Control method of system with high thermal capacity

FIELD: heating systems.

SUBSTANCE: invention refers to control method of convective heat exchange system in which heat energy is exchanged between liquid and medium. Control method of convective heat exchange system in which heat energy is exchanged between liquid and medium involves creation of liquid flow through medium, determination of value of transferred heat by adding several differences between liquid temperature at medium inlet and liquid temperature at heated medium outlet; at that, temperatures are measured in fixed time periods within fixed time intervals, determination of change of medium temperature during fixed time interval, and calculation of ratio between transferred heat and temperature variation. There also described is floor heating system and method of determining temperature of massive floor with tubes built in the floor.

EFFECT: improving available convective heat exchange systems, namely high-inertia systems like floor heating systems, which allows increasing comfort, decreasing temperature variations and increasing economy.

10 cl, 21 dwg

 

The technical FIELD

The present invention relates to a method of controlling the system of convective heat transfer, in which there is an exchange of heat energy between the fluid and the environment. The invention relates also to the heat exchanger, the heater or warm the floor, which happens this way. In particular, this invention relates also to a method of controlling the system of convective heat transfer with high thermal capacity, which is characterized as a consequence, large time constants.

The LEVEL of TECHNOLOGY

The invention can be applied to manage any systems in which there is an exchange of heat energy between the fluid and the environment, and can provide a noticeable positive effect in systems with a large time constant. As an example of such a system in the following description of the invention are mainly considered, floor heating systems. On the other hand, the invention can be applied to control the temperature of the ice rink, a swimming pool or any other system with large time constants.

Underfloor heating is becoming increasingly popular in heating systems of residential premises. Typically, such a system includes pipes, which are used in closed loop circulates water between the area of talopram, where the water absorbs heat energy, and area of heat is outdate, where thermal energy is transferred to first floor and then to the surrounding space. Usually the area talopram connected with traditional heating system, for example, boiler, heated liquid fuel or gas, or is part of such system, while the heat zone is usually embedded in the structure of the concrete floor or in such a massive structure floor with a large heat capacity, which thus results in a large value of the time constants of the heating system.

There are several ways to control the convective heat transfer in known systems floor heating. Typically, the water flows through the pipe at a fixed speed and a fixed temperature when serving. In the circuit while installing the valve that controls the amount of water that passes through the floor. In the improved system in the floor provides a circuit that is isolated from the rest of the system, with which you can control the temperature of the water flowing into the floor. In other systems, the pipe is divided into separate segments with valves to control the flow of water in each segment. The control action is usually applied on the basis of the observed difference between the actual temperature and the desired temperature of the ambient space is.

Due to the large thermal inertia is relatively a lot of time before installation of the system will affect the temperature of the floor, and still more before the installation will affect the temperature of the ambient space, i.e. at room temperature. Therefore, such systems are difficult to manage. Consequently, the heated space located in a climate with large temperature fluctuations, themselves subjected to large temperature changes. As a consequence, the operation of the system is interfaced with the high cost of heating and does not create a satisfactory environment.

Increasingly, the heat is used for floors made of materials that are sensitive to temperature extremes and high temperatures, for example for wood floors. The management of this system requires more care, and so many of the existing systems operate at relatively low temperatures, for example about 30°C. This, however, leads to a further increase in time constants, and often does not allow to counteract sudden changes in the weather. Similar problems exist in other systems, heating and cooling with relatively large time constants, for example for heating pools or cooling rollers.

Description of the INVENTION

The goal is to improve the merits of the existing systems of convective heat transfer, such high inertia systems, floor heating systems, which, in particular, allows to increase comfort, reduce temperatures and increase savings. Accordingly, according to one aspect of the invention provides a method, characterized in that the heat transferred is determined by adding several differences between the temperature of the liquid at the entrance of the heated medium and the liquid temperature at the outlet of the heated medium. Temperature is measured at fixed intervals within a fixed time interval. For a fixed interval and determine the change in temperature, and calculates the coefficient control that represents the relationship between the transferred heat and temperature change. This factor determines the total temperature difference (i.e. the sum of the difference between the inlet temperature and outlet temperature, measured over a fixed interval of time), providing a certain temperature environment, such as an increase of 1°C. at Fixed time intervals assume that the temperature is measured with a fixed frequency, for example every second, every ten seconds or every minute, within a fixed time interval. Fixed interval may be part of the best from 1 to 10, or even 100 minutes.

Using this coefficient, it is possible to obtain a specific temperature environment, relying only on measurements of water temperature at the inlet and outlet and not waiting until the ambient temperature rises. Thus the temperature can be controlled without the disadvantages associated with large thermal inertia of the medium. For example, set a specific desired floor temperature. After manufacturing floor for him is determined by its coefficient in the initial experiment, performed in accordance with paragraph 1. In the future carry out continuous control of Underfloor heating in accordance with paragraph 2, that is, measure the actual temperature of the floor and determine the temperature change required to achieve the desired temperature. Through the floor let the water and measure its temperature at the inlet and exit through the same intervals that were used in the initial experiment. Using the coefficient, determine the total temperature difference, which will provide the desired change in temperature of the floor. For example, it is desirable to raise the temperature at 4°C, and the coefficient specifies the total temperature difference between the 2500 measurements every second to achieve a temperature increase of one degree. Then to increase by 4 degrees require a total temperature difference of 10,000. By passing sorrow is her water through the floor heating system every second measured water temperature at the inlet and outlet the difference between them are, until the sum reaches 10000. At this point, the water circulation is stopped, and the transferred heat is distributed by sex, for which after some time will be achieved by increasing the temperature to the desired 4 degrees.

