GB2107829A

GB2107829A - Thermostatic valves, and solar water heating systems incorporating the same

Info

Publication number: GB2107829A
Application number: GB08207958A
Authority: GB
Inventors: Dudley Vernon Steynor
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-06-09
Filing date: 1982-03-18
Publication date: 1983-05-05

Abstract

A thermostatic valve for controlling the flow of water through a solar panel includes a coil spring (8) formed from shape memory effect brass which expands axially to engage and displace a poppet valve member (2) to open the valve when a predetermined temperature is attained. <IMAGE>

Description

SPECIFICATION Improvements in thermostatic valves, and solar water heating systems incorporating the same The present invention relates to a thermostatic or temperature-responsive valve which is operable to control the flow of a fluid, for example of a liquid such as water. More particularly, the invention relates to a thermostatic valve of the type which opens at or above a predetermined temperature to permit, or increase, fluid flow, and which closes when the temperature falls to or below the predetermined temperature to prevent or reduce fluid flow.

It is an object of the present invention to provide a thermostatic valve of the above type which is relatively reliable, and simple and inexpensive to produce.

According to one aspect of the present invention, there is provided a thermostatic valve comprising a housing having fluid inlet and outlet ports, a valve member cooperable with a valve seat within the housing. the valve member being displaceable relative to the seat to control the flow of fluid between the inlet and outlet ports, and temperature responsive means operable to displace the valve member in a direction to open the valve in response to an increase in temperature, the temperature responsive means including or comprising a shape memory effect actuator.

The displaceable valve member may comprise a poppet-type valve member which is normally biased by a spring towards its seat, i.e. towards a valve-closed position. The shape memory effect (SME) actuator may comprise a coil spring formed from an SME brass, for example a Delta metal alloy, which expands and contracts axially with respective increases and decreases in temperature. When the temperature rises to or above the predetermined value, the SME spring expands, overcoming the force exerted by the bias spring, unseating the poppet valve member, and opening the valve. When the temperature subsequently drops to or below the predetermined value, the SME spring contracts, allowing the bias spring to re-seat the valve member and closing the valve.

Shape memory effect (SME) in a well-known phenomenon peculiar to certain alloys, including certain copper-zinc-aluminium alloys. These alloys deform, or attempt to deform, when subjected to a drop in temperature, while a subsequent temperature rise will allow them to remember, and regain or attempt to regain, their original shape. If deformation of the alloys is restrained, for example as the temperature increases, the force exerted will increase as the temperature increases. One manufacturer of such SME alloys, and specifically Delta alloys, is The Delta Metal Co. Ltd. of Ipswich, Suffolk.

The thermostatic valve embodying the invention is primarily although not exclusively intended to be incorporated in a solar water heating system.

Thus, according to another aspect of the present invention, there is provided a solar water heating system comprising a solar panel arrangement which, in use, is fed from a supply of water under pressure, a reservoir for receiving water from the solar panel arrangement, and a thermostatic valve as above defined for controlling the flow of water from the panel arrangement to the reservoir, the valve comprising a normally closed valve which is adapted to open when the water in the panel arrangement is heated to or above a predetermined temperature to permit the heated water to be displaced from the panel arrangement and flow into the reservoir due to the pressure of the water supply.

From another aspect, the invention provides, for use in a solar water heating system as just defined, a solar panel arrangement having a water inlet intended to be connected to a supply of water under pressure and a water outlet intended to be connected to a reservoir, and a thermostatic valve as above defined incorporated in, or connected or connectable to, the panel arrangement, for controlling the flow of water from the panel arrangement to the reservoir, the valve being a normally closed valve which is arranged or adapted to open only when the water in the panel arrangement is heated to or above a predetermined temperature, to permit heated water in the panel arrangement to flow to the reservoir, and to close to stop or significantly reduce said flow when the temperature of the water in the panel arrangement falls below a predetermined value.

In a system of the above type, cold water, i.e.

water at ambient temperature, is supplied under pressure to the solar panel arrangement from the mains, or a cold water tank fed by the mains. The thermostatic valve remains closed until the temperature of the water in the solar panel arrangement exceeds the predetermined value, whereupon the valve opens, and the heated water is displaced by the pressure of the incoming cold water, into the reservoir. When the panel arrangement is substantially emptied of heated water, the incoming cold water which replaced it is sensed by the valve, and the valve closes. This sequence is repeated each time the contents of the panel arrangement attains or exceeds the predetermined temperature, to progressively fill the reservoir.

