A WORKING FLUID

Abstract

A working fluid for use in a heat transfer system, for example of the type used to transfer heat in a heat engine. The working fluid comprises a plurality of nano-particles suspended in a base fluid so as to improve a heat transfer property of the base fluid. Ideally the nano-particles are suspended in the base fluid in a colloidal suspension. A system for manufacturing a nano-fluid is also described. The system includes a plurality of hoppers for containing types of nano-particle and a reservoir that contains a base fluid. A control means controls valves on the hoppers and on the reservoir in order to dispense working fluid and defined amounts of nano-particles into a mixer tank. A mixer mixes the nano-particles with the base fluid to produce a nano-fluid which is in colloidal suspension in the working fluid.

Claims

1. A working fluid comprising a plurality of nano-particles suspended in at least one hydro-fluoro-ether base fluid.

2. A working fluid according to claim 1 wherein the nano-particles are suspended in the base fluid in a colloidal suspension.

3. A working fluid according to claim 1 or claim 2 wherein the plurality of nano-particles comprise nano-particles of boron carbine (B.sub.4C), nano-particles of boron nitride (BN), nano-particles of beryllium oxide (BeO), nano-particles of magnesium oxide (MgO), nano-particles of graphite, nano-particles of silicon (Si), nano-particles of aluminium nitride (AlN), nano-particles of silicon carbide (SiC), nano-particles of aluminium oxide (Al.sub.2O.sub.3), nano-particles of titanium dioxide (TiO.sub.2), nano-particles of silicon dioxide (SiO.sub.2), nano-particles of copper (II) oxide (CuO), or any combination thereof.

4. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of boron carbide (B.sub.4C).

5. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of boron nitride (BN).

6. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of beryllium oxide (BeO).

7. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of magnesium oxide (MgO).

8. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of graphite or graphene.

9. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of silicon (Si).

10. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of aluminium nitride (AlN).

11. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of silicon carbide (SiC).

12. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of aluminium oxide (Al.sub.2O.sub.3).

13. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of titanium dioxide (TiO.sub.2).

14. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of silicon dioxide (SiO.sub.2).

15. A working fluid according to any preceding claim wherein the plurality of nano-particles comprises nano-particles of copper (II) oxide (CuO).

16. A working fluid according to any preceding claim wherein nano-particles have at least two characteristic dimensions less than 100 nm.

17. A working fluid according to any preceding claim wherein nano-particles have dimensions less than 100 nm.

18. A working fluid according to any preceding claim wherein nano-particles have at least two dimensions less than 75 nm.

19. A working fluid according to any preceding claim wherein nano-particles have dimensions less than 75 nm.

20. A working fluid according to any preceding claim wherein nano-particles have at least two dimensions less than 50 nm.

21. A working fluid according to any preceding claim wherein nano-particles have dimensions less than 50 nm.

22. A working fluid according to any preceding claim wherein nano-particles have at least two dimensions less than 25 nm.

23. A working fluid according to any preceding claim wherein nano-particles have dimensions less than 25 nm.

24. A working fluid according to any preceding claim wherein the nano-particles have dimensions greater than nm.

25. A working fluid according to any preceding claim wherein the nano-particles have dimensions greater than 10 nm.

26. A working fluid according to any preceding claim wherein the nano-particles have dimensions greater than 15 nm.

27. A working fluid according to any preceding claim wherein the base fluid is at least 50% hydro-fluoro-ethers by volume.

28. A working fluid according to any preceding claim wherein the base fluid comprises HFE-7000 hydro-fluoro-ether.

29. A working fluid according to any preceding claim wherein the base fluid is at least 50% HFE-7000 hydro-fluoro-ether by volume.

30. A working fluid according to any preceding claim wherein the volumetric concentration of the nano-particles within working fluid is greater than 1%.

31. A working fluid according to any preceding claim wherein the volumetric concentration of the nano-particles within working fluid is greater than 2%.

32. A working fluid according to any preceding claim wherein the volumetric concentration of the nano-particles within working fluid is greater than 3%.

33. A working fluid according to any preceding claim wherein the volumetric concentration of the nano-particles within working fluid is greater than 4%.

34. A working fluid according to any preceding claim wherein the volumetric concentration of the nano-particles within working fluid is greater than 5%.

35. A working fluid according to any preceding claim wherein the volumetric concentration of the nano-particles within working fluid is greater than 6%.

36. A working fluid according to any preceding claim wherein the volumetric concentration of the nano-particles within working fluid is greater than 7%.

37. A working fluid according to any preceding claim wherein the volumetric concentration of the nano-particles within the working fluid is less than 8%.

38. A working fluid according to any of claims 1 to 35 wherein the volumetric concentration of the nano-particles within the working fluid is less than 7%.

39. A working fluid according to any of claims 1 to 34 wherein the volumetric concentration of the nano-particles within the working fluid is less than 6%.

40. A working fluid according to any of claims 1 to 33 wherein the volumetric concentration of the nano-particles within the working fluid is less than 5%.

