Patent Publication Number: US-2013233510-A1

Title: Liquid heating system

Description:
This invention is in the field of liquid heating equipment, and in particular a system for heating varying volumes of liquid to selected temperatures. 
     BACKGROUND 
     In many industries a supply of hot water or other hot liquid is required for an operation on temporary basis. For example in some hydraulic fracturing operations on underground petroleum formations, large volumes of hot liquid comprising water mixed with various other products such as hydrocarbons, proppants and other additives are pumped down a well bore as part of the fracturing process. A continuous flow of liquid at a selected temperature for a period of time is required. The amount of liquid needed, and the selected temperature can vary from one situation to the next. Providing portable equipment that can be readily adapted to heat the required varying flow volumes of liquid to the varying selected temperatures is problematic. 
     Water from streams or ponds is often used, and this water often contains particulate matter which leaves sludge and contamination in the equipment used to heat the water. In some industries such contamination from one site must be cleaned out of the equipment so same is not transported to contaminate the next site. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a liquid heating system that overcomes problems in the prior art. 
     In a first embodiment the present invention provides a liquid heating system comprising a plurality of heat exchangers including a first heat exchanger, a final heat exchanger, and a plurality of middle heat exchangers. Each heat exchanger comprises a right heating chamber having a right input port and a right output port, and a left heating chamber having a left input port and a left output port. A heating circuit is connected to a source of heated supply fluid, and is configured such that circulating heated supply fluid through the heating circuit heats target liquid present in the right and left heating chambers. The right and left heating chambers are connected such that target liquid to be heated flows into the right input port of the right heating chamber of the first heat exchanger and through each right heating chamber to the left heating chamber of the final heat exchanger, and then through each left heating chamber and through the left output port of the first heat exchanger to a hot liquid discharge. 
     In a second embodiment the present invention provides a liquid heating system comprising a plurality of heat exchangers including a first heat exchanger, a final heat exchanger, and a plurality of middle heat exchangers. Each heat exchanger comprises a right heating chamber having a right input port and a right output port, and a left heating chamber having a left input port and a left output port. A heating circuit is connected to a source of heated supply fluid, and is configured such that circulating heated supply fluid through the heating circuit heats liquid present in the right and left heating chambers. The right input port of the first heat exchanger is connected to a source of target liquid to be heated, and the right output port of each of the first and middle heat exchangers is connected to the right input port of a next successive heat exchanger. The right input port of the final heat exchanger is connected to the right output port of a prior middle heat exchanger, and the right output port of the final heat exchanger is connected to the left input port of the final heat exchanger. The left output port of each of the final and middle heat exchangers is connected to the left input port of a next successive heat exchanger. The left input port of the first heat exchanger is connected to the left output port of a prior middle heat exchanger, and the left output port of the first heat exchanger is connected to a hot liquid discharge. 
     In a third embodiment the present invention provides a heat exchanger comprising an outer wall and end walls forming an enclosure. An inner dividing wall extends across the enclosure to form right and left heating chambers, the right heating chamber having a right input port and a right output port, and the left heating chamber having a left input port and a left output port. A heating circuit is adapted to be connected to a source of heated supply fluid and configured such that during operation heated supply fluid circulates through the outer wall and the inner dividing wall, and configured such that circulating heated supply fluid through the heating circuit heats liquid present in the right and left heating chambers. 
     The heat exchanger can be mounted with a fluid heating apparatus on a heating module that is portable and easily transported. The fluid heating apparatus can be a substantially self-contained combustion type fluid heater that can operate in a remote work site. In the system of the present invention each heat exchanger and fluid heating apparatus adds about the same amount of energy and temperature rise to the target liquid, and so operates efficiently, and minimizes the number of heating modules required. 
     The number of heating modules required can be calculated and portable equipment that can be readily adapted to heat the required varying flow volumes of water to the varying selected temperatures can be transported to the work site. 
     The heating chamber of the heat exchangers are open, without cross conduits or the like, and so can be cleaned of foreign material by providing closable cleaning apertures in each heating chamber. 
