Abstract:
This invention relates to a heating/cooling system operating on the basis of a novel SPLIT BUFFER TANK; representing an efficiency improvement alternative to HVAC systems functioning with existing commercial buffer tanks. Currently, commercial buffers have the heat source provider (HSP)-return and system-return discharging to a common buffer/vessel. Novel SPLIT BUFFER is provided with a SEPARATION DISK placed inside the tank as mechanical way of separating the hot water inflow from the HSP from the warmer water inflow from system return. The disk moves up and down along the tank driven by demanded water supply and return. Pump- 1  circulates hot water from the hot section of the buffer to the secondary system claiming for heat. Pump- 2  circulates warmer water from the warmer section of the buffer through the HSP where it is reheated, and subsequently stored in the hot section of the buffer to reinitiate this cycle again.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to a heating/cooling system featuring a buffer tank, and more particularly to such a system employing a split buffer tank configured to separate hot heat source provider flow return from warm secondary system flow return. 
       BACKGROUND OF THE INVENTION 
       [0002]    To better illustrate the nature of the invention, take for instance the case of a condensing boiler as a heat source provider (HSP). It is common to find all variety of brands and models operating at steady-state-efficiency levels from 70-80% for non-condensing to 82-98% for condensing. Steady-state Efficiency—refers to a measuring parameter for boiler maximum efficiency capability assessed under a controlled steady test and carried out by recognizable standard certification bureau. In the test, parameters such as air-intake temperature and volume, air/gas mixture, water/brine temperature/flow entering/leavening the boiler, system heat demand, and some others, are all fixed during boiler firing to obtain a better judgment of its efficiency at artificial steady state conditions. Test Standards for Gas-Fired Boilers. CGA P.2-1991 (R1999)/ENERGY START Canada, and the U.S. Department of Energy&#39;s/Title 10/Code of Federal Regulations for the Energy Conservation Program for Consumer Products, make indications that during the steady state testing of a condensing boiler water outlet temperature shall be at 180° F./82° C. and inlet temperature shall be at 80° F./26.7° C. at all times. 
         [0003]    Drifting away from the stationary conditions dictated by the test, it arrives at the real world, a different place. A world loaded with always changing conditions where lab subsets are not so frequently encountered during the operating life span of the boiler. To complicate matters, there appears the need for adding buffer capacity in order to eliminate problems associated with excessive cycling, poor temperature control, and erratic system operation. The HVAC industry learned a long time ago that it was by adding a buffer tank to the boiler-system that they resolved all these problems. However, one issue remains unsolved. That is, the loss of the boiler high efficiency during continuous operation due to the water mixing inside the tank. But with no solution on hand, they were forced to look the other way. 
         [0004]    In today&#39;s commercial buffers (See  FIG. 2 ), boiler water-return at temperature t b  and secondary system water-return at temperature t s  easily get mixed in the buffer because of the lack of mechanical medium capable of isolating the encountering of the two flows inside the tank (See also  FIG. 4 ). This mixed water at temperature equal t mix  when going to the boiler produces the same effect on efficiency behavior as the one depicted in  FIG. 3 . There, and independent study (by Jim Cooke) shows how condensing and non-condensing boilers thermal efficiency gets influenced by water return temperature during steady-state conditions. Cooke&#39;s study also shows thermal efficiency behavior for a condensing boiler at three different firing rates (33/67/100%). 
         [0005]      FIG. 4  shows some water/brine supply/return hydraulic connections for some brand name buffer tanks and their prevailing flow pattern when all intakes/outlets are in used. Water/brine motion inside the buffer not only gets affected by physical characteristics of the system such as pumps flow, buffer diameter and height, inlet/outlet configuration, among other variables, but also by changing set of dynamic conditions regulated by DCS (Distributed Control System). Flow patterns in the buffer are chaotic and unpredictable with limited opportunities for creating stratification conditions. For this to occur pumped flow coming from HSP/boiler and/or secondary system need to be slowed down to such extent that entering speed must be close to laminar flow. Only such minimal disturbance in the body of water inside the tank will have no major mixing effect in the natural convection phenomenon associated with stratification. From a design stand point this may lead to uneconomical alternatives such as having a much bigger diameter for piping inlet/outlet connections, otherwise designed with acceptable velocity of 2.1±0.9 m/s (7±3 ft/s) for normal liquid service applications, with maximum velocity of 2.1 m/s (7 ft/s) at piping discharge points. Perhaps even requiring a buffer tank with oversize uneconomical dimensions in diameter and/or height. This, without mentioning the time factor to allow the stratification process to evolve and settled in a constant demand HVAC system. 
