Hydronic/biphasic radiator with reduced thermal inertia and low environmental impact

Abstract

A radiator with reduced thermal inertia, based on the principle of phase changing, using a non-toxic, non-flammable fluid with reduced environmental impact. The radiator is provided by means of vertical pipes which engage a collector containing a pipe bundle-type exchanger with smooth or finned pipes, internally crossed by the thermo-vector fluid of the system, and which heat the intermediate vector fluid, bringing it to the biphasic state. The vector fluid evaporates, rising up the vertical pipes, flowing through the channels obtained in the extruded profiles of the vertical pipes themselves. The fluid re-descends, condensing on the walls, returning into contact with the hot pipes of the exchanger in order to re-evaporate and rise back up the vertical pipes. The film of condensed liquid provides the required heat exchange. The terminal is further equipped with mechanical parts which allow the inserting of temperature sensors for possible monitoring and control of consumption and system operation and control thereof, by means of on-board electronic control devices (electric valves) and remote devices suitably operating in radio-frequency.

Claims

1. A radiator of the thermosiphon type comprising a radiating body made of metal which comprises: a tubular-shaped collector defining a longitudinal axis and situated in the bottom part of the radiator, and adapted to contain an intermediate vector fluid functioning in the biphasic state, a heat exchanger placed within the collector, consisting of one or more pipes which are parallel to the longitudinal axis of the collector and within which pipes a thermo-vector fluid from an external heating plant can flow, at least one pipe which is orthogonal to the longitudinal axis of the collector, containing therein one or more channels connected to the collector and communicating with the same, an adjustment system integrated within the radiator itself, in order to adjust the temperature of the intermediate vector fluid as a function of the thermal requirements of the room, a temperature sensor inside the collector for measuring the temperature of the intermediate vector fluid in contact with the heat exchanger.

2. The radiator according to claim 1, wherein the radiating body is made of aluminum.

3. The radiator according to claim 1, wherein the intermediate vector fluid can evaporate, under conditions of nucleate boiling, on contact with a surface of the heat exchanger.

4. The radiator according to claim 3, wherein the surface of the pipes which constitute the heat exchanger, has micro-fins in order to favour the nucleation phenomena.

5. The radiator according to claim 1, wherein the thermo-vector fluid is water.

6. The radiator according to claim 1, where the temperature sensor is inserted in a pipe parallel to a pipe of the heat exchanger.

7. The radiator according to claim 6, comprising a valve adapted to modify the thermo-vector fluid flow at the heat exchanger inlet.

8. The radiator according to claim 7, comprising a feedback-type control system in order to maintain the conditions of evaporation in the state of nucleate boiling.

9. Use of the radiator according to claim 1, for replacing a traditional radiator and using the same heating and thermo-vector fluid circulation system in order to supply the heat exchanger.

10. The method for adjusting the thermal conditions of a room heated by a radiator according to claim 1, wherein the adjustment of the temperature takes place by adjusting the thermo-vector fluid flow at the heat exchanger inlet by means of a valve.

11. The method according to claim 10, wherein the valve which controls the thermo-vector fluid flow can be remotely controlled by radio-frequency.

12. The method for controlling the operation of a radiator according to claim 11, wherein the nucleate boiling regime is maintained by adjusting the temperature of the intermediate vector fluid on contact with a wall of the heat exchanger by means of a variation of the thermo-vector fluid flow at the heat exchanger inlet.

13. The method for controlling the operation of a radiator according to claim 12, wherein, during the transition period between the moment in which the intermediate vector fluid is at room temperature and the moment in which it reaches the desired temperature, the heating of the intermediate vector fluid is electronically controlled by using a suitable operating sequence which maintains the temperature of said fluid below the critical temperature at which the chemical degradation of the fluid begins.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further features and advantages of the invention will become clearer in view of the detailed description of a preferred but not exclusive embodiment of a hydronic biphasic radiator, which uses the hot water from an external heating plant as thermo-vector fluid, shown by way of non-limiting example with the aid of the accompanying drawings in which:

(2) FIG. 1 shows a front view of the thermosiphon according to the present invention,

(3) FIG. 2 shows a cross-section, which also shows the principle of operation of the biphasic thermosiphon,

(4) FIG. 3 shows a longitudinal section which shows the hot water (thermo-vector fluid) inlet and a bulb in a central position, with respect to the heat exchanger pipes, with a temperature sensor,

(5) FIG. 4 is another representation of the collector with the heat exchanger, and a sealing flange,

(6) FIG. 5 shows a cross-section with, at the centre of the collector, a heat exchanger provided as a single pipe,

(7) FIG. 6 shows various perspective views of the radiator and how the thermosiphon is assembled on the wall of the room to be heated.

