Patent Application
20150369517
This disclosure relates to the field of liquid heating equipment and in particular equipment for heating liquid in portable tanks and like containers.
Heat exchangers are used in many industries for heating liquids, where a hot heating fluid, such as steam, water, glycol or the like, is circulated through a heating circuit that is immersed in the target liquid to be heated. Commonly the target liquid will be contained in a tank or like container, and the heating circuit will be mounted inside the tank with inlet and outlet ports exposed on the tank exterior. A fluid heating system, such as a boiler or water heater, or the like is connected to the ports such that heating fluid enters the inlet port at a high temperature and flows through the heating circuit to the outlet port where the temperature has dropped due to the transfer of heat to the target liquid. The heating fluid then flows from the outlet port back to the fluid heating system where it is reheated.
The amount of heat transferred from the heating fluid to the target fluid increases as the temperature difference (AT) between the hot fluid and the target liquid increases. Also the amount of heat removed from the heating fluid and transferred to the target liquid increases as the surface area of the heating circuit that is exposed to the target liquid increases, either by making the heating circuit longer, or by increasing the surface area of the heating circuit per unit of length.
In many industries water is stored temporarily in large tanks that are transported to and set up at a work location for various purposes. Often as well the stored water must be heated to a desired temperature. One common large portable tank is the cylindrical 400 barrel (bbl) tank, with dimensions of about 12 feet in diameter and a height of about 20 feet. These dimensions allow for fairly easy transport on roads on most jurisdictions, and provide considerable capacity of 400 bbl or 16,800 US gallons. Oil well fracturing operations for example may utilize several 400 bbl or similar large capacity tanks as these operations require large quantities of water, and commonly also require that the water be heated to temperatures up to 140° F.
Conventional large tanks have access doors that provide access through an access opening to the tank interior for personnel to enter and clean the tank interior. The dimensions of the access openings are fairly standard for any given size of tank. As well, to facilitate heating the water in the tank, a heating circuit is sometimes mounted inside the tank. The conventional mounted heating circuit typically comprises a two inch diameter steel pipe supported inside the tank somewhat above the tank floor and following inside the cylindrical wall from a first port extending through the tank wall to a second port extending through the tank wall. A heating system is connected to the ports and hot heating fluid is circulated through the pipe to warm the target liquid, being the water in the tank. The total length of the heating circuit is somewhat less than π times the tank diameter (Da), and so for a 12 foot diameter tank, the length will be about 30 feet.
With the small outer surface area provided by 30 feet of two inch pipe, in order to transfer sufficient heat to raise the temperature of the water, the heating fluid must be quite high, increasing the AT between the heating and target fluids and increasing the heat transfer rate. Thus where high temperature water is required, it is common to use steam as the heating fluid, since the steam temperature can be maintained at about 300° F.
The use of steam heating systems however has significant drawbacks. The steam pressure can easily exceed 2000 pounds per square inch (psi) so even a small leak can cause serious injury to nearby personnel. Steam heaters are considered high pressure vessels, since they are closed to the atmosphere, and as such require operators with specialized training in the operation of the steam system. To handle the high pressures, the pipe of the conventional permanently mounted heating circuit is quite thick, and there can thus be a significant temperature gradient between the inside and outside surface of the wall, such that heat does not transfer as readily as it would though a thin wall pipe where the temperature gradient between the inside and outside surfaces of the wall is less.
A further problem with steam is that steam condenses back into water in the steam loop, and so vessels or conduits can be ruptured when temperatures reach below freezing and trapped water expands.
Alternatively, a glycol heating system can be used where a hot glycol liquid is circulated through the pipe. While other liquids can be used, glycol is a popular choice as it is not subject to freezing and the damage that can result from same. These glycol systems are open to the atmosphere and so pressures in the heating circuit are only those required to circulate the glycol, about 20-40 psi. There are no high pressures or danger of explosion, and so specially qualified personnel are not required. The temperature of the glycol must be kept below the boiling point, or at a maximum of about 200° F. The rate of heat transfer is therefore much less than when using a steam heating system at 300° F., and the glycol heating systems are thus mainly used to prevent the water in the tank from freezing.