         [0006]    The more realistic assumption is that any flow leaving the buffer will do so at a temperature t mix . 
         [0007]    From  FIG. 2  and  FIG. 4  it may be concluded that: 
         [0000]        t   mix =( t   b   +t   s )/2       t b  Water/brine temperature at boiler outlet. Considered equal to t 1  (See  FIG. 1 ) when no heat losses occur in pipe connection between boiler and buffer   t s  Water/brine temperature at system return. Considered equal to t 2  (See  FIG. 1 ) when no heat losses occur in pipe connection between system and buffer   t mix  Water/brine temperature from the mixture of warm and hot water if there is no separation disk (as it happens in existing commercial buffers). Water temperature going to the boiler   t 1  Water temperature from hot section of the buffer to the secondary system   t 2  Water temperature from Secondary System to warm section of the buffer   t 1 -t 2  Delta temperature. Q=W×C p ×(t 2 −t 1 )   Q Secondary system heat demand. Q=W×C p ×(t 2 −t 1 )         
         [0015]    Using data results from chart on  FIG. 3  and applying the same analogy to evaluate water return/supply configuration on boiler efficiency for the typical commercial buffer connections on  FIG. 4 ; It may be proven that when water gets mixed in the buffer and returned to the boiler at mixed temperature t mix , it will produce the same effect on the thermal efficiency of the boiler. As flow pattern and temperature of the mix evolve over time, the rising temperature of the water/brine will increasingly hamper its ability to quickly regain thermal energy when recirculating through the boiler, resulting in longer less efficient runs with increasingly unnecessary consumption of energy resources (See  FIG. 6 ). This in turn will force chimney gases to escape the boiler without fully rendering their caloric load. 
         [0016]    When dealing with condensing boilers it is crucial to realize that continuous 80° F./26.7° C. water-return and below is the determinant factor in achieving continuous outstanding higher efficiencies (See chart on  FIG. 3 ); and that, boilers serving a buffer/system in which mixed water return temperature does not fall below 80° F./26.7° C. will never meet the necessary temperature requirements for achieving such continuous performance. Ignoring this fact, when justifying a boiler selection, will result in having a boiler that cost 50% more than necessary (comparing to condensing boiler) and achieves, from time to time, just above condensing boiler performance. 
         [0017]    Currently buffer technology has not corrected the problems created with usual configurations such as the one on  FIG. 4  (and the like); and as a result, its usage just exacerbate the sub-utilization of condensing boilers in boiler/buffer/systems that ONLY occasionally allow condensation to occur. 
       SUMMARY OF THE INVENTION 
       [0018]    According to a first aspect of the invention there is provided a heating/cooling system operating on the basis of a novel split buffer tank comprising a separations disk, a guide bar adapted inside the split buffer tank to freely allow the separation disk to move up and down along the guide bar to make room for hot and warm fluid storage on opposite sides of the disk, two disk flow bypasses for respective loop flow functionality between the split buffer tank and each of a heat source provider and a secondary system, and hydraulic connections to interconnect the heat source provider and the secondary system to the split buffer tank. 
         [0019]    Preferably the heat source provider is hydraulically connected to the split buffer tank. 
         [0020]    Preferably the secondary system ( 14 ) is hydraulically connected to the split buffer tank. 
         [0021]    Preferably buffer heat source provider return line serves as hydraulic connection to convey hot fluid from the heat source provider into a hot section of the split buffer tank on a hot side of the disk. 
         [0022]    Preferably a buffer heat source provider supply line serves as hydraulic connection to convey warm fluid from a warm section of the split buffer tank on a warm side of the disk to the heat source provider. 
         [0023]    Preferably a buffer system supply line serves as hydraulic connection to convey hot fluid from a hot section of the split buffer tank on a hot side of the disk to the secondary system. 
         [0024]    Preferably a buffer system return line serves as hydraulic connection to convey warm fluid from the secondary system to a warm section of the split buffer tank on a warm side of the disk. 
