GB1585557A

GB1585557A - Heating system

Info

Publication number: GB1585557A
Application number: GB24883/77A
Authority: GB
Original assignee: VE MA ELETTROPOMPE SpA
Current assignee: VE MA ELETTROPOMPE SpA
Priority date: 1976-06-15
Filing date: 1977-06-14
Publication date: 1981-03-04
Also published as: FR2355252A1; DE2726497A1; IT1192161B

Description

(54) HEATING SYSTEM (71) We, VE-MA ELETTROPOMPE S.p.A., a Joint Stock Company, organized and existing under the laws of Italy, of Via Marco Polo, 26-Mestrino (Province of Padova) Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a heating system particularly but not exclusively of the kind which uses solar collectors.

As is known, systems of this type absorb the heat of solar radiation and transfer this heat, in tube nests of various shapes and dimensions, into a fluid which, in turn.

exchanges the heat with a heat receiving medium such as water in a specially designed boiler-accumulator.

Thus, there occur two exchange steps where the features of the heat exchanger play a role. the other variables on which the output and the regulating system depend being the temperature of the exchange fluid and the temperature, flow rate, and tapping rate of the heat receiving water.

As may be seen, the predictable parameters and the unpredictable ones are numerous. and the regulation and the consequent problem of choice of the best operative condition is not capable of simple solution. and any deviation from an optimal condition wastes or. more accurately. does not utilize a certain amount of energy. which is therefore lost.

In the systems currently employed. there is generally included an exchange fluid circulating pump. and the latter is usually stopped by a thermostatic control as soon as the temperature of the heat receiving water reaches a preset temperature maximum or rises above the temperature of the exchange fluid.

This control method affords on the one hand extreme simplicity of construction but utilizes only part of the energy that can be derived from a solar collector, the thermal behaviour of which is tied to the changeable weather situations.

According to the present invention there is provided a heating system comprising a heat exchanging fluid circuit, a thermal source adapted to heat heat exchanging fluid flowing through said heat exchanging fluid circuit, a heat receiving fluid circuit arranged for flow of heat receiving fluid which receives heat from said heat exchanging fluid, and temperature sensors arranged to monitor the temperatures of said heat exchanging and heat receiving fluids at appropriate points, in combination with a comparator unit of the monitored temperatures, the output of said comparator unit being arranged to vary the heat exchanging fluid flow rate to maintain a required temperature differential between said heat exchanging and said heat receiving fluids.

By this invention it is possible to provide a heating system which improves the heat extraction from a thermal source, such as a solar collector.

The present invention may also provide a heating system which adjusts itself to a thermal source of variable heat delivery.

A device can thus be provided which does not require an operator, and which may be of low cost.

An embodiment of the present invention will now be described in detail, by way of example. with reference to the accompanying drawing wherein: Figure 1 is an exemplary schematic representation of a solar collector plant; and Figure 2 is a graph of the operating temperatures of the heat receiving water and exchange fluid.

Referring to Figure 1, a thermal source 1 e.g. a solar collector, is included in a closed circuit formed by a pipe 2 and exchanger 3 accomodated inside a thermal accumulator or boiler 4, and by a variable flow circulating pump 5. Also included is a surge tank 6. The relative positions of the components are not-critical but only conditioned by the fact that said solar collector 1 will be exposed to the sun radiation and that said exchanger 3 will be always located within a boiler 4, knownperse. Said boiler 4 is fed with a heat receiving fluid, e.g. water, through a pipe 7 equipped with a valve 8, the pipe 7 being connected to the water supply, Hot water is tapped from an upper tube 9.

The embodiment has a data processing and comparator unit 10, substantially consisting of a comparator 11, error amplifier 14, manual regulator 15, and power amplifier 16. The comparator 11 is adapted to compare the signals from a first thermostatic probe or sensor 12 located in the tube 2, at the outlet from said solar collector 1, and from a second thermostatic probe or sensor 13 for detecting the temperature of the water within said boiler 4.