     In a fourth embodiment the present invention provides a heat exchanger apparatus comprising a heating chamber with an input port and an output port. A water jacket substantially encloses the heating chamber, the water jacket having a supply end extending substantially along a length of the heating chamber, and a return end extending substantially along a length of the heating chamber. A supply manifold extends along substantially a length of the supply end of the water jacket, the supply manifold defining a supply port adapted for connection to receive supply fluid from a circulating fluid heater, and a plurality of supply apertures along a length thereof connecting an interior of the supply manifold to an interior of the water jacket. A return manifold extends along substantially a length of the return end of the water jacket, the return manifold defining a return port adapted for connection to return supply fluid to the circulating fluid heater and a plurality of return apertures along a length thereof connecting an interior of the return manifold to the interior of the water jacket. A size of the supply apertures is selected such that a flow of supply fluid entering the supply port is restricted and such that resulting pressure in the supply manifold causes the supply fluid to flow along the length of the supply manifold and out through each supply aperture in the supply manifold, then through the interior of the water jacket around the heating chamber through a return aperture in the return manifold into the return manifold and through the return port. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       While the invention is claimed in the concluding portions hereof, preferred embodiments are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where: 
         FIG. 1  is a top view of an embodiment of a liquid heating system of the present invention; 
         FIG. 2  is a front view of the embodiment of  FIG. 1 ; 
         FIG. 3  is a schematic sectional front view of a heat exchanger of the embodiment of  FIG. 1 ; 
         FIG. 4  is a schematic sectional end view of the heat exchanger illustrated in  FIG. 3 ; 
         FIG. 5  is an end view of a heating module of the embodiment of  FIG. 1  including the heat exchanger of  FIG. 3  and a fluid heating apparatus; 
         FIG. 6  is a schematic illustration of the operation of a heating system of the prior art; 
         FIG. 7  is a schematic sectional view of a heat exchanger apparatus with a single heating chamber; 
         FIG. 8  is a schematic side view of the heat exchanger apparatus of  FIG. 7 ; 
         FIG. 9  is a schematic view of the manifolds and water jacket of the heat exchanger apparatus of  FIG. 7 ; 
         FIG. 10  is a schematic view of the manifolds and water jacket of a heat exchanger apparatus of the prior art. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
       FIGS. 1 and 2  illustrate an embodiment of a liquid heating system  1  of the present invention. The liquid heating system  1  comprises a plurality of heat exchangers  3  including a first heat exchanger  3 A, a final heat exchanger  3 B, and a plurality of middle heat exchangers  3 C. The heat exchanger  3  is schematically illustrated in  FIGS. 3 and 4 . 
     Each heat exchanger  3  comprises a right heating chamber  5  having a right input port  5 A and a right output port  5 B, and a left heating chamber  7  having a left input port  7 A and a left output port  7 B. The volume of the right heating chamber  5  is substantially equal to the volume of the left heating chamber  7 . 
     The right and left input ports  5 A,  7 A are located in lower portions of the corresponding right and left heating chambers  5 ,  7  and the right and left output ports  5 B,  7 B are located in upper portions of the corresponding right and left heating chambers  5 ,  7 . Thus cooler liquid enters the input ports  5 A,  7 A at the bottom of the chamber where same is heated as it passes through the chamber to the output ports  5 B,  7 B located at the top of the opposite end of the chamber. The hottest liquid in the chamber will be at the top of the chamber and thus will flow out of the output ports  5 B,  7 B. 
     The terms “right” and “left” are used for convenience of reference only to differentiate the heating chambers for the purposes of the present description. 
     A heating circuit  9  is connected to a source of heated supply fluid, and is configured such that circulating heated supply fluid  11  through the heating circuit  9  heats liquid present in the right and left heating chambers  5 ,  7 . In the illustrated system  1 , each heat exchanger is mounted on a heating module  13 , illustrated in  FIG. 5 , that includes a fluid heating apparatus  15  operative to provide the source of heated supply fluid. The heating module  13  is portable and easily moved from one job site to the next, and includes any pumps, fuel tanks, electrical power systems, and the like necessary to operate, control, and circulate the heated supply fluid  11  through the fluid heating apparatus  15  and the heat exchanger  3 . The fluid heating apparatus  15  is typically provided by a substantially self-contained combustion type fluid heater that does not require external electrical power and so can be conveniently set up and operated at a remote work site. 
     The illustrated heat exchanger  3  includes an outer wall  17  and end walls  19  forming an enclosure, and an inner dividing wall  23  extending across the enclosure to form the right and left heating chambers  5 ,  7 , and the heating circuit  9  is configured such that heated supply fluid  11  circulates through the outer wall  17  and the inner dividing wall  23 . The illustrated heating circuit  9  includes a supply input line  25  connected to a supply manifold  27  that distributes the heated supply fluid  11  along a length of the heat exchanger  3  through manifold holes  29 . The heated supply fluid  11  then flows through a water jacket  31  around a first side of the outer wall  17 , then up the inner dividing wall  23 , back down the inner dividing wall  23 , and up the second side of the outer wall  17  through a return manifold  28  to the return line  33  and back to the fluid heating source  15 . 