         [0025]    Preferably the split buffer tank ( 1 ) comprises the following:
       (a) a hot-outlet hydraulically connected to a buffer system supply line to convey stored hot fluid from the split buffer tank to the secondary system to satisfy demand for heat;   (b) a warm-inlet hydraulically connected to a buffer system return line to convey secondary system return warm fluid to split buffer tank for storage;   (c) a hot-inlet hydraulically connected to a buffer heat source provider return line to convey hot fluid from the heat source provider to the split buffer tank for storage;   (d) a warm-outlet hydraulically connected to a buffer heat source provider supply line to convey stored warm fluid from the split buffer tank to the heat source provider for reheating;   (e) the separation disk, which functions to hydraulically separate hot fluid inflow from the heat source provider from warm fluid inflow from the secondary system, and to serve as an insulating wall for thermal separation between hot and warm sections of the tank, the separation disk comprising the following:
           i) an insulating core which functions to thermally insulate the hot section of the split buffer tank from the warm section;   ii) a separation disk warm-side bypass to allow a pump- 1  to recirculate fluid in a system loop during positioning of the disk in a top position;   iii) a separation disk hot-side bypass to allow pump- 2  to recirculate fluid in a heat source provider loop during positioning of the disk in a bottom position; and   iv) a pressure release check valve hydraulically connecting a hot face of the disk with a warm face of the disk in order to eliminate pressure differential between the hot and warm sections of the tank that may arise from a make-up fluid connection on the split buffer tank;   
           f) the guide bar, which is a center guide squared bar to guide the separation disk up and down along the split buffer tank and to prevent rotation of the disk from causing misalignment of the warm-side bypass with the hot outlet ( 8 ), or the hot-side bypass with the warm outlet ( 11 ), at an edge of the separation disk, the disk being displaceable up and down along the center guide bar to allow hot and warm fluid accumulation during thermal recharging and discharging of the split buffer tank;   g) a separation disk hub to secure the separation disk to the center guide bar and to accommodate a set of counterweight plates;   h) the set of counterweight plates balancing buoyancy of the separation disk to make the separation disk effectively weightless when placed in the fluid medium inside the split buffer tank;   i) a top position disk stopper to limit displacement of the disk when going to the top position lining up the warm-side bypass with the hot outlet;   j) a bottom position disk stopper to limit displacement of the disk when going to the bottom position, lining up the hot side bypass with the warm outlet;   k) a guide bar attachment to mechanically secure the guide bar to a bottom of the split buffer tank; and   l) a pressurized fluid make-up &amp; air vent connection to maintain continuous fluid supply to the system and to allow for allocation of air vent equipment in association with the split buffer tank.       
 
         [0042]    Preferably there is provided a Distributed Control System (DCS) logic that is arranged to work independently or in conjunction with additional DCS controllers and comprises the following:
       a) a demand-based sensor/selector inside the Secondary System perimeter which functions to monitor an inner temperature and call for heat, starting a Pump- 1  operable between the buffer tank and the secondary system, if the inner temperature falls below a preset value;   b) a fluid temperature sensor/selector located at a buffer system supply line, between a hot outlet of the buffer tank and the pump- 1 , the temperature sensor/selector registering a first point fluid temperature, operating only when the pump- 1  is ON, and if the first point fluid temperature falls below a set point, signaling to start first a pump- 2  operable between the buffer tank and the heat source provider and, with a time delay, start the heat source provider to reload the split buffer tank with hot fluid; and   c) another fluid temperature sensor/selector located at a buffer heat source provider supply line, between a buffer tank warm outlet and pump- 2  to register a second point fluid temperature and shut-off the pump- 2 , and with time delay, shut off the heat source provider if the second point fluid temperature rises to a second preset value.       
 
         [0046]    The split buffer tank is preferably insulated to retain heat, provided with medium to high pressure capabilities and suitable to operate at higher than normal temperatures. 
         [0047]    The heat source provider may feature any direct heating device such as gas/oil boiler, heat pump, solar plant (solid fuel), wood pellet/log and/or any district heating, or indirect heating device operated via integrated heat exchangers or external flat plate heat exchanger. 
