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S.EZHIL RAJ M.E-THERMAL(R&AC) 1 VARIABLE REFRIGERANT FLOW (VRF)

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Page 1: VARIABLE REFRIGERANT FLOW(VRF)  ppt

S.EZHIL RAJ

M.E-THERMAL(R&AC)

1

VARIABLE REFRIGERANT FLOW

(VRF)

Page 2: VARIABLE REFRIGERANT FLOW(VRF)  ppt

OUTLINE

2

INTRODUCTION

HISTORY

HVAC SYSTEMS

WHAT IS VRF ?

TYPES OF VRF

DESIGN FEATURES

BUILDING CHARACTERISTICS

APPLICATION

CONCLUSION

Page 3: VARIABLE REFRIGERANT FLOW(VRF)  ppt

INTRODUCTION

3

Controlled refrigerant is supplied in the evaporator

unit as per load requirement.

No intermediate medium for the heat exchange which

makes it efficient.

In a VRF system, multiple indoor fan coil units may be

connected to one outdoor unit.

Page 4: VARIABLE REFRIGERANT FLOW(VRF)  ppt

HISTORY

4

Variable refrigerant flow (VRF), also known

as variable refrigerant volume (VRV), is invented

in Japan by Daikin company in 1982.

Daikin had registered the VRV term as an official

trademark. All other companies use VRF for their

similar HVAC systems.

Eventually, VRF is the more common term

for these types of systems, and this is the term that will

be used for the rest of the article.

Page 5: VARIABLE REFRIGERANT FLOW(VRF)  ppt

Split Air-conditioning

5

It consists of one indoor unit along with an

outdoor unit constitute a single split AC.

source-carrier

Page 6: VARIABLE REFRIGERANT FLOW(VRF)  ppt

Few advantages and Disadvantages

of Spilt AC’s

6

Advantages:

These AC’s have low initial cost

Ease of installation

No ducting required

Each system have own control.

Disadvantages:

Distance between indoor and outdoor unit should not be greater than 100- 150 ft otherwise the performance will suffer.

Limited air throw.

Page 7: VARIABLE REFRIGERANT FLOW(VRF)  ppt

Multi-Split Systems

7

There are multiple evaporator units connected to

one external condensing unit. These type of

systems were designed mainly for small to

medium commercial applications.

Each indoor unit has its own set of refrigerant

pipe work connecting it to the outdoor unit.

SOURCE-DAIKEN

Page 8: VARIABLE REFRIGERANT FLOW(VRF)  ppt

Multi-Split Systems

8

Advantages of Multi-splits:

No need of duct work installation.

System efficiency improves then individual Split unit.

Multi-splits are suitable for single thermal zone applications i.e. either for cooling mode or heat mode.

Drawbacks:

Main Drawback is that Individual system control not possible.

In this systems whole system will turn OFF or ON completely in response to a single thermostat. These systems are therefore not suitable for areas/rooms with variable heat gain/loss characteristics

Page 9: VARIABLE REFRIGERANT FLOW(VRF)  ppt

Variable Refrigerant Flow

Systems

9

Adjust cooling and heating by adjusting refrigerant

flow and variable speed compressor .

Indoor units can be in different modes .

VRF systems are equipped with enhanced features like

inverter drives, pulse modulating electronic expansion

valves and distributed controls.

Page 10: VARIABLE REFRIGERANT FLOW(VRF)  ppt

Types of VRF systems

10

Cooling only systems – those systems can only cool.

Heating is not available. Fan and Dry modes are

available for each indoor unit independently.

Heat Pump systems – All the indoor units can either

heat or cool . Fan and Dry modes are available for each

indoor unit independently.

Heat Recovery systems – These systems are the most

sophisticated ones, where cooling and heating may be

available by each indoor unit, independently, at the

same time.

Page 11: VARIABLE REFRIGERANT FLOW(VRF)  ppt

VRF heat pump systems

11

VRF heat pump systems permit heating or cooling in

all of the indoor units but not simultaneous heating and

cooling.

When the indoor units are in the cooling mode, they

act as evaporators; when they are in the heating mode,

they act as condensers.

These are also known as two-pipe systems.

Page 12: VARIABLE REFRIGERANT FLOW(VRF)  ppt

VRF heat pump systems

12

SOURCE-DAIKEN

Page 13: VARIABLE REFRIGERANT FLOW(VRF)  ppt

Heat Recovery VRF system (VRF-

HR)

13Source-DAIKEN

Page 14: VARIABLE REFRIGERANT FLOW(VRF)  ppt

2 PIPE WITH BC VRF –HR

SYSTEM

14SOURCE-DAIKEN

Page 15: VARIABLE REFRIGERANT FLOW(VRF)  ppt

VRF-HR

15

Typically, extra heat exchangers in distribution boxes are used to transfer some reject heat from the superheated refrigerant exiting the zone being cooled to the refrigerant that is going to the zone to be heated.