     In the system  1  of the present invention the right and left heating chambers  5 ,  7  are connected such that the target liquid  35  that is to be heated flows into the right input port  5 A of the right heating chamber  5  of the first heat exchanger  3 A and through each right heating chamber  5  of the first, middle, and final heat exchangers  3 A,  3 C,  3 B to the left heating chamber  7  of the final heat exchanger  3 B, and then through each left heating  7  chamber of the final, middle, and first heat exchangers  3 B,  3 C,  3 A and through the left output port  7 B of the first heat exchanger  3 A to a hot liquid discharge  37 . Direction of target liquid flow is indicated by arrows between the heat exchangers  3  in  FIGS. 3 and 4 . 
     The right input port  5 A of the first heat exchanger  3   a  is connected to a source  39  of target liquid  35  to be heated, and then right output ports  5 B and right input ports  5 A are connected together such that target liquid  35  flows from the right input port  5 A of the first heat exchanger  3 A through each right heating chamber of the first and middle heat exchangers  3 A,  3 C to the right heating chamber  5  of the final heat exchanger  3 B. The right output port  5 B of the final heat exchanger  3 B is then connected to the left input port  7 A of the final heat exchanger  3 B and left output ports  7 B and left input ports  7 A are connected together such that the target liquid  35  flows from the right output port  5 B of the final heat exchanger  3 B through each left heating chamber  7  of the final and middle heat exchangers  3 B,  3 C to the left heating chamber  7  of the first heat exchanger  3 A and out the output port  7 B thereof. 
     In the system  1  the temperature of the target liquid  35  increases in each chamber such that the temperature of the target liquid  35  at the output port  5 B or  7 B of any heating chamber  5 ,  7  is greater than the temperature thereof at the input port  5 A or  7 A of that same heating chamber. Thus since the target liquid  35  flows through all the right heating chambers  5  before entering the left heating chamber  7  of the final heat exchanger  3 B and then flowing through all the left heating chambers  7  in reverse order, it can be seen that in each heat exchanger  3  of the system  1 , the target liquid  35  in the right heating chamber  5  will have a temperature that is lower than the temperature of the target liquid in the left heating chamber  7  thereof. 
     As well, the lowest temperature of the target liquid  35  will be when entering the system  1  at the input port  5 A of the right heating chamber  5  of the first heat exchanger  3 A, with some temperature increase in each heating chamber between the input and output ports thereof until the target liquid  35  exits the system  1  to the hot liquid discharge  37  at the maximum temperature achieved. 
     In the prior art at a typical work site where it is required to heat a target liquid, as schematically illustrated in  FIG. 6  a number of similar conventional liquid heating units  113  would be connected together, the number selected to achieve the desired temperature increase at the required flow rate. The target liquid  135  enters the first unit at a first temperature T 1 , and leaves the first unit at temperature T 2  and enters the second unit at that temperature T 2 , leaves the second unit at temperature T 3  and enters the third unit at that temperature T 3 , leaves the third unit at temperature T 4  and enters the fourth unit at that temperature T 4  and leaves the fourth unit at the desired temperature T 5 . 
     It is known that the rate of heat transfer from one liquid or like source to another liquid or like target decreases as the temperature gradient between the source and the target decreases. 
     Thus in the conventional system of  FIG. 6 , in the first conventional liquid heating unit the supply fluid will enter the heat exchanger of the unit at a supply temperature TS, heat will be absorbed from the supply fluid relatively quickly by the cold target liquid at temperature T 1  and the supply fluid returns from the heat exchanger  103  to the fluid heater  115  at a return temperature TR significantly less than the supply temperature TS. 
     Then in the second conventional liquid heating unit, the supply fluid will again enter the heat exchanger of the unit at a temperature TS, heat will be absorbed less quickly by the target liquid at the higher temperature T 2  and the supply liquid returns from the heat exchanger  103  to the fluid heater  115  at return temperature TR′ that is higher than the return temperature TR of the supply fluid in the first unit. Similarly on through the rest of the conventional liquid heating units  113 , such that in the schematic illustration of  FIG. 6 , TR&lt;TR′&lt;TR″&lt;TR″′. 
