ITBO20120040A1 - METHOD FOR ADJUSTING THE RETURN TEMPERATURE OF THE CIRCULATING FLUID IN A HEATING SYSTEM AND THE AMBIENT TEMPERATURE OF AT LEAST ONE LOCAL HEATED BY SUCH HEATING SYSTEM - Google Patents

Description

DESCRIPTION

of the patent for industrial invention entitled:

"METHOD FOR ADJUSTING THE RETURN TEMPERATURE OF THE CIRCULATING FLUID IN A HEATING SYSTEM AND THE AMBIENT TEMPERATURE OF AT LEAST ONE ROOM HEATED BY THIS HEATING SYSTEM"

The present invention relates to a method for regulating the return temperature of the circulating fluid in a heating system and the ambient temperature of at least one room heated by this heating system, and also relates to a corresponding heating system.

In particular, the present invention finds advantageous, but not exclusive, application in heating systems which include, as means for heating the fluid to be fed to the radiators, a condensing boiler or a heat pump, to which the following description will explicitly refer without losing generality.

In a typical heating system comprising a condensing boiler, the fluid that is heated and fed to the radiators essentially consists of water. The radiators are made of cast iron, aluminum or steel alloys. There is usually at least one radiator in each room to be heated. This heating system comprises a pumping system, which comprises one or more pumps normally distributed along a delivery portion of the hydronic circuit to feed the fluid to the radiators, and a plurality of thermostatic valves, each of which is arranged at the inlet or at the outlet of a respective radiator. The thermostatic valves are manually operated by the user to set the desired room temperature in the relevant room. Thermostatic valves are mechanically controlled valves according to the user's settings to vary the water flow rate in the radiator and therefore regulate the radiator power. When the ambient temperature tends to rise compared to that set by the user, the valve closes to let less water pass through the radiator, thus reducing the power supplied and therefore decreasing the temperature of the water leaving the radiator.

The efficiency or performance of a boiler is measured as the ratio between the thermal energy supplied to the hydronic circuit and the quantity of calories equivalent to the quantity of fuel burned. The efficiency of a boiler measured in this way is also known as "efficiency". The efficiency or performance of a heat pump is measured as the ratio between the thermal energy supplied to the hydronic circuit and the work done to obtain this thermal energy. The efficiency of a heat pump calculated in this way is also known as the "coefficient of performance" (COP). The efficiency of a condensing boiler is greater the lower the water return temperature, i.e. the temperature of the water entering the boiler. The efficiency of the pumping system generally depends on the efficiency of the pumps, the density of the fluid circulating in the hydronic circuit and the characteristics of the hydronic circuit. The efficiency of the heating system depends on the efficiency of both the boiler and the pumping system and, in general, is equal to a large percentage of the efficiency of the boiler.

One of the drawbacks of the heating system described above is that the return temperature is uncertain, because the water temperature at the outlet of the radiators differs from one radiator to another, due to the possible different types of radiators, the conditions climatic conditions in each room and the user settings made on each thermostatic valve. It is therefore not possible to maximize the efficiency of the boiler.

Another disadvantage of the heating system are the rather long response times, especially in the start-up phase of the system. In fact, at start-up all the thermostatic valves open simultaneously and the system flow rate reaches the maximum value, but the flow rate for each radiator is limited. Furthermore, the response times increase as the quantity of water contained by the radiator and the temperature difference between the inlet and outlet of the radiator increase.

In addition, the thermostatic valves allow to regulate the room temperature room by room, without however there being any connection between the individual rooms, as the regulation is mechanical and each thermostatic valve performs its own regulation independently from the others. . Consequently, it is impossible to privilege one room over the others only at certain times of the day, for example when the system is started up in the morning.

A known variant of the heating system described above comprises, instead of the boiler, a heat pump. The heat pump has a very high efficiency if it is possible to make it work in the so-called "sub-cooling" regime of the refrigerant fluid that circulates in the internal circuit of the heat pump. In other words, the efficiency of the heat pump is very high if the water return temperature, i.e. the temperature of the water coming from the radiators and returning to the refrigerant / water heat exchanger of the heat pump, is lower. at the condensation temperature of the refrigerant fluid.

However, the aforementioned drawbacks for the system with condensing boiler are not, in practice, solved by the use of the heat pump, due to the difficulty of maintaining the return temperature sufficiently low. Furthermore, the efficiency of some types of heat pumps drastically drops during the start-up phase of the heating system.

The purpose of the present invention is to provide a method for regulating the return temperature of the fluid in a heating system and, at the same time, to keep the ambient temperature under control in the rooms heated by this heating system, and to realize a heating system implementing this method, which method and plant are free from the drawbacks described above and, at the same time, are easy and economical to implement.

