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Engineering Project Show

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by

Kenny Chew

on 3 January 2013

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Transcript of Engineering Project Show

Obstacle 1 Obstacle 2 Obstacle 3 Start Low T Syndrome New Standings The Low ΔT Syndrome occurs when the difference between the Chilled Water Supply (CHWS) and Chilled Water Return (CHWR) Temperature is less than that of the design, which is 5.5 °C.

The main cause of the Low ΔT Syndrome is the use of "constant flow" equipment, as explained by the thermodynamic equation: Condenser Water (CW) Pumps are oversized, resulting in over-pressurized pipes Detailed Energy Audit for Chiller Plant Room The chiller plant located near the TCC was built in 1998, with
3 nos. of 175 RT Chillers
3 nos. of Chilled Water (CHW) Pumps
3 nos. of Condenser Water (CW) Pumps
3 nos. of Cooling Towers (CT)

The chiller plant serves the TCC, computer labs, function rooms and a clean room which needs to be airconditioned for 24 hours, daily.

The equipment has not been upgraded since, and are of bad efficiency as of now.

2nd Green Building Master-plan mandates that government buildings must achieve the Green Mark Gold Plus certification by 2020. INTRODUCTION COOLING TOWERS OBSTACLES Low ΔT Syndrome (Q=mcΔT)

CW pumps are oversized

Over-pressurized pipes

Poor part load efficiency CURRENT STANDINGS Target Standings Poor part load efficiency Daikin McQuay Dual Compressor Magnetic Bearing Magnitude Chiller Most chillers operate most efficiently at 100% loading, but the TCC is unoccupied most of the year, resulting in low operating efficiencies.

Currently operating at 0.657 kW/RT. Dual compressor technology allows chiller to operate at higher % loading, hence better efficiency.

Magnetic bearing technology allows compressor shaft to hover in mid-air, removing friction. This in turn further improves the operating efficiency.

Proposed System: 2 nos. of 300 RT
Proposed Efficiency: Up to 0.531 kW/RT
Cost: $400,000 Solution 1 Current set of pumps: OPAL End Suction
Pressure: 40m & 35m

Proposed set of pumps: Paragon w/ Teco
Pressure: 30m & 22m
Cost: $4000 each Original design exceeded the required amount, perhaps due to "safety factor" or wrong design. Solution 2 After proposing upgrades to both the chillers and pumps (CHW & CW), the cooling tower (CT) is left.

After conducting an on-site inspection, the CTs were found to still be in good condition, hence the current set of CTs will be kept to serve the proposed system. Q= mc T Q: Cooling capacity or cooling load
m: Mass flow rate
c: Specific heat capacity of water (constant)
T: Temperature difference between CHWS and CHWR With constant flow equipments, "m" remains constant. During the night time when load conditions drop (Q decreases), ΔT has to decrease as well to satisfy the equation. This results in the Low ΔT Syndrome.

Low ΔT Syndrome in turn, will lead to capacity deficiency, increased operation costs, etc. Solution 3 Variable Primary Flow Scheme With the VPF Scheme, the flow rate (m) will be varied and modulated with respect to the load conditions. This means that when load conditions drop (Q decreases), flow rate (m) will decrease as well. This will ensure a nearly constant ΔT. Variable Frequency Drives The VPF Scheme works on the basis of equipment speed variation, which can only be achieved through Variable Frequency Drives (VFDs).

The current system is not equipped with VFDs, hence all equipment in the proposed system, including the cooling towers that are from the current design will be fitted with VFDs to enable speed modulation. Q= mc T Q: Cooling capacity or cooling load
m: Mass flow rate
c: Specific heat capacity of water (constant)
T: Temperature difference between CHWS and CHWR Advantages of VFDs Affinity Law
Initiates a soft start
Prevents water hammering
Reduce wear & tear Affinity Law P: Power consumed
N: Rotational Speed With a 10% reduction in rotational speed, around 30% reduction of power consumed can be achieved. Proposed
Schematic Diagram Return On
Investment Current System: 1,200,000 kWh/year
S$350,000/year

Proposed System: 470,000 kWh/year
S$140,000/year

Savings: S$200,000/year ROI: $745,500 / $140,000 = 3.70 years Target Standings Proposed Standings
0.6 kW/RT With reference to Green Mark for Non-Residential Existing Buildings (NREB) Version 2.1
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