Improving the maneuverability and thermal efficiency of modern cogeneration systems based on gas turbine power plants

The paper is devoted to the issue of increasing the maneuverability and efficiency of modern cogeneration systems based on gas turbine power plants. Promising solutions for increasing the maneuverability of GTU-CHPP by using heat accumulators and the formation of a preheating circuit of the network water are considered. It is shown that in the non-heating period, it is possible to increase both the thermal efficiency and the generated electric power by installing a heat exchanger in front of the compressor. The calculation results show that this provides an increase of 0.4% in the net electrical efficiency by and an increase 3.3% in the annual electricity generation.

Improving a heat supply system by increasing the efficiency of the heat pump unit

The reliability and efficiency of the operation of district heating systems is largely determined by the efficiency of preparation of heating network water. In open heat supply systems, make-up water, among other things, compensates for the water intake in hot water supply systems. A number of technologies have been developed that increase the efficiency of an open heat supply system by reducing the water consumption in the supply pipeline of the heating network, increasing the operating time of the heat pump, and increasing the specific generation of electricity for heat consumption at the CHP plant due to additional cooling of the network water in the return pipe of the heating network.

Methodology for determining the flow rate and temperature of generated hot water when calculating the thermal diagram of a hot water boiler room

The consumption and temperature of hot water produced by boiler units are calculated using such a quantity as the consumption of the consumed network water. The formulas represent functional dependencies connecting the obtained values not only with the consumption of heating water, but also with the consumption of hot water supplied for recirculation, for own needs and for the needs of the fuel economy. They take into account the losses of network and hot water. The formulas are obtained as a result of the joint solution of the equation for the total consumption of hot water and the equation for its partial costs.

Determination of the Design Characteristics of Heat Exchange Equipment for Heating Network Water of a Cogeneration Gas Turbine Unit with a Change in the Heat Load of Consumers in Regions with Different Climatic Conditions

Optimization studies of the dependence of fuel consumption on changes in the heat load of consumers in regions with different climatic conditions and taking into account the determination of the design characteristics of the equipment for heating network water of a cogeneration GTU were carried out. The GTU has two fuel combustion chambers, a waste-heat boiler and a contact heat exchanger for heating of feeding network water. Schematic-parametric optimization studies were carried out on the design mathematical model of the GTU. The analysis of the data of the circuit-parametric optimization made it possible to conclude that for the operating modes of the gas turbine plant with a higher thermal load, it is advantageous to slightly increase the heating surface area of the heater of feeding network water, the cost of materials for the manufacture of which is lower than for the waste heat boiler. This technical solution provided a relatively low increase in specific capital investments with full provision of consumers with electric and thermal energy. The data obtained in this work can be used to select the optimal technical solutions that ensure competitiveness in the operation of a cogeneration gas turbine unit in regions with different climatic characteristics.

HEAT MODES OF THE HEATING NETWORK IN WARMING BUILDINGS

The results of calculations of heat losses by network pipelines for heating of idealized groups of buildings during insulation of structures are presented in the work. Formulas for estimation of heat loss reduction by heat conduits are proposed depending on the efficiency of energy saving measures for construction and the law of change of network water costs along the length of the heat conduit, which is determined by the network configuration. The purpose of this work is to evaluate the influence of the hydraulic characteristics of the branches of the heating network on the magnitude of heat losses during transportation of the coolant by pipelines of the distribution network to buildings. Idealized groups of buildings with the same number of objects and the same maximum heat consumption for heating of a separate building are considered. For district heating systems, the efficiency of implementing energy-saving measures for buildings is determined not only by the reduction of heating costs, but also by the change in operating costs for the microdistrict heating network, which is caused by the reduction of heat carrier costs and heat losses by heating system pipelines. The magnitude of the heat loss depends on the method of laying the networks, the parameters of the pipeline insulation, the temperature of the coolant, and the environment. In the case of selective insulation of the buildings of the selected group of buildings, the location of the insulated building is significantly influenced by the amount of heat losses by the pipelines. In case of centralized heat supply, a fragment of the construction load decrease due to the insulation of buildings and the reduction of the network water temperature in the space heating devices causes the reduction of heat losses by the pipelines of the distribution thermal networks. The magnitude of the reduction of heat losses by heat pipelines is determined by the degree of efficiency of insulation of buildings, the nature of changes in the cost of the coolant along the length of the branch of the thermal network and practically does not depend on the magnitude of the heating load of buildings. Keywords: centralized heat supply, centralized heating systems, energy saving, heat transfer resistance, enclosing structures, coefficient of efficiency of building insulation, distribution thermal networks, heat loss by pipelines.

Response of the Bacterial Community and Antibiotic Resistance in Overnight Stagnant Water from a Municipal Pipeline

Although drinking water safety has raised considerable concern, to date, the hidden health risks in newly released overnight water from a municipal pipeline have seldom received attention. In this study, bacterial community composition and the response of antibiotic-resistant bacteria (ARB) to ciprofloxacin, azithromycin, tetracycline, penicillin, and cephalosporin in overnight stagnant water were analyzed. With increases in heterotrophic bacteria plate count (HPC) during water stagnation, the numbers of ARB and the ARB/HPC ratios for the five antibiotics in resident water were observed to increase, which illustrated that the prevalence of ARB rose in the pipe network water during stagnation time (ST). Furthermore, during water stagnation for 12 h, an increase in bacteria related to fermentation was also observed. When the ST rose to 48 h, the fermentation bacteria become non-significant, and this was related to the exchange of pipe network water during daytime stagnation within the 48-h period. The antibiotic resistance index (ARI) showed that tetracycline had the highest resistance level in fresh water, and then decreased during water stagnation. When ST increased to 12 h, all ARI values of the five antibiotics were low, which was associated with changes in parameters during water retention and reduced resistance during short-term stagnation. When the ST increased to 24 and 48 h, the resistance to most antibiotics (except for tetracycline) increased, which showed that increasing antibiotic resistance is caused by the formation of biofilms in the pipeline during water stagnation.