Abstract:

This paper presents a detailed transient simulation model to analyze the dynamic behavior of refrigerant-oil mixtures in vapor compression systems, with a particular focus on air-source heat pump operation during heating-mode cycling. A modular simulation framework is developed, incorporating refined sub-models for the compressor, heat exchangers, accumulator, and connecting tubing. Empirical correlations are applied to predict heat transfer coefficients, pressure drops, and oil retention characteristics across varying operating conditions. The simulation results reveal pronounced transient imbalances in refrigerant and oil distribution throughout the system, strongly influenced by ambient temperature variations and system cycling dynamics. These findings highlight the critical role of dynamic refrigerant-oil interaction modeling in achieving accurate system performance prediction and provide valuable insights for optimizing heat pump design and control strategies.