Performance optimization of CO2 heat pump water heater

Nawaz, Kashif; Shen, Bo; Elatar, Ahmed; Baxter, Van D.; Abdelaziz, Omar

doi:10.1016/j.ijrefrig.2017.09.027

Title: Performance optimization of CO₂ heat pump water heater

Journal Article · Sat Oct 14 00:00:00 EDT 2017 · International Journal of Refrigeration

DOI:https://doi.org/10.1016/j.ijrefrig.2017.09.027· OSTI ID:1414698

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Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

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.

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Research Organization:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: AC05-00OR22725

OSTI ID:: 1414698

Alternate ID(s):: OSTI ID: 1549396

Journal Information:: International Journal of Refrigeration, Vol. 85, Issue C; ISSN 0140-7007

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 48 works

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Title: Performance optimization of CO2 heat pump water heater

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