     The amount of energy added by each conventional liquid heating unit  113  to the target liquid is proportional to the difference between the supply temperature TS and the return temperature TR of the unit. Thus each successive conventional liquid heating unit  113  transfers less energy than the prior unit. 
     In contrast in the system  1  of the present invention, since the volume of the right and left heating chambers is substantially the same, the average temperature of the target liquid  35  in each heat exchanger  3  is the average of the temperature RT of the target, liquid in the right heating chamber and the temperature LT of the target liquid in the left heating chamber. 
     Thus in the first heat exchanger  3 A the temperature RT of the target liquid in the right heating chamber  5  that is just entering the system  1  is the coldest of any heating chamber in any of the heat exchangers  3 , while the temperature LT of the target liquid in the left heating chamber  7  that is just leaving the system  1  is the hottest of any heating chamber in any of the heat exchangers  3 . The average temperature in the first heat exchanger  3 A is thus (RTA+LTA)/2. 
     In the next in line middle heat exchanger  3 C′, the temperature RT of the target liquid in the right heating chamber  5  is higher than the temperature in the prior right heating chamber  5  of the first heat exchanger  3 A, and the temperature LT of the target liquid in the left heating chamber  5  is lower than the temperature in the subsequent left heating chamber  7  of the first heat exchanger  3 A, and the average temperature of the target liquid in heat exchanger  3 C′ is about the same as the average temperature of the target liquid in first heat exchanger  3 A. 
     This temperature relationship carries on all through the system  1  from one heat exchanger to the next. In the final heat exchanger  3 B, the temperature RT of the target liquid in the right heating chamber  5  is only one temperature step less than temperature LT of the target liquid in the left heating chamber  7 . The target liquid  35  at this point is just about to turn and return along the left heating chambers  7  of the string of heat exchangers, and the temperature thereof has increased by about one half of the total increase required between the temperature of the target liquid entering the system and the temperature of the target liquid leaving the system, and is therefore at an average temperature of about (RTA+LTA)/2, the same as in the first heat exchanger  3 A. 
     The temperature of the target liquid in each heating chamber  5 ,  7  will increase between the input port and the output port, however generally speaking the above described temperature relationship will be present in each heat exchanger  3 . Thus the temperature gradient between the supply temperature TS of the supply fluid entering each heat exchanger  3  and the average temperature of the target fluid in the right and left heating chambers  5 ,  7  of the heat exchanger  3  will be about the same in each heat exchanger. The return temperature TR of the supply fluid leaving each heat exchanger and returning to the fluid heating source  15  will also be about the same, and so the amount of energy added by each heat exchanger  3  and fluid heating source  15  to the target liquid is about the same. 
     With each heat exchanger  3  and fluid heating source  15  adding the same amount of energy, the number of heating modules  13  in the system  1  of the invention is reduced compared to the number of conventional liquid heating units  113  required, where each successive conventional liquid heating unit  113  transfers less energy than the prior unit. 
     The heat exchangers of the illustrated system  1  also define cleaning apertures  41  in the right and left heating chambers  5 ,  7 , and removable covers  43  on the cleaning apertures. The heating chambers  5 ,  7  are open with substantially smooth walls which can be readily cleaned of accumulated residue, sludge, sediment, and like particles of material that can result from, for example, using unclean water from rivers, ponds, and the like as is sometimes desirable in remote work sites. 
     The cleaning apertures  41  schematically illustrated in  FIG. 4  are defined in the top of the outer wall  17  but same could also be defined in an end wall  19  as illustrated in  FIG. 3 , where an upper cleaning aperture  41 A and a lower drain aperture  41 B in each of the right and left heating chambers  5 ,  7  would facilitate cleaning of foreign material from the heating chamber  5 ,  7 . 
     It is contemplated that 20-30 heating modules  13  could be practically connected in the system  1  of the present invention to provide a wide range of heating capacities for a wide range of water flow volumes and desired target liquid temperatures. The independent heating modules are conveniently transported and connected by simple conduits and connectors such that assembly at a work site is readily accomplished. 
       FIGS. 7-9  schematically illustrate the operation of the water jacket  31  and manifolds  27 ,  28  of  FIG. 3  in use on a heat exchanger apparatus  203  that has only a single heating chamber  205  with an input port  205 A and an output port  205 B. A water jacket  231  substantially encloses the heating chamber  205 . The water jacket  231  will in some applications enclose the ends of the heating chamber  205  as well as the walls thereof, or in other applications the ends will be covered by an insulating layer. The illustrated water jacket  231  has a supply end  231 A extending the length L of the heating chamber  205 , and a return end  231 B extending the length L of the heating chamber  205 . 