When pipes are laid within the floor, enters the fluid at a temperature different from the temperature of the floor, thermal energy is transferred from the liquid to the floor. In the initial period of time, thermal energy is transferred to the solid floor, for example, solid layer of concrete surrounding the pipe. At this time, thermal energy is distributed largely uniformly in all directions perpendicular to the outer surface of the pipe. In the subsequent period of time, when propagating thermal energy reaches the outer boundary of a solid floor, for example the upper surface of the floor, it starts to be transmitted to the ambient air. When thermal energy is distributed in a continuous solid material, it is fast, and the temperature quickly drops. When thermal energy is distributed in a different environment, for example by air, the surrounding floor, this is not as fast and fluid temperature decreases much more slowly. In this next period of time thermal energy spreads faster through solid concrete than h the rez transition to another environment. In this regard, the boundary between the initial and subsequent periods of time easily detected by observing the temperature of the liquid in the pipes.

According to the second aspect of the application of the invention provide a method for determining a floor temperature of the solid particulate material using the above observations. According to this method, the pipe in the floor filled with liquid whose temperature differs from the temperature of the floor. Then define a fixed point in time at which thermal energy is no longer distributed evenly in all directions perpendicular to the outer surface of the pipe. Then determine the temperature of the liquid in the pipes. From the point of view of the climate control this temperature is usually close enough to the floor temperature, and therefore can be used to control the climate near the floor. In this regard, the third use of the invention is a method of controlling the temperature in the heated or cooled space, the method is characterized in that the temperature control based on the temperature of the floor, which is determined in the manner specified in the second option.

Pipes can be filled with liquid, hot or cold relative to the floor, and the temperature difference between the water and the floor may preferably be up to 10°C or even more

In one particular implementation of the method the hot water passes through a pipe embedded in the floor, more cold than the hot water. When hot water is completely passed the pipe, i.e. when registered a significant increase in temperature at the exit of the pipe, water circulation is stopped. Due to convective heat transfer between the water pipe and a cold solid concrete water temperature decreases relatively quickly. However, the speed of the temperature expressed in degrees Celsius per unit time decreases. At a certain point in time, the speed of decrease of the temperature will decrease to a value of, for example, 50% of the speed at which the liquid temperature was decreased at the time of cessation of circulation. One of the purposes of the invention is to select a fixed point in time based on the speed at which lowers the water temperature. For example, a fixed point in time can be established when the rate will be 50% of the initial speed corresponding to the supply of hot water.

DETAILED description of the INVENTION

Next will be described a preferred embodiment of the invention with reference to the drawings, in which:

figure 1 presents the experimental setup,

figure 2 presents a scheme illustrating methods for the control of floor heating system,

figure 3 shows a model of the temperature gradient during the stages of heating and alignment for 10-inch concrete block

figs.4-6 presents the results of the step-by-step experiment conducted to estimate the heat capacity

7 shows a cross section of the concrete floor with a built-in pipe, and

on Fig shows a graph of the temperature change at the output during a certain time interval.

In the following detailed description the following symbols are used:

the stream of energy

- mass flow

CP - specific heat

ΔT is the temperature difference between the water input and output

TRef.- inlet temperature

To.the outlet temperature

h is the time interval between temperature measurements.

Underfloor heating system is installed, as shown in figure 1. Underfloor heating system mainly consists of multiple circulation paths for the water circulation pump 1, valve 2 with the actuator, sensor 3 temperature sensor 4 temperature controller 5. Figure 1 shows one of the circuits 6, i.e. a floor heating system for a room. In this system, heating water temperature at the inlet and at the outlet is measured by the sensors 4 water temperature, which the mouth of alluaudia manifolds 7, 8 and accessed from the controller 5. The temperature of the air in the room, the floor temperature and the ambient temperature are measured wireless temperature sensors 3 Danfoss, which are located indoors and which supports access via the serial interfaces. The flow of water is provided by the circulation pump 1 Gryundfos UPI or similar, which creates a constant pressure drop and provides, therefore, a constant flow of water in the circuit 6. The permeate valve 9 water is controlled by the servo motor 10, which receives control signals from the controller 5. Water is supplied from the inlet pipe 11 with hot water and returned to the outlet pipe 12. Direct control over the temperature of the concrete is due to the fact that all system components are controlled by a controller 5. The optimal operation of the control system largely depends on temperature of a large mass of concrete, as actually transmitted heat is generated due to the difference between the temperature of the concrete and the temperature of the air in the room. And dealing with the heated mass of concrete, it is necessary carefully to avoid unnecessary overheating.

Problem management immediately divided into two: the inner loop process maintains the temperature of the concrete at the desired level, and the outer contour of the PR is the set-point temperature of the concrete taking into account external conditions, see Figure 2.

If there are multiple heat sources in the control room temperature they can be used in parallel, as the set-point temperature of concrete can be expressed through thermal energy:

Similarly, other heat sources can contribute to the necessary amount of heat and have their own designation, as shown in the example:

where the source 1 may be a conventional heat sink and source 2 can be quickly triggered (i.e. with a very low time constant) fan heater.

The purpose of the control concrete temperature is to provide fast and accurate control this temperature. The main problem with this is that the temperature of the mass concrete is heterogeneous, and to measure it effectively impossible to use the sensors. We propose to apply the control scheme provides a procedure by which to evaluate the temperature of the concrete through the water outlet temperature. After calculating the temperature of the concrete can run a sequence of multiple firings. Because the estimation of heating concrete takes a long time, it is desirable to have a long duty cycle. Thus, it is proposed to calculate skolik the heat required to convey the concrete to achieve the setpoint temperature, and then pass the calculated value before the next stage of evaluation. Then the control loop can be described as follows.

The described cycle regulation assumes that we know the heat capacity (CP) of the concrete floor. Generally speaking, this is not always true, but it seems reasonable to take the heat capacity constant, so that it was possible to design an experiment that allows to assess the amount of heat that will be discussed below.

The temperature evaluation of concrete

It is assumed that for some time after discharge heat not produced any heat. When this temperature gradients concrete slowly decreased to a uniform temperature. The temperature of the hot water in the concrete, also slowly decreased until it reached a temperature of concrete. Figure 3 shows a model of the temperature gradient during the stages of heating and balance for 10-inch concrete block. The model assumes that the heating element is attached to the left side of the concrete block with an initial temperature of 20°C. In particular, figure 3 shows a slow transition to thermal equilibrium after heating water at 60°C for 40 minutes.

