ES2677269B1 - Two-phase thermal transmission system - Google Patents

Description

DESCRIPTION

THREE-PHASE THERMAL TRANSMISSION SYSTEM

TECHNICAL SECTOR

This invention is framed within thermal transmission systems by means of heat-dislodged fluids separated through a network of conduits, for their use, which includes industries such as thermo-solar, cooling and / or heating of motors and / or elements that require thermal transmission beyond the local transmission as well as air conditioning, heating, hot water generation and / or water vapor.

BACKGROUND OF THE INVENTION

The strong growth and energy demand of the last decades together with the limitation of resources, its continuous increase in price and at the same time the incorporation of relatively new concepts such as ecological footprint and the overwinter effect, have been developing the thermal transmission systems every time in a step beyond the frontier of efficiency, effectiveness and energy sustainability.

There have been major changes in terms of improvement of insulators, materials, fluids, accessories and design, although there have been few changes in thermal transfer systems, which are mainly based on two concepts. On the one hand, the certification bodies and the applicable legislation in thermal installations comprise a very specific area of operation in them, in them their transmission systems. On the other hand, the developers of the thermal installation product invest in the evolution of their products in accordance with the applicable legislation, leaving the transfer system and its evolution in an unalterable second plane, although a whole new range of products can be developed from a development of it.

The current thermal transmission systems are divided mainly into two groups, those whose thermal exchange cycle is developed with a heat transfer fluid in a single state (monofasics), generally as liquids and those in which its heat transfer fluid is presented in two states (biphasic), usually as liquid-vapor.

The biphasic systems, basically, currently consist of two systems, those usually based on boilers or exchangers of continuous evaporation of demineralized water and those that compress-decompress a vapor-liquid by means of a motor (compressor). The former, as explained above, have boilers or exchangers for the continuous evaporation of demineralized water at 100 ° C together with a steam superheater whose final temperature is adapted to the needs, with pressures always higher than the atmospheric one, transferring by high pressure and temperature the steam / gas to the points of use-exchange and later discarded to the environment or is returned to the point of generation, in a semi-closed or open cycle depending on the installation, transferring mechanical and mechanical energy in some cases throughout the process . In these systems lies the disadvantage of being forced to maintain high temperatures, above 120 ° C to avoid saturation in the circuit, although there is no demand or this is low, being very inefficient in this state because the various losses tend to stay linear by hour of system operation. The second group, those that compress-decompress a vapor, generally use heat-bearing fluids called refrigerant fluids, gaseous at room temperature and pressure, in a closed hermetic circuit, where, under the mechanical action of a compressor element, they are compressed and liquefied, yielding heat to reference system 1, and subsequently conducted and expanded again by absorbing heat from reference system 2, its range of primary exchange temperatures are limited to approximate ranges of -40 ° C to 60 ° C, it consumes great energy during the process due to the great mechanical work of the compressor, they also have thermal losses due to friction in the compressor and those due to the conversion of the electrical energy into mechanics by its motor.

The other group, the most common and most widely used are those systems that work with a fluid coolant or fluid mixture in liquid state and pressures above atmospheric. They are generally based on the semi-closed circulation of additivated demineralized water, which, being cooled or heated to minimum and maximum temperatures between 3 ° C and 90 ° C in a cooling device or boiler respectively, is circulated, yielding therefore calonfica energy to all those points of use-exchange. This system has the disadvantages of requiring elements of permanent acceleration of the fluid to flow to points of use, such as circulating pumps, and since the kinematic viscosity of the liquid water is relatively high, large losses occur in the forced circulation of the fluid associated with the mechanical work of the circulating pump, in addition to a large dimensioning of the conduits in relation to that same phenomenon, although it also requires in the installation of elements that allow the expansion of incompressible character of the liquids according to the temperature variations thereof. In some cases, gravity and changes in the density of the liquid according to its temperature (thermosyphon effect) are also used, although they do not require a mechanical fluid accelerator element, the kinematic viscosity of the liquid added to the small variation of the density of the liquid. The same for each degree of temperature, makes this system a bad alternative when efficiency and effectiveness are requirements to be taken into account, since they require high gradients of emitter-receiver temperature and therefore, high thermal losses in the emitter.

As can be seen a single-phase (liquid) thermal transmission system, although conceptually its theoretical operation is simple, its installation and continuous service is not necessary because it requires various elements that reduce its efficiency, effectiveness, reliability, durability and intrinsic safety.

Therefore, it is the object of the present invention to develop a thermal transmission system that overcomes the aforementioned drawbacks, developing a system such as the one described below and is included in its essentiality in the first revindication.

