Heating of the individual house - business difficult, and in each case is required to execute calculations with many indicators. In most cases the builder orders only architecturally - construction part of the project and loses sight or saves funds for development of its heattechnical part which has to be attached to real conditions and consider new materials and technologies.
The engineering system of heating includes boiler point, system of distributing of pipelines and thermal devices. That the system functioned according to modern requirements, i.e. it is comfortable, economic and reliable, the complex of engineering calculations is very important.
Calculation of thermal losses of the house has to be executed on each room separately, taking into account quantity of windows, doors, external walls. Necessary data for calculation of heatlosses:
- thickness of walls and overlappings, the material used at their construction;
- a design of a roofing covering and the used materials;
- the type of the base and material used at its construction;
- glazing type (usual windows or double-glazed windows) if double-glazed windows, then matters double or threefold;
- quantity and thickness of couplers of a floor.
It is important to consider existence in designs of the heat-insulating layer, its structure and thickness.
Sometimes selection is carried out on the integrated calculations, depending on room volume. Rooms with an identical volume can have different indicators on heatlosses if it is angular, and another the adjacent or internal room located in the southern or northern part of the house, etc.
So that to avoid insufficient warming up of rooms, builders use the traditional principle "more is better than less". In this case the quantity of radiators is increased, cost increases is equivalent to their stock on power that increases the total amount of system, so, the size of a membrane tank, power of the circulation pulser and amount of the consumed electricity. Operation of system of heating with the raised thermolysis will lead to an overheat of the house and artificial increase in heatlosses.
Hydraulic calculation of pipelines of system of heating - an important component of a complex of engineering calculations. It is necessary to determine resistance of the planned system, diameters of pipelines, pump power for circulation of the heat carrier in system. Data of calculation allows to plan the additional devices providing rational distribution of heat so that to have an opportunity completely to use their performance data. In houses from 350 sq.m in order to avoid a mistake towards deficiency of power of system diameters of pipelines of distributing of the 1st floor or the characteristic of the circulation pulser are often overestimated. It leads to rise in price of system both at cost, and in operation. Only at competent approach to design it is possible to optimize system on constructibility and expenses. Unfortunately, the consumer learns about deficiency of power of system of heating of the house only in use. And losses from alterations will be very essential. In the firms which are professionally engaged in installation of systems of heating, experts in short terms carry out development of the optimum project of system.
The economic equipment is always more expensive at an acquisition phase and installation. But over time it nevertheless pays off, but does not become a source of constant problems and expenses.
History of development of systems of heating is characterized not only the invention of new systems, but also return to use of those systems which were used earlier, but over time were forgotten. It occurs thanks to creation of the new equipment, materials and changes of service conditions.
Schemes of systems of heating are subdivided on the following indicators:
- with the top and lower eyeliner;
- vertical or horizontal;
- one-pipe or two-pipe;
- deadlock or passing.
Improvement of systems of heating happens in the different directions:
- increase of a thermolysis of heating devices;
- decrease in operational and capital expenditure;
- economy of warmth due to improvement of ways of regulation;
- increase of reliability and durability of systems of heating.
So, at a certain stage of development gravitational one-pipe systems of heating with the top distributing of the giving highway were applied. The invention of pumps allowed to pass from gravitational systems to pump one-pipe with a korotkozamykayushchy site (KZU) and to two-pipe systems.
The period of intensive development of individual housing construction promoted increase in requirement of the heating equipment.
In the market of the equipment there was a large number of import coppers for individual heat supply, reliable effective coppers of the domestic producers working at all types of fuel.
There were automatic devices on regulation of a thermolysis of heating devices, pipes on the basis of polyethylene. Pipes from the sewed polyethylene have much a smaller roughness, maintain temperature to 90 0C; they are easy, convenient in installation, are durable and maintain pressure applied in systems of heating.
These circumstances allowed to pass to design of two-pipe systems of heating.
However two-pipe systems of heating have an essential shortcoming which needs to be considered at design. It will be a question of influence of gravitational pressure upon work of system. At change of temperature of the heat carrier the system of heating can be disadjusted.
To reduce this influence and to achieve stability of work of system of heating, it is necessary that the share of gravitational pressure, in the located pressure, for each heating device made no more than 10%.