If the estimated value of the temperature use the temperature of the water after 15 minutes of th the heat, in this example, will get an estimated value of temperature of 26°C. From the temperature distribution immediately after heating shows that the estimated value of 26°C corresponds to the measurement at a distance of 30 mm from the heat source. The concrete at a distance of more than 30 mm has a lower temperature during heating and transition in thermal equilibrium. Thus, the average concrete temperature will be lower than the estimated value due to save thermal gradient.

Estimation of heat capacity

The purpose of the experiment is to assess the value of heat capacity, heats the concrete in the test room and watching the temperature rise of the concrete. The heat capacity can be calculated as follows:

Assuming that the flow and the time - constant value, thereby turning on the integral to discrete values, we obtain:

where

and where

h is the time interval between measurements for the i-th interval, i.e. k·h=t.

Figure 4 illustrates the experiment on heat transfer, in which water was supplied only in the surveyed premises, and the inlet valve for the hot water was opened 40 minutes. It shows the water temperature at the entrance to the contour of the space (Twater Ref.) the temperature of the water.

Figure 6 is an estimated value of heat capacity, calculated according to Equation 2, is shown as a function of time. Here, as in Figure 5, it is seen that the equilibrium temperature is not achieved. So the resulting score will be very high so long as the concrete would not be in equilibrium. The movement of heat into the environment could also affect the last part of the graph, however, experiments carried out in the steady state, demonstrated here, a much smaller drop in temperature.

In Equation 2 assumes a homogeneous temperature of the concrete. However, the problem is that to achieve a uniform temperature distribution in the concrete after heating takes a long time. The heating process causes the radial temperature gradient from the center of the heat pipe, the temperature equalization occurs very slowly.

Figure 5 shows the noise temperature of the water after completion of the heating cycle. In the first 20 minutes after heating is discontinued there is a rapid decrease in water temperature. At a certain point in time indicated by double arrow 13, the lower temperature slows down and in the next moment becomes almost linear. This can be explained by the shape of the concrete floor. At the initial stage after heating thermal energy is distributed equally in radial what's directions from the pipe, but when the heat reaches the top and bottom of the concrete, it begins to spread mainly in the hand, whereas the distribution of heat to the surface of the floor is reduced. As a result, the consumption of thermal energy is significantly reduced. This phenomenon can be used to determine the temperature of the concrete floor with built in floor pipes. According to this method, the pipe in the concrete floor fill with hot liquid and determine the point in time (hereinafter referred to as "fixed time"), in which the temperature decrease is much slower. During this time the temperature reduction rate of the fluid decreases, for example, less than 50%, in particular up to 25% of the speed at which the temperature is decreased, when stopped the hot water in the pipe. If you measure the water temperature at any point in time after a fixed time, i.e. the right of the double arrow 13, it will be approximately equal to the temperature of the floor. This method is illustrated in the following experiment, where hot water is provided in the circuit formed by the pipe 14 (see Fig.7)that is built into the structure 15 of the concrete floor. The water temperature at the outlet of the concrete floor are shown in the graph on Fig.

Initially, i.e. at time 0, the hot water enters the system. As it takes some time, so rubyville there was cold water, outlet temperature begins to rise at time and. The difference between time 0 and time and speed of the water flow can be estimated to determine the length of the pipe 14.

When the valve of the hot water closed over a short period of time begins to decrease the outlet temperature. This period depends on the flow rate and pipe length. Point b on Fig shows the moment when the temperature starts to drop.

For the first time, from b to C, the outlet temperature decreases relatively quickly. At this time, heat energy is transmitted through a mass of solid concrete in all directions. The distance traveled during the propagation of thermal energy from the pipe 14, is limited by the circle 16. Because heat is transferred through solid concrete, heat transfer occurs equally in all directions perpendicular to the outer surface of the pipe, as indicated by arrows 17 of equal length. During the second interval of time, after time, the temperature is decreased relatively slowly, while the temperature of the concrete does not reach steady state. This time period begins when thermal energy passes from the pipe 14, the distance indicated by the circle 18. At the same time in the direction of the y axis (see axis coordinate figure 7) is transmitted less energy, due to the fact that the heat transfer in this is the direction includes the transition from solid concrete to the surrounding air through the surface 19 of the floor. On Fig first period of time is limited by the points b and C, and the second starts from the point C. Because of the heat energy is transmitted with a lower speed, the slope of the curve after point with less than a to the point C.

In the following description the invention is explained in more detail.

I Introduction

Floor heating systems using water increasingly used in recent years. Distribution of floor heating is due mainly to the fact that the floor provides a more comfortable feeling (e.g., bathrooms), and in a heated room achieves a more uniform temperature distribution (due to the large heat transfer surface, i.e. the floor).

Typical floor heating system using water includes a circulation pump, which maintains the flow of heated water in the cast pipes inside floor heated rooms. In particular, each floor can be divided into the upper floor, made of wood or tiles, and the bottom floor where the concrete filled pipe with water. For each Underfloor heating has a control valve for the hot water to open and close so that the temperature of the air in the room remained close to the desired value, providing comfort.

For many years the management system under the roar of the floor with water use was based on the use of relay controllers characterized by flexibility and simplicity. Usually each room is equipped with independent relay regulator that controls the temperature of the air in the room through the control valve. In addition, the hot water temperature at the entrance floor is controlled by thermostat, which indirectly indicates that the temperature of the upper floor will not exceed the limitations due to the material (e.g. wooden floors can be destroyed), and criteria of comfort (floor does not become too hot). However, the main disadvantage is that due to the large heat capacity of the concrete bottom of the floor and limited the maximum water inlet temperature control system responds very slowly and is unnecessary overheating of the air in the room.

