VRF AND ITS VARIOUS TYPES,DESIGN FACTORS,DIFFERERNT TYPES OF HVAC COMPONENTS,VRF-HEAT RECOVARY ,ADVANTAGES,LIMITATIONS,APPLICATIONS

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

2. OUTLINE
2
 INTRODUCTION
 HISTORY
 HVAC SYSTEMS
 WHAT IS VRF ?
 TYPES OF VRF
 DESIGN FEATURES
 BUILDING CHARACTERISTICS
 APPLICATION
 CONCLUSION

3. 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.

4. 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.

5. Split Air-conditioning
5
 It consists of one indoor unit along with an
outdoor unit constitute a single split AC.
source-carrier

6. 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.

7. 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

8. 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

9. 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.

10. 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.

11. 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.

12. VRF heat pump systems
12
SOURCE-DAIKEN

13. Heat Recovery VRF system (VRF-
HR)
13
Source-DAIKEN

14. 2 PIPE WITH BC VRF –HR
SYSTEM
14
SOURCE-DAIKEN

15. 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.

16. DESIGN FEATURES
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 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

17. 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

18. Compressor Efficiency
18
SOURCE-CARRIER

19. 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

20. 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

21. 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.

22. 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.

23. 23
SOURCE-CARRIER

24. 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

25. 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

26. Applications
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 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.

27. CONCLUSION
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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.

28. 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/