Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F12/00—Use of energy recovery systems in air conditioning, ventilation or screening
  • F24F12/001—Use of energy recovery systems in air conditioning, ventilation or screening with heat-exchange between supplied and exhausted air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F13/00—Details common to, or for air-conditioning, air-humidification, ventilation or use of air currents for screening
  • F24F13/24—Means for preventing or suppressing noise
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28C—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA COME INTO DIRECT CONTACT WITHOUT CHEMICAL INTERACTION
  • F28C3/00—Other direct-contact heat-exchange apparatus
  • F28C3/06—Other direct-contact heat-exchange apparatus the heat-exchange media being a liquid and a gas or vapour
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
  • F28F19/006—Preventing deposits of ice
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
  • Y02B30/56—Heat recovery units

Definitions

• the invention relates to a method for recovering heat, in which method heat is recovered from exhaust air by a heat recovery unit arranged on the exhaust side and the recovered heat is transferred to supply air.
• the invention also relates to an arrangement for recovering heat.
• the object of the invention is to provide a method and an arrangement by which the drawbacks of the prior art can be eliminated. This is achieved by the method and arrangement provided by the invention.
• the method of the invention is characterized by spreading non-freezing liquid on the surfaces of the heat recovery unit on the exhaust side.
• the arrangement according to the invention is characterized in that in connection with the heat recovery unit are arranged means for spreading non-freezing liquid on the surfaces of the heat recovery unit.
• the advantage of the invention is, above all, that it makes it possible to provide protection against freezing and, in addition, that the efficiency of heat recovery is increased unlike in the previously known units, where it is reduced.
• the improvement in the heat recovery results from the fact that the heat-transfer coefficient of a wet heat-transfer radiator is higher than that of a dry radiator. This is described in Finnish Patent Application 933,534. In fact, the efficiency of the unit in the summer can be increased and the freezing in the winter prevented with one and the same unit.
• a further advantage is that the non- freezing liquids used are hygroscopic, in other words, they significantly drop the partial pressure of saturated steam. They dry the air, and so the heat of evaporation can be recovered.
• fig. 1 shows a general view of a first embodiment of an arrangement according to the invention
• fig. 2 shows a general view of a second embodiment according to the invention
• fig. 3 shows a general view of a third embodiment according to the invention
• fig. 4 shows a general view of a fourth embodiment according to the invention.
• Fig. 1 shows a general view of an arrangement according to the invention.
• Reference number 1 indicates an outlet channel through which the indoor air flows from the building. The flow of the indoor air through the outlet channel 1 is indicated in the figure by arrows.
• Reference number 2 indicates, generally, a heat recovery unit, i.e. heat exchanger, arranged in the outlet channel 1 to recover heat from the exhaust air. The heat recovered from the exhaust air is transferred from the heat recovery unit 2 to a second heat exchanger arranged in the inlet channel, and the recovered heat is transferred by the heat exchanger to the supply air.
• the inlet channel and the second heat exchanger arranged in it are not shown in fig. 1, since they are conventional technology to a person skilled in the art.
• non-freezing liquid is spread on the surfaces of the heat recovery unit 2 on the exhaust side.
• Means spreading non-freezing liquid are indicated in the figure by number 3.
• the means 3 may comprise, for example, a moistening mat, which is moistened with non- freezing liquid and which spreads the liquid on the surfaces of the heat recovery unit.
• the non-freezing liquid spread on the surfaces of the heat recovery unit runs along the surfaces in the manner indicated by arrows in the figure.
• the non-freezing liquid may be any non-corrosive substance that is safe to the environment. Examples for suitable liquids include calcium magnesium acetate/water, propylene glycol/ water, urea/water, etc.
• an accumulating device 4 which is arranged to receive the non-freezing liquid running from the surfaces of the heat recovery unit 2.
• the accumulating device 4 may be, for example, a reservoir.