(8) FIG. 7 shows a detail of a vertical pipe,

(9) FIG. 8 shows a detail of the assembly of the crosspiece which closes the thermosiphon in the upper part,

(10) FIG. 9 shows, as in FIG. 8, the assembly of the crosspiece and the closing of the vertical pipes,

(11) FIG. 10 shows the engagement of the vertical pipes in the collector,

(12) FIG. 11 shows the position of the sensor-holding bulb in the case of a heat exchanger with four pipes,

(13) FIG. 12 shows the position of the sensor-holding bulb in the case that the heat exchanger consists of only one pipe.

(14) FIG. 13 shows the transient phase of the intermediate vector fluid heating.

(15) The reference numbers in the figures indicate the same elements or components.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

(16) A hydronic biphasic thermosiphon 1 according to the invention is shown in FIG. 1, where numeral 2 indicates the vertical pipes containing the channels along the walls of which the film of moisture forms during operation, and numeral 3 indicates the collector containing the intermediate vector fluid which, during operation, in contact with heat exchanger 6 which is found within the collector, evaporating, rises up the aforementioned channels before condensing along the walls of the same (FIG. 2).

(17) The pipe bundle-type heat exchanger, as shown in FIGS. 2 and 3 by a group of four pipes 6, is fixed to collector 3 and terminates with two sealing flanges 16, one at the inlet and the other at the outlet of the thermo-vector fluid, each of which rests on the corresponding abutment of collector 3 and is sealingly welded or brazed 14 onto the latter (FIG. 3). Each flange 16 has one or more holes (FIG. 4) for housing and sealingly fixing the pipes 6 within which the water or another thermo-vector fluid at temperature from the plant flows. The heat exchange pipes 6 can be made of aluminium, copper or steel alloy, smooth or finned or micro-finned (FIG. 5). The finning 17 allows to reduce the number of pipes or reduce the overall dimensions of the radiator inasmuch as they increase the number of triggers and nucleation of the bubbles during the biphasic heat exchange with the intermediate vector fluid. The increasing of the number of bubbles guarantees the field of existence of the heat exchange in nucleate boiling which has the highest heat exchange coefficient with the intermediate vector fluid.

(18) The fixing of the smooth pipes generally takes place by brazing or expanding. The finned pipes, on the other hand, are fixed at one end by expanding or brazing, and at the other by means of a double expanding element with the aid of an additional fixing ferrule which allows the passing of the finning in the installation phase.

(19) In order to prevent excessive load losses at the radiator inlet and outlet, two conical reducers 4 are used which are suitably dimensioned and engaged on collector 3. The two conical reductions 4 which protrude from collector 3 are shown by way of example, the concept is that there are two devices at the collector inlet and outlet, in particular they can be conical connections, which allow to limit load losses by guiding the water flow. In fact, the water passes through a standard connection which is usually of ½ gas size and must then enter the four pipes of the exchanger.

(20) The conical reducer has the task of guiding the fluid threads so as to limit the load losses and therefore reduce the electrical pumping power, which leads to energy saving, as by limiting the load losses, the counter-pressure is limited and the pump must overcome a smaller pressure in order to pump the fluid.

(21) The vertical pipes 2 are characterized by profiles, e.g. finnings, suitable fluid dynamic geometries, such as to favour a better compromise between heat exchange towards the environment and terminal weight. In particular, a finning 19 on the rear part facing the wall (FIGS. 6, 7) contributes to increasing the heat exchange by convection with the air contained between the radiator and the wall, also increasing the rising speed thereof and the chimney effect. The pitch of the fins must allow as much as possible the return of fresh air from the adjacent areas so as to accelerate as much as possible the fluid which moves due to the density gradients, increasing the heat exchange coefficient by natural convection.

(22) By developing the surface on the rear side 19, it is possible to provide a smaller number of pipes, reducing the external dimensions of the radiator and limiting the weight and therefore the inertia of the radiator. At the front, vertical pipe 2 has stubby fins 20, in order to increase the efficiency thereof, of the smallest height possible compatibly with the engagement dimensions of vertical pipe 2 with collector 3 (FIG. 10).

(23) The number of vertical pipes is optimized based on the power to be exchanged as a function of the water inlet temperature.

(24) The small thickness, as can be noted from FIG. 6, which is less or at least equal to that of traditional furnishing thermosiphons, guarantees architectural integration. Vertical pipe 2 has therein channels 10 for passing the vapour and the film of condensate. The channels are dimensioned with the valid ratios for the biphasic heat exchange and have a greatly reduced section thanks to the extremely low surface tension of the fluid.

