Variable refrigerant flow (VRF) has the ability to control the amount of refrigerant flowing to each of the evaporators, enabling the use of many evaporators of differing capacities and configurations, individualized comfort control, simultaneous heating and cooling in different zones, and heat recovery from one zone to another. In the system, refrigerant flow control is the key advantage it also allows the use of many evaporators of differing capacities and configuration.
Variable Refrigerant Flow (VRF) System:-
VRV system has the ability to control the amount of refrigerant flowing to the multiple evaporators (indoor units), enabling the use of many evaporators of differing capacities and configurations connected to a single condensing unit. The control is achieved by varying the flow of refrigerant through a pulse modulating valve (PMV). The indoor units are linked by a control to the outdoor unit which responds to the demand from the indoor units by varying its compressor speed to match the total cooling and/or heating requirements.
The new VRF system uses an inverter compressor which is capable of changing the speed to follow the variations in the total cooling/heating load as determined by the suction gas pressure measured on the condensing unit.
In this, the compressor and condenser are the part of outdoor unit while evaporator and expansion valve are the part of the indoor unit attached with the distribution pipe.
The performance of VFR system is evaluated through energy simulation software Trace for a practical office building running from 8:00AM to 7:00PM. This building is in Jodhpur, Rajasthan which comes under the composite climate of Indian context. The building has only one floor with total area- 2500 m2. The orientation of the building is in the west direction. The air cooled VRF system is compared with the packaged terminal air conditioner with system to maintain the indoor conditions-240 C temp. & 60% RH and the results are as follows-
In the above case study, simulative results shows that the VRF system is 28% more efficient to save the energy for maintaining the same thermal comfort in the building.
Er. Sheelam Khare & Er. Rishikesh
Source- HVAC Variable Refrigerant Flow System, by A. Bhatiya