• the arrangement further comprises a concentrator 5, which is arranged to increase the concentration of the non-freezing liquid before the liquid is re-spread on the surfaces of the heat recovery unit.
• the diluted but still non-freezing liquid running from the heat recovery unit 2 is conducted from the accumulating device 4 through a pipe 6 to the concentrator 5.
• the pipe 6 can be provided with an equalizing reservoir 7.
• a pump 8 can also be arranged in the pipe 6.
• the concentration of the liquid is increased in the concentrator 5 and the liquid is conducted with a spray pipe 9 from the concentrator 5 to a moistening mat serving as a spreader 3.
• the liquid is spread on the moistening mat by means of nozzles 10 arranged in the spray pipe 9.
• the flow direction of the liquid from the accumulating device 4 to the moistening mat serving as a spreader 3 is indicated in the figure by arrows.
• the concentrator 5 may be any suitable apparatus, such as a reverse osmosis apparatus, an apparatus operating on the evaporation principle, etc.
• the water separated from the liquid can be removed from the concentrator e.g. by means of an aggregate 11. The combined effect may be e.g.
• the minimum temperature of the exhaust air is 0°C: nominal efficiency of recovery 70% actual efficiency 46% recovered energy 32.5 kJ/kg dry air heating energy needed 47.5 kJ/kg dry air additional heating demand 15.0 kJ/kg dry air.
• the apparatus provided by the invention does not have a temperature limit for the exhaust air: actual efficiency > 70% final temperature of exhaust air > -12.5°C recovered energy > 45.5 kJ/kg dry air additional heating demand ⁇ 2.0 kJ/kg dry air.
• the final temperature of the exhaust air may be slightly below 0°C without causing too much freezing.
• the effects of a wet radiator and of hygroscopicity have not been taken into account except with marks ⁇ and >.
• the basic idea of the invention can also be applied by not attempting to prevent freezing altogether but by stopping icing and/or by defrosting when the ice starts to impair heat recovery. Heat recovery then becomes periodical.
• the advantage of this kind of embodiment is that less non-freezing liquid is needed.
• the above operation can be controlled e.g. such that the supply of liquid is started when the pressure loss of the heat recovery unit exceeds a certain value, or when the outdoor temperature is below a certain value.
• the start-up can also be based on measuring the temperatures of the heat transfer liquid and/or the exhaust air and/or the supply air of the heat recovery unit, or in more advanced systems, on reduction of the efficiency of recovery computed at a control centre. All these control methods, which are known per se, are naturally included in the invention.
• the equipment can be simplified by not including a regeneration unit.
• the liquid is accumulated in a reservoir 7, from where it can be taken elsewhere for regeneration, or the regeneration can also be performed on the spot e.g. by manually adding concentrated liquid, salt, etc.
• This kind of embodiment is shown in fig. 2. Accumulation is not always necessary, if the liquid can be directly conducted e.g. by a pipe 15 e.g. to sewage purification or to a utilization process.
• This kind of embodiment is shown in fig. 3.
• the liquid is supplied from a supply reservoir 14.
• the non-freezing liquid can also be concentrated without an actual concentrator using the air-conditioning unit itself e.g. in a situation where air-conditioning units are used for heating a building at night or at other times when the building is not in use.
• This kind of embodiment is presented in fig. 4.
• exhaust air is conducted from the heat recovery unit 2 back to the building, to which no outdoor air is supplied at all.
• a heat exchanger for supply air is indicated in fig. 3 by reference number 12.
• Additional air L is supplied to the recovery unit 2 e.g. at point 13. The additional heat heat heats the air and also vaporizes water from the liquid spread on the surfaces of the recovery unit 2, whereby the liquid is concentrated.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
• Steam Or Hot-Water Central Heating Systems (AREA)
• Drying Of Gases (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8544077

Family Applications (1)

Country Status (6)

Cited By (1)

Citations (7)

• 1995
  • 1995-09-22 FI FI954508A patent/FI102319B1/fi active
• 1996
  • 1996-09-18 AU AU69897/96A patent/AU6989796A/en not_active Abandoned
  • 1996-09-18 CA CA002232718A patent/CA2232718A1/en not_active Abandoned
  • 1996-09-18 WO PCT/FI1996/000492 patent/WO1997011318A1/en active Application Filing
• 1998
  • 1998-03-20 NO NO981274A patent/NO981274L/no unknown
  • 1998-03-20 SE SE9800933A patent/SE9800933L/xx unknown

Patent Citations (7)

Non-Patent Citations (1)

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