In order to overcome these problems we propose a new approach to the management to increase the dynamic characteristics. We offer a cascading structure of a control system with an internal circuit, the controlling temperature of the lower (concrete) floor, and the outer contour of managing the temperature of the air in the room. However, the management task is greatly complicated by the fact that the temperature of the lower floor is characterized by a certain distribution and is difficult to measure, and control valves are limited to discrete values (open/closed is). The proposed new approach to the assessment and management of the temperature of the lower floor is designed to overcome these difficulties of management. This approach eliminates overheating and allows for high temperature hot water inlet, reducing the response time of the temperature of the air.

This document has the following structure. Section II describes the plan of a typical floor heating systems using water and used test system. Section III describes the traditional setting for the control and management tasks. Section IV provides a brief description of the simplified model of floor heating systems, and in section V, the model is confirmed by experimental data. In section VI analyzes the control method and proposes a new approach to the management and evaluation of the temperature in the lower (concrete) floor. In section VII of the proposed control scheme is implemented in a test system. Conclusions are presented in section VIII.

II description of the system

Typical floor heating system using water can be divided into two parts: the water circuit and the heated floor and the room. Below we describe each of these components.

A. Water circuit

Water circuit provides a supply of heated floors warm water, stirring returning from floors with water supplied from the outside with hot water, see Fig.9. Isbutton the e amount of cold water in the circuit reset output return header.

The temperature at the entrance to the distribution manifold, and hence at the entrance to the heated floors (Tin;Icontrols thermostat valve, which regulates the amount of hot water added to the water circuit, as indicated in Fig.9.

The temperature at the inlet to the floor is measured on the discharge header. The outlet temperature is measured immediately before the valve at the exit.

B. the Heated floor and the room

Heated floor can be divided into the upper floor and lower floor. The bottom floor is usually made of concrete, which flooded the heating pipes.

Feeding in these pipes hot water, warming up the lower floor. The heat from the bottom floor is transferred to the room through the top floorthe top floor can be considered as a resistance, see Figure 10. Top floor, located above the lower floor, is made, for example, from wood, tile, etc.

The temperature of the air in the room (Tdmeasure a temperature sensor, usually mounted on the wall of this room. The results of these measurements are used to control room temperature. Figure 10 also illustrates the possible disturbances during temperature control. To obtain the experimental results were used to test the system, Imelda the above-described properties.

III Description of the complexities of management

The complexity in the management of the Underfloor heating system can arise in the solution of the following two tasks: the rejection of disturbances and for adherence to the specified value. In most homes the setpoint temperature is mostly constant and varies only in times of departures, such as vacations. When increasing the set value occurs, the task as quickly as possible to reach the new setpoint, without overheating. Rejection of disturbances is the most difficult problem nowadays. Often as the sole source of perturbations considered only the weather, but the factors that create disturbances are also additional heat sources, as well as fluctuations in temperature and water pressure at the inlet. Climatic perturbations caused primarily by fluctuations in the ambient temperature, however, a certain role is also played by the wind and radiation. Other disturbances may also include solar radiation passing through the window, burning wood in the stove, the heat dissipation from the people and so on (see Figure 10).

Figure 11 shows a floor heating system in a typical control system, where the drive is output valve, for which the temperature of the air is used directly as the feedback control is about the principle of the relay. This approach has inherited some old problems. The main problem associated with the perturbation is large unmanaged heat capacity of the concrete floor, which makes it difficult to compensate the fluctuations in weather conditions and other sources of heat. Under the existing approach relay, you must wait until the temperature falls below the setpoint, then open the control valve. After that, the temperature of the concrete bottom of the floor will rise to a level at which the concrete will be able to adapt to the increased heat load. Because of this, an unwanted dip in temperature until the temperature of the concrete rises. Such problems can occur in the early days, when rapidly increasing ambient temperature. Solar radiation passing through the window, can very quickly reduce the need for heat. Even when the control system closes the inlet valve when the preset value of the internal temperature, the heat warm the lower floor will still further increase the temperature in the room. The severity of these problems largely depends on thermal resistance of the floor. In case of high thermal resistance of the floor, such as wood, to provide the necessary heat required much bol is f high temperature of the lower floor, than in the case of floors with low thermal resistance (e.g., tiles). Wooden floor also has a temperature limit, failure to comply with which it will be destroyed. Manufacturer of wooden floors Cancers Ltd. [1] recommends that you set a limit on the temperature of the concrete at the level of 37.5°C, which under the existing management systems leads to the restriction of water inlet temperature and, consequently, limit the possibility to quickly change the temperature of the concrete.

IV Modeling

The object model is the heated floor and the room. For these objects are characterized by the slowest dynamics, which imposes limitations on the dynamic characteristics of the control system. The dynamics of the water circuit is much faster than the dynamics of the heated floor, and therefore we neglect it, considering how static.

The floor model and the heated room can be divided into 3 parts: the lower floor, the upper floor and the room. The relationship of these 3 parts is depicted in Fig.

Concrete lower floor is heated by hot water, which circulates through the floor, i.e. by heat transferfrom the water to the concrete. The temperature difference between the top layer bottom floor Ttop.and the ambient temperature TPDMindoors creates a heat transferfrom the bottom floor to the zdwhu the room through the upper floor. While the temperature is determined by the amount of heatreceived from the floor, andobtained from disturbance.

Next, we present the model for each of the 3 parts shown on Fig.

A. the Lower floor

A relatively thick layer of concrete, low heat transfer from the concrete to the room and the low thermal conductivity of concrete is given a high value Bio>>1, i.e. the temperature of the concrete should not be considered uniformly distributed, therefore, should be used in a distributed temperature model [2]. To simplify the modeling, concrete lower floor is divided into several volumes with uniform temperature. Since the temperature gradient is changed in the radial direction from the heating pipes in the concrete, the concrete is divided into n+1 ring volume with the same thickness L (see Fig).

