Abstract
This paper reports the effects of low- cost immersed condensers on the performance of a heat pump water heater (HPWH) that does not require a water- circulating pump. The proposed design is based on the immersion of an L-style condenser coil through an opening in the top of the water tank. The novel design aims to eliminate the need for the water-circulating pumps, thereby substantially improving efficiency and reducing costs and maintenance of the HPWH system. Comprehensive compu-tational fluid dynamics (CFD) simulations and experimental tests were performed, and the results showed that the CFD simu-lations were close to the experimental data. Further results confirm that the L-style condenser can introduce buoyancy-driven flow and eliminate temperature stratification in the studied HPWH water tank, thereby improving the heat transfer coefficient and coefficient of performance (COP) of the HPWH. The testing results further showed that the L-style condenser enabled more than 53% higher COP and 400% higher heat transfer coefficient compared with the straight vertical condenser, and achieved much faster water heating. Furthermore, the effects of immersed condensers with different circuits on the HPWH performance were evaluated and compared. All results indicate that the current energy-saving and inexpensive HPWH technology is technically valid, and the benefits of performance improvement and low cost are attractive in future HPWH design.
| Original language | English |
|---|---|
| Pages (from-to) | 737-748 |
| Number of pages | 12 |
| Journal | ASHRAE Transactions |
| Volume | 131 |
| Issue number | Pt2 |
| DOIs | |
| State | Published - 2025 |
| Event | ASHRAE Annual Conference, 2025 - Phoenix, United States Duration: Jun 21 2025 → Jun 25 2025 |
Funding
The authors appreciate the U.S. Department of Energy (DOE) and the Tennessee Valley Authority (TVA) for jointly spon-soring this project. The authors also appreciate Heatcraft and Wolvere for generously providing the vent tube used in the test unit and Tecumseh for providing the rotary compressors for the heat pump. The authors also appreciate Olivia Shafer for technical editing. Notice: This manuscript has been authored by UT-Battelle LLC under contract DE-AC05-00OR22725 with the U.S. Depart-ment of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).