Generally, such thermostatic probes represent a suitable means for generating signals which are proportional to the temperatures of the exchange fluid and heat receiving fluid.

The output signal from the comparator 11 is inputted to the error amplifier 14, equipped with the manual regulator 15. and hence to the power amplifier 16 which is fed from the mains and sends modulated power to said variable flow pump 5.

Such a device operates as a temperature follower whereby, once the temperature differential between the exchange fluid - thermostatic probe 12 - and the heat receiving fluid - thermostatic probe 13 - has been set such as to afford an optimal thermal exchange in the boiler 4, the differential is maintained for any system condition of the solar collector or thermal condition of the boiler tank. In other words. as may be observed in Figure 2. the difference between the two temperatures - shown by dotted lines in the case of the exchange fluid and in full lines in the case of the heat receiving water respectively - is kept virtually constant.

That action is obtained by varying the delivery rate. e.g. by varying the rpm of the circulating pump under control by the control system 10.

Depending on the particular variation of conditions. the system will behave as follows: I) The solar collector receives less heat; the probe 12 detects a temperature drop. the electric pump receives through the amp lifier 16. a command to reduce the flow rate such that the thermal exchange in the solar collector and boiler is varied so as to tend to bring the exchange fluid tempera ture back to the previous value. If that exchange produces in the boiler a decreased temperature of the heat receiv ing water. then the system. through the probe 13, adjusts the probe 12 such as to maintain the temperature differential constant.

2) The solar collector receives more heat; the reverse response of Case I occurs.

3) The temperature of service water in the boiler tank drops; the same response as Case 2 occurs.

4) The temperature of service water in the boiler tank raises; the same response as Case I occurs.

It should be noted, moreover, that advantageously, though in a manner knownperse, the variable flow pump may be designed to have an electric energy absorption (power input) which is proportional to the output power and, therefore, to the delivery rate, thus affording the advantage that to weak thermal exchanges the energy consumption is low so that maximum economy and high overall efficiency are ensured by the system.

Other embodiments are possible, involving, for example, variations in the probe locations and of the signal they produce.

Obviously. the materials and the dimensions of the system may be varied to meet particular requirements.

WHAT WE CLAIM IS: 1. A heating system comprising a heat exchanging fluid circuit, a thermal source adapted to heat heat exchanging fluid flowing through said heat exchanging fluid circuit, a heat receiving fluid circuit arranged for flow of heat receiving fluid which receives heat from said heat exchanging fluid. and temperature sensors arranged to monitor the temperatures of said heat exchanging and heat receiving fluids at appropriate points. in combination with a comparator unit of the monitored temperatures, the output of said comparator unit being arranged to vary the heat exchanging fluid flow rate to maintain a required temperature differential between said heat exchanging and said heat receiving fluids.

2. A heating system according to claim I wherein said heat exchanging fluid circuit includes a variable flow circulating pump controlled by the output of said comparator unit.

3. A heating system according to claim 2.

wherein said variable flow circulating pump is arranged to operate so that its electrical power input is proportional to its mechanical power output.

4. A heating system according to either one of the preceding claims wherein said comparator unit comprises a comparator and in cascade connection therewith a manually programmable error amplifier and a power amplifier.

5. A heating system according to any one of the preceding claims wherein said heat receiving fluid circuit includes an accumulator in which the exchange of heat

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

pump 5. Also included is a surge tank 6. The relative positions of the components are not-critical but only conditioned by the fact that said solar collector 1 will be exposed to the sun radiation and that said exchanger 3 will be always located within a boiler 4, knownperse. Said boiler 4 is fed with a heat receiving fluid, e.g. water, through a pipe 7 equipped with a valve 8, the pipe 7 being connected to the water supply, Hot water is tapped from an upper tube 9.

The embodiment has a data processing and comparator unit 10, substantially consisting of a comparator 11, error amplifier 14, manual regulator 15, and power amplifier 16. The comparator 11 is adapted to compare the signals from a first thermostatic probe or sensor 12 located in the tube 2, at the outlet from said solar collector 1, and from a second thermostatic probe or sensor 13 for detecting the temperature of the water within said boiler 4.

