 / 26.7

67.0 / 19.4

Full–load

B (required)82.0 / 27.8

65.0 / 18.3

80.0 / 26.7

67.0 / 19.4

Full–load

Test
description

ANSI/AHRI Heat Pump Tests for variable-speed
compressor and constant indoor fan
Air entering outdoor unit°F/°C

Air entering indoor unit °F/°C

Dry–bulb

Wet–bulb

Dry–bulb

Wet–bulb

A2 (required)95.0 / 35.0

75.0 / 23.9

80.0 / 26.7

B2 (required)82.0 / 27.8

65.0 / 18.3

80.0 / 26.7

EV (required)87.0 / 30.6

69.0 / 20.6

80.0 / 26.7

B1 (required)82.0 / 27.8

65.0 / 18.3

F1 (required)67.0 / 19.4

53.5 / 11.9

Test description© E.A. Groll & D. Ziviani

Compressor
speed

Air volumerate

67.0 / 19.4

Maximum

Full–load67.0 / 19.4

Maximum

Full–load67.0 / 19.4

Intermediate

Intermediate80.0 / 26.7

67.0 / 19.4

Minimum

Minimum

80.0 / 26.7

67.0 / 19.4

Minimum

Minimum

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Hybrid-Drive Variable Speed Compression
System Testing (cont’d)

TestCompressor
Type

Outdoor Fan
Motor

Variable
Speed
Components

Fixed Speed
Components

SSHP1

ScrollPSC

None

Compressor
Outdoor Fan

SSHP2

RotaryPSC

None

Compressor
Outdoor Fan

VSHP1

RotaryPSC

Compressor

Outdoor Fan

VSHP2

RotaryPSC

Compressor
Outdoor Fan

None

VSHP3

RotaryECM

Compressor
Outdoor Fan

None© E.A. Groll & D. Ziviani

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Outline

Advanced Heat Pump Systems
Refrigerant Injected Compression with Economization© E.A. Groll & D. ZivianiSlide 9/43

Refrigerant Injected Compression with Economization
System Overview© E.A. Groll & D. Ziviani

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Refrigerant Injected Compression with Economization
Multiple Injection PortsR-410A vapor compression cycle with three injection ports (Mathison 2008)© E.A. Groll & D. Ziviani

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Refrigerant Injected Compression with Economization
Multiple Injection Ports (cont’d)

Variation in relative COP with number of injection
points for R-410A cycle operating at evaporating
temperature of -20 °C and condensing
temperature of 50 °C

Variation in normalized cooling capacity andpower consumption with number of injection
points for R-410A cycle operating at evaporating
temperature of -20 °C and condensing
temperature of 50 °C© E.A. Groll & D. Ziviani

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Refrigerant Injected Compression with Economization
Limit of Economization

R-410A vapor compression cycle with continuous injection (Mathison 2008)© E.A. Groll & D. Ziviani

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Refrigerant Injected Compression with Economization
Experimental Work: single vs. two injection lines❑ Hermetic scroll compressor for cold-climate heat pump (Bell et al. 2013)• Symmetric scroll wraps with constant wall thickness• Single- and double-injection points• R-290; Volume ratio 3• 𝑝evap = 244.5 kPa (−20 C) , 𝑝cond = 1476.7 kPa (43.3 C), ∆𝑇sh = 11.1 K© E.A. Groll & D. Ziviani

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Refrigerant Injected Compression with Economization
Experimental Work: single vs. two injection lines❑ Hermetic scroll compressor for cold-climate heat pump (Bell et al. 2013)© E.A. Groll & D. Ziviani

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Refrigerant Injected Compression with Economization
Experimental Work: Military ECU with R-407C❑ ECU for cooling application in cold climates (Bahman et al. 2018)© E.A. Groll & D. Ziviani

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Outline

Advanced Heat Pump Systems
Liquid Flooded Compression with Internal Regeneration© E.A. Groll & D. Ziviani

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Liquid Flooded Compression with Internal Regeneration
Introduction

Cycle Schematic of Liquid Flooded Compression with Regeneration (Bell 2011)© E.A. Groll & D. Ziviani

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Liquid Flooded Compression with Internal Regeneration
Thermodynamic Modeling

Cycles in T-s Diagram

Modeling Results

Bell, I.H., Groll, E.A., and Braun, J.E., “Performance of Vapor Compression Systems with Compressor Oil
Flooding and Regeneration,” Int’l J. Refrigeration, Vol. 34, No. 1, 2011, pp. 225-233.

