Abstract
Ñontents
Introduction
Potential saving fuel in the housing and communal services (HCS) is estimated at 50-60% that gives hope for reduction of losses of fuel by 2-2,5 times. Considerable losses of fuel it is caused first of all, big power consumption of processes of heating of water for needs of heating and hot water supply. Lack of due regulation is the reason of considerable expenses of fuel.
Introduction of system of regulation of consumption of thermal energy is one of ways of economy of warmth in systems of heat supply. At establishment of an optimum operating mode the economy of warmth can make 20% and more annual consumption on heating without violation of the thermal mode in buildings. A bigger effect of automation is reached when it is carried out not only in new construction which in the large cities even in volume of a five-years period doesn't exceed 15% of all housing stock, but also at reconstruction of the existing buildings.
The greatest economy of warmth at additional regulation at consumers is reached during the autumn and spring periods in the range of so-called "break" of the temperature schedule when temperature of network water is maintained at the level 70°C With for satisfaction of loading of hot water supply while for systems of heating such temperature during this period exceeds demanded. For additional regulation of holiday of warmth a number of systems of automatic control is developed and tested for heating in TsTP in operational conditions. The organization of group automatic control of holiday of thermal energy on heating is most effective as at the same time costs of system of regulation and her operation are minimized.
Additional regulation of an expense of warmth on heating in ITP is reduced to change of a consumption of the network water coming to heating system through an elevator nozzle. If to change this expense a throttling of network water before a nozzle, then the mixture coefficient in an elevator won't change, at the same time reduction of a consumption of network water will lead to proportional reduction of a consumption of water in local system of heating. Meanwhile it is known that decrease in a consumption of water in local heating system is lower than 75-80% of settlement size that leads to inadmissible hydraulic maladjustment of system therefore it is necessary that at decrease in a consumption of network water through an elevator nozzle his coefficient of injection increased. In this case the consumption of the mixed water in local system will decrease more slowly, than the consumption of network water, and regulation will become possible on the bigger range of change of a consumption of network water.
1. Purpose and problem definition
Research objective is, the economy is warm in the housing and communal services systems.
In our country accession of systems of heating of buildings to a thermal network through water elevators was widely used. Water elevators are applied in systems of heating to fall of temperature of water in the external giving pipeline up to the temperature, admissible in system of heating, tg, and partial transfer of pressure created by the central pump at thermal station to local system of heating to water circulation creation. Thus, the water elevator in system of heating carries out at the same time two functions, replacing mixing and circulating pumps. Use of an elevator leads to stabilization of a consumption of water in system of heating that is necessary for providing her normal hydraulic mode. The water elevator is established in individual thermal point of the building. The schematic diagram of individual thermal point of system of heating with a water elevator is given in figure 1. One of shortcomings of a water elevator is his low efficiency (E). The static efficiency of a standard elevator practically doesn't exceed 10%. Therefore, circulating pressure on input of heat conductors of external thermal networks to the building has to not less than by 10 times to exceed losses of pressure in system of heating ΔPc. This condition sets the top limit of loss of pressure when using elevator mixing installation by size ΔPc = 1,2·104 Pas. Other lack of a water elevator is the constancy of coefficient of mixture excluding local high-quality regulation of a heat transfer of heating devices. Hot water from a thermal network G1, kg/s, (during the winter period with a temperature Ò1 = 130…150°Ñ) comes to a nozzle. The return water from system of heating G0 , êã/ñ, with a temperature t0 = 70°Ñ mixes up in an elevator with hot water up to the temperature tã = 95°Ñ and in quantity Gã, kg/s, comes to the giving highway of system of heating. Part of the return water in quantity (Gã – G0), kg/s, with a temperature t0 = 70°Ñ is removed in a thermal network. Therefore, the elevator works for the closed ring of system of heating.
Figure 1 – Elevator input: 1 – latch; 2 – thermometer; 3 – manometer; 4 - expense regulator; 5 – backpressure valve; 6 – ãðÿçåâèê; 7 – heat meter; 8 – pressure regulator; 9 – water-jet elevator; 10 – for systems of forced ventilation and air conditioning; 11 – temperature regulator;
The scheme of pressure during the established work of an elevator is given in figure 2. Constancy of hydrodynamic pressure at the beginning of a mixing chamber of an elevator increases pressure at sudden expansion of a stream.
Figure 2. The scheme of pressure in a water elevator for water heating.
If the hydraulic resistance of heating system decreases, the consumption of V0 water increases. The relation of two water flows in an elevator is called coefficient of mixture (admixture) which is equal ≈1,4. In calculations, temperature of network water before an elevator was accepted equal 70°Ñ, water temperature on heating leaving the system 40°Ñ. Actually water temperature on leaving the system of heating at change of a consumption of network water will change in the range from 50 to 30°C, but this change will practically not influence hydraulic characteristics of an elevator because of weak dependence of specific volume of water on temperature. In these conditions local quantitative regulation of an expense of heat on heating has to be carried out, i.e. the consumption of the network water coming to system of heating has to change. At the same time an important condition is preservation of an invariable consumption of the water circulating in system of heating in order to avoid hydraulic maladjustment of the last.