EXPLANATION OF THE INVENTION

Having explained the above and taking into account, among others, the difficulties presented in the current technique, the invention constitutes a biphasic thermal transmission system with improved characteristics to the previous ones, based on the technique of thermal utilization of the tendency to thermodynamic equilibrium of fluids and its vapor pressure.

Considering in the first point, that all liquid / vapor absorbs / gives a large amount of energy in the form of heat based on a change of liquid state to steam or steam to liquid, in process that is quantified with the physical concept of latent heat of a fluid based on its enthalpy of change of state, and that this design also takes advantage of not only the energy in the form of heat based on its change of state of its fluid but also its specific heat in both states. Being therefore a hybrid system of the previous ones that has advantaged characteristics between both systems of gaseous-vapor and liquid thermal transfer at the same time.

Considering that any liquid is capable of being evaporated at the absolute ford from the so-called triple point, that there are infinite molecular groups both pure and in mixture that are liquid stable and safe with calorific capacities, serving as an example, the liquid water, which weighs To look striking, it has a boiling temperature at the ford of 1 ° C. On the other hand, fluids in a liquid state confined in a constant volume can maintain their liquid state at very high temperatures since their own vapor balances the pressure to a stable point or what is known as thermodynamic equilibrium of vapor pressure, if well this effect has a limit at a point known as the critical point, where the vapor-liquid can not coexist as clearly differentiated elements, in the case of water this point is from 22 MPa. pressure and 374 ° C. Therefore, pure water can be used, as an example in this biphasic thermal transfer system with a range of operational temperatures of 1 - 374 ° C.

Together these concepts, and considering a single constant volume equal the sum of several volumes spaced in space, but connected between them by means of pipes, what is described below is what is described as inventive innovation with industrial application as a thermal transfer system .

Basic components of the system:

- A heat transfer fluid capable of existing in the range of temperatures and operating pressures in two states (liquid and vapor).

- A heat emitter with thermal transfer capacity to the fluid (steam) (radiator, exchanger, serpentm, fan-coil, split, etc).

- A heat receiver with thermal transfer capacity to a fluid (liquid) within a closed system (solar collector, boiler, encapsulated electrical resistance, motor, device to be cooled).

- Roundtrip interconnection pipes.

- Load / service valve.

- The acceleration of the liquid fluid in the direction towards the receiver by the gravitational action or other device that replaces it.

The functional explanation of the invention starts by considering together the physical elements that constitute the total volume of the thermal transmission installation, as shown in the figures and as claimed, therefore the receiver, emitter, pipeline, pipeline of return and valve of load in closed position, form a unique closed and hermetic volume. Together these, the heat transfer fluid should be understood as a fluid that can exist within the range of operation, as fluid in liquid and vapor state (biphasic), therefore, free to occupy the entire volume of the installation in its liquid form and gaseous, which in practice is achieved by emptying the system and its subsequent integration through the load / service valve, or integrating the fluid previously, and take it to a temperature in which its vapor pressure is higher than atmospheric and purging the air contained by accessories added for this purpose, such as purgers.

Once the installation gathers the basic elements as claimed in such a way, it is calculated that the volumetric capacity of the heat receiver is occupied by the fluid in liquid state and with free steam output, therefore leaving the rest of the installation occupied by the steam of the fluid, this tendera alone constantly to balance its thermodynamic state of pressure and temperature, henceforth PT, as long as in the receiver T> P with respect to its characteristic curve of saturation PT of thermodynamic equilibrium, considering The pure fluid, or those azeotropic and zeotropic mixtures, as a heat transfer fluid.

Taking into account the above and from it, the circuit obeys to three different possibilities of operation:

- Operation 1, heat receiver temperature equal to that of the heat emitter:

The fluid in the receiver is at the same temperature as the emitter, being in both coinciding with the equilibrium vapor pressure for a given temperature, there is no thermal exchange and the system remains in thermodynamic equilibrium with its own vapor.

- Operation 2, the heat receiver is at a higher temperature than the heat emitter:

In this case, the fluid contained in the receiver receives energy in the form of heat increasing its temperature and pressure according to its characteristic PT diagram, but because the steam is free to circulate towards the heat emitter with lower pressure and temperature, fulfilling the thermodynamic imbalance in the receiver T> P, this thermodynamic deviation of the fluid in the receiver is compensated by the evaporation of the fluid, whose molecules with more energy vaporize and move as saturated steam or superheated steam by pressure difference through the pipes to the emitter / is, transporting the heat equal to the enthalpy of vaporization characteristic of the fluid plus the specific heat of the superheated steam.