In accordance with the present invention, a method is provided for regulating the return temperature of the circulating fluid in a heating system and controlling the ambient temperature of at least one room heated by this heating system, and a heating system, as defined in the claims attached.

The present invention will now be described with reference to the attached drawings, which illustrate a non-limiting example of embodiment, in which:

- figure 1 illustrates the heating system realized according to the dictates of the present invention; and - Figures 2 and 3 illustrate the performance curves of the radiators and of the heat generator of the heating system of Figure 1 used to determine reference values for the flow and return temperatures of the fluid, according to the regulation method supplied with the present invention.

In Figure 1, 1 generally indicates, as a whole, the heating system made according to the present invention. The heating system 1 comprises one or more radiators 2, each of which is arranged in a respective room (not shown) to be heated, a heat generator 3 consisting, for example, of a condensing boiler or a heat pump, to heat a heat transfer fluid, for example a fluid essentially consisting of water, to be fed to the radiators 2, a fluid transport circuit divided into a delivery portion 4 to convey the hot fluid from the outlet 3a of the heat generator 3 to the inlets 2a of the radiators 2, and a return portion 5 for conveying the cooled fluid from the outlets 2b of the radiators 2 to the inlet 3b of the heat generator 3. Since the heat carrier fluid considered is water-based, the fluid transport circuit will be here hereinafter called, for simplicity, hydronic circuit.

The delivery portion 4 of the hydronic circuit comprises a main branch 6 connected to the output 3a of the heat generator 3 and secondary branches 7 to connect, each, the main branch 6 to the inlet 2a of a respective radiator 2. The return portion 5 of the hydronic circuit comprises a main branch 8 connected to the input 3b of the heat generator 3 and secondary branches 9 to connect, each, the output 2b of a respective radiator 2 to the main branch 8. The heating system 1 comprises a pump 10 arranged in a point of the main branch 6 to circulate the fluid along the entire hydronic circuit, from the outlet 3a to the inlet 3b of the heat generator 3, passing through all the radiators 2.

In this document, by delivery temperature we mean the temperature of the fluid at the outlet 3a of the heat generator 3, i.e. substantially the temperature of the fluid in the main branch 6 of the delivery portion 4 of the hydronic circuit, and by return temperature we mean the temperature of the fluid at the inlet 3b of the heat generator 3, ie substantially the temperature of the fluid in the main branch 8 of the return portion 5 of the hydronic circuit.

With reference to Figure 1, according to the invention, the heating system 1 comprises a plurality of electronic valves 11, each of which is associated with a respective radiator 2 and comprises a respective hydraulic valve 12 for regulating the flow rate of the fluid through the radiator 2 and a respective control unit 13 for controlling the hydraulic valve 12 as a function of input signals. The electronic valves 11 are of a type known per se and therefore are not described in further detail. In the embodiment of Figure 1, the electronic valves 11 are arranged in the return portion 5 of the hydronic circuit. In particular, the hydraulic valve 12 of each electronic valve 11 is arranged in a respective secondary branch 9 of the return portion 5, that is, in the secondary branch 9 connected to the output 2b of the respective radiator 2. More precisely, each electronic valve 11 has the own hydraulic valve 12 connected to the outlet 2b of a respective radiator 2.

Furthermore, the heating system 1 comprises a plurality of fluid temperature sensors 14, each of which is associated with a respective radiator 2 and is arranged in the secondary branch 9 which is connected to the outlet 2b of said radiator 2 to measure the temperature of the fluid leaving the radiator 2, and a plurality of ambient temperature sensors 15, each of which is associated with a respective room for measuring the temperature of the air in that room. The fluid temperature sensor 14 associated with any radiator 2 is connected to the output of the hydraulic valve 12 associated with the same radiator 2. For simplicity, hereinafter the measured temperature of the fluid leaving the generic radiator 2 will be called the fluid temperature. measured TURi. The measured air temperature of the generic room will be indicated with TAi. Figure 1 illustrates three radiators 2 for as many rooms, three respective electronic valves 11, three respective fluid temperature sensors 14 to obtain three measured fluid temperatures TURI, TUR2, TUR3, and three respective ambient temperature sensors to obtain three d air measured TAI, TA2, TA3. The heating system 1 comprises a further fluid temperature sensor 16 arranged on the main branch 6 of the delivery portion 4 of the hydronic circuit, preferably between the output 3a of the heat generator 3 and the pump 10, to measure the delivery temperature .