41. A working fluid according to any of claims 1 to 32 wherein the volumetric concentration of the nano-particles within the working fluid is less than 4%.

42. A working fluid according to any of claims 1 to 31 wherein the volumetric concentration of the nano-particles within the working fluid is less than 3%.

43. A working fluid according to any of claims 1 to 30 wherein the volumetric concentration of the nano-particles within the working fluid is less than 2%.

44. A working fluid according to any of claims 1 to 29 wherein the volumetric concentration of the nano-particles within the working fluid is less than 1%.

45. A working fluid according to any preceding claim wherein the heat transfer property of the base fluid which is improved is the heat transfer coefficient (h).

46. A system for manufacturing a working fluid according to any of claims 1 to 45 including a plurality of hoppers each containing at least one type of nano-particle; a reservoir containing the at least one base fluid; control means associated with valves on the hoppers and a valve on the reservoir, the valves are operable to dispense a user defined volume of base fluid and user defined amounts of nano-particles into a mixer tank; a mixer for mixing the nano-particles with the base fluid in the mixer tank to produce a nano-fluid; and a dispenser for dispensing the working fluid into storage containers.

47. A system according to claim 46 wherein the mixer is operative to mix the nano-particles and the at least one base fluid until the nano-particles are suspended in the base fluid in a colloidal suspension.

48. A method of operating the system for manufacturing a working fluid according to either claim 46 or 47.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0048] FIG. 1 is a table showing the increase in the heat transfer coefficient (W/(m.sup.2K) of a working fluid when different nano-particles are added at different volumetric concentrations;

[0049] FIG. 2 is Table 1 showing the power of a system performing an organic Rankine cycle when using different working fluids;

[0050] FIG. 3 is a diagram illustrating key steps in the production of a working fluid with different nano-particles; and

[0051] FIG. 4 is a basic functional diagram of a production plant for manufacturing working fluid with a range of different nano-particles.

DETAILED DESCRIPTION OF THE FIGURES

[0052] FIG. 1 is a table illustrating the percentage differences between the mean heat transfer coefficients of a HFE-7000 based working fluid and thirty-six different working nano-fluids, each of which comprises nano-particles of one of twelve different chemicals added to the HFE-7000 based working fluid at one of three different volumetric concentrations.

[0053] The thirty-six different basic working fluids, are described, these being separate example embodiments of the invention. A particularly preferred embodiment may be derived, for example by coating some of the nano-particles with graphene. A refinement of these additional variations may be obtained by coating nano-particles with a monolayer coating of graphene on nano-particles.

[0054] The twelve different chemicals from which the nano-particles comprised by the thirty-six working nano-fluids are formed are: boron carbine (B.sub.4C), boron nitride (BN), beryllium oxide (BeO), magnesium oxide (MgO), graphite, graphene (reduced graphene), silicon (Si), aluminium nitride (AlN), silicon carbide (SiC), aluminium oxide (Al.sub.2O.sub.3), titanium dioxide (TlO.sub.2), silicon dioxide (SiO.sub.2), and copper (II) oxide (CuO).

[0055] The three different volumetric concentrations of the nano-particles within the working fluid being 1%, 4%, and 6% by volume.

[0056] The mean heat transfer coefficients of the HFE-7000 working fluid and the thirty-six working nano-fluids are measured when conducting heat in flows with Reynolds Number of around 1200.

[0057] The nano-particles of the thirty-six examples of working nano-fluids have dimensions of approximately 45 nm.

[0058] All thirty-six of the working nano-fluids have greater mean thermal conductivities than the HFE-7000 working fluid with no suspended nano-particles present.

[0059] FIG. 2 is a table illustrating the power output of as system performing an organic Rankine cycle between a solar thermal panel and an expander, when using thirteen different working fluids.

[0060] The thirteen working fluids are: pure HFE-7000, a nano-fluid comprising nano-particles of boron carbine (B.sub.4C) suspended in HFE-7000, a nano-fluid comprising nano-particles of boron nitride (BN) suspended in HFE-7000, a nano-fluid comprising nano-particles of beryllium oxide (BeO) suspended in HFE-7000, a nano-fluid comprising nano-particles of magnesium oxide (MgO) suspended in HFE-7000, a nano-fluid comprising nano-particles of graphite suspended in HFE-7000, a nano-fluid comprising nano-particles of silicon (Si) suspended in HFE-7000, a nano-fluid comprising nano-particles of aluminium nitride (AlN) suspended in HFE-7000, a nano-fluid comprising nano-particles of silicon carbide (SiC) suspended in HFE-7000, a nano-fluid comprising nano-particles of aluminium oxide (Al.sub.2O.sub.3) suspended in HFE-7000, a nano-fluid comprising nano-particles of titanium dioxide (TlO.sub.2) suspended in HFE-7000, a nano-fluid comprising nano-particles of silicon dioxide (SiO.sub.2) suspended in HFE-7000, and a nano-fluid comprising nano-particles of copper (II) oxide (CuO) suspended in HFE-7000.