         [0048]    The secondary system may feature any HVAC applications for office buildings, industrial facility or any other closed environment, where safe and healthy building conditions are regulated with temperature and humidity, as well as “fresh air” from outdoors. Also any industrial thermal processes involving cooling/heating applications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0049]    In the following drawings, which illustrate the exemplary embodiments of the present invention: 
           [0050]      FIG. 1  schematically illustrates a heating/cooling system operating with the novel invention of a split buffer tank 
           [0051]      FIG. 2  schematically illustrates a prior art boiler/system operating with an existing commercial buffer tank 
           [0052]      FIG. 3  shows a simplified chart for condensing and non-condensing boilers steady-state thermal efficiency as function of return water temperature 
           [0053]      FIG. 4  schematically illustrates prior art water/brine supply/return hydraulic connections for some commercial buffer tanks showing prevailing flow patterns. 
           [0054]      FIG. 5  shows boiler/buffer/system connections effect on time thermal efficiency 
           [0055]      FIG. 6  shows split buffer Vs commercial buffer connection effect on energy savings 
           [0056]      FIG. 7   a  schematically illustrates a commercial buffer tank connection for a geothermal heat pump. 
           [0057]      FIG. 7   b  schematically illustrates a split buffer tank connection for a geothermal heat pump 
           [0058]      FIG. 8  shows geothermal heat pump/buffer/system connection effect on energy savings 
           [0059]      FIG. 9  is a cross-sectional view of a split buffer/separation disk operating at a top position 
           [0060]      FIG. 10  is a cross-sectional view of the split buffer/separation disk operating at a bottom position 
           [0061]      FIG. 11  is a plan view of the separation disk 
           [0062]      FIG. 12  shows separation disk hub details, including cross-sectional view A-A with details on counterweight plates and a pressure release check valve. Separation ring insulating core ( 2   a  in  FIGS. 9 &amp; 10 ) is not shown, to simplify the drawings. 
       
    
    
     DETAILED DESCRIPTION 
     1. General Character of the invention 
       [0063]    The present invention relates to a heating/cooling system operating on the basis of a SPLIT BUFFER TANK, as shown in  FIG. 1 . Its design includes a mechanical disk ( 2 ) in order to separate the hot HSP flow return ( 19 ) from the warm secondary system flow return ( 15 ). Because both sections get thermally and hydraulically isolated one from each other, it favours the separation of the two bodies of water with different thermal properties. This in turn, allows the independent supply of water/brine to the secondary system at a steady high temperature serving the demand for heat, and steady low water/brine temperature to the HSP for reheating. Since steady state conditions for both flows are possible with this new invention, its use will maximize thermal operating efficiency for existing large sets of manufactured HVAC equipment. It alone will allow not only the step down on equipment sizes for a given set of thermal conditions, but also the decrease in the use of non-renewable natural resources and in the otherwise normally increasing maintenance costs. The HSP and the Secondary System work in a closed loop interconnected through the buffer/vessel. The term “water” or “brine” will be used indistinctively, meaning the fluid used within this closed loop. The name “System” is used herein to refer to the Secondary System, not the overall heating/cooling system. 
       2. Inventive Idea 
       [0064]    In the case of the split buffer of the present invention (refer to  FIG. 1 ), boiler water-return at temperature t b  will never encounter system water-return at temperature t s . Therefore, a constant flow of water to the boiler at t 2  will remain unchanged throughout the heat-loading operation, allowing the boiler to perform at very stable conditions closely mimicking lab subsets. With boiler operating at continuous high efficiency levels, buffer reloading will be carried out in shorter periods with saving in non-renewable energy resources, and time operation will be minimized, reducing boiler wearing and operational costs. On the system side, because now water/brine to the system can be delivered at continuous targeted high temperature, system HVAC equipment will see a significant improvement in their thermal transfer units (because of higher log median temperature differential, or LMTD). This alone will favor downsizing when considering the use of split buffer during the initial phase of HVAC system design. 
         [0065]    Additional desirable key features can be added to the system that now can operate at continuous buffer system delivery targeted temperature and work with much lower water return temperature to the boiler. For example, less volume of water/brine will be needed to be pumped in order to be capable of carrying a bigger load to the system, smaller piping diameter with reduced pressure drops can be used, smaller handling systems with reduced heat exchangers can be used, and it would make sense to put effort in designing a system with water return temperature as low as possible since its purpose will not be defeated by buffer mixing. And lastly, it would be expected to have a smaller required boiler capacity more responsive to system loads and less costly to operate. 