Once the steam has reached the emitter, the thermodynamic phenomenon inverse to the receiver happens (T <P of thermodynamic equilibrium), the vapor molecules in contact with the surface of the emitter yield heat energy, they condense, therefore decreasing their volume and it creates a depression that is compensated with the arrival of more vapor from the receiver (specifically), therefore in the emitter heat energy is delivered based on its enthalpy of condensation, specific heat, vapor phase and specific heat in the liquid phase.

When liquefied, there is a contribution of vapor from the receiver, a large difference of vapor-liquid densities, and a height difference between both, the design of the circuit linked to the action of gravity (or another device that replaces it), the fluid returns to the receiver where the cycle is repeated until it reaches the state of thermodynamic equilibrium PT or the temperature of the receiver is reached equilibrium T <P.

- Operation 3, the heat sink is at a lower temperature than the heat emitter:

In this case, considering that the thermodynamic imbalance T> P is fulfilled in the emitter, the inverse phenomenon does not occur because there are no liquid molecules in the liquid state that vaporize and perform the cycle, there is a density difference in the phase emitter-receiver vapor, but the circulation based on this difference is blocked by the same density of the liquid in its return pipe that does not allow the steam to flow to the receiver, so that the inverse heat exchange emitter to receiver is zero.

Thanks to the described characteristics, a thermal transmission system is achieved that widely innovates the current technique, possessing an extended industrial applicability with the following characteristics that among others include:

- It is exempt in its basic form of permanent rotating moving parts and / or circulation pumps, therefore, it has greater reliability and efficiency than liquid phase systems with such elements.

- Very low maintenance, no loss or reposition of fluid, less accessories to maintain.

- Adaptability to certain facilities that were previously designed to work with thermal transmission systems in a liquid state.

- High thermal transfer rates due to the low kinematic viscosity of the heat-carrying vapor, low thermal gradients between emitter-receiver even over long distances> 25m.

- Wide ranges of temperature and operating pressure as well as applicability for infinity of pure caloportantes fluids and mixtures (Water, methanol, butane, hexane, ethylene glycol ...) Does not require additional expansion devices, because the contained vapor is a compressible fluid before the liquid expansion.

- Hermetic.

- Ability to operate at both higher and lower atmospheric pressures.

- The diameters of the necessary transfer pipes are of smaller size, comparing the same thermal transport capacity of the traditional liquid phase systems due to the low kinematic viscosity of the heat transfer vapor of this system.

- They have a higher efficiency and efficiency in thermal transmission per kg of fluid transmitted compared to forced circulation systems as well as thermal convection (thermosiphon)

- Irreversibility of heat transport between heat emitter to receiver without accessories.

- Applicability for both emitters and multiple heat receivers installed in parallel and series.

- Greater homogeneity in the thermal distribution in different heat emitters affected by large differences in height-distances to the heat sink.

Unless otherwise indicated, all technical and scientific elements used herein have the meaning usually understood by one of ordinary skill in the art to which this invention pertains. In the practice of the present invention, methods and materials similar or equivalent to those described in the specification can be used.

Throughout the description and the claims the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be apparent in part from the description and in part from the practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical realization thereof, a set of drawings is included as an integral part of said description. where with illustrative and non-limiting character, the following has been represented:

- Figure 1 shows a basic diagram of the system with gravity operation.

- Figure 2 shows a diagram of the system exposing its operation with several transmitters and receivers both in series and in parallel by gravity.

- Figure 3 shows a diagram of the system exposing its operation with several transmitters and receivers both in series and in parallel, where a condensate collector assembly plus impulse pump is implemented to give the heat receivers the freedom of position with respect to the height of the the heat emitters.

- Figure 4 shows a diagram of the system exposing its operation with several transmitters and receivers both in series and in parallel where a condensate collector assembly plus a booster pump is implemented to give the heat receivers the freedom of positioning with respect to the height of the The heat emitters, as well as the series emitter concept, exemplify a steam superheater.

A list of the different elements represented in the figures comprising the invention is provided below:

1 = Heat receiver, comprising: solar collector, boiler, encapsulated electrical resistance, motor, device to be cooled ...

2 = Emitter of heat, which includes: radiator, exchanger, serpentm, fan-coil, split ...

3 = Load valve or analog device.

4 = Return pipe (liquid).

5 = One-way pipe (steam).

6 = Acceleration of gravity

7 = A condensate collector set plus booster pump, or analog device. 8 = A steam superheater or analog device.