© E.A. Groll & D. Ziviani

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Liquid Flooded Compression with Internal Regeneration
Experimental Results• Oil Flooded R-410A Scroll Compressor• Running gear modifications for R-410A and flooding• Shaft and rotor modifications for better compressor
balance• 4 inch3 suction volume• 3.29 volume ratio

Oil Injection #1

Location of Oil Injection PortsOil Injection #2© E.A. Groll & D. Ziviani

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Liquid Flooded Compression with Internal Regeneration
Experimental Results (cont’d)• Cold-climate heat pump with oil-flooded compression (Ramaraj et al. 2014)• R-410A• ISO 32 POE• Tcd = 43.3 ℃; varied Tev© E.A. Groll & D. Ziviani

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Liquid Flooded Compression with Internal Regeneration
Experimental Results: 𝑇cond = 43.3 ℃© E.A. Groll & D. Ziviani

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Liquid Flooded Compression with Internal Regeneration
System Results (Ramaraj et al., 2016)© E.A. Groll & D. Ziviani

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Outline

Advanced Heat Pump Systems
Cold-Climate Heat Pumps© E.A. Groll & D. Ziviani

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Cold-Climate Heat Pumps

Cycle Configurations (Bertsch and Groll, 2008)• Simplified schematics of:
a.
b.
c.
•

Two-stage cycle with intercooler
Two-stage cycle with closed economizer
Cascade cycle

Heating mode with ambient temperatures from -30 °C to 10 °C and supply temperatures from 40-60 °C© E.A. Groll & D. Ziviani

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Cold-Climate Heat Pumps

Cycle Configurations (Bertsch and Groll, 2008)• Cycle comparisons:• Heating mode supply temperatures of 50 °C© E.A. Groll & D. Ziviani

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Cold-Climate Heat Pumps

Experimental Work (Bertsch and Groll, 2008)© E.A. Groll & D. Ziviani

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Cold-Climate Heat Pumps

Recent Developments: Packaged Propane Heat Pump

© E.A. Groll & D. Ziviani

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Outline

Advanced Heat Pump Systems
Quasi-isothermal Compression with Cylinder Cooling andInternal Regeneration© E.A. Groll & D. Ziviani

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Cylinder Cooling with Internal Regeneration
Concept Description© E.A. Groll & D. Ziviani

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Cylinder Cooling with Internal Regeneration

Thermodynamic Diagrams: Effect of Intermediate Pressure
Cycles in p-h Diagram

Cycles in T-s Diagram© E.A. Groll & D. Ziviani

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Cylinder Cooling with Internal Regeneration
Parametric Studies

Compressor temperature riseversus intermediate pressure ratio
for different regenerator efficiencies

COP improvements compared toconventional vapor compression cycle
as a function of evaporating temperature© E.A. Groll & D. Ziviani

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Cylinder Cooling with Internal Regeneration
Employing Linear Compressor

Simulation modeland several
prototypes weredeveloped bySunPower Inc.
(Van at al. 1998)

Linearcompressor
was inventedin Europeand Japan.
(Dolz,1954)

Bradshaw built a
prototype linearcompressor anddeveloped asimulation model.
(Bradshaw, 2012)

LG Inc. patented
and commercialized
several versions oflinear compressors

1980
1992

1950
First
mathematicalmodel of a linearcompressor.
(Pollak et al.
1979)

2013

2008
2000

2012

2002
Wisemotion
compressor technology
was developed byEmbraco© E.A. Groll & D. Ziviani

The university of
Oxford built one
linear compressor
with new magnetic
motor. (Liang at al.
2013)

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…..

