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WO1982003677A1 - Systeme de chauffage solaire d'eau d'un reservoir a double paroi a drain de retour hermetique - Google Patents

Systeme de chauffage solaire d'eau d'un reservoir a double paroi a drain de retour hermetique Download PDF

Info

Publication number
WO1982003677A1
WO1982003677A1 PCT/US1982/000444 US8200444W WO8203677A1 WO 1982003677 A1 WO1982003677 A1 WO 1982003677A1 US 8200444 W US8200444 W US 8200444W WO 8203677 A1 WO8203677 A1 WO 8203677A1
Authority
WO
WIPO (PCT)
Prior art keywords
jacket
fluid
collector
heat
transfer fluid
Prior art date
Application number
PCT/US1982/000444
Other languages
English (en)
Inventor
Corp Altas
Howard E Grunes
Dennis J Morrison
Original Assignee
Corp Altas
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Corp Altas filed Critical Corp Altas
Priority to AU84513/82A priority Critical patent/AU8451382A/en
Publication of WO1982003677A1 publication Critical patent/WO1982003677A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D11/00—Central heating systems using heat accumulated in storage masses
    • F24D11/002—Central heating systems using heat accumulated in storage masses water heating system
    • F24D11/003—Central heating systems using heat accumulated in storage masses water heating system combined with solar energy
    • 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
    • Y02B10/00—Integration of renewable energy sources in buildings
    • Y02B10/20—Solar thermal

