Investigation of failures in operation of heat networks of large heat supply systems

Abstract

The effect of deviations in heat network parameters on operation of heating system and hot-water supply systems in buildings is examined. The consequences of a decrease in the water temperature in a heat network under extreme weather conditions in a range below the design ambient air temperature, the efficiency of disconnection of a hot water supply system (HWSS) heater in this period, and deviations in the normal heat supply in the transition period at relatively high outdoor temperatures are considered. The specific and scope of failures depend on the design-heating load to design hot water supply load ratio for the heat network. A mathematical model was developed, and numerical investigation was performed of modern schemes of heat points which are designed primarily for covering the hot water supply load and recovering the heating system heat output in case of low or no hot water consumption in HWSS. The performed calculations demonstrate that the heating system has no time to restore its heat output, thereby considerably reducing air temperature in the heated premises. The lower the ambient air temperature and the lower the ratio of the design loads for hot water supply and heating, the greater is this decrease. At the same time, in case of a sudden decrease in the outdoor temperature and an accident in the heat supply system, the heating system must be the priority consumer, since a heating failure not only decreases the thermal comfort of consumers but can cause emergency situations in local utility systems, such as a cold water supply system. Correction of failures in a heat supply system requires calculation of operating conditions of heat networks.