According to the invention, the heating system 1 comprises a control unit 17, i.e. a central control unit, configured to control each electronic valve 11 in such a way that the latter modulates the opening of its own hydraulic valve 12 as a function of the temperature. of fluid measured TURi of the respective radiator 2 and of a reference ("set point") of the return temperature TRSET common to all the radiators 2, and therefore to all the electronic valves 11. In detail, the opening of each hydraulic valve 12 it is modulated in such a way that the temperature of the fluid leaving the respective radiator 2 converges to the return temperature reference TRSET. For example, the modulation of the opening of each hydraulic valve 12 is made on the basis of a comparison with hysteresis between the relative measured fluid temperature TURi and the return temperature reference TRSET.

The modulating control of the electronic valves 11 as a function of the measured fluid temperatures TURi described above causes the temperatures of the fluid leaving all the radiators 2 to converge to the same value, and in particular to the return temperature reference TRSET. Consequently, the temperatures of the fluid leaving the radiators 2 are kept at the lowest possible value, which will substantially coincide with the return temperature reference TRSET.

The control unit 17 is also configured to control each electronic valve 11 so that the latter completely closes its own hydraulic valve 12 when the measured air temperature TAi of the respective room is equal to, or greater than, a reference of TASETi room temperature associated with the respective room. The control unit 17 is configured to control each electronic valve 11 so as to reopen its own hydraulic valve 12 when the measured air temperature TAi of the respective room returns to be lower than the respective reference of ambient temperature TASETi. The opening entity of the hydraulic valve 12 is defined by the modulation as a function of the measured fluid temperature TURi described above.

The on / off control of the electronic valves 11 as a function of the measured air temperatures TAi described above is performed simultaneously with the control of the electronic valves 11 as a function of the measured fluid temperatures TURi. This helps to keep the temperatures of the fluid leaving the radiators 2 at a minimum value and allows to compensate for the excessive increase of the ambient temperature in some rooms. In fact, when the measured air temperature TAi of a certain room exceeds the respective ambient temperature reference TASETi in the absence of the on / off control of the electronic valves 11, the temperature of the fluid at the outlet of the radiator 2 of that room, and therefore the temperature of the fluid in the return portion 5 of the hydronic circuit would increase abruptly. By closing the hydraulic valve 12, the flow of fluid in the respective radiator 2 is canceled, thus reducing the thermal power supplied by the radiator 2 and preventing the sudden increase in temperature of the fluid from propagating in the return portion 5 of the hydronic circuit and polluting "modulating control of electronic valves 11.

The pump 10 has a variable flow rate and is constituted, for example, by a variable speed inverter pump of a known type. The control unit 17 is configured to control the pump 10 so as to vary its flow rate as a function of the opening / closing state and the extent of opening of the hydraulic valves 12 of all the electronic valves 11. The opening / closing state and the extent opening of a hydraulic valve 12 are determined according to the last command that the control unit 17 has given to the respective electronic valve 11.

The control unit 17 is configured to control the heat generator 3 as a function of the measured return temperature TDm and a return temperature reference TDSET, so that the delivery temperature converges to the delivery temperature reference TDSET.

The control unit 17 is also configured to decrease the response time of the heating system in the event that in one of the rooms there is an immediate and considerable demand for thermal energy. In particular, when the measured air temperature TAi of a certain room is lower, by a predetermined temperature margin, than the ambient temperature reference TASETi associated with that room, the control unit 17 controls the electronic valves il associated with the radiators 2 of all the other rooms to completely close the respective hydraulic valves 12. In this way, the entire flow rate of the pump 10 is temporarily dedicated to the radiator 2 of a room, which increases its thermal power supplied to meet the extraordinary demand for thermal energy of that local.

From what has been described above, it is clear that the heating system 1 actually implements a method for regulating the return temperature of the heating system and, at the same time, regulating the room temperature in one or more rooms heated by this heating system, which method is substantially based on the fact of associating, to each radiator 2, a respective electronic valve 11, and of controlling the electronic valves 11 as a function of the measurements of the temperatures of the fluid leaving the various radiators 2 and of the measurements of the temperatures from the air in the various rooms, according to the procedures already described.

Furthermore, according to the method of the invention, the return temperature reference TRSET and the delivery temperature reference TDSET are determined as a function of a predetermined value of thermal power supplied by the radiator 2, for example the nominal thermal power of the radiator. 2, by interpolating the performance curves of the radiator 2 and of the heat generator 3, in such a way as to maximize the performance of the electric generator.