         [0066]      FIG. 5  shows the hypothetical effect of boiler/buffer connection configuration on thermal efficiency for the three scenarios considered in  FIG. 4  with some additional considerations. The same boiler with best/middle/worst connections arrangement now working in a time evolving water mixing situation where the slope in the chart will indicates the speed of change by which thermal efficiency drops down for a given best/middle/worst case scenario. The dashed line at 120 seconds marks the time at which such boiler will finish thermal loading when operating with a novel split buffer (280 seconds when operating with commercial buffer). It can be observed that the split buffer operation provides an advantage when compare to commercial buffers. The elimination of water return mixing allows it to consistently perform (at 98% efficiency) enabling thermal reloading in shorter boiler time operation, see  FIG. 6  (with lower energy resource spending, more rapid system response and less mechanical maintenance cost on the boiler). 
         [0067]    In the case of a water-to-water geothermal heat pump (GHP) (see  FIG. 7   a ,  7   b ), operating with any commercial buffers from  FIG. 4 , GHP brine return at temperature t b  and system brine return at temperature t s ; again, easily get mixed in the buffer because of the lack of mechanical medium capable of isolating the encountering of the two flows inside the tank. This mixed water at temperature equal t mix =(t b +t s )/2 when going to the GHP condenser or evaporator (depending on whether the GHP is in a heating mode—like that shown in  FIG. 7   a , or a cooling mode) will produce an LMTD much lower than the one generated when operating with the split buffer ( 1 ), with no mix ( FIG. 7   b ). LMTD reduction will hamper the ability of the brine to quickly regain thermal energy and transport a higher load to the buffer in a shorter period of time; resulting, in longer GHP runs with increasing consumption of energy and equipment wearing. During buffer thermal loading operation, as t mix  approaches t b , LMTD tends to zero making the heating transferring process to become more critical. At this time, the rate of heat transfer via condenser/evaporator to the GHP brine will approximate slowly to zero, forcing the GHP to operate for a longer period time until t mix =t b  at time t 10  (See chart on  FIG. 8 ), and the system shuts-off. 
         [0068]    Split buffer ( 1 ) offers operational advantages to GHP due to the ability to maintain a constant flow of low water temperature (high water temperature during reverse cycle) going to the GHP evaporator accelerating heating-loading time. The results, a more efficient GHP operation with lower running time, less energy consumption and lower maintenance cost. Special consideration should be given to Split Buffer ( 1 ) Distributed Control System which now needs to be reconditioned in order to perform not only on heating but cooling reverse cycle. 
         [0069]    Similar analysis may be carried out for other Heat Source Providers (HSP) as part of any HVAC system with the same positive improvement in their operation. 
       2.1. Sequence of Operation 
       [0070]    Heating/cooling cycle for the system in  FIG. 1  initiate with demand-based sensor/selector inside secondary system perimeter TS 0  ( 22 ) sensing the need for heat and sending a signal to start pump- 1  ( 13 ). At this moment in time, secondary system ( 14 ) temperature is below TS 0  ( 22 ) set point. 
         [0071]    With Pump- 1  ( 13 ) running and water/brine flowing from split buffer ( 1 ) to secondary system ( 14 ), low temperature sensor/selector TS 1  ( 23 ) located at buffer hot outlet ( 8 ) registers point water temperature. If water/brine temperature is above set point, there will be no signal to start pump- 2  ( 17 ) and HSP/boiler ( 18 ). Split buffer ( 1 )/pump- 1  ( 13 ) will continue supplying hot water and pushing separation disk ( 2 ) toward the top position of the split buffer tank ( 1 ) shown in  FIG. 9  until a warm-side bypass ( 3   a ) of the separation disk ( 2 ) gets aligned with hot outlet ( 8 ) of the buffer tank ( 1 ). At that point, pump- 1  ( 13 ) will recirculate warm water along system loop “split buffer ( 1 )→buffer system supply line ( 12 )→secondary system ( 14 )→buffer system return line ( 15 )→split buffer ( 1 )” via the warm side bypass ( 3   a ) until any excess heat remaining in the water is released into the secondary system ( 14 ) and TS 1  ( 23 ) registers a water temperature falling below set point. TS 1  ( 23 ) will then triggers on pump- 2  ( 17 ), and with time delay, HSP/boiler ( 18 ). Pump- 1  ( 13 ) will run continuously until secondary system ( 14 ) temperature reaches TS 0  ( 22 ) set point indicating that the demand for heat is mitigated. 
