Comparing R1233zd and R245fa forLow Temperature ORC Applications 

BALA  V.  DATLA  

VERD ICORP

TALLAHASSEE ,   FL ,  USA  

JOOST BRASZ

SYRACUSE  TURBOMACHINERY

SYRACUSE ,  NY,  USA

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014

Brief Introduction to ORC Systems 

R245fa as working fluid in ORC’s

R1233zd as working fluid in ORC’s

Comparing R1233zd to R245fa

Summary

Overview of the Talk

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 2

ORC System Overview

Heat InputHeat RejectedPower Extraction

Flow Circulation

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 3

Why R245fa as working fluid?

Power density of R245fa at elevated temperatures matches that of R134a based refrigeration compressors.

Use existing R134a based compressor

Reduction in development and production time and cost of the turbo generator.

Moderate GWP of 950

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 4

75 kW ORC system using R245fa

R134a based 

Compressor

Mechanical Design Pressure of 2170 kPa

R245fa based Turbo Generator

Inlet Pressure 2000 kPaSaturated Evaporation 

Temperature (SET) 121.9 °C

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 5

75 kW ORC system using R245fa

Rotor operating at 35000 RPM

75 kW at shaft

Isentropic Aero efficiency 80%

Fixed vane Nozzle

Magnetic Bearings

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 6

75 kW ORC system using R245fa

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Thermal Efficiency based on Generator Output is 12.9%

75 kW ORC system using R245fa

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 8

R1233zd as drop in for the 75 kW R245fa ORC System

Fluid Property Units R1233zd R245faMolar Mass [kg/kmol] 130.5 134.1Critical Pressure [kPa] 3570.9 3651.2Critical Temperature

[C] 165.60 154.01

GWP [-] 6 950Boiling Point @ 1 atm

[C] 18.7 15.1

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 9

Expander Inlet/Exit 

Expander inlet is limited by Design PressureExit is determined by the ambient

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 10

R1233zd as drop in for the 75 kW R245fa ORC System

R134a based 

Compressor

Mechanical Design Pressure of 2170 kPa

R245fa based Turbo Generator

Inlet Pressure 2000 kPaSaturated Evaporation 

Temperature (SET) 121.9 °C

R1233zd based Turbo Generator

Inlet Pressure 2000 kPaSaturated Evaporation 

Temperature (SET) 132.5 °C

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R1233zd as drop in for the 75 kW R245fa ORC System

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 12

Thermal Efficiency based on Generator Output is 14.0%

R1233zd as drop in for the 75 kW R245fa ORC System

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 13

Comparing R1233zd to R245fa

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 14

Comparing R1233zd to R245fa

System Performance Comparison Units R1233zd R245faMechanical Shaft Power Output [kW] 80.4 74.8Gross Electric Power Out from Generator [kW.e] 74.0 68.9Total Heat Input [kW.th] 528.4 534.6Total Heat Rejected [kW.th] 459.7 470.8Pump Power [kW.e] 6.0 5.7Energy Balance [kW] 0.00 -0.07Condenser Fan Power based on 0.012 kW.e/kW.th [kW.e] 5.5 5.6Net Power Out of Air Cooled System [kW.e] 60.3 55.4Thermal Efficiency based on Shaft Power [%] 15.2% 14.0%Thermal Efficiency based on Generator Power [%] 14.0% 12.9%Thermal Efficiency based on Air Cooled Net Power [%] 11.4% 10.4%

Cycle analysis shows use of R1233zd would result in gain of 8.7% in efficiency compared to R245fa

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Comparing R1233zd to R245fa

Turbine Parameters Units R1233zd R245faInlet Temperature [°C] 135.0 124.4Inlet Pressure [kPa] 2000 2000Outlet Temperature [°C] 59.1 59.0Outlet Pressure [kPa] 167.7 191.3Pressure Ratio [-] 11.93 10.45Spouting Velocity [m/s] 309.5 295.9Mass Flow Rate [kg/s] 2.10 2.13Exit Volume Flow Rate [m3/s] 0.253 0.218Rotor Speed [rpm] 36628 35000Shaft Power [kW] 80.4 75.0

15TH INTERNATIONAL REFRIGERATION AND AIR CONDITIONING CONFERENCE AT PURDUE, JULY 14-17, 2014 16

R1233zd Drop In for existing R245fa system

Expander Heat Source Fluid Temperatures Heat Exchangers Pump Material Compatibility

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Summary R1233zd can be used in existing R245fa based ORC turbine with little or no

modifications. While care should be taken for components in contact with theworking fluid and be checked for material compatibility.

With the a reasonably close spouting velocity of R1233zd compared to R245fa atdesign conditions, a fixed speed machine would have a comparable turbineefficiency to that of variable speed machine when R1233zd is used as the drop influid.

The use of low GWP R1233zd for low temperature ORC system shows promising8.7% higher cycle efficiency when compared to an equivalent R245fa basedsystem.

This gain in performance of R1233zd when compared to R245fa system shouldhelp realize proportional reduction in cost/kW and ROI time over existing R245famachines.

R1233zd with its low GWP and high cycle efficiency when compared to R245facould make it a great candidate for low GWP, low temperature ORC systems.

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