Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
  • F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
  • F24H7/00—Storage heaters, i.e. heaters in which the energy is stored as heat in masses for subsequent release
  • F24H7/02—Storage heaters, i.e. heaters in which the energy is stored as heat in masses for subsequent release the released heat being conveyed to a transfer fluid
  • F24H7/0208—Storage heaters, i.e. heaters in which the energy is stored as heat in masses for subsequent release the released heat being conveyed to a transfer fluid using electrical energy supply
  • F24H7/0233—Storage heaters, i.e. heaters in which the energy is stored as heat in masses for subsequent release the released heat being conveyed to a transfer fluid using electrical energy supply the transfer fluid being water

Definitions

• water heaters in particular electric water heaters, meet the daily needs of a family. For a family of four consuming approximately 150 liters of water per day, these water heaters generally have a volume of 200 liters.
• hot water By regulation, hot water must be stored at a temperature equal to or higher than 60 ° C to avoid bacterial proliferation of the legionella type. There is therefore a temperature difference of 40K between the hot water which is stored in the water heater and the room in which it is located and whose temperature is of the order of 20 ° C.
• the hot water from the water tank is stored in a container (also known as a "balloon") generally of cylindrical shape having a diameter of 45 cm and a height of more than 125 cm (not including the thermal insulating envelope).
• the daily heat losses of such a water heater with a capacity of 200 liters are significant. They are between 1.4 and 2 kWh per day.
• the hot water consumed is replaced by an equivalent volume of cold water entering from the bottom of the device.
• Such water heaters have a major defect. In fact, even if anodes are placed next to the heating resistance at the base of the device, the fouling by limestone and the various mineral salts is significant and causes additional energy losses due to the additional thermal resistances associated with the deposit. .
• the invention aims to remedy these drawbacks and to improve the energy balance of water heaters. More generally, the invention aims to improve the energy balance of heat storage processes and devices of which the water heater cylinders are only one particular application.
• the heat accumulation method according to the invention consists in providing a container containing a first fluid under its vapor pressure and in providing the following steps:
• the heat is stored in the first fluid under its vapor pressure, in particular water, in a sealed container,
• the heat is transferred by condensation of the vapor phase of said fluid on the external surface of an exchanger, located in the vapor phase of the first fluid,
• - Heat is supplied to said container by means of a hot source, in particular a heating resistor or a burner.
• the heat transfer is effected by heat pipe effect, that is to say by evapo-condensation.
• the container is thermally insulated.
• the use of a fluid under its vapor pressure makes it possible to reduce the dimensions of the container by approximately 75%. to meet the same needs. Given this reduction in volume, for an identical cost of insulation, the performance of the envelope is improved insulating thermal and reducing the heat losses by a factor of 3 to 4.
• sufficient heat is supplied to maintain the first fluid at a temperature such that the pressure in the container is substantially equal to atmospheric pressure.
• heat can be provided in an amount sufficient to maintain the first fluid at a temperature such that the absolute pressure in the container is greater than atmospheric pressure, in particular substantially equal to 2 bar.
• the holding temperature is approximately 120 ° C for a pressure of 2 bar.
• the exchanger comprises a circuit traversed by a second fluid, in particular water, the temperature of which is lower than that of the first fluid.
• Heat can be stored not only in the first fluid but also in a material undergoing a solid / liquid phase change in the range of temperature variation of the first fluid in the container.
• the solid / liquid phase change material is introduced into nodules, in particular plastic capsules, and these nodules are immersed in the first fluid.
• a mass of solid / liquid phase change material is introduced into a container separate from the container of the first fluid, and this container is thermally connected to the container by a heat exchanger which can be turned on or off. at will.
• the container containing the phase change material may further include a heating plate. You can adjust the capacity of the water heater by whether or not using the additional resistance (heating plate) provided in the container containing the phase change material.