         [0072]    Once demand in secondary system ( 14 ) gets satisfied, TS 0  ( 22 ) will shut off pump- 1  ( 13 ). HSP/boiler ( 18 )/pump- 2  ( 17 ) will continue running/loading split buffer ( 1 ) with hot water/brine until separation disk ( 2 ) reaches the bottom position of the split buffer tank ( 1 ) shown in  FIG. 10 , aligning a hot-side bypass ( 3   b ) of the separation disk ( 2 ) with buffer warm-outlet ( 11 ) of the buffer tank ( 1 ). At that point, pump- 2  ( 17 ) will continue recirculating water along the HSP/boiler loop “split buffer ( 1 )→buffer HSP/boiler supply line ( 16 )→HSP/boiler ( 18 )→buffer HSP/boiler return line ( 19 )→split buffer ( 1 )” via the hot side bypass ( 3   b ) until water/brine temperature reaches high temperature sensor TS 2  ( 24 ) set point, dictated by the outdoor reset control ORC ( 28 ). TS 2  ( 24 ) then will shut-off HSP/boiler ( 18 ), and with time delay, pump- 2  ( 17 ). This will leave split buffer ( 1 ) thermally loaded and resting for the next cycle. 
         [0073]    When running concurrently, pump- 1  ( 13 ) and pump- 2  ( 17 ) will create an operational valet on the separation disk ( 2 ) that now moves up and down inside the split buffer, obeying HSP/boiler ( 18 ) and secondary system ( 14 ) water flow demand and return. Both served by pump- 1  ( 13 ) and pump- 2  ( 17 ). Pump- 1  ( 13 ) and pump- 2  ( 17 ) operate concurrently with no discharge counterpressure (other than loop pressure losses) that forces any of the pumps to fight. Pump- 1  ( 13 ) is always discharging in the suction section of pump- 2  ( 17 ) and vice versa. 
         [0074]    Low temperature sensor/selector TS 1  ( 23 ) will operate only when pump- 1  ( 13 ) is on. This prevents pump- 2  ( 17 ) and HSP/boiler ( 18 ) from operating when supply line ( 12 ) gets cold and the secondary system is not calling for heat. 
         [0075]    Split buffer ( 1 ) thermal reloading cycle will not only be initiated by a new demand for heat for secondary system ( 14 ); but also, by additional high temperature sensor (TS 3 ) ( 25 ), added to split buffer ( 1 ) to maintain a high water/brine temperature during long resting periods. It should be used only if additional extra time for secondary system recovery is not allowed by the HVAC system. High temperature set point for TS 3  ( 25 ) is dictated by the outdoor reset control ORC ( 28 ). 
         [0076]    Outdoor reset control ORC ( 28 ), is a commonly used microprocessor-based control designated to regulate supply water/brine temperature based on outdoor temperature. Automatic reset ratio calculation sets the relationship between outdoor temperature and supply water/brine temperature (heating curve) to provide optimum control and comfort. As the outdoor temperature changes, the control adjusts firing rate of the boiler or running time to compensate for exterior heat loss. 
         [0077]    ORC ( 28 ) will automated high temperature set point for TS 2  ( 24 ) and (TS 3 ) ( 25 ). And because it matches heat loss from the secondary system with HSP/boiler required output, it will optimize energy conservation in a system that will operate at the lowest practical return water temperature. 
