Application of Viper Energy Recovery Expansion Device in Transcritical Carbon Dioxide Refrigeration Cycle

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1 Application of Viper Energy Recovery Expansion Device in Transcritical Carbon Dioxide Refrigeration Cycle Riley Barta, Ph.D. Student PI: Prof. Eckhard A. Groll May 16 th,

2 Overview q Introduction q The Viper Expander q Test Stand Design q Theoretical Analysis q Experimental Results q Conclusions and Future Work 2

3 Overview Goal: Recover expansion energy that is not utilized using traditional expansion valves Motivation: Increase understanding of natural refrigerants and devices that can be used to increase efficiency of refrigeration cycles Method: Utilize the Viper Expander to harness expansion work by moving the expansion process from isenthalpic towards isentropic 3

4 Transcritical CO # Cycle 3 2 q Traditional Expansion Valve: h % = h ' (isenthalpic) 4 1 4

5 Transcritical CO # Cycle 3 2 q Traditional Expansion Valve: h % = h ' (isenthalpic) q Isentropic Expansion h % h ') 4s 4 1 5

6 Transcritical CO # Cycle 3 2 q Traditional Expansion Valve: h % = h ' (isenthalpic) q Isentropic Expansion h % h ') 4s 4v 4 1 q Expansion Through Viper h % h '* More Isentropic Expansion Work from 1 st Law W + Q = m h 6

7 Transcritical CO # Cycle 3 2 q Traditional Expansion Valve: h % = h ' (isenthalpic) q Isentropic Expansion h % h ') 4s 4v 4 1 q Expansion Through Viper h % h '* More Isentropic Expansion Work from 1 st Law W + Q = m h η 3),53678 = h % h '* h % h ') W = m (h % h '* ) 7

8 Literature Review q Yang (2009) - CO 2 Refrigeration System Ø Experimentally tested a double acting rotary vane expander/generator Ø Increased COP by 11 14% q Elbel and Hrnjak (2004) Transcritical CO 2 System Ø Tested a prototype ejector with integrated needle for high-side pressure control Ø Improvements in COP and cooling capacity were 7% and 8%, respectively 8

Literature Review q Baek and Groll (2005) Transcritical CO 2 System Ø Tested a piston cylinder expander known as the Expansion Device With Output Work (ED-WOW) Ø Improvement in COP was

9 Literature Review q Baek and Groll (2005) Transcritical CO 2 System Ø Tested a piston cylinder expander known as the Expansion Device With Output Work (ED-WOW) Ø Improvement in COP was % q He (2009) R410A Refrigeration System Ø Experimentally tested a Pelton-type expander Ø Improvements in COP and cooling capacity were 6.5% and 5.4%, respectively He (2009) 9

10 Overview q Introduction q The Viper Expander q Test Stand Design q Theoretical Analysis q Experimental Results q Conclusions and Future Work 10

generator q Utilize energy released from transition from

11 The Viper Expander q High pressure refrigerant converted to high-velocity stream imparted on an impeller to spin the generator q Utilize energy released from transition from supercritical into 2-phase region Nozzle Impeller Generator Viper Rectifier Motor (ECM) 11

12 The Viper Expander Flow Direction q Currently, impeller utilizes a Pelton Wheel design q Nozzle is fixed-diameter, designed for mass flow rates attainable with current test setup 12

13 Overview q Introduction q The Viper Expander q Test Stand Design q Theoretical Analysis q Experimental Results q Conclusions and Future Work 13

14 Test Stand Design P Hot-gas Bypass Test Stand Ø Independently control all three parameters surrounding compressor 1. P?3)@AB8C7 2. P EF@G3HI 3. T EF@G3HI h 14

15 Test Stand Design P Hot-gas Bypass Test Stand Viper placed here Ø Control all three parameters surrounding compressor Ø Place Viper in liquid expansion line to simulate realistic operating conditions h 15

16 Test Stand Design P Viper placed here Hot-gas Bypass Test Stand, Mass and Energy Balance m Lh L = m Mh M + m Nh N (1) m L = m M + m N (2) Ø Result: Calculate the mass flow rate through the Viper h 16

17 Test Stand Design 17

18 Overview q Introduction q The Viper Expander q Test Stand Design q Theoretical Analysis q Experimental Results q Conclusions and Future Work 18

19 Theoretical Analysis q Purpose: Understand how expander operating conditions can be simulated in hot-gas bypass test stand q Process: 1. Take design operating conditions 2. Add pressure drop and hot-gas bypass energy and mass balance to model 3. Calculate Viper isentropic efficiency 19

20 Theoretical Results P [kpa] L 7N 4H 5N C 5H 6N 23.5 C p-h, CarbonDioxide, OP4 p Cond C 1H 6H 3N 2H 4N 3H 2N C 2L 3L -0.7 kj/kg-k q 2-stage transcritical CO # cycle q Cycle input into 2 hot-gas bypass stand cycles 1. High-side 2. Low-side 2 x L 8N C Low-Side, "L" High-Side, "H" N. Czapla, "N" h [kj/kg] 9N 1L,N Hot Gas Bypass 6L q Hot-gas bypass and pressure drop shown Ø Predict how well stand can replicate operating conditions 20

21 Theoretical Results From Hot-gas Bypass Valve m N, h N From Liquid Valve m M, h M To Compressor Inlet m L, h L q Parameters of chosen, high-side operating conditions analysis: Ø T TFGUHH8 = 37.8 Ø T YIUHH8 = 1.7 Ø m L = \C ) Ø η 3),]H^687))H8 = 0.7 Ø η 3),53678 = 0.5 q Results: Ø m M = \C ) Ø W = kw Ø COP Improvement of 6.8 % when placed on low-side 21

22 Overview q Introduction q The Viper Expander q Test Stand Design q Theoretical Analysis q Experimental Results q Conclusions and Future Work 22

23 Experimental Results P [kpa] Established Cycle Comparison, mm Nozzle Established Cycle, "e" mm Nozzle, "n" 4e 4n 23.5 C C C 3n C 3e 2n q Testing Method: 2e 1. Establish steadystate cycle with test stand valves 2. Slowly engage Viper, eventually sending 100% of m M through the Viper 3. Adjust superheat to T Eb = 10 ± x C 5n 1n 6n 5e 6e 1e h [kj/kg] 4. Observe Viper outputs, calculate Viper isentropic efficiency 23

24 Experimental Results q m L = 42.0 C ) R744, mm Viper Nozzle C C C q m M = 13.1 C ) q P ef6biu78 = 4489 kpa q W = 11.9 W P [kpa] 23.5 C q Speed = 5790 rpm Ø η is,viper = 6. 5 % C 2 x h [kj/kg] 24

25 Overview q Introduction q The Viper Expander q Test Stand Design q Theoretical Analysis q Experimental Results q Conclusions and Future Work 25

26 Conclusions and Future Work q Test stand is reaching desired operating conditions q Experimental isentropic efficiency is lower than theoretically assumed q Pelton wheel design is not optimal for these operating conditions with CO # Ø Turbine re-design being pursued q Nozzle design is also in question, and further design efforts are being pursued 26

27 Questions? Thank You 27

Choked Flow Characteristics of Subcritical Refrigerant Flowing Through Converging-Diverging Nozzles

Entropy 2014, 16, 5810-5821; doi:10.3390/e16115810 Article OPEN ACCESS entropy ISSN 1099-4300 www.mdpi.com/journal/entropy Choked Flow Characteristics of Subcritical Refrigerant Flowing Through Converging-Diverging