Drinking water temperature modeling in domestic systems
A. Moerman
J.H.G. Vreeburg – Mentor
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Abstract
Domestic drinking water systems are the final stage of the transport process to deliver potable water to the customers tap. Although these systems play an important role in drinking water quality only several researches on the edge of residence time and temperature were performed during the past. These two parameters play an important role in microbial growth and metal leaching. Past research was performed on the appearance of Legionella in domestic drinking water systems, occurrence of hotspots which influence the drinking water temperature and the microbial growth and leaching of metals in stagnant water. However, the fluid dynamics which are present in domestic drinking water systems due to highly variable demand patterns were not included yet. By the use of SIMDEUM consumer demand patterns could be modeled, and drinking water dynamics can be approached. The Dutch legislation on drinking water prescribes the temperature at the tap should not exceed the threshold of 25°C. However, any scientific basis for this threshold was not found in the literature. Nor could it be obtained from interviews with experts. During this master thesis research a model was developed to calculate the temperature in domestic drinking water systems. Afterwards several scenarios were calculated to investigate the effects of e.g. hot summer days, pipe concealment, housing types and hotspots on the drinking water temperature. This research is a first exploration in the field of drinking water temperature modeling in domestic systems, since empirical data on temperature in domestic drinking water systems is not available. It was found that residence time influences the microbial growth more than temperature does. Demand pattern changes in time have more influence than demand volume changes since water in the domestic drinking water system is heated relatively fast. The results of this research have consequences for the in house sampling method of Dutch water companies (RDT sampling) which is used to measure the water temperature within the drinking water supply system before the water meter. Water is heated while it passes the domestic drinking water system before it is sampled at the kitchen tap. Hence the actual temperature in the drinking water distribution system will be lower than RDT measurements show.