GB2121172A - Bomb calorimeter - Google Patents

Abstract

In a bomb calorimeter, the chamber and/or the bomb in which a substance under test is subjected to combustion may have an excess of material 4, 6 which is at least partially removable e.g. by turning, milling or drilling, so that the mass of the chamber or of the bomb can be adjusted to an accurate value. This then makes it possible to interchange chambers and bombs which have not been calibrated together. <IMAGE>

Description

SPECIFICATION Bomb calorimeter The invention relates to a bomb calorimeter for determining the calorific value of solid or liquid substances, more particularly fuels.

Bomb calorimeters are known which comprise a bomb which contains the substance to be tested and has an ignition device, and a chamber which contains the bomb and is filled with water during the measuring operation and is preferably surrounded, in turn, by an isothermal or adiabatic water jacket.

The calorific value is determined by measuring any increase in temperature in the water of the chamber. Therefore, the temperature of the water in the chamber must be measured very carefully so as not to exceed the required error tolerance, which may be only 0.1%, for example. Since the error in weighing the water and the error in measuring the temperature cannot be made as small as one would like, when calibrating the calorimeter system particular emphasis must be placed on precisely determining the heat capacity of this system. The dominant factors are the heat capacity of the water-filled chamber and of the bomb.

Frequently, it is desirable to be able to use a plurality of bombs and hitherto each bomb has had to be calibrated into the calorimeter system in question from scratch. The different heat capacities resulting are then taken into account in the calculations. The same applies when a more than one chamber is used.

Further, when bombs are used in chambers for which they were not calibrated, recalibration is required at every experiment. Bombs can be made with optical markings which may be scanned electro-optically to ensure association of the correct bomb with the correct chamber, but such markings can be complicated and the scanning techniques necessary to ensure correct matching can be expensive.

Thus, it has been found that when a plurality of calorimeter systems, bombs and inner chambers are used, not only is the calibration extremely complex but also the operator has to exercise extreme care.

The aim of the invention is therefore to make it possible to use any desired combinations of bombs and chambers without reducing the required accuracy of measurement, without the need for fresh calibration each time and without the need to provide optical markings on the bombs which are scanned by means of electronic optical means so that the right bomb can be associated with the right chamber. A plurality of chambers and bombs should be compatible with one another and interchangeable.

According to the invention, therefore, we provide a bomb calorimeter comprising a bomb having an ignition device, and a chamber which contains the bomb, wherein the bomb and/or the chamber has excess material which is at least partially removable.

The removal of the excess material of the bomb and/or-the chamber is a way of accurately adjusting their heat capacities. Since the heat capacity is dependent on the mass of the bomb or chamber, by accurately adjusting the mass, the heat capacity may be adjusted to within fine error limits.

Since the water for the chamber can be weighed to within 0.1 g and the heat capacity of the chamber is obtained by adding the heat capacity of the empty chamber and that of the water put in, it is now possible according to the invention subsequently to bring the mass of the empty chamber to a desired value, extremely precisely and accurately, in spite of manufacturing tolerances or the like, by partially removing the excess material provided on the bomb or chamber according to the invention until the desired mass is attained. The same procedure may be followed with the bomb.

Thus, a bomb calorimeter may be obtained wherein all the chambers and bombs are interchangeable since they all have the same heat capacity. Similarly, complicated markings and matching of bombs with specific inner chambers using optical scanning means, which may be expensive, are avoided, as is the need for repeated re-calibration.

A preferred embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a longitudinal section through a chamber of a bomb calorimeter in accordance with the invention; and Fig. 2 is a side view of a bomb calorimeter in accordance with the invention.

A bomb calorimeter (not shown in detail) comprises, in known manner, a chamber 1 in which the bomb 2 can be set up. In addition, temperature measuring means and stirrers or the like may engage in this chamber 1. The space between the wall of the chamber 1 and the bomb 2 is filled with an accurately metered quantity of water.

In order to obtain a precise heat capacity both for the bomb and for the chamber, so that a plurality of chambers 1 and bombs 2 can be used together or interchanged without affecting the overall heat capacity of the system, in this embodiment an excess of material which is at least partially removable is provided both on the bomb 2 and also on the chamber 1 in a manner which will be described hereinafter.

