For the device located in a ground floor and included in ring ABVGDLMZHZIK, circulating pressure will be created by a difference of scales of water column ZHZ and column AB as on site BVGDLM the temperature is identical and equal 95 ° With, and on site AKIZ the temperature too is identical and equal 70 ° to S.No height of water columns AV and EZ accordingly more heights of water columns AB and ZHZ. Hence, and the difference in weight of columns AV and EZ will be more differences in weight of columns AB and ZHZ, from here circulating pressure for the device of the second floor more than for the ground floor device.
It the following often observed phenomenon speaks: in systems of water heating heating devices of the top floors get warm better, than devices of ground floors.
From resulted above reasonings follows that in two-trumpet systems of heating the heating devices located flush with a copper or below it, will not work or will get warm very poorly. For the specified systems practice establishes the least distance between the centre of heating devices of a ground floor and the copper centre in 3 metres. In this connection boiler-houses for heating systems should have sufficient zaglublenie. The specified lack are deprived one-trumpet systems of heating. In this case the hydrostatic pressure, forcing to circulate water in system, will be formed izza water coolings in the pipelines bringing nagretuju water to heating devices, and also taking away a chilled water from devices to a copper.
This cooling is useful , first, for creation of a hydrostatic pressure, and secondly, for additional heating of the premise, therefore the specified pipelines lay openly and do not isolate. On the contrary, water cooling in the main strut (the elevating pipeline) is harmful, for leads to decrease in temperature and increase in density and, as consequence, to reduction of a hydrostatic pressure. In this connection an elevating strut from a copper it is necessary carefully teploizolirovat.
the Quantity of heat , given to a premise heating devices, depends on quantity of water arriving in the device and its temperature. In turn, the quantity of water which can be passed through the pipeline to the device, depends on the circulating pressure forcing water to move on a pipe. The more circulating pressure, the can be diameter of a pipe for the admission of a certain quantity of water less and, on the contrary, the less circulating pressure, the there should be diameter of a pipe more.
But for normal action of system of heating one more condition is required: that circulating pressure was sufficient for overcoming of all resistance which are met by moving water in this system. It is known that water at the movement in heating system meets the resistance caused by a friction of water about walls of pipes, and except them, also local resistance which taps, tees, krestoviny, cranes, heating devices and coppers concern.
Resistance owing to a friction depends on diameter and length of the pipeline, and also on speed of movement of water (if speed increases twice resistance - four times, i.e. In square-law dependence). Than diameter and more length of the pipeline and the above speed of water is less, the more resistance is created on a water way, and on the contrary.
In the scheme of heating represented on rice 1 and is available two rings: one, passing through the strut nearest to a copper, and another which passes through a distant strut. As the first ring is shorter than the second at thermal loading identical in both rings and identical diameters of pipes will pass on a short ring of more water, than it is required by calculation and as a result on a long ring will take place less waters, than follows by calculation. That it to avoid, it is necessary to apply to a distant strut pipes bolshego diameter, than for the nearest strut, and thus to balance resistance in both rings. At bolshej to length of pipes resistance increases, with increase in diameter of pipes it falls.
the Size of local resistance depends, vopervyh, from speed of water, hence, and from change of the section causing change of this speed (for example, in cranes, heating devices, coppers etc.), vovtoryh, from direction change on which water, and changes of a quantity of water (for example, in taps, tees, krestovinah, gates moves).
Shown on fig. 1 and the heating system is system with the top distributing . Here hot water rises through the main strut in the main pipeline laid usually on an attic.
On fig. 1 the system of heating with the bottom distributing is shown . In this system the submitting highway feeding ascending struts, settles down on the ground floor in the underground channel or in a building cellar. Return struts join the general return highway.
By a principle of action the system heating with the bottom distributing does not differ from system with the top distributing. Both here, and there circulation is created because hot water as easier, is superseded by return water upwards on struts; cooling down in heating devices, this water falls downwards through return struts and again arrives in a copper.
In systems with natural prompting in buildings small etazhnosti the size of circulating pressure is insignificant, and consequently in them it is impossible to suppose the big speeds of movement of water in pipes; hence, diameters of pipes should be big. The system can appear economically unprofitable. Therefore application of systems with natural circulation is supposed only for small buildings.
We Will list lacks of systems of heating with natural circulation of water:
- the action radius (to 30 m across) izza small circulating pressure is reduced;
- cost (to 5-7% of cost of a building) in connection with application of pipes of the big diameter is raised;
- the expense of metal and a work expense are increased by system installation;
- system inclusion in action is slowed down;
- danger of freezing waters in the pipes laid in not heated premises is raised.
At the same time, we will note advantages of system with natural circulation of water , defining on occasion its choice:
- relative simplicity of the device and operation;
- independence of action from supply by electric energy;
- absence of the pump , and accordingly, noise and vibrations;
- comparative durability (at correct operation the system can operate 35-40 years and more without major repairs);
- the self-regulation causing equal temperature of premises. In system at change of temperature and water density the expense owing to increase or reduction of natural circulating pressure changes also. Simultaneous change of temperature and the water expense provides the heat transfer of the devices necessary for maintenance of the set temperature of premises, i.e. Gives to system thermal stability.
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