Transcritical CO2 Heat Pump Simulation Model and Validation for Simultaneous Cooling and Heating
In the present study, a steady-state simulation model
has been developed to evaluate the system performance of a
transcritical carbon dioxide heat pump system for simultaneous water
cooling and heating. Both the evaporator (including both two-phase
and superheated zone) and gas cooler models consider the highly
variable heat transfer characteristics of CO2 and pressure drop. The
numerical simulation model of transcritical CO2 heat pump has been
validated by test data obtained from experiments on the heat pump
prototype. Comparison between the test results and the model
prediction for system COP variation with compressor discharge
pressure shows a modest agreement with a maximum deviation of
15% and the trends are fairly similar. Comparison for other operating
parameters also shows fairly similar deviation between the test
results and the model prediction. Finally, the simulation results are
presented to study the effects of operating parameters such as,
temperature of heat exchanger fluid at the inlet, discharge pressure,
compressor speed on system performance of CO2 heat pump, suitable
in a dairy plant where simultaneous cooling at 4oC and heating at
73oC are required. Results show that good heat transfer properties of
CO2 for both two-phase and supercritical region and efficient
compression process contribute a lot for high system COPs.
[1] P. Neksa, "CO2 heat pump systems," Int. Journal of Refrigeration, vol.
25, pp. 421-427, 2002.
[2] L. Cecchinato, M. Corradi, E. Fornasieri and L. Zamboni, "Carbon
dioxide as refrigerant for tap water heat pumps: A comparison with the
traditional solution," Int. Journal of Refrigeration, vol. 28, pp. 1250-
1258, 2005.
[3] R. Yokoyama, T. Shimizu, K. Ito and K. Takemura, "Influence of
ambient temperatures on performance of a CO2 heat pump water heating
system," Energy, vol. 32, pp. 388-398, 2007.
[4] S. D White, M. G. Yarrall, D. J. Cleland and R. A. Hedley, "Modelling
the performance of a transcritical CO2 heat pump for high temperature
heating," Int. Journal of Refrigeration, vol. 25, pp. 479-486, 2002.
[5] S. G. Kim, Y. J. Kim, G. Lee and M. S. Kim, "The performance of a
transcritical CO2 cycle with an internal heat exchanger for hot water
heating," Int. Journal of Refrigeration, vol. 28, pp. 1064-1072, 2005.
[6] J. Sarkar, S. Bhattacharyya and M. Ramgopal, "Simulation of a
transcritical CO2 heat pump cycle for simultaneous cooling and heating
applications," Int. Journal of Refrigeration, vol. 29, pp. 735-743, 2006.
[7] N. Agrawal and S. Bhattacharyya, "Optimized transcritical CO2 heat
pumps: Performance comparison of capillary tubes against expansion
valves," Int. Journal of Refrigeration, vol. 31, pp. 388-395, 2008.
[8] T. M. Ortiz, D. Li and E. A. Groll, "Evaluation of the performance
potential of CO2 as a refrigerant in air-to-air air conditioners and heat
pumps: system modelling and analysis," ARTI final report, no.
21CR/610-10030, 2003.
[9] V. Gnielinski, "New equations for heat and mass transfer in turbulent
pipe and channel flow," International Chemical Engineering, vol. 16,
pp. 359-366, 1976.
[10] S. S. Pitla, E. A. Groll and S. Ramadhyani, "New correlation to predict
the heat transfer coefficient during in-tube cooling of turbulent
supercritical CO2," Int. Journal of Refrigeration, vol. 25, pp. 887-895,
2002.
[11] X. Fang, C. W. Bullard and P. S. Hrnjak, "Heat transfer and pressure
drop of gas coolers," ASHRAE Transactions, vol. 107, pp. 255-266,
2001.
[12] S. H. Yoon, E. S. Cho, Y. W. Hwang, M. S. Kim, K Min and Y. Kim,
"Characteristics of evaporative heat transfer and pressure drop of carbon
dioxide and correlation development," Int. Journal of Refrigeration, vol.
27, pp. 111-119, 2004.
[13] J. Sarkar, S. Bhattacharyya and M. Ramgopal, "Transcritical CO2 heat
pump prototype development for simultaneous water cooling and
heating," International Congress of Refrigeration, Beijing, 2007.
[1] P. Neksa, "CO2 heat pump systems," Int. Journal of Refrigeration, vol.
25, pp. 421-427, 2002.
