ПРОБЛЕМЫ ОБЕСПЕЧЕНИЯ ТЕПЛОГИДРАВЛИЧЕСКИХ РЕЖИМОВ КАК ПРИЧИНА ПЕРЕХОДА НА ЛОКАЛЬНЫЙ ИСТОЧНИК ТЕПЛОСНАБЖЕНИЯ

Abstract

As a necessary boundary condition, certain supply temperatures have to be maintained in order to provide sufficient thermal energy effectively. In order to ensure the quality of the thermal service (e.g. domestic hot water (DHW) needing to be supplied at 60°С), a district heating (DH) is usually regulated under two control levels. The first level is named the centralized control; this level functions at the heat sources, which controls the primary supply temperature and then rotation of a pump rotor varies to meet the heating load variations of a building (second level). The coefficient of mixing of the elevator is defined as the ratio between the water flow delivered from a DH network to the building and the DH network flow rate. We outline the overall framework workflow, beginning with identifying the study region, selecting promising locations of sufficient population size to warrant DH/CHP investment, assessing future heat demand, costs of reconstructing a boiler plant or expanding an existing DH network. We found what commercial software and non-linear equations staff uses (1) to model and analyze various values for controlling the supply temperature, effect of outdoor temperature and (2) to evaluate water flow. The values suggested in the Russian Regulations on the utility services (approved by the Decision No. 354 of the Government of the Russian Federation of 6 May 2011) include the efficiency of regulation, indoor and DHW temperature but not DH network flow rates. The risks that can threaten a DH company when individual homeowners implement heating system improvements increasing flow rates are especially high for a single-family house. About 10..15% of heat power is considered as a loss in the conversion from DH to a space heating (SH) system and is therefore not available at the balance. Another problem is the local control; this level functions at each heating substation, which controls the SH supply temperature and secondary pump speed to satisfy the variable heating load of the heat consumers. This situation is compounded by the faulty adjusting the control valve of at the SH side. A further reduction of the flow rate is therefore difficult without legally profound interventions in the district heating substations. In each hydraulic branch, it may consume some extent of water pressure head which is defined as “excess head”; part of the available head necessarily consumed by local throttle valves is defined as “available head” (at least 15 metres of water). Because reductions in the supply temperature or pressure lead to uncomfortable conditions for consumers, it is common for Russian DH companies to make recalculations according to the hot water parameters they deliver to a substation. We also show the investment required for residential and commercial oil/natural gas furnaces/boilers and DH equipment for three scenarios. The actual savings realised by a DH company depend on the price structure of the competing companies. The analysis concludes that all either natural gas or oil based local heating equipment should be replaced by DH.