Product category:
Chemical analysis equipment
News Release from: Digital Data Systems | Subject: Cal2k, Eco and e2K
Edited by the Laboratorytalk Editorial
Team on 04 July 2007
Comparison of bomb calorimetry methods
The adiabatic system, isothermal system, and the dry method (dry static jacket isothermal method) are compared and advantages and disadvantages described
In the adiabatic system the environment is controlled so that no energy is lost or gained To achieve this state, the calorimeter vessel (bomb) and bucket are surrounded by a water jacket which is strictly temperature controlled by a system of circulators, heaters and coolers, so that it has the same temperature as the inner bucket
This article was originally published on Laboratorytalk on 4 Jul 2007 at 8.00am (UK)
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The isothermal calorimeter measures the effect that the environment has on the bucket before and after the determination and corrects the result accordingly.
This implies that the environment is stable during the determination.
To achieve stability a large body of water surrounds the vessel and bucket assembly, which is thermally stable.
Further reading
Bomb calorimeter added to Cal2k range
Digital Data Systems introduces the new e2K, an inexpensive, language-compatible combustion (bomb) calorimeter, to the Cal2k system range.
Calorimeter has a 'revolutionary' vessel
The vessel is the heart of the calorimeter and features a printed circuit board containing; a microprocessor, memory, temperature sensors and other electronics, which are built into the base
Calorific analysis of fuels and oils
Calorific value (CV) of liquid fuels and oils can be determined in exactly the same way as solids, like coal, by placing the sample in a pressurised vessel, igniting, and measuring the released heat
DDS developed its first calorimeter system in 1972; this system was a full isothermal system with water jacket.
Prior to development of the CP500, it was demonstrated by Digital Data Systems that a polystyrene jacket, which has very little thermal mass and negligible heat conductivity, could replace the water jacket.
The system was referred to as the dry method.
Isoperibol (isothermal) calorimeter:.
With an isoperibol calorimeter a water jacket surrounds the bucket in which the vessel sits.
The surrounding water jacket is controlled to be at a constant temperature.
When a sample is fired, the heat from the vessel is transferred to the water in the bucket and the temperature rise of the bucket water is measured to determine the calorific value of the sample.
Dry static jacket (isothermal) calorimeter (DDS - CAL2k, ECO and e2K):.
The dry static jacket isothermal method has no water inside the calorimeter.
An aluminium sleeve that is an integral part of the vessel replaces the bucket.
The sleeve transfers the heat from the combustion process rapidly and evenly around the outside shell of the vessel.
The temperature sensors are located between the combustion vessel and the sleeve.
The temperature rise of the vessel is measured to determine the calorific value of the sample.
The surrounding water jacket is replaced by polystyrene that is insulated from the outside environment by an aluminium box.
The timing of the determination and the quality of the insulation is such that the environment has negligible effect on the determination.
The advantages to the dry static jacket isothermal method are:.
No complicated water pipes and valves.
The associated switching circuitry is not required.
This makes the unit virtually maintenance free.
The electronic control circuits are reduced thus making the unit very easy to fault find in case of failure.
With reduced electronics in the calorimeter, the training of a service technician or operator is reduced to an absolute minimum.
Precise and reproducible determination of gross calorific values according to ISO 1928, DIN51900 and BS1016:105 international standards.
By making the vessel removable and by removing the cooling of the vessel from the calorimeter, the speed of each determination is greatly increased.
Once a result is obtained for a determination, the hot vessel can be removed and cooled in a separate unit.
This allows for another vessel to be inserted into the calorimeter and another determination to be started even before the previous vessel has been cooled.
This allows for higher throughput in a single calorimeter.
The use of the dry static jacket method allows water to be removed from the vessel surrounds which in turn allows electronics to be built into the vessel.
The advantages to this are:.
The temperature measurements of the vessel are totally independent of the calorimeter and all calibration data is stored inside the vessel.
Multiple vessels can be used in a single calorimeter.
Any vessel can be used in any calorimeter without re-calibration.
If a vessel needs reconditioning or fails the calorimeter can still be used, using another vessel.
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