Water heating system refers to a heating method that heats water to a certain temperature, transports it to the water pipe cooling network under the floor, and realizes the heating purpose through floor heating.
The low-temperature geothermal medium forms a gradually decreasing temperature gradient from the sole of the foot to the head indoors, which gives people the comfort of warming their feet and cooling their heads. Radiant floor heating conforms to the fitness theory of "warm feet and cool roof" in traditional Chinese medicine. It is the most comfortable heating method at present and a symbol of modern life quality.
As far as heat medium is concerned, it can be divided into two categories: liquid circulation system and electric floor heating, and as far as pavement structure is concerned, it can be divided into wet floor heating and dry floor heating. Dry floor heating does not need to backfill peas (ultra-thin). From the surface decoration materials, it can be divided into floor floor heating and floor tile floor heating; Functionally divided into ordinary floor heating and far infrared floor heating.
Installation and commissioning
1, the low-temperature hot water floor radiant heating system has not been debugged completely, so it is forbidden to run.
2. The debugging and operation of low-temperature hot water floor radiant heating system should be carried out under normal heating and power supply conditions.
3. The initial heating (debugging) must be carried out after the curing period of the concrete filling layer is over and the filling layer is completely naturally dried.
4. The debugging of low-temperature hot water floor radiant heating system shall be carried out by the construction unit with the cooperation of the construction unit.
5. When heating for the first time, the hot water temperature should be gentle, and the water supply temperature should be controlled to be about 10℃ higher than the ambient temperature at that time, but not higher than 32℃. At this water temperature, it should run continuously for 48h；; After that, the water temperature increased by 3℃ every 24 hours until it reached the design water supply temperature. At this temperature, all components and heating pipes connected with the water collector should be adjusted one by one until they run normally.
6. The heating effect of low-temperature hot water floor radiant heating system should be based on the temperature indicated by the black ball thermometer at the center of the room 1.5m away from the ground, as the basis for evaluation and examination.
adjustment method
With the vigorous implementation of metering heating technology in China, low-temperature floor radiant heating is gradually popularized in civil buildings in China. This paper introduces the forms and characteristics of floor radiant heating system, and analyzes and studies the heating regulation methods of low-temperature floor radiant heating system.
introduce
Floor heating is a new heating method which is different from traditional radiator heating. Compared with radiator heating, it has the advantages of uniform indoor temperature distribution, good comfort, energy saving, easy household heat metering and convenient maintenance and management. With the vigorous implementation of metering heating technology in China and the increasing attention paid by the state to building energy conservation, low-temperature floor radiant heating system has been gradually paid attention to and widely used in civil buildings in China.
In the heating system, the variation law of heating heat load with outdoor temperature is usually used as the basis of heating regulation. The purpose of heating regulation is to make the heat released by the heat dissipation equipment of heating users adapt to the changing law of heat load of users and prevent the room temperature of heating users from being too high or too low. But the scene has been investigated. Some users require to change to other heating methods after only one heating period, because the room is too cold to meet the user's comfort requirements, while some users complain that the room is too hot, the room temperature reaches above 26℃, and the adjustment effect is not great, so they have to open the window, resulting in energy waste. Therefore, it is of great significance to correctly analyze the problems existing in the low-temperature floor radiant heating system, especially to understand the adjustment process of the heating system, for popularizing the application of the system and improving the heating quality.
1 Forms and characteristics of floor heating system
The form of floor heating system. Low-temperature hot water floor radiant heating is to introduce hot water with a certain temperature into the heating coil buried in the floor structure layer, and heat the floor surface through the heat transfer of the structure layer. The surface of the heated floor mainly radiates heat to the room to make up for the indoor heat loss and achieve the purpose of heating.
The heating coil in the structural layer is combined with the building structure. According to the size of the room, one room can be equipped with one or several loops, and a small room can be equipped with one loop for several rooms. The supply and return pipe of each loop are connected to the distribution main pipe, and the distribution main pipe of each user is connected to the outdoor pipe network through the supply and return pipe in the building.
Form of floor structure layer. The commonly used floor heating structure layer is concrete embedded pipe, and its main structures include floor, insulation layer, heating pipe, filling layer, leveling layer and floor surface. At the same time, thermal insulation layer should be added near the external wall to reduce heat loss. When laying directly on the ground floor or the first floor, waterproof layer should be added to prevent water from infiltrating into the soil, damaging the insulation layer and reducing the heating power.
Characteristics of floor heating system. Due to the different heating mechanisms, low-temperature hot water floor radiant heating has advantages and energy-saving effects that radiator heating, which is dominated by convection, does not have.
High comfort. The surface temperature of indoor floor is uniform, and the room temperature gradually decreases from bottom to top, giving people a comfortable feeling of warm feet and cool head; Because of the small air convection, rabbits are prevented from flying around in the dust, and the indoor environment is clean and hygienic.
The energy-saving effect is remarkable. Compared with conventional radiator heating, the indoor juice temperature of low-temperature floor radiation heating can be reduced by 1℃-3℃.
There is no pipeline equipment on the ground, which does not occupy the effective area of the room and the ground, which not only increases the usable area for users, but also is beautiful.
Easy to adjust and control. As long as the adjustment or control device is arranged on the distribution manifold. It can be easily adjusted and controlled to meet the different working conditions required by each room. Good thermal stability. The concrete in the structural layer has a large heat storage capacity, so the room temperature changes slowly and the temperature fluctuation is relatively small.
