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Title: Characterization of Wrapped Coil Tank Water Heater during Charging/Discharging

Abstract

Heat pump water heaters (HPWH) are an energy efficient method for water heating compared to conventional electric water heaters. A wrapped coil around the water tank is often used as the condenser for the heat pump for such applications. Thermal stratification, caused by varying heat transfer rate from the condenser to the water depending on the phase of the refrigerant and the wrap configuration, is often observed inside the tank, especially for HPWHs using CO2 as the refrigerant. The current study investigates the impact of the charging/discharging process on thermal stratification. A series of simulations were conducted based on the draw patterns recommended by the DOE method of test for rating water heater performance. We also analyzed the water circulation patterns during charging/discharging process. The thermal stratification was adversely affected because of the circulation even when the Heat Pump (HP) was operational. It was observed that a relatively higher charge/discharge flow rate disrupts the thermal stratification quickly and thus lowers the supply water temperature. Furthermore, the duration of charging/discharging also plays an important role. It was noticed that the back flow has insignificant effect on the supply water temperature if charging/discharging time is relatively small. However, the effect was obviousmore » for larger water draw flow rates that last for longer time.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1407796
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: ASME 2017 IMECE International Mechanical Engineering Congress & Exposition - Tampa, Florida, United States of America - 11/3/2017 12:00:00 AM-11/9/2017 12:00:00 AM
Country of Publication:
United States
Language:
English

Citation Formats

Elatar, Ahmed F., Nawaz, Kashif, Shen, Bo, Baxter, Van D., and Abdelaziz, Omar. Characterization of Wrapped Coil Tank Water Heater during Charging/Discharging. United States: N. p., 2017. Web. doi:10.1115/IMECE2017-71818.
Elatar, Ahmed F., Nawaz, Kashif, Shen, Bo, Baxter, Van D., & Abdelaziz, Omar. Characterization of Wrapped Coil Tank Water Heater during Charging/Discharging. United States. doi:10.1115/IMECE2017-71818.
Elatar, Ahmed F., Nawaz, Kashif, Shen, Bo, Baxter, Van D., and Abdelaziz, Omar. Wed . "Characterization of Wrapped Coil Tank Water Heater during Charging/Discharging". United States. doi:10.1115/IMECE2017-71818. https://www.osti.gov/servlets/purl/1407796.
@article{osti_1407796,
title = {Characterization of Wrapped Coil Tank Water Heater during Charging/Discharging},
author = {Elatar, Ahmed F. and Nawaz, Kashif and Shen, Bo and Baxter, Van D. and Abdelaziz, Omar},
abstractNote = {Heat pump water heaters (HPWH) are an energy efficient method for water heating compared to conventional electric water heaters. A wrapped coil around the water tank is often used as the condenser for the heat pump for such applications. Thermal stratification, caused by varying heat transfer rate from the condenser to the water depending on the phase of the refrigerant and the wrap configuration, is often observed inside the tank, especially for HPWHs using CO2 as the refrigerant. The current study investigates the impact of the charging/discharging process on thermal stratification. A series of simulations were conducted based on the draw patterns recommended by the DOE method of test for rating water heater performance. We also analyzed the water circulation patterns during charging/discharging process. The thermal stratification was adversely affected because of the circulation even when the Heat Pump (HP) was operational. It was observed that a relatively higher charge/discharge flow rate disrupts the thermal stratification quickly and thus lowers the supply water temperature. Furthermore, the duration of charging/discharging also plays an important role. It was noticed that the back flow has insignificant effect on the supply water temperature if charging/discharging time is relatively small. However, the effect was obvious for larger water draw flow rates that last for longer time.},
doi = {10.1115/IMECE2017-71818},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2017},
month = {11}
}

Conference:
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