2019

Cylinder Cooling with Internal Regeneration
Linear Compressor ModelingTransientPeriodic
steady-state© E.A. Groll & D. Ziviani

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Cylinder Cooling with Internal Regeneration
Example of Linear Compressor Performance Testing• Conducted testing of two commercially available linear compressors:•••

Refrigerator-freezer applications (cooling capacity ~200 W)
Embraco and LG
Refrigerant R134a© E.A. Groll & D. Ziviani

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Cylinder Cooling with Internal Regeneration
Linear Compressor Prototype with 3D Printed Cylinder• Linear compressor research focuses on• Scaling to larger capacities• Using 3D metal printing capabilities to include internal cooling channels• The same concept is being investigated for twin-screw compressors by 3D metal printing of the rotors
and housing© E.A. Groll & D. Ziviani

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Outline

Advanced Heat Pump Systems
Chemical-Looping Heat Pump

© E.A. Groll & D. Ziviani

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Chemical-Looping Heat Pump
Concept

CompoundReaction
FormulaIsopropanol(Fluid – A)

C3H8O

Acetone(Fluid – B)

C3H6O + H2

△𝑻𝒃𝒐𝒊𝒍𝒊𝒏𝒈 [K]26.38© E.A. Groll & D. Ziviani

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Chemical-Looping Heat Pump

Thermodynamic Model Results: Single-Loop

Sink Temperature = 35 oC

Sink Temperature = 20 oC© E.A. Groll & D. Ziviani

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Summary and Perspectives• Research efforts related to vapor compression systems for the HVAC&R
industry has rapidly increased over the last years• Phase-out and down of refrigerant• Recent advances in compressor and other vapor compression component
technologies and control strategies• An overview of several research topics concerning novel compression
concepts and unique cycle integration have been introduced• The aim is to move system performance closer to Carnot efficiency• Novel manufacturing techniques and computational resources will enable
next generation of vapor compression cycles• Scientific breakthroughs could lead to non-vapor compression technologies© E.A. Groll & D. Ziviani

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2020 Purdue Conferences© E.A. Groll & D. Ziviani

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Rankine 2020
Advances in Cooling, Heating and Power
Generation
Abstracts due 13th September 2019

Providing a unique opportunity to explore researchand developments in the closely related fields ofthermodynamic cycles, working fluids and theirapplications to refrigeration, air conditioning, heatpumps and power generation
University of Glasgow, Glasgow, Scotland
Sunday 26th July – Wednesday 29th July 2020
Visit www.rankine2020.com for full details© E.A. Groll & D. Ziviani

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US Workshop for IEA-HPT ExCo @ NIST, Gaithersburg, MD

Thank you!

© E.A. Groll & D. Ziviani

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Chemical-Looping Heat Pump

Membrane Electrode Assembly (MEA) Fabrication
Reinforced sPEEK Membrane

TeflonGasketCategory

Membrane Electrode Assembly (MEA)

Materials

MembraneGas Diffusion
Layer
Catalyst for Anode40% wt. PtRu (1:1) on
CarbonCatalyst for
Cathode50% wt. Cu on
CarbonGasketTeflon Gasket (25 𝜇 m)

© E.A. Groll & D. Ziviani

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TeflonGasket

Chemical-Looping Heat Pump
Experimental Setup

Electrochemical Cell: 20cm2 Fuel Cell Type

© E.A. Groll & D. Ziviani

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Chemical-Looping Heat Pump

Experimental Results: Linear Sweep Voltammetry (LSV)
Cell Area: 20 cm2© E.A. Groll & D. Ziviani

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Chemical-Looping Heat Pump

Parametric Studies: IEA performance targets© E.A. Groll & D. Ziviani

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Hybrid-Drive Variable Speed Compression• Market for residential air-source heat pumps in United States dominated by fixed-speed single-stagesystems• Meet minimum Seasonal Energy Efficiency Ratios (SEER)• Use compressors with PSC (permanent split capacitor) motors operated at fixed speeds• High efficiency systems have relatively low market penetration• Use variable speed brushless DC (BLDC) motors• Modulate capacity to match building load

• Why are not more variable-speed systems sold?
• Current minimum efficiency regulations can be met through lower cost approaches than variable speed e.g.
increasing heat exchanger surface area (Goetzler et al.)• Capacity modulation through variable speed compressors• Proven technology to improve seasonal efficiency of heat pumps• Typically uses a BLDC motor with an electronic drive• Losses from power electronics at full load can cause overall system efficiency to suffer and thermal management
to be needed© E.A. Groll & D. Ziviani

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