Generally, such thermostatic probes represent a suitable means for generating signals which are proportional to the temperatures of the exchange fluid and heat receiving fluid.

The output signal from the comparator 11 is inputted to the error amplifier 14, equipped with the manual regulator 15. and hence to the power amplifier 16 which is fed from the mains and sends modulated power to said variable flow pump 5.

Such a device operates as a temperature follower whereby, once the temperature differential between the exchange fluid - thermostatic probe 12 - and the heat receiving fluid - thermostatic probe 13 - has been set such as to afford an optimal thermal exchange in the boiler 4, the differential is maintained for any system condition of the solar collector or thermal condition of the boiler tank. In other words. as may be observed in Figure 2. the difference between the two temperatures - shown by dotted lines in the case of the exchange fluid and in full lines in the case of the heat receiving water respectively - is kept virtually constant.

That action is obtained by varying the delivery rate. e.g. by varying the rpm of the circulating pump under control by the control system 10.

Depending on the particular variation of conditions. the system will behave as follows: I) The solar collector receives less heat; the probe 12 detects a temperature drop. the electric pump receives through the amp lifier 16. a command to reduce the flow rate such that the thermal exchange in the solar collector and boiler is varied so as to tend to bring the exchange fluid tempera ture back to the previous value. If that exchange produces in the boiler a decreased temperature of the heat receiv ing water. then the system. through the probe 13, adjusts the probe 12 such as to maintain the temperature differential constant.

2) The solar collector receives more heat; the reverse response of Case I occurs.

3) The temperature of service water in the boiler tank drops; the same response as Case 2 occurs.

4) The temperature of service water in the boiler tank raises; the same response as Case I occurs.

It should be noted, moreover, that advantageously, though in a manner knownperse, the variable flow pump may be designed to have an electric energy absorption (power input) which is proportional to the output power and, therefore, to the delivery rate, thus affording the advantage that to weak thermal exchanges the energy consumption is low so that maximum economy and high overall efficiency are ensured by the system.

Other embodiments are possible, involving, for example, variations in the probe locations and of the signal they produce.

Obviously. the materials and the dimensions of the system may be varied to meet particular requirements.

WHAT WE CLAIM IS: 1. A heating system comprising a heat exchanging fluid circuit, a thermal source adapted to heat heat exchanging fluid flowing through said heat exchanging fluid circuit, a heat receiving fluid circuit arranged for flow of heat receiving fluid which receives heat from said heat exchanging fluid. and temperature sensors arranged to monitor the temperatures of said heat exchanging and heat receiving fluids at appropriate points. in combination with a comparator unit of the monitored temperatures, the output of said comparator unit being arranged to vary the heat exchanging fluid flow rate to maintain a required temperature differential between said heat exchanging and said heat receiving fluids.
2. A heating system according to claim I wherein said heat exchanging fluid circuit includes a variable flow circulating pump controlled by the output of said comparator unit.
3. A heating system according to claim 2.

wherein said variable flow circulating pump is arranged to operate so that its electrical power input is proportional to its mechanical power output.
4. A heating system according to either one of the preceding claims wherein said comparator unit comprises a comparator and in cascade connection therewith a manually programmable error amplifier and a power amplifier.
5. A heating system according to any one of the preceding claims wherein said heat receiving fluid circuit includes an accumulator in which the exchange of heat

between said heat exchanging and said heat receiving fluid occurs and wherein said temperature sensors are arranged at the point where said heat exchanging fluid leaves said thermal source and at the point where the exchange of heat between said heat exchanging and said heat receiving fluid takes place within said accumulator, respectively.
6. A heating system according to any one of the preceding claims wherein said thermal source is a solar collector.
7. A heating system substantially as herein described with reference to and as illustrated in the accompanying drawings.

s T T TTO X T r T T T n t) n