Definitions

  • the present invention relates generally to heating systems and, in particular, to indirect drain-back solar water heating systems.
  • the typical solar heating system utilizes a solar collector, which can be a panel positioned for maximum exposure to solar energy, and a means for transferring the heat absorbed by the collector to the subject matter to be heated.
  • a solar collector which can be a panel positioned for maximum exposure to solar energy
  • systems which have been developed to implement such heat transfer may be categorized as indirect or direct heating systems.
  • direct heating systems the subject matter to be heated, e.g. water, air, or other fluids, is circu ⁇ lated through the solar collector where there is a direct transfer of absorbed heat to the subject matter.
  • the indirect systems there is a closed solar collector loop for absorbing heat from the collector and a heat exchanger for transferring heat from the solar collector loop to the subject matter to be heated.
  • the solar collector loop utilizes a heat transfer fluid which is circulated through the solar collector, where the fluid absorbs heat from the collector, and thence into the heat exchanger.
  • the heat exchanger can be a part of the solar collector loop shaped, for example, in a coil, and positioned to. be surrounded by the subject matter to be heated. Heat can thereby be transferred from the circulating heat transfer fluid through the walls of the coil to the surrounding subject matter.
  • Other heat exchanger configurations include the use of a reservoir as part of the solar collector loop for storing heated heat tran ⁇ fer fluid. Disposed within the reservoir is a second loop, through which is circulated the subject matter to be heated. The loop is shaped and positioned so that heat from the heat transfer liquid within the reservoir is transferred through the walls of the second loop to the circulating subject matter to be heated.
  • Solar heating systems may be characterized as non-draining or draining. Draining systems may be further characterized as drain-back or drain-down. The difference between the systems has to do with solar heating operation when the solar energy available is insufficient to prevent the fluid in the collector from freezing, or when the subject matter to be heated has already reached the maximum desired temperature and continued absorption of heat by the collector will cause the fluid in the collector to boil or to generate excessive temperature or pressure.
  • the collector In the non-draining systems, the collector is always filled with fluid. In order to prevent freeze damage, either a non-freezing fluid is used or the fluid is circulated when it approaches the freezing temperature, drawing some heat from the heated subject matter, thereby keeping the fluid above the freezing temperature, but also causing heat loss.
  • non-freezing fluids in the collector loop usually requires the use of a double-walled heat exchanger between the collector fluid and the heated subject matter to insure no contamination of the heated subject matter, which lowers energy collection efficiency.
  • high- boiling temperature fluids such as silicone or hydro ⁇ carbon oils are used, or the excess pressure developed is either vented to the atmosphere or transferred to a holding reservoir.
  • the heat transfer fluid In drain down systems, the heat transfer fluid is drained from the collector and discarded whenever the fluid approaches the fluid freezing temperature. Boil-over protection is usually achieved in the same way it is for a non-draining system, that is, by venting the fluid when it boils.
  • the heat transfer fluid is drained out of the collector and transferred to a reservoir and is replaced by a gas when there is insufficient heat available, or the subject matter to be heated has reached its maximum desired temperature.
  • the gas will neither freeze when outside temperatures are very cold nor create excessive pressure when excess temperatures are generated in the solar collector.
  • the present invention is directed to draining systems and, in particular, to indirect drain-back systems.
  • Direct heating draining systems have the primary advantage of not requiring a heat exchanger between the collector fluid and solar storage. They are usually drain down systems and have the disadvantage of needing more complex controls and components than other systems. Direct heating draining systems require special elec ⁇ trically actuated hardware to insure correct draining operation. If these systems fail, freezing or boiling can occur. Additionally, by circulating potable water, for example, through the collectors, mineral deposits can eventually build up inside the collector passage which can reduce performance. Furthermore, subjecting the collectors and supply plumbing to water main pressure increases the possibility of leaks.
  • Boiling of the collector fluid which is a concern in non-draining closed loop system and in some drain down systems is not a concern with drain-back systems. In drain-back systems it is easy to avoid introducing fluid to the collector when boiling could occur.
  • drain-back systems In drain-back systems it is easy to avoid introducing fluid to the collector when boiling could occur.
  • the antifreeze solution is forced out of the system through the pressure relief valve. The system must then be refilled before energy collection can resume. Drain down systems usually refill themselves when boiling occurs but provisions must be made to direct the hot fluid to a safe place and vents must function properly.
  • Indirect drain-back systems overcome the problems of antifreeze systems and direct heating draining systems. Whenever the pump is not running, the system is in the drained mode, the possibility of freezing and boiling is virtually eliminated even if the pump fails.
  • Indirect drain-back systems employ a single walled heat exchanger between the heat transfer fluid in the collector loop and the subject matter to be heated, e.g. potable water. This allows the collector loop to operate at low pressure in a closed configuration eliminating the need for solenoid valves or vents. Also since the collector loop is closed, mineral deposits are not a problem.
