The market share of Variable Refrigerant Flow (VRF) heat pump systems is gradually increasing in commercial buildings in North America owing to higher efficiencies compared to conventional heating, ventilation, and air conditioning (HVAC) systems, tighter zonal temperature control, and a decoupled ventilation air supply system. Validated models to accurately predict VRF installed performance are crucial to incorporating them into Energy Efficiency Programs and also for code-based compliance. Since the performance of all air-source heat pumps, including VRF systems, is dependent on ambient temperatures and part-load operation, manufacturer performance metrics based on a few rated conditions do not adequately describe actual installed performance. Previous research efforts (Dharmarajan et al., 2022) established the disconnect between manufacturer published performance datasets and the actual field performance of VRF systems, making it extremely difficult to predict the seasonal efficiencies of VRF systems in different applications. Most manufacturer datasets range from full load to only 50% or 60% part-load operation. In actual installations, where VRF equipment is sized for peak heating or cooling loads, they operate predominantly at lower part-loads, typically ranging from 0% to 50%. This also highlights the need to validate and refine current EnergyPlus VRF performance models with respect to measured field data. The objective of this paper is to compare limited lab-tested rated performance data to measured field datasets from multiple VRF installations and to generate curve fits that can be used to refine current VRF models. The analysis includes measured datasets from multiple field demonstrations, including both electric heat pump VRF (EVRF) and natural gas engine-driven heat pump VRF (GVRF) systems across a range of climate zones. The study examines the impact of part-load operation and ambient temperatures on VRF performance. Results indicate a good correlation between rated performance metrics based on laboratory data under controlled conditions and measured field performance data for heating operation. Based on multiple VRF field datasets, the authors generated a family of curves which represent a holistic VRF system heating performance map across a wide range of ambient conditions.
| File Size : | 1
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| Note : | This product is unavailable in Russia, Belarus |
| Number of Pages : | 9 |
| Product Code(s) : | D-CH-24-C056 |
| Published : | 2024 |