It is also known to draw water from the tank and pass the water through a water heater and return the water back to the tank. A problem in many situations is that the water in the tank is often contaminated and spillage can cause environmental damage and costly clean-up operations. Drawing the contaminated water out of the tank exposes same to the risk of freezing and subsequent rupture of lines and spillage if equipment fails. Seals and the like are also subject to failure and subsequent contaminated leakage.
These portable tanks are subjected to considerable shock forces when lifted and tipped horizontally onto a vehicle deck for transport. During transport to the work site as well, these tanks are often carried over rough roads and so the heating circuit must be robust to avoid damage. The thick wall pipe thus also serves to resist damage, although damage can occur at the ports through the tank wall, or to the support legs holding the pipe above the tank floor, as the pipe flexes and vibrates during transit over rough roads.
The present disclosure provides a heat exchanger apparatus that overcomes problems in the prior art.
In a first embodiment the present disclosure provides a heat exchanger apparatus for a portable tank, where the portable tank includes an access opening and an access door removably attachable to seal the access opening. The apparatus comprises a cover plate configured to be removably attached to the access opening to seal the access opening, and a heating circuit attached to an inner surface of the cover plate such that when the cover plate is attached to the access opening, the heating circuit extends into an interior of the tank. Input and output ports extend through the cover plate and are connected at inner ends thereof to the heating circuit such that fluid flowing into the input port flows through the heating circuit to the output port. The input and output ports are adapted at outer ends thereof for attachment to a fluid heating system to circulate heating fluid through the heating circuit.
In a second embodiment the present disclosure provides a method of heating a target liquid in a portable tank, where the portable tank includes an access opening and an access door removably attachable to seal the access opening. The method comprises configuring a cover plate to be removably attached to the access opening to seal the access opening; attaching a heating circuit to an inner surface of the cover plate such that when the cover plate is attached to the access opening, the heating circuit extends into an interior of the tank; extending input and output ports through the cover plate and connecting inner ends thereof to the heating circuit; installing the tank at a desired location; attaching the cover plate to the access opening such that the heating circuit extends into the interior of the tank, and such that the access opening is sealed; filling the tank with the target liquid to a level above the heating circuit; attaching outer ends of the input and output ports to a fluid heating system and circulating heating fluid through the heating circuit.
The present disclosure provides a heat exchanger apparatus for a portable tank that provides sufficient surface area to allow glycol at 200° F. to heat the target liquid, thus avoiding the complications encountered when using pressurized steam at 300° F. The target liquid is also kept inside the tank at all times, reducing the risk of spillage.
The risk of damage to the heat exchanger apparatus during loading and transport of the tank is reduced as the heat exchanger apparatus can simply be removed and transported separately. As well the portable tanks of the kind contemplated for use with the presently disclosed apparatus and method are fairly standard in construction and instead of installing a permanent heat exchanger apparatus in tanks which might possibly be used for heating liquid, the heat exchanger apparatus of the present disclosure can be simply installed in any tank where heat is required. Thus the present disclosure provides considerable versatility and reduces costs.
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:
A heating circuit 13 is attached to the inner surface 11A of the cover plate 11 such that when the cover plate 11 is attached to the access opening 3, the heating circuit 13 extends into an interior of the tank 1 as schematically illustrated in
Input and output ports 15A, 15B extend through the cover plate 11 and connect at inner ends 17 thereof to the heating circuit 13 such that fluid flowing into the input port 15A flows through the heating circuit 13 to the output port 15B. The input and output ports 15A, 15B are adapted at outer ends 19 thereof for attachment to a fluid heating system 21 to circulate heating fluid through the heating circuit 13. The fluid heating system 21 can use steam, glycol, water, as the heating fluid. The present apparatus 10 provides a large surface area for heat transfer from the heating fluid to the target liquid such that an un-pressurized glycol or water fluid heating system 21 can effectively heat the target fluid, and it is contemplated that typically the user will prefer such an un-pressurized system to avoid the hazards and specialized personnel requirements of a steam system.
