Evaluation of chemical and non-chemical treatment methods for condenser water: Towards GBI requirement

Abstract

In the Heating, Ventilation and Air Conditioning (HVAC) field, condenser water is used to remove heat from the refrigerant cycle and is cooled at cooling towers. Due to the high operating temperatures of 29°C to 38°C, the condenser water cycle is vulnerable to operating issues such as scaling, corrosion and microbiological proliferation; which can be mitigated through either chemical or non-chemical treatment methods. In this paper, the chemical and non-chemical treatment methods for condenser water treatment in the Heating, Ventilation and Air Conditioning (HVAC) systems are compared in terms of efficiency (scaling, corrosion and microbiological proliferation control) and environmental impact. The efficiency of one chemical treatment system (descalant) and three non-chemical treatment systems (Merus Ring, Power Pulsed and Ultra Low Frequency) are investigated by taking condenser water samples from the cooling tower basins biweekly for three months to characterize for pH, water alkalinity, iron content, chloride content, total dissolved solids (TDS) content, electrical conductivity and water hardness, which are compared to the Japan Refrigeration and Air Conditioning Industry Association Standards (JRA-GL-02-1994) and applied to the Langelier Saturation Index (LSI), Ryznar Stability Index (RSI) and Practical (Puckorious) Scaling Index (PSI) to predict the scale formation in condenser water samples. The temperature differences between chilled waters for all systems investigated are recorded to relate the characterized parameters to chiller efficiency. The environmental impacts for all systems investigated are assessed by focusing on the operational stage of all system where the main source of environmental damage is due to the electrical consumption by the HVAC systems. The results yield that all systems investigated comply to the industrial standards. LSI and RSI proved that all condenser waters are saturated with calcium ions but PSI proved that scale formations in the systems investigated are unlikely as the scales are likely to remain dissolved in the condenser water. Consistent temperature differences of chilled water are observed throughout the research period which show that the performance of chillers in each system are optimal, which proves that non-chemical treatment systems are as efficient (in terms of corrosion, scaling and microbial activity control) as chemical treatment system. Environmental impact analysis concluded that chemical treatment system has the highest annual equivalent CO2 emission per cooling capacity of 868.30 kg CO2 e/year RT and that two of the chemicals used causes damage to the aquatic environment. Thus, non-chemical treatment systems have lesser environmental impact than chemical treatment system.