     A supply manifold  227  extends along substantially a length of the supply end  231 A of the water jacket  231 . The supply manifold  227  defines a supply port  227 A adapted for connection to a supply line  225  to receive supply fluid  211  from a circulating fluid heater  215 , and a plurality of supply apertures  229  along a length thereof connecting an interior of the supply manifold  227  to an interior of the water jacket  231 . 
     A return manifold  228  extends along substantially a length of the return end  231 B of the water jacket  231 . The return manifold defines a return port  228 A adapted for connection to a return line  233  to return supply fluid  211  to the circulating fluid heater  215  and a plurality of return apertures  230  along a length thereof connecting an interior of the return manifold to the interior of the water jacket  231 . 
     The size of the supply apertures  229  is selected such that a flow of supply fluid  211  entering the supply port  227 A is restricted and such that resulting pressure in the supply manifold  227  causes the supply fluid  211  to flow along the length of the supply manifold  227  and out through each supply aperture  229  in the supply manifold, then around the heating chamber  205  through one of the return apertures  230  into the return manifold  228  and through the return port  228 A to the return line  233 . The supply port  227 A and return port  228 A are located substantially at a mid-point of the length of the corresponding supply and return manifolds  227 ,  228  to provide even fluid flow from each end of the manifolds. 
     The effect of the manifolds  227 ,  228  on the flow of supply fluid through the water jacket  231  is schematically illustrated in  FIG. 9 . The back pressure in the supply manifold  227  ensures that supply fluid  211  moves down the length of the supply manifold  228  and out each supply aperture  229 , more or less equally through each. The flow of supply liquid  211  is indicated by the arrows. Because the return manifold  228  on the opposite end of the water jacket  231  also has return apertures  230  along the length thereof the supply liquid  211  will flow generally from a supply aperture  229  to an opposite return aperture  230  such that a substantially equal flow of supply fluid  211  is present along the length of the water jacket  231  from the supply end  231 A thereof to the return end  231 B thereof. 
     The total area of the supply apertures  229  is generally less than a total area of the return apertures  230  such that there is little resistance to the flow of supply liquid  211  into the return manifold  228 . Thus where the number of supply apertures  229  is the same as the number of return apertures  230 , and where each supply aperture  229  has substantially the same area and each return aperture  230  has substantially the same area, and the area of each return aperture  230  will be greater than the area of each supply aperture  230 . Conveniently the return apertures  230  will simply be somewhat larger than the supply apertures  229 , but the number of apertures  229 ,  230  could vary and a similar result obtained by sizing the apertures accordingly. 
     This even flow provides an even temperature across the length L of the water jacket  231 , decreasing from the supply end  231 A to the return end  231 B as heat is transferred from the supply fluid  211  to a target liquid in the heating chamber  205 . Thus the entire area of the water jacket  231  is substantially at the same temperature gradient and is exposed to the heating chamber  205 . 
     Heat transfer from the water jacket  231  to the heating chamber  205  is increased compared to a typical prior art water jacket  331  illustrated in  FIG. 10 , where the supply fluid  311  enters the water jacket  331  directly through a supply line  325  and leaves directly through a return line  333 . The supply fluid  311  enters the middle of the supply end  331 A of the water jacket  331  and then moves naturally toward the return line  333  in the middle of the opposite return end  331 B thereof, generally as indicated by the arrows. As there are no inlets or outlets near the outer regions  334  of the water jacket  331  removed from the supply line  325  and return line  333 , there is little flow of supply liquid  311  in the outer regions  334  of the water jacket  331 . The temperature of the outer regions  334  is therefore significantly less than the central regions  336  of the water jacket  331  through which the supply liquid  311  predominantly flows, and heat transfer efficiency is reduced. 
     In the heat exchanger apparatus  3  of  FIGS. 3 and 4  as discussed above the heating chamber is divided into a right heating chamber  5  having a right input port  5 A and a right output port  5 B, and a left heating chamber  7  having a left input port  7 A and a left output port  7 B, and the water jacket  31  includes similar supply and return manifolds  27 ,  28  and is configured to heat a target liquid in both the right and left heating chambers  5 ,  7  in a similar even efficient manner. 
     The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention.