Test sample heating apparatus and method

A test sample heating apparatus and method includes a heating jacket that applies heat to a sample vessel containing a test sample. The heating jacket has a vessel-receiving recess that is sized and shaped to allow the sample vessel to be placed within the recess with limited annular spacing between at least part of the sample vessel exterior surface and at least part of the heating jacket recess interior surface. Proximate surfaces of at least one of the heating jacket and the sample vessel may be coated with a dark coating to enhance heat transfer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/164,161 filed on Mar. 27, 2009, which application is incorporated herein by reference as if reproduced in full below.

Not applicable.

FIELD OF THE DISCLOSURE

This invention relates generally to testing equipment used to measure properties of materials and chemical systems, and more specifically to a heating device used to heat media contained in a sample vessel during material testing.

BACKGROUND

In the oil and gas industry, it is imperative to know and understand the material properties of compositions used during drilling and exploration and to determine how these properties are affected by temperature, pressure and time. Various tests require that a material, compound or formulation, be subjected to testing at temperatures above ambient temperature.

An exemplary material test utilizes a viscometer to determine the viscosity of a fluid sample wherein a sample is rotated in relation to an immersed sensor element such as a bob. It is often desirable to conduct such measurements at above-ambient temperatures.

To do this, the sample is routinely placed in a sample cup having specified dimensions. During testing the sample is arranged within a heating unit with a bob of specified dimension located in the sample cup. Typically, an oil-based or water-based fluid is retained in the heating unit intermediate the heating unit interior surfaces and the sample vessel exterior surfaces to provide efficient heat transfer from the heating unit to the sample vessel and consequently to the sample.

The heating unit typically has an insulating chamber to limit heat dissipation to the environment.

Conventional heating units for instruments that test fluid properties typically comprise a container constructed to hold a liquid heating medium, typically an oil. Heaters are used to apply heat to the heating unit's retaining wall which is in direct contact with the heating liquid, thus increasing the liquid's temperature. The sample vessel is at least partially surrounded by the liquid inside the heating jacket. The liquid imparts heat to the sample vessel through conduction heating. In this system, the retaining surface of the heating unit is typically machined aluminum and the exterior surface of the sample vessel is a corrosion-resistant alloy.

A second conventional heating apparatus uses a machined graphite block to replace the oil. The graphite block is machined to directly contact the outer surfaces of the sample vessel. Heaters apply heat directly to the graphite block, which increases the block's temperature. An exemplary heating apparatus using graphite block is marketed by Chandler Engineering as Model No. 5550 HPHT Viscometer.

BRIEF SUMMARY OF THE DISCLOSURE

A test sample heating apparatus and method includes a heating jacket that applies heat to a sample vessel containing a test sample. The heating jacket has a vessel-receiving recess that is sized and shaped to allow the sample vessel to be placed within the recess with limited annular spacing between at least part of the sample vessel exterior surface and at least part of the heating jacket recess interior surface. Proximate surfaces of at least one of the heating jacket and the sample vessel may be coated with a dark coating to enhance heat transfer.

DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

The exemplary embodiment is best understood by referring to the drawings, like numerals being used for like and corresponding parts of the various drawings.

The directions lower and upper as used in this specification are used for descriptive purposes only and it will be understood by one having skill in the art that different orientations are possible.

Referring toFIG. 1, a cross-sectional view of a test sample heating apparatus10is shown.

An exemplary sample cup12is shown positioned in a heating unit14. More particularly, sample cup12is positioned in heating unit recess42of heating unit14.

Sample cup12comprises a generally cylindrical cup having a sample wall34and a sample cup bottom38. In the embodiment depicted, sample cup12is attached to a viscometer80by conventional attachment means. A stem valve82extends from sample cup bottom38. A viscometer bob84extends into sample cup12. Viscometer bob84is attached to viscometer80by means of bob shaft86.

Heating unit14generally comprises a heat jacket26disposed within an exterior heat shield40, an exterior base46and a lid50. Heat jacket26is attached to lid50and extends downwardly from lid50. Insulation48is provided intermediate heat jacket26and exterior heat shield40, exterior base46and lid50.

