Wednesday, August 05, 2009

Electronic Descaling Prevents Limescale Build Up

Environmental Treatment Concepts has partnered Hull University's Department for Chemistry in Industry to develop an effective, environmentally friendly method of testing physical water treatment. Water that is naturally hard, as in 70 per cent of the UK, contains dissolved calcium and other minerals. These help to build and maintain healthy bodies, but their effect on pipework and water systems can be disastrous. When water-borne minerals, such as calcium bicarbonate, revert to their solid carbonate state, limescale is formed in water systems, and this narrows pipes, blocks jets, slows the flow, reduces thermal efficiency and provides a breeding ground for bacteria.

Research has shown that just 6mm of limescale will reduce energy efficiency by 40 per cent and, in a moderately hard water area, 6mm of limescale can form in pipework, or on heat exchangers in just two years. This in turn results in higher running costs. Portsmouth University used the difference in thermal transfer properties of copper pipe and hard water scale to calculate how long the water needs of a family would take to heat in a conventional domestic hot water cylinder. With no scale on its heat exchanger, it takes 1.5 hours to heat up.

However, with just 5mm of scale the boiler now has to run for more than four hours. This is because the thermal conductivity of calcium carbonate (scale) is 4,000 times less than that of copper. The larger the water system, the greater the potential energy wastage. At King's School Canterbury a temperature data logger and an electronic descaler were placed on two parallel hot water calorifiers, heating a total of 9,000 litres of water. The data logger outputs show that on the installation date, the primary boiler was running continuously for 17 hours during the day, attempting to get the water to the required temperature.

Two months later, when the heat exchanger had began descaling, the boiler ran just 6.5 hours, a reduction of almost 62 per cent. Pre-installation, it took six hours and 20 minutes for water temperature to recover 10C and once the heat exchanger became more efficient, by removing scale, recovery time dropped to two hours 40 minutes. Energy is wasted due to scaling in many ways. About the most wasteful are air-conditioning and refrigeration chillers.

One major chiller manufacturer, York International, said that just 0.04in of scale on condenser tubes of a typical 500 ton chiller, wastes GBP25,000 in energy per year. These tubes are typically 3/4in diameter and are often found completely blocked with calcium in under a year, so 0.04in of scale can be formed very quickly.

A recent report carried out by Advantica, at the former British Gas research establishment in Loughborough, measured the relative energy consumption of a clean and scaled gas-fired water heater. This report concluded that in the steady-state fully fired condition, the 9g of scale deposited in the heat exchanger resulted in an average reduction of 5.6 per cent in gas boiler efficiency. In heat-up mode (as with an instantaneous water heater) the 9g of scale deposited in the heat exchanger resulted in an average reduction of 17 per cent in gas boiler efficiency.

Currently, no government agency (Carbon Trust, EST, BRE, and so on) recognises the potential energy (and water) savings to be made by encouraging the use of water treatment in hard water areas, (70 per cent of the UK). The Carbon Trust states that 1mm of limescale will increase energy cost by seven per cent and recommends regular cleaning as the solution, but with new and emerging technologies, it is no longer necessary to resort to chemical and mechanical cleaning methods alone. With electronic water descaling the build up of limescale can be prevented.

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