TY - JOUR
T1 - CFD solution and experimental testing of buoyancy-driven convection caused by condensers immersed in a water tank of HPWH
AU - Gao, Zhiming
AU - Mei, Viung C.
AU - Chen, Fang C.
PY - 2003
Y1 - 2003
N2 - Heat pump water heaters can cut electricity consumption, comparing with the conventional electric resistant water heating tanks by half. A conventional heat pump water heater (HPWH) requires a water circulating pump to sample water temperature every 15 minutes in the tank and to draw water to a condenser-water heat exchanger outside the tank, if water temperature is below the set point. The pump would be on at least once every 15 minutes, 24 hours a day. The novel design presented in this study was to insert the condenser coil through the opening on the top of the water tank. This design eliminated the need of the water circulating pumps, and thus greatly improved the reliability of the HPWH systems. Two types of condenser coil designs were considered; one was a bayonet tube (tube-in-tube) and one was the "U" tube. Previous test data indicated that "U" tube design performed better than the bayonet tube condenser coil, and thus only "U" tube condenser coil was considered in the study. With straight "U" tubes inserted into the tank, it was found that the convective heat transfer was not strong enough to break water temperature stratification in the tank, which resulted in a temperature differential of 16°C (30°F) from top to bottom. However, when the coil was built in "L" shape, the water stratification disappeared. A computational fluid dynamics code, CFD, was used to study the straight and L shaped condenser coils. Results from CFD simulation were compared with the experimental data and found they were close to each other.
AB - Heat pump water heaters can cut electricity consumption, comparing with the conventional electric resistant water heating tanks by half. A conventional heat pump water heater (HPWH) requires a water circulating pump to sample water temperature every 15 minutes in the tank and to draw water to a condenser-water heat exchanger outside the tank, if water temperature is below the set point. The pump would be on at least once every 15 minutes, 24 hours a day. The novel design presented in this study was to insert the condenser coil through the opening on the top of the water tank. This design eliminated the need of the water circulating pumps, and thus greatly improved the reliability of the HPWH systems. Two types of condenser coil designs were considered; one was a bayonet tube (tube-in-tube) and one was the "U" tube. Previous test data indicated that "U" tube design performed better than the bayonet tube condenser coil, and thus only "U" tube condenser coil was considered in the study. With straight "U" tubes inserted into the tank, it was found that the convective heat transfer was not strong enough to break water temperature stratification in the tank, which resulted in a temperature differential of 16°C (30°F) from top to bottom. However, when the coil was built in "L" shape, the water stratification disappeared. A computational fluid dynamics code, CFD, was used to study the straight and L shaped condenser coils. Results from CFD simulation were compared with the experimental data and found they were close to each other.
UR - http://www.scopus.com/inward/record.url?scp=1842479317&partnerID=8YFLogxK
U2 - 10.1115/IMECE2003-42655
DO - 10.1115/IMECE2003-42655
M3 - Conference article
AN - SCOPUS:1842479317
SN - 1071-6947
VL - 43
SP - 33
EP - 38
JO - American Society of Mechanical Engineers, Manufacturing Engineering Division, MED
JF - American Society of Mechanical Engineers, Manufacturing Engineering Division, MED
T2 - 2003 ASME International Mechanical Engineering Congress
Y2 - 15 November 2003 through 21 November 2003
ER -