(25) The minimum passage section as a function of the low surface tension and viscosity of the fluid are such as to allow a pipe to be provided with a smaller thickness than traditional furnishing radiators. Furthermore, the technology of the biphasic radiator, not necessitating a collector 3 also on the upper part, allows to reduce the weight of the entire radiator which has only one collector on the lower part and an aesthetic and structural crosspiece 5 on the upper part. The crosspiece (FIGS. 8, 9) can be screwed with self-threading screws 21 on specific hollow slots obtained directly on the extruded profile of the vertical pipe. The vertical pipes are closed on the upper part with aluminium plugs 22 obtained by fine blanking, so as to guarantee the narrow tolerances necessary for providing the brazed joint, and equipped with specific interlocking teeth for housing on the corresponding hollow one on the vertical pipe obtained by mechanical process.

(26) In FIGS. 3 and 4, there is shown a heat exchanger formed by four pipes 6 which are parallel to the longitudinal axis of collector 3 which contains them.

(27) In FIG. 5, there is depicted a variation with a heat exchanger 6 consisting of a single central pipe, with respect to collector 3, which can be equipped with micro-finning 17. The collector is provided starting from an extruded profile with a tubular profile at the centre which is supported and connected to the collector by means of one or two fins 18 in such a configuration as to allow in any case a sufficient efflux of intermediate vector fluid which wets and exchanges heat with the surface of central pipe 6. In this variation, the heat exchanger is the central pipe 6 and is already integrated in the starting extruded profile. The central pipe 6 may be longitudinally finned, the fins 17 are directly obtained by extrusion. This configuration facilitates the production of the radiator, using the brazing of the two head flanges 7 as fixing technology. The mechanical processes are also relatively simple: they involve suitably working the front end of the collector, so as to remove the fins which support the central pipe and the fins of the central pipe itself in order to create a shoulder which allows the housing of two flanges which will be brazed onto the collector. The two flanges guarantee the sealing of the system and contribute towards supporting the central pipe.

(28) In FIG. 4 a bulb, in this case centrally arranged, holds a temperature sensor 8 which may be in contact with the heat exchanger pipes 6 or in direct contact with the intermediate vector fluid. The possibility to insert temperature sensors within the collector, in contact with the exchanger pipes or in direct contact with the fluid, gives the possibility to integrate the system terminal with advanced devices for controlling and monitoring energy consumption and comfort for complete home automation integration and reduction of energy consumption.

(29) For this purpose, the collector may be equipped with one or more bulbs, not shown in the drawings, i.e. cylindrical containers adapted to house the temperature sensors for controlling the heat exchange process between intermediate vector fluid and the thermo-vector fluid from the heating system, so as to maintain the system in better heat exchange conditions (nucleate boiling) without exceeding the critical thermal flow conditions of the fluid.

(30) Furthermore, the hydronic radiator can be integrated, if necessary, with control and adjustment devices directly connected thereto, such as systems comprising a flow adjustment valve or electric valve, specifically connected to the collector inlet, giving the possibility of modulating the inlet flow of the thermo-vector fluid from the heating plant, therefore modulating the thermal power conferred to the radiator and supplied therefrom to the environment.

(31) Eventually, the electric valve may also be remotely controlled in radio-frequency, by means of an electronic control console, providing an integrated system capable of improving the global efficiency of the heating process of residential and commercial environments.

(32) In order to implement the aforementioned control system, it is possible to equip the radiator with a cylindrical housing, part of the exchanger, in direct contact with the intermediate vector fluid in the biphasic state and within which one or more temperature sensors may be inserted in order to detect the temperature of the intermediate vector fluid. The signal from these sensors can be processed by the possible control electronics as a temperature feedback signal and as a parameter which is correlatable with the operating conditions of the radiator and the plant (plant monitoring). The intermediate vector fluid temperature, compared with the room temperature read by an environment probe or a probe placed on the control electronics onboard the radiator, can provide useful information for adjusting the thermo-vector fluid flow entering the radiator, allowing to modulate the flow and the power supplied by the radiator as a function of the real requirements and therefore the required energy consumptions.

(33) The same probe eventually installed can at the same time supply a feedback to the possible control electronics installed on the radiator, in order to implement the desired control logics of the biphasic heat exchange process between the heat exchange and the biphasic fluid, in order to optimise the heat exchange coefficient with the biphasic fluid remaining in the heat exchange range for nucleate boiling.