  • OMPI Typically, these systems employ a pump, differen ⁇ tial temperature controller, heat exchanger and fluid reservoir.
  • the subject matter to be heated is held in a storage tank.
  • the controller turns the pump on.
  • Heat transfer fluid is pumped from the fluid reservoir to the collector and establishes a loop between the reservoir and the collector. Heat energy is then transferred from the fluid reservoir to the storage tank through a single- walled heat exchanger.
  • the pump shuts off and the fluid drains back into the reservoir. In this way, there are no freezing or boiling problems since the fluid is not allowed into the collectors if they are too cold or if the fluid is too hot.
  • Indirect drain-back systems can be set up in either a vented or hermetic configuration.
  • a vented configuration the reservoir is vented to the atmo ⁇ sphere causing the system to operate at atmospheric pressure.
  • the hermetic configuration the reservoir is sealed with a gas space at the top.
  • the hermetic mode eliminates the need to add make-up heat transfer fluid to the collector loop since no evaporation can occur. Also corrosion is reduced since no air can enter the system. Plain steel surfaces can therefore be used.
  • a hermetic system must, however, be designed to accommodate pressure variations caused by expansion of the fluid in the loop and by the vapor pressure of the fluid.
  • the heat exchanger can be a coil submerged in the drain-back reservoir.
  • a second pump is used to circulate the subject matter to be heated; e.g., potable water, through the heat exchanger.
  • the heat exchanger could be set up to thermosyphon; i.e., to induce fluid flow using the property that hot fluids rise and cold fluids sink.
  • the main advantage of an external heat exchanger is that it can be added to an existing tank.
  • a heat exchange coil which is part of the collector loop and which is submerged within the storage tank is used with an indirect drain-back system.
  • This approach eliminates the need for two pumps and can result in a more compact arrangement.
  • a separate reservoir is located outside the storage tank.
  • the problem with indirect drain-back systems is that they require a separate fluid reservoir and a heat exchanger which can impose thermal performance penal ⁇ ties. With the reservoir separate from the storage tank, heat losses will occur from it. A heat exchanger between the collector loop and storage will cause the collectors to operate hotter than they would without a heat exchanger, reducing efficiency.
  • the foregoing and other problems of prior art solar water heating systems are overcome by the present improved heating system of the type having a heat collector, a heat exchanger, a heat transfer fluid and means for circulating the fluid through the heat collector, where the fluid is heated, to the heat exchanger, where the fluid is cooled, and back to the heat collector.
  • the improvement comprises a heat exchanger in the form of a sealed, hollow, annular jacket for containing a portion of the fluid and a gas which is lighter than the fluid, the jacket having an
  • the circulating means include pump means connected between the outlet of the jacket and the heat collector.
  • a return pipe is communicatively connected between the heat collector and the jacket inlet.
  • the pump means when energized, circulate heat transfer fluid from the jacket outlet to the heat collector and when unenergized, allow the heat transfer fluid flow in the reverse direction.
  • the pump means, the jacket and the return pipe together are capable of containing all of the heat transfer fluid when the pump means are unenergized.
  • the jacket When the jacket .inlet is located below the heat transfer fluid surface in the jacket, the jacket further includes a vent which is positioned above the heat transfer fluid surface and communicatively coupled to a point on the return pipe which is at least as high as the vent.
  • the jacket is positioned about the storage tank and made an integral part of the storage tank, both physically and thermally.
  • the tank jacket forms an annular volume which becomes both the solar fluid reservoir and the heat exchanger.
  • the jacketed tank approach requires a special tank, it is the least complex when compared to existing indirect drain-back systems. It has the advantage of continuous passive thermal coupling between the solar loop water and potable water, thereby making the solar loop fluid an integral part of solar storage. It also makes full use of the tank wall as the heat exchange surface, resulting in material economy. As such, it can be a hermetic system so that plain steel surfaces, for example, can be used.
  • venting configuration includes a dip tube and a containment tube positioned in the solar loop to reduce mixing and heat-transfer-fluid-flashing effects present in the operation of drain back systems.
  • FIG. 1 is a simplified diagram of the present invention.
  • FIG. 2 is a detailed perspective view of the present invention including one embodiment of the vent means.
  • FIG. 3 illustrates an alternative configuration of the vent means.
  • a collector 10 is disposed so that it can absorb solar energy.
  • a storage or water supply tank 12 is located below the level of the collector 10. Disposed about the storage tank 12 is an annular, sealed, hollow jacket 14. The wall of the storage tank 12 and the inner wall of the annular jacket 14 are a common wall. Contained within the annular jacket is a
  • the annular jacket 14 is connected to the collector 10 by a return pipe 20 which is connected between the collector output 22 and the 5 jacket inlet 24.
  • the jacket inlet 24 is positioned toward the top of the jacket.
  • a pump means 26 is connected between the outlet of the jacket 28 and the inlet 30 to the collector.
  • the pump 26 is energized when the col ⁇ lector temperature is higher than the jacket 28
  • the pump draws heat transfer fluid from the bottom of the jacket 1 and circulates the heat transfer fluid into the collector 10. At the collector 10, the heat transfer fluid
