Understanding Taikoo Place


Taikoo Place is the commercial hub of east Hong Kong Island. Set on an area of four million square feet, Taikoo Place is comprised of nine office buildings. Each of these buildings is serviced by water cooled air conditioning systems. These air conditioning systems use sea water cooling towers (chillers).
The performance and energy efficiency of the chillers depends upon the operating condition of their condenser units. Like most other condenser units, the condensers within Taikoo Place’s air conditioning systems suffer from fouling. Fouling greatly reduces the heat transfer efficiency resulting in increased power consumption. At the same time, fouling generates the additional cost of maintenance and the cost of lost opportunity during maintenance downtime.
To overcome this problem, Automatic Tube Cleaning Systems (ATCS) were installed in several sea water cooled chillers at Taikoo Place from 2002 to 2003. The ATCS is an environmentally sound online condenser cleaning technology which has been patented by CQM Systems.
The performance of the chiller units was monitored for six months, before and after installation, by recording their performance parameters.

The Challenge

The topic of fouling in heat exchangers has been of increasing interest in recent years since it is so closely linked to the cost of building and running a facility. It has been reported that fouling costs are about 0.25% of the gross national product (GNP) of highly industrialized countries, which, based on estimates of GNP of U.S. of $15 trillion, makes the staggering cost of fouling $37 billion a year.

To understand the high cost of fouling one must understand the effects of fouling, particularly with reference to the chiller units at Taikoo Place, Hong Kong.

Hands-On Integration

CQM prides itself on its ability to efficiently integrate its technologies with complex on-site cooling systems and towers.

ATCS: The Process

CQM’s Automatic Tube Cleaning System (ATCS), including the patented Trapping Method, is performed by the injection of pressurized air which propels the
supply water, with the sponge balls, into the heat transfer system.

chiller units

The Science of Fouling… It Matters.

The accumulation of deposits on the surfaces of a heat exchanger increases the overall resistance to heat flow.
Figure 1, illustrates the manner in which temperature distribution is affected by the presence of individual fouling

In Figure 1:
To = Temperature of outside fluid
Ti = Temperature of inside fluid
Xw = Thickness of the tube wall
Xdi = Thickness of fouling deposit
ho = Heat transfer coefficient of outside fluid
hi = Heat transfer coefficient of inside fluid
km = Thermal conductivity of tube wall
kdi = Thermal conductivity of fouling deposit

tube wall fouling depositoverall resistance to heat transfer

The overall resistance to heat transfer can be calculated using the equation to the right; where DL= logarithmic mean of the diameters of Do and Di. Fouling on the shell side of the condenser is neglected as the recirculating refrigerant stream is assumed to be clean.
It is clear that as the fouling thickness (Xdi) increases, the heat transfer coefficient (Uc) decreases. A decrease in the heat transfer coefficient implies that in order to transfer the same amount of heat, more power would be required. Therefore, when fouling thickness increases, the power consumption in heat exchangers also increases.

It Just Makes Business Sense

Across the four chillers, 13.9% energy savings was obtained. More importantly, the initial investment was recouped in less than 2 years!

This study demonstrates that companies who integrate the ATCS technology within their cooling systems realized significant savings. The table shows the
incredibly short amount of time it takes to pay back the cost of system, in each of the four separate ATCS systems installed at Tai Koo Place.