       2.2. Operation Notes 
       [0078]    Bypass connection ( 3   a ) and ( 3   b ) in the separation disk ( 2 ) (as it is shown in  FIG. 9 ,  10 ,  11 ) allow pumps to bypass flow during top or bottom disk positions. During top position ( FIG. 9 ), with pump- 1  ( 13 ) running, warm-side bypass ( 3   a ) will line up with hot outlet ( 8 ) allowing water/brine to freely recirculate along system loop. Once low temperature sensor TS 1  ( 23 ) registers recirculating water/brine temperature being below set point, it will start pump- 2 ( 17 ), and with time delay HSP/boiler ( 18 ), to reinitiate thermal loading. During bottom position ( FIG. 10 ) with pump- 2  ( 17 ) running, hot-side bypass ( 3   b ) will line up with warm outlet ( 11 ) allowing hot water/brine to freely recirculate along HSP/boiler loop. Once high temperature sensor TS 2  ( 24 ) registers recirculating water/brine temperature being on target, it will shut-off thermal reloading sending the system to a temporary rest. Both loops operate independently and complementing one another. 
         [0079]    Top position disk stopper ( 26 ) and bottom position disk stopper ( 27 ) will limit the separation disk run along guide bar ( 7 ). During disk top position (see  FIG. 9 ), it allows disk warm-side bypass ( 3   a ) to line up with hot outlet ( 8 ). During disk bottom position (see  FIG. 10 ), it allows disk hot-side bypass ( 3   b ) to line up with warm outlet ( 11 ). 
         [0080]    Each bypass curves through ninety degrees, first extending axially into the disk just inward from its circular cylindrical periphery and then turning through ninety degrees to extend radially out of the disk through the disks peripheral edge, which otherwise seals to the internal cylindrical surface of the tank&#39;s peripheral wall closing concentrically around the guide bar  7 . The radially opening end of the bypass communicates with the respective one of the supply lines ( 12 ,  16 ) when one side of the disc, specifically the side of the disk opposite the other end of the bypass, seats against the respective stopper ( 26 ,  27 ). This seating or stopping of the disc acts to block further sliding of the disk along the guide bar. The warm side bypass ( 3   a ) extends into the bottom face of the disk so as to fluidly communicate only with the warm water or brine and buffer warm inlet ( 9 ) below the disk, while the hot side bypass ( 3   b ) extends into the top face of the disk so as to fluidly communicate with the hot water or brine and buffer hot inlet ( 10 ) above the disk. 
         [0081]    The guide bar ( 7 ) is illustrated as centrally positioned in the buffer tank and as having a square cross-section closely fitting in a similarly sized passage of square section extending through the hub of the disk so that a sliding seal is formed between the hub and the guide bar to prevent water or brine from crossing the disk from on side thereof to the other through the hub, while allowing sliding of the disk along the guide bar. The straight-sides of the square cross-sections of the tube and hub passage cooperate to prevent relative rotation between the two, thereby maintaining the bypass passages in the disk in the same radial planes of the tank and bar longitudinal axes as the respective outlets of the tank. It will be appreciated that other non-circular cross-sectional shapes can be used to establish such rotation-preventing cooperation between the disk and the guide bar. The guide bar and disk also cooperate to substantially maintain the orientation of the disk&#39;s plane relative to the bar&#39;s longitudinal axis to thereby keep the outer periphery of the disk near the inner periphery of the tank and thus minimize fluid leakage and mixing across the disc. 
         [0082]    Because separation disk ( 2 ) and the insulating manufacturing material injected in the core ( 2   a ) of the disk will vary in density when compared to water/brine or any other liquid being used, weight balancing is carried out through a set of counterweight plates positioned in a hub ( 6 ) of the disk (as seen in  FIG. 12 ) in order to counterbalance the buoyancy effect of the disk. The purpose is to make the disk as neutrally buoyant or effectively weightless as possible when placed inside the tank (Buoyant force−counterweight=0), eliminating its tendency to float to the top or sink to bottom position. This may happen when the system is resting for long period of time. In any case, split buffer will maintain its operability due to the configuration in hydraulic connections ( 12 ), ( 15 ), ( 16 ), ( 19 ) and to DCS instructions that maintains the appropriate sequence of operation at any disk position. 
         [0083]    Separation disk is provided with pressure release check valve ( 5 ) (See  FIG. 12 ) to balance any pressure differential that may arise from make-up water/brine feeding through the make-up/air vent connection line ( 20 ) (see  FIG. 1 ,  9 ,  10 ). Pressure release check valve ( 5 ) allows forward flow from hot section atop to the warm section in the bottom and closes to block reverse flow. This allows achievement of a pressure balance across the disc, thereby preventing the disk from sinking when the system is resting. 
         [0084]    Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.