The operation of the thermostatic valve is determined by the temperature response of the actuator comprising the SME spring. When the valve is closed, the SME spring may, for example, be heated by the water in the collector, or one of the collectors, of the panel arrangement, and/or by air trapped in the panel arrangement adjacent the collector if the arrangement is such that the temperature of the latter air is related to the temperature of the water in the panel arrangement. When the valve is open, the SME spring may be in heat transfer relation with the water flowing through the valve, and may be cooled thereby when the panel arrangement is emptied of heated water and the incoming cold water from the supply commences to flow out of the panel arrangement.

In order that the invention may be more readily understood, reference will now be made to the accompanying drawings, in which: Figure 1 is a longitudinal section through a temperature-responsive or thermostatic valve embodying the present invention; Figure 2 is a schematic representation of a solar energy-powered water heating system embodying the valve of Figure 1; and Figure 3 is a section, similar to Figure 1, of a modified farm of thermostatic valve.

The thermostatic valve shown in Figure 1 comprises a body assembled from opposite end sections 1 and 10 threadedly interconnected by a centre section 7. The end sections 1 and 10 are provided with appropriately threaded inlet and outlet ports 1 a and 1 Oa respectively which communicate with a valve chamber within the body. The centre section 7 is provided or formed with a perforated or spider-like annular support member 4, the radially inner part 4a of which carries a resilient, for example neoprene, valve seat element 3 which is cooperable with the head of a displaceable poppet-type valve member 2.

The annular support member 4 has a central boss 4b which slidably receives and guides the stem of the valve member 2.

The intended direction of flow of water through the valve is indicated by the arrows, and it will be seen that the head of the valve member 2 is located on the upstream side of the support member 4 with the stem extending downstream of the support member. The valve stem is surrounded by a coil spring 5 which is retained in a compressed state between the support member 4 and a perforate disc-like spring retainer 6 screw-threaded onto the valve stem. The downstream end of the stem is provided with a slot 2a, or is otherwise formed, to permit the valve member 2 as a whole to be rotated relative to the spring retainer 6, by means, for example, of a screw-driver inserted through the outlet port 1 Oa, to adjust the axial position of the spring retainer 6 on the stem, and therefore adjust the compression of the valve spring 5.

Located within the valve body on the downstream side of the spring retainer 6 is a temperature-responsive actuator comprising a tightly-coiled spring 8 made from an SME material such as a Delta alloy. As shown in Figure 1, the axial length of the SME spring 8, in its cold or ambient condition, is less than the axial spacing between the spring retainer 6 and downstream inner end wall of the body end section 10, so that a clearance exists between the spring 8 and retainer 6 and/or the said inner end wall of the section 10.

The valve may be constructed so that, in operation, heat to extend the SME spring 8 and open the valve is transferred to the spring 8 from the surrounding environment, for example air, via the valve body. Additionally or alternatively, heat may be transferred to the spring 8, when the valve is closed, by water from the inlet port 1 a, which is allowed to bleed or leak past the valve member 2 and contact the spring. When the valve is open, the extension of the spring 8 is dependent upon the temperature of the water flowing through the valve.

The characteristics of the specific SME spring 8 employed in the illustrated embodiment are such that the spring will commence to expand axially from its tightly coiled unextended condition shown at approximately 1 50C, and, if unrestrained, would achieve a maximum extension of approximately twice the unextended length at approximately 400C. Thus, in the illustrated embodiment, at approximately 1 50C, the spring 8 will commence to expand and to take up the clearance between itself and the spring retainer 6. Further temperature rise will cause the spring 8 to expand and exert pressure against the retainer 6. When this pressure overcomes the combined resistance of the spring 5 plus that of the water pressure acting on the head of the valve member 2, the valve member will lift off the valve seat element 3.As soon as this occurs, the water pressure acting on the head of the valve member drops, permitting the valve member to open further, and enabling an increased rate of flow of water through the valve under the influence of the pressure of mains or other water supply. The water flowing through the valve contacts the spring 8, and when the temperature of the water drops, for example to below 1 0 C, the spring 8 will be correspondingly cooled and will contract axially, rapidly resuming its tightly coiled condition shown, and the spring 5 coupled with the water pressure will re-seat the valve member 2, closing the valve.

The valve described and illustrated is fully adjustable to accommodate different water temperatures and pressures. This is achieved by rotating the valve stem in either direction relative to the spring retainer 6 as previously described, thus altering the compression of the valve spring 5, and the cold clearance between the retainer 6 and the SME spring 8. This compensates for differences in water pressures acting on the valve head. In addition, since the pressure exerted on the retainer 6 by the spring 8 depends upon temperature (i.e. the higher the spring temperature the greater the force exerted by the spring 8), it is possible to obtain any desired setting covering a range of water temperatures from approximately 40 to 1 000C coupled to water pressures of from approximately 1 to 4 bar.

The thermostatic valve shown in Figure 1 may, to advantage, be incorporated in a solar energypowered water heating system, such as that shown in Figure 2. This system comprises a mains-fed cold water tank 1 which may conveniently be the cold water storage tank of a domestic water system, mounted in or on the roof of a house or other dwelling.

The cold water tank 11 is connected to the input of a solar panel 12 (or array of panels) mounted on the roof or wall of the house below the level of the tank 11, and the output of the panel 12 is connected to a hot water reservoir comprising a thermally insulated tank 13, via a temperature-responsive or thermostatically- operated valve V as shown in Figure 1, and a manually adjustable valve 1 5. The hot water storage tank 13 has at least one tap 1 3a for supplying water, for example to a basin and/or bath, and an overflow or expansion pipe 1 3b which may also drain into the bath or basin. The tank is also fitted with a conventional immersion heater (not shown) for providing supplemental heating.

The solar panel 12 may be of any appropriate type, but is preferably of the type disclosed in Patent No. 1,179,681, manufactured under the Trade Mark "Solarcoil" by Verdik Ltd. of Lane End, High Wycombe, Buckinghamshire. This panel basically comprises a collector in the form of a flat, spirally wound coil 1 2a of copper tube mounted in an appropriate casing 1 2b. The inlet 1 2c of the panel is connected to the centre of the spiral coil 1 2a, and the outlet 2d is connected to the radially outer end of the coil via the valve V.

The valve V is mounted in the solar panel casing 1 2b so as to sense the air temperature in the space containing the coil 1 2a. The valve V is located to one side of the coil 1 2a so as to be shielded from, and therefore minimise the heating effect of, direct sunlight Shielding could, however, alternatively be achieved by locating the valve B behind the coil 1 2a, i.e. between the coil and the base of the panel casing.

In operation, initially, the valve V is set to the required temperature, for example 500C, and the hot water storage tank 1 3 will be empty. The manual valve 1 5 is adjusted to set the required maximum flow rate of water through the system.

If the coil 1 2a of the solar panel 12 is initially empty, and when the air temperature within the casing 1 2b, sensed by the SME spring in the valve V, reaches or exceeds the pre-set value, the valve V will open, and since the system is vented by the overflow 1 3b, cold water (i.e. water at a temperature substantially less than 500C) at a pressure dependent upon the relative height of the cold water tank 11 will flow from the latter into the coil 1 2a. When the cold water is sensed by the SME spring in the valve V, the valve closes and flow ceases.

Solar energy collected by the panel 2 heats the water in the coil 1 2a, and when this temperature reaches 500C, the air temperature in the "Solarcoil" type of solar panel will approximate or be slightly iower than 500 C, and the valve V, which may be adjusted to compensate for this water/air temperature difference if necessary, opens, and the heated water is ejected from the coil into the tank 13 by further cold water under pressure flowing from the tank 11 into the coil.

When this incoming cold water is sensed by the SME spring in the valve V, the valve closes again, so that only, or substantially only, water at or above 500C flows into the tank 1 3. Solar energy will then heat the fresh charge of cold water in the coil 1 2a, and the previously described sequence will be repeated.

The valve hereinbefore described is of the type in which the SME actuator is operable to displace the valve member so as to open the valve at or above a predetermined temperature to permit or increase fluid flow, the valve closing when the temperature falls to or below the predetermined temperature to prevent or reduce fluid flow.

However, according to a modification of the invention, the SME actuator is operable to retain the valve member in its valve-closed condition at or above a predetermined temperature, and is operable to cause, or allow, the valve member to be displaced in a direction to open the valve when the temperature drops to or below the predetermined temperature.

As shown in Figure 3, which illustrates one embodiment of such a modified thermostatic valve, the positions of the return spring and SME spring are reversed. In particular, the SME spring 8 surrounds the stem of the valve member 2, and acts between the support member 4 and spring retainer 6, whilst the return spring 5 acts, and is retained in compression, between the spring retainer and the downstream (lower inner end wall of the valve body end section 10. The characteristics and dimensions of the SME spring 8 are such that it will assume and remain in its axially expanded condition shown whilst its- temperature does not fall to or below a predetermined temperature, for example 500C.In this expanded condition, the SME spring 8 acts between the support member 4 and spring retainer 6 with a force which is greater than that exerted by the return spring 5, thus urging the valve member 2, and retaining it, in its valveclosed position as shown. When the temperature drops to or below the predetermined temperature, the SME spring 8 will axially contract, for example to or toward a condition in which it is tightly coiled (i.e. its adjacent turns contact one another), and the return spring 5 will be free to urge the valve member 2, via the spring retainer 6, away from the seat element 3 to a valve-open condition.

The valve shown in Figure 3 may be employed to protect a liquid-containing system against damage resulting from freezing of the liquid, by automatically opening and draining down the system, or part thereof, when the temperature approaches the freezing point of the liquid. For example, as applied to a solar water heating system, at least one such valve may be connected to the system, at or adjacent the lowermost region of the or each solar panel, so that whenever the outside air temperature falls below a predetermined temperature, for example 50C, the valve will automatically open, allowing ths water to drain from the solar panel or panels.In addition, at least one further such valve may be connected to the system, at or adjacent the uppermost region of the or each panel, the further valve opening and allowing air to vent into the or each panel upon opening of the first or water drain valve, to prevent or minimise the risk of formation of an air lock.

The valve of Figure 3 may, for example, be used in combination with a valve of the type shown in Figure 1, and may be incorporated in, or attached to, a solar panel as shown in Figure 2, or may be otherwise appropriately connected into the system shown in Figure 2.

Another application of the valve shown in Figure 3 is in outdoor water pumping systems, such as a water supply system derived from a river or stream, employing a "Hydram"pump or equivalent operated by the flow or head of water.

In such a system, the valve could be employed to automatically open and drain water from the system or pump as the temperature approaches freezing point.

The automatic thermostatic or temperatureresponsive valves herein described possess various significant advantages. They are robust and reliable, and relatively simple and inexpensive to manufacture, adjust and install. The valves are adjustable to accommodate a wide range of temperatures and pressures, and since the poppet-type valve arrangement is arranged with the valve head upstream of its associated seat, water pressure does not act to open the valve, thus enabling the valves to operate satisfactorily at higher pressureithan prior normally closed thermostatic valves, i.e. at pressures at least up to 4 bar. The valves are relatively compact, and their ports and components are mutually coaxially arranged, thus rendering the valves particularly suited to in-line connection to pipework.

It will be understood, that various modifications may be made. For example, SME actuators having configurations other than that of a coil spring may be employed, and the SME actuators may be employed in combination with valve arrangements other than poppet-type valve arrangements.

In its simplest form, the valve may be nonadjustable, the calibration of the valve to operate at the required temperature, or over the required range of temperatures, being effected during manufacture. Alternatively, other forms of adjustment may be provided, preferably enabling adjustment to be effected externally of the valve body without disconnecting the outlet port union.

For example, a wedge or cam device could be interposed between the valve spring which surrounds the valve stem and its seating on the support member 4 to permit adjustment of the compression of the latter spring, the wedge or cam device being operated by a spindle or lever extending laterally out of the valve body via a suitable seating and gland. In this event, the latter spring 5 may be conical or tapered instead of cylindrical in its axial direction, with its apex directed towards the support member 4 and cooperating with the wedge or cam device.

While the valves are particularly suited to use in combination with solar heating systems they may be used to advantage in other applications where thermostatic regulation of water or other liquid, or a fluid, is required.

The valve shown in Figure 3 is not restricted to the specific applications herein described, but may be employed in many applications where a valve is required to open upon a temperature drop and to close upon a temperature rise. The valve may be operable to open and close at any required temperature, or within any required temperature range, depending upon the characteristics of the SME spring, and/or the adjustability of the valve, etc. The valve could, for example, be designed for use as a radiator valve, such as a domestic central heating radiator valve.

Claims

1. A thermostatic valve comprising a housing having fluid inlet and outlet ports, a valve member cooperable with a valve seat within the housing, the valve member being displaceable relative to the seat to control the flow of fluid between the inlet and outlet ports, and temperature responsive means operable to displace the valve member in a direction to open the valve in response to an increase in temperature, the temperature responsive means including or comprising a shape memory effect actuator.

2. A valve as claimed in claim 1, wherein the displaceable valve member comprises a poppettype valve member which is normally biased by a spring towards its seat, i.e. towards a valveclosed position.

3. A valve as claimed in claim 2, wherein the shape memory effect (SME) actuator comprises a coil spring formed from an SME brass which expands and contracts axially with respective increases and decreases in temperature.

4. A valve as claimed in claim 3, wherein the SME spring is arranged and adapted so that, in operation, when the temperature rises to or above the predetermined value, the SME spring expands, overcoming the force exerted by the bias spring, unseating the poppet valve member, and opening the valve, and when the temperature subsequently drops to or below the predetermined value, the SME spring contracts, allowing the bias spring to re-seat the valve member and closing the valve.

5. A thermostatic valve, substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

6. A solar water heating system comprising a solar panel arrangement which, in use, is fed from a supply of water under pressure, a reservoir for receiving water from the solar panel arrangement, and a thermostatic valve as claimed in any of claims 1 to 5 for controlling the flow of water from the panel arrangement to the reservoir, the valve comprising a normally closed valve which is adapted to open when the water in the panel arrangement is heated to or above a pre determined temperature to permit the heated water to be displaced from the panel arrangement and flow into the reservoir due to the pressure of the water supply.

7. For use in a solar water heating system as claimed in claim 6, a solar panel arrangement having a water inlet intended to be connected to a supply of water under pressure and a water outlet intended to be connected to a reservoir, said thermostatic valve being incorporated in, or connected or connectable to, the panel arrangement, for controlling the flow of water from the panel arrangement to the reservoir, the valve being a normally closed valve which is arranged or adapted to open only when the water in the panel arrangement is heated to or above a predetermined temperature, to permit heated water in the panel arrangement to flow to the reservoir, and to close to stop or significantly reduce said flow when the temperature of the water in the panel arrangement falls below a predetermined value.

8. A thermostatic valve comprising an elongate housing having fluid inlet and outlet ports spaced apart in the longitudinal direction of the housing, a poppet valve member having a longitudinal axis disposed generally parallel to the longitudinal direction of the housing, and being displaceable relative to a valve seat within the housing disposed generally coaxial with the poppet valve member, the valve member including a valve head cooperable with the valve seat, the valve head and valve seat being disposed in the fluid flow path in the housing between the fluid inlet and outlet ports, with the valve head on the upstream side of the valve seat, the valve member being displaceable relative to the valve seat to control the flow of fluid between the inlet and outlet ports by means of temperature responsive means including or comprising a shape memory effect (SME) actuator.

9. A valve as claimed in claim 8, wherein the SME actuator comprises an SME brass coil spring disposed generally coaxial with the poppet valve member on the downstream side of the valve head, the SME spring being operable to displace the poppet valve member in one axial direction, and a return spring comprising a second coil spring disposed generally coaxial with the poppet valve member on the downstream side of the valve head, the return spring being operable to urge the poppet valve member in the opposite axial direction.

10. Valve as claimed in claim 9, wherein the inlet and outlet ports, the poppet valve member and valve seat, and the SME spring and return spring, are all aligned with the longitudinal axis of the housing.

11. A valve as claimed in claim 8 or 9, which comprises a valve as claimed in any of claims 1 to 4.

12. A valve as claimed in claim 8, 9 or 10, of a modification of the valve claimed in claim 1, 2 or 3, wherein the SME actuator is operable to retain the valve member in its valve-closed condition at or above a predetermined temperature, and is operable to cause, or allow, the valve member to be displaced in a direction to open the valve when the temperature drops to or below the predetermined temperature.

13. A thermostatic valve, substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

14. A valve as claimed in claim 12 or 13 in combination with a solar water heating system as claimed in claim 6, or a solar panel arrangement as claimed in claim 7, the said valve being connected to the system or panel arrangement at or adjacent the lowermost region thereof, so as to open at or below a predetermined temperature to allow liquid to drain from the solar panel arrangement.

1 5. A system or solar panel arrangement as claimed in claim 14, including an additional valve as claimed in claim 12 or 13, connected to the system or panel arrangement at or adjacent the uppermost region thereof, to allow air to vent into the panel arrangement upon opening of the drain valve.

16. A solar energy-powered water heating system, substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.