Heat jacket26is generally constructed as a hollow cylinder with an open upper end52and a closed base30. Interior wall surface28of heat jacket26is generally cylindrical from base30to upper end opening52. Interior wall surface28, base30and opening52define heating unit recess42.

Referring toFIG. 1andFIG. 2, sample cup12is shown in operational placement with sample cup12(not visible inFIG. 2) disposed within heating unit recess42of heat jacket26. Sample cup12is readily removable from heating unit14. In the embodiment depicted such removal may be accomplished by lowering heating unit14in relation to viscometer80.

Heating elements16are attached to heat jacket26. Heating elements16comprise heater bands extending around heat jacket26. Heating elements16are electrically connected to a power source (not shown). Heat regulation is provided by a controller (not shown), which may be computer-controlled.

Thermocouple24is provided for measurement of temperature interior of sample cup12. In the embodiment depicted, thermocouple24is contained within bob shaft86. Thermocouple58is provided in heat jacket26for measurement of temperature of heat jacket26.

Sample cup12wall34has an exterior surface36. Heat jacket26has an interior wall surface28. Sample cup12is closely received within heating unit recess42of heat jacket26with an annular opening44defined by sample cup exterior surface36and jacket interior wall surface28.

Heating unit recess42is sized to allow insertion and removal of sample cup12into and from heating unit recess42of heating unit14. Sample cup12and heating unit14are structured and sized to limit the lateral dimension44aof annular opening44. Lateral dimension44ais the distance between sample cup exterior surface36and jacket interior wall surface28.

In an exemplary embodiment, sample cup12and heating unit14are constructed such that annular opening lateral dimension44abetween sample cup exterior surface36and jacket interior wall surface28is in a range of 0.127 mm (0.005 inches) to 6.35 mm (0.25 inches) with sample cup12installed in heating unit recess42. Such limited annular opening enhances radiant heat transfer between sample cup exterior surface36and jacket interior wall surface28.

In an exemplary embodiment emissivity of sample cup exterior surface36is increased by applying a coating54to sample cup wall exterior surface36. In an exemplary embodiment, cup coating54is a material having an emissivity coefficient in the range of 0.6 to 1.0. A coating54having an emissivity coefficient of greater than 0.9, such as black paint, is preferred.

In an exemplary embodiment, cup coating54is a non-reflective material such as a flat paint or a matte paint.

In an exemplary embodiment emissivity of jacket interior wall surface28is increased by applying a coating56to heating unit recess42interior wall surface28. In an exemplary embodiment, coating56is a material having an emissivity coefficient in the range of 0.6 to 1.0. A coating56having an emissivity coefficient of greater than 0.9, such as black paint, is preferred. In an exemplary embodiment, coating56is a non-reflective material such as flat paint or matte paint.

In exemplary tests of test sample heating apparatus10, a sample cup12containing a sample material60comprising water was placed in a heating unit14. Sample cup coating54and heating unit coating56each comprised a low-reflectivity flat black coating. Annular opening44acomprised a measured distance of 1.27 mm (0.050 inches) in one test and 3.175 (0.125 inches) in another test. Heating elements16were activated to increase temperature of heating unit recess42interior wall surface28in a range starting at ambient temperature of 21° C. (70° F.) and extending upward to 177° C. (350° F.). Temperature readings were regularly taken at thermocouple24. Temperature readings were regularly taken at thermocouple58.

It was determined that heat transfer from heating unit14to sample cup12was adequate to provided controlled temperature within the described temperature range with acceptable time differential between the measured temperature of sample material60and heating unit recess42interior wall surface28.