• the phase change material can be constituted by a vegetable wax, a beeswax or a mineral wax.
• an additive is introduced into the fluid of the container which makes it possible to raise the temperature of the liquid phase without increasing the vapor pressure, while retaining the heat capacity.
• this first fluid is constituted by water
• the additive can be constituted by sodium chloride.
• the present invention also relates to a heat storage device comprising: a sealed container containing a fluid, in particular water, under its vapor pressure,
• An exchanger located in the part of the container containing the vapor phase of said fluid, a hot source, in particular a heating resistor or a burner, to provide heat to the liquid phase of said fluid.
• the heat storage device further comprises a thermal insulator enveloping the container.
• the amount of heat provided by the hot source is determined sufficiently to maintain the fluid at a temperature such that the maximum pressure variation inside the container is ⁇ 1 bar absolute.
• This variation corresponds to a container which, during the initial charge of water, can be under a pressure of 20 mb absolute at a temperature of 20 ° C while its absolute pressure will be approximately 2 bar for a temperature of 120 ° C.
• the exchanger comprises a circuit traversed by a second fluid, in particular water.
• the present invention also relates to the application of the method and the device according to the invention and their preferred alternative embodiments to the production of hot water storage tank, especially for water heaters.
• Figure 1 of these drawings is a schematic view, in open perspective, of an alternative embodiment of a heat storage device 1 according to the invention.
• Figure 2 is a schematic section of another variant of a device according to the invention.
• FIG. 3, finally, is a schematic vertical section of a variant of the device of FIG. 2.
• the temperature of cold water varies relatively little during the year, between 12 and 22 ° C.
• the cold water 4c circulates in an exchanger 4, preferably in a copper circuit 4b, located at the top of the tank.
• the water circulating in the exchanger 4 is heated by condensation 3 of the water vapor 2b coming from the evaporation at the free surface 2c of the hot water 2a stored, under its vapor pressure, in the tank has heat pipe effect.
• the hot water 2a is stored at a temperature varying, for example, between 100 and 90 ° C. These temperature levels are chosen to limit losses and make the internal pressure of the hot water tank vary between 0.7 and 1 bar absolute.
• the balloon 1 is surrounded by a thermally insulating envelope 6.
• the tank 1 is designed to withstand higher pressures, in particular at least 2 bar absolute so that the water can be stored at a temperature of around 120 ° C.
• the storage capacity under the same volume is increased.
• the hot water stock is 50 liters. It is heated to 100 ° C, for example.
• the opening of the tap causes a circulation of cold water 4c which enters one exchanger 4 located at the top of the heat storage tank.
• This cold water enters at a variable temperature between 12 and 22 ° C. It is reheated to an outlet temperature which can vary between 45 and 60 ° C.
• the flow rate in circuit 4b of the exchanger 4 is adjusted and / or the mixture with additional cold water at the outlet of the exchanger 4.
• the exchanger 4 constitutes a cold point located in the vapor phase 2b of the heat pipe effect.
• the hot water stored is at a temperature ⁇ e 100 ° C (for example) at the start of the day and 90 ° C (for example) at the end of the day
• this water evaporates on the liore surface 2c . It comes to condense 3 on the outer wall 4a of the exchanger and thus heats the circulating water 4b inside the exchanger 4.
• the condensed water 3 drops in drops on the water reserve 2a where it comes mix. This results in a slight lowering, between 100 and 90 ° C, of the temperature of the stored water.
• the container 1 (the balloon) with heat pipe effect allows to radically modify the volume u storage since:
• the energy exchanged on one side of the exchanger is consisting of a so-called sensitive energy, allowing the liquid water to heat up for temperature differences of around 40K (variable between 23 and 58K) and
• the usual domestic hot water flow rates are around 10 1 / min, the power exchanged is therefore high: 27.8 kW.
• the latent heat of vaporization of water is 2250 kJ / kg for temperatures varying between 90 and 110 ° C, it is sufficient that the evapo-condensation flow rate originating from storage is 12 g / s.
• the total operating time over a day is 900 s (15 min for 150 liters of domestic hot water).
• the evapo-condensed mass is a little more than 11 kg.
• These 11 kg of water drop by drop, at a variable temperature between 65 and 50 ° C, in the liquid phase 2a (initially at 100 ° C) with which they mix.