Figure 2 illustrates the performance curves of the radiator 2 constituted, for example, by curves of the thermal power supplied by the radiator, indicated by PR, as the delivery temperature TD and the return temperature TR vary. Figure 3 illustrates the performance curves of the heat generator 3 consisting, for example, of COP curves as the delivery temperature TD and the return temperature TR vary. In both figures 2 and 3 the return temperature TR is represented on the abscissa axis and the curves are parameterized for some values of the flow temperature TD. As the flow temperature TD increases, the power curves PR rise (figure 2) and the COP curves fall (figure 3).

With reference to the example of figures 2 and 3, the predetermined value PRSET of thermal power required by the radiator 2 (figure 2) can be satisfied by several pairs of delivery and return temperatures, indicated with A, B and C in figures 2 and 3. The optimal temperature pair is the one that maximizes the efficiency of the heat generator 3. In the example shown in Figures 2 and 3, the optimal temperature pair is the pair B. Therefore, the temperatures of the temperature pair B are the return temperature reference TRSET and the delivery temperature reference TDSET that the control unit 17 uses to control the electronic valves 11 and the heat generator 3.

According to a further embodiment of the invention, which is not illustrated, which is used if there is only one room to be heated, the heating system 1 differs from the one illustrated in Figure 1 in that it comprises only one radiator 2, a single electronic valve 11, one fluid temperature sensor 14 and one room temperature sensor 15.

According to a further embodiment of the invention, not illustrated, one or more radiators 2 are associated with each room. In each of the rooms with several radiators 2, all the relative electronic valves 11 are controlled on / off according to the air temperature. measured TURi and the TASETi ambient temperature reference for the room in question.

According to a further embodiment of the invention, not illustrated, the electronic valves 11 are arranged in the delivery portion 4 of the hydronic circuit. In particular, the hydraulic valve 12 of each electronic valve 11 is arranged in a respective secondary branch 7 of the delivery portion 4, that is, in the secondary branch 7 connected to the inlet 2a of the respective radiator 2. More precisely, each electronic valve 11 has the own hydraulic valve 12 connected to the inlet 2b of a respective radiator 2. Furthermore, each fluid temperature sensor 14 is connected to the outlet 2b of the respective radiator 2.

Although the invention described above makes particular reference to a very precise example of embodiment, it is not to be considered limited to this example of embodiment, since all those variants, modifications or simplifications that would be evident to those skilled in the art, such as for example the arrangement of the fluid temperature sensors 14 between the output 2b of the respective radiators 2 and the respective electronic valves 11.

The main advantage of the method and of the system 1 described above is to keep the fluid leaving all the radiators 2 at the same temperature and therefore at the lowest possible temperature, thanks to the double control of the electronic valves 11, of the modulating type according to the Fluid temperatures measured TURi and of the on / off type according to the measured air temperature TAi, thus allowing to increase the efficiency of the heat generator 3. Furthermore, the possibility of choosing the flow and return temperature references in operation of the thermal power supplied by the radiator 2 and through an interpolation of the performance curves of the radiator and heat generator 3 such as to maximize the performance l the heat generator, allows to optimize the efficiency of the heat generator 3 and the heating system 1.

Claims (12)

