Model and simulation of multi-functional variable refrigerant flow systems in EnergyPlus

The multi-functional variable refrigerant flow (MFVRF) system is a promising solution to meet the UE objective that all new buildings shall be nearly zero-energy buildings (NZEBs). In particular, it is a high-efficiency system able to supply space cooling, space heating and domestic hot water (DHW) production simultaneously in different zones allowing also for waste heat recovery. The aim of this work is to implement a novel dynamic model of the MFVRF in EnergyPlus 9.4 in order to assess its final energy consumption and to account for the heat recovered when working in cooling mode to be used for DHW production. The developed model is employed to compare the performance of a MFVRF system in a multifamily residential building of 858 m2 with that of a conventional solution. The simulations are performed for two different climate conditions in Spain and two different DHW consumption temperatures. The results show significant energy savings achieved with the MFVRF system and DHW being consumed at 60 ºC for both Madrid (63.82%) and Seville (51.8%). Additionally, energy savings were even further enhanced for DHW being consumed at 45 ºC for Madrid (73.69%) and for Seville (70.71%). It is concluded that part of the annual DHW energy demand is covered by heat recovery for Madrid (4.96%) and Seville (5.69%) at a DHW consumption temperature of 60 ºC and for Madrid (6.42%) and Seville (8.96%) at a DHW consumption temperature of 45 ºC.