It is necessary to consider also the fact that in the course of regulation at decrease in temperature of the giving heat carrier the difference of density of the return and giving heat carriers and consequently, and gravitational pressure decreases.
For ensuring steady work of systems of heating not only at a settlement temperature of external air, but also at its higher values, in calculations it is necessary to consider not the maximum gravitational pressure, but minimum. For ensuring steady work of system of heating at big temperature differences of the heat carrier it is necessary to increase at design losses of pressure in pipelines to values which 10 times more gravitational pressure.
Now the actual moment is connection of heating devices to the operating systems of heating at reconstruction of attics under premises. At connection two options of one-pipe systems of heating with the top distributing are considered.
The first option - connection of heating devices to struts according to the flowing scheme when all heat carrier of a strut passes through the heating device. The second option - connection of the heating device with KZU.
In the first option it is simple to define a surface of the heating device if to accept the average temperature of the device close to settlement. However such decision increases losses of pressure in a strut and consequently, reduces an expense of the heat carrier passing through a strut.
In option with KZU the heat carrier expense in a strut not only does not decrease, but even increases due to increase in gravitational pressure.
Use of plastic pipes is the reason of keen interest in the low-temperature systems of panel and radiant heating (LTSPRH) which heating elements settle down in a floor design. Application of steel pipes constrained use of these systems in connection with rather short service life of the last, complexity and high cost of routine maintenance and overhaul repairs. Therefore were applied by NSPLO only in exceptional cases in premises of preschool institutions and in halls of swimming pools. Now the scope of data of systems considerably extended. It is explained by a number of advantages before traditional systems. First of all, it is sanitary and hygienic aspect.
The heated surface of a floor creates indoors the increased radiation temperature which exceeds temperature of internal air. Increase of radiation temperature in rooms with NSPLO can reach several degrees. It is explained by temperature increase of internal surfaces of protections. Intensive radiant heat exchange of a heated surface of a floor, walls and a ceiling, and also furniture and other objects is the reason of noted phenomena.
In this regard the thermal comfort in rooms with NSPLO can be provided at lower temperature of internal air (2-3 0C), than at traditional convective systems of heating.
Noted circumstance, as a rule, is not considered at design of such systems. It often leads to overestimate of power of heating panels, an overexpenditure of the most expensive elements of heating panels and pipes, the raised heat expense on heating, and in the absence of system of automatic control - to emergence of discomfort indoors.
When calculating heating panels it is necessary to consider domestic standard requirements for floor surface temperature which differ from foreign. The maximum temperature of a heated surface of a floor should not exceed 30 0C, and the average temperature of a surface 24-26 0C (for roundabout paths of pools 31 0C). Foreign requirements are on average 2-3 0C higher. Inspection of the rooms equipped with such systems showed that the average temperature of a surface of heated floors is, as a rule, higher standard on 2-3 0C.
The problem of compliance of temperatures of a surface of a floor to standard values can be solved by a variation of a step of laying of pipes, temperature and an expense of the heat carrier. The possibility of such calculation is limited to absence of reliable results of researches of process of transfer of heat in the massif of the panel with pipes or cables, and also data on coefficient of a thermolysis of a surface (Вт/м2×0С) of panels at not a uniform temperature of a surface of a heated floor. Temperature increase of panels is reached by the following decisions.
- In the thickness of the panel over heat source (a pipe, a cable) the material layer with heat conductivity coefficient less, than at the main material of the panel (concrete) is placed. The panel thermolysis at the same time increases approximately for 20-30%.
- In the thickness of the panel at the level of a pipe the metal plate (as a rule, aluminum) which coefficient of heat conduction is several times higher, than at concrete settles down. The plate plays a role of a peculiar edge. At the same time the heattechnical effect noted above is observed.
- Perhaps also combination of these constructive decisions.
The considered ways of increase of a thermolysis of heating panels did not find broad application in connection with increase in cost of systems and complication of methods of installation of heating panels so far.
From the aforesaid it is possible to draw the following conclusions:
- at reconstruction of one-pipe systems of water heating it is necessary to consider influence of gravitational forces;
- in the course of design of two-pipe systems for reduction of influence of gravitational forces it is recommended to increase the hydraulic resistance of the main pipeline;
- it is expedient to take measures for alignment of temperature of a surface of a floor for increase in efficiency of floor heating.