Performance optimization of CO2 heat pump water heater
Abstract
A preliminary analysis was conducted to analyze the performance of a heat pump water heater (HPWH) that uses CO2 as the refrigerant. A model to predict the performance was developed and calibrated based on the experimental data for an existing HPWH using a CO2 refrigerant. The calibrated model was then used to run a parametric analysis in which factors such as water supply temperature, water circulation rate, tank stratification, and condenser configuration were considered. The performance of a commercial CO2 system was compared with that of a similar system using R-134a as the refrigerant. It was found that CO2 HPWH performance was comparable to that of an R-134a HPWH, more so for a separated gas cooler configuration. For comparable performance, the compressor size and the tube-in-tube heat exchanger (condenser/gas cooler) size were compared for CO2- and R-134a-based systems. Finally, the impact of the water circulation rate on the water temperature stratification in the tank, an essential requirement for higher performance for CO2 HPWH systems was also investigated.
- Publication Date:
- Research Org.:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Org.:
- USDOE
- OSTI Identifier:
- 1414698
- Alternate Identifier(s):
- OSTI ID: 1549396
- Grant/Contract Number:
- AC05-00OR22725
- Resource Type:
- Accepted Manuscript
- Journal Name:
- International Journal of Refrigeration
- Additional Journal Information:
- Journal Volume: 85; Journal Issue: C; Journal ID: ISSN 0140-7007
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 42 ENGINEERING; 32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; Heat pump; Water heater; Carbon dioxide; Alternative refrigerants
Citation Formats
Nawaz, Kashif, Shen, Bo, Elatar, Ahmed, Baxter, Van D., and Abdelaziz, Omar. Performance optimization of CO2 heat pump water heater. United States: N. p., 2017.
Web. doi:10.1016/j.ijrefrig.2017.09.027.
Nawaz, Kashif, Shen, Bo, Elatar, Ahmed, Baxter, Van D., & Abdelaziz, Omar. Performance optimization of CO2 heat pump water heater. United States. https://doi.org/10.1016/j.ijrefrig.2017.09.027
Nawaz, Kashif, Shen, Bo, Elatar, Ahmed, Baxter, Van D., and Abdelaziz, Omar. Sat .
"Performance optimization of CO2 heat pump water heater". United States. https://doi.org/10.1016/j.ijrefrig.2017.09.027. https://www.osti.gov/servlets/purl/1414698.
@article{osti_1414698,
title = {Performance optimization of CO2 heat pump water heater},
author = {Nawaz, Kashif and Shen, Bo and Elatar, Ahmed and Baxter, Van D. and Abdelaziz, Omar},
abstractNote = {A preliminary analysis was conducted to analyze the performance of a heat pump water heater (HPWH) that uses CO2 as the refrigerant. A model to predict the performance was developed and calibrated based on the experimental data for an existing HPWH using a CO2 refrigerant. The calibrated model was then used to run a parametric analysis in which factors such as water supply temperature, water circulation rate, tank stratification, and condenser configuration were considered. The performance of a commercial CO2 system was compared with that of a similar system using R-134a as the refrigerant. It was found that CO2 HPWH performance was comparable to that of an R-134a HPWH, more so for a separated gas cooler configuration. For comparable performance, the compressor size and the tube-in-tube heat exchanger (condenser/gas cooler) size were compared for CO2- and R-134a-based systems. Finally, the impact of the water circulation rate on the water temperature stratification in the tank, an essential requirement for higher performance for CO2 HPWH systems was also investigated.},
doi = {10.1016/j.ijrefrig.2017.09.027},
journal = {International Journal of Refrigeration},
number = C,
volume = 85,
place = {United States},
year = {Sat Oct 14 00:00:00 EDT 2017},
month = {Sat Oct 14 00:00:00 EDT 2017}
}
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Works referencing / citing this record:
Comparison of Transcritical CO2 and Conventional Refrigerant Heat Pump Water Heaters for Domestic Applications
journal, February 2019
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