(34) By keeping the instantaneous values of the intermediate vector fluid temperature under control, the condition of heat exchange between intermediate vector fluid in the biphasic state and heat exchanger is maintained, in nucleate boiling regime, maximising its heat exchange coefficient and preventing the fluid from working in critical flow conditions.

(35) It has been discovered that using intermediate vector fluids particularly from the hydrofluoroether family, the critical flow is a function of the room temperature (coinciding with the temperature of the fluid before it is heated by the thermal source, i.e. the thermo-vector fluid). The critical phase of operation occurs when the radiator is at room temperature (therefore “cold”) and is fed by the thermo-vector fluid passing in the heat exchanger. In particular, in the most severe case in which, starting from the room temperature, the radiator is fed at the maximum power, the external temperature of the heat exchanger takes on rather high peak temperature values in the first instants of operation and for a good period of the transient, before reaching the regime. The hydrofluoroethers are characterised by a maximum usage temperature, critical temperature, above which the chemical degradation of the fluid takes place. If it is found that the radiator may have this criticality, a control electronics adjustment algorithm known as “Soft Start” may be adopted which is capable of maintaining the intermediate vector fluid temperature at the heat exchanger surface below the critical value of chemical degradation. The electronics modulate/choke the thermal power supplied by the thermo-vector fluid to the intermediate vector fluid, so as to maintain/control the intermediate vector fluid temperature below the critical temperature. In FIG. 13, an illustrative diagram is shown of the rising choked ramp during the heating transient. In the first 30 seconds, the radiator supplies full power in order to preheat the fluid and cause it to largely evaporate. It then supplies between 50 and 65% for a total time “L” (which in the first choking comprises 100% for thirty seconds plus 50-65% for the remaining L-30 sec). The other incremental power stretches then follow which last the same time L. The duration of each interval depends on the room temperature at which the radiator is found when the feeding/heating step begins (starting from cold). The lower the room temperature, the greater the duration L must be. It is possible to calibrate the duration of each interval based on various intervals of room temperature. The system with incremental powers and durations L has the function of gradually causing the intermediate vector fluid to evaporate, keeping the boiling regime in the nucleate boiling phase by allowing the vapour to reach the top of the vertical pipes and giving the liquid film time to re-descend, maintaining the intermediate vector fluid temperature at the heat exchanger surface below the temperature of chemical degradation. Based on the complexity of the regulator and the calculation resources, it is possible to vary both the duration L and the corresponding choked power, by creating more steps than those represented (in the direction of a continuous adjustment of the soft start), all of this as a function of the temperature detected by the sensor placed within the radiator at the heat exchanger surface, so as to maintain the fluid temperature below the critical value. When the temperature at the thermo-vector fluid/intermediate vector fluid interface rises, if it exceeds the limit, the electronic control will immediately provide for decreasing the supplied instantaneous power and increasing the corresponding duration L. The control of the power introduced into the intermediate thermo-vector fluid takes place by varying the thermo-vector fluid flow by actuating a special electric valve with an opening and closing control. The soft start has a limited total duration (Ltot) and is interrupted when the radiator enters the adjusting mode of the room temperature (i.e. within the band of room temperature adjustment). The soft start has the advantage, by keeping the boiling in the nucleated phase and limiting the temperature peak at the fluid/thermal source interface, of allowing the use of thermal sources with high thermal flows per unit area. The use of an intermediate vector fluid in the biphasic state with low surface tension and viscosity allows to reduce the efflux channels, the internal volume of the radiator and consequently the weight of the entire structure, to a minimum. In particular, this results in a greatly reduced thickness of the pipe or vertical pipes with a perfect integration on an architectural level with more modern style interiors.

(36) The use of biphasic heat exchange technology with finned pipes in the exchanger, combined with optimisation of the finning on the rear and front part of the radiator, leads to optimising the surface heat exchange wherein the entire surface basically exchanges heat at the same temperature. The optimisation of the heat exchange in conjunction with the weight reduction of the radiating body and the limited content of the intermediate vector fluid, as a first consequence leads to a consistent reduction of the time constant, limiting the transient times, satisfying the requirement of energy saving and meeting the requirements of the lifestyle of contemporary society.

(37) From the perspective of room comfort, the biphasic hydronic radiator, due to the heat exchange in boiling regime, favours the radiating heat exchange, by maximising the radiating efficiency of the surface, thanks to the uniformity of the thermal map of the surface. Finally, due to the vacuum level, the possibility of using various fluids with different boiling points at atmospheric pressure is provided, but especially the possibility to always assure the evaporation and therefore the biphasic heat exchange with even surface distribution of temperature on the radiator also for plant water inlet temperatures which are characteristic of a heat pump or condensation-type boiler.