  • a vent tube connects the top of the jacket 36 to a point on the return pipe 20 which is at least as high as the top of the fluid level in the jacket. It can also be seen that when the heat transfer fluid 16 is fully drained from the collector 10, the heat transfer fluid level 17 is located at some point below the top of the jacket 14. This permits the gas 18 which fills the space between the heat transfer fluid level in the jacket and the top of the jacket to enter the vent tube 27 and to flow into the return pipe 20 so that the fluid contained within the collector 10 may be drained fully from the collector.
  • the jacket inlet positioning the jacket inlet above the fluid level in the jacket permits the return pipe to serve additionally as a vent.
  • a separate vent above the fluid level should be added.
  • the jacket inlet be posi ⁇ tioned below the fluid level in the jacket and toward the lower portion of the jacket.
  • FIG. 3 An alternative method for venting the gas 18 into the return pipe 20 is shown in Figure 3.
  • the return pipe 20 is connected to the top of the jacket 14.
  • a dip tube 38 is communicatively coupled to the return pipe 20 so that one end of the dip tube extends into the jacket 14.
  • the end of the dip tube extending into the jacket is closed.
  • the dip tube 38 has a vent opening 40 which is located above the heat transfer fluid level 17, and a main opening 42 which is located just above the closed end and below the heat transfer fluid level 17.
  • the vent opening 40 is smaller than the main opening 42, with the vent opening 40 being sized so that there is enough back pressure to keep the
  • a containment tube 44 which extends from the top of the jacket toward the bottom of the jacket contains the dip tube 38.
  • the containment tube 44 is open at its bottom and is sealed to the jacket and around the exterior of the dip tube at its top.
  • the containment tube 44 has a jacket vent 46 which is located above the heat transfer fluid level 17.
  • the heat transfer fluid is pumped from the bottom of the jacket 14, up through the collector 10 and back to the inlet 34 of the jacket.
  • a vent tube 27 connects the gas space at the top of jacket to the return pipe 20 at a point above the top of the jacket. While in operation, unless the flow rate is perfectly balanced, the vent tube 27 will either expell heat transfer fluid into the top of the tank or suck gas into the return pipe 20. Both of these cause mixing which results in destratification of the storage tank and reduced system performance. Expelling water through the vent tube 27 is similar to pumping water from the bottom of the jacket to the top, as in Figure 1.
  • the storage 12 tank is highly stratified (caused by drawing off some hot water from the top and replacing it with cold water at the bottom), and there is a small temperature rise through the collector 10, then hot water at the top will be diluted with colder water. If gas is entrained in the flow within the return pipe 20, gas bubbles will be introduced to the bottom of the jacket and mix the water as they rise to the top. Mixing can also occur on system start up. As the collectors are
  • a vaporizable liquid such as water
  • it can flash to vapor in the collector due to low pressure caused by the fluid column "pulling" on the fluid at the system high point.
  • Large pipes are used to facilitate good drainability, there is therefore only a small pressure drop through the flow loop.
  • Pressure in the collectors can be reduced as much as the height of the fluid column between the collectors and storage tanks. For example, if the collectors are 30 feet above the storage tank, and the jacket is at atmospheric pressure (14.7 psia typical) the pressure in the collectors can be 1.66 psia. Under these conditions, the water would flash at approximately 120°F. Flashing is undersirable for several reasons. It may cause fatigue damage to the collectors and piping, it may partially fill the collectors with vapor which would reduce energy collec ⁇ tion. Entrained vapor bubbles in the downcoming fluid could increase mixing of the storage tank and the noise could be objectionable.
  • the vent opening 40 and the main opening 42 in the dip tube 38 are sized so that there is enough back pressure to keep the water in the collector loop above its vapor pressure so that it will not flash.
  • the size of the openings and the back pres ⁇ sure required depends upon the height of the collectors and the solar loop pressure. If the collectors are high above the storage tank and if the system is at low pressure, more back pressure will be required. Alter ⁇ natively, if the solar loop is pressurized before it is sealed, very little or no back pressure will be needed to keep the heat transfer fluid above its vapor
  • OMPI pressure hence larger openings can be used.
  • less than 5-10 percent of the fluid flow in the return pipe 20 exits through the vent opening 40 above the water line 17 and the rest exits through the main opening 42 below the water line 17.
  • No signifi ⁇ cant amount of mixing can occur since the returning water is contained inside the containment tube 44 and flows at low velocity to the bottom of the jacket 14.
  • any gas which is expelled from the col- lector loop through the dip tube 38 during startup does not disturb the bulk of the water in the jacket since it bubbles up to the top through the containment tube 44.
  • gas is drawn into the piping through the vent opening 40 at " the top of the dip tube 38 allowing the collector loop to drain.
  • the containment tube 44 can be insulated or constructed from insulative material to further isolate the enter ⁇ ing fluid from the fluid already in the jacket 14.
  • the storage tank 12 of the preferred embodiment of the present invention comprises a glass lined steel tank.
  • the jacket 14 is steel.
  • the pump 26 is a high head/low flow rate pump.
  • the heat transfer fluid 16 is plain water.
  • the jacket 14 is partially filled with plain water.
  • the remainder of the jacket and the return pipe 20 are filled with air or an inert gas, such as nitrogen. In a hermetic configuration, air will quickly become inert as the small amount of oxygen is depleted.
  • the pump 26 is deenergized and the water level is roughly 2 or 3 inches from the top of the jacket 14 to allow for thermal expansion of the water.