The last upper layer (n+1) has the form of a ring, but, nevertheless, considered to have a uniform temperature. When the heat transfer from water to concrete the temperature of the water and concrete decreases along the length of the pipe. This feature can be modeled by "cutting" concrete lower floor along the pipe m slices, as shown in Fig.

However, heat transfer between separate these sections are neglected. In addition, it is assumed that the "top of the Loy concrete" in all slices have the same temperature, i.e. can be considered as a single entity. In General this gives a two-dimensional model, as shown in Fig and 14.

Next, we denote the element at the i-th slice of the j-th layer as Ei;j. This means that Ti;j is the temperature of cylindrical concrete element (i;j) and- the flow of heat from the cylindrical element (i;(j-1)) K (i;j); note thatdenotes the heat flow from the outlet of the first pipe with water to the layer (i;1) concrete. Tin, I., iindicates the temperature of the water at the entrance to the i-th slice of the pipe. Tin, o., iindicates the temperature of the water at the output of the i-th slice of the pipe.

Using these symbols, the heat fluxcan be expressed as follows:

where Rin b- thermal resistance at the transition from water to concrete, Ai;j is the surface area between the element (i;j-1) and (i;j), and K is thermal conductivity of concrete. The total heat transferred to the water, will be

Temperature Ti;j can be determined using the relation:

where Cfb- specific heat of concrete, a mij is the mass of the element (i;j).

Because the top layer of concrete is considered as a single entity, the temperature of this layer is assumed homogeneous, hence, it can be calculated from the formula:

The water temperature at the exit of the slice i is determined by the formula:

where Cfin- the specific heat of water andthe mass flow of water; the water temperature at the entrance to the i-th slice TV;I.;j is calculated using the formula:

where Tin the entry.- the water temperature at the inlet to the floor, and Tin,o.=Tin,o.,mthe outlet water temperature from the floor.

C. the Top floor and the room

The heat capacity of the upper floor we neglect, as it is much smaller than the heat capacity of the lower floor. The flow of heat from the concrete to the room when passing through the upper floor is easy to calculate, considering the upper floor as a thermal resistance, ie,

where Rb PDM- thermal resistance from the top layer of concrete to the air, and TPDMthe temperature in the room.

Finally, you can calculate the temperature inside, considering it is homogeneous (i.e. assuming perfect mixing of the air) as follows:

where- the net heat loss from the room to the environment,

CfPDM- specific heat of air, and mPDM.- the mass of the air in the room.

Connecting the model, as shown in Fig received General fashion the ü.

V Proof model

Confirmation of the model by comparing the experimental data obtained on a test system of floor heating, with the data of the mathematical model. The experiment was conducted in the test area of 16 m2with concrete floors, 10 cm thick, in which are embedded pipes with water in the ratio of 4 m m2.

In the experiment, the hot water blowing into the floor for 1 hour. Then heat the valve was closed and the water is circulated in the floor, without receiving additional heat. Measuring temperature curve for water outlet, see solid line on Fig. The dashed line denotes the temperature of the water at the entrance. Using the model the same water inlet temperature and the same initial conditions, we can calculate the temperature of the concrete, which is denoted by a dashed line. From Fig shows that the temperature of the water in the test system and the model are very close. This demonstrated that the model very well describes the temperature distribution in a real system the floor, and the water outlet temperature equal to the temperature of the warm layer in the concrete.

On Fig shows how in the course of the same experiment changing the temperature of the water when in the same room change design parameters of the floor. It was an attempt to investigate how the and features floor heating systems affected by changes in the thickness of the bottom floor and the length of the pipes with water. Theoretically, for the space of 16 m2with a concrete bottom floors and wooden upper floors, the water temperature at the outlet of the concrete bottom thickness 5 cm and 10 cm thick should be the same at the first stage of the experiment, when the floor is pumped hot water. When a heat wave in 5-centimeter lower floor reaches the surface of the concrete (approximately half an hour), the overall temperature of the concrete begins to grow faster than the 10-centimeter thickness of the bottom floor. This is because the large thermal resistance of the wooden upper floor substantially prevents heat transfer into the room. When the discharge of heat is terminated, the temperature of the water in both systems is reduced, however, after about 4.5 hours at the temperature of 5 cm lower floor will be lower than 10 cm lower floor because of less heat capacity.

If in the same room in the lower floor are placed tube twice the length (8 m on m2), the outlet water temperature will be lower than in the case of pipe length 4 m m2. This is because the heat transfer from the water to the concrete is twice as much to the bottom floor comes more heat. When the discharge of heat is stopped, the outlet water temperature decreases more slowly than in the case of 4 m m2on the WMD that the distance between the pipes is less and the temperature of the concrete rather comes into balance.

The results of mathematical modeling, presented at Fig, give a good idea of how the various design parameters of the lower floor are changing the nature of the distribution of floor temperature. This information will be useful later, when the proposed method of control will be discussed in General.

VI a New approach to management

The proposed control method, which is illustrated in Fig involves dividing the problem into two parts: an inner control loop that supports the desired temperature of the concrete, and the external circuit that controls the temperature of the room.

In General, the method can be described in three repetitive steps.

1. Evaluation of the temperature of the concrete at the momentconcrete (t).

2. Calculate the amount of heat, ONan.that will be introduced to bring the temperature of the concrete to the specified value.

3. Transfer the required amount of heat.

A. assessment of the temperature of concrete

Installing the temperature sensor in the concrete layer was unsuitable for a number of reasons. First, the sensor is placed in the concrete layer, it is difficult to maintain and replace, especially if it is a wooden floor. Secondly, very significantly the location of the sensor. If it is placed next to the pipes, it will be very quick to react to heat. Elago be placed in the middle between the two pipes, he will not respond until thermal gradient reaches the most remote from the pipe.

For system control, you could use two estimates: the temperature, which describes the amount of heat transferred to the room (Ttop.), and the maximum surface temperature of the concrete, which is important to account for the limitations that arise when using wooden floors.

