COOLING COIL PERFORMANCE OPTIMIZATION DURING OPERATION STAGE

Abstract

In Singapore, air conditioning is attributed as one of the major services of most buildings, contributing 60% to a building’s total energy consumption. Despite the widespread usage of air-conditioning systems, the local industry seems to be plagued with the problem of supplying over-designed coils to many buildings. Over-designed cooling coils reduce operating efficiencies, often operating at less than their design capacity. Reduced efficiency adversely affects the cooling and dehumidification process, which in turn affects energy consumption.

The objective of this report is to understand current cooling coil operating condition so as to find ways to improve operational efficiency. The research methodology involves the use of coil selection software, SPC 2000 version 4.6 for the purpose of simulation. Simulations results revealed that oversized coils operating at less than design load increases the Sensible Heat Ratio (SHR). This increase in SHR leads to overcooling and under-dehumidification of the air which inevitably affects the Indoor Air Quality (IAQ). Further simulations were performed and analyzed to prove the research hypothesis: reducing the effective number of coil rows during operation increases the efficiency of the coil. Analysis of the simulated results clearly strengthens and supports this hypothesis. This brought about the proposed implementation of the bypass valve system, which allows flexibility in operating at a 6-row or 3-row coil condition. With this flexibility, the system addresses the issues arising from over-designing. Although the issue of over-design as acknowledged by the author may not be resolved in the near future, the proposed system can contain its effects. This proposed system not only caters for oversized cooling coils, it can also be implemented on optimally design cooling coils so as to cater for possible future reduction in cooling load requirements.

The associated limitations involving simulations include 1) inability to capture real life/environmental variables due to software limitations, and 2) a possible bias approach arising from the selected software manufacturer. However, the results and data collected still proved useful in emphasizing and proving of the hypothesis. With this approach, the author hopes to contribute on a macro level to global sustainability, and on a micro level, the life cycle maintenance cost of building operation.