improving vapor compression system efficiency through

© E.A. Groll & D. Ziviani Slide 1/43

Improving Vapor Compression System Efficiency through Advanced Vapor Compression Technologies

Dr. Davide Ziviani

Research Assistant Professor

Associate Director of the Center for High Performance Buildings

November 12, 2019

Prof. Eckhard A. Groll

Reilly Professor of Mechanical Engineering

William E. and Florence E. Perry Head of Mechanical Engineering

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


• 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

Outline


Outline

Advanced Heat Pump Systems

Hybrid-Drive Variable-Speed Compression


Hybrid-Drive Variable Speed CompressionOverview

• 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 to

the PSC motor.

Separation of line electronic drive

circuitry using a relay. [Chretien et al.]

Electronic Drive Control [Chretien et al.]


Hybrid-Drive Variable Speed CompressionCompressor Testing

• Chretien et al. tested the variable speed control of PSC compressors on multiple residential heat pump systems 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 and

Rotary Compressor each

tested in an Air-Source

Heat Pump.


Hybrid-Drive Variable Speed CompressionCompressor Testing (cont’d)

• Preliminary results show stronger correlation between compressor speed and compressor efficiency for scroll than for rotary

• Degradation of performance• Full speed efficiency of scroll compressor at 60 Hz line power and identical operating point was 8% lower in

calorimeter testing after heat pump testing.

Volumetric and Overall Isentropic

Efficiency of a Scroll and Rotary

Compressor each tested in the

Calorimeter.


Hybrid-Drive Variable Speed CompressionSystem Testing

Test description

Air entering outdoor unit °F/°C


Air volume

rate Dry–bulb Wet–bulb Dry–bulb Wet–bulb

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


Air entering indoor unit °F/°C Compressor speed

Air volume rate

Dry–bulb Wet–bulb Dry–bulb Wet–bulb

A2 (required) 95.0 / 35.0 75.0 / 23.9 80.0 / 26.7 67.0 / 19.4 Maximum Full–load

B2 (required) 82.0 / 27.8 65.0 / 18.3 80.0 / 26.7 67.0 / 19.4 Maximum Full–load

EV (required) 87.0 / 30.669.0 / 20.6 80.0 / 26.7

67.0 / 19.4 IntermediateIntermediat

e

B1 (required) 82.0 / 27.8 65.0 / 18.3 80.0 / 26.7 67.0 / 19.4 Minimum Minimum

F1 (required) 67.0 / 19.4 53.5 / 11.9 80.0 / 26.7 67.0 / 19.4 Minimum Minimum

ANSI/AHRI Heat Pump Tests for fixed-speed compressor and constant volume indoor fan

ANSI/AHRI Heat Pump Tests for variable-speed compressor and constant indoor fan


Hybrid-Drive Variable Speed CompressionSystem Testing (cont’d)

Test Compressor Type

Outdoor Fan Motor

Variable Speed

ComponentsFixed Speed Components

SSHP1 Scroll PSC None CompressorOutdoor Fan

SSHP2 Rotary PSC None CompressorOutdoor Fan

VSHP1 Rotary PSC Compressor Outdoor Fan

VSHP2 Rotary PSC Compressor Outdoor Fan None

VSHP3 Rotary ECM Compressor Outdoor Fan None


Outline


Refrigerant Injected Compression with Economization


Refrigerant Injected Compression with EconomizationSystem Overview


R-410A vapor compression cycle with three injection ports (Mathison 2008)

Refrigerant Injected Compression with EconomizationMultiple Injection Ports


Refrigerant Injected Compression with EconomizationMultiple 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 and power consumption with number of injection

points for R-410A cycle operating at evaporating temperature of -20 °C and condensing

temperature of 50 °C


R-410A vapor compression cycle with continuous injection (Mathison 2008)

Refrigerant Injected Compression with EconomizationLimit of Economization


❑ 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

Refrigerant Injected Compression with EconomizationExperimental Work: single vs. two injection lines


❑ Hermetic scroll compressor for cold-climate heat pump (Bell et al. 2013)

Refrigerant Injected Compression with EconomizationExperimental Work: single vs. two injection lines


❑ ECU for cooling application in cold climates (Bahman et al. 2018)

Refrigerant Injected Compression with EconomizationExperimental Work: Military ECU with R-407C


Outline


Liquid Flooded Compression with Internal Regeneration


Liquid Flooded Compression with Internal RegenerationIntroduction

Cycle Schematic of Liquid Flooded Compression with Regeneration (Bell 2011)


Modeling ResultsCycles in T-s Diagram

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.