We propose to estimate the temperature of concrete to use the temperature of the water. At the end of the idle period without heating temperature of water and concrete are aligned. If we measure the temperature of the water after this idle period, the measurement result will correspond to the warmest place in the concrete, which is closest to the water pipes. If we extend the idle period, the temperature gradients in the concrete will be less and the measurement will give a lower value of the temperature, as is clear from the temperature curve after injection of heat on Fig.

B. Assessment of thermal capacity of concrete

We offer based on experimental data approach, which allows to obtain a "dynamic" heat capacity of concrete. The main idea consists in performing the experiment, in which we report a known amount of heat QNan.and measure the temperature increase ΔTconcrete. The heat capacity of Cfconcrete

Fig illustrates such an experiment, carried out on our test installation. In the initial phase after heat-pump (t=68 min) water temperature decreases rapidly. After the initial stage, the temperature drop is much lower, reflecting the transition of the temperature gradient of the phase radial distribution in the transverse phase distribution. We can expand Equation 9, by adding a dynamic heat capacity:

values which are deposited along the secondary axis on Fig. The value of the dynamic heat capacitydescribes the equilibrium level, not the actual heat capacity of the concrete floor.

The temperature distribution in the concrete, where the closest to the pipe layers are the most warm, ensures that the estimated value of the dynamic heat capacity is always less than the actual capacity.

VII Results

In experiments 1 August received some results with the new method of control involves the control of the temperature of the concrete, and through it, the temperature of the room. The experiment was started from cold floors (23,5°C) when the outdoor temperature is around 17°C. during the whole experiment the set-point temperature was set to 23.5°C.

On Fig is provided to the water outlet temperature, estimated value of the temperature of the concrete and the temperature of the insulated floor. The temperature of the insulated floor is measured when placing a temperature sensor between the floor and the insulation material. In steady state, the measured temperature value is very close to the temperature of the top layer of concrete. The temperature of the concrete is calculated by the method proposed in section VI. It is seen that initially, when a large temperature gradient, the rise of temperature of the top layer of concrete, and then, when the gradient is small, the temperature of the top layer of concrete is quite in line with the estimated values. Since the temperature of the top layer of concrete is lower than the average temperature of the lower floor, there is a temperature gradient between the temperature of the top layer of concrete and an estimated temperature value.

On Fig the control and estimates the temperature of the concrete. First, when the reference value is significantly higher than the estimates, the temperature of the concrete is growing quickly, but the temperature control unit concrete constraint in the heat transfer to the concrete, thus increasing its temperature by 3 degrees. After that, when the control temperature is below the estimates, the heating is discontinued and the temperature of the concrete is reduced until he is below the control temperature, and then heating starts again. In atamasthana control and the estimated temperature is very close, that shows that the concrete temperature can be controlled.

On Fig shows the distribution of temperatures of the concrete floor in the described experiment. In the experiment the aim was to maintain the temperature of the concrete floor at 30°C by opening and closing the circuit, heating the floor. We can see the temperature distribution in different layers. Layer 1 of the concrete closest to the pipe with water. Layer 2 concrete is farther from the pipe than layer 1. The top layer is adjacent to the floor, as shown in Fig.

VIII Concluding remarks

The purpose of this paper was to present and evaluate the proposed method of controlling the temperature in the Underfloor heating system using water. Discussed the problems inherited in this way, specified and validated experimental data model finite elements for the concrete floor. The proposed method is based on a cascade scheme was verified in the real application. The simulation results help to clarify the results of an experiment demonstrating how different concrete layers react to the proposed management approach. The main conclusion is that the control circuit is capable of rapidly and precisely control the temperature of the concrete, without overheating. It is possible to estimate the temperature of the concrete, using the temperature section is usausausa from the system water.

Literature

1. Junckers Ltd., the QR Transformation 1, junckers.techinfo.wp.dk/PDF/E40uk.pdf, E 4.0 Solid Hardwood Flooring. General Information. Underfloor heating.

2. Yunus A. Cengel and Robert H. Turner. Fundamentals of thermal-fluid sciences. McGraw-Hill, 2005.

1. The method of controlling the system of convective heat transfer, in which there is an exchange of heat energy between the fluid and the environment, including:
creating a fluid flow through the environment,
determination of the magnitude of heat transferred by the addition of several differences between the liquid temperature at the inlet of the environment and the temperature of the liquid at the outlet of the heated medium, and the temperature is measured at fixed intervals within a fixed time frame,
the definition of change of temperature for a fixed time interval, and
the calculation of the ratio between the transmitted heat and temperature changes.

2. The method according to claim 1, which includes:
determining the difference between the desired temperature and the actual temperature environment
providing, by the found values of the difference and the relationship between the transferred heat and temperature change, the amount of heat required to raise the temperature from the actual temperature to the desired,
providing a fluid flow through the environment while simultaneously determining the amount of transferred heat by adding multiple differential is th between the temperature of the liquid inlet and the liquid temperature at the outlet, moreover, temperature is measured at fixed time intervals, and
the defining moment when the transferred heat is sufficient warmth.

3. The method according to claim 2, characterized in that the temperature of the medium is determined by measuring the temperature of the liquid after a time interval during which the fluid flow was absent.

4. Underfloor heating system, including pipe embedded in the floor, and containing entrance, provided with a device for temperature measurement on the input, the output, to measure the temperature at the outlet, means providing circulation of liquid in the pipeline and the processing means designed to control the fluid in accordance with the method according to any one of claims 1 and 2.

5. The system according to claim 4, intended to determine the desired amount of heat to transfer from the floor to the environment, and on the basis of this number to determine the desired floor temperature.

6. System according to any one of claims 4 and 5, including several paths connected in parallel between input and output, characterized in that each circuit is independently connected to the fluid flow between input and output that allows you to control the amount of heat transmitted separately in each loop.

