Dynamic modeling and characteristic analysis of a two-stage vapor injection heat pump system under frosting conditions. (December 2017)

• Record Type: Journal Article
• Authors: Qiao, Hongtao; Aute, Vikrant; Radermacher, Reinhard
• Is Part Of: International journal of refrigeration. Volume 84(2017)
• Page Start: 181
• Page End: 197
• Publication Date: 2017-12
• Subjects: Modeling -- Frost -- Air flow distribution -- TXV hunting -- Vapor injection -- Heat pump; Modélisation -- Givre -- Distribution d'air -- Pompage de détendeurs thermostatiques -- Injection de vapeur -- Pompe à chaleur; Refrigeration and refrigerating machinery -- Periodicals; 621.56
• DOI: 10.1016/j.ijrefrig.2017.08.020
• Languages: English
• ISSNs: 0140-7007

Abstract

Highlights: Frosting transients of an FTVI heat pump system are simulated. The refrigerant loop is modeled following a fully dynamic approach. Non-uniform frost growth and air flow redistribution are modeled. System hunting phenomenon is well captured in the simulation. Favorable agreement with experimental data demonstrates model fidelity. Abstract: This paper presents a distributed-parameter dynamic heat exchanger model integrated with a detailed frost growth model to account for non-uniform frost formation on a fan-supplied finned-tube coil. A novel, iteration-free approach is proposed to solve the air flow redistribution by linearizing a system of non-linear air pressure drop equalization equations, resulting in a significant improvement in the computational efficiency. As a continuation and extension of our previous work, the developed models along with the component models described in Qiao et al. (2015a) are applied for the first time to explore the frosting dynamics of a two-stage flash tank vapor injection heat pump system. It is found that frost formation degrades the heating performance of the system substantially. Meanwhile, the simulation indicates that air and refrigerant flow maldistribution, resulting from non-uniform frost growth on the outdoor heat exchanger, can lead to unstable system hunting behavior. Comparisons between the simulation results and experimental data indicate that the proposed models can reasonably predict the time-dependent heat transfer and fluid flow phenomena of the system.