[0061] The nano-particles of the twelve working nano-fluids having dimensions of approximately 45 nm and volumetric concentrations within the working nano-fluids of 4%.

[0062] The system passes the working fluids through a solar thermal panel, upon which radiation of intensity 800 W/m.sup.2 is incident. The working fluids are then passed through positive displacement expander where mechanical work is extracted from the working fluid. The working fluid then passes through a heat exchanger to a reservoir from which it is pumped back through the solar thermal panel. The pressure ratio of the system is 5:1.

[0063] In a preferred example embodiment of the invention the working fluid comprises 94% by volume HFE-7000, 6% by volume nano-particles of titanium dioxide (TiO.sub.2) with dimensions greater than 40 nm and less than 50 nm.

[0064] Referring to FIG. 4, tests were carried out in sealed glass containers, heated by part immersion in water. The water was initially checked to establish base visual and clarity. Water was heated to a maximum temperature of 90° C. and cooled using aluminium heat sinks (not shown). All temperatures were measured using thermo-couples with read-outs obtained automatically and displayed as outputs on a display (not shown). Initially all cooling was performed using a 1 mm thick aluminium heat sink (not shown). Subsequently cooling was carried out in free air, at ambient temperature without a heat sink.

[0065] The nano-particle mixture consisted of 6% (by volume) of copper oxide (CuO) nano particles in 94% (by volume) HFE-7000. The heating cycle, from room temperature to 90° C., was 20% faster than with water without the copper oxide nano particles. Identical cooling times showed the nano-particle mixture cooled 8.5% quicker than ?.

[0066] The nano-particle mixture consisting of 6% (by volume) of copper oxide (CuO) was then mixed with HFE 7100 which has a boiling point of 61° C. Similar maximum temperatures were attained in a shorter time.

[0067] Additionally, because of the molecular structure of HFE 7100 it also exhibited modest lubricant qualities and no corrosive activity was visible from any of the moving parts of pumps and expanders (not shown).

[0068] A further trial was performed used titanium oxide (TiO.sub.2) at a concentration of 8% by volume. The mixture required little agitation to remain in suspension. When heated as a mixed, in the same volume of waters used for CuO, the titanium oxide (TiO.sub.2) nano-fluid attained slighter higher temperature (boiled at 92° C.), and cooled over the same cooling period but at a slightly lower cooling rate. The titanium oxide mixture also remained in suspension for a longer time and needed less agitation than the nano-particle mixture consisting of 6% (by volume) of copper.

[0069] A further test was carried out using silicon oxide (SiO.sub.2) nano-particles with identical ratio mix to the copper oxide nano-particle mixture. However, initial heat absorption was slower with the silicon oxide nano-particles. After around 4.5 minutes the temperature of the nano fluid with the silicon oxide nano-particles heated significantly faster than the CuO nano fluid. There was very little nano particle settlement throughout the heating and cooling cycle and almost no settling after several hours.

CONCLUSIONS

[0070] All the samples used displayed improved heat transfer properties, thus efficiency; used within systems employing fluid as the heat transfer medium, is enhanced proportionally.

[0071] From the above titanium oxide and silicon dioxide appear to offer good heat transfer properties and showed good heat retention and heat release properties. They also tended to remain in suspension and showed little signs of settlement. This is considered to offer a benefit during maintenance.

[0072] Silicon dioxide shows the best overall potential for a wide range of applications, of the nano-particles tested.

Results

[0073] Quoted figures are degrees Celsius and are achieved using free air cooling over the same time interval. Table 2 shows results of preliminary trials using mixtures of HFE with copper oxide and silicon dioxide.

TABLE-US-00001 TABLE 2 Nano particle Fluid Max temp Cooled temp CuO water 91 40 CuO HFE 90 40 7100 TiO.sub.2 HFE 92 44 SiO.sub.2 HFE 87 45

[0074] Referring briefly to FIG. 3 which illustrates key steps in the manufacture of a working fluid with different nano-particles. FIG. 4 is a basic functional diagram of a production plant for manufacturing working fluid with different types of nano-particles that can be added and mixed in different ratios to the HFE liquid and shows in diagrammatical form key stages in production. Input hoppers A, B, C and D have different nano-particles and valves (not shown) deliver predefined volumes of each nano-particle into a main hopper for mixing with a base fluid into a colloidal suspension.

[0075] It is apparent that the invention may be included in heat transfer systems for use for example in buildings and/or vehicles in which heat needs to be transferred to cooler zones or from hotter zones. Examples of systems include: air-condoning units, combined heat and power units and blowers, for example for warming cabs in vehicles or rooms. The improved heat transfer efficiency of the working fluid enables heat energy to be transferred more efficiently (quicker and with less pumping power) than was previously the case and so provides for lighter and more compact heat transfer systems.

[0076] The invention has been described by way of example only and it will be appreciated that variation may be made to the embodiments described above without departing from the scope of the claims.