Fluid heater

A heat distribution apparatus comprising a fluid conduit having a peripheral wall defining a flow passage and a pair of fluid capillaries extending along the wall and secured thereto. The capillaries being connected to one another in series to provide a fluid flow path along one of the capillaries and a return path along another of said capillaries to convey heat exchange fluid to transfer heat between the flow passage and the heat exchange fluid.

FIELD OF THE INVENTION

The present invention relates to methods and apparatus for distributing heat to or removing heat from remote locations.

DESCRIPTION OF THE PRIOR ART

It is often necessary to distribute heat to or remove heat from remote locations to inhibit freezing at that location. For example, in a fluid conveying system such as a water supply system, there is a danger during cold weather that fluid in the conduit will freeze. There are many proposals to supply heat to such a conduit such as by wrapping an electric heating cable about the conduit but these have tended to be used in locations close to. an electrical power source. Moreover, such installations tend to be used intermittently due to their relative inefficiency and power consumption.

An alternate form of heating apparatus is shown in Canadian Patent 2019590 in which a self-regulating heating cable is inserted within a fluid conduit. With this arrangement it is possible to insulate the conduit to conserve energy and to regulate the power consumption due to the self-regulating nature of the cable. This arrangement has found wide-spread use, particularly in domestic water supplies in remote areas. The heating effect obtained from this installation is however limited to the available length of the heating cable which becomes a limiting factor in some installations. Moreover, the electrical system is prohibited in some environments such as sewers or drains that may contain methane because of the possibility of ignition of sewer gas. There is also a reticence to use electric heating cables in some environments where the cable may be exposed, such as roof and gutter de-icing, where damaged cables may come in contact with water and can result in fire when breakdown occurs. Proper electrical installation ensures the safe operation of such devices but nevertheless there is always a risk of improper installation.

It will also be appreciated that such cables cannot function to extract heat from the fluid.

It is therefore an object to the present invention to provide a method and apparatus for providing heat to remote locations in which the above disadvantages are obviated or mitigated.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a fluid conduit having a peripheral wall to define a flow passage and a pair of fluid capillaries extending along the wall. The capillaries are connected in series and secured to the wall. Fluid may then flow along one of the capillaries in one-axial direction and be returned through the other capillary in the opposite direction. The capillaries are connected to a source of heat exchange fluid and thereby transfer heat through the wall of the conduit between the heat exchange fluid and fluid within the conduit.

In an alternative embodiment, the capillaries may be contained within the peripheral wall defining the conduit. In both embodiments an external jacket may be applied to provide insulation to the conduit.

In an alternative aspect of the invention there is provided a heating apparatus comprising a pair of concentric conduits and an end-cap at one end of said conduits to direct fluid flowing in one of the conduits to the other. At the opposite end, the conduits are connectable to a source of heat exchange fluid.

In a further aspect, the present invention provides a heat distribution system having a source of heat exchange fluid, a manifold having a fluid supply and a fluid return, a pump to circulate fluid between the supply and return through the heat exchange fluid source and a conduit connected to each of the supplies and returns with said conduits being connected in series. The conduits transfer heat along their path.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring therefore toFIG. 1, a heat distribution system10includes a fluid heater12, a central manifold14and a pair of heat distribution apparatus16,18connected at respective locations to the manifold14. It will be appreciated that a cooling effect can be obtained using a fluid cooler rather than a heater but for ease of description reference will be made to the apparatus functioning as a heater.

The fluid heater12is connected to the manifold14through a supply line20and a return line22. The lines20,22are connected through an inlet21and outlet23to a coil24within the heater12. A heating source, such as a gas or electric heater, is supplied to the coil24so that fluid within the coil24is heated as it passes through the coil between the inlet21and outlet23. Fluid is circulated through the coil24by a pump26located within the manifold24and connected to the supply line20. The lines20,22are connected to each of a series of outlets30,32,34provided on the manifold14. Each of the outlets30,32,34has a pair of pipes36,38, one of which is connected to the supply line20and the other of which is connected to the return line22. The pipe36is connected to the supply line20through a check valve40and the return line22is connected to the pipe38through a selector valve42. The valve42may be moved between an open and closed position to permit fluid to flow from the pump26through the coil24to be discharged in the supply conduit22and to the outlet30. The manifold therefore permits selective distribution of fluid to one or more of the outlets30,32,34.

The heat distribution apparatus16is connected to the outlet30and is shown in greater detail inFIG. 2. The apparatus16includes a conduit50having a peripheral wall52defining an interior channel54through which a fluid to be heated, for example water, flows. A pair of capillary tubes56,58are located on the exterior of the peripheral wall52and extend axially parallel to the axis of the conduit50. A metallic tape60is interposed between the capillary tubes and the wall52and an outer sleeve62is located over the conduit50. The sleeve62is preferably made from heat shrinkable plastics material and retains the capillary tubes56,58in location. A tracer wire64extends parallel to the capillary tubes56,58to assist in locating the apparatus16at a later date if it is buried or hidden.

At one end of the conduit52, the capillary tubes56,58are interconnected by a connector66. The connector66is a press fit on the exterior of the capillary tubes56,58and may be secured by a suitable cement. The connector66also includes a wire loop68that may be used to indicate the end of the capillaries during a subsequent inspection.

The opposite end of the capillaries56,58are split from the conduit52and connected at the port30to the lines36,38respectively. A continuous loop is therefore provided from the pump26through the heater12and the capillaries56,58for fluid that is heated within the coil24. The conduit52is used to convey fluid, such as a water supply line and the heat supplied from fluid flowing through the capillaries56,58flows through the wall52to maintain the fluid above the freezing point or other predetermined temperature. The supply of heat may be regulated by varying the temperature of the fluid or by varying the flow rate through modulation of the pump26.

An alternative heat distribution apparatus18is shown in greater detail inFIGS. 4 and 5and is intended for the direct application of heat to remote areas such as an eavestrough or roof or to be located internally within a fluid conduit, such as a water pipeline sewer. The heat distribution apparatus18includes a pair of concentric ducts70,72defined by annular walls71,73respectively with an end-cap76bridging the termination of the ducts70,72. At the opposite end, an end-cap78provides a spigot80for connection to the line36. The conduit70extends through the end-cap78where it is sealed by an o-ring82and terminates in an end-cap84with a connecting spigot86for connection to the line38.

Again, therefore, the heated fluid is discharged through the spigot86into the duct70and is re-directed by end-cap76into the exterior duct72. Heat is transferred across the wall of the duct72to provide distributed heating to the surrounding environment.

Each of the heat distribution apparatus16,18has one or more temperature sensors80,82, along the axis to sense either the temperature of fluid in conduit52or the ambient temperature. The sensor80,82control the valves42to direct fluid to the outlet at which heat is required.

The heating apparatus16may be co-extruded as a unitary moulding and sized to meet the requirements of the fluid within the conduit52. The heating apparatus18is likewise sized to provide a flexible pliant heater that may be entrained along the edge of a roof or within an eavestrough.

Typically the fluid conduit is a extruded polyethylene pipe or similar extrudeable material. A cross linked polyethylene pipe, such as that known by the trade name PEX or KITEC is suitable. For a conduit of nominal 50 mm diameter the capillary tubes56,58have a diameter of 5 mm to 10 mm for the apparatus18, the ducts70,72have a diameter of 12 mm to 16 mm, although it will be appreciated that other dimensions may be used to suit different applications.

In the embodiment ofFIGS. 2 and 3, the number of capillary tubes56,58may be increased to 4, 6, or more if required to meet the heating needs for particular environments. The pair of capillary tubes56,58may then be connected in parallel and supplied through a common manifold or may be controlled independently so that the heating effect can be regulated according to the ambient temperature. Thus, as the temperature drops below a given level, an additional pair of capillaries are connected to the heat source and additional heat supplied to the conduit by multiple flow paths.

It will also be appreciated that the capillaries may be wound about the exterior of the conduit in a spiral pattern if so desired to distribute the heating effect uniformly over the wall52of the conduit.

The capillaries may be co-extruded with the conduit50and may be secured with adhesive if preferred.