It should be noted that this perfect balance of heating and cooling demand is unlikely to occur for many hours each year, but whenever mixed mode is used energy is saved.

Units are now available to deliver the heat removed from space cooling into hot water for space heating, domestic hot water or leisure applications, so that mixed mode is utilized for more of the year.

Page 16: VARIABLE REFRIGERANT FLOW(VRF)  ppt

DESIGN FEATURES

16

Separation tubes and Header

A separation tube has 2 branches whereas a header has more

than 2 branches. Either of the separation tube or header, or

both, can be used for branches. However, the separation tube

is never provided after the header because of balancing issues

Page 17: VARIABLE REFRIGERANT FLOW(VRF)  ppt

DESIGN FEATURES

17

The compressor unit includes two or more scroll or

rotary compressors which is an inverter-controlled

variable-speed VRF compressor. The variable-

speed compressor units are rated at significantly

higher part-load efficiency than constant-speed

systems.

SOURCE-CARRIER

Page 18: VARIABLE REFRIGERANT FLOW(VRF)  ppt

Compressor Efficiency

18

SOURCE-CARRIER

Page 19: VARIABLE REFRIGERANT FLOW(VRF)  ppt

DESIGN FEATURES

19

Electronic Expansion Valve (EEV) instead of

Thermostatic Expansion Valve (TXV)

TXV valves are spring actuated (mechanical)

Prone to hunting (overfeeding or starvation of

refrigerant)

Source-CARRIER

Page 20: VARIABLE REFRIGERANT FLOW(VRF)  ppt

DESIGN FEATURES

20

Inverter Technology

Converts AC to DC and then modulate to desired

frequency required for the desired motor load.

• Multiple or single inverter driven compressor is

used

SOURCE-SAMSUNG

Page 21: VARIABLE REFRIGERANT FLOW(VRF)  ppt

Pipe Design

21

The long pipe lengths will introduce pressure losses in

the suction line and, unless the correct diameter of pipe

is selected, the indoor units will be starved of

refrigerant resulting in insufficient cooling to the end

user.

So it is very important to make sure that the pipe

sizing is done properly, both for the main header pipe

as well as the feeder pipes that feed each indoor unit.

The maximum allowable length varies among different

manufacturers.

Page 22: VARIABLE REFRIGERANT FLOW(VRF)  ppt

Building Characteristics

22

The maximum allowable vertical distance between an

outdoor unit and its farthest indoor unit is 50m

The maximum permissible vertical distance between

two individual indoor units is 15m,

The maximum overall refrigerant piping lengths

between outdoor and the farthest indoor unit is up to

180m. Note: The longer the lengths of refrigerant

pipes, the more expensive the initial and operating

costs.

Page 23: VARIABLE REFRIGERANT FLOW(VRF)  ppt

23SOURCE-CARRIER

Page 24: VARIABLE REFRIGERANT FLOW(VRF)  ppt

ADVANTAGES

24

Energy Saving claimed upto 40 %.

High COP.

Space saving

Lesser Noise

Precise temperature control

Simultaneous heating and cooling (three-pipe

VRF heat recovery system only)

Heat recovery

Zoned comfort

Page 25: VARIABLE REFRIGERANT FLOW(VRF)  ppt

LIMITATIONS

25

Initial cost is High ,since additional backup unit is

needed

Separate Ventilation system

Refrigerant Piping

Environmental Concerns

For high rise building the system cannot be used

Source-DAIKEN

Page 26: VARIABLE REFRIGERANT FLOW(VRF)  ppt

Applications

26

VRF systems may be a particularly good option for

buildings with multiple zones or wide variance

heating/cooling loads across many different internal

zones.

These systems provide individual control and are the

most versatile of the multi-split systems. Hotels,

schools and office buildings are good examples.

Page 27: VARIABLE REFRIGERANT FLOW(VRF)  ppt

CONCLUSION

27

The variable refrigerant flow system is considered

to be one of the most promising energy saving

technologies gaining its momentum in recent years.

A viable energy efficient technology is needed to

conserve energy as well as to achieve better

human comfort. So this is been relatively new and

efficient way to design HVAC system with VRF

technology.

Page 28: VARIABLE REFRIGERANT FLOW(VRF)  ppt

References

28

Goetzler, W. (2007). Variable refrigerant flow

systems. ASHRAE Journal.

VARIABLE REFRIGERANT FLOW SYSTEMS

Technology Overview ASHRAE

NB/PEI,SEPTEMBER 2011 Roger Nasrallah, ing.

Enertrak in

http://www.ashrae.in

http://totalclimatecontrol.com.au/heat-recovery-

vrf-system-vrf-hr/