• the average temperature over the day is 95 ° C.
• the average temperature is 60 ° C.
• the difference for the 50 liter tank is therefore 75K and ⁇ e 40K for the 200 liter tank.
• FIG. 2 shows a general cold water inlet E, provided with a control valve, which is divided downstream along a line with control valve for the supply 4c of the exchanger 4, and according to a bypass line B or by-pass, also fitted with a valve, which leads to an inlet of a mixer M, another inlet of which receives hot water from the exchanger 4.
• the phase change material 7 can be packaged in the form of nodules 8, for example by filling plastic capsules with the material 7.
• the nodules 8 are immersed in water 2a; they make it possible to split the material 7 and to obtain good heat exchanges by increasing the exchange surface.
• the phase change material 7 may be Carnauba wax having a phase change temperature of 82 ° C to 84 ° C with latent heat of fusion of 190 J / g. If we admit a low temperature of
• the increase in the heat storage capacity of a volume of water of 60 liters comprising 10 kg of nodules is approximately 20%.
• Figure 3 shows a variant in which the material 7 has phase change is placed en masse in a container 9 separated from that containing the water 2a.
• the thermal coupling between the stored hot water 2a and the material 7 is ensured by an exchanger 10 comprising a coil 10 embedded in the mass of the material 7 and allowing a circulation of hot water 2a coming to the tank 1 and returning to this tank.
• the start-up or shutdown of the exchanger 10 can be controlled using a valve
• An additional heating resistor 12 for example in the form of a plate, is provided in the container 9.
• the heat storage with the material 7 has phase change, according to Figures 2 and 3, is carried out as follows.
• a water temperature 2a lower than the phase change temperature of the material 7, the latter is in the solid state in the nodules 8, or in the container 9.
• the material 7 of the nodules 8 (FIG. 2) changes from the solid state to the liquid state by absorbing the latent heat of fusion, when the temperature of the water 2a crosses, by increasing values, the temperature of change of phase.
• FIG. 3 when the exchanger 10 is in service.
• the temperature of the water 2a decreases as a result of the removal of heat due to the withdrawal of sanitary water through the exchanger 4.
• the temperature of the water 2a reaches, by decreasing values, the solidification temperature of material 7, the latter releases its latent heat of fusion-solidification.
• FIG. 3 enables the container 9 containing the phase change material 7 to be put into service or not and thus to vary the storage capacity of the water heater as required.
• the presence of the additional heating resistor 12 makes it possible to modulate the power of the water heater by using or not using this additional resistor.
• the phase change material 7 is chosen so as not to pose a problem of environmental pollution at the end of the life of the equipment.
• an additive can be added to the liquid 2a which makes it possible to increase the temperature of the liquid for the same vapor pressure, while retaining the storage capacity.
• the liquid 2a is water
• the water heater can of course be regulated, in particular as regards the intervention of the material 7 and of the auxiliary resistance 12 in the case of FIG. 3.
• the method and the device for heat accumulation according to the invention makes it possible to:
• provision is made for regulating the capacity of the thermal storage of the water heater which is carried out by counting the time of withdrawal of hot water by the user. For example, if the regulation (by time counting) finds a reduction in the daily duration of use, that is to say a significant reduction in the consumption of hot water compared to the previous days, the storage capacity thermal of the water heater will be adapted either by decreasing the storage water temperature, or by not heating the container 9 containing the liquid solid phase change material. Conversely, the increase in thermal storage capacity is carried out by directly controlling the heating during the day and this, as a function of the counting of the time for drawing off hot water.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Heat-Pump Type And Storage Water Heaters (AREA)

Applications Claiming Priority (5)

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• 2000
  • 2000-06-22 FR FR0008026A patent/FR2800447B1/fr not_active Expired - Fee Related
  • 2000-10-03 EP EP00966260A patent/EP1224427A1/de not_active Withdrawn
  • 2000-10-03 CA CA002389023A patent/CA2389023A1/fr not_active Abandoned
  • 2000-10-03 WO PCT/FR2000/002734 patent/WO2001031265A1/fr not_active Application Discontinuation

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