CLAIMS 1. Method for regulating the return temperature of the fluid circulating in a heating system and the ambient temperature of at least one room heated by this heating system, which comprises at least one radiator (2) to heat said room and thermal generating means ( 3) to heat the fluid to be fed to the radiator (2); the method including: - associating, to the radiator (2), a respective electronic valve (11) comprising its own hydraulic valve (12) to regulate the flow rate of the fluid through the radiator (2); - measuring the temperature of the fluid leaving the radiator (2) by means of a respective fluid temperature sensor (14); - measure the air temperature in the room by means of a respective room temperature sensor (15); - command the electronic valve (11) to modulate the opening of the hydraulic valve (12) as a function of the measured temperature (TURi) of the fluid leaving the radiator (2) and of a return temperature reference (TRSET); And - command the electronic valve (11) to completely close the hydraulic valve (12) when the measured air temperature (TAi) is equal to, or greater than, an ambient temperature reference (TASETi). Method according to claim 1, wherein the electronic valve (11) is controlled to modulate the opening of its own hydraulic valve (12) in such a way that the temperature of the fluid leaving the radiator (2) converges to said reference return temperature (TRSET). Method according to claim 1 or 2, wherein the electronic valve (11) is commanded to open its own hydraulic valve (12) when the measured air temperature (TAi) is lower than said ambient temperature reference (TASETi) . Method according to any one of claims 1 to 3, and comprising: - determining said return temperature reference (TRSET) as a function of a value (PRSET) of thermal power supplied by the radiator (2), by interpolating the performance curves of the radiator (2) and of the heat generating means (3), in in such a way as to maximize the performance of the heat generating means (3). Method according to any one of claims 1 to 4, and comprising: - determine a flow temperature reference (TDSET) as a function of a thermal power value (PRSET) supplied by the radiator (2), by interpolating the performance curves of the radiator (2) and of the heat generator means (3), in in such a way as to maximize the performance of the heat generating means (3); - measuring the fluid delivery temperature by means of a further fluid temperature sensor (16); - controlling said thermal generator means (3) as a function of the measured delivery temperature (TDm) and of the delivery temperature reference (TDSET). Method according to claim 4 or 5, wherein said performance curves comprise curves of thermal power supplied by the radiator (2) as the delivery temperature (TD) and the return temperature (TR) of the fluid vary. Method according to any one of claims 4 to 6, wherein said performance curves comprise yield curves or COP of the thermal generator means (3) as the delivery temperature (TD) and the return temperature (TR) of the fluid. Method according to any one of claims 1 to 7, wherein said heating system (1) comprises a plurality of radiators (2) for heating several rooms and a respective electronic valve (11) is associated with each radiator (2); the temperature of the fluid leaving each radiator (2) being measured by means of a respective fluid temperature sensor (14); the air temperature in each room being measured by means of a respective ambient temperature sensor (15); said return temperature reference (TRSET) being unique for all radiators (2); each electronic valve (11) being controlled to modulate the opening of its own hydraulic valve (12) as a function of the measured temperature (TURi) of the fluid leaving the respective radiator (2) and of the return temperature reference (TRSET); each electronic valve (11) being commanded to completely close its own hydraulic valve (12) when the measured air temperature (TAi) of the relevant room is equal to, or greater than, an ambient temperature reference (TASETi) associated with the room . Method according to claim 8, and comprising: - when the measured air temperature (TAi) of a certain room is lower, by a predetermined temperature margin, than the ambient temperature reference (TASETi) associated with said certain room, command the electronic valves (11) associated with the radiators (2) of all the other rooms to completely close the respective hydraulic valves (12). 10. Heating system comprising at least one radiator (2) to heat at least one room, thermal generator means (3) to heat the fluid to be fed to the radiator (2), a fluid transport circuit (4, 5), which comprises a return portion (5) for conveying the cooled fluid from the radiator (2) to the thermal generating means (3), at least one electronic valve (11), which comprises a hydraulic valve (12) to regulate the flow rate of the fluid through the radiator (2), at least one fluid temperature sensor (14) disposed in said return portion (5) for measuring the temperature of the fluid leaving the radiator (2), at least one ambient temperature sensor (15) for measure the air temperature in the room, and control means (17) configured to control the electronic valve (11) in such a way as to modulate the opening of the hydraulic valve (12) as a function of the measured temperature (TURi) of the fluid in outlet from the radiator (2) and a return temperature reference (TRSET) and in such a way as to completely close the hydraulic valve (12) when the measured air temperature (TAi) is equal to, or greater than, an ambient temperature reference (TASETi). 11. Plant according to claim 10, and comprising a plurality of radiators (2) for heating several rooms, a plurality of electronic valves (11), each of which is associated with a respective radiator (2) to regulate the flow rate of the fluid through the radiator (2), a plurality of fluid temperature sensors (14), each of which is arranged in a respective secondary branch (9) of said return portion (5) connected to the outlet (2b) of a respective radiator (2) for measuring the temperature of the fluid leaving the radiator (2), and a plurality of ambient temperature sensors (15), each of which is associated with a respective room for measuring the temperature of the air in the room; said return temperature reference (TRSET) being unique for all radiators (2); said control means (17) being configured to control each electronic valve (11) in such a way as to modulate the opening of its own hydraulic valve (12) as a function of the measured temperature (TURi) of the fluid leaving the respective radiator (2) and the return temperature reference (TRSET) and in such a way as to completely close its hydraulic valve (12) when the measured air temperature (TAi) of the relevant room is equal to, or greater than, an ambient temperature reference (TASETi) associated with the room. System according to claim 10 or 11, wherein said fluid transport circuit (4, 5) comprises a delivery portion (4) for conveying the hot fluid from said heat generating means (3) to said at least one radiator ( 2) and a variable flow pump (10) arranged in said delivery portion (4), at the outlet (3a) of the heat generating means (3); said control means (17) being configured to control the pump (10) so as to vary its flow rate as a function of the opening / closing state and the extent of opening of the hydraulic valves (12) of all the electronic valves (11).