Convenient for home measurement. The heating fee in China is basically charged according to the heating building area. This method has many disadvantages. No matter what the indoor temperature is, whether it is indoor heating or not, it will be charged the same, which will lead to great waste of energy. The most reasonable charging method should be based on the actual heat consumption of each user.
Initial Adjustment Analysis of Floor Heating System
2. 1 Necessity of initial adjustment
In the traditional radiator heating system, the initial adjustment is essential, and more attention should be paid to the initial adjustment of the floor heating system. In the traditional system, if the initial adjustment is unreasonable, it can be compensated by increasing the system flow, resulting in large flow and small temperature difference operation. Although this can ensure the stability of the system, it also reduces the adjustability of the system. For the radiant floor heating system, adjustability is one of its great advantages and its foundation. The adjustment of one user will affect other users more or less. Only by doing a good job in the initial adjustment of the system can the mutual interference between users in the established pipe network be effectively reduced.
The greater the system flow, the higher the room temperature of the end users, the smaller the room temperature deviation between the near-end users and the end users, and the smaller the influence of hydraulic imbalance on thermal imbalance. The large flow operation of heating system is to eliminate the imbalance of thermal working condition level of the system by increasing the flow of end users and restraining the flow of nearby users. However, the large flow operation has not fundamentally eliminated the hydraulic imbalance of the system, and the problem of uneven flow distribution among heat users has not been solved. Large-flow operation has the following disadvantages: it reduces the ability of users to adjust independently. Need a larger water pump, consume a lot of energy, increase the initial investment and operating costs.
The initial adjustment is generally carried out before the heating system is put into operation, with the purpose of adjusting the operating flow of each heat user to the ideal flow, that is, the flow that meets the actual heat load demand of heat users. When the heating system is in the design condition, the ideal flow is the design flow. In other words, the initial regulation was mainly to solve the problem of uneven traffic distribution. Without initial adjustment, the whole heating system will be inconsistent and unbalanced, and the total flow of the system will generally exceed the designed total flow.
2.2 Initial adjustment method
There are many methods for manual initial adjustment, such as resistance coefficient method and predetermined programming method. However, due to the heavy workload of calculation or field adjustment, it is generally difficult to use in practice. In recent years, experts and engineers at home and abroad have put forward a variety of initial adjustment methods, such as proportional method, compensation method, computer method, simulation analysis method, simulated resistance method, temperature adjustment method, self-supporting adjustment method, simple and rapid method, etc., which have practical operation value in the actual heating system and are characterized by simplicity, accuracy and reliability to varying degrees.
3 adjustment method of direct-connected floor heating system
For the directly connected floor heating system, the design temperature difference between supply and return water is small, and the specification requires 10℃, so the circulating water flow of the system is relatively large. Commonly used adjustment methods are as follows:
Methods of quality management. When this method is adopted, the system always keeps the design flow running. We know that the change of water supply temperature has a great influence on the heat dissipation of floor surface. For the carpet with the smallest thermal conductivity, when the pipe spacing is 300mm, the floor surface heat dissipation will increase by 15W/m2 for every 5℃ increase in water supply temperature, while the marble with the largest thermal conductivity will increase by 365,438+for every 5℃ increase in water supply temperature.
Centralized regulation method, when this method is adopted, the circulating water volume of the system changes with the change of outdoor temperature, while the water supply temperature remains unchanged and always maintains the design value. When the circulating flow of the system is less than 50% of the designed circulating flow, the slope of the curve is large, and the change of the flow has obvious influence on the heat dissipation of the floor surface, while when the circulating flow of the system exceeds 50% of the designed flow, the change of the flow has little influence on the heat dissipation of the floor surface. This shows that for the direct-connected floor radiant heating system, only when the circulating flow of the system is small, the method of quantity adjustment can have better adjustment performance. As we know, the temperature difference between the supply and return water of the floor radiant heating system is small, and the flow required by the system is very large under the condition of constant heat load, which is 2.5 times that of radiator heating, so it is not recommended to adopt the method of quantity adjustment for the floor radiant heating system.
By changing the quality adjustment of flow in stages, the circulating flow can be reduced in several stages according to the change of outdoor temperature, while at the same stage, the circulating flow remains unchanged and centralized quality adjustment is implemented. This adjustment method is a combination of qualitative adjustment and quantitative adjustment, which can absorb the advantages of the two adjustment methods and overcome their shortcomings. Suitable for small and medium-sized heating systems that have not yet popularized variable speed pumps. Under different flow rates, the influence of water supply temperature on heat dissipation is different, and with the decrease of flow rate, this influence becomes smaller and smaller. Then when adjusting, we should try to choose a larger flow. Generally, the whole heating period is divided into three stages to change the circulating flow of the system, and changing the flow in stages depends on the parallel combination of multiple pumps.
Almost all floor heating products are imported and made in China, but the cost and price of products from different producing areas vary greatly. Because users' awareness of floor heating is not high, many floor heating companies are shoddy and fight price wars with other companies with low-priced products. General users often choose a company according to the installation cost, and as a result, they choose a product with relatively poor quality. The author has investigated some floor heating companies, some use domestic brand products as imported products, and some use foreign products that are gradually eliminated and a new generation of imported products to fight price wars. There was a complaint from the director of a company that operated world-class floor heating products. Because of such vicious competition, the company's profits were suppressed very low, and the ultimate interests were damaged by users.