[2] L. Cecchinato, M. Corradi, E. Fornasieri and L. Zamboni, "Carbon
dioxide as refrigerant for tap water heat pumps: A comparison with the
traditional solution," Int. Journal of Refrigeration, vol. 28, pp. 1250-
1258, 2005.
[3] R. Yokoyama, T. Shimizu, K. Ito and K. Takemura, "Influence of
ambient temperatures on performance of a CO2 heat pump water heating
system," Energy, vol. 32, pp. 388-398, 2007.
[4] S. D White, M. G. Yarrall, D. J. Cleland and R. A. Hedley, "Modelling
the performance of a transcritical CO2 heat pump for high temperature
heating," Int. Journal of Refrigeration, vol. 25, pp. 479-486, 2002.
[5] S. G. Kim, Y. J. Kim, G. Lee and M. S. Kim, "The performance of a
transcritical CO2 cycle with an internal heat exchanger for hot water
heating," Int. Journal of Refrigeration, vol. 28, pp. 1064-1072, 2005.
[6] J. Sarkar, S. Bhattacharyya and M. Ramgopal, "Simulation of a
transcritical CO2 heat pump cycle for simultaneous cooling and heating
applications," Int. Journal of Refrigeration, vol. 29, pp. 735-743, 2006.
[7] N. Agrawal and S. Bhattacharyya, "Optimized transcritical CO2 heat
pumps: Performance comparison of capillary tubes against expansion
valves," Int. Journal of Refrigeration, vol. 31, pp. 388-395, 2008.
[8] T. M. Ortiz, D. Li and E. A. Groll, "Evaluation of the performance
potential of CO2 as a refrigerant in air-to-air air conditioners and heat
pumps: system modelling and analysis," ARTI final report, no.
21CR/610-10030, 2003.
[9] V. Gnielinski, "New equations for heat and mass transfer in turbulent
pipe and channel flow," International Chemical Engineering, vol. 16,
pp. 359-366, 1976.
[10] S. S. Pitla, E. A. Groll and S. Ramadhyani, "New correlation to predict
the heat transfer coefficient during in-tube cooling of turbulent
supercritical CO2," Int. Journal of Refrigeration, vol. 25, pp. 887-895,
2002.
[11] X. Fang, C. W. Bullard and P. S. Hrnjak, "Heat transfer and pressure
drop of gas coolers," ASHRAE Transactions, vol. 107, pp. 255-266,
2001.
[12] S. H. Yoon, E. S. Cho, Y. W. Hwang, M. S. Kim, K Min and Y. Kim,
"Characteristics of evaporative heat transfer and pressure drop of carbon
dioxide and correlation development," Int. Journal of Refrigeration, vol.
27, pp. 111-119, 2004.
[13] J. Sarkar, S. Bhattacharyya and M. Ramgopal, "Transcritical CO2 heat
pump prototype development for simultaneous water cooling and
heating," International Congress of Refrigeration, Beijing, 2007.
@article{"International Journal of Mechanical, Industrial and Aerospace Sciences:52861", author = "Jahar Sarkar", title = "Transcritical CO2 Heat Pump Simulation Model and Validation for Simultaneous Cooling and Heating", abstract = "In the present study, a steady-state simulation model
has been developed to evaluate the system performance of a
transcritical carbon dioxide heat pump system for simultaneous water
cooling and heating. Both the evaporator (including both two-phase
and superheated zone) and gas cooler models consider the highly
variable heat transfer characteristics of CO2 and pressure drop. The
numerical simulation model of transcritical CO2 heat pump has been
validated by test data obtained from experiments on the heat pump
prototype. Comparison between the test results and the model
prediction for system COP variation with compressor discharge
pressure shows a modest agreement with a maximum deviation of
15% and the trends are fairly similar. Comparison for other operating
parameters also shows fairly similar deviation between the test
results and the model prediction. Finally, the simulation results are
presented to study the effects of operating parameters such as,
temperature of heat exchanger fluid at the inlet, discharge pressure,
compressor speed on system performance of CO2 heat pump, suitable
in a dairy plant where simultaneous cooling at 4oC and heating at
73oC are required. Results show that good heat transfer properties of
CO2 for both two-phase and supercritical region and efficient
compression process contribute a lot for high system COPs.", keywords = "CO2 heat pump, dairy system, experiment,
simulation model, validation.", volume = "2", number = "7", pages = "882-6", }