ASHRAE Journal - February 2013 - S13

Feature
• Other benefits of reliability, better
dehumidification, quicker response
time and wider capacity range
make the digital scroll technology
more attractive.

Table 1: Cost benefits due to installation of VRF system with digital scroll technology.
Description

Unit

For DX System

Total Load In Durbar Hall and Galleria Restaurant: 90 TR
Power consumption
kW/TR
1.35
Total power consumption
kW
121.5
Hours of operation per day
Hrs/day
8
Total power consumption per day
kW/day
972
Working days per year
days/year
250
Total power consumption per year
kW/year
243,000
Electricity cost per unit (kWh)
Rs./$
6
1,458,000/
Cost of power per annum
Rs./$
29,160

For VRF System
0.85
76.5
8
612
250
153,000
6
918,000/
18,360
540,000/
10,800

Small Duct, High Velocity System
• In a small duct, high velocity system, the AHU delivers the air at very
high external static pressure.
• Heat transfer is higher than in the
conventional system; ΔT across the
coil is around 54°F to 61°F (12°C to
Savings per annum
Rs./$
16°C). Due to these two factors, air
Total Load In New Banquet and Guest Rooms: 108 TR
quantity per ton can be reduced
Power consumption
kW/TR
1.35
0.85
to 250 cfm to 280 cfm (118 L/s to
Total power consumption
kW
145.8
91.8
132 L/s).
Hours of operation per day
hrs/day
8
8
• This enables a small duct size,
Total power consumption per day
kW/day
1166.4
734.4
which can be accommodated in
Operational days per year
days/year
250
250
very little space above the false Total power consumption per year
kW/year
291,600
183,600
ceiling.
Electricity cost per unit (kWh)
Rs./$
6/0.12
6/0.12
• Ducting is designed using the static
1,749,600/
1,101,600/
Rs./$
regain method to maintain high Cost of power per annum
34,992
22,032
static throughout the supply duct.
648,000/
Savings per annum
Rs./$
12,960
The flexible supply tubing plays a
large role in minimizing the supply Additional Income generated due
to space utilization for 6 new guest
10,800,000/
noise.
Rs./$
rooms (Rs. 10,000 per day tariff ×
216,000
• The air distribution is called aspira- 180 days occupancy × 6 rooms)
tion and is different from conven- Total benefit to the client due to
tional air diffusion.
installation of Samsung VRF System
11,988,000/
Rs./$
239,760
• The supply air velocity (face veloc- with Emerson Digital Scroll Technolity) is above 800 fpm (4 m/s) and ogy (A+B+C)
goes up to 2,000 fpm (10 m/s). But
ber units and further purified with activated carbon filters
the air quantity per outlet is limited to 18 cfm to 40 cfm
before being exhausted to the environment.
(8.5 L/s to 19 L/s).
• Sound levels have been drastically reduced from 85 dBA
• The supply jet forms a beam at a very high velocity and
to almost zero near the owner’s residence, and around
creates a negative pressure around the periphery of the
60 dBA near the outdoor unit battery due to the distant
supply beam. The room air is attracted towards the primary
location of these units.
air due to this negative pressure. This is called aspiration.
• The old DX system using R-22 is now replaced with eco• The induction of room air with primary air gives an even
friendly R-410A refrigerant.
temperature in the room and hot pockets are avoided. As the
• The entire system is now controlled from the BMS room,
air quantity per outlet is 40 cfm (19 L/s) only, the number of
and room parameters can be set through the data manoutlets per ton of cooling capacity can vary from eight to 10.
agement system. Faults can be immediately seen from
• This system can deliver its maximum cooling capacity if
the central system, which gives the user controllability.
the coil inlet temperature of the refrigerant is maintained
around 43°F (6°C).
• As the system is integrated with VRF outdoor unit, suitable Conclusion
Retrofitting the HVAC system of a heritage building requires
electronic expansion valves have been used for achieving
sensitivity to the design, materials and other special features of the
the required evaporating temperature.
building. It is important to ensure that the selected retrofitting measures complement the existing building and do not have an adverse
Environment-Friendly System Design
impact on its historic or architectural characteristics. It is challenging
Indoor Environmental Quality
• To maintain indoor air quality, each room is provided with for a consultant to design and select a system that will promote
sustainable performance for existing heritage buildings without
treated fresh air.
• Kitchen exhaust air is treated through electrostatic scrub- adversely impacting their cultural and traditional significance.
S13

February 2013

ASHRAE Journal - February 2013

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