In Fig. 1, the chamber 1 contains a bomb support 3 for positioning the bomb 2 and this bomb support 3 comprises the excess material of the chamber 1.

The excess material of the bomb 2 is preferably provided on the bottom 4 of the bomb.

In both cases, the excess material may be removed at least partially by shaping by machining, and in particular by turning, milling or optionally by drilling. It is readily apparent that the bottom 4 of the bomb 2, for example, can be trued by a small amount without any major problems.

The bomb support 3 is conveniently fixedly mounted in the chamber 1 and its mass can be reduced by drilling its bottom 5 and/or by removing its rim 6. In the bottom 5 of the bomb support 3 there is an opening 7 which may be enlarged, for example, to give the desired balance of weight. On the rim 6, teeth or recesses 8 may be formed or the entire rim 6 may simply be shortened. The fixed mounting of the bomb base 3 in the chamber 1 has the major advantage that it ensures that the right bomb support is always associated with the right chamber and it is impossible for confusion to occur or even for a matching bomb support 3 to be lost.

The bottom 4 of the bomb 2 is thick enough for a machining tool, more particularly a turning tool, to be applied thereto. However, it is also possible for the base to have at least one projecting portion, e.g. a projecting rim or the like, on which the machining tool can be placed.

It should also be mentioned that the possible points of attack for a machining tool, more particularly for a drill or the like which is to be placed against the bomb base, may be predetermined or already marked, for example punch-marked. In this way, the manufacturing process makes it easier to obtain the desired balance of weight.

It will be appreciated that the features and details of construction, for example excess material on the bomb and excess material on the chamber, need not be present together in the same embodiment, but may be present independently or together, or in any combination as desired.

Similarly, it will be appreciated that when reference is made herein to one bomb or one chamber the same considerations apply analogously to calorimeters having more than one bomb and/or more than one chamber.

Claims (14)

1. A bomb calorimeter comprising a bomb having an ignition device, and a chamber which contains the bomb, wherein the bomb and/or the chamber has excess material which is at least partially removable.

2. A bomb calorimeter as claimed in claim 1, wherein the excess material can be at least partially removed by machining, turning, milling or drilling.

3. A bomb calorimeter as claimed in claim 1 or claim 2, wherein the excess material of the chamber forms a support for the bomb.

4. A bomb calorimeter as claimed in claim 3, wherein the support for the bomb is fixedly mounted in the chamber and its mass can be reduced by drilling the bottom of the support and/or by at least partially removing a rim thereon.

5. A bomb calorimeter as claimed in any preceding claim, wherein the excess material of the bomb is provided on the bottom thereof.

6. A bomb calorimeter as claimed in claim 5 wherein the bottom of the bomb is of sufficient thickness to enable a machining tool to be applied thereto.

7. A bomb calorimeter as claimed in claim 5 or claim 6, wherein the bottom of the bomb has at least one projecting portion or the like, to which a machining tool can be applied.

8. A bomb calorimeter as claimed in claim 7, wherein the projecting portion is a rim.

9. A bomb calorimeter as claimed in any of claims 6 to 8 wherein the machining tool is a turning tool.

10. A bomb calorimeter as claimed in any preceding claim, wherein the excess material of the chamber is marked with predetermined possible points of attack for a machining tool.

1 A bomb calorimeter as claimed in claim 10 wherein the possible points of attack for a drill are punch-marked on the excess material of the chamber.

12. A bomb calorimeter substantially as herein described with reference to the accompanying drawings.

1 3. A method of accurately adjusting the heat capacities of component parts of a bomb calorimeter having at least one bomb ant at least one chamber which contains the bomb(s), which comprises at least partially removing excess material provided on at least one bomb and/or at least one chamber.

14. A method as claimed in Claim 13 substantially as herein described with reference to the accompanying drawings.

1 5. A method of making sets of interchangeable bombs and/or chambers for use in a bomb calorimeter which comprises accurately adjusting the heat capacity of at least one bomb and/or chamber by at least partially removing excess material therefrom.

1 6. A method as claimed in claim 1 5 substantially as herein described with reference to the accompanying drawings.