A MODELING TECHNIQUE FOR ESTIMATING HOT TAP WATER-CONSUMPTION IN DISTRICT-HEATING SYSTEMS

This paper is concerned with estimating the hot tap water consumption in district heating systems when direct measurements of the hot tap wa ter are not available. Instead, only measurements of the total mass fl ow, that is the mass flow for both heating and hot water are assumed a vailable. Thus, a method is needed that may be applied in order to sep arate the mass flow into these two parts, or even more if the mass flo w is assumed to be consisting of more than two factors. Here, the mass flow is divided into one part dependent upon climate variables and on e part that is independent of the climate. By assuming that the hot ta p water consumption is to a high degree independent of the weather, th e latter part is an estimate of the hot tap water. The data are from t he Reykjavik Municipal District Heating System in Iceland. The results show that the hot tap water consumption has a noon and an evening pea k and is at its minimum around 4 a.m. The average consumption is about 10 per cent of the yearly average mass flow. Furthermore, the consump tion is highest during the winter time and lowest during the summer ti me. It was found sufficient to use one tap water profile on working da ys and one for weekends. It is shown that the solar effect on the mass flow is quite moderate. During working days it is about 1.2 per cent of the yearly average mass flow and 1.6 per cent during weekends (base d on 10 hours of sunshine per day).