It was further determined that the achievement of a desired temperature of the test sample and maintenance of a desired temperature of the test sample was enhanced in the present invention as compared to a conventional application using a fluid heating medium within heating unit recess42. An apparent reason for improved control is reduced thermal mass of the present invention in the heating unit recess42resulting from elimination of the liquid heat transfer medium. In a conventional application, the liquid medium is heated to transfer heat to the test sample within sample cup12. When a desired temperature is achieved and heating elements16are deactivated, a liquid medium continues to transfer heat to the sample cup12. The present invention does not eliminate continued heat transfer between heating unit recess42interior wall surface28and sample cup wall exterior surface36upon deactivation of heating elements16. However, the present invention, having less thermal mass and having annular opening44, responds more quickly to decrease heat transfer when heating elements16are deactivated.

In operation, the heating effect of the sample cup12by the heating jacket26is accomplished by radiant heat transfer. Heat transfer by conduction or convection is minimal.

In an application of the present invention involving a viscometer80, a sample material60is placed in sample cup12. Sample cup12is placed in heating unit recess42without insertion of a conductive liquid between sample cup wall34and heat jacket interior wall surface28. Sample cup12and heating unit14are then positioned such that viscometer bob84is positioned within sample cup12and sample cup12is attached to viscometer80. Sample cup12is then rotated with respect to heating unit14. Power is applied to resistive heating elements16with a resulting increase in temperature of heating elements16and a corresponding increase of temperature of heating jacket26. As the temperature of heating jacket26increases a temperature differential between heating jacket26and sample cup12develops. Accordingly, there is a net transfer of electromagnetic radiation to sample cup12from heating jacket26, resulting in heating of sample cup12and a resulting heating of the sample material60. The rate of heat transfer from heating jacket26to sample cup12is a function of the temperature differential, the surface areas of heating jacket26and sample cup12and the emissivity coefficients of heating jacket26and sample cup12or, if a coating54or coating56is used, the emissivity coefficients of the coating54and the coating56. The temperature of the sample24is monitored by thermocouple24with such temperature controlled by controlling the temperature of heating jacket26. Viscometer80may be used to determine material sample60properties at the various temperatures generated. In an exemplary embodiment, heat jacket26comprises aluminum and heating unit recess42interior wall surface28heat jacket coating56comprises black paint having a flat finish.

In an exemplary embodiment, sample cup coating54of sample cup12exterior surface36comprises black paint having a flat finish.

In an exemplary embodiment, sample cup12comprises a corrosion-resistant alloy.

In an exemplary embodiment, sample cup12may be utilized without a coating54or heat jacket26may be utilized without a coating56. In either such event, the teachings of the present invention apply, but with a reduction in the heat transfer rate.

In an exemplary embodiment, the finish roughness of sample cup coating54is in the range of 630 to 9,842.5 rms microns (16 to 250 rms micro-inch) (wherein rms means root mean square).

In an exemplary embodiment, the finish roughness of heating unit coating56of interior wall surface28is in the range of 630 to 9,842.5 rms microns (16 to 250 rms micro-inch) (16 to 250 rms micro-inch).

In an alternative embodiment, heat jacket interior wall surface28may be anodized with a black dye applied.

In an alternative embodiment, sample cup coating54may comprise a relatively dark, non-reflective coating. In an alternative embodiment, heat jacket interior surface28coating56may comprise a relatively dark, non-reflective coating.

In an alternative embodiment, sample cup coating54and heat jacket26may be other than a flat finish.

In an alternative embodiment, sample cup coating54may comprise a coating having a friction coefficient in the range of 0.2 to 0.0 to allow for lesser dimension of annular opening44while allowing ready insertion and removal of sample cup12into and from heating unit recess42of heating unit14. An exemplary coating material comprises polytetrafluoroethylene.

In an alternative embodiment, heating unit coating56may comprise a coating having a friction coefficient in the range of 0.2 to 0.0 to allow for lesser dimension of annular opening44while allowing ready insertion and removal of sample cup12into and from heating unit recess42of heating unit14. An exemplary coating material comprises polytetrafluoroethylene.

Various embodiments will be understood from the foregoing description, and it will be apparent that, although embodiments have been described in detail, various changes, substitutions, and alterations may be made in the manner, procedure and/or details thereof without departing from the spirit and scope or sacrificing any of its material advantages, the forms hereinbefore described being merely exemplary embodiments thereof.