7. The method of determining the temperature of a massive floor with built in floor pipes, including the following ø the guy:
filling the pipe with fluid, whose temperature differs from the temperature of the floor,
the definition of a fixed point in time at which thermal energy is no longer distributed evenly in all directions perpendicular to the outer surface of the pipe,
measuring the temperature of the liquid in the pipes at some point in time after a fixed time, and
an approximate calculation of the floor temperature measured by the temperature.

8. The method according to claim 7, characterized in that the liquid temperature is not more than 50% of the floor temperature, or Vice versa, the floor temperature is not more than 50% of the fluid temperature, measured in degrees Celsius.

9. The method according to any of claims 7 and 8, characterized in that the fixed time is determined on the basis of the speed at which changes the temperature of the liquid.

10. The method according to claim 9, characterized in that the fixed point in time represents the moment when the rate of change of temperature of the liquid is reduced to 50% from the rate at which liquid temperature was changed immediately after filling the tube with liquid.



 

Same patents:

FIELD: power engineering.

SUBSTANCE: heat electric power supply system consists of heat energy use sub-system, straight and return main pipelines of heat network, circulation circuit of heat carrier of centralised heat supply at least with one heating unit of the building, and electric power supply sub-system. At that electric power supply sub-system consists of power plant; power lines; at least one liquid transformer consisting of at least one winding; tank with transformer liquid; circulation pump; and separating heat exchanger the secondary circuit whereof is equipped with circulation pump. When the above circulation pump is in operation, heat carrier of secondary circuit of separating heat exchanger is supplied to one heating unit of the building, which is connected to secondary circuit of separating heat exchanger. Version of heat electric power supply system is described as well.

EFFECT: improving efficiency, ecological properties and reliability of the system, fuel calorific capacity fully used by centralised heat supply source, and effectiveness of heat removal from transformers, reducing temperature loads on electrical part of the system during intense ambient temperature decrease, cost of operation and overall dimensions of electrical transformers.

3 cl, 3 dwg

Heating system // 2315243

FIELD: heating engineering.

SUBSTANCE: heating system comprises round or elliptic inner passage for fluid, top and bottom plates that face each other and define an inner passage for flowing the heat-transfer water, a number of connecting members, inner passage for water made in the plates by means of connecting members, and two sections for transporting fluid for supplying and discharging water.

EFFECT: enhanced efficiency.

10 cl, 13 dwg, 1 tbl

The invention relates to a heating system that uses a heating plate panel

The invention relates to the field of heat transfer and can be used for space heating

The invention relates to the breeding of sheep, in particular to devices of growing lambs in the winter and early spring cattle

The invention relates to a power system, in particular to a district heating residential, public and industrial buildings and structures

Block heater // 2135899
The invention relates to a heating engineer and can be used in heating of private houses and cottages

The invention relates to a heating engineer vehicles, in particular to heating systems cabins of trucks plying on long distances

Heating system // 2315243

FIELD: heating engineering.

SUBSTANCE: heating system comprises round or elliptic inner passage for fluid, top and bottom plates that face each other and define an inner passage for flowing the heat-transfer water, a number of connecting members, inner passage for water made in the plates by means of connecting members, and two sections for transporting fluid for supplying and discharging water.

EFFECT: enhanced efficiency.

10 cl, 13 dwg, 1 tbl

FIELD: power engineering.

SUBSTANCE: heat electric power supply system consists of heat energy use sub-system, straight and return main pipelines of heat network, circulation circuit of heat carrier of centralised heat supply at least with one heating unit of the building, and electric power supply sub-system. At that electric power supply sub-system consists of power plant; power lines; at least one liquid transformer consisting of at least one winding; tank with transformer liquid; circulation pump; and separating heat exchanger the secondary circuit whereof is equipped with circulation pump. When the above circulation pump is in operation, heat carrier of secondary circuit of separating heat exchanger is supplied to one heating unit of the building, which is connected to secondary circuit of separating heat exchanger. Version of heat electric power supply system is described as well.

EFFECT: improving efficiency, ecological properties and reliability of the system, fuel calorific capacity fully used by centralised heat supply source, and effectiveness of heat removal from transformers, reducing temperature loads on electrical part of the system during intense ambient temperature decrease, cost of operation and overall dimensions of electrical transformers.

3 cl, 3 dwg

FIELD: heating systems.

SUBSTANCE: invention refers to control method of convective heat exchange system in which heat energy is exchanged between liquid and medium. Control method of convective heat exchange system in which heat energy is exchanged between liquid and medium involves creation of liquid flow through medium, determination of value of transferred heat by adding several differences between liquid temperature at medium inlet and liquid temperature at heated medium outlet; at that, temperatures are measured in fixed time periods within fixed time intervals, determination of change of medium temperature during fixed time interval, and calculation of ratio between transferred heat and temperature variation. There also described is floor heating system and method of determining temperature of massive floor with tubes built in the floor.

EFFECT: improving available convective heat exchange systems, namely high-inertia systems like floor heating systems, which allows increasing comfort, decreasing temperature variations and increasing economy.

10 cl, 21 dwg

FIELD: heating systems.

SUBSTANCE: invention refers to heating equipment, namely to radiant heating systems, and can be used for keeping temperature mode in domestic and public buildings during winter period. Radiant panel device contains one or several heating panels with heat-release surface and heat generator; heating panel includes closed circulation loop filled with working medium in the form of liquid and its vapours, in which there is the following: condensation section having thermal contact with heat-release surface of heating panel; evaporation section interconnected with it and having thermal contact with heating device of heat generator; accumulation-and-displacement section interacting with evaporation and condensation sections and having thermal contact with device of cyclic heating of accumulation-and-displacement section to the temperature exceeding temperature of the rest sections of circulation loop and cyclic cooling of accumulation-and-displacement section to the temperature not exceeding temperature of the rest sections of circulation loop. The device located between accumulation-and-displacement section and condensation section and allowing movement of working medium from condensation section to accumulation-and-displacement section and preventing, completely or partially, movement of working medium from accumulation-and-displacement section to condensation section. The device located between accumulation-and-displacement section and evaporation section and allowing movement of working medium from accumulation-and-displacement section to evaporation section and preventing, completely or partially, movement of working medium from evaporation section to accumulation-and-displacement section.