PREFERRED EMBODIMENT OF THE INVENTION

In view of the figures, a preferred embodiment of the proposed invention according to FIG. 1 is described below:

Bearing in mind that this system comprises a multitude of assumable devices as heat receiver (1) heat emitter (2) and heat transfer fluid, and that presenting this preferred embodiment of the invention in accordance with this broad concept is not feasible in its objective of improving the understanding of the invention together with its implementation, will be proposed as an example a thermo-solar installation composed of a flat solar collector as heat receiver (1) and a heat exchanger serpentm inside a water accumulator as a heat emitter (2) and with pure methanol as a heat transfer fluid.

Starting from a structure conforming to specifications that provide us with a difference of acceptable heights according to the figure, a flat solar collector panel (1) will be installed in its lower part with a coherent angle to the solar radiation, also in the structure at the top, and above the highest level of the collector will be an accumulator set with 300l. of water in which a serpentm-type exchanger (2) is integrated, where the upper entrance to the serpentm (2) is joined by copper pipe (5) to the upper outlet of the collector (1), then install a copper pipe (4) starting from the lower outlet of the serpentm (2), to the lower entrance of the collector (1) as well install a load / service valve (3) on the return pipe (4).

The system will be put in ford with a tool usually known as a ford pump, knowing previously the volume data of the collector and of the installed pipeline, after the ford the system integrates the heat transfer fluid, with methanol being chosen (- 50 ° C «68 pa. And 136.7 ° C« 1Mpa.), In an amount of approximately 80% of the volume of the collector plus the volume of the equivalent level in the return pipeline, the rest being occupied by methanol in the vapor state.

Taking into account that the installation is solar, if there is incident solar radiation, immediately the cycle will start, capturing heat the fluid in the whole surface in the collector (1), evaporating in the upper part, transporting the heat quickly through the pipeline one way (5) in the form of vapor, reaching the serpentm (2) yielding heat through it to the water, as latent and specific heat of both phases, condensing and by action of gravity (6), it will return through the return (4) in its liquid form to enter again in the capador and so on, until there is a thermal equilibrium between the two or there is no sun in this case.

It is further verified that this preferred embodiment is also feasible in multiple receivers and transmitters in parallel according to FIG. 2, and that the implementation of a condensate pump described in FIG. 3 is feasible and that it is also possible to implement a steam superheater in series or another analogous device according to figure 4.

Having sufficiently described the nature of the present invention, as well as the way of putting it into practice, it is stated that, within its essentiality, it could be carried out in other forms of realization that differ in detail from that indicated at an example rate. , and which will also reach the protection that is collected, provided that it does not alter, change or modify its fundamental principle.

Claims (7)

1.- Two-phase thermal transmission system characterized comprising: - A pure fluid or mixture of two or more fluids in biphasic form (liquid and vapor), integrated within a closed and hermetic circuit, without other element, impurity and / or pressure in the circuit more than the one coming from its own pressure. steam characteristic. With disposition and level such that at least one heat sink (1), is found with fluid available in a liquid state that absorbs heat and is therefore evaporated, in such a way that the passage of steam through a pipeline is allowed (5) towards at least one heat emitter (2), where heat gives off and is condensed in the heat emitter (2), being directed as liquid by a return pipe (4) to the heat receiver (1) by a gravitational and / or mechanical acceleration, reaching a level such that it allows the liquid part to absorb again heat energy. 2. - Two-phase thermal transmission system according to claim 1, characterized in that the heat receiver (1) is at a height with respect to the horizontal, lower than the height of the emitter (2) and as a fluid return acceleration is used the gravity. 3. - Two-phase thermal transmission system according to claim 1 characterized in that the device used for the acceleration of the fluid in the direction of the receiver is a condensate pump (7) or analogous device that pumps the condensed fluid to the heat receiver (1) both continuously and discontinuously. 4. - biphasic thermal transmission system according to claim 1 or 3 characterized in that at the outlet of the heat receiver (1) a steam superheater (8) is arranged in series to increase the steam outlet temperature above its temperature of saturation. 5. - Two-phase thermal transmission system according to claim 3 or 4 characterized in that the receiver (1) is at a height with respect to the horizontal above the height of the emitter (2). 6. - Two-phase thermal transmission system according to one of claims 1 to 5 wherein multiple thermal receivers (1) and / or thermal emitters (2) are joined in parallel or series. 7. Two-phase thermal transmission system according to one of claims 1 to 6 containing devices for distribution and control of the elements thereof, such as: Valves, distributors, detectors, thermometers, manometers, vacuum gauges, transmitters, thermostats, dilators, traps, visors ...