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

Abstract

Systeme de chauffage solaire d'eau ameliore indirect a drain de retour du type ou on fait circuler un fluide de transfert de chaleur (16) a l'aide d'une pompe (26) depuis un echangeur de chaleur (12, 14), ou le fluide est refroidi, vers un collecteur de chaleur (10), ou le fluide est chauffe, puis retourne a l'echangeur de chaleur, l'amelioration comprenant une double paroi annulaire hermetique (14), un echangeur de chaleur, et une structure de mise a l'event (27, 40, 46) couplee a un reservoir de stockage d'eau chaude (12) qui permet au fluide de transfert d'etre draine et revenir depuis le collecteur de chaleur lorsque la pompe est mise hors de fonctionnement.
PCT/US1982/000444 1981-04-13 1982-04-12 Systeme de chauffage solaire d'eau d'un reservoir a double paroi a drain de retour hermetique WO1982003677A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU84513/82A AU8451382A (en) 1981-04-13 1982-04-12 Jacketed tank hermetic drain-back solar water heating system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US25381881A 1981-04-13 1981-04-13
US253818810413 1981-04-13

Publications (1)

Publication Number Publication Date
WO1982003677A1 true WO1982003677A1 (fr) 1982-10-28

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Family Applications (1)

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PCT/US1982/000444 WO1982003677A1 (fr) 1981-04-13 1982-04-12 Systeme de chauffage solaire d'eau d'un reservoir a double paroi a drain de retour hermetique

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EP (1) EP0076842A1 (fr)
WO (1) WO1982003677A1 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1464588A1 (fr) * 2003-03-28 2004-10-06 Calsonic Kansei Corporation Reservoir d'eau pure pour un système de piles à combustible
ES2332563A1 (es) * 2008-03-18 2010-02-08 Energy Panel, S.L Procedimiento de destilacion de disolvente mediante energia solar termica termodinamica.
WO2010019990A1 (fr) * 2008-08-18 2010-02-25 Renewable Energy Systems Limited Système de collecte d'énergie solaire et système de génération d'énergie comprenant un système de collecte d'énergie solaire
FR2939875A1 (fr) * 2008-12-15 2010-06-18 Electricite De France Installation de chauffe-eau amelioree
EP2388533A1 (fr) 2010-05-21 2011-11-23 Electricité de France Installation de chauffe-eau améliorée
ITMI20111853A1 (it) * 2011-10-12 2013-04-13 Sunwood S R L Centrale termica compatta multienergia per riscaldamento di ambienti e produzione di acqua calda sanitaria.

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2054130A (en) * 1979-07-25 1981-02-11 Sunsense Ltd Improvements in and relating to solar powered heating systems
US4269167A (en) * 1979-12-07 1981-05-26 Embree John M Closed pressurized solar heating system with automatic valveless solar collector drain-back
US4324228A (en) * 1980-08-11 1982-04-13 Paul Shippee Solar heating apparatus
US4326499A (en) * 1979-12-26 1982-04-27 Koskela Marvin O Solar water heating system and heat exchanger therefor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2054130A (en) * 1979-07-25 1981-02-11 Sunsense Ltd Improvements in and relating to solar powered heating systems
US4269167A (en) * 1979-12-07 1981-05-26 Embree John M Closed pressurized solar heating system with automatic valveless solar collector drain-back
US4326499A (en) * 1979-12-26 1982-04-27 Koskela Marvin O Solar water heating system and heat exchanger therefor
US4324228A (en) * 1980-08-11 1982-04-13 Paul Shippee Solar heating apparatus

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ITT Bulletin TESE/576, Copyright 1976 by ITT, "Solar Heating Systems Design Manual", pages 4-8 to 4-15. *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1464588A1 (fr) * 2003-03-28 2004-10-06 Calsonic Kansei Corporation Reservoir d'eau pure pour un système de piles à combustible
US7255243B2 (en) 2003-03-28 2007-08-14 Calsonic Kansei Corporation Pure water tank for fuel cell system
ES2332563A1 (es) * 2008-03-18 2010-02-08 Energy Panel, S.L Procedimiento de destilacion de disolvente mediante energia solar termica termodinamica.
WO2010019990A1 (fr) * 2008-08-18 2010-02-25 Renewable Energy Systems Limited Système de collecte d'énergie solaire et système de génération d'énergie comprenant un système de collecte d'énergie solaire
FR2939875A1 (fr) * 2008-12-15 2010-06-18 Electricite De France Installation de chauffe-eau amelioree
EP2388533A1 (fr) 2010-05-21 2011-11-23 Electricité de France Installation de chauffe-eau améliorée
ITMI20111853A1 (it) * 2011-10-12 2013-04-13 Sunwood S R L Centrale termica compatta multienergia per riscaldamento di ambienti e produzione di acqua calda sanitaria.

Also Published As

Publication number Publication date
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