TY - GEN
T1 - Modeling improvements for air-source heat pumps using different expansion devices at varied charge levels - Part II
AU - Shen, Bo
AU - Groll, Eckhard A.
AU - Braun, James E.
PY - 2011
Y1 - 2011
N2 - This paper describes steady-state performance simulations performed on a 3-ton R-22 split heat pump in heating mode. In total, 150 steady-state points were simulated, which covers refrigerant charge levels from 70% to 130% relative to the nominal value, the outdoor temperatures at 17°F (-8.3 °C), 35°F (1.7°C) and 47°F (8.3°C), indoor airflow rates from 60% to 150% of the rated airflow rate, and two types of expansion devices (fixed orifice and thermostatic expansion valve [TXV]). A charge tuning method, which is to calibrate the charge inventory model based on measurements at two operation conditions, was applied and shown to improve the system simulation accuracy significantly over an extensive range of charge levels. In addition, we discuss the effects of using a suction line accumulator in modeling a heat pump system using either a fixed orifice or thermal expansion valve. Last, we identify the issue of refrigerant mass flow mal-distribution at low charge levels and propose an improved modeling approach.
AB - This paper describes steady-state performance simulations performed on a 3-ton R-22 split heat pump in heating mode. In total, 150 steady-state points were simulated, which covers refrigerant charge levels from 70% to 130% relative to the nominal value, the outdoor temperatures at 17°F (-8.3 °C), 35°F (1.7°C) and 47°F (8.3°C), indoor airflow rates from 60% to 150% of the rated airflow rate, and two types of expansion devices (fixed orifice and thermostatic expansion valve [TXV]). A charge tuning method, which is to calibrate the charge inventory model based on measurements at two operation conditions, was applied and shown to improve the system simulation accuracy significantly over an extensive range of charge levels. In addition, we discuss the effects of using a suction line accumulator in modeling a heat pump system using either a fixed orifice or thermal expansion valve. Last, we identify the issue of refrigerant mass flow mal-distribution at low charge levels and propose an improved modeling approach.
UR - https://www.scopus.com/pages/publications/84856639295
M3 - Conference contribution
AN - SCOPUS:84856639295
SN - 9781936504121
T3 - ASHRAE Transactions
SP - 552
EP - 564
BT - ASHRAE Transactions - Papers Presented at the 2011 Annual Conference in Montreal, Quebec, Canada of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.
T2 - 2011 ASHRAE Annual Conference
Y2 - 25 June 2011 through 29 June 2011
ER -