EFFECT: increasing efficiency of heat transfer from heating device of heat generator to heat-release surface of panel.

17 cl, 2 dwg

FIELD: machine building.

SUBSTANCE: procedure for production of multi-layer sectional heating panel consists in: stacking layers of sound and moisture proof material and porous heat insulation material on base of synthetic resin one on another. A row of shock absorbing poles passes through layers at specified horizontal step; the poles have metal protective caps on their upper parts. Layers are stacked on a bearing device on the first worktable. The bearing device is designed for transfer together with a fabricated heating panel along worktables set successively along a work line. Further, the procedure consists in matching and connection of a lower heat accumulating plate to upper surface of heat insulating material on the second worktable; in matching and connection of a heat conducting steel plate to upper surface of the lower heat accumulating plate on the third worktable; in matching and connection the upper heat accumulating plate to upper surface of the heat conducting steel plate on the fourth work table; in making holes for rivets by drilling the upper and lower heat accumulating plates, heat conducting steel plate and upper parts of corresponding protective caps put on upper parts of shock absorbing poles on the fifth worktable; in setting rivets into holes on the sixth work table; in riveting with a riveting machine on the seventh worktable for through connection with rivets via holes made in the heat conducting steel plate and holes in an upper part of the protective caps of the shock absorbing poles thus producing a finished heating panel of several layers combined into an integral one; and in transporting the finished panel from the eighth worktable with a transporting device.

EFFECT: ease at construction and operation, raised efficiency at fabrication of great number of multi-layer heating panels.

4 dwg

FIELD: heating.

SUBSTANCE: formation method of multi-purpose plastic panel for its being used for room heating and cooling is characterised with installation in panel of upper and lower plates one opposite another so that cavities are formed between them, and with installation of headers for arrangement of heat carrier movement in end parts of the panel. Layers of plates, which form cavities are made in the form of honeycomb cells using at least one layer, around which on external layer there formed is honeycomb cells in the form of extended functional channels using at least one layer for the purpose of their being used for arrangement of heat exchange, and to headers by means of nozzles there connected are pipelines of heating and cooling systems; at that, some part of cells of external layer are plugged on the side of heat carrier headers and to them by means of vertical channels there made is air supply and discharge line from ventilation system.

EFFECT: providing the functioning of panel both of heating and cooling systems, possibility of using the panel as independent finishing material for room finishing.

5 cl, 6 dwg

FIELD: heating.

SUBSTANCE: heat-insulating panel assembly includes the following: a variety of panels; the first and the second hot water supply tubes installed separately inside the panel to provide at least two hot water passages; and the first and the second connection assemblies provided in the panel for connection to a boiler or to the first and the second hot water supply tube for water circulation in the first and the second hot water supply tubes. According to the present invention, two hot water tubes provide different hot water passages inside the panel used for heating of a room.

EFFECT: improving heating efficiency; simplifying manufacture of a double structure of hot water supply tubes with improved stability to temperature variations and corrosion; possibility of choosing a configuration, a pitch and a shape of tubes without any restrictions owing to using as a tube material the thermoplastic elastomer with a polybutylene layer on inner surface, as wells reducing the diameter and length of hot water supply tubes installed in the panel, due to which thickness of the panel is reduced and the boiler load is minimised.

7 cl, 15 dwg

Heating device // 2535296

FIELD: power industry.

SUBSTANCE: invention relates to heat power industry and can be used in technologies of independent heating and hot water supply of individual houses, industrial buildings and facilities. A heating device includes an insulated housing with a furnace chamber arranged in it and provided with atomisers above which a heat exchanger with heat carrier inlet and outlet and a flue gas collector is installed. Additionally, the device is provided with a thermoelectric converter arranged in the furnace chamber, the outlet of which is connected through an in-series connected voltage inverter and a switching apparatus to a feed circuit of a delivery pump and an ozone plant connected by means of an air duct through the delivery pump to the furnace chamber.

EFFECT: invention allows reducing natural gas consumption by 15…20%, as well as considerably reducing toxicity of combustion products owing to reducing content of carbon and nitrogen oxides in them.

1 dwg

FIELD: power industry.

SUBSTANCE: technical solution relates to power systems and can be used for heating of premises by accumulation of energy and its use in heated floor systems. The technical result is achieved by that in the building heating system containing the heat generating unit and heating sections designed from the pipes interconnected among themselves, located in a floor the cavity of which is filled with the liquid heat carrier, and the heat generating unit is fitted with the mains power switching unit connected to the heat carrier temperature sensor, the input branch pipe of heating sections is connected to the output branch pipe of the heat generating unit, and the output branch pipe - to the input heat generating unit, and the heat generating unit consists of an electric boiler and thermal energy storage canister or of the thermal energy storage canister with tubular electric heaters, the mains power switching unit of the heat generating unit is designed as a control unit which enables heating mode of the heat carrier at the beginning of the period of reduced rate for electric power and disables when the heat carrier is heated up to 85°C, and the input branch pipe of heating sections is connected to the output branch pipe of thermal energy storage canister through the thermostatic mixing valve connected through the pipeline with the return pipeline of heating sections..

EFFECT: technical result of the offered technical solution is depreciation of operation of heating systems.

2 dwg

FIELD: heating.

SUBSTANCE: radiator comprises horizontally heating pipes installed with extreme sections bent upwards connected by adapters. Bent sections form air cavities compensating volume of freezing water. Besides, heating pipes have heat removing ribs, which reduce their size from the middle of the pipe to its ends, which prevents radiator break with increased length of the heating pipe.

EFFECT: in case of a heating system emergency cost of emergency-recovery works reduces significantly.

1 dwg

Up!