Mixed 0-1 sequential linear programming optimization of heat distribution in a district-heating system

A district-heating system transports heat from the heat plant by using prim ary pipe network, via substation, to secondary pipe network where heat is f inally distributed to buildings. When this system is designed its operation al characteristics were selected to provide thermal comfort (TC) in all bui ldings served by this district heating system. After several years of opera tion, the system characteristics may change and TC in buildings deteriorate s; some buildings are overheated and other buildings are underheated. The s tudy investigates an optimum strategy to mitigate the problem caused by cha nges of three of system characteristics: hydraulic resistance of secondary pipe network, heat transmittance of radiators inside buildings, and heat tr ansmittance of building envelope. A strategy of problem mitigation consists of the adjustment of hydraulic resistance of existing valves and retrofitt ing the local heating system with new substation heat exchanger and additio nal pumps. We used a steady state, bottom-up approach and mixed 0-1 sequent ial linear programming to find optimal mitigation strategy, i.e. optimum co mbination of valves' hydraulic resistances, new pumps placement and new siz e of substation heat exchanger. The results indicate that the calculated op timal strategy does not effectively improve TC in buildings only in cases w hen TC is deteriorated by higher than nominal values of heat transmittance of some building envelopes. (C) 2000 Elsevier Science S.A. All rights reser ved.