In the illustrated apparatus 10, the heating circuit 13 comprises a heating conduit 23 extending from the inner surface 11A of the cover plate 11 towards a far wall 25 of the tank 1 opposite the access opening 3, as schematically illustrated in
The illustrated heating conduit 23 is also provided by corrugated tubing, as schematically illustrated in
The corrugated heating conduit 23 is also flexible, which provides versatility in making up the heating circuit 13. The heating conduit 23 is conveniently provided by corrugated stainless steel tubing with a wall thickness T that is less than about 0.015 inches. Such tubing is readily available as the inner stainless steel portion of a flexible gas line is provided by such tubing with a wall thickness T of 0.010 inches, which is then covered by a coating for use as a gas line. When used as the heating conduit 23 in the present disclosure, the stainless steel tubing with the very thin wall is an excellent conductor, allowing heat to pass readily from the heating fluid flowing in the heating conduit through the tubing wall to the target fluid, and is also very light, facilitating manipulation of the apparatus 10 during installation.
To add structure to the heating circuit 13, especially where the heating conduit 23 is flexible but also where a rigid heating conduit 23 is used, a brace member 29 is attached to the inner surface 11A of the cover plate 11 and extends toward the far wall along the heating circuit 13, and the heating conduit 23 is supported on the brace member 29 as schematically illustrated in
To facilitate manual manipulation of the apparatus 10, the brace member 29 should be as light weight as possible, and can be, for example, an open framework made with aluminum tubing. Other brace structure could be used as well. To minimize weight, the cover plate 11 can also be made from aluminum, or some other light weight material. Some plastics may be suitable, as the pressure against the cover plate 11 is typically not excessive.
Also in the illustrated apparatus 10, a support member 31, is mounted on a bottom inner portion of the heating circuit 13. The support member 31 is typically a skid adapted to slide along the tank floor 33 and support the inside end of the heating circuit 13 as it moves into the interior of the tank 1 during installation of the cover plate 11, as schematically illustrated in
The present disclosure provides a method of heating a target liquid in a portable tank 1, where the portable tank 1 includes an access opening 3 and an access door 5 removably attachable to seal the access opening. The method comprises configuring a cover plate 11 to be removably attached to the access opening 3 to seal the access opening; attaching a heating circuit 13 to an inner surface 11A of the cover plate 11 such that when the cover plate is attached to the access opening 3, the heating circuit 13 extends into an interior of the tank 1; extending input and output ports 15 through the cover plate 11 and connecting inner ends 17 thereof to the heating circuit 13; installing the tank 1 at a desired location; attaching the cover plate 11 to the access opening 3 such that the heating circuit 13 extends into the interior of the tank 1, and such that the access opening 3 is sealed; filling the tank 1 with the target liquid to a level above the heating circuit 13; attaching outer ends 19 of the input and output ports 15 to a fluid heating system 21 and circulating heating fluid through the heating circuit 13.
When it is desired to move the tank 1 to a different location, the target liquid is removed from the tank 1 and the cover plate 11 is removed from the access opening 3 the heating circuit 13 is withdrawn from the interior of the tank; loading the tank 1 and the heat exchanger apparatus 10 comprising the cover plate 11 with heating circuit 13 on one or more vehicles for transport.
The present disclosure provides a heat exchanger apparatus 10 for a portable tank 1 that provides sufficient surface area to allow glycol at 200° F. to heat the target liquid, thus avoiding the complications encountered when using pressurized steam at 300° F. The target liquid is also kept inside the tank 1 at all times, reducing the risk of spillage.
Portable tanks of the kind contemplated for use with the presently disclosed apparatus and method are fairly standard in construction and the heat exchanger apparatus 10 can be configured to be installed on such a tank, and then used on any other tank with the same access opening, providing considerable versatility. The expense of installing a permanent heat exchanger system in each tank is avoided.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2854794 | Jun 2014 | CA | national |
