Oxygen bomb calorimeter use skills - the importance of water
In the calorific value measurement, the determination of heat is achieved by measuring the temperature change of the heat transfer medium. Generally speaking, water, air and metal can be used as the heat transfer medium. Water is the most commonly used one, and its heat conduction. The coefficient is about 0.5W/mK, the specific heat capacity is about 4.18KJ/Kg. °C, the water has good fluidity, and has a fast thermal conductivity and a good ability to maintain temperature. Therefore, in the calorimeter design, The inner and outer cylinders are usually filled with water. Air has a small specific heat capacity (1kJ/kg.°C) and a low thermal conductivity (0.023W/(m·k)), so it is generally used as a thermal insulation spacer. The metal has the fastest thermal conductivity (thermal conductivity). The rate is 17-90 W/(m·k)), which is a good conductor of heat. The uniformity of temperature is also good, only because of the low heat capacity value (0.4-0.8kJ/kg. °C), heat absorption and heat preservation. The ability is slightly worse, but the response to temperature is very strong, so the oxygen bombs are made of some heat-conducting, pressure-resistant, corrosion-resistant metal, and even some calorimeters use this feature to pass the built-in temperature of the inner wall of the oxygen bomb. The sensor directly measures the temperature rise of the oxygen bomb, such as IKA's C7000.
When the oxygen bomb calorimeter is used, the sample is filled in the crucible, placed in the oxygen bomb, oxygenated and ignited and burned. The oxygen bomb is completely submerged in the water, and the heat released by the sample is transferred to the water through the oxygen bomb, and finally The temperature balance is reached in the barrel. In order to place the influence of the external temperature field on the calorimetric system, a layer of water-filled insulation layer is added outside the inner cylinder, so that we need to use a large amount of water in the calorific value measurement or the calorific value measurement process. In a more automated calorimeter, the water is usually connected to a constant temperature cooler to control the temperature of the overall system, including: providing a stable temperature ignition temperature; quickly taking away the heat generated during the experiment to avoid the impact Next experiment, etc.
The water in the calorimeter needs to be replaced regularly. When you operate the oxygen bomb, you may wipe the hand with a towel or clean the oxygen bomb. It is also easy to bring some dust and fiber into the circulating water. It will be easy to block the tube after a long time. Road, the most typical fault is that the water filling time is too long, or the drainage is not clean, which will greatly increase the load on the drain pump or the suction pump, or the pump is completely blocked, so the pump has to be replaced.
In addition, if the water is not replaced for a long time, it is easy to breed algae. We recommend replacing the water in the calorimeter every 3-6 months. The frequency of replacement is just the same as the frequency of calibration. We provide special protective liquid for each use. Adding in a ratio of 1ml/1L can prevent the growth of algae and increase the conductivity of water, because the amount of water in the automatic calorimeter and the heating of the medium need to maintain a certain conductivity.
Therefore, maintaining good usage habits and periodically replacing the circulating water of the calorimeter can not only reduce the failure rate during work, but also prolong the service life of the instrument.
As shown in the figure below, a C2000 user forgot to replace the circulating water for a long time, causing blockage of the pipeline.
About IKA® ( )
IKA Group is the market leader in pre-laboratory, calorimetric analysis, mixed dispersion industrial technology. Magnetic stirrers, overhead stirrers, dispersion homogenizers, mixers, constant temperature shakers, grinders, rotary evaporators, Heating plates, constant temperature circulation systems, calorimeters, laboratory reactors and other related products constitute the product line of IKA laboratory analysis, while industrial technology mainly includes mixing equipment for scale production, dispersion emulsification equipment, kneading equipment, and Try to expand the production of the complete solution. The group is headquartered in Staufen, southern Germany, with branches in the United States, China, India, Malaysia, Japan, South Korea, Brazil and other countries.
Founded in 1910, IKA is now proud to review the history of the past 100 years.
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