Calorimeters with Heat Exchange between the Sample and Surroundings

Calorimeters with Heat Exchange between the Sample and Surroundings... 

Calorimeters with Heat Exchange between the Sample and Surroundings 1175 Here is a summary of the difficulties encountered in flow calorimeters ... 

The construction principles of such chip calorimeters are similar to those of conventional calorimeters The heater corresponds to the furnace, and the center of the membrane corresponds to the calorimeter system, including the sample container. The thin membrane serves as the thermal path between the heater and the sample with very low thermal resistance and very low effective heat capacity. The thermopile measures the temperature difference between the sample site and the chip frame (surroundings). Because of the much larger lateral dimension of the membrane of at least two orders of magnitude, the heat exchange between the sample and the frame can be neglected. The chip calorimeter can therefore be considered a quasi-adiabatic calorimeter when vacuum is applied. 

These are still diathermal calorimeters, where everything happens as if there was excellent heat exchange between the system S and the surrounding thermostat T. This means that the system temperature Ts closely follows that of the thermostat, Tj. The good heat exchange is, in reality, simulated . For that purpose, the thermal transfer between sample and thermostat is complemented or replaced by a physical phenomenon taking place in close contact with die sample and able to generate or remove heat in situ. 

It follows from these considerations that in calorimeters with large thermal resistance between sample vessel and surroundings, the measured temperature signal is proportional to the heat exchanged with the calorimeter substance. In... 

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