2. Solution of an objective
This problem is solved by an elevator with the adjustable section of a nozzle. At reduction of section of a nozzle as a result of a vdviganiye in him the regulating needle the consumption of network water on system of heating decreases. At the same time as a result of increase in the key geometrical parameter of an elevator – the relation of sections of a chamber of mixture and a nozzle – his coefficient of injection increases. It leads to the fact that the consumption of the mixed water circulating in system of heating decreases to a lesser extent, than a consumption of network water. At an elevator with the invariable section of a nozzle (without control device) coefficient of speed of a working nozzle φ1, this coefficient considering hydraulic losses of an elevator with the adjustable section of a nozzle changes depending on the provision of the regulating needle and consequently, and from the sizes of the ring section formed by an internal surface of a nozzle an external surface of a needle. The regulating needle not only reduces the section of a nozzle but also leads to decrease in coefficient of speed of knot a nozzle needle, at completely open nozzle (relative section of fc of =100%) φ1=0,95, at reduction of section to fc of =50% φ1 decreases to 0,8, and at fc of =25% φ1=0,74. Decrease φ1 okazyvayet considerable influence on overall performance of an elevator, i.e. on his coefficient of injection. The great influence on indicators of regulation of an elevator with the changing section of a nozzle is exerted by work of the nozzle needle hub: than less the coefficient decreases φ1 at reduction of section of a nozzle, subjects the water consumption in system of heating is less cut. In modern systems of heat supply the central high-quality regulation of holiday of heat which is reduced to change of temperature of network water depending on temperature of external air under the certain law called by the temperature schedule of a thermal network is carried out. This schedule usually is under construction so that to satisfy the main thermal loading – the heating which is characterized by the equal daily schedule and the sharp expressed seasonal unevenness. Development of the hot water supply having the equal seasonal schedule and the expressed daily unevenness has led to changes of the heating temperature schedule.
As in hot water supply it is required to pump water with a constant temperature approximately 60°Ñ, water temperature in the giving line of a thermal network can't fall below 70°Ñ though systems of heating at temperatures of external air above +2°Ñ (for climatic conditions of Donetsk) require water of lower temperature. In the absence of local regulation of holiday of heat in systems of heating it leads to an overheat of rooms and to an overexpenditure of heat on heating in the range of "cut" which reaches 2-3% of an annual expense of heat for heating. The aspiration to reduce a consumption of network water on subscriber input which has considerably increased emergence of loading of hot water supply, and to reduce the price at the same time of the most expensive part of system of heat supply – thermal networks – has led to emergence instead of parallel schemes of inclusion of heaters of hot water supply of the two-level mixed schemes in which it is used warmly network water after system of heating for preliminary heating of tap water in the first step of a heater, and two-level consecutive, in which for decrease in a consumption of network water in the period of the maximum loads of hot water supply heat-sink ability of buildings is used. In actual practice there are subscribers without loading of hot water supply and with the loading attached according to the parallel, mixed and consecutive schemes. At such variety of structures of thermal loading and schemes of her accession the uniform schedule of the centralized high-quality regulation doesn't wash to provide to a constant of settlement temperature of internal air in the heated rooms at an invariable consumption of network water during a heating season.
Conclusion
Thus, for all subscriber inputs the central high-quality regulation which is carried out in heat supply source has to be supplemented with local quantitative regulation of holiday of heat on heating by change of a consumption of network water on subscriber inputs. At the same time in order to avoid floor-by-floor maladjustment of local systems of heating it is necessary to keep an invariable consumption of water in system of heating.
References
Zinger N. M., Belevich A.I. Research of hydraulic characteristics of the jet pump (elevator) with the variable section of a nozzle.
Grudzinsky M. M., Livchak V. I. Effektivnost of group automatic control of an expense of warmth on heating with correction on temperature of internal air.
Zinger N. M. Belevich A.I. Optimization of a design of a nozzle and needle of the water-jet pump (elevator) with the adjustable section of a nozzle.
Zinger N. M. Mironov V.D., Burd A.L., Zhidkov A.A. The monitoring system and automatic control of holiday of heat on heating.
Energy saving in systems of heat supply, ventilation and air conditioning: Ñïðàâ. grant / L.D. Boguslavsky, V. I. Livchak, V.P. Titov, etc.; Under the editorship of L.D. Boguslavsky and V. I. Livchak. - M.: Stroyizdat, 1990 – 624 pages.