Liquid Flooded Compression with Internal RegenerationThermodynamic Modeling


• 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

Oil Injection #2Location of Oil Injection Ports

Liquid Flooded Compression with Internal RegenerationExperimental Results


• Cold-climate heat pump with oil-flooded compression (Ramaraj et al. 2014)• R-410A

• ISO 32 POE

• Tcd = 43.3 ℃; varied Tev

Liquid Flooded Compression with Internal RegenerationExperimental Results (cont’d)


Liquid Flooded Compression with Internal RegenerationExperimental Results: 𝑇cond = 43.3 ℃


Liquid Flooded Compression with Internal RegenerationSystem Results (Ramaraj et al., 2016)


Outline


Cold-Climate Heat Pumps


Cold-Climate Heat PumpsCycle Configurations (Bertsch and Groll, 2008)

• Simplified schematics of:a. Two-stage cycle with intercooler

b. Two-stage cycle with closed economizer

c. Cascade cycle

• Heating mode with ambient temperatures from -30 °C to 10 °C and supply temperatures from 40-60 °C


Cold-Climate Heat PumpsCycle Configurations (Bertsch and Groll, 2008)

• Cycle comparisons:• Heating mode supply temperatures of 50 °C


Cold-Climate Heat PumpsExperimental Work (Bertsch and Groll, 2008)


Cold-Climate Heat PumpsRecent Developments: Packaged Propane Heat Pump


Outline


Quasi-isothermal Compression with Cylinder Cooling and

Internal Regeneration


Cylinder Cooling with Internal Regeneration Concept Description


Cycles in T-s Diagram Cycles in p-h Diagram

Cylinder Cooling with Internal Regeneration Thermodynamic Diagrams: Effect of Intermediate Pressure


Compressor temperature rise versus intermediate pressure ratio

for different regenerator efficiencies

COP improvements compared toconventional vapor compression cycle

as a function of evaporating temperature

Cylinder Cooling with Internal Regeneration Parametric Studies


Linear compressor was invented in Europe and Japan. (Dolz,1954)

1980

First mathematical model of a linear compressor. (Pollak et al. 1979)

1992

Simulation model and several prototypes were developed by SunPower Inc. (Van at al. 1998)

2000 2002

LG Inc. patented and commercialized several versions of linear compressors

Wisemotion compressor technology was developed by Embraco

2008

Bradshaw built a prototype linear compressor and developed a simulation model. (Bradshaw, 2012)

2012 2019

…..2013

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

1950

Cylinder Cooling with Internal Regeneration Employing Linear Compressor


Transient

Periodic

steady-state

Cylinder Cooling with Internal Regeneration Linear Compressor Modeling


• Conducted testing of two commercially available linear compressors:• Refrigerator-freezer applications (cooling capacity ~200 W)

• Embraco and LG

• Refrigerant R134a

Cylinder Cooling with Internal Regeneration Example of Linear Compressor Performance Testing


• 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

Cylinder Cooling with Internal Regeneration Linear Compressor Prototype with 3D Printed Cylinder


Outline


Chemical-Looping Heat Pump


Chemical-Looping Heat PumpConcept

CompoundReaction Formula

△𝑻𝒃𝒐𝒊𝒍𝒊𝒏𝒈 [K]

Isopropanol (Fluid – A)

C3H8O

26.38Acetone

(Fluid – B)C3H6O + H2


Chemical-Looping Heat PumpThermodynamic Model Results: Single-Loop

Sink Temperature = 35 oC Sink Temperature = 20 oC


• 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

Summary and Perspectives


2020 Purdue Conferences


Rankine 2020Advances in Cooling, Heating and Power Generation

Abstracts due 13th September 2019

Providing a unique opportunity to explore research and developments in the closely related fields of thermodynamic cycles, working fluids and their applications to refrigeration, air conditioning, heat pumps and power generation

University of Glasgow, Glasgow, Scotland

Sunday 26th July – Wednesday 29th July 2020

Visit www.rankine2020.com for full details

http://www.rankine2020.com/


Thank you!

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


Chemical-Looping Heat PumpMembrane Electrode Assembly (MEA) Fabrication

Category Materials

Membrane

Gas Diffusion Layer

Catalyst for Anode40% wt. PtRu (1:1) on

Carbon

Catalyst for Cathode

50% wt. Cu on Carbon

Gasket Teflon Gasket (25 𝜇m)

Membrane Electrode Assembly (MEA)

Teflon

Gasket

Teflon

Gasket

Reinforced sPEEK Membrane


Chemical-Looping Heat PumpExperimental Setup

Electrochemical Cell: 20 cm2 Fuel Cell Type


Chemical-Looping Heat PumpExperimental Results: Linear Sweep Voltammetry (LSV)

Cell Area: 20 cm2


Chemical-Looping Heat PumpParametric Studies: IEA performance targets


Hybrid-Drive Variable Speed Compression

• Market for residential air-source heat pumps in United States dominated by fixed-speed single-stage systems

• 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

improving vapor compression system efficiency through

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